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Before yesterdayMatteo Malvica

Custom base64 alphabet encoder/decoder

21 January 2019 at 00:00
As I am spending slices of my time refreshing some Malware Analysis theory, I thought was valuable (at least to my future amnesiac self) writing down a simple β€˜custom base64 alphabet translator.’ This can/should be extended to support CLI/WebApp i ntegration. So, here is the skeleton: UPDATE: added interactive mode below and also found this great tool which is already doing what I aimed for and much more. import string import base64 # custom encoding function def EncodeCustomBase64(stringToBeEncoded,custom_b64): standard_b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=' encoded = base64.

Detecting VMware on 64-bit systems

5 December 2018 at 00:00
Hot on the heels of the latest post, I have decided to port to linux another lab example from Intermediate x86 class. This time I will talk about the RedPill paper by Joanna Rutkowska. This test is expected to work on single-core CPUs only The main purpose of this test code is to call the SIDT instruction and save its return value inside an array: this value will tell us whether we are running it inside a vm or not.

Revealing software-breakpoints from memory (linux)

2 December 2018 at 00:00
I was about to finish the Intermediate x86 class from OpenSecTraining, when I thought was worthwhile porting to Linux this interesting exercise about software breakpoints. Whenever we send a software breakpoint on GDB or any other debugger, the debugger swaps the first instruction byte with the double C (0xCC) instruction and keeps track of each and every breakpoint/replaced-instruction via the breakpoint table and thus, leaving the code section of the executable altered.

Windows XP Kernel Debugging on VMware fusion

16 November 2018 at 00:00
Something that once was done with heavy and expensive serial cables, can now be achieved in a matter of seconds through virtual machines. I am of course speaking about kernel debugging, what else? Recently I have been following the exceptionally great Intermediate x86 training lead by Xeno Kovah where, in order to keep up with the labs, I had to setup a WinXP-to-WinXP kernel debugging setup. So after a few moments of bewilderment I reached a full working environment with the following steps.

SLAE32 - Assignment 7 - Custom Crypter

10 October 2017 at 00:00
As as a seventh and last assignment of the 32-bit Securitytube Linux Assembly Expert, I have been tasked to create a custom shellcode crypter. The idea behind a crypter, is to encode the shellcode beforehand and decode it at runtime. This process will make the shellcode looks like random values, and thus aiming to bypass AV and IDS detection. When it comes to cryptography, it is a well-known wise approach to not try to reinvent the wheel and instead use what is available and well tested: this is done to prevent any new weakness or bug to be introduced in a a freshly written crypto-algorithm.

SLAE32 - Assignment 6 - Polymorphic Shellcodes

6 October 2017 at 00:00
As a sixth assignment of the 32-bit Securitytube Linux Assembly Expert, I had to create three different polymorphic version of shellcodes taken from ShellStorm. Here is my selection: Linux x86 execve(β€œ/bin/sh”) - 28 bytes. Linux x86 iptables flush - 43 bytes. Linux x86 ASLR deactivation - 83 bytes. Polymorphism means that we can mutate shellcode, so while keeping the same functionality the signature is different.