[stack][ENTRY_UDP] process handshake initialization packets

quicktap-cli/Cargo.toml

@@ -7,3 +7,7 @@ edition = "2021"
 
 [dependencies]
 quicktap = { path = "../quicktap", version = "0.1.0" }
+clap = { version = "4.0.29", features = ["derive"]}
+daemonize = "0.4.1"
+log = "0.4.17"
+simple_logger = "4.0.0"

quicktap-cli/README.md

@@ -0,0 +1,20 @@
+# Quicktap CLI
+This is a WireGuard xplatform implementation for using [Quicktap Engine](../quicktap/README.md) with as many platforms as possible.
+
+Here's a support table for the CLI:
+
+|         | IPv4          | IPv6          |
+|---------|---------------|---------------|
+| Linux   | ✓             | ✓             |
+| NetBSD  | ⚠<sup>‡</sup> | x<sup>‡</sup> |
+| MacOS   | x<sup>†</sup> | x<sup>†</sup> |
+| Windows | x<sup>†</sup> | x<sup>†</sup> |
+
+Key:
+- ✓ - Fully supported
+- ⚠ - Partially supported
+- x - Not supported
+- ‡ - Support planned
+- † - Unmaintained
+
+Help is wanted! Improve existing implementations or pick out an unmaintained or unsupported one and help the project get better.

quicktap-cli/src/cli.rs

@@ -0,0 +1,9 @@
+use clap::{ArgAction, Parser};
+
+#[derive(Parser)]
+#[command(author = "The Quicktap Maintainers", version, about = "A userspace WireGuard implementation written in Rust", long_about = None)]
+pub struct Cli {
+    #[arg(short, long, action = ArgAction::SetTrue)]
+    pub foreground: bool,
+    pub interface_name: String
+}

quicktap-cli/src/command.rs

@@ -0,0 +1,45 @@
+use std::error::Error;
+use std::io;
+use std::os::unix::net::SocketAddr;
+use std::os::unix::net::{UnixListener, UnixStream};
+
+pub enum PacketThreadCommand {
+    UpdateConfig(UpdateConfigCommand),
+    Stop
+}
+
+pub struct UpdateConfigCommand {}
+
+pub struct CommandClient {
+    stream: UnixStream,
+    addr: SocketAddr,
+    current_command: CommandType
+}
+pub enum CommandType {
+    WaitingForCommand,
+    Read,
+    Write
+}
+
+pub fn command_handler(listener: UnixListener) -> Result<(), Box<dyn Error>> {
+    listener.set_nonblocking(true)?;
+
+    let mut clients: Vec<CommandClient> = vec![];
+
+    match listener.accept() {
+        Ok((stream, addr)) => {
+            clients.push(CommandClient { stream, addr, current_command: CommandType::WaitingForCommand })
+        },
+        Err(e) if matches!(e.kind(), io::ErrorKind::WouldBlock) => {
+            // ignore.
+        },
+        Err(e) => {
+            // okay, real error, knock it up
+            return Err(e.into())
+        }
+    }
+
+    // uh lets play ignorey ignorey for now
+
+    Ok(())
+}

quicktap-cli/src/main.rs

@@ -1,15 +1,132 @@
-use std::net::{Ipv4Addr};
+
-use quicktap::cidr::{IpInet, Ipv4Inet};
+use std::fs::File;
+
+use std::os::unix::net::{UnixListener};
+
+use std::sync::mpsc::channel;
+use std::thread::{spawn};
+
+use clap::Parser;
+use daemonize::Daemonize;
+use log::{error, info};
+
 use quicktap::drivers::tun::TunDevice;
 use quicktap::drivers::tungeneric::{GenericDriver, GenericInterface};
 
