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Diffstat (limited to 'docs/env_variables.md')
| -rw-r--r-- | docs/env_variables.md | 36 |
1 files changed, 34 insertions, 2 deletions
diff --git a/docs/env_variables.md b/docs/env_variables.md index 41733f1b..de6b4bd8 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 @@ -18,11 +22,21 @@ 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: + - Some build/configure scripts break with afl++ compilers. To be able to + pass them, do: +``` + export CC=afl-cc + export CXX=afl-c++ + export AFL_NOOPT=1 + ./configure --disable-shared --disabler-werror + unset AFL_NOOPT + make +``` + - Most afl tools do not print any output if stdout/stderr are redirected. If you want to get the output into a file then set the `AFL_DEBUG` environment variable. @@ -379,6 +393,10 @@ checks or alter some of the more exotic semantics of the tool: - In QEMU mode (-Q), `AFL_PATH` will be searched for afl-qemu-trace. + - In QEMU mode (-Q), setting `AFL_QEMU_CUSTOM_BIN` cause afl-fuzz to skip + prepending `afl-qemu-trace` to your command line. Use this if you wish to use a + custom afl-qemu-trace or if you need to modify the afl-qemu-trace arguments. + - Setting `AFL_CYCLE_SCHEDULES` will switch to a different schedule everytime a cycle is finished. @@ -390,6 +408,12 @@ checks or alter some of the more exotic semantics of the tool: without disrupting the afl-fuzz process itself. This is useful, among other things, for bootstrapping libdislocator.so. + - Setting `AFL_TARGET_ENV` causes AFL++ to set extra environment variables + for the target binary. Example: `AFL_TARGET_ENV="VAR1=1 VAR2='a b c'" afl-fuzz ... ` + This exists mostly for things like `LD_LIBRARY_PATH` but it would theoretically + allow fuzzing of AFL++ itself (with 'target' AFL++ using some AFL_ vars that + would disrupt work of 'fuzzer' AFL++). + - Setting `AFL_NO_UI` inhibits the UI altogether, and just periodically prints some basic stats. This behavior is also automatically triggered when the output from afl-fuzz is redirected to a file or to a pipe. @@ -410,7 +434,8 @@ checks or alter some of the more exotic semantics of the tool: and RECORD:000000,cnt:000009 being the crash case. - If you are Jakub, you may need `AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES`. - Others need not apply. + Others need not apply, unless they also want to disable the + `/proc/sys/kernel/core_pattern` check. - Benchmarking only: `AFL_BENCH_JUST_ONE` causes the fuzzer to exit after processing the first queue entry; and `AFL_BENCH_UNTIL_CRASH` causes it to @@ -457,6 +482,7 @@ checks or alter some of the more exotic semantics of the tool: `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. + See [rpc_statsd.md](rpc_statsd.md) for more information. - Setting `AFL_CRASH_EXITCODE` sets the exit code afl treats as crash. For example, if `AFL_CRASH_EXITCODE='-1'` is set, each input resulting @@ -523,6 +549,12 @@ 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: |