发布日期：2011-12-05
更新日期：2011-12-06
受影响系统：
PHP PHP 5.4.0beta2
描述：
--------------------------------------------------------------------------------
BUGTRAQ ID: 50907
CVE ID: CVE-2011-4566
PHP是一种在电脑上运行的脚本语言，主要用途是在于处理动态网页，包含了命令行运行接口或者产生图形用户界面程序。
PHP的实现上存在漏洞，在32位版本中，函数exif_process_IFD_TAG没有正确检验值offset_val，成功利用此漏洞可允许远程攻击者在受影响Web服务器中执行任意代码，可能会造成拒绝服务。
<*来源：flolechaud
链接：https://bugs.php.net/bug.php?id=60150
*>
测试方法：
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警 告
以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！
====
exif.c:2852:
value_ptr = offset_base+offset_val;
if (offset_val+byte_count > IFDlength || value_ptr < dir_entry)
{
====
The check (offset_val + byte_count) is not safe :
(gdb)
2852 value_ptr = offset_base+offset_val;
(gdb)
2853 if (offset_val+byte_count > IFDlength || value_ptr <
dir_entry) {
(gdb)
2905 ImageInfo->sections_found |= FOUND_ANY_TAG;
(gdb) p/x offset_base
$1 = 0x5af564
(gdb) p/x offset_val
$2 = 0xf20008bc
(gdb) p/x value_ptr
$3 = 0xf25afe20
(gdb) p/x offset_val
$4 = 0xf20008bc
(gdb) p/x byte_count
$5 = 0xe000067
(gdb) p/x IFDlength
$6 = 0x1586
(gdb) p/x offset_val+byte_count
$7 = 0x923
(gdb) p/x (int64_t)offset_val+byte_count
$8 = 0x100000923
$ CFLAGS="-m32 -g" CXXFLAGS="-m32 -g" ./configure --disable-all --enable-exif
$ CFLAGS="-m32 -g" CXXFLAGS="-m32 -g" make
$ php --version
PHP 5.4.0beta1 (cli) (built: Oct 19 2011 21:15:00)
Copyright (c) 1997-2011 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2011 Zend Technologies
Test script:
---------------
florent$ cat run.php
<?php
$exif = exif_read_data($argv[1]);
?>
florent$ php run.php ./sample.jpg
Expected result:
----------------
Warning or Error without bad pointer dereference.
Actual result:
--------------
(gdb) r run.php ./Sample.jpg
Starting program: /Users/florent/Downloads/php-5.4.0beta1/sapi/cli/php run.php
./Sample.jpg
Reading symbols for shared libraries ++........................ done
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0xf25afe24
0x0008ba9c in php_strnlen (str=0xf25afe24 <Address 0xf25afe24 out of bounds>,
maxlen=234881127) at exif.c:296
296 if (str && maxlen && *str) {
(gdb) bt
#0 0x0008ba9c in php_strnlen (str=0xf25afe24 <Address 0xf25afe24 out of
bounds>, maxlen=234881127) at exif.c:296
#1 0x0008cf04 in exif_iif_add_value (image_info=0xbfffee30, section_index=7,
name=0xbfffe818 "DateTimeOriginal", tag=36867, format=2, length=234881127,
value=0xf25afe24, motorola_intel=0) at exif.c:1699
#2 0x0008d284 in exif_iif_add_tag (image_info=0xbfffee30, section_index=7,
name=0xbfffe818 "DateTimeOriginal", tag=36867, format=2, length=234881127,
value=0xf25afe24) at exif.c:1803
#3 0x00090b56 in exif_process_IFD_TAG (ImageInfo=0xbfffee30, dir_entry=0x5af6a8
"\003?\002", offset_base=0x5af568 "II*", IFDlength=5510, displacement=12,
section_index=7, ReadNextIFD=1, tag_table=0x4291a0) at exif.c:3110
#4 0x00090d20 in exif_process_IFD_in_JPEG (ImageInfo=0xbfffee30,
dir_start=0x5af66a "#", offset_base=0x5af568 "II*", IFDlength=5510,
displacement=12, section_index=7) at exif.c:3138
#5 0x00090ae3 in exif_process_IFD_TAG (ImageInfo=0xbfffee30, dir_entry=0x5af5ea
"i?\004", offset_base=0x5af568 "II*", IFDlength=5510, displacement=12,
section_index=3, ReadNextIFD=1, tag_table=0x4291a0) at exif.c:3101
#6 0x00090d20 in exif_process_IFD_in_JPEG (ImageInfo=0xbfffee30,
dir_start=0x5af570 "\f", offset_base=0x5af568 "II*", IFDlength=5510,
displacement=12, section_index=3) at exif.c:3138
#7 0x00091032 in exif_process_TIFF_in_JPEG (ImageInfo=0xbfffee30,
CharBuf=0x5af568 "II*", length=5510, displacement=12) at exif.c:3215
#8 0x0009114a in exif_process_APP1 (ImageInfo=0xbfffee30, CharBuf=0x5af560
"\025?Exif", length=5518, displacement=4) at exif.c:3240
#9 0x00091792 in exif_scan_JPEG_header (ImageInfo=0xbfffee30) at exif.c:3385
#10 0x000927e4 in exif_scan_FILE_header (ImageInfo=0xbfffee30) at exif.c:3763
#11 0x000931c8 in exif_read_file (ImageInfo=0xbfffee30, FileName=0x5aa3c4
"./Sample.jpg", read_thumbnail=0, read_all=0) at exif.c:3902
#12 0x00093412 in zif_exif_read_data (ht=1, return_value=0x5ab254,
return_value_ptr=0x0, this_ptr=0x0, return_value_used=1) at exif.c:3955
#13 0x00265c88 in zend_do_fcall_common_helper_SPEC (execute_data=0x592028) at
zend_vm_execute.h:642
#14 0x0026d26b in ZEND_DO_FCALL_SPEC_CONST_HANDLER (execute_data=0x592028) at
zend_vm_execute.h:2215
#15 0x00264529 in execute (op_array=0x5ac7a4) at zend_vm_execute.h:410
#16 0x00225f27 in zend_execute_scripts (type=8, retval=0x0, file_count=3) at
zend.c:1271
#17 0x00199f29 in php_execute_script (primary_file=0xbffffa60) at main.c:2391
#18 0x0038625c in do_cli (argc=3, argv=0xbffffc04) at php_cli.c:983
#19 0x00387837 in main (argc=3, argv=0xbffffc04) at php_cli.c:1356
建议：
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