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// Copyright (c) 2014, 2015 Robert Clipsham <robert@octarineparrot.com>
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A TCP packet abstraction.
use crate::Packet;
use crate::PrimitiveValues;
use crate::ip::IpNextHeaderProtocols;
use alloc::{vec, vec::Vec};
use pnet_macros::packet;
use pnet_macros_support::types::*;
use pnet_base::core_net::Ipv4Addr;
use pnet_base::core_net::Ipv6Addr;
use crate::util::{self, Octets};
/// The TCP flags.
#[allow(non_snake_case)]
#[allow(non_upper_case_globals)]
pub mod TcpFlags {
/// CWR – Congestion Window Reduced (CWR) flag is set by the sending
/// host to indicate that it received a TCP segment with the ECE flag set
/// and had responded in congestion control mechanism (added to header by RFC 3168).
pub const CWR: u8 = 0b10000000;
/// ECE – ECN-Echo has a dual role, depending on the value of the
/// SYN flag. It indicates:
/// If the SYN flag is set (1), that the TCP peer is ECN capable.
/// If the SYN flag is clear (0), that a packet with Congestion Experienced
/// flag set (ECN=11) in IP header received during normal transmission
/// (added to header by RFC 3168).
pub const ECE: u8 = 0b01000000;
/// URG – indicates that the Urgent pointer field is significant.
pub const URG: u8 = 0b00100000;
/// ACK – indicates that the Acknowledgment field is significant.
/// All packets after the initial SYN packet sent by the client should have this flag set.
pub const ACK: u8 = 0b00010000;
/// PSH – Push function. Asks to push the buffered data to the receiving application.
pub const PSH: u8 = 0b00001000;
/// RST – Reset the connection.
pub const RST: u8 = 0b00000100;
/// SYN – Synchronize sequence numbers. Only the first packet sent from each end
/// should have this flag set.
pub const SYN: u8 = 0b00000010;
/// FIN – No more data from sender.
pub const FIN: u8 = 0b00000001;
}
/// Represents a TCP packet.
#[packet]
pub struct Tcp {
pub source: u16be,
pub destination: u16be,
pub sequence: u32be,
pub acknowledgement: u32be,
pub data_offset: u4,
pub reserved: u4,
pub flags: u8,
pub window: u16be,
pub checksum: u16be,
pub urgent_ptr: u16be,
#[length_fn = "tcp_options_length"]
pub options: Vec<TcpOption>,
#[payload]
pub payload: Vec<u8>,
}
/// Represents a TCP option.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct TcpOptionNumber(pub u8);
/// The TCP header options.
#[allow(non_snake_case)]
#[allow(non_upper_case_globals)]
pub mod TcpOptionNumbers {
use super::TcpOptionNumber;
/// End of Options list.
pub const EOL: TcpOptionNumber = TcpOptionNumber(0);
/// No operation.
pub const NOP: TcpOptionNumber = TcpOptionNumber(1);
/// Maximum segment size.
pub const MSS: TcpOptionNumber = TcpOptionNumber(2);
/// Window scale.
pub const WSCALE: TcpOptionNumber = TcpOptionNumber(3);
/// Selective acknowledgements permitted.
pub const SACK_PERMITTED: TcpOptionNumber = TcpOptionNumber(4);
/// Selective acknowledgment.
pub const SACK: TcpOptionNumber = TcpOptionNumber(5);
/// Timestamps.
pub const TIMESTAMPS: TcpOptionNumber = TcpOptionNumber(8);
}
/// A TCP option.
#[packet]
pub struct TcpOption {
#[construct_with(u8)]
number: TcpOptionNumber,
#[length_fn = "tcp_option_length"]
// The length field is an optional field, using a Vec is a way to implement
// it
length: Vec<u8>,
#[length_fn = "tcp_option_payload_length"]
#[payload]
data: Vec<u8>,
}
impl TcpOption {
/// NOP: This may be used to align option fields on 32-bit boundaries for better performance.
pub fn nop() -> Self {
TcpOption {
number: TcpOptionNumbers::NOP,
length: vec![],
data: vec![],
}
}
/// Timestamp: TCP timestamps, defined in RFC 1323, can help TCP determine in which order
/// packets were sent. TCP timestamps are not normally aligned to the system clock and
/// start at some random value.
pub fn timestamp(my: u32, their: u32) -> Self {
let mut data = vec![];
data.extend_from_slice(&my.octets()[..]);
data.extend_from_slice(&their.octets()[..]);
TcpOption {
number: TcpOptionNumbers::TIMESTAMPS,
length: vec![10],
data: data,
}
}
/// MSS: The maximum segment size (MSS) is the largest amount of data, specified in bytes,
/// that TCP is willing to receive in a single segment.
pub fn mss(val: u16) -> Self {
let mut data = vec![];
data.extend_from_slice(&val.octets()[..]);
TcpOption {
number: TcpOptionNumbers::MSS,
length: vec![4],
data: data,
}
}
/// Window scale: The TCP window scale option, as defined in RFC 1323, is an option used to
/// increase the maximum window size from 65,535 bytes to 1 gigabyte.
