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Fix UAF issues with PCRE after request shutdown #15205
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,12 @@ | ||
| --TEST-- | ||
| GH-15205: UAF when destroying RegexIterator after pcre request shutdown | ||
| --CREDITS-- | ||
| YuanchengJiang | ||
| --FILE-- | ||
| <?php | ||
| $array = new ArrayIterator(array('a', array('b', 'c'))); | ||
| $regex = [new RegexIterator($array, '/Array/')]; | ||
| echo "Done\n"; | ||
| ?> | ||
| --EXPECT-- | ||
| Done |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| --TEST-- | ||
| GH-15205: UAF when destroying stream after pcre request shutdown | ||
| --CREDITS-- | ||
| nicolaslegland | ||
| --FILE-- | ||
| <?php | ||
| // Prime cache | ||
| preg_replace('/pattern/', 'replace', 'subject'); | ||
|
|
||
| class wrapper | ||
| { | ||
| public function stream_open($path, $mode, $options, &$opened_path) | ||
| { | ||
| return true; | ||
| } | ||
|
|
||
| public function stream_close() | ||
| { | ||
| echo "Close\n"; | ||
| preg_replace('/pattern/', 'replace', 'subject'); | ||
| preg_match('/(4)?(2)?\d/', '23456', $matches, PREG_OFFSET_CAPTURE | PREG_UNMATCHED_AS_NULL); | ||
| preg_match('/(4)?(2)?\d/', '23456', $matches, PREG_OFFSET_CAPTURE); | ||
| } | ||
|
|
||
| public $context; | ||
| } | ||
|
|
||
| stream_wrapper_register('wrapper', 'wrapper'); | ||
| $handle = fopen('wrapper://', 'rb'); | ||
| ?> | ||
| --EXPECT-- | ||
| Close |
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Based on the description and what I've understood at so far... couldn't you re-initialize this to an empty table after the
zend_hash_destroy? No more use-after-free, no other code changes necessary because it's still got a valid hash table in it?There was a problem hiding this comment.
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The change described as-is would only work for the resource test. The spl test would still cause a uaf because it references the pcre cache entry directly. That would be solvable by always looking up the instance from the cache though.
However, even with the uaf out of the way, the issue still wouldn't be fixed as the pcre entry no longer exists, so then we end up with an exception on cli while the code works fine on non-cli SAPIs. We could fix that by allowing to re-add entries to the hash table, but that is all messy and complicated and opens the question of who needs to clean up the cache entries after re-adding them after they were removed in the first place.