mime: explicitly rewind subparts at attachment time.

Subparts may have been previously used as a top-level mime structure and
thus not rewound.

New test 695 checks the proper functioning in these particular conditions.

Reported-by: Qriist on github
Fixes #15842
Closes #15911

lib/mime.c

@@ -1561,6 +1561,14 @@ CURLcode Curl_mime_set_subparts(curl_mimepart *part,
       }
     }
 
+    /* If subparts have already been used as a top-level MIMEPOST,
+       they might not be positioned at start. Rewind them now, as
+       a future check while rewinding the parent may cause this
+       content to be skipped. */
+    if(mime_subparts_seek(subparts, (curl_off_t) 0, SEEK_SET) !=
+       CURL_SEEKFUNC_OK)
+      return CURLE_SEND_FAIL_REWIND;
+
     subparts->parent = part;
     /* Subparts are processed internally: no read callback. */
     part->seekfunc = mime_subparts_seek;

tests/data/Makefile.am

@@ -101,7 +101,7 @@ test652 test653 test654 test655 test656 test658 test659 test660 test661 \
 test662 test663 test664 test665 test666 test667 test668 test669 test670 \
 test671 test672 test673 test674 test675 test676 test677 test678 test679 \
 test680 test681 test682 test683 test684 test685 test686 test687 test688 \
-test689 test690 test691 test692 test693 test694 \
+test689 test690 test691 test692 test693 test694 test695 \
 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \
 test709 test710 test711 test712 test713 test714 test715 test716 test717 \

tests/data/test695

@@ -0,0 +1,78 @@
+<testcase>
+<info>
+<keywords>
+MIME
+</keywords>
+</info>
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.0 200 OK swsclose
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+
+blablabla
+
+</data>
+</reply>
+
+# Client-side
+<client>
+<features>
+Mime
+</features>
+<server>
+http
+</server>
+<tool>
+lib%TESTNUMBER
+</tool>
+
+<name>
+MIME parts reuse as a child part
+</name>
+<command>
+http://%HOSTIP:%HTTPPORT/we/want/%TESTNUMBER
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/^--------------------------[A-Za-z0-9]*/------------------------------/
+s/boundary=------------------------[A-Za-z0-9]*/boundary=----------------------------/
+</strippart>
+<protocol>
+POST /we/want/%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+Content-Length: 196
+Content-Type: multipart/form-data; boundary=----------------------------
+
+------------------------------
+Content-Disposition: form-data; name="data"
+Content-Type: text/html
+
+<title>hello</title>
+--------------------------------
+POST /we/want/%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+Content-Length: 423
+Content-Type: multipart/form-data; boundary=----------------------------
+
+------------------------------
+Content-Disposition: form-data
+Content-Type: multipart/mixed; boundary=----------------------------
+
+------------------------------
+Content-Disposition: attachment; name="data"
+Content-Type: text/html
+
+<title>hello</title>
+--------------------------------
+
+--------------------------------
+</protocol>
+</verify>
+</testcase>

tests/libtest/Makefile.inc

@@ -48,7 +48,7 @@ LIBTESTPROGS = libauthretry libntlmconnect libprereq                     \
  lib599 \
  lib643        lib645 lib650 lib651 lib652 lib653 lib654 lib655 lib658   \
  lib659 lib661 lib666 lib667 lib668 \
- lib670 lib671 lib672 lib673 lib674 lib676 lib677 lib678 lib694 \
+ lib670 lib671 lib672 lib673 lib674 lib676 lib677 lib678 lib694 lib695   \
  lib1156 \
  lib1301 \
  lib1485 \
@@ -340,6 +340,8 @@ lib678_LDADD = $(TESTUTIL_LIBS)
 
 lib694_SOURCES = lib694.c $(SUPPORTFILES)
 
+lib695_SOURCES = lib695.c $(SUPPORTFILES)
+
 lib1301_SOURCES = lib1301.c $(SUPPORTFILES) $(TESTUTIL)
 lib1301_LDADD = $(TESTUTIL_LIBS)
 

tests/libtest/lib695.c

@@ -0,0 +1,115 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 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.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "test.h"
+
+#include "memdebug.h"
+
+
+/* write callback that does nothing */
+static size_t write_it(char *ptr, size_t size, size_t nmemb, void *userdata)
+{
+  (void) ptr;
+  (void) userdata;
+  return size * nmemb;
+}
+
+CURLcode test(char *URL)
+{
+  CURL *curl = NULL;
+  curl_mime *mime1 = NULL;
+  curl_mime *mime2 = NULL;
+  curl_mimepart *part;
+  CURLcode res = TEST_ERR_FAILURE;
+
+  /*
+   * Check proper rewind when reusing a mime structure.
+   */
+
+  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();
+
+  /* First set the URL that is about to receive our POST. */
+  test_setopt(curl, CURLOPT_URL, URL);
+
+  /* get verbose debug output please */
+  test_setopt(curl, CURLOPT_VERBOSE, 1L);
+
+  /* Do not write anything. */
+  curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_it);
+
+  /* Build the first mime structure. */
+  mime1 = curl_mime_init(curl);
+  part = curl_mime_addpart(mime1);
+  curl_mime_data(part, "<title>hello</title>", CURL_ZERO_TERMINATED);
+  curl_mime_type(part, "text/html");
+  curl_mime_name(part, "data");
+
+  /* Use first mime structure as top level MIME POST. */
+  curl_easy_setopt(curl, CURLOPT_MIMEPOST, mime1);
+
+  /* Perform the request, res gets the return code */
+  res = curl_easy_perform(curl);
+
+  /* Check for errors */
+  if(res != CURLE_OK)
+    fprintf(stderr, "curl_easy_perform() 1 failed: %s\n",
+            curl_easy_strerror(res));
+  else {
+    /* phase two, create a mime struct using the mime1 handle */
+    mime2 = curl_mime_init(curl);
+    part = curl_mime_addpart(mime2);
+
+    /* use the new mime setup */
+    curl_easy_setopt(curl, CURLOPT_MIMEPOST, mime2);
+
+    /* Reuse previous mime structure as a child. */
+    res = curl_mime_subparts(part, mime1);
+
+    if(res != CURLE_OK)
+      fprintf(stderr, "curl_mime_subparts() failed: %sn",
+              curl_easy_strerror(res));
+    else {
+      mime1 = NULL;
+
+      /* Perform the request, res gets the return code */
+      res = curl_easy_perform(curl);
+
+      /* Check for errors */
+      if(res != CURLE_OK)
+        fprintf(stderr, "curl_easy_perform() 2 failed: %s\n",
+                curl_easy_strerror(res));
+    }
+  }
+
+test_cleanup:
+  curl_easy_cleanup(curl);
+  curl_mime_free(mime1);
+  curl_mime_free(mime2);
+  curl_global_cleanup();
+  return res;
+}