Fix truncating of attachments on upload

MySQL is kind enough to quietly truncate the filedata field when attempting
to CONCAT data beyond the size of max_allowed_packet. The simplest fix is to
automatically adjust the max_allowed_packet to the size of the file being
uploaded plus some extra. See MySQL bugs #22853, #34782, and #63919 for more
discussion on the issue.

The max_allowed_packet variable default to 1M, but is expandable to 1G.
Therefore, the fixed limit of attachments for osTicket will be 1G, since it
would be impossible for MySQL to append data after that mark. *Sigh*

include/class.file.php

@@ -92,16 +92,15 @@ class AttachmentFile {
     }
 
     function sendData() {
-        # XXX: For maximum efficiency,
-        #      do "show variables like 'max_allowed_packet'", and use the
-        #      lesser of half of PHP's memory limit and that value as the
-        #      chunk_size
         $chunk_size = 256 * 1024;
-        for ($start=1; $start<$this->getSize(); $start+=$chunk_size) {
+        $start = 1;
+        for (;;) {
             list($data) = db_fetch_row(db_query(
                 'SELECT SUBSTRING(filedata,'.$start.','.$chunk_size
                 .') FROM '.FILE_TABLE.' WHERE id='.db_input($this->getId())));
+            if (!$data) break;
             echo $data;
+            $start += $chunk_size;
         }
     }
 
@@ -185,14 +184,27 @@ class AttachmentFile {
         if (!(db_query($sql) && ($id=db_insert_id())))
             return false;
 
-        foreach (str_split($file['data'], 1024*100) as $chunk) {
+        $chunk_size = 256 * 1024;
+        $start = 0;
+        # This boils down to a disagreement between the MySQL community and
+        # developers. I'll refrain from a soapbox discussion here, but MySQL
+        # will truncate the field to '' when the length of a CONCAT expression
+        # exceeds the value of max_allowed_packet. See the following bugs for
+        # more information. The easiest fix is to expand the parameter.
+        # http://bugs.mysql.com/bug.php?id=22853
+        # http://bugs.mysql.com/bug.php?id=34782
+        # http://bugs.mysql.com/bug.php?id=63919
+        if (db_get_variable('max_allowed_packet') < strlen($file['data']))
+            db_set_variable('max_allowed_packet', strlen($file['data']) + $chunk_size);
+        while ($chunk = substr($file['data'], $start, $chunk_size)) {
             $sql='UPDATE '.FILE_TABLE
-                .' SET filedata = CONCAT(filedata,'.db_input($chunk).')'
+                .' SET filedata = CONCAT(filedata, 0x'.bin2hex($chunk).')'
                 .' WHERE id='.db_input($id);
             if(!db_query($sql)) {
                 db_query('DELETE FROM '.FILE_TABLE.' WHERE id='.db_input($id).' LIMIT 1');
                 return false;
             }
+            $start += $chunk_size;
         }
 
         return $id;