源码
#! /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',port=80)
发现有三个路由分别是：
/geneSign
@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
param = urllib.unquote(request.args.get("param", ""))
action = "scan"
return getSign(action, param)
取得传递的参数param和固定的action，传入和调用getSign()函数。
/De1ta
@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())
取得传递的参数param和从cookie传递的action，sign，绕过waf()函数后，创建Task对象，并调用Exec方法，最后以json形式返回结果。
/
@app.route('/')
def index():
return open("code.txt","r").read()
获取首页源码
Task-Exec()
首先我们要通过
if (self.checkSign()):
并且两个action的判断都要满足
if "scan" in self.action:
if "read" in self.action:
因为用的是in，所以action是scanread和readscan都可行。
接下来读取flag.txt，并通过
tmpfile.write(resp)
写入result.txt给json.dumps。
self.checkSign()
满足self.checkSign()，就需要满足
hashlib.md5(secert_key + param + action).hexdigest() = self.sign
但是我们不知道secret_key的值是多少，它只存在于服务端。注意到/geneSign中已经将action定为scan，所以我们传入的param可以为flag.txtread，这样的话还是会拼接为secert_key + 'flag.txtread' + 'scan'
构建payload1：/geneSign?param=flag.txtread
得到哈希值ee67bf7b971abc8fc4bc3c3c5694563b
构建payload2：
/De1ta?param=flag.txt
Cookie: action=readscan;sign=ee67bf7b971abc8fc4bc3c3c5694563b
得到flag{bad42dee-4118-4c77-809b-9adfaa0387b7}
方法2-哈希长度扩展攻击
当md5加密参数存在用户可控变量时
(md5(secret+args); args可控)
我们可以通过手动填充args部分，添加(控制)最后一组明文，并根据上一次加密的结果逆向再和库中固定的加密轮密钥来演算出我们新添加的一组明文的加密结果，进而推出最后的新密文。
简单地说就是用户可以用过控制args变量来来控制最后的加密结果md5(....)而不需要知道secret值。
需要工具hashpump
待补充
参考链接：
https://blog.csdn.net/RABCDXB/article/details/115412359