"CoolShell puzzle game" writeup

地址：http://fun.coolshell.cn/

0. Fuck your brain
   看到一大串符号，还以为是 js 代码，结果放到 Chrome 控制台执行没有任何结果，然后搜了一下发现有一门叫Brainfuck的编程语言，醉了，用官网提供的编译器把那串代码编译执行一下就出结果了，答案是“welcome.html”

1. Multiply
   2, 3, 6, 18, 108. ? 看到这一串数字很容易得到 ? = 18*108 = 1944，放到 URL 里试试，提示Yes, one of the answers is 1944，嗯……下面还有一句话，“生命、宇宙以及任何事情的终极答案”，直接谷歌了一下，说是42，好吧我信了，那么答案就是这两个数的乘积了，1944*42 = 81648

2. Keyboard
   有一张键盘的图片和一段代码，点击图片会跳转到维基百科关于 Dvorak 键盘的介绍，猜测可能是与QWERTY键盘的键位转换，可以手动转换也可以使用在线工具转换，转换后的代码是main() { printf(&unix["21%six12"],(unix)["have"]+"fun"-0x60);}，用 gcc 编译执行可以得到结果“unix”，当然，也可以手动分析试试，可以参考http://blog.csdn.net/lisonglisonglisong/article/details/38404973

3. QR Code
   出现一个二维码和一段文字，扫描二维码可得[abcdefghijklmnopqrstuvwxyz] <=> [pvwdgazxubqfsnrhocitlkeymj],看来下面的文字是密文，而这是加密方式，逆向解密得“chere there is a shell, there is a way. s expect you use the shell command to solve this problem, now, please try using the rot13 of "shell" to enter next level.”答案就是“shell”的rot13变换，即“furyy”。
   解密用的 Python 代码如下。

    #!/usr/bin/env python3

    s = 'Wxgcg txgcg ui p ixgff, txgcg ui p epm. I gyhgwt mrl lig txg ixgff wrsspnd tr irfkg txui hcrvfgs, nre, hfgpig tcm liunz txg crt13 ra "ixgff" tr gntgc ngyt fgkgf.'
    result = ''
    letter1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
    letter2 = ['p', 'v', 'w', 'd', 'g', 'a', 'z', 'x', 'u', 'b', 'q', 'f', 's', 'n', 'r', 'h', 'o', 'c', 'i', 't', 'l', 'k', 'e', 'y', 'm', 'j']
    for item in s.lower():
        if item in letter2:
            result +=  letter1[letter2.index(item)]
        else:
            result += item
    print(result)

4. cat
   首先，标题是“Palindrome”，意思是“回文”，然后图片左侧有一些字符串，符合回文的特征，“c”,“a”，“t”三个字母标红了，试了试“cat”，果然不对……继续看下面“The answer has been lost in the source”，难道是让查看源码的意思吗？F12走起，然后就发现这句话下面隐写了“Notes: it's case-sensitive!”，嗯……大小写敏感，指的应该是答案或者是回文字符串吧，继续看源码就发现，注释里有一大坨字符串，这TM是啥啊……
   
   只能从“回文”考虑了，用正则表达式找一下这一坨字符串里的回文字符串，正则表达式是([A-Z])([0-9])[a-z](2)(1)|([0-9])([A-Z])[a-z](6)(5)，放到http://tool.oschina.net/regex做一下匹配，得到

共找到 9 处匹配：
E1v1E
4FaF4
9XrX9
O3i3O
0MaM0
4GbG4
M5l5M
0WeW0
Y0s0Y

嗯……感觉还需要再处理一下，根据“cat”三个字母标红的未知，取每行中间的字母，凑出了“variables”这个单词，试了试，正确！

5. variables
   点击图片会打开http://fun.coolshell.cn/n/2014这个链接，显示一个数字，用这个数字替换链接中的“2014”，打开该链接又会显示一个数字，根据提示“Keep going, you will find the result...”，只要这样一直找下去，就会得到答案，简单写个脚本跑一下，一会就能得到结果，Cool! the next level is "tree"。

    #!/usr/bin/env python3

    import requests
    n = "2014"
    while True:
        url = "http://fun.coolshell.cn/n/" + n
        r = requests.get(url)
        num = r.content.decode("utf-8")
        print(num)
        n = num

