mirror of
https://github.com/nlohmann/json.git
synced 2024-12-21 20:07:51 +08:00
82 lines
3.1 KiB
Markdown
82 lines
3.1 KiB
Markdown
# Fuzz testing
|
|
|
|
Each parser of the library (JSON, BJData, BSON, CBOR, MessagePack, and UBJSON) can be fuzz tested. Currently,
|
|
[libFuzzer](https://llvm.org/docs/LibFuzzer.html) and [afl++](https://github.com/AFLplusplus/AFLplusplus) are supported.
|
|
|
|
## Corpus creation
|
|
|
|
For most effective fuzzing, a [corpus](https://llvm.org/docs/LibFuzzer.html#corpus) should be provided. A corpus is a
|
|
directory with some simple input files that cover several features of the parser and is hence a good starting point
|
|
for mutations.
|
|
|
|
```shell
|
|
TEST_DATA_VERSION=3.1.0
|
|
wget https://github.com/nlohmann/json_test_data/archive/refs/tags/v$TEST_DATA_VERSION.zip
|
|
unzip v$TEST_DATA_VERSION.zip
|
|
rm v$TEST_DATA_VERSION.zip
|
|
for FORMAT in json bjdata bson cbor msgpack ubjson
|
|
do
|
|
rm -fr corpus_$FORMAT
|
|
mkdir corpus_$FORMAT
|
|
find json_test_data-$TEST_DATA_VERSION -size -5k -name "*.$FORMAT" -exec cp "{}" "corpus_$FORMAT" \;
|
|
done
|
|
rm -fr json_test_data-$TEST_DATA_VERSION
|
|
```
|
|
|
|
The generated corpus can be used with both libFuzzer and afl++. The remainder of this documentation assumes the corpus
|
|
directories have been created in the `tests` directory.
|
|
|
|
## libFuzzer
|
|
|
|
To use libFuzzer, you need to pass `-fsanitize=fuzzer` as `FUZZER_ENGINE`. In the `tests` directory, call
|
|
|
|
```shell
|
|
make fuzzers FUZZER_ENGINE="-fsanitize=fuzzer"
|
|
```
|
|
|
|
This creates a fuzz tester binary for each parser that supports these
|
|
[command line options](https://llvm.org/docs/LibFuzzer.html#options).
|
|
|
|
In case your default compiler is not a Clang compiler that includes libFuzzer (Clang 6.0 or later), you need to set the
|
|
`CXX` variable accordingly. Note the compiler provided by Xcode (AppleClang) does not contain libFuzzer. Please install
|
|
Clang via Homebrew calling `brew install llvm` and add `CXX=$(brew --prefix llvm)/bin/clang` to the `make` call:
|
|
|
|
```shell
|
|
make fuzzers FUZZER_ENGINE="-fsanitize=fuzzer" CXX=$(brew --prefix llvm)/bin/clang
|
|
```
|
|
|
|
Then pass the corpus directory as command-line argument (assuming it is located in `tests`):
|
|
|
|
```shell
|
|
./parse_cbor_fuzzer corpus_cbor
|
|
```
|
|
|
|
The fuzzer should be able to run indefinitely without crashing. In case of a crash, the tested input is dumped into
|
|
a file starting with `crash-`.
|
|
|
|
## afl++
|
|
|
|
To use afl++, you need to pass `-fsanitize=fuzzer` as `FUZZER_ENGINE`. It will be replaced by a `libAFLDriver.a` to
|
|
re-use the same code written for libFuzzer with afl++. Furthermore, set `afl-clang-fast++` as compiler.
|
|
|
|
```shell
|
|
CXX=afl-clang-fast++ make fuzzers FUZZER_ENGINE="-fsanitize=fuzzer"
|
|
```
|
|
|
|
Then the fuzzer is called like this in the `tests` directory:
|
|
|
|
```shell
|
|
afl-fuzz -i corpus_cbor -o out -- ./parse_cbor_fuzzer
|
|
```
|
|
|
|
The fuzzer should be able to run indefinitely without crashing. In case of a crash, the tested input is written to the
|
|
directory `out`.
|
|
|
|
## OSS-Fuzz
|
|
|
|
The library is further fuzz-tested 24/7 by Google's [OSS-Fuzz project](https://github.com/google/oss-fuzz). It uses
|
|
the same `fuzzers` target as above and also relies on the `FUZZER_ENGINE` variable. See the used
|
|
[build script](https://github.com/google/oss-fuzz/blob/master/projects/json/build.sh) for more information.
|
|
|
|
In case the build at OSS-Fuzz fails, an issue will be created automatically.
|