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diff --git a/README.md b/README.md index 0757685..88522aa 100644 --- a/README.md +++ b/README.md @@ -12,22 +12,23 @@ callback either at _init or at specified entry point. ## Building / Compiling -0. Clone, compile and install dyninst: https://github.com/dyninst/dyninst/ +1. Clone, compile and install dyninst: https://github.com/dyninst/dyninst/ Note that you could also use dyninst 9.3.2, but has less platform support and quite a few bugs. For using dyninst 9.x you have to edit the Makefile Using at least 10.0.1 is highly recommended. +NOTE: You should use at least dyninst 10.0.1 ! -1. Edit the Makefile and set DYNINST_ROOT and AFL_ROOT to appropriate paths. +2. Download and install afl++ from https://github.com/vanhauser-thc/AFLplusplus +It's an up to date and enhanced version to the original afl with better +performance, new features and bugfixes. -2. make +3. Edit the Makefile and set DYNINST_ROOT and AFL_ROOT to appropriate paths. -3. make install +4. make -4. Download and install afl++ from https://github.com/vanhauser-thc/AFLplusplus -It's an up to date and enhanced version to the original afl with better -performance, new features and bugfixes. +5. sudo make install ### Building dyninst 10 @@ -117,11 +118,12 @@ level 1 (-x) is highly recommended (+50%). level 2 (-xx) gives an additonal 40% but removes (usually unnecessary) precautions -## Example of running the tool +## Example of instrumenting a target binary Dyninst requires DYNINSTAPI_RT_LIB environment variable to point to the location of libdyninstAPI_RT.so. +``` $ export DYNINSTAPI_RT_LIB=/usr/local/lib/libdyninstAPI_RT.so $ ./afl-dyninst -i ./unrar -o ./rar_ins -e 0x4034c0 -s 10 Skipping library: libAflDyninst.so @@ -129,13 +131,17 @@ Instrumenting module: DEFAULT_MODULE Inserting init callback. Saving the instrumented binary to ./unrar_ins... All done! Happy fuzzing! +``` Here we are instrumenting the rar binary with entrypoint at 0x4034c0 (manually found address of main), skipping the first 10 basic blocks and outputing to unrar_ins You can also use the afl-dyninst.sh helper script which sets the required -environment variables for you. +environment variables for you: +``` +$ ./afl-dyninst.sh -i ./unrar -o ./rar_ins -e 0x4034c0 -s 10 +``` ## Running AFL on the instrumented binary @@ -146,10 +152,36 @@ directory or LD_LIBRARY_PATH as that is where the instrumented binary will be lo Since AFL checks if the binary has been instrumented by afl-gcc, the AFL_SKIP_BIN_CHECK environment variable needs to be set. No modifications to AFL itself is needed. +``` $ export AFL_SKIP_BIN_CHECK=1 +``` Then, AFL can be run as usual: +``` $ afl-fuzz -i testcases/archives/common/gzip/ -o test_gzip -- ./gzip_ins -d -c +``` You can also use the afl-fuzz-dyninst.sh helper script which sets the required environment variables for you. +``` +$ afl-fuzz-dyninst.sh -i testcases/archives/common/gzip/ -o test_gzip -- ./gzip_ins -d -c +``` + +## Problems + +After instrumenting the target binary always check if it works. +Dyninst is making big changes to the code, and hence more often than not +things are not working anymore. + +Problem 1: The binary does not work (crashes or hangs) +Solution: increase the -m parameter. -m 8 is the minimum recommended, on some + targets -m 16 is required etc. + +Problem 2: Basically every fuzzing test case is reported as crash although it + does not when running it from the command line +Solution: This happens if the target is using throw/catch, and dyninst's + modification result in that the cought exception is not resetted and + hence abort() is triggered. + No solution to this issue is known yet. + Binary editing the target binary to perform _exit(0) would help though. +More problems? Create an issue at https://github.com/vanhauser-thc/afl-dyninst |