diff --git a/llvm/docs/LibFuzzer.rst b/llvm/docs/LibFuzzer.rst index f8cdfbfdd5c4..983f47c6ffef 100644 --- a/llvm/docs/LibFuzzer.rst +++ b/llvm/docs/LibFuzzer.rst @@ -397,171 +397,13 @@ You should get an error pretty quickly:: artifact_prefix='./'; Test unit written to ./crash-b13e8756b13a00cf168300179061fb4b91fefbed -PCRE2 ------ +More examples +------------- -Here we show how to use libFuzzer on something real, yet simple: pcre2_:: +Examples of real-life fuzz targets and the bugs they find can be found +at http://tutorial.libfuzzer.info. Among other things you can learn how +to detect Heartbleed_ in one second. - COV_FLAGS=" -fsanitize-coverage=edge,indirect-calls,8bit-counters" - # Get PCRE2 - wget ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre2-10.20.tar.gz - tar xf pcre2-10.20.tar.gz - # Build PCRE2 with AddressSanitizer and coverage; requires autotools. - (cd pcre2-10.20; ./autogen.sh; CC="clang -fsanitize=address $COV_FLAGS" ./configure --prefix=`pwd`/../inst && make -j && make install) - # Build the fuzzing target function that does something interesting with PCRE2. - cat << EOF > pcre_fuzzer.cc - #include - #include - #include "pcre2posix.h" - extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) { - if (size < 1) return 0; - char *str = new char[size+1]; - memcpy(str, data, size); - str[size] = 0; - regex_t preg; - if (0 == regcomp(&preg, str, 0)) { - regexec(&preg, str, 0, 0, 0); - regfree(&preg); - } - delete [] str; - return 0; - } - EOF - clang++ -g -fsanitize=address $COV_FLAGS -c -std=c++11 -I inst/include/ pcre_fuzzer.cc - # Link. - clang++ -g -fsanitize=address -Wl,--whole-archive inst/lib/*.a -Wl,-no-whole-archive libFuzzer.a pcre_fuzzer.o -o pcre_fuzzer - -This will give you a binary of the fuzzer, called ``pcre_fuzzer``. -Now, create a directory that will hold the test corpus: - -.. code-block:: console - - mkdir -p CORPUS - -For simple input languages like regular expressions this is all you need. -For more complicated/structured inputs, the fuzzer works much more efficiently -if you can populate the corpus directory with a variety of valid and invalid -inputs for the code under test. -Now run the fuzzer with the corpus directory as the only parameter: - -.. code-block:: console - - ./pcre_fuzzer ./CORPUS - -Initially, you will see Output_ like this:: - - INFO: Seed: 2938818941 - INFO: -max_len is not provided, using 64 - INFO: A corpus is not provided, starting from an empty corpus - #0 READ units: 1 exec/s: 0 - #1 INITED cov: 3 bits: 3 units: 1 exec/s: 0 - #2 NEW cov: 176 bits: 176 indir: 3 units: 2 exec/s: 0 L: 64 MS: 0 - #8 NEW cov: 176 bits: 179 indir: 3 units: 3 exec/s: 0 L: 63 MS: 2 ChangeByte-EraseByte- - ... - #14004 NEW cov: 1500 bits: 4536 indir: 5 units: 406 exec/s: 0 L: 54 MS: 3 ChangeBit-ChangeBit-CrossOver- - -Now, interrupt the fuzzer and run it again the same way. You will see:: - - INFO: Seed: 3398349082 - INFO: -max_len is not provided, using 64 - #0 READ units: 405 exec/s: 0 - #405 INITED cov: 1499 bits: 4535 indir: 5 units: 286 exec/s: 0 - #587 NEW cov: 1499 bits: 4540 indir: 5 units: 287 exec/s: 0 L: 52 MS: 2 InsertByte-EraseByte- - #667 NEW cov: 1501 bits: 4542 indir: 5 units: 288 exec/s: 0 L: 39 MS: 2 ChangeBit-InsertByte- - #672 NEW cov: 1501 bits: 4543 indir: 5 units: 289 exec/s: 0 L: 15 MS: 2 ChangeASCIIInt-ChangeBit- - #739 NEW cov: 1501 bits: 4544 indir: 5 units: 290 exec/s: 0 L: 64 MS: 4 ShuffleBytes-ChangeASCIIInt-InsertByte-ChangeBit- - ... - -On the second execution the fuzzer has a non-empty input corpus (405 items). As -the first step, the fuzzer minimized this corpus (the ``INITED`` line) to -produce 286 interesting items, omitting inputs that do not hit any additional -code. - -(Aside: although the fuzzer only saves new inputs that hit additional code, this -does not mean that the corpus as a whole is kept minimized. For example, if -an input hitting A-B-C then an input that hits A-B-C-D are generated, -they will both be saved, even though the latter subsumes the former.) - - -You may run ``N`` independent fuzzer jobs in parallel on ``M`` CPUs: - -.. code-block:: console - - N=100; M=4; ./pcre_fuzzer ./CORPUS -jobs=$N -workers=$M - -By default (``-reload=1``) the fuzzer processes will periodically scan the corpus directory -and reload any new tests. This way the test inputs found by one process will be picked up -by all others. - -If ``-workers=$M`` is not supplied, ``min($N,NumberOfCpuCore/2)`` will be used. - -Heartbleed ----------- -Remember Heartbleed_? -As it was recently `shown `_, -fuzzing with AddressSanitizer_ can find Heartbleed. Indeed, here are the step-by-step instructions -to find Heartbleed with libFuzzer:: - - wget https://www.openssl.org/source/openssl-1.0.1f.tar.gz - tar xf openssl-1.0.1f.tar.gz - COV_FLAGS="-fsanitize-coverage=edge,indirect-calls" # -fsanitize-coverage=8bit-counters - (cd openssl-1.0.1f/ && ./config && - make -j 32 CC="clang -g -fsanitize=address $COV_FLAGS") - # Get and build libFuzzer - svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer - clang -c -g -O2 -std=c++11 Fuzzer/*.cpp -IFuzzer - # Get examples of key/pem files. - git clone https://github.com/hannob/selftls - cp selftls/server* . -v - cat << EOF > handshake-fuzz.cc - #include - #include - #include - #include - #include - - SSL_CTX *sctx; - int Init() { - SSL_library_init(); - SSL_load_error_strings(); - ERR_load_BIO_strings(); - OpenSSL_add_all_algorithms(); - assert (sctx = SSL_CTX_new(TLSv1_method())); - assert (SSL_CTX_use_certificate_file(sctx, "server.pem", SSL_FILETYPE_PEM)); - assert (SSL_CTX_use_PrivateKey_file(sctx, "server.key", SSL_FILETYPE_PEM)); - return 0; - } - extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { - static int unused = Init(); - SSL *server = SSL_new(sctx); - BIO *sinbio = BIO_new(BIO_s_mem()); - BIO *soutbio = BIO_new(BIO_s_mem()); - SSL_set_bio(server, sinbio, soutbio); - SSL_set_accept_state(server); - BIO_write(sinbio, Data, Size); - SSL_do_handshake(server); - SSL_free(server); - return 0; - } - EOF - # Build the fuzzer. - clang++ -g handshake-fuzz.cc -fsanitize=address \ - openssl-1.0.1f/libssl.a openssl-1.0.1f/libcrypto.a Fuzzer*.o - # Run 20 independent fuzzer jobs. - ./a.out -jobs=20 -workers=20 - -Voila:: - - #1048576 pulse cov 3424 bits 0 units 9 exec/s 24385 - ================================================================= - ==17488==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x629000004748 at pc 0x00000048c979 bp 0x7fffe3e864f0 sp 0x7fffe3e85ca8 - READ of size 60731 at 0x629000004748 thread T0 - #0 0x48c978 in __asan_memcpy - #1 0x4db504 in tls1_process_heartbeat openssl-1.0.1f/ssl/t1_lib.c:2586:3 - #2 0x580be3 in ssl3_read_bytes openssl-1.0.1f/ssl/s3_pkt.c:1092:4 - -Note: a `similar fuzzer `_ -is now a part of the BoringSSL_ source tree. Advanced features ================= diff --git a/llvm/docs/ProgrammersManual.rst b/llvm/docs/ProgrammersManual.rst index 4608a9c15e44..e6362b864aa5 100644 --- a/llvm/docs/ProgrammersManual.rst +++ b/llvm/docs/ProgrammersManual.rst @@ -337,6 +337,7 @@ Failure values are constructed using ``make_error``, where ``T`` is any class that inherits from the ErrorInfo utility, E.g.: .. code-block:: c++ + class BadFileFormat : public ErrorInfo { public: static char ID;