+use crate::cli::Cli;
+use crate::command::{command_handler, PacketThreadCommand};
+use crate::pproc::packet_thread;
+
+pub mod cli;
+pub mod pproc;
+pub mod command;
+
 fn main() {
-    let mut device = TunDevice::new(&GenericInterface {
+    simple_logger::init().unwrap();
-        addresses: vec![IpInet::V4(Ipv4Inet::new(Ipv4Addr::new(10, 19, 2, 2), 16).unwrap())],
+
-        mtu: None,
+    let args = Cli::parse();
-        name: "ela1".to_string(),
+
-    }).unwrap();
+    info!("Hello, world! {}", quicktap::version());
-    loop {
+    info!("Starting up");
-        println!("{:?}", device.read().unwrap().header)
+
+    if !args.foreground {
+        info!("Forking to background");
+
+        let stdout = match File::create("/var/log/e4.log") {
+            Ok(f) => f,
+            Err(e) => {
+                error!("Failed to open stdout file: {}", e);
+                std::process::exit(8);
+            }
+        };
+        let stderr = match File::create("/var/log/e4.err") {
+            Ok(f) => f,
+            Err(e) => {
+                error!("Failed to open stderr file: {}", e);
+                std::process::exit(9);
+            }
+        };
+
+        let daemon_opts = Daemonize::new()
+            .stdout(stdout)
+            .stderr(stderr);
+        match daemon_opts.start() {
+            Ok(_) => info!("Forked to background successfully"),
+            Err(e) => {
+                error!("Failed to daemonize quicktap-cli worker process: {}", e);
+                std::process::exit(1);
+            }
+        }
     }
+
+    info!("Creating unconfigured device");
+
+    let device = match TunDevice::new(&GenericInterface {
+        addresses: vec![],
+        mtu: None,
+        name: args.interface_name.clone(),
+    }) {
+        Ok(d) => d,
+        Err(e) => {
+            error!("Failed to create interface: {}", e);
+            std::process::exit(2);
+        }
+    };
+
+    info!("Spawning packet processor thread");
+
+    let (tx, rx) = channel::<PacketThreadCommand>();
+
+    let pproc_thread = spawn(|| {
+        match packet_thread(device, rx) {
+            Ok(_) => (),
+            Err(e) => {
+                error!("Error in pproc_thread: {}", e);
+            }
+        }
+    });
+
+    info!("Creating command listener");
+    match UnixListener::bind(format!("/var/run/{}.sock", args.interface_name)) {
+        Ok(l) => {
+            // handle l
+            match command_handler(l) {
+                Ok(_) => (),
+                Err(e) => error!("Error in command handler: {}", e)
+            }
+        },
+        Err(e) => {
+            error!("Error creating command listener {}: {}", format!("/var/run/{}.sock", args.interface_name), e);
+        }
+    };
+
+
+    match tx.send(PacketThreadCommand::Stop) {
+        Ok(_) => (),
+        Err(e) => {
+            error!("Error sending stop command to packet thread: {}", e);
+            std::process::exit(6);
+        }
+    }
+
+    info!("Waiting for packet thread to stop");
+    match pproc_thread.join() {
+        Ok(_) => (),
+        Err(e) => {
+            error!("Error joining thread: {:?}", e);
+            std::process::exit(5);
+        }
+    }
+
+    info!("Cleaning up");
+
+    match std::fs::remove_file(format!("/var/run/{}.sock", args.interface_name)) {
+        Ok(_) => (),
+        Err(e) => {
+            error!("Failed to remove existing socket: {}", e);
+            std::process::exit(7);
+        }
+    }
+
+    info!("Cya!");
 }

quicktap-cli/src/pproc.rs

@@ -0,0 +1,45 @@
+use std::error::Error;
+use std::io;
+use std::sync::mpsc::Receiver;
+
+use log::{error, info};
+
+use quicktap::drivers::tun::TunDevice;
+use quicktap::drivers::tungeneric::GenericDriver;
+
+use crate::command::PacketThreadCommand;
+
+pub fn packet_thread(mut device: TunDevice, rx: Receiver<PacketThreadCommand>) -> Result<(), Box<dyn Error>> {
+    loop {
+        // Check command channel
+        let command = match rx.try_recv() {
+            Ok(d) => Some(d),
+            Err(e) if matches!(e, std::sync::mpsc::TryRecvError::Empty) => None,
+            Err(e) => return Err(e.into())
+        };
+        if let Some(cmd) = command {
+            if let PacketThreadCommand::Stop = cmd {
+                info!("packet thread: recieved command to stop by control process");
+                return Ok(())
+            }
+        }
+
+        let packet = match device.read() {
+            Ok(p) => Some(p),
+            Err(e) => match e.kind() {
+                io::ErrorKind::WouldBlock => None,
+                _ => {
+                    error!("Error while reading packets from interface: {}", e);
+                    return Err(e.into());
+                }
+            }
+        };
+
+        if let Some(p) = packet {
+            info!("recv_packet_on_tun {:?}", p.header);
+
+            // parse and route
+
+        }
+    }
+}

quicktap/Cargo.toml

@@ -14,6 +14,8 @@ x25519-dalek = "2.0.0-pre.1"
 rand = "0.8.5"
 hmac = "0.12.1"
 chacha20poly1305 = "0.10.1"
+build-info = "0.0.29"
+log = "0.4.17"
 
