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Diffstat (limited to 'docs/env_variables.md')
| -rw-r--r-- | docs/env_variables.md | 33 |
1 files changed, 31 insertions, 2 deletions
diff --git a/docs/env_variables.md b/docs/env_variables.md index a36f2b4e..e203055f 100644 --- a/docs/env_variables.md +++ b/docs/env_variables.md @@ -55,7 +55,7 @@ make fairly broad use of environmental variables instead: in your `$PATH`. - `AFL_PATH` can be used to point afl-gcc to an alternate location of afl-as. - One possible use of this is examples/clang_asm_normalize/, which lets + One possible use of this is utils/clang_asm_normalize/, which lets you instrument hand-written assembly when compiling clang code by plugging a normalizer into the chain. (There is no equivalent feature for GCC.) @@ -294,6 +294,9 @@ checks or alter some of the more exotic semantics of the tool: on Linux systems. This slows things down, but lets you run more instances of afl-fuzz than would be prudent (if you really want to). + - Setting `AFL_NO_AUTODICT` will not load an LTO generated auto dictionary + that is compiled into the target. + - `AFL_SKIP_CRASHES` causes AFL++ to tolerate crashing files in the input queue. This can help with rare situations where a program crashes only intermittently, but it's not really recommended under normal operating @@ -306,6 +309,14 @@ checks or alter some of the more exotic semantics of the tool: don't want AFL++ to spend too much time classifying that stuff and just rapidly put all timeouts in that bin. + - Setting `AFL_FORKSRV_INIT_TMOUT` allows you to specify a different timeout + to wait for the forkserver to spin up. The default is the `-t` value times + `FORK_WAIT_MULT` from `config.h` (usually 10), so for a `-t 100`, the + default would wait for `1000` milliseconds. Setting a different time here is useful + if the target has a very slow startup time, for example when doing + full-system fuzzing or emulation, but you don't want the actual runs + to wait too long for timeouts. + - `AFL_NO_ARITH` causes AFL++ to skip most of the deterministic arithmetics. This can be useful to speed up the fuzzing of text-based file formats. @@ -380,8 +391,12 @@ checks or alter some of the more exotic semantics of the tool: processing the first queue entry; and `AFL_BENCH_UNTIL_CRASH` causes it to exit soon after the first crash is found. - - Setting `AFL_DEBUG_CHILD_OUTPUT` will not suppress the child output. + - Setting `AFL_DEBUG_CHILD` will not suppress the child output. + This lets you see all output of the child, making setup issues obvious. + For example, in an unicornafl harness, you might see python stacktraces. + You may also see other logs that way, indicating why the forkserver won't start. Not pretty but good for debugging purposes. + Note that `AFL_DEBUG_CHILD_OUTPUT` is deprecated. - Setting `AFL_NO_CPU_RED` will not display very high cpu usages in red color. @@ -389,6 +404,13 @@ checks or alter some of the more exotic semantics of the tool: for an existing out folder, even if a different `-i` was provided. Without this setting, afl-fuzz will refuse execution for a long-fuzzed out dir. + - Setting `AFL_MAX_DET_EXRAS` will change the threshold at what number of elements + in the `-x` dictionary and LTO autodict (combined) the probabilistic mode will + kick off. In probabilistic mode not all dictionary entires will be used all + of the times for fuzzing mutations to not slow down fuzzing. + The default count is `200` elements. So for the 200 + 1st element, there is a + 1 in 201 chance, that one of the dictionary entries will not be used directly. + - Setting `AFL_NO_FORKSRV` disables the forkserver optimization, reverting to fork + execve() call for every tested input. This is useful mostly when working with unruly libraries that create threads or do other crazy @@ -406,6 +428,13 @@ checks or alter some of the more exotic semantics of the tool: matches your StatsD server. Available flavors are `dogstatsd`, `librato`, `signalfx` and `influxdb`. + - Setting `AFL_CRASH_EXITCODE` sets the exit code afl treats as crash. + For example, if `AFL_CRASH_EXITCODE='-1'` is set, each input resulting + in an `-1` return code (i.e. `exit(-1)` got called), will be treated + as if a crash had ocurred. + This may be beneficial if you look for higher-level faulty conditions in which your + target still exits gracefully. + - Outdated environment variables that are not supported anymore: `AFL_DEFER_FORKSRV` `AFL_PERSISTENT` |