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From e8429400d40e3c3aa4b22ba701991d698a2f3b2f Mon Sep 17 00:00:00 2001
From: Stanislav Malyshev <stas@php.net>
Date: Mon, 31 Aug 2015 21:28:11 -0700
Subject: [PATCH] Fix bug #70172 - Use After Free Vulnerability in
unserialize()
---
ext/standard/tests/serialize/bug70172.phpt | 52 ++++++++++++++++++++
ext/standard/var.c | 23 +++++++--
ext/standard/var_unserializer.c | 76 ++++++++++++++++--------------
ext/standard/var_unserializer.re | 12 +++--
4 files changed, 121 insertions(+), 42 deletions(-)
create mode 100644 ext/standard/tests/serialize/bug70172.phpt
Index: php5-5.3.3.1/ext/standard/tests/serialize/bug70172.phpt
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ php5-5.3.3.1/ext/standard/tests/serialize/bug70172.phpt 2015-10-27 16:23:12.000000000 +0100
@@ -0,0 +1,52 @@
+--TEST--
+Bug #70172 - Use After Free Vulnerability in unserialize()
+--FILE--
+<?php
+class obj implements Serializable {
+ var $data;
+ function serialize() {
+ return serialize($this->data);
+ }
+ function unserialize($data) {
+ $this->data = unserialize($data);
+ }
+}
+
+$fakezval = ptr2str(1122334455);
+$fakezval .= ptr2str(0);
+$fakezval .= "\x00\x00\x00\x00";
+$fakezval .= "\x01";
+$fakezval .= "\x00";
+$fakezval .= "\x00\x00";
+
+$inner = 'r:2;';
+$exploit = 'a:2:{i:0;i:1;i:1;C:3:"obj":'.strlen($inner).':{'.$inner.'}}';
+
+$data = unserialize($exploit);
+
+for ($i = 0; $i < 5; $i++) {
+ $v[$i] = $fakezval.$i;
+}
+
+var_dump($data);
+
+function ptr2str($ptr)
+{
+ $out = '';
+ for ($i = 0; $i < 8; $i++) {
+ $out .= chr($ptr & 0xff);
+ $ptr >>= 8;
+ }
+ return $out;
+}
+?>
+--EXPECTF--
+array(2) {
+ [0]=>
+ int(1)
+ [1]=>
+ object(obj)#%d (1) {
+ ["data"]=>
+ int(1)
+ }
+}
\ No newline at end of file
Index: php5-5.3.3.1/ext/standard/var.c
===================================================================
--- php5-5.3.3.1.orig/ext/standard/var.c 2015-10-27 16:23:12.000000000 +0100
+++ php5-5.3.3.1/ext/standard/var.c 2015-10-27 16:23:12.000000000 +0100
@@ -913,6 +913,8 @@
int buf_len;
const unsigned char *p;
php_unserialize_data_t var_hash;
+ int oldlevel;
+ zval *old_rval = return_value;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &buf, &buf_len) == FAILURE) {
RETURN_FALSE;
@@ -930,6 +932,19 @@
php_error_docref(NULL TSRMLS_CC, E_NOTICE, "Error at offset %ld of %d bytes", (long)((char*)p - buf), buf_len);
RETURN_FALSE;
}
+ if (return_value != old_rval) {
+ /*
+ * Terrible hack due to the fact that executor passes us zval *,
+ * but unserialize with r/R wants to replace it with another zval *
+ */
+ zval_dtor(old_rval);
+ *old_rval = *return_value;
+ zval_copy_ctor(old_rval);
+ var_push_dtor_no_addref(&var_hash, &return_value);
+ var_push_dtor_no_addref(&var_hash, &old_rval);
+ } else {
+ var_push_dtor(&var_hash, &return_value);
+ }
PHP_VAR_UNSERIALIZE_DESTROY(var_hash);
}
/* }}} */
Index: php5-5.3.3.1/ext/standard/var_unserializer.c
===================================================================
--- php5-5.3.3.1.orig/ext/standard/var_unserializer.c 2015-10-27 16:23:12.000000000 +0100
+++ php5-5.3.3.1/ext/standard/var_unserializer.c 2015-10-27 16:26:09.000000000 +0100
@@ -129,6 +129,9 @@
while (var_hash) {
for (i = 0; i < var_hash->used_slots; i++) {
+#if VAR_ENTRIES_DBG
+ fprintf(stderr, "var_destroy dtor(%p, %ld)\n", var_hash->data[i], Z_REFCOUNT_P(var_hash->data[i]));
+#endif
zval_ptr_dtor(&var_hash->data[i]);
}
next = var_hash->next;
@@ -546,6 +549,7 @@
zval **args[1];
zval *arg_func_name;
+ if (!var_hash) return 0;
if (*start == 'C') {
custom_object = 1;
}
@@ -672,6 +676,7 @@
if (yych != '"') goto yy18;
++YYCURSOR;
{
+ if (!var_hash) return 0;
INIT_PZVAL(*rval);
@@ -702,6 +707,7 @@
long elements = parse_iv(start + 2);
/* use iv() not uiv() in order to check data range */
*p = YYCURSOR;
+ if (!var_hash) return 0;
if (elements < 0) {
return 0;
@@ -1131,7 +1137,7 @@
}
if (*rval != NULL) {
- zval_ptr_dtor(rval);
+ var_push_dtor_no_addref(var_hash, rval);
}
*rval = *rval_ref;
Z_ADDREF_PP(rval);
Index: php5-5.3.3.1/ext/standard/var_unserializer.re
===================================================================
--- php5-5.3.3.1.orig/ext/standard/var_unserializer.re 2015-10-27 16:23:12.000000000 +0100
+++ php5-5.3.3.1/ext/standard/var_unserializer.re 2015-10-27 16:23:12.000000000 +0100
@@ -128,6 +128,9 @@
while (var_hash) {
for (i = 0; i < var_hash->used_slots; i++) {
+#if VAR_ENTRIES_DBG
+ fprintf(stderr, "var_destroy dtor(%p, %ld)\n", var_hash->data[i], Z_REFCOUNT_P(var_hash->data[i]));
+#endif
zval_ptr_dtor(&var_hash->data[i]);
}
next = var_hash->next;
@@ -414,7 +417,7 @@
}
if (*rval != NULL) {
- zval_ptr_dtor(rval);
+ var_push_dtor_no_addref(var_hash, rval);
}
*rval = *rval_ref;
Z_ADDREF_PP(rval);
@@ -573,6 +576,7 @@
long elements = parse_iv(start + 2);
/* use iv() not uiv() in order to check data range */
*p = YYCURSOR;
+ if (!var_hash) return 0;
if (elements < 0) {
return 0;
@@ -590,6 +594,7 @@
}
"o:" iv ":" ["] {
+ if (!var_hash) return 0;
INIT_PZVAL(*rval);
@@ -612,6 +617,7 @@
zval **args[1];
zval *arg_func_name;
+ if (!var_hash) return 0;
if (*start == 'C') {
custom_object = 1;
}
|
