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diff --git a/README.txt b/README.txt new file mode 100644 index 0000000..6f5764a --- /dev/null +++ b/README.txt @@ -0,0 +1,79 @@ +American Fuzzy Lop + Dyninst == AFL Fuzzing blackbox binaries + +The tool has two parts. The instrumentation tool and the instrumentation +library. Instrumentation library has an initialization callback and basic +block callback functions which are designed to emulate what AFL is doing +with afl-gcc/afl-g++/afl-as. +Instrumentation tool (afl-dyninst) instruments the supplied binary by +inserting callbacks for each basic block and an initialization +callback either at _init or at specified entry point. + +Usage: ./afl-dyninst -i <binary> -o <binary> -l <library> -e <address> -s <number> + -i: Input binary + -o: Output binary + -l: Library to instrument (repeat for more than one) + -e: Entry point address to patch (required for stripped binaries) + -r: Runtime library to instrument (path to, repeat for more than one) + -s: Number of basic blocks to skip + -v: Verbose output + +Switch -l is used to supply the names of the libraries that should +be instrumented along the binary. Instrumented libraries will be copied +to the current working directory. This option can be repeated as many times +as needed. Depending on the environment, the LD_LIBRARY_PATH should be set +to point to instrumented libraries while fuzzing. + +Switch -e is used to manualy specify the entry point where initialization +callback is to be inserted. For unstipped binaries, afl-dyninst defaults +to using _init of the binary as an entry point. In case of stripped binaries +this option is required and is best set to the address of main which +can easily be determined by disassembling the binary and looking for an +argument to __libc_start_main. + +Switch -s instructs afl-dyninst to skip the first <number> of basic +blocks. Currently, it is used to work around a bug in Dyninst +but doubles as an optimization option, as skipping the basic blocks +of the initialization rutines makes things run faster. If the instrumented +binary is crashing by itself, try skiping a number of blocks. + +Switch -r allows you to specify a path to the library that is loaded +via dlopen() at runtime. Instrumented runtime libraries will be +written to the same location with a ".ins" suffix as not to overwrite +the original ones. Make sure to backup the originals and then rename the +instrumented ones to original name. + +The instrumentation library "libDyninst.so" must be available in the current working +directory as that is where the instrumented binary will be looking for it. + +Compiling: + +1. Edit the Makefile and set DYNINST_ROOT and AFL_ROOT to appropriate paths. +2. make + +Example of running the tool: + +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 ./rar -o ./rar_ins -e 0x4034c0 -s 100 +Skipping library: libAflDyninst.so +Instrumenting module: DEFAULT_MODULE +Inserting init callback. +Saving the instrumented binary to ./rar_ins... +All done! Happy fuzzing! + +Here we are instrumenting the rar binary with entrypoint at 0x4034c0 +(manualy found address of main), skipping the first 100 basic blocks +and outputing to rar_ins. + +Running AFL on instrumented binary + +Since AFL checks if the binary has been instrumented by afl-gcc,AFL_SKIP_BIN_CHECK environment +variable needs to be set. No modifications to AFL it self 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 + + + |