- Fix #1288: [FR] Improve fuzzing of unbound by adapting the netbound

program.

doc/Changelog

@@ -1,3 +1,7 @@
+21 May 2025: Wouter
+	- Fix #1288: [FR] Improve fuzzing of unbound by adapting the netbound
+	  program.
+
 20 May 2025: Yorgos
 	- Merge #1285:  RST man pages. It introduces restructuredText man pages
 	  to sync the online and source code man page documentation.

testcode/fake_event.c

@@ -900,8 +900,10 @@ run_scenario(struct replay_runtime* runtime)
 			runtime->now->evt_type == repevt_front_reply) {
 			answer_check_it(runtime);
 			advance_moment(runtime);
-		} else if(pending_matches_range(runtime, &entry, &pending)) {
-			answer_callback_from_entry(runtime, entry, pending);
+		} else if(runtime->now && pending_matches_range(runtime,
+			&entry, &pending)) {
+			if(entry)
+				answer_callback_from_entry(runtime, entry, pending);
 		} else {
 			do_moment_and_advance(runtime);
 		}
@@ -1274,7 +1276,7 @@ struct serviced_query* outnet_serviced_query(struct outside_network* outnet,
 		(flags&~(BIT_RD|BIT_CD))?" MORE":"", (dnssec)?" DO":"");
 
 	/* create packet with EDNS */
-	pend->buffer = sldns_buffer_new(512);
+	pend->buffer = sldns_buffer_new(4096);
 	log_assert(pend->buffer);
 	sldns_buffer_write_u16(pend->buffer, 0); /* id */
 	sldns_buffer_write_u16(pend->buffer, flags);
@@ -1334,7 +1336,13 @@ struct serviced_query* outnet_serviced_query(struct outside_network* outnet,
 		edns.opt_list_in = NULL;
 		edns.opt_list_out = per_upstream_opt_list;
 		edns.opt_list_inplace_cb_out = NULL;
-		attach_edns_record(pend->buffer, &edns);
+		if(sldns_buffer_capacity(pend->buffer) >=
+			sldns_buffer_limit(pend->buffer)
+			+calc_edns_field_size(&edns)) {
+			attach_edns_record(pend->buffer, &edns);
+		} else {
+			verbose(VERB_ALGO, "edns field too large to fit");
+		}
 	}
 	memcpy(&pend->addr, addr, addrlen);
 	pend->addrlen = addrlen;

testcode/replay.c

@@ -795,7 +795,7 @@ macro_expand(rbtree_type* store, struct replay_runtime* runtime, char** text)
 	char buf[10240];
 	char* at = *text;
 	size_t len = macro_length(at);
-	int dofunc = 0;
+	int tries = 0, dofunc = 0;
 	char* arithstart = NULL;
 	if(len >= sizeof(buf))
 		return NULL; /* too long */
@@ -834,6 +834,8 @@ macro_expand(rbtree_type* store, struct replay_runtime* runtime, char** text)
 	/* actual macro text expansion */
 	while(*at) {
 		size_t remain = sizeof(buf)-strlen(buf);
+		if(tries++ > 10000)
+			return NULL; /* looks like got into an infinite loop, bail out */
 		if(strncmp(at, "${", 2) == 0) {
 			at = do_macro_recursion(store, runtime, at, remain);
 		} else if(*at == '$') {

testcode/testbound.c

@@ -339,6 +339,35 @@ static void remove_configfile(void)
 	cfgfiles = NULL;
 }
 
+/** perform the playback on the playback_file with the args. */
+static int
+perform_playback(char* playback_file, int pass_argc, char** pass_argv)
+{
+	struct replay_scenario* scen = NULL;
+	int c, res;
+
+	/* setup test environment */
+	scen = setup_playback(playback_file, &pass_argc, pass_argv);
+	/* init fake event backend */
+	fake_event_init(scen);
+
+	pass_argv[pass_argc] = NULL;
+	echo_cmdline(pass_argc, pass_argv);
+
+	/* run the normal daemon */
+	res = daemon_main(pass_argc, pass_argv);
+
+	fake_event_cleanup();
+	for(c=1; c<pass_argc; c++)
+		free(pass_argv[c]);
+	return res;
+}
+
+/* For fuzzing the main routine is replaced with
+ * LLVMFuzzerTestOneInput. */
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#define main dummy_main
+#endif
 /**
  * Main fake event test program. Setup, teardown and report errors.
  * @param argc: arg count.
@@ -354,7 +383,6 @@ main(int argc, char* argv[])
 	char* playback_file = NULL;
 	int init_optind = optind;
 	char* init_optarg = optarg;
-	struct replay_scenario* scen = NULL;
 
