Fixed segfault due to libcurl connection caching

Libcurl is doing connection caching. When easy handle is cleaned up,
if the handle was previously used by the curl_multi_api, the connection
remains open un the curl multi handle is cleaned up. Some protocols are
sending content like the FTP one, and libcurl try to use the
WRITEFUNCTION or the HEADERFUNCTION. Since structures used in those
callback are freed, we need to use an other callback to which avoid
segfaults.

Libcurl commit d021f2e8a00 fix this issue and should be part of 7.28.2

NEWS

@@ -7,6 +7,7 @@ PHP                                                                        NEWS
     (Johannes)
 
 - cURL extension:
+  . Fixed bug (segfault due to libcurl connection caching). (Pierrick)
   . Fixed bug #63795 (CURL >= 7.28.0 no longer support value 1 for
     CURLOPT_SSL_VERIFYHOST). (Pierrick)
   . Fixed bug #63352 (Can't enable hostname validation when using curl stream

ext/curl/interface.c

@@ -971,6 +971,15 @@ PHP_MSHUTDOWN_FUNCTION(curl)
 }
 /* }}} */
 
+/* {{{ curl_write_nothing
+ * Used as a work around. See _php_curl_close_ex
+ */
+static size_t curl_write_nothing(char *data, size_t size, size_t nmemb, void *ctx) 
+{
+	return size * nmemb;
+}
+/* }}} */
+
 /* {{{ curl_write
  */
 static size_t curl_write(char *data, size_t size, size_t nmemb, void *ctx)
@@ -2604,6 +2613,21 @@ static void _php_curl_close_ex(php_curl *ch TSRMLS_DC)
 #endif
 
 	_php_curl_verify_handlers(ch, 0 TSRMLS_CC);
+
+	/* 
+	 * Libcurl is doing connection caching. When easy handle is cleaned up,
+	 * if the handle was previously used by the curl_multi_api, the connection 
+	 * remains open un the curl multi handle is cleaned up. Some protocols are
+	 * sending content like the FTP one, and libcurl try to use the 
+	 * WRITEFUNCTION or the HEADERFUNCTION. Since structures used in those
+	 * callback are freed, we need to use an other callback to which avoid
+	 * segfaults.
+	 *
+	 * Libcurl commit d021f2e8a00 fix this issue and should be part of 7.28.2 
+	 */
+	curl_easy_setopt(ch->cp, CURLOPT_HEADERFUNCTION, curl_write_nothing);
+	curl_easy_setopt(ch->cp, CURLOPT_WRITEFUNCTION, curl_write_nothing);
+
 	curl_easy_cleanup(ch->cp);
 
 	/* cURL destructors should be invoked only by last curl handle */

ext/curl/tests/curl_multi_segfault.phpt

@@ -0,0 +1,56 @@
+--TEST--
+Segfault due to libcurl connection caching 
+--CREDITS--
+--SKIPIF--
+<?php 
+if (!extension_loaded("curl")) exit("skip curl extension not loaded");
+if (false === getenv('PHP_CURL_FTP_REMOTE_SERVER'))  exit("skip PHP_CURL_FTP_REMOTE_SERVER env variable is not defined");
+if (false === getenv('PHP_CURL_FTP_REMOTE_USER'))  exit("skip PHP_CURL_FTP_REMOTE_USER env variable is not defined");
+if (false === getenv('PHP_CURL_FTP_REMOTE_PASSWD'))  exit("skip PHP_CURL_FTP_REMOTE_PASSWD env variable is not defined");
+?>
+--FILE--
+<?php
+  $host = getenv('PHP_CURL_FTP_REMOTE_SERVER');
+  $username = getenv('PHP_CURL_FTP_REMOTE_USER');
+  $password = getenv('PHP_CURL_FTP_REMOTE_PASSWD');
+
+  // FTP this script to a server 
+  $fp  =  fopen ( __FILE__ ,  "r" );
+  $url  =  "ftp://$username:$password@$host/" ;
+
+  $ch  =  curl_init ();
+
+  curl_setopt ( $ch , CURLOPT_URL, $url );
+  curl_setopt ( $ch , CURLOPT_RETURNTRANSFER, 1 );
+
+  //force passive connection
+  curl_setopt ( $ch , CURLOPT_FTP_USE_EPSV, 0 );
+  curl_setopt ( $ch , CURLOPT_FTP_SKIP_PASV_IP, 1 );
+
+  $cmh =  curl_multi_init();
+  curl_multi_add_handle($cmh, $ch);
+
+  $active = null;
+
+  do {
+	  $mrc = curl_multi_exec($cmh, $active);
+  } while ($mrc == CURLM_CALL_MULTI_PERFORM);
+
+
+  while ($active && $mrc == CURLM_OK) {
+	  if (curl_multi_select($cmh) != -1) {
+		  do {
+			  $mrc = curl_multi_exec($cmh, $active);
+		  } while ($mrc == CURLM_CALL_MULTI_PERFORM);
+	  }
+  }   
+    
+  var_dump(is_string(curl_multi_getcontent($ch)));
+  curl_multi_remove_handle($cmh, $ch);
+  curl_close($ch);
+  curl_multi_close($cmh);
+?>
+===DONE===
+--EXPECTF--
+bool(true)
+===DONE===