#6571: Warnings from EXIF reader cause malformed XMLRPC responses
------------------------+---------------------------------------------------
Reporter: redsweater | Owner: josephscott
Type: defect | Status: new
Priority: high | Milestone: 2.7
Component: XML-RPC | Version: 2.5
Severity: normal | Keywords:
------------------------+---------------------------------------------------
Note: This is a new bug in 2.5. The problem does not exist in 2.3.3.
The addition of the exif_read_data function in wp-admin/includes/image.php
causes a scenario where the exif reader prints warning text directly to
the output, thus corrupting both HTML and XMLRPC output in differing ways.
When the debug info is printed in the web/HTML based upload flow, it
mainly just upsets the visual beauty of the web page, but when it is
printed as part of the XMLRPC based upload flow, the text is inserted
before the XML cargo and therefore violates the expectations of the
protocol.
The problem at its core seems to be that exif_read_data will print warning
information even for image types that are otherwise supported. Case #5397
ran into a similar version of this issue, but only partly fixed it by
blocking out image types that are known to "provoke" the EXIF reader. I
think there has to be some more radical fix for this, possibly by
silencing the exif reader's warnings, or by redirecting those warnings
temporarily to a non-stdout location?
The end result for users today of XMLRPC based clients is if they upload
an image to 2.5 that triggers these warnings, the resulting XML is
corrupted and the client is likely to reject the response as not well
formed XML.
An example of an image that provokes such as a warning is attached. Note
that images generated by Adobe products such as Lightroom or Photoshop
seem to provoke the warnings.
An example of such a corrupted response is pasted here:
{{{
Response text:
<br />
<b>Warning</b>: exif_read_data(waffles1.jpg) [<a href='function.exif-
read-data'>function.exif-read-data</a>]: Incorrect APP1 Exif Identifier
Code in <b>/Volumes/Data/Users/daniel/Documents/WebSites/red-
sweater.com/wptrunk/wp-admin/includes/image.php</b> on line <b>238</b><br
/>
<br />
<b>Warning</b>: Cannot modify header information - headers already sent
by (output started at /Volumes/Data/Users/daniel/Documents/WebSites/red-
sweater.com/wptrunk/wp-admin/includes/image.php:238) in
<b>/Volumes/Data/Users/daniel/Documents/WebSites/red-sweater.com/wptrunk
/wp-includes/class-IXR.php</b> on line <b>363</b><br />
<br />
<b>Warning</b>: Cannot modify header information - headers already sent
by (output started at /Volumes/Data/Users/daniel/Documents/WebSites/red-
sweater.com/wptrunk/wp-admin/includes/image.php:238) in
<b>/Volumes/Data/Users/daniel/Documents/WebSites/red-sweater.com/wptrunk
/wp-includes/class-IXR.php</b> on line <b>364</b><br />
<br />
<b>Warning</b>: Cannot modify header information - headers already sent
by (output started at /Volumes/Data/Users/daniel/Documents/WebSites/red-
sweater.com/wptrunk/wp-admin/includes/image.php:238) in
<b>/Volumes/Data/Users/daniel/Documents/WebSites/red-sweater.com/wptrunk
/wp-includes/class-IXR.php</b> on line <b>365</b><br />
<br />
<b>Warning</b>: Cannot modify header information - headers already sent
by (output started at /Volumes/Data/Users/daniel/Documents/WebSites/red-
sweater.com/wptrunk/wp-admin/includes/image.php:238) in
<b>/Volumes/Data/Users/daniel/Documents/WebSites/red-sweater.com/wptrunk
/wp-includes/class-IXR.php</b> on line <b>366</b><br />
<?xml version="1.0"?>
<methodResponse>
<params>
<param>
<value>
<struct>
<member><name>file</name><value><string>waffles.jpg</string></value></member>
<member><name>url</name><value><string>http://192.168.1.20/wptrunk/wp-
content/uploads/waffles1.jpg</string></value></member>
<member><name>type</name><value><string>image/jpeg</string></value></member>
</struct>
</value>
</param>
</params>
</methodResponse>
}}}
--
Ticket URL: <http://trac.wordpress.org/ticket/6571>
WordPress Trac <http://trac.wordpress.org/>
WordPress blogging software