 	/* we do not want the test to depend on the timezone */
 	(void)putenv("TZ=UTC");
@@ -462,24 +490,11 @@ main(int argc, char* argv[])
 	if(atexit(&remove_configfile) != 0)
 		fatal_exit("atexit() failed: %s", strerror(errno));
 
-	/* setup test environment */
-	scen = setup_playback(playback_file, &pass_argc, pass_argv);
-	/* init fake event backend */
-	fake_event_init(scen);
-
-	pass_argv[pass_argc] = NULL;
-	echo_cmdline(pass_argc, pass_argv);
-
 	/* reset getopt processing */
 	optind = init_optind;
 	optarg = init_optarg;
 
-	/* run the normal daemon */
-	res = daemon_main(pass_argc, pass_argv);
-
-	fake_event_cleanup();
-	for(c=1; c<pass_argc; c++)
-		free(pass_argv[c]);
+	res = perform_playback(playback_file, pass_argc, pass_argv);
 	if(res == 0) {
 		log_info("Testbound Exit Success\n");
 		/* remove configfile from here, the atexit() is for when
@@ -499,6 +514,101 @@ main(int argc, char* argv[])
 	return res;
 }
 
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+static int delete_file(const char *pathname) {
+  int ret = unlink(pathname);
+  free((void *)pathname);
+  return ret;
+}
+
+static char *buf_to_file(const uint8_t *buf, size_t size) {
+  int fd;
+  size_t pos;
+  char *pathname = strdup("/tmp/fuzz-XXXXXX");
+  if (pathname == NULL)
+    return NULL;
+
+  fd = mkstemp(pathname);
+  if (fd == -1) {
+    log_err("mkstemp of file %s failed: %s", pathname, strerror(errno));
+    free(pathname);
+    return NULL;
+  }
+  pos = 0;
+  while (pos < size) {
+    int nbytes = write(fd, &buf[pos], size - pos);
+    if (nbytes <= 0) {
+      if (nbytes == -1 && errno == EINTR)
+             continue;
+      log_err("write to file %s failed: %s", pathname, strerror(errno));
+      goto err;
+    }
+    pos += nbytes;
+  }
+
+  if (close(fd) == -1) {
+    log_err("close of file %s failed: %s", pathname, strerror(errno));
+    goto err;
+  }
+
+  return pathname;
+err:
+  delete_file(pathname);
+  return NULL;
+}
+
+/* based on main() above, but with: hard-coded passed args, file created from fuzz input */
+int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
+{
+       int c, res;
+       int pass_argc = 0;
+       char* pass_argv[MAXARG];
+       char* playback_file = NULL;
+
+       /* we do not want the test to depend on the timezone */
+       (void)putenv("TZ=UTC");
+       memset(pass_argv, 0, sizeof(pass_argv));
+#ifdef HAVE_SYSTEMD
+       /* we do not want the test to use systemd daemon startup notification*/
+       (void)unsetenv("NOTIFY_SOCKET");
+#endif /* HAVE_SYSTEMD */
+
+       checklock_start();
+       log_init(NULL, 0, NULL);
+       /* determine commandline options for the daemon */
+       pass_argc = 1;
+       pass_argv[0] = "unbound";
+       add_opts("-d", &pass_argc, pass_argv);
+
+       playback_file = buf_to_file(Data, Size);
+       if (playback_file) {
+               log_info("Start of %s testbound program.", PACKAGE_STRING);
+
+               res = perform_playback(playback_file, pass_argc, pass_argv);
+               if(res == 0) {
+                       log_info("Testbound Exit Success\n");
+                       /* remove configfile from here, the atexit() is for when
+                        * there is a crash to remove the tmpdir file.
+                        * This one removes the file while alloc and log locks are
+                        * still valid, and can be logged (for memory calculation),
+                        * it leaves the ptr NULL so the atexit does nothing. */
+                       remove_configfile();
+#ifdef HAVE_PTHREAD
+                       /* dlopen frees its thread state (dlopen of gost engine) */
+                       pthread_exit(NULL);
+#endif
+               }
+
+               delete_file(playback_file);
+       }
+
+       if(log_get_lock()) {
+               lock_basic_destroy((lock_basic_type*)log_get_lock());
+       }
+       return res;
+}
+#endif /* FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION */
+
 /* fake remote control */
 struct listen_port* daemon_remote_open_ports(struct config_file* 
 	ATTR_UNUSED(cfg))

