Changeset View
Changeset View
Standalone View
Standalone View
doc/fuzzing.md
Fuzz-testing Bitcoin Core | Fuzz-testing Bitcoin ABC | ||||
========================== | ========================== | ||||
A special test harness `test_bitcoin_fuzzy` is provided to provide an easy | A special test harness `test_bitcoin_fuzzy` is provided to provide an easy | ||||
entry point for fuzzers and the like. In this document we'll describe how to | entry point for fuzzers and the like. In this document we'll describe how to | ||||
use it with AFL. | use it with AFL. | ||||
Building AFL | Building AFL | ||||
------------- | ------------- | ||||
It is recommended to always use the latest version of afl: | It is recommended to always use the latest version of afl: | ||||
``` | ``` | ||||
wget http://lcamtuf.coredump.cx/afl/releases/afl-latest.tgz | wget http://lcamtuf.coredump.cx/afl/releases/afl-latest.tgz | ||||
tar -zxvf afl-latest.tgz | tar -zxvf afl-latest.tgz | ||||
cd afl-<version> | cd afl-<version> | ||||
make | make | ||||
export AFLPATH=$PWD | export AFLPATH=$PWD | ||||
``` | ``` | ||||
Instrumentation | Instrumentation | ||||
---------------- | ---------------- | ||||
To build Bitcoin Core using AFL instrumentation (this assumes that the | To build Bitcoin ABC using AFL instrumentation (this assumes that the | ||||
`AFLPATH` was set as above): | `AFLPATH` was set as above): | ||||
``` | ``` | ||||
./configure --disable-ccache --disable-shared --enable-tests CC=${AFLPATH}/afl-gcc CXX=${AFLPATH}/afl-g++ | mkdir -p buildFuzzer | ||||
cd buildFuzzer | |||||
cmake -GNinja .. -CCACHE=OFF -DCMAKE_C_COMPILER=afl-gcc -DCMAKE_CXX_COMPILER=afl-g++ | |||||
export AFL_HARDEN=1 | export AFL_HARDEN=1 | ||||
cd src/ | ninja test_bitcoin_fuzzy | ||||
make test/test_bitcoin_fuzzy | |||||
``` | ``` | ||||
We disable ccache because we don't want to pollute the ccache with instrumented | We disable ccache because we don't want to pollute the ccache with instrumented | ||||
objects, and similarly don't want to use non-instrumented cached objects linked | objects, and similarly don't want to use non-instrumented cached objects linked | ||||
in. | in. | ||||
The fuzzing can be sped up significantly (~200x) by using `afl-clang-fast` and | The fuzzing can be sped up significantly (~200x) by using `afl-clang-fast` and | ||||
`afl-clang-fast++` in place of `afl-gcc` and `afl-g++` when compiling. When | `afl-clang-fast++` in place of `afl-gcc` and `afl-g++` when compiling. When | ||||
compiling using `afl-clang-fast`/`afl-clang-fast++` the resulting | compiling using `afl-clang-fast`/`afl-clang-fast++` the resulting | ||||
`test_bitcoin_fuzzy` binary will be instrumented in such a way that the AFL | `test_bitcoin_fuzzy` binary will be instrumented in such a way that the AFL | ||||
Show All 12 Lines | |||||
AFLIN=$PWD/inputs | AFLIN=$PWD/inputs | ||||
mkdir outputs | mkdir outputs | ||||
AFLOUT=$PWD/outputs | AFLOUT=$PWD/outputs | ||||
``` | ``` | ||||
Example inputs are available from: | Example inputs are available from: | ||||
- https://download.visucore.com/bitcoin/bitcoin_fuzzy_in.tar.xz | - https://download.visucore.com/bitcoin/bitcoin_fuzzy_in.tar.xz | ||||
- http://strateman.ninja/fuzzing.tar.xz | |||||
Extract these (or other starting inputs) into the `inputs` directory before starting fuzzing. | Extract these (or other starting inputs) into the `inputs` directory before starting fuzzing. | ||||
Fuzzing | Fuzzing | ||||
-------- | -------- | ||||
To start the actual fuzzing use: | To start the actual fuzzing use: | ||||
``` | ``` | ||||
$AFLPATH/afl-fuzz -i ${AFLIN} -o ${AFLOUT} -m52 -- test/test_bitcoin_fuzzy | $AFLPATH/afl-fuzz -i ${AFLIN} -o ${AFLOUT} -m52 -- src/test/test_bitcoin_fuzzy | ||||
``` | ``` | ||||
You may have to change a few kernel parameters to test optimally - `afl-fuzz` | You may have to change a few kernel parameters to test optimally - `afl-fuzz` | ||||
will print an error and suggestion if so. | will print an error and suggestion if so. |