- "Tom" posted a bug report that mentioned how libcurl did wrong when doing a

POST using a read callback, with Digest authentication and
  "Transfer-Encoding: chunked" enforced.  I would then cause the first request
  to be wrongly sent and then basically hang until the server closed the
  connection. I fixed the problem and added test case 565 to verify it.

lib/http.c

@@ -2905,7 +2905,17 @@ CURLcode Curl_http(struct connectdata *conn, bool *done)
       if(result)
         return result;
 
-      if(data->set.postfieldsize) {
+      if(data->req.upload_chunky && conn->bits.authneg) {
+        /* Chunky upload is selected and we're negotiating auth still, send
+           end-of-data only */
+        result = add_buffer(req_buffer,
+                            "\x0d\x0a\x30\x0d\x0a\x0d\x0a", 7);
+        /* CR  LF   0  CR  LF  CR  LF */
+        if(result)
+          return result;
+      }
+
+      else if(data->set.postfieldsize) {
         /* set the upload size to the progress meter */
         Curl_pgrsSetUploadSize(data, postsize?postsize:-1);