[原创]第二题南冥神功解题-CTF对抗-看雪-安全社区|安全招聘|kanxue.com

[原创]第二题南冥神功解题

发表于: 2021-5-11 18:27 4863

[原创]第二题南冥神功解题

lynnux

2021-5-11 18:27

4863

是10x9数列，IDA分析看样子要求对所有为0的字节填1就OK了，把数据列出来，分析每次仅能移动1行1列，可以斜着，最后发现路径如图，找路径都找了半天，不过非常有趣啊！

然后上python代码爆破：

发现结果GJ0V4LA4VKEVQZSVCNGJ00N，还有另外一条路径见图，所以至少有两个值。

'''
一个char分两次操作
第1次值为5 -  (index_in_string + index) %6
第2次值为(index + index_in_string / 6) % 6
{
0x53, 0x00, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01, 0x01,
0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00,
0x00, 0x00, 0x01, 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00,
0x00, 0x01, 0x01, 0x00, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00,
0x00, 0x00, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01, 0x01,
0x01, 0x01, 0x00, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01,
0x00, 0x00, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01,
0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01,
0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01, 0x01, 0x00, 0x00
};
'''
 
road = [[0, 1], [1, 2], [2, 1], [2, 0], [3, 0], [4, 0], [4, 1],

        [5, 2], [6, 1], [6, 0], [7, 0], [8, 0],

        [8, 1], [8, 2], [7, 3], [7, 4], [8, 4], [8, 5], [7, 6],

        [6, 6], [5, 6], [4, 6], [3, 6], [3, 5], [4, 4],

        [4, 3], [3, 3], [2, 3], [1, 3], [0, 3], [0, 4], [1, 5],

        [1, 6], [0, 6], [0, 7], [1, 8], [1, 9], [2, 9],

        [3, 9], [3, 8], [4, 7], [5, 8], [6, 8], [7, 8], [8, 8], [8, 9]]

string = b'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
 
def target_value(row, column, current_row):

    target = 0

    if row == 0:

        if column < 0:

            target = 4

        elif column > 0:

            target = 1

        else:

            print("error")

    elif row > 0:

        if column > 0:

            target = 2

        elif column < 0:

            target = 3

        else:

            # print("error1")

            if current_row & 1 == 0:

                target = 2

            else:

                target = 3

    elif row < 0:

        if column > 0:

            target = 0

        elif column < 0:

            target = 5

        else:

            # print("error2")

            if current_row & 1 == 0:

                target = 0

            else:

                target = 5

    return target
 
def calc(r1, r2):

    row = r2[0] - r1[0]

    column = r2[1] - r1[1]

    return target_value(row, column, r2[0])
 
def search_char(index, v1, v2):

    for index_in_string, s in enumerate(string):

        if v1 == (5 - (index_in_string + index) % 6):

            if v2 == ((index + index_in_string // 6) % 6):

                return chr(s)
 
output = ""

last = [0, 0]

for i in range(len(road) // 2):

    v1 = calc(last, road[i*2])

    v2 = calc(road[i*2], road[i*2+1])

    last = road[i*2 + 1]

    output += search_char(i, v1, v2)
 
print(output)