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Bug #69706 getimagesize() can fail if the underlying stream doensn't support seeking
Submitted: 2015-05-25 18:29 UTC Modified: 2020-04-12 04:22 UTC
Votes:11
Avg. Score:4.4 ± 0.9
Reproduced:9 of 9 (100.0%)
Same Version:4 (44.4%)
Same OS:2 (22.2%)
From: deviantintegral at gmail dot com Assigned: cmb (profile)
Status: No Feedback Package: GetImageSize related
PHP Version: 5.6.9 OS: Any
Private report: No CVE-ID: None
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 [2015-05-25 18:29 UTC] deviantintegral at gmail dot com 
Description:
------------
I've verified this is an issue on PHP 5.4, 5.6, and statically on the master branch.

The AWS SDK (https://aws.amazon.com/sdk-for-php/) includes a stream wrapper that by default does not support seeking on files backed by S3. Calling getimagesize() on an image can fail if php_skip_variable() is called. I've seen this happen with images that specify the "Image Quality" EXIF tag, which is the M_APP15 constant in ext/standard/image.c.

The stream documentation states that seeking is not required to be supported by stream wrappers, and it's not clear that getimagesize() needs seeking to work properly.

I see two ways to improve this:

* Log a notice if php_skip_variable() tries to seek on an unseekable stream. That would have saved me a ton of time tracing this with GDB.
* Or, if a stream is not seekable, copy the file to the temporary file system and fetch metadata from there.

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 [2020-04-02 11:25 UTC] cmb@php.net
-Status: Open +Status: Feedback -Assigned To: +Assigned To: cmb
 [2020-04-02 11:25 UTC] cmb@php.net 
For SEEK_CUR and positive offsets, non-seekable streams are
supposed to be read (discarding what was written).  So if you can
still reproduce this issue with any of the actively supported PHP
versions[1], please provide a minimal self-contained reproduce
script.

[1] <https://www.php.net/supported-versions.php>
 [2020-04-12 04:22 UTC] php-bugs at lists dot php dot net 
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Re-Opened". Thank you.
 
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