@ -31,108 +31,6 @@ Static linking is when the linker links entire routines not created by you, into
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.
# RIP Relative Addressing
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:
```cpp
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
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.
Each of these instructions can be anywhere in virtual memory and it would not effect code execution one bit. However this is not the case with routines which have conditional branches. Take the following c++ code for example.
```cpp
ObfuscateRoutine
void LoopDemo()
{
for (auto idx = 0u; idx <10;++idx)
DbgPrint("> Loop Demo: %d\n", idx);
}
```
This c++ function, compiled by clang-cl with `mcmodel=large`, will generate a routine with the following instructions:
Uh oh, `jnb loc_99`?, thats RIP relative! In order to handle branching operations, a "jump table" is generated by `obfuscation::obfuscate` explicit default constructor. Instead of branching to the RIP relative code, it will instead branch to an inline jump (`JMP [RIP+0x0]`). As demonstrated below, the branching operation is altered to branch to an asbolute jump.
The linker is able to get the address of the branching code by taking the rip relative virtual address of the branching operation, which is a signed number, and adding it to the current byte offset into the current routine, plus the size of the branching instruction. For example `LoopDemo@17` + size of the branching instruction, which is six bytes, then adding the signed relative virtual address (0x2A). The result of this simple calculation gives us `LoopDemo@65`, which is correct, the branch goes to `add rsp, 28h` in the above example.
# Usage - Using Theodosius
Theodosius uses the same class structure as HMDM does. Its a highly modular format which allows for extreme usage, supporting almost every idea one might have. In order to use Theo, you must first define three lambdas, `theo::memcpy_t` a method of copying memory, `theo::malloc_t` a method to allocate executable memory, and lastely `theo::resolve_symbol_t` a lamdba to resolve external symbols.
@ -378,6 +276,108 @@ CreateRemoteThread
);
```
# RIP Relative Addressing
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:
```cpp
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
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.
Each of these instructions can be anywhere in virtual memory and it would not effect code execution one bit. However this is not the case with routines which have conditional branches. Take the following c++ code for example.
```cpp
ObfuscateRoutine
void LoopDemo()
{
for (auto idx = 0u; idx <10;++idx)
DbgPrint("> Loop Demo: %d\n", idx);
}
```
This c++ function, compiled by clang-cl with `mcmodel=large`, will generate a routine with the following instructions:
Uh oh, `jnb loc_99`?, thats RIP relative! In order to handle branching operations, a "jump table" is generated by `obfuscation::obfuscate` explicit default constructor. Instead of branching to the RIP relative code, it will instead branch to an inline jump (`JMP [RIP+0x0]`). As demonstrated below, the branching operation is altered to branch to an asbolute jump.
The linker is able to get the address of the branching code by taking the rip relative virtual address of the branching operation, which is a signed number, and adding it to the current byte offset into the current routine, plus the size of the branching instruction. For example `LoopDemo@17` + size of the branching instruction, which is six bytes, then adding the signed relative virtual address (0x2A). The result of this simple calculation gives us `LoopDemo@65`, which is correct, the branch goes to `add rsp, 28h` in the above example.
# Obfuscation
The usage of the word obfuscation in this project is use to define any changes made to code, this includes code flow. `obfuscation::obfuscate`, a base class, which is inherited and expanded upon by `obfuscation::mutation`, obfuscates code flow by inserting `JMP [RIP+0x0]` instructions after every single instruction. This allows for a routine to be broken up into unique allocations of memory and thus provides more canvas room for creative ideas.
_xeroxz
4 years ago