testcode/testpkts.c

@@ -923,10 +923,14 @@ pkt_snip_edns_option(uint8_t* pkt, size_t len, sldns_edns_option code,
 	if(!pkt_find_edns_opt(&opt_position, &remaining)) return 0;
 	if(remaining < 8) return -1; /* malformed */
 	rdlen = sldns_read_uint16(opt_position+6);
+	if(remaining < ((size_t)rdlen)+8)
+		return -1; /* malformed */
 	rdata = opt_position + 8;
 	while(rdlen > 0) {
 		if(rdlen < 4) return -1; /* malformed */
 		optlen = sldns_read_uint16(rdata+2);
+		if((size_t)rdlen < 4+((size_t)optlen))
+			return -1; /* malformed */
 		if(sldns_read_uint16(rdata) == code) {
 			/* save data to buf for caller inspection */
 			memmove(buf, rdata+4, optlen);
@@ -1134,8 +1138,9 @@ static void lowercase_dname(uint8_t** p, size_t* remain)
 	while(**p != 0) {
 		/* compressed? */
 		if((**p & 0xc0) == 0xc0) {
-			*p += 2;
-			*remain -= 2;
+			llen = *remain < 2 ? (unsigned int)*remain : 2;
+			*p += llen;
+			*remain -= llen;
 			return;
 		}
 		llen = (unsigned int)**p;
@@ -1178,6 +1183,12 @@ static void lowercase_rdata(uint8_t** p, size_t* remain,
 			uint8_t len;
 			if(rdataremain == 0) return;
 			len = **p;
+			if(rdataremain < ((size_t)len)+1) {
+				/* malformed LDNS_RDF_TYPE_STR, skip remainder */
+				*p += rdataremain;
+				*remain -= rdatalen;
+				return;
+			}
 			*p += len+1;
 			rdataremain -= len+1;
 		} else {
@@ -1207,6 +1218,12 @@ static void lowercase_rdata(uint8_t** p, size_t* remain,
 				break;
 			default: error("bad rdf type in lowercase %d", (int)f);
 			}
+			if (rdataremain < (size_t)len) {
+				/* malformed RDF, skip remainder */
+				*p += rdataremain;
+				*remain -= rdatalen;
+				return;
+			}
 			*p += len;
 			rdataremain -= len;
 		}

util/random.c

@@ -78,6 +78,37 @@
  */
 #define MAX_VALUE 0x7fffffff
 
+/* If the build mode is for fuzzing this removes randomness from the output.
+ * This helps fuzz engines from having state increase due to the randomness. */
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+struct ub_randstate {
+       unsigned int dummy;
+};
+
+struct ub_randstate* ub_initstate(struct ub_randstate* ATTR_UNUSED(from))
+{
+       struct ub_randstate* s = (struct ub_randstate*)calloc(1, sizeof(*s));
+       if(!s) {
+               log_err("malloc failure in random init");
+               return NULL;
+       }
+       return s;
+}
+
+long int ub_random(struct ub_randstate* state)
+{
+       state->dummy++;
+       return (long int)(state->dummy & MAX_VALUE);
+}
+
+long int
+ub_random_max(struct ub_randstate* state, long int x)
+{
+       state->dummy++;
+       return ((long int)state->dummy % x);
+}
+#else /* !FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION */
+
 #if defined(HAVE_SSL) || defined(HAVE_LIBBSD)
 struct ub_randstate* 
 ub_initstate(struct ub_randstate* ATTR_UNUSED(from))
@@ -200,6 +231,8 @@ ub_random_max(struct ub_randstate* state, long int x)
 }
 #endif /* HAVE_NSS or HAVE_NETTLE and !HAVE_LIBBSD */
 
+#endif /* FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION */
+
 void 
 ub_randfree(struct ub_randstate* s)
 {