Option for specifying forkserver initialization timeout via environment variable (#522)

* Addition of AFL_FORKSRV_INIT_TMOUT env var

This commit introduces a new environment variable which allows to
specify the timespan AFL should wait for initial contact with the
forkserver.

This is useful for fuzz-targets requiring a rather long setup time
before the actual fuzzing can be started (e.g., unicorn).

* add .swp files to .gitignore

* Inherit init_tmout in afl_fsrv_init_dup

Without this patch, the forkserver would spawn with a timeout of 0 in
cmplog mode, leading to an immediate crash.

Additionally, this commit removes a spurious whitespace.

* Initialize afl->fsrv.init_tmout in afl_fsrv_init

Not all afl-components will need the new AFL_FORKSRV_INIT_TMOUT
environment variable. Hence, it's initialized to the safe "default"
value from before in afl_fsrv_init now.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/afl-fuzz.c b/src/afl-fuzz.c
index 664cc076..ae5cb087 100644
--- a/src/afl-fuzz.c
+++ b/src/afl-fuzz.c
@@ -173,6 +173,7 @@ static void usage(u8 *argv0, int more_help) {
       "AFL_FAST_CAL: limit the calibration stage to three cycles for speedup\n"
       "AFL_FORCE_UI: force showing the status screen (for virtual consoles)\n"
       "AFL_HANG_TMOUT: override timeout value (in milliseconds)\n"
+      "AFL_FORKSRV_INIT_TMOUT: time spent waiting for forkserver during startup (in milliseconds)\n"
       "AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES: don't warn about core dump handlers\n"
       "AFL_IMPORT_FIRST: sync and import test cases from other fuzzer instances first\n"
       "AFL_MAP_SIZE: the shared memory size for that target. must be >= the size\n"
@@ -969,6 +970,22 @@ int main(int argc, char **argv_orig, char **envp) {
 
   }
 
+  if (afl->afl_env.afl_forksrv_init_tmout) {
+
+    afl->fsrv.init_tmout = atoi(afl->afl_env.afl_forksrv_init_tmout);
+    if (!afl->fsrv.init_tmout) {
+
+      FATAL("Invalid value of AFL_FORKSRV_INIT_TMOUT");
+
+    }
+
+  } else {
+
+    afl->fsrv.init_tmout = afl->fsrv.exec_tmout * FORK_WAIT_MULT;
+
+  }
+
+
   if (afl->non_instrumented_mode == 2 && afl->no_forkserver) {
 
     FATAL("AFL_DUMB_FORKSRV and AFL_NO_FORKSRV are mutually exclusive");