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[2016-10-04 18:00 UTC] fernando at null-life dot com
Description: ------------ When "encoding" length parameter is equal or close to 0x7fffff, stack-overflow happens in libc.so. Some affected functions are: XMLReader::open and XMLReader::xml ----------------------------------- Source code: https://github.com/php/php-src/blob/master/ext/xmlreader/php_xmlreader.c#L851 PHP_METHOD(xmlreader, open) { zval *id; size_t source_len = 0, encoding_len = 0; zend_long options = 0; xmlreader_object *intern = NULL; char *source, *valid_file = NULL; char *encoding = NULL; char resolved_path[MAXPATHLEN + 1]; xmlTextReaderPtr reader = NULL; if (zend_parse_parameters(ZEND_NUM_ARGS(), "p|s!l", &source, &source_len, &encoding, &encoding_len, &options) == FAILURE) { return; } id = getThis(); if (id != NULL) { if (! instanceof_function(Z_OBJCE_P(id), xmlreader_class_entry)) { id = NULL; } else { intern = Z_XMLREADER_P(id); xmlreader_free_resources(intern); } } if (!source_len) { php_error_docref(NULL, E_WARNING, "Empty string supplied as input"); RETURN_FALSE; } valid_file = _xmlreader_get_valid_file_path(source, resolved_path, MAXPATHLEN ); if (valid_file) { reader = xmlReaderForFile(valid_file, encoding, options); // encoding length not checked } ... https://github.com/php/php-src/blob/master/ext/xmlreader/php_xmlreader.c#L1035 PHP_METHOD(xmlreader, XML) { zval *id; size_t source_len = 0, encoding_len = 0; zend_long options = 0; xmlreader_object *intern = NULL; char *source, *uri = NULL, *encoding = NULL; int resolved_path_len, ret = 0; char *directory=NULL, resolved_path[MAXPATHLEN]; xmlParserInputBufferPtr inputbfr; xmlTextReaderPtr reader; if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|s!l", &source, &source_len, &encoding, &encoding_len, &options) == FAILURE) { return; } id = getThis(); if (id != NULL && ! instanceof_function(Z_OBJCE_P(id), xmlreader_class_entry)) { id = NULL; } if (id != NULL) { intern = Z_XMLREADER_P(id); xmlreader_free_resources(intern); } if (!source_len) { php_error_docref(NULL, E_WARNING, "Empty string supplied as input"); RETURN_FALSE; } inputbfr = xmlParserInputBufferCreateMem(source, source_len, XML_CHAR_ENCODING_NONE); if (inputbfr != NULL) { /* Get the URI of the current script so that we can set the base directory in libxml */ #if HAVE_GETCWD directory = VCWD_GETCWD(resolved_path, MAXPATHLEN); #elif HAVE_GETWD directory = VCWD_GETWD(resolved_path); #endif if (directory) { resolved_path_len = strlen(resolved_path); if (resolved_path[resolved_path_len - 1] != DEFAULT_SLASH) { resolved_path[resolved_path_len] = DEFAULT_SLASH; resolved_path[++resolved_path_len] = '\0'; } uri = (char *) xmlCanonicPath((const xmlChar *) resolved_path); } reader = xmlNewTextReader(inputbfr, uri); if (reader != NULL) { #if LIBXML_VERSION >= 20628 ret = xmlTextReaderSetup(reader, NULL, uri, encoding, options); // encoding length not checked #endif ... GDB output: USE_ZEND_ALLOC=0 ASAN_OPTIONS=detect_leaks=0 gdb -q --args /home/operac/build4/bin/php -n poc.php No symbol table is loaded. Use the "file" command. Breakpoint 1 (__asan_report_error) pending. Reading symbols from /home/operac/build4/bin/php...done. gdb-peda$ b xmlReaderForFile Breakpoint 2 at 0x42e530 gdb-peda$ r Starting program: /home/operac/build4/bin/php -n poc.php ... Breakpoint 2, 0x00007ffff5773f90 in xmlReaderForFile () from /usr/lib/x86_64-linux-gnu/libxml2.so.2 