 [target.'cfg(unix)'.dependencies]
 tun = "0.5.4"
@@ -21,3 +23,6 @@ tun = "0.5.4"
 [dev-dependencies]
 hex_lit = "0.1.1"
 hex = "0.4.3"
+
+[build-dependencies]
+build-info-build = "0.0.29"

quicktap/README.md

@@ -1,4 +1,4 @@
-# Quicktap
+# Quicktap Engine
 Quicktap is a (hopefully) standard-compliant Rust implementation of the [WireGuard protocol](https://wireguard.org).
 
 It was designed to be a simpler alternative to Cloudflare's [boringtun](https://github.com/cloudflare/boringtun).

quicktap/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    build_info_build::build_script();
+}

quicktap/src/device/mod.rs

@@ -0,0 +1,46 @@
+//! A high-level implementation of the `WireGuard` protocol; does everything the kernel module does except for interfacing with the networking interfaces.
+//! Use the appropriate glue layer in `quicktap::drivers` to provide the tun/tap interface, and the mechanism in `quicktap::drivers::udp_listener` for working with the `UdpSocket`.
+
+use std::collections::HashMap;
+use x25519_dalek::{PublicKey, StaticSecret};
+use crate::noise::handshake::HandshakeState;
+
+/// A high-level struct for the configuration of a `WireGuard` device. This is the equivalent of `[Interface]` in wg-quick.
+pub struct QTInterface<'a> {
+    /// A list of `QTPeer`s that this interface manages
+    pub peers: HashMap<PublicKey, QTPeer<'a>>,
+    /// The private key of the interface
+    pub private_key: StaticSecret
+}
+impl<'a> QTInterface<'a> {
+    /// Create a new, blank `QTInterface` with no configuration
+    pub fn new(private_key: StaticSecret) -> Self {
+        QTInterface {
+            peers: HashMap::default(),
+            private_key
+        }
+    }
+}
+
+/// A high-level struct for the current state with another peer. This is the equivalent of `[Peer]` in wg-quick, with additional tunneling information added.
+pub struct QTPeer<'a> {
+    /// The currently active WireGuard handshake session with this peer, if any
+    pub handshake: Option<HandshakeState<'a>>,
+    /// The in-flight WireGuard handshake with this peer, if any
+    pub handshake_in_flight: Option<HandshakeState<'a>>,
+    /// The public key of this peer
+    pub public_key: PublicKey,
+    /// The optional pre-shared key with this peer. Set to all zero if there is none.
+    pub q: [u8; 32]
+}
+impl<'a> QTPeer<'a> {
+    /// Create a new, blank `QTPeer` with no configuration
+    pub fn new(key: PublicKey) -> Self {
+        QTPeer {
+            handshake: None,
+            handshake_in_flight: None,
+            public_key: key,
+            q: [0u8; 32]
+        }
+    }
+}

quicktap/src/drivers/error.rs

@@ -0,0 +1,23 @@
+//! Defines the error type for the glue layer
+use std::error::Error;
+use std::fmt::{Display, Formatter};
+
+#[derive(Debug)]
+#[allow(clippy::module_name_repetitions)]
+/// Represents an error in the driver (glue) portion of quicktap
+pub enum DriverError {
+    /// An invalid packet type has been received on the interface, and quicktap does not know how to process it
+    /// This is raised in the PREENTRY stage of packet processing
+    InvalidPacketTypeRecvOnInterface,
+    /// A correctly authenticated handshake packet was received, but we do not recognize the peer
+    UnrecognizedValidHandshake
+}
+impl Error for DriverError {}
+impl Display for DriverError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::InvalidPacketTypeRecvOnInterface => write!(f, "Invalid packet type received on interface"),
+            Self::UnrecognizedValidHandshake => write!(f, "Handshake packet valid, but from unknown peer")
+        }
+    }
+}

quicktap/src/drivers/linux.rs

@@ -3,8 +3,10 @@
 use std::error::Error;
 use std::io;
 use std::io::{Read, Write};
+
 use etherparse::IpHeader;
 use tun::platform::Device;
+
 use crate::drivers::tungeneric::{GenericDriver, GenericInterface, TunPacket};
 
