add linux support (#2)

Author: StackOverflowExcept1on

.github/workflows/ci.yml

@@ -1,11 +1,32 @@
 name: CI
 on:
   push:
+    branches: [ master ]
   pull_request:
+    branches: [ master ]
   workflow_dispatch:
 
 jobs:
-  build:
+  linux-build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Build project
+        run: ./_build.sh
+
+      - name: Run project without root
+        run: ./_run.sh
+
+      - name: Run project with root
+        run: ./_run.sh -a
+
+  windows-build:
     runs-on: windows-latest
 
     steps:

Bootstrapper/CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.20)
 project(Bootstrapper)
 
-set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 add_library(${PROJECT_NAME} SHARED src/library.cpp)

Bootstrapper/build.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+set -ex
+
+mkdir -p build && cd build
+
+cmake ..
+cmake --build . --config Release

Bootstrapper/src/library.cpp

@@ -4,7 +4,7 @@
 #else
 #define EXPORT __attribute__((visibility("default")))
 #include <dlfcn.h>
-#include <cstdio>
+#include <thread>
 #endif
 
 /// This class helps to manage shared libraries
@@ -113,3 +113,32 @@ extern "C" EXPORT InitializeResult bootstrapper_load_assembly(
 
     return InitializeResult::Success;
 }
+
+#ifndef _WIN32
+std::string getEnvVar(const char *name) {
+    auto val = std::getenv(name);
+    return val == nullptr ? std::string() : std::string(val);
+}
+
+__attribute__((constructor))
+void initialize_library() {
+    auto runtime_config_path = getEnvVar("RUNTIME_CONFIG_PATH");
+    auto assembly_path = getEnvVar("ASSEMBLY_PATH");
+    auto type_name = getEnvVar("TYPE_NAME");
+    auto method_name = getEnvVar("METHOD_NAME");
+
+    if (!runtime_config_path.empty() && !assembly_path.empty() && !type_name.empty() && !method_name.empty()) {
+        std::thread thread([=] {
+            sleep(1);
+            auto ret = bootstrapper_load_assembly(
+                runtime_config_path.c_str(),
+                assembly_path.c_str(),
+                type_name.c_str(),
+                method_name.c_str()
+            );
+            printf("[+] api.inject() => %d\n", (uint32_t) ret);
+        });
+        thread.detach();
+    }
+}
+#endif

DemoApplication/build.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+set -ex
+dotnet publish -c Release -r linux-x64 -p:PublishDir="$(pwd)/dist" --self-contained

README.md

@@ -11,32 +11,36 @@ CLI tool that can replace C# methods in .NET Core applications
 
 ### Requirements
 
-- Visual Studio 2022 with installed C++ & C# build tools: https://visualstudio.microsoft.com/en/vs/
+- C++ & C#
+  - Linux: g++, .NET 8: https://dotnet.microsoft.com/en-us/download/dotnet/8.0
+  - Windows: Visual Studio 2022 with installed C++ & C# build tools: https://visualstudio.microsoft.com/en/vs/
 - Node.js: https://nodejs.org/en/download/
 - frida: https://frida.re
 
-### Installation on Windows
+### Building
 
 Open command line and run this script
 
+- `_build.sh` on Linux
+- `_build.bat` on Windows
+
 It will build
 
 - Node.js package [net-core-injector](package.json) - DLL-injector written in TypeScript
 - [Bootstrapper](Bootstrapper) - helper native library written in C++ to interact with .NET Core runtime
 - [DemoApplication](DemoApplication) - test application to demonstrate how it works
 - [RuntimePatcher](RuntimePatcher) - code that attaches to [DemoApplication](DemoApplication)
 
-```
-_build.bat
-```
-
 ### Running
 
 This script should produce output like the GIF above
 
-```
-_run.bat
-```
+- `_run.sh` on Linux
+
+  Note: If you want to attach to an existing process on Linux, this requires root privileges. In this case, use
+  `_run.sh -a` (attach).
+
+- `_run.bat` on Windows
 
 ### Internal documentation
 
@@ -50,8 +54,8 @@ I did it in [`Bootstrapper/src/library.cpp`](Bootstrapper/src/library.cpp).
 
 [`net-core-injector/src/main.ts`](src/main.ts) injects `Bootstrapper.dll` into C# process and loads custom assembly
 
-
 The following command runs `DemoApplication.exe` on another thread and injects code.
+
 ```
 start DemoApplication\dist\DemoApplication.exe
 
@@ -64,6 +68,7 @@ RuntimePatcher\dist\RuntimePatcher.dll ^
 ```
 
 Then the execution happens in this order:
+
 1. get into `DemoApplication.exe` process memory via DLL-injection of `Bootstrapper.dll`
 2. call native C++ code
    ```cpp
@@ -86,4 +91,4 @@ You can use this to mod games written in C# or to patch any software
 
 ### TODO
 
-- Linux support is incomplete due to some issues with the secondary host context in `hostfxr`
+- I don't have macOS device so it's supported for now. External contributors are welcome.

RuntimePatcher/build.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+set -ex
+dotnet publish -c Release -p:PublishDir="$(pwd)/dist"

_build.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+set -ex
+
+npm install
+
+cd Bootstrapper
+./build.sh
+cd ..
+
+cd DemoApplication
+./build.sh
+cd ..
+
+cd RuntimePatcher
+./build.sh
+cd ..

_run.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -e
+
+while getopts "a" OPTION 2> /dev/null; do
+  case ${OPTION} in
+    a)
+      DO_ATTACH="yes"
+      ;;
+    \?)
+      break
+      ;;
+  esac
+done
+
+if [ "$DO_ATTACH" == "yes" ]; then
+  set -m
+  sudo sysctl kernel.yama.ptrace_scope=0
+
+  ./DemoApplication/dist/DemoApplication &
+  npm start -- inject \
+  DemoApplication \
+  Bootstrapper/build/libBootstrapper.so \
+  RuntimePatcher/dist/RuntimePatcher.runtimeconfig.json \
+  RuntimePatcher/dist/RuntimePatcher.dll \
+  "RuntimePatcher.Main, RuntimePatcher" \
+  "InitializePatches"
+  fg %1
+else
+  LD_PRELOAD=./Bootstrapper/build/libBootstrapper.so \
+  RUNTIME_CONFIG_PATH="$(pwd)/RuntimePatcher/dist/RuntimePatcher.runtimeconfig.json" \
+  ASSEMBLY_PATH="$(pwd)/RuntimePatcher/dist/RuntimePatcher.dll" \
+  TYPE_NAME="RuntimePatcher.Main, RuntimePatcher" \
+  METHOD_NAME="InitializePatches" \
+  ./DemoApplication/dist/DemoApplication
+fi