AFL_FORK_SERVER_KILL_SIGNAL backwards compatiblity

If `AFL_KILL_SIGNAL` is set, `AFL_FORK_SERVER_KILL_SIGNAL` is set
to the same value.

docs/env_variables.md

@@ -418,6 +418,10 @@ checks or alter some of the more exotic semantics of the tool:
     fork server when AFL++ is terminated. Unless you implement your
     fork server, you likely do not have to set it. By default, `SIGTERM`
     (`AFL_FORK_SERVER_KILL_SIGNAL=15`) will be delivered to the fork server.
+    If only `AFL_KILL_SIGNAL` is provided, `AFL_FORK_SERVER_KILL_SIGNAL` will
+    be set to same value as `AFL_KILL_SIGNAL` to provide backward compatibility.
+    If `AFL_FORK_SERVER_KILL_SIGNAL` is also set, it takes precedence.
+
     NOTE: Uncatchable signals, such as `SIGKILL`, cause child processes of
     the fork server to be orphaned and leaves them in a zombie state.
 

include/common.h

@@ -32,6 +32,7 @@
 #include <unistd.h>
 #include <sys/time.h>
 #include <stdbool.h>
+#include "forkserver.h"
 #include "types.h"
 
 /* STRINGIFY_VAL_SIZE_MAX will fit all stringify_ strings. */
@@ -73,6 +74,11 @@ u8 *find_afl_binary(u8 *own_loc, u8 *fname);
    FATALs if `numeric_signal_as_str` is not a valid integer .*/
 int parse_afl_kill_signal(u8 *numeric_signal_as_str, int default_signal);
 
+/* Configure the signals that are used to kill the forkserver
+   and the forked childs. If `afl_kill_signal_env` or `afl_fsrv_kill_signal_env`
+   is NULL, the appropiate values are read from the environment. */
+void configure_afl_kill_signals(afl_forkserver_t *fsrv, char* afl_kill_signal_env, char* afl_fsrv_kill_signal_env);
+
 /* Read a bitmap from file fname to memory
    This is for the -B option again. */
 

src/afl-analyze.c

@@ -1115,10 +1115,7 @@ int main(int argc, char **argv_orig, char **envp) {
 
   }
 
-  fsrv.child_kill_signal =
-      parse_afl_kill_signal(getenv("AFL_KILL_SIGNAL"), SIGKILL);
-  fsrv.fsrv_kill_signal =
-      parse_afl_kill_signal(getenv("AFL_FORK_SERVER_KILL_SIGNAL"), SIGTERM);
+  configure_afl_kill_signals(&fsrv, NULL, NULL);
 
 
   read_initial_file();

src/afl-common.c

@@ -25,6 +25,7 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include "forkserver.h"
 #ifndef _GNU_SOURCE
   #define _GNU_SOURCE
 #endif
@@ -47,6 +48,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <signal.h>
 
 u8  be_quiet = 0;
 u8 *doc_path = "";
@@ -476,6 +478,27 @@ int parse_afl_kill_signal(u8 *numeric_signal_as_str, int default_signal) {
   return default_signal;
 }
 
+void configure_afl_kill_signals(afl_forkserver_t *fsrv, char* afl_kill_signal_env, char* afl_fsrv_kill_signal_env) {
+  afl_kill_signal_env = afl_kill_signal_env ?
+    afl_kill_signal_env : getenv("AFL_KILL_SIGNAL");
+  afl_fsrv_kill_signal_env = afl_fsrv_kill_signal_env ?
+    afl_fsrv_kill_signal_env : getenv("AFL_FORK_SERVER_KILL_SIGNAL");
+
+  fsrv->child_kill_signal =
+      parse_afl_kill_signal(afl_kill_signal_env, SIGKILL);
+
+  if (afl_kill_signal_env && !afl_fsrv_kill_signal_env) {
+    /*
+    Set AFL_FORK_SERVER_KILL_SIGNAL to the value of AFL_KILL_SIGNAL for backwards
+    compatibility. However, if AFL_FORK_SERVER_KILL_SIGNAL is set, is takes precedence.
+    */
+    afl_fsrv_kill_signal_env = afl_kill_signal_env;
+  }
+  fsrv->fsrv_kill_signal =
+      parse_afl_kill_signal(afl_fsrv_kill_signal_env, SIGTERM);
+
+}
+
 static inline unsigned int helper_min3(unsigned int a, unsigned int b,
                                        unsigned int c) {
 

src/afl-fuzz.c

@@ -25,6 +25,7 @@
 
 #include "afl-fuzz.h"
 #include "cmplog.h"
+#include "common.h"
 #include <limits.h>
 #include <stdlib.h>
 #ifndef USEMMAP
@@ -1358,10 +1359,9 @@ int main(int argc, char **argv_orig, char **envp) {
 
   #endif
 
-  afl->fsrv.child_kill_signal =
-      parse_afl_kill_signal(afl->afl_env.afl_child_kill_signal, SIGKILL);
-  afl->fsrv.fsrv_kill_signal =
-      parse_afl_kill_signal(afl->afl_env.afl_fsrv_kill_signal, SIGTERM);
+  configure_afl_kill_signals(&afl->fsrv,
+    afl->afl_env.afl_child_kill_signal,
+    afl->afl_env.afl_fsrv_kill_signal);
 
   setup_signal_handlers();
   check_asan_opts(afl);

src/afl-showmap.c

@@ -1260,10 +1260,7 @@ int main(int argc, char **argv_orig, char **envp) {
                                  : 0);
     be_quiet = save_be_quiet;
 
-    fsrv->child_kill_signal =
-        parse_afl_kill_signal(getenv("AFL_KILL_SIGNAL"), SIGKILL);
-    fsrv->fsrv_kill_signal =
-        parse_afl_kill_signal(getenv("AFL_FORK_SERVER_KILL_SIGNAL"), SIGTERM);
+    configure_afl_kill_signals(fsrv, NULL, NULL);
 
     if (new_map_size) {
 

src/afl-tmin.c

@@ -1197,10 +1197,7 @@ int main(int argc, char **argv_orig, char **envp) {
 
   }
 
-  fsrv->child_kill_signal =
-      parse_afl_kill_signal(getenv("AFL_KILL_SIGNAL"), SIGKILL);
-  fsrv->fsrv_kill_signal =
-      parse_afl_kill_signal(getenv("AFL_FORK_SERVER_KILL_SIGNAL"), SIGTERM);
+  configure_afl_kill_signals(fsrv, NULL, NULL);
 
 
   if (getenv("AFL_CRASH_EXITCODE")) {