qbdi-based binary-only instrumentation for afl-fuzz
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 prebuilt toolchain, in that case make sure to set the proper CC and CXX env variables because there are many different compilers for each API version in the prebuilt 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
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 build to libdemo.so.
Then we should load the library in template.cpp and find the target function address.
void *handle = dlopen(lib_path, RTLD_LAZY);
..........................................
..........................................
..........................................
p_target_func = (target_func)dlsym(handle, "target_func");
then we read the data from file and call the function in fuzz_func
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 @@
