Limit use of deprecated mktemp function

Author: justsmth

crypto/test/test_util.cc

@@ -97,22 +97,32 @@ size_t createTempFILEpath(char buffer[PATH_MAX]) {
   }
   return GetTempFileNameA(pathname, "awslctest", 0, buffer);
 }
+FILE* createRawTempFILE() {
+  char filename[PATH_MAX];
+  if(createTempFILEpath(filename) == 0) {
+    return nullptr;
+  }
+  return fopen(filename, "w+b");
+}
 #else
+#include <cstdlib>
 size_t createTempFILEpath(char buffer[PATH_MAX]) {
-  if(tmpnam(buffer) == nullptr) {
+  const auto pattern = "awslc.XXXXXXXXX";
+  strncpy(buffer, pattern, PATH_MAX);
+OPENSSL_BEGIN_ALLOW_DEPRECATED
+  // Functions for constructing a tempfile path (i.e., tmpname and mktemp)
+  // are deprecated in C99.
+  if(NULL == mktemp(buffer)) {
     return 0;
   }
+OPENSSL_BEGIN_ALLOW_DEPRECATED
   return strnlen(buffer, PATH_MAX);
 }
-#endif
-
 FILE* createRawTempFILE() {
-  char filename[PATH_MAX];
-  if(createTempFILEpath(filename) == 0) {
-    return nullptr;
-  }
-  return fopen(filename, "w+b");
+  return tmpfile();
 }
+#endif
+
 
 TempFILE createTempFILE() {
   return TempFILE(createRawTempFILE());