diff options
| -rw-r--r-- | README.md | 7 | ||||
| -rw-r--r-- | docs/Changelog.md | 4 | ||||
| -rw-r--r-- | docs/env_variables.md | 4 | ||||
| -rw-r--r-- | include/afl-fuzz.h | 2 | ||||
| -rw-r--r-- | include/envs.h | 1 | ||||
| -rw-r--r-- | instrumentation/README.lto.md | 28 | ||||
| -rw-r--r-- | src/afl-fuzz-state.c | 7 | ||||
| -rw-r--r-- | src/afl-fuzz-stats.c | 14 | ||||
| -rw-r--r-- | src/afl-fuzz.c | 1 |
9 files changed, 67 insertions, 1 deletions
diff --git a/README.md b/README.md index 438f9425..b3e464e1 100644 --- a/README.md +++ b/README.md @@ -473,6 +473,13 @@ compiler is used. Also - if possible - you should always configure the build system such that the target is compiled statically and not dynamically. How to do this is described below. +The #1 rule when instrumenting a target is: avoid instrumenting shared +libraries at all cost. You would need to set LD_LIBRARY_PATH to point to +these, you could accidently type "make install" and install them system wide - +so don't. Really don't. +**Always compile libraries you want to have instrumented as static and link +these to the target program!** + Then build the target. (Usually with `make`) **NOTES** diff --git a/docs/Changelog.md b/docs/Changelog.md index c5ff8adb..daa014e4 100644 --- a/docs/Changelog.md +++ b/docs/Changelog.md @@ -9,6 +9,10 @@ Want to stay in the loop on major new features? Join our mailing list by sending a mail to <afl-users+subscribe@googlegroups.com>. ### Version ++3.15a (dev) + - afl-fuzz: + added AFL_IGNORE_PROBLEMS plus checks to identify and abort on + incorrect LTO usage setups and enhanced the READMEs for better + information on how to deal with instrumenting libraries - added the very good grammar mutator "GramaTron" to the custom_mutators - added optimin, a faster and better corpus minimizer by diff --git a/docs/env_variables.md b/docs/env_variables.md index cceffa68..0686f1a8 100644 --- a/docs/env_variables.md +++ b/docs/env_variables.md @@ -432,6 +432,10 @@ checks or alter some of the more exotic semantics of the tool: and RECORD:000000,cnt:000009 being the crash case. NOTE: This option needs to be enabled in config.h first! + - If afl-fuzz encounters an incorrect fuzzing setup during a fuzzing session + (not at startup), it will terminate. If you do not want this then you can + set `AFL_IGNORE_PROBLEMS`. + - If you are Jakub, you may need `AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES`. Others need not apply, unless they also want to disable the `/proc/sys/kernel/core_pattern` check. diff --git a/include/afl-fuzz.h b/include/afl-fuzz.h index 3d528bc4..4b19e698 100644 --- a/include/afl-fuzz.h +++ b/include/afl-fuzz.h @@ -384,7 +384,7 @@ typedef struct afl_env_vars { afl_force_ui, afl_i_dont_care_about_missing_crashes, afl_bench_just_one, afl_bench_until_crash, afl_debug_child, afl_autoresume, afl_cal_fast, afl_cycle_schedules, afl_expand_havoc, afl_statsd, afl_cmplog_only_new, - afl_exit_on_seed_issues, afl_try_affinity; + afl_exit_on_seed_issues, afl_try_affinity, afl_ignore_problems; u8 *afl_tmpdir, *afl_custom_mutator_library, *afl_python_module, *afl_path, *afl_hang_tmout, *afl_forksrv_init_tmout, *afl_preload, diff --git a/include/envs.h b/include/envs.h index 26cc250f..49605330 100644 --- a/include/envs.h +++ b/include/envs.h @@ -88,6 +88,7 @@ static char *afl_environment_variables[] = { "AFL_HARDEN", "AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES", "AFL_IGNORE_UNKNOWN_ENVS", + "AFL_IGNORE_PROBLEMS", "AFL_IMPORT_FIRST", "AFL_INST_LIBS", "AFL_INST_RATIO", diff --git a/instrumentation/README.lto.md b/instrumentation/README.lto.md index 626bc9cb..38252308 100644 --- a/instrumentation/README.lto.md +++ b/instrumentation/README.lto.md @@ -138,6 +138,34 @@ make NOTE: some targets also need to set the linker, try both `afl-clang-lto` and `afl-ld-lto` for `LD=` before `configure`. +## Instrumenting shared libraries + +Note: this is highly discouraged! Try to compile to static libraries with +afl-clang-lto instead of shared libraries! + +To make instrumented shared libraries work with afl-clang-lto you have to do +quite some extra steps. + +Every shared library you want to instrument has to be individually compiled- +The environment variable `AFL_LLVM_LTO_DONTWRITEID=1` has to be set during +compilation. +Additionally the environment variable `AFL_LLVM_LTO_STARTID` has to be set to +the combined edge values of all previous compiled instrumented shared +libraries for that target. +E.g. for the first shared library this would be `AFL_LLVM_LTO_STARTID=0` and +afl-clang-lto will then report how many edges have been instrumented (let's say +it reported 1000 instrumented edges). +The second shared library then has to be set to that value +(`AFL_LLVM_LTO_STARTID=1000` in our example), the third to all previous +combined, etc. + +The final program compilation step then may *not* have `AFL_LLVM_LTO_DONTWRITEID` +set, and `AFL_LLVM_LTO_STARTID` must be set to all combined edges of all shared +libaries it will be linked to. + +This is quite some hands-on work, so better stay away from instrumenting +shared libraries :-) + ## AUTODICTIONARY feature While compiling, a dictionary based on string comparisons is automatically diff --git a/src/afl-fuzz-state.c b/src/afl-fuzz-state.c index b832c11e..24ccc108 100644 --- a/src/afl-fuzz-state.c +++ b/src/afl-fuzz-state.c @@ -267,6 +267,13 @@ void read_afl_environment(afl_state_t *afl, char **envp) { afl->afl_env.afl_force_ui = get_afl_env(afl_environment_variables[i]) ? 1 : 0; + } else if (!strncmp(env, "AFL_IGNORE_PROBLEMS", + + afl_environment_variable_len)) { + + afl->afl_env.afl_ignore_problems = + get_afl_env(afl_environment_variables[i]) ? 1 : 0; + } else if (!strncmp(env, "AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES", afl_environment_variable_len)) { diff --git a/src/afl-fuzz-stats.c b/src/afl-fuzz-stats.c index ead65b1d..a9deb22d 100644 --- a/src/afl-fuzz-stats.c +++ b/src/afl-fuzz-stats.c @@ -534,6 +534,20 @@ void show_stats(afl_state_t *afl) { t_bytes = count_non_255_bytes(afl, afl->virgin_bits); t_byte_ratio = ((double)t_bytes * 100) / afl->fsrv.real_map_size; + if (unlikely(t_bytes > afl->fsrv.real_map_size)) { + + if (unlikely(!afl->afl_env.afl_ignore_problems)) { + + FATAL( + "Incorrect fuzzing setup detected. Your target seems to have loaded " + "incorrectly instrumented shared libraries. If you use LTO mode " + "please see instrumentation/README.lto.md. To ignore this problem " + "and continue fuzzing just set 'AFL_IGNORE_PROBLEMS=1'.\n"); + + } + + } + if (likely(t_bytes) && unlikely(afl->var_byte_count)) { stab_ratio = 100 - (((double)afl->var_byte_count * 100) / t_bytes); diff --git a/src/afl-fuzz.c b/src/afl-fuzz.c index 9b9e01a4..8ffc0e77 100644 --- a/src/afl-fuzz.c +++ b/src/afl-fuzz.c @@ -216,6 +216,7 @@ static void usage(u8 *argv0, int more_help) { "AFL_HANG_TMOUT: override timeout value (in milliseconds)\n" "AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES: don't warn about core dump handlers\n" "AFL_IGNORE_UNKNOWN_ENVS: don't warn on unknown env vars\n" + "AFL_IGNORE_PROBLEMS: do not abort fuzzing if an incorrect setup is detected during a run\n" "AFL_IMPORT_FIRST: sync and import test cases from other fuzzer instances first\n" "AFL_KILL_SIGNAL: Signal ID delivered to child processes on timeout, etc. (default: SIGKILL)\n" "AFL_MAP_SIZE: the shared memory size for that target. must be >= the size\n" |