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

lib/mqtt.c

@@ -319,7 +319,7 @@ static CURLcode mqtt_publish(struct connectdata *conn)
 {
   CURLcode result;
   char *payload = conn->data->set.postfields;
-  size_t payloadlen = (size_t)conn->data->set.postfieldsize;
+  size_t payloadlen;
   char *topic = NULL;
   size_t topiclen;
   unsigned char *pkt = NULL;
@@ -327,6 +327,14 @@ static CURLcode mqtt_publish(struct connectdata *conn)
   size_t remaininglength;
   size_t encodelen;
   char encodedbytes[4];
+  curl_off_t postfieldsize = conn->data->set.postfieldsize;
+
+  if(!payload)
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  if(postfieldsize < 0)
+    payloadlen = strlen(payload);
+  else
+    payloadlen = (size_t)postfieldsize;
 
   result = mqtt_get_topic(conn, &topic, &topiclen);
   if(result)

tests/data/Makefile.inc

@@ -205,6 +205,7 @@ test1800 test1801 \
 \
                                     test1904 test1905 test1906 test1907 \
 test1908 test1909 test1910 test1911 test1912 test1913 test1914 test1915 \
+test1916 test1917 \
 \
 test2000 test2001 test2002 test2003 test2004 test2005 test2006 test2007 \
 test2008 test2009 test2010 test2011 test2012 test2013 test2014 test2015 \

tests/data/test1198

@@ -30,7 +30,7 @@ mqtt
 MQTT PUBLISH empty payload, single space topic
 </name>
 <command option="binary-trace">
-"mqtt:/%HOSTIP:%MQTTPORT/ " -d ""
+mqtt://%HOSTIP:%MQTTPORT/%20 -d ""
 </command>
 </client>
 

tests/data/test1199

@@ -30,7 +30,7 @@ mqtt
 MQTT PUBLISH empty payload, no topic
 </name>
 <command option="binary-trace">
-"mqtt:/%HOSTIP:%MQTTPORT/" -d ""
+mqtt://%HOSTIP:%MQTTPORT -d ""
 </command>
 </client>
 

tests/data/test1916

@@ -0,0 +1,57 @@
+<testcase>
+<info>
+<keywords>
+MQTT
+MQTT PUBLISH
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data nocheck="yes">
+hello
+</data>
+<datacheck hex="yes">
+00 04 31 31 39 30   68 65 6c 6c 6f 5b 4c 46 5d 0a
+</datacheck>
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+mqtt
+</features>
+<server>
+mqtt
+</server>
+<name>
+MQTT PUBLISH with no POSTFIELDSIZE set
+</name>
+<tool>
+lib1916
+</tool>
+<command option="binary-trace">
+"mqtt://%HOSTIP:%MQTTPORT/ "
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+# These are hexadecimal protocol dumps from the client
+#
+# Strip out the random part of the client id from the CONNECT message
+# before comparison
+<strippart>
+s/^(.* 00044d5154540402003c000c6375726c).*/$1/
+</strippart>
+<protocol>
+client CONNECT 18 00044d5154540402003c000c6375726c
+server CONNACK 2 20020000
+client PUBLISH 3 000120
+client DISCONNECT 0 e000
+</protocol>
+</verify>
+</testcase>

tests/data/test1917

@@ -0,0 +1,61 @@
+<testcase>
+<info>
+<keywords>
+MQTT
+MQTT PUBLISH
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data nocheck="yes">
+hello
+</data>
+<datacheck hex="yes">
+00 04 31 31 39 30   68 65 6c 6c 6f 5b 4c 46 5d 0a
+</datacheck>
+</reply>
+
+#
+# Client-side
+<client>
+
+# require HTTP too as otherwise CURLOPT_POST doesn't exist
+<features>
+mqtt
+http
+</features>
+<server>
+mqtt
+</server>
+<name>
+MQTT PUBLISH with CURLOPT_POST set (no payload)
+</name>
+<tool>
+lib1917
+</tool>
+<command option="binary-trace">
+"mqtt://%HOSTIP:%MQTTPORT/ "
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+# These are hexadecimal protocol dumps from the client
+#
+# Strip out the random part of the client id from the CONNECT message
+# before comparison
+<strippart>
+s/^(.* 00044d5154540402003c000c6375726c).*/$1/
+</strippart>
+<protocol>
+client CONNECT 18 00044d5154540402003c000c6375726c
+server CONNACK 2 20020000
+</protocol>
+<errorcode>
+43
+</errorcode>
+</verify>
+</testcase>

tests/libtest/Makefile.inc

@@ -59,7 +59,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib1558 lib1559 lib1560 lib1564 lib1565 lib1567 \
  lib1591 lib1592 lib1593 lib1594 lib1596 \
          lib1905 lib1906 lib1907 lib1908 lib1910 lib1911 lib1912 lib1913 \
-         lib1915 \
+         lib1915 lib1916 lib1917 \
          lib3010
 
 chkdecimalpoint_SOURCES = chkdecimalpoint.c ../../lib/mprintf.c \
@@ -655,6 +655,12 @@ lib1915_SOURCES = lib1915.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1915_LDADD = $(TESTUTIL_LIBS)
 lib1915_CPPFLAGS = $(AM_CPPFLAGS)
 
+lib1916_SOURCES = lib1916.c $(SUPPORTFILES) $(WARNLESS)
+lib1916_CPPFLAGS = $(AM_CPPFLAGS)
+
+lib1917_SOURCES = lib1916.c $(SUPPORTFILES) $(WARNLESS)
+lib1917_CPPFLAGS = $(AM_CPPFLAGS) -DLIB1917
+
 lib3010_SOURCES = lib3010.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib3010_LDADD = $(TESTUTIL_LIBS)
 lib3010_CPPFLAGS = $(AM_CPPFLAGS)

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;
+}