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https://github.com/cinit/LibcoreSyscall
A library for making Linux syscalls on Android written in pure Java.
https://github.com/cinit/LibcoreSyscall
android android-library java libart libcore linux-syscall syscall
Last synced: about 2 months ago
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A library for making Linux syscalls on Android written in pure Java.
- Host: GitHub
- URL: https://github.com/cinit/LibcoreSyscall
- Owner: cinit
- License: apache-2.0
- Created: 2024-10-29T13:50:33.000Z (2 months ago)
- Default Branch: main
- Last Pushed: 2024-10-30T13:19:43.000Z (2 months ago)
- Last Synced: 2024-10-30T14:29:49.094Z (2 months ago)
- Topics: android, android-library, java, libart, libcore, linux-syscall, syscall
- Language: Java
- Homepage:
- Size: 116 KB
- Stars: 30
- Watchers: 2
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Libcore-Syscall
Libcore-Syscall is a Java library for Android that allows you to make any Linux system calls directly from Java code.
## Features
- Support Android 5.0 - 15
- Support any system calls (as long as they are permitted by the seccomp filter)
- Implemented in 100% pure Java 1.8
- No shared libraries (lib*.so) are shipped with the library
- No `System.loadLibrary` or `System.load` is used
- Small, no dependencies
## Usage
The library provides the following classes:
- MemoryAccess/MemoryAllocator: Allocate and read/write native memory.
- NativeAccess: Register JNI methods, or call native functions (such as `dlopen`, `dlsym`, etc.) directly.
- Syscall: Make any Linux system calls.
## Example
Here is an example of how to use the library. It calls the `uname` system call to get the system information.
See [TestMainActivity.java](demo-app/src/main/java/com/example/test/app/TestMainActivity.java) for the complete example.
```java
import dev.tmpfs.libcoresyscall.core.IAllocatedMemory;
import dev.tmpfs.libcoresyscall.core.MemoryAccess;
import dev.tmpfs.libcoresyscall.core.MemoryAllocator;
import dev.tmpfs.libcoresyscall.core.NativeHelper;
import dev.tmpfs.libcoresyscall.core.Syscall;
public String unameDemo() {
StringBuilder sb = new StringBuilder();
int __NR_uname;
switch (NativeHelper.getCurrentRuntimeIsa()) {
case NativeHelper.ISA_X86_64:
__NR_uname = 63;
break;
case NativeHelper.ISA_ARM64:
__NR_uname = 160;
break;
// add other architectures here ...
}
// The struct of utsname can be found in in the NDK.
// ...
int releaseOffset = 65 * 2;
// ...
int utsSize = 65 * 6;
try (IAllocatedMemory uts = MemoryAllocator.allocate(utsSize, true)) {
long utsAddress = uts.getAddress();
Syscall.syscall(__NR_uname, utsAddress);
// ...
sb.append("release = ").append(MemoryAccess.peekCString(utsAddress + releaseOffset));
// ...
sb.append("\n");
} catch (ErrnoException e) {
sb.append("ErrnoException: ").append(e.getMessage());
}
return sb.toString();
}
```
## The Tricks
- The Android-specific `libcore.io.Memory` and the evil `sun.misc.Unsafe` are used to access the native memory.
- Anonymous executable pages are allocated using the `android.system.Os.mmap` method.
- Native methods are registered with direct access to the `art::ArtMethod::entry_point_from_jni_` field.
## Notice
- This library is not intended to be used in production code. You use it once and it may crash everywhere. It is only for a Proof of Concept.
- This library can only work on ART, not on OpenJDK HotSpot / OpenJ9 / GraalVM.
- The `execmem` SELinux permission is required to allocate anonymous executable memory. Fortunately, this permission is granted to all app domain processes.
- The `system_server` does not have the `execmem` permission. However, this is not true if you have a system-wide Xposed framework installed.
## Build
To build the library:
```shell
./gradlew :core-syscall:assembleDebug
```
To build the demo app:
```shell
./gradlew :demo-app:assembleDebug
```
## The Future
- A symbol resolver that can resolve symbols in loaded native libraries.
- Loading arbitrary shared libraries (lib*.so) with 100% pure Java code in memory without writing it to the disk.
## Credits
- [pine](https://github.com/canyie/pine)
## License
The library is licensed under the [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0).