[SWPUCTF 2022 新生赛]Capture!

Problem: [SWPUCTF 2022 新生赛]Capture!

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修改高度得part1

再LSB隐写一把梭

zsteg -a flag.png #一把梭

猜测base64，无果

再颠倒顺序即可解出

[SWPUCTF 2022 新生赛]Cycle Again

Problem: [SWPUCTF 2022 新生赛]Cycle Again

先用010查看图片发现图片的宽和高为零即可知是crc爆破

再用脚本crc爆破

import binascii
import struct

# \x49\x48\x44\x52\x00\x00\x01\x00\x00\x00\x00\x00\x08\x02\x00\x00\x00
crc32key = 0x6bb7ad9c

for i in range(0, 65535):
    for j in range(0, 5000):
        width = struct.pack('>i', j)
        height = struct.pack('>i', i)
        data = b'\x49\x48\x44\x52' + width + height + b'\x08\x06\x00\x00\x00'
        crc32result = binascii.crc32(data) & 0xffffffff
        if crc32result == crc32key:
            print(''.join(map(lambda c: "%02X" % c, width)))
            print(''.join(map(lambda c: "%02X" % c, height)))


output:
00000800
00000480

即可得到part1

再用crc爆破压缩包即可获得part2

crc脚本

[SWPUCTF 2022 新生赛]Coffee Please

解压文档

使用vscode 搜索

即可得到flag

NSSCTF{8ff8a53a-9378-4e78-b54a-ef86e8c84432}

Problem: [SWPUCTF 2022 新生赛]Convert Something

[SWPUCTF 2022 新生赛]Convert Something

零宽隐写+base64隐写

零宽隐写
网站

base64隐写脚本

import base64
def get_base64_diff_value(s1, s2):
    base64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
    res = 0
    for i in range(len(s1)):
        if s1[i] != s2[i]:
            return abs(base64chars.index(s1[i]) - base64chars.index(s2[i]))
    return res

def solve_stego():
    with open('.\字频统计.txt', 'rb') as f:
        file_lines = f.readlines()
    bin_str=''
    for line in file_lines:
        steg_line = line.decode().replace('\r\n', '')
        norm_line = base64.b64encode((base64.b64decode(line))).decode()
        diff = get_base64_diff_value(steg_line, norm_line)
        pads_num = steg_line.count('=')
        if diff:
            bin_str += bin(diff)[2:].zfill(pads_num * 2)
        else:
            bin_str += '0' * pads_num * 2
    print (bin_str)
    res_str = ''
    for i in range(0, len(bin_str), 8):
        res_str += chr(int(bin_str[i:i+8], 2))
    print (res_str)

if __name__=='__main__':
    solve_stego()
    ```
    
# [SWPUCTF 2022 新生赛]Does your nc work？


>https://www.nssctf.cn/problem/2633


nc 连接签到题，注意不要用windows连接就行


# [SWPUCTF 2022 新生赛]funny_web
> Problem: [[SWPUCTF 2022 新生赛]funny_web](https://www.nssctf.cn/problem/2637)

账号NSS
密码2122693401


intval()函数用于字符串转整数，可以使十六进制转十进制用于绕过数字过滤


intval()函数绕过，可以凭借字符串拼接绕过
payload:?num=12345a