pub fn wscale(val: u8) -> Self {
TcpOption {
number: TcpOptionNumbers::WSCALE,
length: vec![3],
data: vec![val],
}
}
/// Selective acknowledgment (SACK) option, defined in RFC 2018 allows the receiver to acknowledge
/// discontinuous blocks of packets which were received correctly. This options enables use of
/// SACK during negotiation.
pub fn sack_perm() -> Self {
TcpOption {
number: TcpOptionNumbers::SACK_PERMITTED,
length: vec![2],
data: vec![],
}
}
/// Selective acknowledgment (SACK) option, defined in RFC 2018 allows the receiver to acknowledge
/// discontinuous blocks of packets which were received correctly. The acknowledgement can specify
/// a number of SACK blocks, where each SACK block is conveyed by the starting and ending sequence
/// numbers of a contiguous range that the receiver correctly received.
pub fn selective_ack(acks: &[u32]) -> Self {
let mut data = vec![];
for ack in acks {
data.extend_from_slice(&ack.octets()[..]);
}
TcpOption {
number: TcpOptionNumbers::SACK,
length: vec![1 /* number */ + 1 /* length */ + data.len() as u8],
data: data,
}
}
}
/// This function gets the 'length' of the length field of the IPv4Option packet
/// Few options (EOL, NOP) are 1 bytes long, and then have a length field equal
/// to 0.
#[inline]
fn tcp_option_length(option: &TcpOptionPacket) -> usize {
match option.get_number() {
TcpOptionNumbers::EOL => 0,
TcpOptionNumbers::NOP => 0,
_ => 1,
}
}
fn tcp_option_payload_length(ipv4_option: &TcpOptionPacket) -> usize {
match ipv4_option.get_length_raw().first() {
Some(len) if *len >= 2 => *len as usize - 2,
_ => 0,
}
}
impl TcpOptionNumber {
/// Create a new `TcpOptionNumber` instance.
pub fn new(value: u8) -> TcpOptionNumber {
TcpOptionNumber(value)
}
}
impl PrimitiveValues for TcpOptionNumber {
type T = (u8,);
fn to_primitive_values(&self) -> (u8,) {
(self.0,)
}
}
#[inline]
fn tcp_options_length(tcp: &TcpPacket) -> usize {
let data_offset = tcp.get_data_offset();
if data_offset > 5 {
data_offset as usize * 4 - 20
} else {
0
}
}
/// Calculate a checksum for a packet built on IPv4.
pub fn ipv4_checksum(packet: &TcpPacket, source: &Ipv4Addr, destination: &Ipv4Addr) -> u16 {
ipv4_checksum_adv(packet, &[], source, destination)
}
/// Calculate the checksum for a packet built on IPv4, Advanced version which
/// accepts an extra slice of data that will be included in the checksum
/// as being part of the data portion of the packet.
///
/// If `packet` contains an odd number of bytes the last byte will not be
/// counted as the first byte of a word together with the first byte of
/// `extra_data`.
pub fn ipv4_checksum_adv(packet: &TcpPacket,
extra_data: &[u8],
source: &Ipv4Addr,
destination: &Ipv4Addr)
-> u16 {
util::ipv4_checksum(packet.packet(),
8,
extra_data,
source,
destination,
IpNextHeaderProtocols::Tcp)
}
/// Calculate a checksum for a packet built on IPv6.
pub fn ipv6_checksum(packet: &TcpPacket, source: &Ipv6Addr, destination: &Ipv6Addr) -> u16 {
ipv6_checksum_adv(packet, &[], source, destination)
}
/// Calculate the checksum for a packet built on IPv6, Advanced version which
/// accepts an extra slice of data that will be included in the checksum
/// as being part of the data portion of the packet.
///
/// If `packet` contains an odd number of bytes the last byte will not be
/// counted as the first byte of a word together with the first byte of
/// `extra_data`.
