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Packet Spoofing using Libnet (Issue)

This is a discussion on Packet Spoofing using Libnet (Issue) within the Networking/Device Communication forums, part of the General Programming Boards category; I am doing packet spoofing but getting an issue. I am capturing packet using SOCK_RAW, working with the TCP packets. ...

  1. #1
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    Packet Spoofing using Libnet (Issue)

    I am doing packet spoofing but getting an issue.

    I am capturing packet using SOCK_RAW, working with the TCP packets. doing Ethernet spoofing or just packet spoofing using LIBNET.

    1 - Used RAW socket to start Sniffing
    2 - When receive packet with SYN flag
    - - then send a packet with SYN+ACK flags to complete second way of handshake of TCP connection
    - - it is desirable that the receiver of the SYN+ACK packet must reply with an ACK packet to complete the handshake, but it is rather sending RESET flagged packet.

    I am using following functions of Libnet in given order

    libnet_init();
    libnet_build_tcp_options();
    libnet_build_tcp();
    libnet_build_ipv4();
    libnet_build_ethernet();
    libnet_write();
    libnet_destroy();

    I am using temporary window size say it 500 in libnet_build_tcp(), while I am using some the string "\003\003\012\001\002\004\001\011\010\012\077\077\ 077\077\000\000\000\000\000\000" as tcp options in libnet_build_tcp_options().

    Please tell where the problem is

  2. #2
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    It's not spoofing, it's just forging the packets. I've done similar things before (only without Libnet, just crafting the packets manually).

    Either way, post your code or we can't help.

    EDIT: RAW sockets don't usually work for ethernet header modification. Unless you use a PF_PACKET (linux) or BPF (mac) socket, the ethernet header will already be there.
    rehman12390 likes this.

  3. #3
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    Code Issue

    I have tried this using two ways:

    1-libnet
    2-bsd socket i.e. sendto() function.

    the problem still lies, I am not receiving the ACK flagged packet after sending the SYN+ACK packet.

    the two codes are attached, the second code is rough i.e. too much unnecessary thing in there, I was just testing that, just get the main idea
    Attached Files Attached Files

  4. #4
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    I haven't seen the entire code, but there's two things that look problematic:

    Code:
    ip.ip_src.s_addr = inet_addr("172.17.13.90");
    Using your external IP is a bad idea for two reasons: it's likely to change, and it doesn't work. Instead, use your local IP (and ioctls to find it), and then your router will convert it into the external IP.

    Code:
    if ((size_Buffer = recvfrom(SOCK_RAW, Buffer, MAX_BUFFER_SIZE, 0, NULL, NULL)) < 0){
    You're not receiving from the socket, you're receiving from SOCK_RAW, which isn't anything. Instead, pass the socket.

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