百度杯十一月Reverse03的checkflag代码

最新推荐文章于 2021-01-06 23:14:16 发布

Flying_Fatty

最新推荐文章于 2021-01-06 23:14:16 发布

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分类专栏： CTF之旅 reverse

本文链接：https://blog.youkuaiyun.com/kevin66654/article/details/56841692

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本文介绍了一种使用Python实现的标志检测算法，该算法通过特定的位运算验证输入的标志是否正确，并根据标志的不同部分修改矩阵中的特定值来进一步验证标志的有效性。文章详细展示了算法的实现过程，包括初始化矩阵、标志映射到矩阵、标志检测函数等关键步骤。

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import sys

def debug():
    global a
    for i in range(0,9):
        for j in range(0,9):
            if a[i][j][0] == 0xFFEEFFEE:
                print '0',
            elif a[i][j][0] == 0xFEFEFEFE:
                print '1',
            elif a[i][j][0] == 0xEFEFEFEF:
                print '2',
            elif a[i][j][0] == 0xEEFFEEFF:
                print '3',
        print

def check():
    global a
    count = 0
    for i in range(0,9):
		for j in range(0,9):
			count = (count + a[i][j][0]) & 0xFFFFFFFF
    if count == 0xFC9CFC4D:
        return True
    else:
        return False

def init():
    global a
    for i in range(0,9):
        for j in range(0,9):
    		a[i][j][0] = 0xFFEEFFEE
    		a[i][j][2] = a[i][j][4] = 0xEFEFEFEF
    		if i == 0:
      			a[i][j][1] = 0xFEFEFEFE
    		else:
      			a[i][j][1] = 0xEFEFEFEF
    		if j == 0:
      			a[i][j][3] = 0xFEFEFEFE
    		else:
      			a[i][j][3] = 0xEFEFEFEF
    s = 'b1ngzl'
    for i in s:
        x = (ord(i) / 16) % 9
        y = (ord(i) % 16) % 9
        a[x][y][0] = 0xEEFFEEFF

def checkflag(s):
    global a
    global num
    length = len(s) ^ 4
    for i in range(length):
        x = (ord(s[i]) / 16) % 9
        y = (ord(s[i]) % 16) % 9
        if a[x][y][1] != 0xFEFEFEFE:
            a[x-1][y][0] = a[x-1][y][0] ^ 0x11111111
        if a[x][y][2] != 0xFEFEFEFE:
            a[x+1][y][0] = a[x-1][y][0] ^ 0x11111111
        if a[x][y][3] != 0xFEFEFEFE:
            a[x][y-1][0] = a[x-1][y][0] ^ 0x11111111
        if a[x][y][4] != 0xFEFEFEFE:
            a[x][y+1][0] = a[x-1][y][0] ^ 0x11111111
    if check() == True:
        print 'flag is right'
    else:
        print 'flag is wrong'

if __name__ == '__main__':
    a = [[[0] * 10 for i in range(10)] for j in range(10)]
    init()
    flag = '34567DEFG1234'
    checkflag(flag)
    debug()