pub fn ipv6_checksum_adv(packet: &TcpPacket,
extra_data: &[u8],
source: &Ipv6Addr,
destination: &Ipv6Addr)
-> u16 {
util::ipv6_checksum(packet.packet(),
8,
extra_data,
source,
destination,
IpNextHeaderProtocols::Tcp)
}
#[test]
fn tcp_header_ipv4_test() {
use crate::ip::IpNextHeaderProtocols;
use crate::ipv4::MutableIpv4Packet;
const IPV4_HEADER_LEN: usize = 20;
const TCP_HEADER_LEN: usize = 32;
const TEST_DATA_LEN: usize = 4;
let mut packet = [0u8; IPV4_HEADER_LEN + TCP_HEADER_LEN + TEST_DATA_LEN];
let ipv4_source = Ipv4Addr::new(192, 168, 2, 1);
let ipv4_destination = Ipv4Addr::new(192, 168, 111, 51);
{
let mut ip_header = MutableIpv4Packet::new(&mut packet[..]).unwrap();
ip_header.set_next_level_protocol(IpNextHeaderProtocols::Tcp);
ip_header.set_source(ipv4_source);
ip_header.set_destination(ipv4_destination);
}
// Set data
packet[IPV4_HEADER_LEN + TCP_HEADER_LEN] = 't' as u8;
packet[IPV4_HEADER_LEN + TCP_HEADER_LEN + 1] = 'e' as u8;
packet[IPV4_HEADER_LEN + TCP_HEADER_LEN + 2] = 's' as u8;
packet[IPV4_HEADER_LEN + TCP_HEADER_LEN + 3] = 't' as u8;
{
let mut tcp_header = MutableTcpPacket::new(&mut packet[IPV4_HEADER_LEN..]).unwrap();
tcp_header.set_source(49511);
assert_eq!(tcp_header.get_source(), 49511);
tcp_header.set_destination(9000);
assert_eq!(tcp_header.get_destination(), 9000);
tcp_header.set_sequence(0x9037d2b8);
assert_eq!(tcp_header.get_sequence(), 0x9037d2b8);
tcp_header.set_acknowledgement(0x944bb276);
assert_eq!(tcp_header.get_acknowledgement(), 0x944bb276);
tcp_header.set_flags(TcpFlags::PSH | TcpFlags::ACK);
assert_eq!(tcp_header.get_flags(), TcpFlags::PSH | TcpFlags::ACK);
tcp_header.set_window(4015);
assert_eq!(tcp_header.get_window(), 4015);
tcp_header.set_data_offset(8);
assert_eq!(tcp_header.get_data_offset(), 8);
let ts = TcpOption::timestamp(743951781, 44056978);
tcp_header.set_options(&vec![TcpOption::nop(), TcpOption::nop(), ts]);
let checksum = ipv4_checksum(&tcp_header.to_immutable(), &ipv4_source, &ipv4_destination);
tcp_header.set_checksum(checksum);
assert_eq!(tcp_header.get_checksum(), 0xc031);
}
let ref_packet = [0xc1, 0x67, /* source */
0x23, 0x28, /* destination */
0x90, 0x37, 0xd2, 0xb8, /* seq */
0x94, 0x4b, 0xb2, 0x76, /* ack */
0x80, 0x18, 0x0f, 0xaf, /* length, flags, win */
0xc0, 0x31, /* checksum */
0x00, 0x00, /* urg ptr */
0x01, 0x01, /* options: nop */
0x08, 0x0a, 0x2c, 0x57,
0xcd, 0xa5, 0x02, 0xa0,
0x41, 0x92, /* timestamp */
0x74, 0x65, 0x73, 0x74 /* "test" */
];
assert_eq!(&ref_packet[..], &packet[20..]);
}
#[test]
fn tcp_test_options_invalid_offset() {
let mut buf = [0; 20]; // no space for options
{
if let Some(mut tcp) = MutableTcpPacket::new(&mut buf[..]) {
tcp.set_data_offset(10); // set invalid offset
}
}
if let Some(tcp) = TcpPacket::new(&buf[..]) {
let _options = tcp.get_options_iter(); // shouldn't crash here
}
}
#[test]
fn tcp_test_options_vec_invalid_offset() {
let mut buf = [0; 20]; // no space for options
{
if let Some(mut tcp) = MutableTcpPacket::new(&mut buf[..]) {
tcp.set_data_offset(10); // set invalid offset
}
}
if let Some(tcp) = TcpPacket::new(&buf[..]) {
let _options = tcp.get_options(); // shouldn't crash here
}
}
#[test]
fn tcp_test_options_slice_invalid_offset() {
let mut buf = [0; 20]; // no space for options
{
if let Some(mut tcp) = MutableTcpPacket::new(&mut buf[..]) {
tcp.set_data_offset(10); // set invalid offset
}
}
if let Some(tcp) = TcpPacket::new(&buf[..]) {
let _options = tcp.get_options_raw(); // shouldn't crash here
}
}
#[test]
fn tcp_test_option_invalid_len() {
use std::println;
let mut buf = [0; 24];
{
if let Some(mut tcp) = MutableTcpPacket::new(&mut buf[..]) {
tcp.set_data_offset(6);
}
buf[20] = 2; // option type
buf[21] = 8; // option len, not enough space for it
}
if let Some(tcp) = TcpPacket::new(&buf[..]) {
let options = tcp.get_options_iter();
for opt in options {
println!("{:?}", opt);
}
}
}
#[test]
fn tcp_test_payload_slice_invalid_offset() {
let mut buf = [0; 20];
{
if let Some(mut tcp) = MutableTcpPacket::new(&mut buf[..]) {
tcp.set_data_offset(10); // set invalid offset
}
}
if let Some(tcp) = TcpPacket::new(&buf[..]) {
assert_eq!(tcp.payload().len(), 0);
}
}