6. tree
   给了二叉树的中序遍历和后序遍历，那么就可以还原出这颗二叉树，然后这棵树的最深路径就是下面那段密文的密钥，相关代码如下

    #!/usr/bin/env python3

    class TreeNode(object):
        def __init__(self, x):
            self.val = x
            self.left = None
            self.right = None

    def buildFromInorderPostorder(postorder, inorder):
        length = len(postorder)
        if length == 0:
            return None
        root_val = postorder[-1]
        root_node = TreeNode(root_val)
        offset = inorder.index(root_val)
        root_node.left = buildFromInorderPostorder(postorder[:offset], inorder[:offset])
        root_node.right = buildFromInorderPostorder(postorder[offset:-1], inorder[offset+1:])
        return root_node

    def deepestPath(root_node):
        if root_node == None:
            return []
        else:
            leftDeepestPath = deepestPath(root_node.left)
            rightDeepestpath = deepestPath(root_node.right)
            return [root_node.val] + (leftDeepestPath if len(leftDeepestPath) > len(rightDeepestpath) else rightDeepestpath)

    if __name__ == '__main__':
        inorder = ["T", "b", "H", "V", "h", "3", "o", "g", "P", "W", "F", "L", "u", "A", "f", "G", "r", "m", "1", "x", "J", "7", "w", "e", "0", "i", "Q", "Y", "n", "Z", "8", "K", "v", "q", "k", "9", "y", "5", "C", "N", "B", "D", "2", "4", "U", "l", "c", "p", "I", "E", "M", "a", "j", "6", "S", "R", "O", "X", "s", "d", "z", "t"]
        postorder = ["T", "V", "H", "o", "3", "h", "P", "g", "b", "F", "f", "A", "u", "m", "r", "7", "J", "x", "e", "w", "1", "Y", "Q", "i", "0", "Z", "n", "G", "L", "K", "y", "9", "k", "q", "v", "N", "D", "B", "C", "5", "4", "c", "l", "U", "2", "8", "E", "I", "R", "S", "6", "j", "d", "s", "X", "O", "a", "M", "p", "W", "t", "z"]
        root_node = buildFromInorderPostorder(postorder, inorder)
        print(deepestPath(root_node))

得到这棵树的最深路径：'z', 'W', 'p', '8', 'L', 'G', 'n', '0', '1', 'w', 'x', 'J', '7'
然后用它来解密密文

echo U2FsdGVkX1+gxunKbemS2193vhGGQ1Y8pc5gPegMAcg= | openssl enc -aes-128-cbc -a -d -pass pass:zWp8LGn01wxJ7

得到答案“nqueens”

7. N Queens
   经典的 N 皇后问题，网上有大量解法，找到一个修改如下

    #!/usr/bin/env python3
    # N queens
    # From: http://blog.csdn.net/gaoyingju/article/details/6725532

    def conflict(state, nextX):
        nextY = len(state)
        for i in range(nextY):
            if abs(state[i]-nextX) in (0, nextY - i):
                return True
        return False

    def queens(num=8, state=()):
        for pos in range(num):
            if not conflict(state,pos):
                if len(state) == num - 1:
                    yield (pos,)
                else:
                    for result in queens(num, state + (pos,)):
                        yield (pos,) + result

    # 求符合条件的code
    import hashlib
    for solution in queens(9):
        code = "".join(str(s+1) for s in solution)
        sha = hashlib.sha1(("zWp8LGn01wxJ7" + code + "
").encode("utf-8"))
        if sha.hexdigest() == "e48d316ed573d3273931e19f9ac9f9e6039a4242":
            print("Success! " + code)
            break

得到答案“953172864”

8. Excel Column
   把字母串转化为数字，类似与进制转换，很容易找到规律，比如 ABC=1*26^2+2*26^1+3*26^0，同理

    COOLSHELL = 3*26^8+15*26^7+15*26^6+12*26^5+19*26^4+8*26^3+5*26^2+12*26^1+12 = 751743486376
    SHELL = 19*26^4+8*26^3+5*26^2+12*26^1+12 = 8826856

数字比较大可以直接粘到谷歌搜索框里计算
因此，COOLSHELL / SHELL = 751743486376 / 8826856 = 85165，再将其转化为对应的字母串，代码如下

    #!/usr/bin/env python3
    letters = [chr(i) for i in range(65, 91)]
    def intToletters(n):
        result = ""
        while n > 0:
            result  = letters[n%26-1] + result
            n = int(n/26)
        return result

    if __name__ == '__main__':
        print(intToletters(85165))

答案是“DUYO”

9. Fraternal Organisation
   乍一看题不知所谓……看下面那一串字符应该是密文。然后密钥就是从两张图片下手了，题目说找到两张图片的关系就很简单了，直接用 Google 图片搜索，第一张搜出来是“pigpen”，第二张是“Freemasonry”，然后把它俩和“加密”组合作为关键词搜索，发现猪圈密码这个有意思的加密方法，对照密钥就可以解密出原文了，答案是“helloworld”,注意小写才能顺利进入下一页面

通关！