- target ClientSession::_handleInput(), since crashing there would bring
down the whole loolwsd (not just a kit process), and it deals with
input from untrusted users (browsers)
- add a --enable-fuzzers configure switch to build with
-fsanitize=fuzzer (compared to normal sanitizers build, this is the only
special flag needed)
- configuring other sanitizers is not done automatically, either use
--with-sanitizer=... or the environment variables from LODE's sanitizer
config
- run the actual fuzzer like this:
./clientsession_fuzzer -max_len=16384 fuzzer/data/
- note that at least openSUSE Leap 15.1 sadly ships with a clang with
libfuzzer static libs removed from the package, so you need a
self-built clang to run the fuzzer (either manual build or one from
LODE)
- <https://chromium.googlesource.com/chromium/src/testing/libfuzzer/+/refs/heads/master/efficient_fuzzing.md#execution-speed>
suggests that "You should aim for at least 1,000 exec/s from your fuzz
target locally" (i.e. one run should not take more than 1 ms), so try
this minimal approach first. The alternative would be to start from the
existing loolwsd_fuzzer binary, then step by step cut it down to not
fork(), not do any network traffic, etc -- till it's fast enough that
the fuzzer can find interesting input
- the various configurations start to be really complex (the matrix is
just very large), so try to use Util::isFuzzing() for fuzzer-specific
changes (this is what core.git does as well), and only resort to ifdefs
for the Util::isFuzzing() itself
Change-Id: I72dc1193b34c93eacb5d8e39cef42387d42bd72f
Reviewed-on: https://gerrit.libreoffice.org/c/online/+/89226
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
==13901==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x000000904678 bp 0x7ffdb9e21580 sp 0x7ffdb9e21340 T0)
==13901==The signal is caused by a READ memory access.
==13901==Hint: address points to the zero page.
#0 0x904677 in LOOLProtocol::tokenize[abi:cxx11](char const*, unsigned long, char) common/Protocol.hpp:113:40
#1 0x898c52 in LOOLProtocol::tokenize(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, char) common/Protocol.hpp:141:16
#2 0x18dc2d9 in LOOLProtocol::ParseVersion(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) common/Protocol.cpp:35:51
#3 0x1148824 in ClientSession::_handleInput(char const*, int) wsd/ClientSession.cpp:358:64
#4 0x18efcb8 in Session::handleMessage(bool, WSOpCode, std::vector<char, std::allocator<char> >&) common/Session.cpp:232:13
Next commit will add the actual simple fuzzer that found this.
Change-Id: I8623b4451a57390f6f84c11084c5a1120a11fcc5
Reviewed-on: https://gerrit.libreoffice.org/c/online/+/89225
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
