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https://github.com/dmaivel/covirt
An x86-64 code virtualizer for VM based obfuscation
https://github.com/dmaivel/covirt
code-virtualizer compiler mba mixed-boolean-arithmetic obfuscation obfuscator reverse-engineering self-modifying-code virtual-machine virtualization virtualizer vm vmp vmprotect
Last synced: 13 days ago
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An x86-64 code virtualizer for VM based obfuscation
- Host: GitHub
- URL: https://github.com/dmaivel/covirt
- Owner: dmaivel
- License: mit
- Created: 2024-12-02T23:47:38.000Z (20 days ago)
- Default Branch: master
- Last Pushed: 2024-12-04T04:35:43.000Z (18 days ago)
- Last Synced: 2024-12-04T05:26:23.255Z (18 days ago)
- Topics: code-virtualizer, compiler, mba, mixed-boolean-arithmetic, obfuscation, obfuscator, reverse-engineering, self-modifying-code, virtual-machine, virtualization, virtualizer, vm, vmp, vmprotect
- Language: C++
- Homepage:
- Size: 382 KB
- Stars: 11
- Watchers: 2
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# covirt 
An x86-64 code virtualizer for VM based obfuscation.
## Features
- Stack-based virtual machine architecture
- MBA, self-modifying code obfuscation
- Support for both PE* and ELF binaries
- Code markers to define protected regions
*\*PE support only tested on binaries compiled via MinGW-w64*
# Getting started
## Dependencies
`CMake` will fetch all these dependencies, so installing them yourself is not necessary.
| Name | Version |
| ---- | ------- |
| [CMake](https://cmake.org/) | 3.25+ |
| [Zydis](https://github.com/zyantific/zydis) | 4.1.0+ |
| [zasm](https://github.com/zyantific/zasm) | Latest |
| [LIEF](https://github.com/lief-project/LIEF) | 0.15.1+ |
## Building
A `C++23` compatible compiler is required in order to build.
```bash
git clone https://github.com/dmaivel/covirt.git
cd covirt
mkdir build
cd build
cmake ..
cmake --build . --config Release
```
# Usage
```bash
Usage: covirt [--help] [--version] [--output OUTPUT_PATH] [--vm_code_size MAX] [--vm_stack_size SIZE] [--no_self_modifying_code] [--no_mixed_boolean_arith] [--show_dump_table] INPUT_PATH
Code virtualizer for x86-64 ELF & PE binaries
Positional arguments:
INPUT_PATH path to input binary to virtualize
Optional arguments:
-h, --help shows help message and exits
-v, --version prints version information and exits
-o, --output OUTPUT_PATH specify the output file [default: INPUT_PATH.covirt]
-vcode, --vm_code_size MAX specify the maximum allowed total lifted bytes [default: 2048]
-vstack, --vm_stack_size SIZE specify the size of the virtual stack [default: 2048]
-no_smc, --no_self_modifying_code disable smc pass
-no_mba, --no_mixed_boolean_arith disable mba pass
-d, --show_dump_table show disassembly of the vm instructions
```
## Code markers
For `covirt` to know which functions need to be virtualized, you must add the start and end markers into your source code, like so:
```c
#include "covirt_stub.h"
int my_function(...)
{
int result = 0;
__covirt_vm_start();
// ...
__covirt_vm_end();
return result;
}
```
> [!IMPORTANT]
> - Do not place `__covirt_vm_end` in unreachable locations (i.e. after a return), as it will prevent the end stub from emitting
> - `__covirt_vm_...();` stubs won't work using `MSVC` because they use inline assembly
> - `SSE4` support is required
## Demo
```c
#include
#include
int calculate(int a, int b)
{
int result = 0;
__covirt_vm_start();
for (int i = 0; i < 10; i++)
if (i > 5)
result += result + a;
else
result += (result >> 1) + b;
printf("result = %d\n", result);
__covirt_vm_end();
return result;
}
int main()
{
calculate(5, 12);
}
```
The example application above was virtualized using `covirt a.out -d`, which outputs a dump of the VM instructions following obfuscation and virtualization. The current VM implementation pushes most operands onto the stack to process them, reducing the complexity of encoding the VM instructions. For instructions that don't have a defined VM handler, they will be executed natively (`vm_exit` -> `native instruction` -> `vm_enter`). Calling functions follows the same pipeline, in which we exit, call the function, and reenter the VM. All together, the transformations make the binaries grow significantly in size:
- `a.out` as an `ELF`: 15.5 kB -> 1.0 MB
- `a.out` as a `PE`: 259.3 kB -> 1.3 MB
## Obfuscation
| Description | IDA |
|-|-----------------|
IDA decompilation of `vm_entry`, which has been obfuscated via the MBA pass only. Over 27k LOC were generated by the decompiler. | 
IDA disassembly of `vm_entry`, which has been obfuscated via the MBA & SMC passes. Decompilation doesn't work. | 
## Known issues
- **Can't call another VM protected function from within a protected region**
- Causes segfault if VM is obfuscated
- No return value if VM isn't obfuscated