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ext/standard: fix use-after-free and resource reuse from write_seek_mode #25401

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ext/standard: fix use-after-free and resource reuse from write_seek_mode #25401

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5 changes: 5 additions & 0 deletions ext/standard/streamsfuncs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1339,7 +1339,12 @@ static void apply_filter_to_stream(bool append, INTERNAL_FUNCTION_PARAMETERS)
}

if (read_write & PHP_STREAM_FILTER_WRITE) {
bool originally_no_fclose = stream->flags & PHP_STREAM_FLAG_NO_FCLOSE;

@iliaal iliaal Nov 11, 2026

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The read chain has the same problem, stream_filter_append($s, 'convert.base64-encode', STREAM_FILTER_READ, ['write_seek_mode' => $obj]) still frees the stream, so the guard needs to wrap both branches.

stream->flags |= PHP_STREAM_FLAG_NO_FCLOSE;
filter = php_stream_filter_create(filtername, filterparams, php_stream_is_persistent(stream));
if (!originally_no_fclose) {
stream->flags ^= PHP_STREAM_FLAG_NO_FCLOSE;
}
if (filter == NULL) {
RETURN_FALSE;
}
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33 changes: 33 additions & 0 deletions ext/standard/tests/streams/write_seek_mode-close-uaf.phpt
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@@ -0,0 +1,33 @@
--TEST--
`write_seek_mode` with a stringable object closing the stream triggers UAF
--EXTENSIONS--
zlib
--CREDITS--
Calif.io
--FILE--
<?php

$stream = fopen('php://temp', 'w+');

final class CloseStreamForWriteSeekMode
{
public function __toString(): string
{
fclose($GLOBALS['stream']);
return 'reset';
}
}

$filter = stream_filter_append(
$stream,
'zlib.deflate',
STREAM_FILTER_WRITE,
['write_seek_mode' => new CloseStreamForWriteSeekMode()],
);

var_dump(is_resource($filter), is_resource($stream));
?>
--EXPECTF--
Warning: fclose(): cannot close the provided stream, as it must not be manually closed in %s on line %d
bool(true)
bool(true)
43 changes: 43 additions & 0 deletions ext/standard/tests/streams/write_seek_mode-reuse.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
--TEST--
`write_seek_mode` with a stringable object closing and reopening the stream triggers reuse
--EXTENSIONS--
zlib
--CREDITS--
Calif.io
--FILE--
<?php

$stream = fopen('php://temp', 'w+');
$replacementStream = null;

final class ReplaceStreamForWriteSeekMode
{
public function __toString(): string
{
fclose($GLOBALS['stream']);
$GLOBALS['replacementStream'] = fopen('php://temp', 'w+');
return 'reset';
}
}

$filter = stream_filter_append(
$stream,
'zlib.deflate',
STREAM_FILTER_WRITE,
['write_seek_mode' => new ReplaceStreamForWriteSeekMode()],
);

var_dump(is_resource($filter), is_resource($replacementStream));
fwrite($replacementStream, str_repeat('A', 64));
var_dump(stream_filter_remove($filter));
rewind($replacementStream);
$raw = stream_get_contents($replacementStream);
var_dump(strlen($raw), bin2hex($raw));
?>
--EXPECTF--
Warning: fclose(): cannot close the provided stream, as it must not be manually closed in %s on line %d
bool(true)
bool(true)
bool(true)
int(64)
string(128) "41414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141414141"
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