gdb-peda$ p strlen($rsi) $2 = 0x7ffffe ... Test script: --------------- poc.php: <?php ini_set('memory_limit', -1); $v = str_repeat("/", 0xffffff/2 - 1); XMLReader::open(".", $v); poc2.php: <?php ini_set('memory_limit', -1); $v = str_repeat("/", 0xffffff/2); XMLReader::xml("<xml>", $v); Expected result: ---------------- No crash Actual result: -------------- ASan output: USE_ZEND_ALLOC=0 ASAN_OPTIONS=detect_leaks=0 /home/operac/build4/bin/php -n poc.php ASAN:SIGSEGV ================================================================= ==7571==ERROR: AddressSanitizer: stack-overflow on address 0x7ffd866baf28 (pc 0x7f684a41b4f9 bp 0x7ffd86ebafd0 sp 0x7ffd866baf30 T0) #0 0x7f684a41b4f8 (/lib/x86_64-linux-gnu/libc.so.6+0x214f8) #1 0x7f684a41ae29 in iconv_open (/lib/x86_64-linux-gnu/libc.so.6+0x20e29) #2 0x7f684b14c908 in xmlFindCharEncodingHandler (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x32908) #3 0x7f684b23f1e6 in xmlReaderForFile (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x1251e6) #4 0x1668f3a in zim_xmlreader_open /home/operac/build4/php-src/ext/xmlreader/php_xmlreader.c:884 #5 0x1d74293 in ZEND_DO_FCALL_SPEC_HANDLER /home/operac/build4/php-src/Zend/zend_vm_execute.h:842 #6 0x1b9ff15 in execute_ex /home/operac/build4/php-src/Zend/zend_vm_execute.h:414 #7 0x1e4e7a8 in zend_execute /home/operac/build4/php-src/Zend/zend_vm_execute.h:458 #8 0x199ce7c in zend_execute_scripts /home/operac/build4/php-src/Zend/zend.c:1427 #9 0x170fda7 in php_execute_script /home/operac/build4/php-src/main/main.c:2494 #10 0x1e56a32 in do_cli /home/operac/build4/php-src/sapi/cli/php_cli.c:974 #11 0x46e424 in main /home/operac/build4/php-src/sapi/cli/php_cli.c:1344 #12 0x7f684a41a82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f) #13 0x46eaf8 in _start (/home/operac/build4/bin/php+0x46eaf8) SUMMARY: AddressSanitizer: stack-overflow ??:0 ?? ==7571==ABORTING USE_ZEND_ALLOC=0 ASAN_OPTIONS=detect_leaks=0 /home/operac/build4/bin/php -n poc2.php ASAN:SIGSEGV ================================================================= ==7572==ERROR: AddressSanitizer: stack-overflow on address 0x7ffee82e1f78 (pc 0x7fd94762c4f9 bp 0x7ffee8ae2020 sp 0x7ffee82e1f80 T0) #0 0x7fd94762c4f8 (/lib/x86_64-linux-gnu/libc.so.6+0x214f8) #1 0x7fd94762be29 in iconv_open (/lib/x86_64-linux-gnu/libc.so.6+0x20e29) #2 0x7fd94835d908 in xmlFindCharEncodingHandler (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x32908) #3 0x7fd94844f795 in xmlTextReaderSetup (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x124795) #4 0x166455d in zim_xmlreader_XML /home/operac/build4/php-src/ext/xmlreader/php_xmlreader.c:1086 #5 0x1d74293 in ZEND_DO_FCALL_SPEC_HANDLER /home/operac/build4/php-src/Zend/zend_vm_execute.h:842 #6 0x1b9ff15 in execute_ex /home/operac/build4/php-src/Zend/zend_vm_execute.h:414 #7 0x1e4e7a8 in zend_execute /home/operac/build4/php-src/Zend/zend_vm_execute.h:458 #8 0x199ce7c in zend_execute_scripts /home/operac/build4/php-src/Zend/zend.c:1427 #9 0x170fda7 in php_execute_script /home/operac/build4/php-src/main/main.c:2494 #10 0x1e56a32 in do_cli /home/operac/build4/php-src/sapi/cli/php_cli.c:974 #11 0x46e424 in main /home/operac/build4/php-src/sapi/cli/php_cli.c:1344 #12 0x7fd94762b82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f) #13 0x46eaf8 in _start (/home/operac/build4/bin/php+0x46eaf8) SUMMARY: AddressSanitizer: stack-overflow ??:0 ?? 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Last updated: Thu Nov 21 11:01:29 2024 UTC |
