CTF杂项——[网鼎杯 2022 玄武组]misc999

文件内容

脚本如下

BASE = 62

CHARSET_DEFAULT = '9876543210qwertyuiopasdfghjklzxcvbnmMNBVCXZLKJHGFDSAPOIUYTREWQ'
str1 = "7dFRjPItGFkeXAALp6GMKE9Y4R4BuNtIUK1RECFlU4f3PomCzGnfemFvO"

def _value(ch, charset):
    try:
        return charset.index(ch)
    except ValueError:
        raise ValueError("base62: Invalid character (%s)" % ch)
 
def decode(encoded, charset=CHARSET_DEFAULT):
    if encoded.startswith("0z"):
        encoded = encoded[2:]

    l, i, v = len(encoded), 0, 0
    for x in encoded:
        v += _value(x, charset=charset) * (BASE ** (l - (i + 1)))
        i += 1

    return v

def decodebytes(encoded, charset=CHARSET_DEFAULT):
    decoded = decode(encoded, charset=charset)
    buf = bytearray()
    while decoded > 0:
        buf.append(decoded & 0xFF)
        decoded //= 256
    buf.reverse()

    return bytes(buf)

print(decodebytes(str1))

运行得到flag