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Diffstat (limited to 'docs/env_variables.md')
| -rw-r--r-- | docs/env_variables.md | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/docs/env_variables.md b/docs/env_variables.md index 26128b01..f7745247 100644 --- a/docs/env_variables.md +++ b/docs/env_variables.md @@ -5,6 +5,10 @@ users or for some types of custom fuzzing setups. See [README.md](README.md) for the general instruction manual. + Note that most tools will warn on any unknown AFL environment variables. + This is for warning on typos that can happen. If you want to disable this + check then set the `AFL_IGNORE_UNKNOWN_ENVS` environment variable. + ## 1) Settings for all compilers Starting with afl++ 3.0 there is only one compiler: afl-cc @@ -18,7 +22,6 @@ To select the different instrumentation modes this can be done by `MODE` can be one of `LTO` (afl-clang-lto*), `LLVM` (afl-clang-fast*), `GCC_PLUGIN` (afl-g*-fast) or `GCC` (afl-gcc/afl-g++). - Because (with the exception of the --afl-MODE command line option) the compile-time tools do not accept afl specific command-line options, they make fairly broad use of environmental variables instead: @@ -287,6 +290,11 @@ checks or alter some of the more exotic semantics of the tool: the target. This must be equal or larger than the size the target was compiled with. + - `AFL_CMPLOG_ONLY_NEW` will only perform the expensive cmplog feature for + newly found testcases and not for testcases that are loaded on startup + (`-i in`). This is an important feature to set when resuming a fuzzing + session. + - `AFL_TESTCACHE_SIZE` allows you to override the size of `#define TESTCASE_CACHE` in config.h. Recommended values are 50-250MB - or more if your fuzzing finds a huge amount of paths for large inputs. @@ -431,13 +439,18 @@ checks or alter some of the more exotic semantics of the tool: normally done when starting up the forkserver and causes a pretty significant performance drop. - - Setting `AFL_STATSD` enable StatsD metrics collection. + - Setting `AFL_STATSD` enables StatsD metrics collection. By default AFL++ will send these metrics over UDP to 127.0.0.1:8125. - The host and port are configurable with `AFL_STATSD_HOST` and `AFL_STATSD_PORT` - respectively. - To get the most out of this, you should provide `AFL_STATSD_TAGS_FLAVOR` that - matches your StatsD server. - Available flavors are `dogstatsd`, `librato`, `signalfx` and `influxdb`. + The host and port are configurable with `AFL_STATSD_HOST` and `AFL_STATSD_PORT` respectively. + To enable tags (banner and afl_version) you should provide `AFL_STATSD_TAGS_FLAVOR` that matches + your StatsD server (see `AFL_STATSD_TAGS_FLAVOR`) + + - Setting `AFL_STATSD_TAGS_FLAVOR` to one of `dogstatsd`, `librato`, `signalfx` or `influxdb` + allows you to add tags to your fuzzing instances. This is especially useful when running + multiple instances (`-M/-S` for example). Applied tags are `banner` and `afl_version`. + `banner` corresponds to the name of the fuzzer provided through `-M/-S`. + `afl_version` corresponds to the currently running afl version (e.g `++3.0c`). + Default (empty/non present) will add no tags to the metrics. - Setting `AFL_CRASH_EXITCODE` sets the exit code afl treats as crash. For example, if `AFL_CRASH_EXITCODE='-1'` is set, each input resulting @@ -504,6 +517,12 @@ The QEMU wrapper used to instrument binary-only code supports several settings: stack pointer in which QEMU can find the return address when `start addr` is hit. + - With `AFL_USE_QASAN` you can enable QEMU AddressSanitizer for dynamically + linked binaries. + + - With `AFL_QEMU_FORCE_DFL` you force QEMU to ignore the registered signal + handlers of the target. + ## 6) Settings for afl-cmin The corpus minimization script offers very little customization: @@ -519,7 +538,7 @@ The corpus minimization script offers very little customization: a modest security risk on multi-user systems with rogue users, but should be safe on dedicated fuzzing boxes. -# #6) Settings for afl-tmin +## 7) Settings for afl-tmin Virtually nothing to play with. Well, in QEMU mode (`-Q`), `AFL_PATH` will be searched for afl-qemu-trace. In addition to this, `TMPDIR` may be used if a |