 #[allow(clippy::module_name_repetitions)]
@@ -31,15 +33,18 @@ impl GenericDriver for TunDevice {
         if let Some(mtu) = config.mtu {
             device_config.mtu(mtu);
         }
+        let device = tun::create(&device_config)?;
+        device.set_nonblock()?;
+
         Ok(Self {
-            device: tun::create(&device_config)?,
+            device,
             read_buf: [0u8; 4096],
             read_offset: 0,
             packet_buf: [0u8; 4096],
         })
     }
 
-    fn read(&mut self) -> Result<TunPacket, Box<dyn Error>> {
+    fn read(&mut self) -> Result<TunPacket, io::Error> {
         self.packet_buf = [0u8; 4096];
         let _ = self.device.read(&mut self.packet_buf)?;
         let ip_header = IpHeader::from_slice(&self.packet_buf);
@@ -53,7 +58,7 @@ impl GenericDriver for TunDevice {
             })
         }
 
-        Err(io::Error::new(io::ErrorKind::WouldBlock, "No packets detected yet").into())
+        Err(io::Error::new(io::ErrorKind::WouldBlock, "No packets detected yet"))
     }
 
     fn clear(&mut self) {
@@ -61,8 +66,9 @@ impl GenericDriver for TunDevice {
         self.read_offset = 0;
     }
 
-    fn write(&mut self, packet: TunPacket) -> Result<(), Box<dyn Error>> {
+    fn write(&mut self, packet: TunPacket) -> Result<(), io::Error> {
         let _ = self.device.write(&packet.packet)?;
         Ok(())
     }
 }
+

quicktap/src/drivers/mod.rs

@@ -5,3 +5,9 @@
 pub mod tun; // Tun/tap drivers for Linux
 
 pub mod tungeneric;
+
+pub mod udp_listener;
+pub mod error;
+
+#[cfg(test)]
+pub mod tests;

quicktap/src/drivers/tests.rs

@@ -0,0 +1,11 @@
+#![allow(clippy::unwrap_used)] // we want to panic, this is a test file
+#![allow(clippy::missing_errors_doc)]
+#![allow(clippy::missing_panics_doc)]
+#![allow(clippy::missing_safety_doc)]
+
+use crate::drivers::error::DriverError;
+
+#[cfg(test)]
+pub fn error_tests() {
+    assert_eq!(format!("{}", DriverError::InvalidPacketTypeRecvOnInterface), "Invalid packet type received on interface".to_string());
+}

quicktap/src/drivers/tungeneric.rs

@@ -1,8 +1,10 @@
 //! Generic traits and modules to represent a tun/tap device
 
 use std::error::Error;
+use std::io;
+
 use cidr::IpInet;
-use etherparse::{IpHeader};
+use etherparse::IpHeader;
 
 #[derive(Debug)]
 /// A parsed packet from an interface
@@ -24,7 +26,7 @@ pub trait GenericDriver {
     /// Upon finding a successful packet inside the internal buffer, or the .clear() method being called, the internal buffer will be cleared.
     /// # Errors
     /// This function will return `WouldBlock` if a packet could not be read. This function may error if there is an error reading the interface.
-    fn read(&mut self) -> Result<TunPacket, Box<dyn Error>>;
+    fn read(&mut self) -> Result<TunPacket, io::Error>;
 
     /// Clear any internal state of this interface.
     fn clear(&mut self);
@@ -32,7 +34,7 @@ pub trait GenericDriver {
     /// Attempt to write a packet to the interface.
     /// # Errors
     /// This function will error if an error occured writing to the device.
-    fn write(&mut self, packet: TunPacket) -> Result<(), Box<dyn Error>>;
+    fn write(&mut self, packet: TunPacket) -> Result<(), io::Error>;
 }
 
