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116 lines
3.9 KiB
Plaintext
116 lines
3.9 KiB
Plaintext
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Fuzzing binary-only programs with afl++
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=======================================
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afl++, libfuzzer and others are great if you have the source code, and
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it allows for very fast and coverage guided fuzzing.
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However, if there is only the binary program and not source code available,
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then standard afl++ (dumb mode) is not effective.
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The following is a description of how these can be fuzzed with afl++
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!!!!!
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DTLR: try DYNINST with afl-dyninst. If it produces too many crashes then
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use afl -Q qemu_mode.
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!!!!!
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QEMU
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----
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Qemu is the "native" solution to the program.
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It is available in the ./qemu_mode/ directory and once compiled it can
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be accessed by the afl-fuzz -Q command line option.
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The speed decrease is at about 50%
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It the easiest to use alternative and even works for cross-platform binaries.
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As it is included in afl++ this needs no URL.
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DYNINST
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-------
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Dyninst is a binary instrumentation framework similar to Pintool and Dynamorio
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(see far below). Howver whereas Pintool and Dynamorio work at runtime, dyninst
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instruments the target at load time, and then let it run.
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This is great for some things, e.g. fuzzing, and not so effective for others,
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e.g. malware analysis.
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So what we can do with dyninst is taking every basic block, and put afl's
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instrumention code in there - and then save the binary.
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Afterwards we can just fuzz the newly saved target binary with afl-fuzz.
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Sounds great? It is. The issue though - this is a non-trivial problem to
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insert instructions, which changes addresses in the process space and that
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everything still works afterwards. Hence more often than not binaries
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crash when they are run.
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The speed decrease is about 15-35%, depending on the optimization options
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used with afl-dyninst.
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So if dyninst works, its the best option available. Otherwise it just doesn't
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work well.
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https://github.com/vanhauser-thc/afl-dyninst
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INTEL-PT
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--------
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The big issue with Intel's PT is the small buffer size and the complex
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encoding of the debug information collected through PT.
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This makes the decoding very CPU intensive and hence slow.
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As a result, the overall speed decrease is about 70-90% (depending on
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the implementation and other factors)
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there are two afl intel-pt implementations:
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1. https://github.com/junxzm1990/afl-pt
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=> this needs Ubuntu 14.04.05 without any updates and the 4.4 kernel.
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2. https://github.com/hunter-ht-2018/ptfuzzer
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=> this needs a 4.14 or 4.15 kernel. the "nopti" kernel boot option must
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be used. This one is faster than the other.
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CORESIGHT
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---------
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Coresight is the ARM answer to Intel's PT.
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There is no implementation so far which handle coresight and getting
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it working on an ARM Linux is very difficult due custom kernel building
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on embedded systems is difficult. And finding one that has coresight in
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the ARM chip is difficult too.
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My guess is that it is slower than Qemu, but faster than Intel PT.
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If anyone finds any coresight implemention for afl please ping me:
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vh@thc.org
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PIN & DYNAMORIO
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---------------
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Pintool and Dynamorio are dynamic instrumentation engines, and they can be
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used for getting basic block information at runtime.
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Pintool is only available for Intel x32/x64 on Linux, Mac OS and Windows
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whereas Dynamorio is additionally available for ARM and AARCH64.
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Dynamorio is also 10x faster than Pintool.
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The big issue with Dynamorio (and therefore Pintool too) is speed.
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Dynamorio has a speed decrease of 98-99%
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Pintool has a speed decrease of 99.5%
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Hence Dynamorio is the option to go for if everything fails, and Pintool
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only if Dynamorio fails too.
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Dynamorio solutions:
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https://github.com/vanhauser-thc/afl-dynamorio
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https://github.com/mxmssh/drAFL
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https://github.com/googleprojectzero/winafl/ <= very good but windows only
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Pintool solutions:
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https://github.com/vanhauser-thc/afl-pin
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https://github.com/mothran/aflpin
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https://github.com/spinpx/afl_pin_mode <= only old Pintool version supported
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That's it!
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News, corrections, updates?
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Email vh@thc.org
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