Add new fuzzer for robots.txt parsing

* fuzz/Makefile.am: Add wget_robots_fuzzer
* fuzz/wget_robots_fuzzer.c: New fuzzer
* fuzz/wget_robots_fuzzer.in: Initial corpora

fuzz/wget_robots_fuzzer.c

@@ -0,0 +1,97 @@
+/*
+ * Copyright(c) 2017-2018 Free Software Foundation, Inc.
+ *
+ * This file is part of GNU Wget.
+ *
+ * GNU Wget is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GNU Wget is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Wget.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+
+#include <sys/types.h>
+#include <dirent.h> // opendir, readdir
+#include <stdint.h> // uint8_t
+#include <stdio.h>  // fmemopen
+#include <string.h>  // strncmp
+#include <stdlib.h>  // free
+#include <fcntl.h>  // open flags
+#include <unistd.h>  // close
+#include <setjmp.h> // longjmp, setjmp
+
+#include "wget.h"
+#undef fopen_wgetrc
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+  #include "res.h"
+
+  // declarations for wget internal functions
+  int main_wget(int argc, const char **argv);
+  void cleanup(void);
+  FILE *fopen_wget(const char *pathname, const char *mode);
+  FILE *fopen_wgetrc(const char *pathname, const char *mode);
+  void exit_wget(int status);
+#ifdef __cplusplus
+  }
+#endif
+
+#include "fuzzer.h"
+
+FILE *fopen_wget(const char *pathname, const char *mode)
+{
+	return fopen("/dev/null", mode);
+}
+
+FILE *fopen_wgetrc(const char *pathname, const char *mode)
+{
+	return NULL;
+}
+
+#ifdef FUZZING
+void exit_wget(int status)
+{
+}
+#else
+void exit(int status)
+{
+}
+#endif
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	FILE *fp, *bak;
+	struct robot_specs *specs;
+
+	if (size > 4096) // same as max_len = ... in .options file
+		return 0;
+
+	bak = stderr;
+	stderr = fopen("/dev/null", "w");
+
+	specs = res_parse((char *) data, (int) size);
+	if (!specs)
+		return 0;
+
+	res_match_path(specs, "a%ff%a");
+
+	res_register_specs("host", 80, specs);
+
+	res_cleanup();
+
+	fclose(stderr);
+	stderr = bak;
+
+	return 0;
+}