Files
wget2/fuzz
Tim Rühsen da75b622d6 Rename wget_http_response_t -> wget_http_response
* include/wget/wget.h: Rename wget_http_response_t -> wget_http_response
* examples/batch_loader.c: Likewise
* examples/check_url_types.c: Likewise
* examples/getstream.c: Likewise
* examples/http_get.c: Likewise
* examples/http_get2.c: Likewise
* examples/http_multi_get.c: Likewise
* examples/websequencediagram.c: Likewise
* examples/websequencediagram_high.c: Likewise
* fuzz/libwget_http_client_fuzzer.c: Likewise
* fuzz/libwget_http_parse_fuzzer.c: Likewise
* libwget/http.c: Likewise
* libwget/http_highlevel.c: Likewise
* libwget/http_parse.c: Likewise
* libwget/ssl_gnutls.c: Likewise
* src/gpgme.c: Likewise
* src/stats_site.c: Likewise
* src/wget.c: Likewise
* src/wget_gpgme.h: Likewise
* src/wget_stats.h: Likewise
* tests/test-cookies-http_state.c: Likewise
* unit-tests/test-cookies-http_state.c: Likewise
* unit-tests/test.c: Likewise
2019-07-19 16:41:21 +02:00
..

Fuzzers

These are fuzzers designed for use with libFuzzer or afl. They can be used to run on Google's OSS-Fuzz (https://github.com/google/oss-fuzz/).

The convention used here is that the initial values for each parser fuzzer are taken from the $NAME.in directory.

Crash reproducers from OSS-Fuzz are put into $NAME.repro directory for regression testing with top dir 'make check' or 'make check-valgrind'.

Running a fuzzer using clang

Use the following commands on top dir:

export CC=clang
export CFLAGS="-O1 -g -fno-omit-frame-pointer -gline-tables-only -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=undefined,integer,nullability -fsanitize=address -fsanitize-address-use-after-scope -fsanitize-coverage=trace-pc-guard,trace-cmp"
export LIB_FUZZING_ENGINE="-lFuzzer -lstdc++"
./configure --enable-fuzzing --disable-doc --disable-manywarnings
make clean
make -j$(nproc)
cd fuzz

# run libwget_xml_parse_buffer_fuzzer
UBSAN_OPTIONS=print_stacktrace=1 ASAN_SYMBOLIZER_PATH=/usr/lib/llvm-7/bin/llvm-symbolizer \
  ./run-clang.sh libwget_xml_parse_buffer_fuzzer

If you see a crash, then a crash corpora is written that can be used for further investigation. E.g.

==2410==ERROR: AddressSanitizer: heap-use-after-free on address 0x602000004e90 at pc 0x00000049cf9c bp 0x7fffb5543f70 sp 0x7fffb5543720
...
Test unit written to ./crash-adc83b19e793491b1c6ea0fd8b46cd9f32e592fc

To reproduce the crash:

./libwget_xml_parse_buffer_fuzzer < ./crash-adc83b19e793491b1c6ea0fd8b46cd9f32e592fc

You can also copy/move that file into libwget_xml_parse_buffer_fuzzer.repro/ and re-build the project without fuzzing for a valgrind run, if you like that better. Just a ./configure (maybe with sanitizers enabled) and a make check-valgrind should reproduce it.

Running a fuzzer using AFL

Use the following commands on top dir:

$ CC=afl-clang-fast ./configure --disable-doc
$ make -j$(nproc) clean all
$ cd fuzz
$ ./run-afl.sh libwget_xml_parse_buffer_fuzzer

Fuzz code coverage using the corpus directories *.in/

Code coverage reports currently work best with gcc+lcov+genhtml.

In the top directory:

CC=gcc CFLAGS="-O0 -g" ./configure --disable-doc --disable-manywarnings
make fuzz-coverage
xdg-open lcov/index.html

Each fuzzer target has it's own files/functions to cover, e.g. libwget_xml_parse_buffer covers libwget/xml.c (except wget_xml_parse_file() and wget_html_parse_file()).

To work on corpora for better coverage, cd fuzz and use e.g. ./view-coverage.sh libwget_xml_parse_buffer_fuzzer.

Creating wget_options_fuzzer.dict

for i in `../src/wget2 --help|tr ' ' '\n'|grep ^--|cut -c 3-|sort`;do echo \"$i\"; done >wget_options_fuzzer.dict