RCTF 2018线上赛 writeup

sha256enc = "087e72033b1eacecd78845563696b9a449015aeb29a12b0f49c969cafababbb2"
key = "DPgOJtFiF9euj7HX"

for i in strlist:
    code = i[0]+i[1]+i[2]+i[3]
    encinfo = hashlib.sha256(code+key).hexdigest()
    if encinfo == sha256enc:
        print code
        break

#!/usr/bin/env python
# coding=utf-8
# author:401219180
import time
import socket
import string
import re
import itertools
import hashlib


def returnmsg(data):
    """发送与接收,代替nc"""
    s.send(data)
    time.sleep(1.5)
    msg = s.recv(2048)
    return msg


def createTree(inputstr, dictree):
    """对比集合列表得出a，b生成字典"""
    inputlist = inputstr.split(" ")
    newdictree = {}
    for x in dictree:
        a, b = 0, 0
        for i in range(4):
            if inputlist[i] == x[i]:
                a += 1
                continue
            if inputlist[i] in x:
                b += 1
                continue
        newdictree[x] = a, b
    return newdictree


def createList(dic, result):
    """集合字典里面生成有效集合列表"""
    numlist = []
    for k, v in dic.iteritems():
        if v == result:
            numlist.append(k)
    return numlist


def listvalueTostr(listindex):
    """生成要猜的值"""
    inputstr = listindex[0] + " " + listindex[1] + " " + listindex[2] + " " + listindex[3]
    return inputstr


# 建立nc连接
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("149.28.139.172", 10002))
time.sleep(1)
firstinfo = s.recv(1024)
r = r‘\+(.*?)\)‘
key = re.findall(r, firstinfo)[0]
sha256enc = firstinfo[-78:-14]
print key
print sha256enc

# sha256碰撞,得出xxxx的值
code = ‘‘
strlist = itertools.product(string.letters + string.digits, repeat=4)

for i in strlist:
    code = i[0] + i[1] + i[2] + i[3]
    encinfo = hashlib.sha256(code + key).hexdigest()
    if encinfo == sha256enc:
        print code
        break

print returnmsg(code)

r1 = r‘Nope. (.*?)\n‘ # 正则用于匹配Nope的值


def startgame():
    # 初始化列表
    while 1:  # 打通关了才知道连续大战8回合,所以干脆写个无限循环
        numlist = []
        for i in itertools.permutations(string.digits, 4):
            numlist.append(i)
        input1 = "2 3 4 5"  # 根据本人多次测试,首轮猜2 3 4 5比猜1 2 3 4赢得几率大些Orz....
        while 1:
            dictree1 = createTree(input1, numlist)
            print "guess: " + input1
            recvdata = returnmsg(input1)
            print recvdata
            if "You got it!" in recvdata:
                break

            ab = re.findall(r1, recvdata)[0]
            numlist = createList(dictree1, eval(ab))
            try:
                input1 = listvalueTostr(numlist[0])
            except IndexError, msg:
                print msg

        if "Flag" in recvdata:  # 如果返回的信息里面有Flag,终止while循环
            break


startgame()