fast resume option

5 files changed, 21 insertions, 4 deletions

diff --git a/docs/env_variables.md b/docs/env_variables.md
index 22e0ce0f..6db31df0 100644
--- a/docs/env_variables.md
+++ b/docs/env_variables.md
@@ -514,6 +514,8 @@ checks or alter some of the more exotic semantics of the tool:
   - `AFL_NO_SNAPSHOT` will advise afl-fuzz not to use the snapshot feature if
     the snapshot lkm is loaded.
 
+  - `AFL_NO_FASTRESUME` will not try to read or write a fast resume file.
+
   - 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.
diff --git a/include/afl-fuzz.h b/include/afl-fuzz.h
index 3f3d6da0..6d03a74c 100644
--- a/include/afl-fuzz.h
+++ b/include/afl-fuzz.h
@@ -454,7 +454,7 @@ typedef struct afl_env_vars {
       afl_no_startup_calibration, afl_no_warn_instability,
       afl_post_process_keep_original, afl_crashing_seeds_as_new_crash,
       afl_final_sync, afl_ignore_seed_problems, afl_disable_redundant,
-      afl_sha1_filenames, afl_no_sync;
+      afl_sha1_filenames, afl_no_sync, afl_no_fastresume;
 
   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 45b080cb..928f4185 100644
--- a/include/envs.h
+++ b/include/envs.h
@@ -115,7 +115,7 @@ static char *afl_environment_variables[] = {
     "AFL_TRACE_PC", "AFL_USE_ASAN", "AFL_USE_MSAN", "AFL_USE_TRACE_PC",
     "AFL_USE_UBSAN", "AFL_USE_TSAN", "AFL_USE_CFISAN", "AFL_USE_LSAN",
     "AFL_WINE_PATH", "AFL_NO_SNAPSHOT", "AFL_EXPAND_HAVOC_NOW", "AFL_USE_FASAN",
-    "AFL_USE_QASAN", "AFL_PRINT_FILENAMES", "AFL_PIZZA_MODE", NULL
+    "AFL_USE_QASAN", "AFL_PRINT_FILENAMES", "AFL_PIZZA_MODE", "AFL_NO_FASTRESUME", NULL
 
 };
 
diff --git a/src/afl-fuzz-state.c b/src/afl-fuzz-state.c
index fbe6d32a..dd684a19 100644
--- a/src/afl-fuzz-state.c
+++ b/src/afl-fuzz-state.c
@@ -286,6 +286,13 @@ void read_afl_environment(afl_state_t *afl, char **envp) {
             afl->afl_env.afl_no_sync =
                 get_afl_env(afl_environment_variables[i]) ? 1 : 0;
 
+          } else if (!strncmp(env, "AFL_NO_FASTRESUME",
+
+                              afl_environment_variable_len)) {
+
+            afl->afl_env.afl_no_fastresume =
+                get_afl_env(afl_environment_variables[i]) ? 1 : 0;
+
           } else if (!strncmp(env, "AFL_CUSTOM_MUTATOR_ONLY",
 
                               afl_environment_variable_len)) {
diff --git a/src/afl-fuzz.c b/src/afl-fuzz.c
index d8be5721..8fd3a407 100644
--- a/src/afl-fuzz.c
+++ b/src/afl-fuzz.c
@@ -335,6 +335,7 @@ static void usage(u8 *argv0, int more_help) {
       "AFL_STATSD_PORT: change default statsd port (default: 8125)\n"
       "AFL_STATSD_TAGS_FLAVOR: set statsd tags format (default: disable tags)\n"
       "                        suported formats: dogstatsd, librato, signalfx, influxdb\n"
+      "AFL_NO_FASTRESUME: do not read or write a fast resume file\n"
       "AFL_NO_SYNC: disables all syncing\n"
       "AFL_SYNC_TIME: sync time between fuzzing instances (in minutes)\n"
       "AFL_FINAL_SYNC: sync a final time when exiting (will delay the exit!)\n"
@@ -2107,7 +2108,7 @@ int main(int argc, char **argv_orig, char **envp) {
   u64 prev_target_hash = 0;
   s32 fast_resume = 0, fr_fd = -1;
 
-  if (afl->in_place_resume) {
+  if (afl->in_place_resume && !afl->afl_env.afl_no_fastresume) {
 
     u8 fn[PATH_MAX], buf[32];
     snprintf(fn, PATH_MAX, "%s/target_hash", afl->out_dir);
@@ -2128,7 +2129,7 @@ int main(int argc, char **argv_orig, char **envp) {
 
   write_setup_file(afl, argc, argv);
 
-  if (afl->in_place_resume) {
+  if (afl->in_place_resume && !afl->afl_env.afl_no_fastresume) {
 
     u64 target_hash = get_binary_hash(afl->fsrv.target_path);
 
@@ -2166,6 +2167,10 @@ int main(int argc, char **argv_orig, char **envp) {
 
       }
 
+      // If the fast resume file is not valid we will be unable to start, so
+      // we remove the file but keep the file descriptor open.
+      unlink(fn);
+
     }
 
   }
@@ -3204,9 +3209,11 @@ stop_fuzzing:
   fclose(afl->fsrv.det_plot_file);
   #endif
 
+  if (!afl->afl_env.afl_no_fastresume) {
   /* create fastresume.bin */
   u8 fr[PATH_MAX];
   snprintf(fr, PATH_MAX, "%s/fastresume.bin", afl->out_dir);
+  ACTF("Writing %s ...", fr);
   if ((fr_fd = open(fr, O_WRONLY | O_TRUNC | O_CREAT, DEFAULT_PERMISSION)) >=
       0) {
 
@@ -3260,6 +3267,7 @@ stop_fuzzing:
     WARNF("Could not create fastresume.bin");
 
   }
+  }
 
   destroy_queue(afl);
   destroy_extras(afl);