XCTF 2ex1

一个mips架构大端序的程序，还有一个密文

运行下程序看看

一开始我没想出解题思路，看了大佬的wp，大佬一眼看出这是被替换了????表的base64加密
ghidra打开加解二进制文件

找到了一个足够64位的奇怪的字符串

@,.1fgvw#`/2ehux$~"3dity%_;4cjsz^+{5bkrA&=}6alqB*-[70mpC()]89noD

解密脚本

d = ""
ret = ""
string = "│_r-+_Cl5;vgq_pdme7#7eC0=".replace("=","")
base64_list = '@,.1fgvw#`/2ehux$~"3dity%_;4cjsz^+{5bkrA&=}6alqB*-[70mpC()]89noD'

for i in string:
	try:
		d += str(bin(base64_list.index(i))[2:]).rjust(6,"0")
	except Exception as e:
		continue
for i in range(0,len(d),8):
	if 32 <= int(d[i:i+8],2) <= 126:
		ret += chr(int(d[i:i+8],2))
print(ret)

flag

flag{change53233}