技術標籤：wp

參考文章：Flask框架快速入門學習

#! /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')

總的來看，有三個路由，分別對應'/'讀取code.txt，'/De1ta'獲取三個引數action,param,sign,並且傳入四個引數給task的構造方法，並將task類的task.Exec()方法執行輸出。"/geneSign"將一些引數加密。
task類中，Exec方法很關鍵：
首先呼叫checkSign()即驗證self.action, self.param是否會等於sign，然後再根據action中如果有scan，則掃描目錄，如果有read，則讀取檔案。也就是說action必須包含scan和read才能讀取param的檔案
問題來了，如何繞過checkSign()

if (getSign(self.action, self.param) == self.sign):
            return True

也就是說action和param getSign()處理後的值要等於sign

def getSign(action, param):
    return hashlib.md5(secert_key + param + action).hexdigest()

得想辦法提前得到我們需要的sign
首先param要為flag.txt和scan要包含readscan是已知的，那麼secert_key呢？我們無法得知
再看看geneSign()方法，直接計算好了getSign(action, param)

@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
    param = urllib.unquote(request.args.get("param", ""))
    action = "scan"
    return getSign(action, param)

所以我們構造payload
/geneSign?param=flag.txtread
預設action=scan
所以將得到secert_key +"flag.txtreadscan"的加密值，也就是我們需要的sign值6d96187919a7b931872af4b1331dfeb9

接下來構造payload

/De1ta?param=flag.txt
Cookie:action=readscan;sign=6d96187919a7b931872af4b1331dfeb9