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Limit the number of filters #16699

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Limit the number of filters #16699

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10 changes: 10 additions & 0 deletions ext/standard/php_fopen_wrapper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
#include "php_memory_streams.h"
#include "php_fopen_wrappers.h"
#include "SAPI.h"
#include "zend_exceptions.h"

static ssize_t php_stream_output_write(php_stream *stream, const char *buf, size_t count) /* {{{ */
{
Expand Down Expand Up @@ -146,13 +147,22 @@ static const php_stream_ops php_stream_input_ops = {
NULL /* set_option */
};

static const char max_stream_filters = 5;

static void php_stream_apply_filter_list(php_stream *stream, char *filterlist, int read_chain, int write_chain) /* {{{ */
{
char *p, *token = NULL;
php_stream_filter *temp_filter;
char nb_filters = 0;

p = php_strtok_r(filterlist, "|", &token);
while (p) {
if (nb_filters >= max_stream_filters) {
zend_throw_exception_ex(NULL, 0, "Unable to apply filter, maximum number (%d) reached", max_stream_filters);
return;
}
nb_filters++;

php_url_decode(p, strlen(p));
if (read_chain) {
if ((temp_filter = php_stream_filter_create(p, NULL, php_stream_is_persistent(stream)))) {
Expand Down
20 changes: 20 additions & 0 deletions tests/security/bug10453.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
--TEST--
Bug #10453 (using a high amount of filters for nefarious purposes)
--FILE--
<?php
$fp = fopen('php://output', 'w');
for($i=0; $i<10; $i++)
stream_filter_append($fp, 'string.rot13');
fwrite($fp, "This is a test.\n");

$fp = fopen('php://filter/write=string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13|string.rot13/resource=php://output', 'w');
fwrite($fp, "This is a test.\n");
?>
--EXPECTF--
This is a test.

Fatal error: Uncaught Exception: Unable to apply filter, maximum number (5) reached in %s
Stack trace:
#0 %s: fopen('php://filter/wr...', 'w')
#1 {main}
thrown in %s