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Release Version: 1.1

TinyAFL is built on top of AFL and TinyInst.

It can be fuzz on windows user-mode application without source (supports both x32 and x64) but it is not so reliable and dirty. It still has some instrument bugs, I will fix it when I fully understand TinyInst :P


  1. Features
  2. How to compile TinyAFL
  3. How to fuzz a target

Features of TinyAFL

TinyAFL works similarly to WinAFL. However I use TinyInst (commit e098622dd421f808eba027d62e126134b812f4c8) for coverage. More about TinyInst can be found here.

TinyAFL supports AFLfast's power schedules by Marcel Böhme and MOpt mutator of MOpt-AFL. I add these features based on afl++


Known CVEs

I have reported some MediaFoundations bugs using this tool. * [Microsoft] CVE-2020-1319, CVE-2020-17105, CVE-2020-17109, CVE-2020-17022, CVE-2021-1643, CVE-2021-1644 ... * [Microsoft] CVE-2021-24080 - found by Symeon Paraschoudis

Building TinyAFL

Although TinyAFL x64 can run both for 32bit and 64bit targets, I still recommend TinyAFL 32bit for 32bit targets and TinyAFL 64bit for 64bit targets.

  1. Open a terminal and set up your build environment (e.g. On Windows, run vcvars64.bat / vcvars32.bat)
  2. Navigate to the directory containing the source
  3. Run the following commands (change the generator according to the version of IDE and platform you want to build for): #### For a 32-bit build
    mkdir build32
    cd build32
    cmake -G"Visual Studio 15 2017" ..
    cmake --build . --config Release
    #### For a 64-bit build
    mkdir build64
    cd build64
    cmake -G"Visual Studio 15 2017 Win64" ..
    cmake --build . --config Release
    ## How to fuzz with TinyAFL The command line for TinyAFL:
    AFL.exe [ afl options ] -- target_cmd_line
    The following TinyAFL options are supported: ``` Required parameters:

-i dir - input directory with test cases -o dir - output directory for fuzzer findings

Execution control settings:

-p schedule - power schedules recompute a seed's performance score. -f file - location read by the fuzzed program (stdin) -t msec - timeout for each run -Q - use binary-only instrumentation (QEMU mode)

Mutator settings:

-L minutes - use MOpt(imize) mode and set the time limit for entering the pacemaker mode (minutes of no new paths). 0 = immediately, -1 = immediately and together with normal mutation).

Fuzzing behavior settings:

-x dir - optional fuzzer dictionary (see README)

Other stuff:

-M / -S id - distributed mode (see parallelfuzzing.txt) -C - crash exploration mode (the peruvian rabbit thing) -e ext - file extension for the fuzz test input file (if needed) -headeronly - mutate only header of testcase (if needed) -sizeofheader - size of header will mutate when use option -header_only (default: 0x200)

tiny-afl settings:

-instrument_module path - path to instrumented PE ``` I add the feature to only mutate the test case header when fuzz (depending on the file format). I believe that some file format exceptions only happen when fields in the header change. To see the supported instrument flags, please refer to the mode-specific documentation at TinyInst.

Example command TinyAFL

AFL.exe -i in -o out -p fast -t 10000 -callconv fastcall -target_offset 0x1260 -nargs 2 -loop -persist -iterations 10000 -instrument_module demo.dll -target_module test.exe -- test.exe @@

Corpus minimization

python -h
Examples of use:
 * Typical use -t 5000 -i in -o min -p demo.dll -- test.exe
 * Dry-run, keep crashes only with 4 workers with a working directory: -C --dry-run -w 4 --working-dir D:\dir -i in -i C:\fuzz\in -o min -p demo.dll -- test.exe @@
 * Read specific file on specific location -t 5000 -i in -o min -f foo.ext -p m.dll -- test.exe @@
 * Read from specific file with pattern -t 5000 -i in -o min -f [email protected]@-foo.ext -p demo.dll -- test.exe @@

Minimize testcase

afl-tmin.exe -h
afl-tmin.exe [ options ] -- /path/to/target_app [ ... ]

Required parameters:

-i file - input test case to be shrunk by the tool -o file - final output location for the minimized data -instrument_module module - target module to test

Execution control settings:

-t msec - timeout for each run (10000 ms)

Special Thanks

Special thanks to Ivan Fratric "ifsecure" security researcher of Google Project Zero has published a great tool for coverage-guided

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