[llvm] r285337 - [libFuzzer] remove large examples from the libFuzzer docs and link to the libFuzzer tutorial instead; also fix a build error in another file
Kostya Serebryany via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 27 13:14:03 PDT 2016
Author: kcc
Date: Thu Oct 27 15:14:03 2016
New Revision: 285337
URL: http://llvm.org/viewvc/llvm-project?rev=285337&view=rev
Log:
[libFuzzer] remove large examples from the libFuzzer docs and link to the libFuzzer tutorial instead; also fix a build error in another file
Modified:
llvm/trunk/docs/LibFuzzer.rst
llvm/trunk/docs/ProgrammersManual.rst
Modified: llvm/trunk/docs/LibFuzzer.rst
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/LibFuzzer.rst?rev=285337&r1=285336&r2=285337&view=diff
==============================================================================
--- llvm/trunk/docs/LibFuzzer.rst (original)
+++ llvm/trunk/docs/LibFuzzer.rst Thu Oct 27 15:14:03 2016
@@ -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 <string.h>
- #include <stdint.h>
- #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 <https://blog.hboeck.de/archives/868-How-Heartbleed-couldve-been-found.html>`_,
-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 <openssl/ssl.h>
- #include <openssl/err.h>
- #include <assert.h>
- #include <stdint.h>
- #include <stddef.h>
-
- 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 <https://boringssl.googlesource.com/boringssl/+/HEAD/FUZZING.md>`_
-is now a part of the BoringSSL_ source tree.
Advanced features
=================
Modified: llvm/trunk/docs/ProgrammersManual.rst
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ProgrammersManual.rst?rev=285337&r1=285336&r2=285337&view=diff
==============================================================================
--- llvm/trunk/docs/ProgrammersManual.rst (original)
+++ llvm/trunk/docs/ProgrammersManual.rst Thu Oct 27 15:14:03 2016
@@ -337,6 +337,7 @@ Failure values are constructed using ``m
that inherits from the ErrorInfo utility, E.g.:
.. code-block:: c++
+
class BadFileFormat : public ErrorInfo<BadFileFormat> {
public:
static char ID;
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