mime: clone mime tree upon easy handle duplication.

A mime tree attached to an easy handle using CURLOPT_MIMEPOST is
strongly bound to the handle: there is a pointer to the easy handle in
each item of the mime tree and following the parent pointer list
of mime items ends in a dummy part stored within the handle.

Because of this binding, a mime tree cannot be shared between different
easy handles, thus it needs to be cloned upon easy handle duplication.

There is no way for the caller to get the duplicated mime tree
handle: it is then set to be automatically destroyed upon freeing the
new easy handle.

New test 654 checks proper mime structure duplication/release.

Add a warning note in curl_mime_data_cb() documentation about sharing
user data between duplicated handles.

Closes #2235

2 files changed, 178 insertions, 1 deletions

diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 9e1ba28a9..d8a55e21d 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -20,7 +20,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib559 lib560 lib562 lib564 lib565 lib566 lib567 lib568 lib569 lib570   \
  lib571 lib572 lib573 lib574 lib575 lib576        lib578 lib579 lib582   \
  lib583 lib585 lib586 lib587 lib589 lib590 lib591 lib597 lib598 lib599   \
- lib643 lib644 lib645 lib650 lib651 lib652 lib653 \
+ lib643 lib644 lib645 lib650 lib651 lib652 lib653 lib654 \
  lib1500 lib1501 lib1502 lib1503 lib1504 lib1505 lib1506 lib1507 lib1508 \
  lib1509 lib1510 lib1511 lib1512 lib1513 lib1514 lib1515         lib1517 \
  lib1520 lib1521 \
@@ -324,6 +324,9 @@ lib652_CPPFLAGS = $(AM_CPPFLAGS)
 lib653_SOURCES = lib653.c $(SUPPORTFILES)
 lib653_CPPFLAGS = $(AM_CPPFLAGS)
 
+lib654_SOURCES = lib654.c $(SUPPORTFILES)
+lib654_CPPFLAGS = $(AM_CPPFLAGS)
+
 lib1500_SOURCES = lib1500.c $(SUPPORTFILES) $(TESTUTIL)
 lib1500_LDADD = $(TESTUTIL_LIBS)
 lib1500_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/libtest/lib654.c b/tests/libtest/lib654.c
new file mode 100644
index 000000000..45051a9c7
--- /dev/null
+++ b/tests/libtest/lib654.c
@@ -0,0 +1,174 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2018, 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.haxx.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 "memdebug.h"
+
+static char data[]=
+#ifdef CURL_DOES_CONVERSIONS
+  /* ASCII representation with escape sequences for non-ASCII platforms */
+  "\x74\x68\x69\x73\x20\x69\x73\x20\x77\x68\x61\x74\x20\x77\x65\x20\x70"
+  "\x6f\x73\x74\x20\x74\x6f\x20\x74\x68\x65\x20\x73\x69\x6c\x6c\x79\x20"
+  "\x77\x65\x62\x20\x73\x65\x72\x76\x65\x72\x0a";
+#else
+  "this is what we post to the silly web server\n";
+#endif
+
+struct WriteThis {
+  char *readptr;
+  curl_off_t sizeleft;
+  int freecount;
+};
+
+static void free_callback(void *userp)
+{
+  struct WriteThis *pooh = (struct WriteThis *) userp;
+
+  pooh->freecount++;
+}
+
+static size_t read_callback(char *ptr, size_t size, size_t nmemb, void *userp)
+{
+  struct WriteThis *pooh = (struct WriteThis *)userp;
+  int eof = !*pooh->readptr;
+
+  if(size*nmemb < 1)
+    return 0;
+
+  eof = pooh->sizeleft <= 0;
+  if(!eof)
+    pooh->sizeleft--;
+
+  if(!eof) {
+    *ptr = *pooh->readptr;           /* copy one single byte */
+    pooh->readptr++;                 /* advance pointer */
+    return 1;                        /* we return 1 byte at a time! */
+  }
+
+  return 0;                         /* no more data left to deliver */
+}
+
+int test(char *URL)
+{
+  CURL *easy = NULL;
+  CURL *easy2 = NULL;
+  curl_mime *mime = NULL;
+  curl_mimepart *part;
+  struct curl_slist *hdrs = NULL;
+  CURLcode result;
+  int res = TEST_ERR_FAILURE;
+  struct WriteThis pooh;
+
+  /*
+   * Check proper copy/release of mime post data bound to a duplicated
+   * easy handle.
+   */
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  easy = curl_easy_init();
+
+  /* First set the URL that is about to receive our POST. */
+  test_setopt(easy, CURLOPT_URL, URL);
+
+  /* get verbose debug output please */
+  test_setopt(easy, CURLOPT_VERBOSE, 1L);
+
+  /* include headers in the output */
+  test_setopt(easy, CURLOPT_HEADER, 1L);
+
+  /* Prepare the callback structure. */
+  pooh.readptr = data;
+  pooh.sizeleft = (curl_off_t) strlen(data);
+  pooh.freecount = 0;
+
+  /* Build the mime tree. */
+  mime = curl_mime_init(easy);
+  part = curl_mime_addpart(mime);
+  curl_mime_data(part, "hello", CURL_ZERO_TERMINATED);
+  curl_mime_name(part, "greeting");
+  curl_mime_type(part, "application/X-Greeting");
+  curl_mime_encoder(part, "base64");
+  hdrs = curl_slist_append(hdrs, "X-Test-Number: 654");
+  curl_mime_headers(part, hdrs, TRUE);
+  part = curl_mime_addpart(mime);
+  curl_mime_filedata(part, "log/file654.txt");
+  part = curl_mime_addpart(mime);
+  curl_mime_data_cb(part, (curl_off_t) -1, read_callback, NULL, free_callback,
+                    &pooh);
+
+  /* Bind mime data to its easy handle. */
+  test_setopt(easy, CURLOPT_MIMEPOST, mime);
+
+  /* Duplicate the handle. */
+  easy2 = curl_easy_duphandle(easy);
+  if(!easy2) {
+    fprintf(stderr, "curl_easy_duphandle() failed\n");
+    res = TEST_ERR_FAILURE;
+    goto test_cleanup;
+  }
+
+  /* Now free the mime structure: it should unbind it from the first
+     easy handle. */
+  curl_mime_free(mime);
+  mime = NULL;  /* Already cleaned up. */
+
+  /* Perform on the first handle: should not send any data. */
+  result = curl_easy_perform(easy);
+  if(result) {
+    fprintf(stderr, "curl_easy_perform(original) failed\n");
+    res = (int) result;
+    goto test_cleanup;
+  }
+
+  /* Perform on the second handle: if the bound mime structure has not been
+     duplicated properly, it should cause a valgrind error. */
+  result = curl_easy_perform(easy2);
+  if(result) {
+    fprintf(stderr, "curl_easy_perform(duplicated) failed\n");
+    res = (int) result;
+    goto test_cleanup;
+  }
+
+  /* Free the duplicated handle: it should call free_callback again.
+     If the mime copy was bad or not automatically released, valgrind
+     will signal it. */
+  curl_easy_cleanup(easy2);
+  easy2 = NULL;  /* Already cleaned up. */
+
+  if(pooh.freecount != 2) {
+    fprintf(stderr, "free_callback() called %d times instead of 2\n",
+            pooh.freecount);
+    res = TEST_ERR_FAILURE;
+    goto test_cleanup;
+  }
+
+test_cleanup:
+  curl_easy_cleanup(easy);
+  curl_easy_cleanup(easy2);
+  curl_mime_free(mime);
+  curl_global_cleanup();
+  return res;
+}