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# qbdi-based binary-only instrumentation for afl-fuzz
NOTE: this code is outdated and first would need to be adapted to the current
AFL++ versions.
Try FRIDA mode or fpicker [https://github.com/ttdennis/fpicker/](https://github.com/ttdennis/fpicker/) first, maybe they suite your need.
## 1) Introduction
The code in ./qbdi_mode allows you to build a standalone feature that
using the QBDI framework to fuzz android native library.
## 2) Build
First download the Android NDK
```
https://developer.android.com/ndk/downloads
https://dl.google.com/android/repository/android-ndk-r20-linux-x86_64.zip
```
Then unzip it and build the standalone-toolchain
For x86_64 standalone-toolchain
```
unzip android-ndk-r20-linux-x86_64.zip
cd android-ndk-r20/
./build/tools/make_standalone_toolchain.py --arch x86_64 --api 21 --install-dir ../android-standalone-toolchain-x86_64
```
For x86 standalone-toolchain
```
./build/tools/make_standalone_toolchain.py --arch x86 --api 21 --install-dir ../android-standalone-toolchain-x86
```
In alternative you can also use the pre-built toolchain, in that case make sure
to set the proper CC and CXX environment variables because there are many
different compilers for each API version in the pre-built toolchain.
For example:
```
export STANDALONE_TOOLCHAIN_PATH=~/Android/Sdk/ndk/20.1.5948944/toolchains/llvm/prebuilt/linux-x86_64/
export CC=x86_64-linux-android21-clang
export CXX=x86_64-linux-android21-clang++
```
Then download the QBDI SDK from website
```
https://qbdi.quarkslab.com/
```
For Android x86_64
```
https://github.com/QBDI/QBDI/releases/download/v0.7.0/QBDI-0.7.0-android-X86_64.tar.gz
```
Then decompress the sdk
```
mkdir android-qbdi-sdk-x86_64
cp QBDI-0.7.0-android-X86_64.tar.gz android-qbdi-sdk-x86_64/
cd android-qbdi-sdk-x86_64/
tar xvf QBDI-0.7.0-android-X86_64.tar.gz
```
Now set the `STANDALONE_TOOLCHAIN_PATH` to the path of standalone-toolchain
```
export STANDALONE_TOOLCHAIN_PATH=/home/hac425/workspace/android-standalone-toolchain-x86_64
```
set the `QBDI_SDK_PATH` to the path of QBDI SDK
```
export QBDI_SDK_PATH=/home/hac425/workspace/AFLplusplus/qbdi_mode/android-qbdi-sdk-x86_64/
```
Then run the build.sh
```
./build.sh x86_64
```
this could build the afl-fuzz and also the qbdi template for android x86_64
### Example
The demo-so.c is an vulnerable library, it has a function for test
```c
int target_func(char *buf, int size) {
printf("buffer:%p, size:%p\n", buf, size);
switch (buf[0]) {
case 1:
puts("222");
if (buf[1] == '\x44') {
puts("null ptr deference");
*(char *)(0) = 1;
}
break;
case 0xff:
if (buf[2] == '\xff') {
if (buf[1] == '\x44') {
puts("crash....");
*(char *)(0xdeadbeef) = 1;
}
}
break;
default: puts("default action"); break;
}
return 1;
}
```
This could be built to `libdemo.so`.
Then load the library in template.cpp and find the `target` function address:
```c
void *handle = dlopen(lib_path, RTLD_LAZY);
..........................................
..........................................
..........................................
p_target_func = (target_func)dlsym(handle, "target_func");
```
Then read the data from file and call the function in `fuzz_func`:
```c
QBDI_NOINLINE int fuzz_func() {
if (afl_setup()) { afl_forkserver(); }
/* Read the input from file */
unsigned long len = 0;
char * data = read_file(input_pathname, &len);
/* Call the target function with the input data */
p_target_func(data, len);
return 1;
}
```
Just compile it
```
./build.sh x86_64
```
Then push the `afl-fuzz`, `loader`, `libdemo.so`, the `libQBDI.so` from the QBDI SDK and the `libc++_shared.so` from android-standalone-toolchain to android device
```
adb push afl-fuzz /data/local/tmp
adb push libdemo.so /data/local/tmp
adb push loader /data/local/tmp
adb push android-qbdi-sdk-x86_64/usr/local/lib/libQBDI.so /data/local/tmp
adb push ../../android-standalone-toolchain-x86_64/sysroot/usr/lib/x86_64-linux-android/libc++_shared.so
/data/local/tmp
```
In android adb shell, run the loader to test if it runs
```
cd /data/local/tmp
export LD_LIBRARY_PATH=/data/local/tmp
mkdir in
echo 0000 > in/1
./loader libdemo.so in/1
p_target_func:0x716d96a98600
offset:0x600
offset:0x580
buffer:0x716d96609050, size:0x5
offset:0x628
offset:0x646
offset:0x64b
offset:0x65c
offset:0x6df
offset:0x590
default action
offset:0x6eb
```
Now run `afl-fuzz` to fuzz the demo library
```
./afl-fuzz -i in -o out -- ./loader /data/local/tmp/libdemo.so @@
```
|
