昨天做到的一个很好的题目（个人觉得），写出来给大家看看（
打开靶机
打开靶机，直接看到源码，并且能够看到提示，flag在flag.txt内：
但是这源码也太恶心人了吧，这谁看得懂啊…
然后经过我不懈的努力（雾
把源码整理好了：
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|
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)):
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
@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')
|
审代码
接下来慢慢对代码进行审计即可：
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@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()
|
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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
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
|
获取flag
整理一下大概就是如下的思路：
通过exec函数读取flag.txt的内容，而flag.txt的内容会被scan的action存储在result.txt中
我们只需要获得read方法读取即可：
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| flag的内容可以通过scan函数储存，read函数读取-->
action中需要有readscan-->
又需要checkSign通过-->
getSign(self.action, self.param) == self.sign -->
而getsign又返回hashlib.md5(secert_key + param + action).hexdigest()-->
等价于hashlib.md5(secert_key + param + action).hexdigest()==self.sign
|
sign，action在/De1ta路由中由cookie传入，而param由get方法传入
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| action=readscan,sign=一个md5值
-->/geneSign会返回secret_key+param+scan的md5
-->param=flag.txtread，成功获取sign
-->/De1ta中param=flag.txt,action=readscan,符合checkSign，又有read和scan，就会输出flag
|
所以我们需要先访问/geneSign路由，然后param=flag.txtread
返回一个值：(055967a25e4ba3f082a3ab94e0344994)
注：这个值随每次靶机打开都是不一样的
这个值就是flag.txtreadscan的sign值：
而我们传入的参数param，action又是flag.txt、readscan，完美符合sign值
然后使用bp抓包，添加cookie，修改url即可：
结束~
另解：哈希长度拓展攻击
虽然但是我并不知道这个怎么用，在这里贴出大佬的wp吧（
略略水一篇博客没人骂我的吧~