 /// Generic interface config

quicktap/src/drivers/udp_listener.rs

@@ -0,0 +1,61 @@
+//! The logic for the WireGuard UDP socket.
+
+use std::error::Error;
+use std::io;
+use std::net::UdpSocket;
+use crate::device::QTInterface;
+use crate::drivers::error::DriverError;
+use crate::stack::entry_udp::UDPPacketEntryStage;
+use crate::stack::PacketProcessingStage;
+
+/// The maximum amount of bytes that can be taken up by a Handshake Initiation packet.
+pub const MSG1_MAX_BYTES: usize = 148;
+/// The maximum amount of bytes that can be taken up by a Handshake Response packet.
+pub const MSG2_MAX_BYTES: usize = 92;
+/// The maximum amount of bytes that can be taken up by a data packet.
+pub const MSGDATA_MAX_BYTES: usize = 65567;
+/// The maximum amount of bytes that can be taken up by a cookie reply packet.
+pub const MSGCOOKIE_MAX_BYTES: usize = 64;
+
+/// Represents the result of a socket processing round
+pub enum SocketRoundResult {
+    /// Represents that an io-specific error was received
+    IoError(io::Error),
+    /// Represents that a non-io-specific error was received
+    GenericAnyError(Box<dyn Error>)
+}
+
+/// Run a socket update round on the (nonblocking!) UDP socket provided. Checks for any packets that may be present and send them off to get processed.
+/// **Warning!** This only runs *one* update round - therefore only one packet will be processed if any are present.
+/// # Errors
+/// This function will error if a socket read fails or the processing of the packet fails. See `PacketEntryStage::process_packet()` for more details on packet processing.
+pub fn qtap_socket_round<'a>(socket: &mut UdpSocket, interface: &'a mut QTInterface<'a>) -> Result<(), SocketRoundResult> {
+    let mut packet_id = [0u8; 1];
+    match socket.peek(&mut packet_id) {
+        Ok(_) => (),
+        Err(e) => return Err(SocketRoundResult::IoError(e))
+    }; // Intentionally peek into a 1-byte vector. This will NOT remove the datagram from the queue.
+    // We WANT to discard the rest of the packet; right now we only care about the first byte so we know how much memory we need to allocate for the buffer.
+    // The packet type tells us this.
+
+    let buf_size = match packet_id[0] {
+        1 => MSG1_MAX_BYTES,
+        2 => MSG2_MAX_BYTES,
+        4 => MSGDATA_MAX_BYTES,
+        3 => MSGCOOKIE_MAX_BYTES,
+        _ => return Err(SocketRoundResult::GenericAnyError(DriverError::InvalidPacketTypeRecvOnInterface.into()))
+    };
+
+    let mut packet_buf = vec![0u8; buf_size];
+    let (read_bytes, from) = match socket.recv_from(&mut packet_buf) {
+        Ok(r) => r,
+        Err(e) => return Err(SocketRoundResult::IoError(e))
+    };
+
+    let packet = packet_buf[..read_bytes].to_vec();
+
+    match UDPPacketEntryStage::process_packet(packet, &from, interface) {
+        Ok(_) => Ok(()),
+        Err(e) => Err(SocketRoundResult::GenericAnyError(e))
+    }
+}

quicktap/src/lib.rs

@@ -10,9 +10,20 @@
 
 // This is an annoyance
 #![allow(clippy::must_use_candidate)]
+#![allow(clippy::module_name_repetitions)]
 
 pub use cidr;
 
 pub mod drivers;
 pub mod qcrypto;
 pub mod noise;
+pub mod stack;
+pub mod device;
+
+#[cfg(test)]
+pub mod tests;
+
+/// Gets the compile-time versioning information for the engine build.
+pub const fn version() -> &'static str {
+    build_info::format!("quicktap engine v{} ({}) built at {} with {}", $.crate_info.version, $.version_control.unwrap().git().unwrap().commit_short_id, $.timestamp, $.compiler)
+}

quicktap/src/noise/data.rs

@@ -18,8 +18,8 @@ fn unpad_packet(p: &[u8]) -> Vec<u8> {
 /// This function will error if the encryption step is unsuccessful.
 pub fn encapsulate(state: &mut HandshakeState, packet: &Vec<u8>) -> Result<Vec<u8>, NoiseError> {
     let packet = pad_packet(packet);
-    let counter = state.n_send;
+    let counter = state.n_send + 1;
-    let packet_data = match qcrypto_aead(&state.t_send, state.n_send, &packet, &[]) {
+    let packet_data = match qcrypto_aead(&state.t_send, state.n_send + 1, &packet, &[]) {
         Ok(d) => d,
         Err(e) => return Err(NoiseError::ChaCha20Error(e))
     };
@@ -32,6 +32,8 @@ pub fn encapsulate(state: &mut HandshakeState, packet: &Vec<u8>) -> Result<Vec<u
     res[8..16].copy_from_slice(&counter.to_le_bytes());
     res[16..16+packet_data.len()].copy_from_slice(&packet_data);
 
