[binutils] Use mkstemp in binutils fuzz target (#3508)

* Use mkstemp in binutils fuzz target

* Adding License

* Remove file and do not abort

projects/binutils/fuzz_bfd.c

@@ -1,28 +1,37 @@
+/* Copyright 2020 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 #include "sysdep.h"
 #include "bfd.h"
 
 #include <stdint.h>
 #include <stdio.h>
+#include <unistd.h>
 
-
-static int bufferToFile(const char * name, const uint8_t *Data, size_t Size) {
-    FILE * fd;
-    if (remove(name) != 0) {
-        if (errno != ENOENT) {
-            printf("failed remove, errno=%d\n", errno);
-            return -1;
-        }
-    }
-    fd = fopen(name, "wb");
-    if (fd == NULL) {
-        printf("failed open, errno=%d\n", errno);
+static int bufferToFile(char * name, const uint8_t *Data, size_t Size) {
+    int fd = mkstemp(name);
+    if (fd < 0) {
+        printf("failed mkstemp, errno=%d\n", errno);
         return -2;
     }
-    if (fwrite (Data, 1, Size, fd) != Size) {
-        fclose(fd);
+    if (write (fd, Data, Size) != Size) {
+        printf("failed write, errno=%d\n", errno);
+        close(fd);
         return -3;
     }
-    fclose(fd);
+    close(fd);
     return 0;
 }
 
@@ -31,6 +40,7 @@ static int initialized = 0;
 char *target = NULL;
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+    char tmpfilename[32];
     if (initialized == 0) {
         if (bfd_init () != BFD_INIT_MAGIC) {
             abort();
@@ -38,17 +48,20 @@ int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
         initialized = 1;
     }
 
-    if (bufferToFile("/tmp/fuzz.bfd", Data, Size) < 0) {
-        abort();
+    strncpy(tmpfilename, "/tmp/fuzz.bfd-XXXXXX", 31);
+    if (bufferToFile(tmpfilename, Data, Size) < 0) {
+        return 0;
     }
-    bfd *file = bfd_openr ("/tmp/fuzz.bfd", target);
+    bfd *file = bfd_openr (tmpfilename, target);
     if (file == NULL)
     {
+        remove(tmpfilename);
         return 0;
     }
     bfd_check_format (file, bfd_archive);
     //TODO loop over subfiles and more processing
     bfd_close (file);
+    remove(tmpfilename);
 
     return 0;
 }