Theodosius (Theo for short) is a jit linker created for obfuscation. The project is extremely modular in design and supports both kernel and usermode projects. Theo works with static libraries rather than completely compiled binaries. This allows it to easily position, obfuscate, and scatter symbols anywhere as the project takes the place of the linker.
Doxygen for this project can be found here
- Theodosius - Jit linker, Mapper, Mutator, and Obfuscator
- RIP Relative Addressing
- License - BSD 3-Clause
- BTBD - Huge thanks for providing suggestions and bouncing ideas back and forth.
- SMAP - scatter mapper, this project is heavily influenced by SMAP.
- XED
- spdlog
- linux-pe
- cmkr
Download and install cmake on your system, then execute the following command in the root dir of this project:
cmake -B build
Then navigate into dependencies/xed/ and run python3 mfile.py. Building XED can be tricky on windows, I suggest you use the visual studios console since it has env vars to everything needed to build XED. linux seems to build it just fine...
A linker is a program which takes object files produces by a compiler and generates a final executable native to the operating system. A linker interfaces with not only object files but also static libraries, "lib" files. What is a "lib" file? Well a lib file is just an archive of obj's. You can invision it as a zip/rar without any compression, just concatination of said object files.
Theo is a jit linker, which means it will link objs together and map them into memory all at once. For usability however, instead of handling object files, Theo can parse entire lib files and extract the objects out of the lib.
If you define a c++ file called "main.cpp" the compiler will generate an object file by the name of "main.obj". When you refer to data or code defined in another c/c++ file, the linker uses a symbol table to resolve the address of said code/data. In this situation I am the linker and I resolve all of your symbols :).
Static linking is when the linker links entire routines not created by you, into your code. Say memcpy (if its not inlined), will be staticlly linked with the CRT. Static linking also allows for your code to be more independant as all the code you need you bring with you. However, with Theo, you cannot link static libraries which are not compiled with mcmodel=large. Theo supports actual static linking, in other words, using multiple static libraries at the same time.
Dynamic linking is when external symbols are resolved at runtime. This is done by imports and exports in DLL's (dynamiclly linked libraries). Theo supports "dynamic linking", or in better terms, linking against exported routines. You can see examples of this inside of both usermode and kernelmode examples.
For integration with visual studios please open install llvm2019 extension, or llvm2017 extension. Once installed, create or open a visual studio project which you want to use with LLVM-Obfuscator and Theo. Open Properties --> Configuration Properties ---> General, then set Platform Toolset to LLVM.
Once LLVM is selected, under the LLVM tab change the clang-cl location to the place where you extracted clang-cl.rar. Finally under Additional Compiler Options (same LLVM tab), set the following: -Xclang -std=c++1z -Xclang -mcode-model -Xclang large -Xclang -fno-jump-tables -mllvm -split -mllvm -split_num=4 -mllvm -sub_loop=4.
Please refer to the LLVM-Obfuscator Wiki for more information on commandline arguments.
- No SEH support, do not add
__try/__exceptin your code. - No CFG (control flow guard) support. Please disable this in C/C++ ---> Code Generation ---> Control Flow Guard
- No Stack Security Check Support. Please disablel this in C/C++ ---> Code Generation ---> Security Check (/GS-)
- Your project must be set to produce a .lib file.
- Your project must not link with other static libraries which are not compiled with
-Xclang -mcmodel-large. - Project must be compiled with the following flags
-Xclang -mcmodel=large, removes RIP relative addressing besides JCC's.-Xclang -fno-jump-tables, removes jump tables created by switch cases./Zc:threadSafeInit-, static will not use TLS (thread local storage).
In order to allow for a routine to be scattered throughout a 64bit address space, RIP relative addressing must not be used. In order to facilitate this, a very special version
of clang-cl is used which can use mcmodel=large. This will generate instructions which do not use RIP relative addressing when referencing symbols outside of the routine in which the
instruction itself resides. The only exception to this is JCC instructions, (besides call) also known as branching instructions. Take this c++ code for an example:
ObfuscateRoutine
extern "C" int ModuleEntry()
{
MessageBoxA(0, "Demo", "Hello From Obfuscated Routine!", 0);
UsermodeMutateDemo();
UsermodeNoObfuscation();
}This c++ function, compiled by clang-cl with mcmodel=large, will generate a routine with the following instructions:
0x00: ; void UsermodeNoObfuscation(void)
0x00: public ?UsermodeNoObfuscation@@YAXXZ
0x00: ?UsermodeNoObfuscation@@YAXXZ proc near ; CODE XREF: ModuleEntry+42↓p
0x00: var_4 = dword ptr -4
0x00: 48 83 EC 28 sub rsp, 28h
0x04: C7 44 24 24 00 00 00 00 mov [rsp+28h+var_4], 0
0x0C: loc_C:
0x0C: 83 7C 24 24 05 cmp [rsp+28h+var_4], 5
0x11: 0F 83 38 00 00 00 jnb loc_4F
0x17: 31 C0 xor eax, eax
0x19: 48 BA 28 01 00 00 00 00 00 00 mov rdx, offset ??_C@_04DKDMNOEB@Demo?$AA@ ; "Demo"
0x23: 49 B8 00 01 00 00 00 00 00 00 mov r8, offset ??_C@_0CD@JEJKPGNA@Hello?5... ; "Hello From Non-Obfuscated Routine!"
0x2D: 48 B8 A0 01 00 00 00 00 00 00 mov rax, offset MessageBoxA
0x37: 45 31 C9 xor r9d, r9d ; uType
0x3A: 44 89 C9 mov ecx, r9d ; hWnd
0x3D: FF D0 call rax ; MessageBoxA
0x3F: 8B 44 24 24 mov eax, [rsp+28h+var_4]
0x43: 83 C0 01 add eax, 1
0x46: 89 44 24 24 mov [rsp+28h+var_4], eax
0x4A: E9 BD FF FF FF jmp loc_C
0x4F: loc_4F:
0x4F: 48 83 C4 28 add rsp, 28h
0x53: C3 retn
0x53: ?UsermodeNoObfuscation@@YAXXZ endp
As you can see from the code above, (sorry for the terrible syntax highlighting), references to strings and calls to functions are done by first loading the address of the symbol into a register and then interfacing with the symbol.
0x2D: 48 B8 A0 01 00 00 00 00 00 00 mov rax, offset MessageBoxA
; ...
0x3D: FF D0 call rax ; MessageBoxA
Each of these instructions can be anywhere in virtual memory and it would not effect code execution one bit.
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