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Bug #80964 A use after free bug in ext/phar/phar.c
Submitted: 2021-04-18 05:45 UTC Modified: 2021-05-23 04:22 UTC
From: lylgood at foxmail dot com Assigned:
Status: No Feedback Package: *Extensibility Functions
PHP Version: master-Git-2021-04-18 (Git) OS: All
Private report: No CVE-ID: None
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 [2021-04-18 05:45 UTC] lylgood at foxmail dot com 
Description:
------------
File: ext/phar/phar.c
Bug Function: phar_entry_remove

In function phar_entry_remove, idata->phar is assigned to phar at line 419.
The idata->phar could be freed at line 430 by calling phar_entry_delref(idata)->phar_archive_delref(idata->phar)->phar_destroy_phar_data(phar).
Whereas the freed idata->phar is dereferenced via phar->donotflus at line 433,
which causes a use after free bug.




Test script:
---------------
419:	phar = idata->phar;

	if (idata->internal_file->fp_refcount < 2) {
		if (idata->fp && idata->fp != idata->phar->fp && idata->fp != idata->phar->ufp && idata->fp != idata->internal_file->fp) {
			php_stream_close(idata->fp);
		}
		zend_hash_str_del(&idata->phar->manifest, idata->internal_file->filename, idata->internal_file->filename_len);
		idata->phar->refcount--;
		efree(idata);
	} else {
		idata->internal_file->is_deleted = 1;
430:		phar_entry_delref(idata); // idata->phar freed here !
	}

433:	if (!phar->donotflush) {  // use after free here!

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 [2021-04-26 02:53 UTC] lylgood at foxmail dot com 
Hi, maintainers.

Sorry to distrub you. Is the bug is a truth one?
Thanks for your time.
 [2021-04-26 15:45 UTC] cmb@php.net 
I think the scenario you're describing is never supposed to
happen, due to the refcount check on line 421.  However, that is
about phar_archive_data->internal_file->fp_refcount and not
phar_archive_data->refcount, so I'm not sure.
 [2021-05-11 06:39 UTC] krakjoe@php.net
-Status: Open +Status: Feedback
 [2021-05-11 06:39 UTC] krakjoe@php.net 
Thank you for this bug report. To properly diagnose the problem, we
need a short but complete example script to be able to reproduce
this bug ourselves.

A proper reproducing script starts with <?php and ends with ?>,
is max. 10-20 lines long and does not require any external
resources such as databases, etc. If the script requires a
database to demonstrate the issue, please make sure it creates
all necessary tables, stored procedures etc.

Please avoid embedding huge scripts into the report.
 [2021-05-23 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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