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[2015-06-11 23:22 UTC] brian dot carpenter at gmail dot com
Description: ------------ While fuzzing PHP 7 built from git source with AFL (http://lcamtuf.coredump.cx/afl/), I discoved a script that causes a null ptr deref and a seg fault in zend_resolve_class_name (zend_compile.c:816). Test script: --------------- <?php class p{public function c(){(0)::t;}}?> Expected result: ---------------- No crash. PHP 5.4.41-0+deb7u1 fails with PHP Parse error: syntax error, unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM) in test00-min on line 2 Actual result: -------------- Program received signal SIGSEGV, Segmentation fault. zend_resolve_class_name () at /home/geeknik/php-src/Zend/zend_compile.c:816 816 if (name->val[0] == '\\') { (gdb) bt #0 zend_resolve_class_name () at /home/geeknik/php-src/Zend/zend_compile.c:816 #1 0x000000000135f616 in zend_compile_class_const () at /home/geeknik/php-src/Zend/zend_compile.c:859 #2 0x0000000001361765 in zend_compile_expr () at /home/geeknik/php-src/Zend/zend_compile.c:6982 #3 0x000000000137d733 in zend_compile_stmt () at /home/geeknik/php-src/Zend/zend_compile.c:6864 #4 0x000000000137d8f1 in zend_compile_stmt () at /home/geeknik/php-src/Zend/zend_compile.c:4186 #5 0x000000000138613a in zend_compile_func_decl () at /home/geeknik/php-src/Zend/zend_compile.c:4690 #6 0x000000000137ddb6 in zend_compile_stmt () at /home/geeknik/php-src/Zend/zend_compile.c:6832 #7 0x000000000137d8f1 in zend_compile_stmt () at /home/geeknik/php-src/Zend/zend_compile.c:4186 #8 0x0000000001382416 in zend_compile_class_decl () at /home/geeknik/php-src/Zend/zend_compile.c:5095 #9 0x000000000137de35 in zend_compile_stmt () at /home/geeknik/php-src/Zend/zend_compile.c:6844 #10 0x000000000138930d in zend_compile_top_stmt () at /home/geeknik/php-src/Zend/zend_compile.c:6754 #11 0x0000000001290a4b in compile_file () #12 0x0000000000d32a30 in phar_compile_file () #13 0x0000000001410194 in zend_execute_scripts () #14 0x00000000011c2a20 in php_execute_script () #15 0x0000000001807d05 in do_cli () at /home/geeknik/php-src/sapi/cli/php_cli.c:967 #16 0x000000000043c021 in main () at /home/geeknik/php-src/sapi/cli/php_cli.c:1334 (gdb) i r rax 0x0 0 rbx 0x0 0 rcx 0x1 1 rdx 0x7ffff6078120 140737321074976 rsi 0x0 0 rdi 0x0 0 rbp 0x1fd4a80 0x1fd4a80 rsp 0x7fffffffa120 0x7fffffffa120 r8 0x0 0 r9 0x7ffff6078108 140737321074952 r10 0x7ffff6087e80 140737321139840 r11 0x7ffff6b54730 140737332463408 r12 0x7ffff6078108 140737321074952 r13 0x7ffff6078150 140737321075024 r14 0x7ffff6078138 140737321075000 r15 0x7fffffffa290 140737488331408 rip 0x133b928 0x133b928 <zend_resolve_class_name+216> eflags 0x10246 [ PF ZF IF RF ] cs 0x33 51 ss 0x2b 43 ds 0x0 0 es 0x0 0 fs 0x0 0 gs 0x0 0 (gdb) exploitable Description: Access violation near NULL on destination operand Short description: DestAvNearNull (15/22) Hash: ec3b50a338012ebadab79a091988f0f6.5154e9673347c8e70cb47d11f3d8468e Exploitability Classification: PROBABLY_EXPLOITABLE Explanation: The target crashed on an access violation at an address matching the destination operand of the instruction. This likely indicates a write access violation, which means the attacker may control write address and/or value. However, it there is a chance it could be a NULL dereference. Other tags: AccessViolation (21/22) PatchesPull RequestsHistoryAllCommentsChangesGit/SVN commits
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Last updated: Sat Dec 21 17:01:58 2024 UTC |
A simple fix is: diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c index 9be3748..902d37c 100644 --- a/Zend/zend_compile.c +++ b/Zend/zend_compile.c @@ -855,8 +855,11 @@ zend_string *zend_resolve_class_name(zend_string *name, uint32_t type) /* {{{ */ zend_string *zend_resolve_class_name_ast(zend_ast *ast) /* {{{ */ { - zend_string *name = zend_ast_get_str(ast); - return zend_resolve_class_name(name, ast->attr); + zval *class_name = zend_ast_get_zval(ast); + if (Z_TYPE_P(class_name) != IS_STRING) { + zend_error_noreturn(E_COMPILE_ERROR, "Illegal class name"); + } + return zend_resolve_class_name(Z_STR_P(class_name), ast->attr); } /* }}} */ Nikic, do you have better one? thanks