2018 高校运维赛 WriteUp

菜是真的菜。
就写出来一个，还是在结束后几分钟emmm
继续学吧。

MISC

Checkin

题意：验证码识别。

大概长这样

思路：
经过观察，发现每个数字/字母的形状不会改变，且无混淆。
考虑分割每个字，计算组成其形状所有符号的ASCII码总和，建立一个一一对应的映射。

首先，批量获取字符，计算其ASCii码之和。

#-*-coding :utf-8 -*-
import socket


def get_all_captcha():
    i = 36
    f = open('captcha.txt', 'a', encoding='utf-8')
    while i:
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.connect(('210.32.4.14', 13373))
        captcha = ''
        while True:
            d = s.recv(1024).decode('utf-8')
            if 'your captcha' in d:
                f.write(captcha + d)
                break
            else:
                captcha += d
        i -= 1
        print(captcha)
    f.close()


if __name__ == '__main__':
    get_all_captcha()
    f = open('captcha.txt', 'r', encoding='utf-8')
    captcha = []
    flag = 0
    for text in f:
        if 'unCAPTCHA' in text:
            flag = 1
        elif flag == 1 and 'your captcha' not in text:
            captcha.append(text.strip('\n'))
        if 'your captcha' in text:
            flag = 0
            ans = []
            while True:
                try:
                    captcha.remove('')
                except:
                    break
            su = 0
            for i in range(len(captcha[0])):
                tmp = 0
                for x in captcha:
                    if x[i] != ' ':
                        tmp += ord(x[i])
                if tmp != 0:
                    su += tmp
                if tmp == 0 and su != 0:
                    ans.append(su)
                    su = 0
            #print('\n'.join(captcha) + '\n')
            print(ans)

然后，利用dict构造一个映射

password = {3329: '0', 1498: '1', 2937: '2', 3041: '3', 2514: '4', 3406: '5', 3151: '6',
            2137: '7', 3751: '8', 3063: '9',
            2354: 'a', 3027: 'b', 2447: 'c', 3036: 'd', 2923: 'e', 2119: 'f', 4152: 'g',
            3223: 'h', 1881: 'i', 3391: 'k', 2655: 'j', 1770: 'l', 4275: 'm', 2822: 'n',
            2601: 'o', 3264: 'p', 3148: 'q', 1868: 'r', 2283: 's', 1592: 't',
            2763: 'u', 2061: 'v', 3550: 'w', 2683: 'x', 2739: 'y', 2726: 'z'}

最后，利用脚本自动提交，获得flag

#-*-coding:utf-8 -*-
import socket
import os
password = {3329: '0', 1498: '1', 2937: '2', 3041: '3', 2514: '4', 3406: '5', 3151: '6',
            2137: '7', 3751: '8', 3063: '9',
            2354: 'a', 3027: 'b', 2447: 'c', 3036: 'd', 2923: 'e', 2119: 'f', 4152: 'g',
            3223: 'h', 1881: 'i', 3391: 'k', 2655: 'j', 1770: 'l', 4275: 'm', 2822: 'n',
            2601: 'o', 3264: 'p', 3148: 'q', 1868: 'r', 2283: 's', 1592: 't',
            2763: 'u', 2061: 'v', 3550: 'w', 2683: 'x', 2739: 'y', 2726: 'z'}


def sent_captcha(s, captcha):
    captcha = captcha + '\n'
    s.send(captcha.encode('utf-8'))


def rev_captcha(s):
    f = open('captcha.txt', 'w', encoding='utf-8')
    captcha = ''
    while True:
        d = s.recv(1024).decode('utf-8')
        print(d)
        captcha += d
        if 'your captcha' in d:
            f.write(captcha)
            return captcha
        elif '{' in d:
            return True
        elif 'bad' in d or 'time' in d:
            # print(d)
            os._exit()


def solve_captache(context):
    if 'unCAPTCHA' not in context:
        context = 'A 20 rounds unCAPTCHA to get your flag! you may need a wider screen...\n' + context
    f = context.split('\n')
    # print('\n'.join(f))
    captcha = []
    flag = 0
    for text in f:
        if 'unCAPTCHA' in text:
            flag = 1
        elif flag == 1 and 'your captcha' not in text:
            captcha.append(text.strip('\n'))
        if 'your captcha' in text:
            flag = 0
            ans = []
            while True:
                try:
                    captcha.remove('')
                except:
                    break
            su = 0
            for i in range(len(captcha[0])):
                tmp = 0
                for x in captcha:
                    if x[i] != ' ':
                        tmp += ord(x[i])
                if tmp != 0:
                    su += tmp
                if tmp == 0 and su != 0:
                    ans.append(su)
                    su = 0
    #print(ans)
    a = ''.join(list(map(lambda x: password[x], ans)))
    print(a)
    return a


if __name__ == '__main__':
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect(('210.32.4.14', 13373))
    while True:
        res = rev_captcha(s)
        if res == True:
            break
        else:
            ans = solve_captache(res)
            sent_captcha(s, ans)

FLAG:
EIS{incompletely_nonautomated_private_turing_test}