I'm testing on a updated Ubuntu x86_64 Xenial (16.04.1), it's not the last PHP release but AFAIK there has been no changes related to XMLReader to recent PHP versions: Full data environment ---- PHP -------------------------------------------- php --version PHP 7.0.8-0ubuntu0.16.04.3 (cli) ( NTS ) Copyright (c) 1997-2016 The PHP Group Zend Engine v3.0.0, Copyright (c) 1998-2016 Zend Technologies with Zend OPcache v7.0.8-0ubuntu0.16.04.3, Copyright (c) 1999-2016, by Zend Technologies ---- PHP XML --------------------------------------- Package: php7.0-xml Priority: optional Section: php Installed-Size: 468 Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com> Original-Maintainer: Debian PHP Maintainers <pkg-php-maint@lists.alioth.debian.org> Architecture: amd64 Source: php7.0 Version: 7.0.8-0ubuntu0.16.04.3 ---- libxml2 ---------------------------------------- Package: libxml2 Priority: standard Section: libs Installed-Size: 2124 Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com> Original-Maintainer: Debian XML/SGML Group <debian-xml-sgml-pkgs@lists.alioth.debian.org> Architecture: amd64 Version: 2.9.3+dfsg1-1ubuntu0.1 ---- libc ------------------------------------ Package: libc6 Priority: required Section: libs Installed-Size: 10948 Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com> Original-Maintainer: GNU Libc Maintainers <debian-glibc@lists.debian.org> Architecture: amd64 Source: glibc Version: 2.23-0ubuntu4 ---- OS -------------------------------------- cat /etc/os-release NAME="Ubuntu" VERSION="16.04.1 LTS (Xenial Xerus)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 16.04.1 LTS" VERSION_ID="16.04" HOME_URL="http://www.ubuntu.com/" SUPPORT_URL="http://help.ubuntu.com/" BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/" VERSION_CODENAME=xenial UBUNTU_CODENAME=xenial ---- Arch --------------------------------------- $ uname -a Linux hp3 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux ---- PoC --------------------------------------------- $ cat poc.php <?php ini_set('memory_limit', -1); $v = str_repeat("/", 0xffffff/2 - 1); XMLReader::open(".", $v); $ php poc.php Segmentation fault (core dumped)The reported stack overflow is certainly not a PHP bug. > encoding length not checked This is a bug, but I'm not sure whether it is a security issue. stas, what do you think? Anyway, fix would be as simple as: ext/xmlreader/php_xmlreader.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/ext/xmlreader/php_xmlreader.c b/ext/xmlreader/php_xmlreader.c index 4d4e7348c9..f920d04eb7 100644 --- a/ext/xmlreader/php_xmlreader.c +++ b/ext/xmlreader/php_xmlreader.c @@ -848,7 +848,7 @@ PHP_METHOD(xmlreader, open) char resolved_path[MAXPATHLEN + 1]; xmlTextReaderPtr reader = NULL; - if (zend_parse_parameters(ZEND_NUM_ARGS(), "p|s!l", &source, &source_len, &encoding, &encoding_len, &options) == FAILURE) { + if (zend_parse_parameters(ZEND_NUM_ARGS(), "p|p!l", &source, &source_len, &encoding, &encoding_len, &options) == FAILURE) { return; } @@ -1033,7 +1033,7 @@ PHP_METHOD(xmlreader, XML) xmlParserInputBufferPtr inputbfr; xmlTextReaderPtr reader; - if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|s!l", &source, &source_len, &encoding, &encoding_len, &options) == FAILURE) { + if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|p!l", &source, &source_len, &encoding, &encoding_len, &options) == FAILURE) { return; }