一个源码阅读,这个是python的一个web框架,叫flask。
#! /usr/bin/env python
#encoding=utf-8
from flask import Flask
from flask import request
import socket
import hashlib
import urllib
import sys
import os
import json
reload(sys)
sys.setdefaultencoding('latin1')
app = Flask(__name__)
secert_key = os.urandom(16)
class Task:
def __init__(self, action, param, sign, ip):
self.action = action
self.param = param
self.sign = sign
self.sandbox = md5(ip)
if(not os.path.exists(self.sandbox)): #SandBox For Remote_Addr
os.mkdir(self.sandbox)
def Exec(self):
result = {}
result['code'] = 500
if (self.checkSign()):
if "scan" in self.action:
tmpfile = open("./%s/result.txt" % self.sandbox, 'w')
resp = scan(self.param)
if (resp == "Connection Timeout"):
result['data'] = resp
else:
print resp
tmpfile.write(resp)
tmpfile.close()
result['code'] = 200
if "read" in self.action:
f = open("./%s/result.txt" % self.sandbox, 'r')
result['code'] = 200
result['data'] = f.read()
if result['code'] == 500:
result['data'] = "Action Error"
else:
result['code'] = 500
result['msg'] = "Sign Error"
return result
def checkSign(self):
if (getSign(self.action, self.param) == self.sign):
return True
else:
return False
#generate Sign For Action Scan.
@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
param = urllib.unquote(request.args.get("param", ""))
action = "scan"
return getSign(action, param)
@app.route('/De1ta',methods=['GET','POST'])
def challenge():
action = urllib.unquote(request.cookies.get("action"))
param = urllib.unquote(request.args.get("param", ""))
sign = urllib.unquote(request.cookies.get("sign"))
ip = request.remote_addr
if(waf(param)):
return "No Hacker!!!!"
task = Task(action, param, sign, ip)
return json.dumps(task.Exec())
@app.route('/')
def index():
return open("code.txt","r").read()
def scan(param):
socket.setdefaulttimeout(1)
try:
return urllib.urlopen(param).read()[:50]
except:
return "Connection Timeout"
def getSign(action, param):
return hashlib.md5(secert_key + param + action).hexdigest()
def md5(content):
return hashlib.md5(content).hexdigest()
def waf(param):
check=param.strip().lower()
if check.startswith("gopher") or check.startswith("file"):
return True
else:
return False
if __name__ == '__main__':
app.debug = False
app.run(host='0.0.0.0')
先看路径,有
整理一下思路:
1.访问/De1ta这个url,执行challenge()函数,需要给cookies设置action
和sign
,给url传param
def challenge():
action = urllib.unquote(request.cookies.get("action"))
param = urllib.unquote(request.args.get("param", ""))
sign = urllib.unquote(request.cookies.get("sign"))
ip = request.remote_addr
if(waf(param)):
return "No Hacker!!!!"
task = Task(action, param, sign, ip)
return json.dumps(task.Exec())
2.challenge()会将这些传给一个Task对象,然后执行Exec()
def Exec(self):
result = {}
result['code'] = 500
if (self.checkSign()):
if "scan" in self.action:
tmpfile = open("./%s/result.txt" % self.sandbox, 'w')
resp = scan(self.param)
if (resp == "Connection Timeout"):
result['data'] = resp
else:
print resp
tmpfile.write(resp)
tmpfile.close()
result['code'] = 200
if "read" in self.action:
f = open("./%s/result.txt" % self.sandbox, 'r')
result['code'] = 200
result['data'] = f.read()
if result['code'] == 500:
result['data'] = "Action Error"
else:
result['code'] = 500
result['msg'] = "Sign Error"
return result
3.Exec()会执行checkSign(),checkSign()会执行getSign()
def checkSign(self):
if (getSign(self.action, self.param) == self.sign):
return True
else:
return False
4.getSign()会secert_key + param + action进行加密后返回,当这个返回值等于sign时即可
def getSign(action, param):
return hashlib.md5(secert_key + param + action).hexdigest()
5.访问/geneSign这个url会执行geneSign()和返回getSign()而它已经把action = "scan"
指定了,所以我们只能在param上做文章。
@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
param = urllib.unquote(request.args.get("param", ""))
action = "scan"
return getSign(action, param)
6.为什么要做文章,因为Exec()中会对action进行判断,我们需要令action中同时有read和scan,但这里已经限定了action="scan"
,所以我们需要在param传值时尾部再增加一个read。
方法一:
中规中矩按步骤即可getflag
/geneSign?param=flag.txtread
取得sign=ebd2ea765b49b20beef3faefdd9b30bf/De1ta?param=flag.txt
action=readscan;sign=ebd2ea765b49b20beef3faefdd9b30bf
作为cookie{"code": 200, "data": "flag{dfdd3b97-e1c3-45ec-a9c6-95e3f8d59715}\n"}
方法二:
/geneSign?param=flag.txt
取得sign=38a9e9012b331e9100bf6805d9e1db9d/De1ta?param=flag.txt
action=scan%80%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%e0%00%00%00%00%00%00%00read;sign=73f8d9f96425377f56f05c594655682f
作为cookie这个操作称为哈希扩展攻击。
使用hashpump:
前面有提示secert_key = os.urandom(16)
然后将上面一行输出作为sign,下面一行替换掉\x
->%
作为action,即可getflag
本文原创于HhhM的博客,转载请标明出处。
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