[wp-trac] [WordPress Trac] #11154: fread() code in pclzip doesn't check the result size

[WordPress Trac]

#11154: fread() code in pclzip doesn't check the result size
-----------------------------+----------------------------------------------
 Reporter:  dobesv           |       Owner:            
     Type:  defect (bug)     |      Status:  new       
 Priority:  normal           |   Milestone:  Unassigned
Component:  Upgrade/Install  |     Version:            
 Severity:  normal           |    Keywords:            
-----------------------------+----------------------------------------------
 Although this code from `class-pclzip.php` obviously works for most
 people, when running inside of teh quercus/PHP interpreter, it fails
 because quercus returns fewer bytes than requested if more than ~8000
 bytes are requested.

 {{{
         if ($p_entry['compression'] == 0) {
           // ----- Reading the file
           $p_string = @fread($this->zip_fd, $p_entry['compressed_size']);
                 echo '<p>Requested '.$p_entry['compressed_size'].' bytes
 of file '.$p_entry['filename'].' and got '.strlen($p_string)' bytes.</p>';
         }
         else {

           // ----- Reading the file
           $v_data = @fread($this->zip_fd, $p_entry['compressed_size']);

           // ----- Decompress the file
           if (($p_string = @gzinflate($v_data)) === FALSE) {
               // TBC
           }
                   echo '<p>Requested '.$p_entry['compressed_size'].' bytes
 of file '.$p_entry['filename'].' and got '.strlen($v_data)' bytes.
 Expecting uncompressed size '.$p_entry['size'].' and got
 '.strlen($p_string).' bytes back from gzinflate.</p>';
         }

 }}}

 For example when installing the flutter plugin within wordpress some files
 are not read in full:

 {{{
 Requested 12787 bytes of file fresh-
 page/thirdparty/swfupload/swfupload.swf and got 8096
 Requested 10020 bytes of file fresh-page/thirdparty/swfupload/swfupload.js
 and got 8097
 }}}

 It does seem like Quercus is behaving differently than the standard PHP
 distribution on this one, in that with a normal PHP executable it would be
 guaranteed to return all the bytes from a local file unless there was an
 EOF, so I'll also take this up with the folks at Quercus.

 My suggestion would be to add these reliable versions of fread and fwrite
 to file.php (or somewhere similarly suitable) and replace all calls to
 fread() or fwrite() that *assume* a full write or full read with calls to
 these functions:

 {{{
 function fullwrite ($sd, $buf) {
   $total = 0;
   $len = strlen($buf);

   while ($total < $len && ($written = fwrite($sd, $buf))) {
     $total += $written;
     $buf = substr($buf, $written);
   }

   return $total;
 }

 function fullread ($sd, $len) {
   $ret = '';
   $read = 0;

   while ($read < $len && ($buf = fread($sd, $len - $read))) {
     $read += strlen($buf);
     $ret .= $buf;
   }

   return $ret;
 }
 }}}

 This would be a bit more defensive in case of unusual environments, since
 as documented fread() and fwrite() are *not* guaranteed to read or write
 the full amount requested/provided.

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/11154>
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