Bug #68547 [Opn]: PHP 5.6.2 Exif Header component value check error

Edit report at https://bugs.php.net/bug.php?id=68547&edit=1 ID: 68547 User updated by: sjh21a at gmail dot com Reported by: sjh21a at gmail dot com Summary: PHP 5.6.2 Exif Header component value check error Status: Open Type: Bug Package: EXIF related Operating System: Ubuntu 14.04 PHP Version: 5.6.3 Block user comment: N Private report: N New Comment: i found this bug on php-5.6.2 but still work 5.6.3 Previous Comments: ------------------------------------------------------------------------ [2014-12-04 23:34:41] sjh21a at gmail dot com Description: ------------ PHP 5.6.2 Exif Header component value check error this bug is exif_process_IFD_TAG() function of ext/exif.c in exif header, get a components value as follows 2818: components = php_ifd_get32u(dir_entry+4, ImageInfo->motorola_intel); dir_entry+4 exists in jpg or tiff files, attacker can modify this all. look at the below code, a wrong check to components value. 2827: if (components < 0) { 2828: exif_error_docref("exif_read_data#error_ifd" EXIFERR_CC, ImageInfo, E_WARNING, "Process tag(x%04X=%s): Illegal components(%ld)", tag, exif_get_tagname(tag, tagname, -12, tag_table TSRMLS_CC), components); 2829: return FALSE; 2830: } only check to components value is negative, doesn't check to 0 value if components value was 0, problem occurs in the below code. 2832: byte_count_signed = (int64_t)components * php_tiff_bytes_per_format[format]; above calculation result are being 0, this can bypass to below code. 2833: if (byte_count_signed < 0 || (byte_count_signed > INT32_MAX)) { 2834: exif_error_docref("exif_read_data#error_ifd" EXIFERR_CC, ImageInfo, E_WARNING, "Process tag(x%04X=%s): Illegal byte_count", tag, exif_get_tagname(tag, tagname, -12, tag_table TSRMLS_CC)); 2835: return FALSE; 2836: } effect: an attacker may be free to any memory area, if do not use to zend_mm, use after free has occurred. set the memory to be free from jpg file. enable zend_mm root@ubuntu:~/x# php x.php crash.jpg ; gdb -q php core Segmentation fault (core dumped) Reading symbols from php...done. [New LWP 9998] [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1". Core was generated by `php x.php crash.jpg'. Program terminated with signal SIGSEGV, Segmentation fault. #0 _zend_mm_free_int (heap=0x887ea38, p=0x41414141) at /root/php-5.6.2/Zend/zend_alloc.c:2076 ^^^^^^^^^^^^^ 2076 size = ZEND_MM_BLOCK_SIZE(mm_block); (gdb) disable zend_mm : # export USE_ZEND_ALLOC=0 root@ubuntu:~/x# php x.php crash.jpg ; gdb -q php core Segmentation fault (core dumped) Reading symbols from php...done. [New LWP 10016] [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1". Core was generated by `php x.php crash.jpg'. Program terminated with signal SIGSEGV, Segmentation fault. #0 __GI___libc_free (mem=0x41414141) at malloc.c:2929 ^^^^^^^^^^^^^^ 2929 malloc.c: No such file or directory. (gdb) Test script: --------------- root@ubuntu:~/x# cat x.php <? error_reporting(0); exif_read_data($argv[1]); exif_thumbnail($argv[1]); ?> and below link is crash image file https://www.dropbox.com/s/hius8be0r9h8hk0/trig.jpg?dl=0 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=68547&edit=1