De1CTF-2019部分wp
目录
- Misc1——We1come
- Misc2——Mine Sweeping
- Web1——SSRF Me
- Crypto1——xorz
去De1CTF划了划水，发现自己是真的菜━┳━ ━┳━
Misc1——We1come
https://t.me/De1CTF ，需要加Telegram群，需要VPN,群里有发签到的flag
Misc2——Mine Sweeping
下载下来是一个扫雷游戏
在没有雷的地方组成的其实是一个二维码，因为踩雷后不会重置雷的位置，所以爆破每一个点是否有雷就可以了。表示此生不再想玩扫雷了。
最后得到了大概是这样的布局
写个脚本画出来
from PIL import Image
import random
str2=[]
with open('p.txt', 'r') as f:
str2=f.readlines()
str1=[]
for i in str2:
str1.append(i)
str1.append(i)
str1.append(i)
str1.append(i)
str1.append(i)
str1.append(i)
print(len(str1[0]))
print(len(str1))
c = Image.new("RGB",(len(str1[0]),len(str1)))
for j in range (0,len(str1)):
for i in range (0,len(str1[0])-1):
a=str1[j]
if a[i]=="1":
c.putpixel([i,j],(255,255,255))
else :
c.putpixel([i,j],(0,0,0))
c = c.resize((200, 200),Image.ANTIALIAS)
c.show()
c.save("c.png")
最后扫码得到网址，访问即可得到flag
Web1——SSRF Me
SSRF(Server-Side Request Forgery:服务器端请求伪造) 是一种由攻击者构造形成由服务端发起请求的一个安全漏洞。一般情况下，SSRF是要目标网站的内部系统。（因为他是从内部系统访问的，所有可以通过它攻击外网无法访问的内部系统，也就是把目标网站当中间人）
源码如下
#! /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)
说实话题目不是很难，就是代码有点长，要好好分析下代码逻辑。
首先可以知道，这段代码的主要的一个入口是在这里
@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())
通过访问/De1ta，会去获取cookie中的action和sign两个参数，同时还会获得一个url传参param。然后会去初始化一个Task对象，并且执行Task对象的Exec方法
然后执行Exec方法就看到调用了checkSign这个方法
def checkSign(self):
if (getSign(self.action, self.param) == self.sign):
return True
else:
return False
他会去将我们传入的sign和getSign(self.action, self.param)比较，相等才能执行后面的关键代码
def getSign(action, param):
return hashlib.md5(secert_key + param + action).hexdigest()
这个sign我们还有一个入口是可以获取的
@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
param = urllib.unquote(request.args.get("param", ""))
action = "scan"
return getSign(action, param)
所以其实我们只要之后传入的param和这个/geneSign传入的param一样，然后action也等于scan，然后拿这边返回给我们的sign是肯定可以通过checkSign的
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"
但是我们现在是要令scan和read都是action内容的一部分，才可以成功读到那边写入的数据。
def scan(param):
socket.setdefaulttimeout(1)
try:
return urllib.urlopen(param).read()[:50]
except:
return "Connection Timeout"
scan()这个方法就是访问param这个地址，将内容的前50读取出来
所以我们可以利用这个来读服务器内部的flag.txt文件
现在就是要令param等于”flag.txt”，action等于”readscan”，就可以获得flag。
所以我们需要知道的是
hashlib.md5(secert_key +”flag.txtreadscan”).hexdigest()
这个的返回值。
@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
param = urllib.unquote(request.args.get("param", ""))
action = "scan"
return getSign(action, param)
通过/geneSign可以构建，令param等于flag.txtread，然后action是scan，这样我们就能获得正确的sign
Crypto1——xorz
题目如下
from itertools import *
from data import flag,plain
key=flag.strip("de1ctf{").strip("}")
assert(len(key<38))
salt="WeAreDe1taTeam"
ki=cycle(key)
si=cycle(salt)
cipher = ''.join([hex(ord(p) ^ ord(next(ki)) ^ ord(next(si)))[2:].zfill(2) for p in plain])
print cipher
# output:
# 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
给出脚本
import string
from binascii import unhexlify, hexlify
from itertools import *
def bxor(a, b): # xor two byte strings of different lengths
if len(a) > len(b):
return bytes([x ^ y for x, y in zip(a[:len(b)], b)])
else:
return bytes([x ^ y for x, y in zip(a, b[:len(a)])])
def hamming_distance(b1, b2):
differing_bits = 0
for byte in bxor(b1, b2):
differing_bits += bin(byte).count("1")
return differing_bits
def break_single_key_xor(text):
key = 0
possible_space = 0
max_possible = 0
letters = string.ascii_letters.encode('ascii')
for a in range(0, len(text)):
maxpossible = 0
for b in range(0, len(text)):
if(a == b):
continue
c = text[a] ^ text[b]
if c not in letters and c != 0:
continue
maxpossible += 1
if maxpossible > max_possible:
max_possible = maxpossible
possible_space = a
key = text[possible_space] ^ 0x20
return chr(key)
salt = "WeAreDe1taTeam"
si = cycle(salt)
b = unhexlify(b'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')
plain = ''.join([hex(ord(c) ^ ord(next(si)))[2:].zfill(2) for c in b.decode()])
b = unhexlify(plain)
print(plain)
normalized_distances = []
for KEYSIZE in range(2, 40):
# 我们取其中前6段计算平局汉明距离
b1 = b[: KEYSIZE]
b2 = b[KEYSIZE: KEYSIZE * 2]
b3 = b[KEYSIZE * 2: KEYSIZE * 3]
b4 = b[KEYSIZE * 3: KEYSIZE * 4]
b5 = b[KEYSIZE * 4: KEYSIZE * 5]
b6 = b[KEYSIZE * 5: KEYSIZE * 6]
normalized_distance = float(
hamming_distance(b1, b2) +
hamming_distance(b2, b3) +
hamming_distance(b3, b4) +
hamming_distance(b4, b5) +
hamming_distance(b5, b6)
) / (KEYSIZE * 5)
normalized_distances.append(
(KEYSIZE, normalized_distance)
)
normalized_distances = sorted(normalized_distances, key=lambda x: x[1])
for KEYSIZE, _ in normalized_distances[:5]:
block_bytes = [[] for _ in range(KEYSIZE)]
for i, byte in enumerate(b):
block_bytes[i % KEYSIZE].append(byte)
keys = ''
try:
for bbytes in block_bytes:
keys += break_single_key_xor(bbytes)
key = bytearray(keys * len(b), "utf-8")
plaintext = bxor(b, key)
print("keysize:", KEYSIZE)
print("key is:", keys, "n")
s = bytes.decode(plaintext)
print(s)
except Exception:
continue