Bug #70096 [Ana->Csd]: Repeated iptcembed() adds superfluous FF bytes
Edit report at https://bugs.php.net/bug.php?id=70096&edit=1
ID: 70096
Updated by: cmb@php.net
Reported by: cmb@php.net
Summary: Repeated iptcembed() adds superfluous FF bytes
-Status: Analyzed
+Status: Closed
Type: Bug
Package: GetImageSize related
Operating System: *
PHP Version: 7.0.0beta1
Assigned To: cmb
Block user comment: N
Private report: N
New Comment:
Automatic comment on behalf of cmb
Revision: http://git.php.net/?p=php-src.git;a=commit;h=8c483ce36cb07d7e986484da93cf064ad1cc9dd7
Log: Fix #70096: Repeated iptcembed() adds superfluous FF bytes
Previous Comments:
------------------------------------------------------------------------
[2015-07-18 19:42:38] cmb@php.net
The algorithm to embed an APP13 marker segment into the file works
by processing the marker segments, and to copy them verbatim. The
only special handling is that after the first APP0 or APP1 marker
segment the new APP13 marker segment is inserted, and an existing
APP13 marker segment is skipped. After the latter has been done,
the rest of the stream is copied in one go; no need for further
processing the individual marker segments.
However, when an existing APP13 is recognized[1], its first byte
(FF) has already been copied to the buffer[2], and only the rest
of the marker segment is skipped. This results in duplication of
this byte.
[1] <https://github.com/php/php-src/blob/php-5.6.11/ext/standard/iptc.c#L236>
[2] <https://github.com/php/php-src/blob/php-5.6.11/ext/standard/iptc.c#L227>
------------------------------------------------------------------------
[2015-07-18 19:14:18] cmb@php.net
Related To: Bug #54173
------------------------------------------------------------------------
[2015-07-18 19:06:07] cmb@php.net
Description:
------------
Repeately calling iptcembed() causes a superfluous FF byte to be
added with each call. While this may not be a violation of the
JFIF standard (the specs are not publicly available, apparently),
I'd nonetheless consider this a bug, because repeated embedding of
the same metadata should not result in different files.
Test script:
---------------
<?php
$filename = __DIR__ . '/test.jpg';
@unlink($filename);
$im = imagecreatetruecolor(10, 10);
imagejpeg($im, $filename);
imagedestroy($im);
$data = "\x1C\x02x\x00\x0ATest image"
. "\x1C\x02t\x00\x22Copyright 2008-2009, The PHP Group";
$content = iptcembed($data, $filename);
$fp = fopen($filename, "wb");
fwrite($fp, $content);
fclose($fp);
echo filesize($filename), PHP_EOL;
clearstatcache();
$content = iptcembed($data, $filename);
$fp = fopen($filename, "wb");
fwrite($fp, $content);
fclose($fp);
echo filesize($filename), PHP_EOL;
?>
Expected result:
----------------
779
779
Actual result:
--------------
779
780
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Edit this bug report at https://bugs.php.net/bug.php?id=70096&edit=1
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