mqtt: handle POST/PUBLISH without a set POSTFIELDSIZE

Detected by OSS-Fuzz
Bug: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28735

Added test 1916 and 1917 to verify.

Closes #6338

1 files changed, 54 insertions, 0 deletions

diff --git a/tests/libtest/lib1916.c b/tests/libtest/lib1916.c
new file mode 100644
index 000000000..0d5fa78c8
--- /dev/null
+++ b/tests/libtest/lib1916.c
@@ -0,0 +1,54 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "test.h"
+
+#include "warnless.h"
+#include "memdebug.h"
+
+int test(char *URL)
+{
+  CURL *curl;
+  CURLcode res = CURLE_OK;
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, URL);
+#ifdef LIB1917
+    /* without any postfields set! */
+    curl_easy_setopt(curl, CURLOPT_POST, 1L);
+#else
+    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "");
+#endif
+    res = curl_easy_perform(curl);
+    if(res) {
+      printf("res: %d\n", res);
+    }
+    curl_easy_cleanup(curl);
+  }
+  curl_global_cleanup();
+  return (int)res;
+}