+    state.n_send += 1;
+
     Ok(res)
 }
 
@@ -53,14 +55,18 @@ pub fn deencapsulate(state: &mut HandshakeState, packet: &[u8]) -> Result<Vec<u8
         return Err(NoiseError::PacketParseError(NoisePacketParseError::WrongIndex(index_me as usize, usize::from_le_bytes(packet[4..8].try_into().unwrap()))))
     }
     let counter = u64::from_le_bytes(packet[8..16].try_into().unwrap());
-    if state.n_recv == counter {
 
+    if !state.bitfield.check_replay_window(counter) {
+        // this packet is not okay! replayed or too old
+        return Err(NoiseError::PacketReplayed)
     }
-    // TODO: Check if this counter is okay, sliding windows and stuff. Don't feel like implementing it fully right now
+
     let packet = match qcrypto_aead_decrypt(&state.t_recv, counter, &packet[16..], &[]) {
         Ok(p) => p,
         Err(e) => return Err(NoiseError::ChaCha20Error(e))
     };
+
+    state.bitfield.update_replay_window(counter);
     state.n_recv = counter;
 
     Ok(unpad_packet(&packet))

quicktap/src/noise/error.rs

@@ -13,6 +13,10 @@ pub enum NoiseError {
     ChaCha20Error(chacha20poly1305::Error),
     /// Represents that the packet had a missing or incorrect cookie MAC.
     PacketUnauthenticated,
+    /// Represents that the packet had the wrong i_i value
+    UnrelatedHandshakePacket,
+    /// Represents that the packet has been replayed and should be dropped
+    PacketReplayed
 }
 impl Error for NoiseError {}
 impl Display for NoiseError {
@@ -20,7 +24,9 @@ impl Display for NoiseError {
         match &self {
             Self::PacketParseError(err) => write!(f, "{}", err),
             Self::ChaCha20Error(error) => write!(f, "Encryption error: {}", error),
-            Self::PacketUnauthenticated => write!(f, "Unauthenticated packet")
+            Self::PacketUnauthenticated => write!(f, "Unauthenticated packet"),
+            Self::UnrelatedHandshakePacket => write!(f, "Unrelated handshake packet"),
+            Self::PacketReplayed => write!(f, "Packet was replayed")
         }
     }
 }

quicktap/src/noise/handshake/initiator.rs

@@ -11,6 +11,48 @@ use crate::qcrypto::hashes::{qcrypto_hash_twice, qcrypto_mac};
 use crate::qcrypto::hkdf::qcrypto_hkdf;
 use crate::qcrypto::pki::{qcrypto_dh_generate_longterm, qcrypto_dh_longterm};
 
+struct HandshakeInitiatorRaw {
+    sender: [u8; 4],
+    ephemeral: [u8; 32],
+    static_pub: [u8; 32 + 16],
+    timestamp: [u8; 12 + 16],
+    mac1: [u8; 16],
+    mac2: [u8; 16]
+}
+impl HandshakeInitiatorRaw {
+    fn to_bytes(&self, session: &HandshakeState) -> [u8; 148] {
+        let mut output = [0u8; 148];
+
+        output[0] = 1u8;
+        output[4..8].copy_from_slice(&self.sender);
+        output[8..40].copy_from_slice(&self.ephemeral);
+        output[40..88].copy_from_slice(&self.static_pub);
+        output[88..116].copy_from_slice(&self.timestamp);
+
+        let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), session.s_pub_i.as_bytes()), &output[..116]);
+
+        output[116..132].copy_from_slice(&mac1);
+
+        let mac2 = if needs_cookie(session) { qcrypto_mac(&session.cookies[session.cookies.len() - 1].cookie, &output[..132]) } else { [0u8; 16] };
+
+        output[132..148].copy_from_slice(&mac2);
+
+        output
+    }
+
+    #[allow(clippy::unwrap_used)] // Only used for type conversions in known safe ways
+    fn from_bytes(bytes: [u8; 148]) -> Self {
+        Self {
+            sender: bytes[4..8].try_into().unwrap(),
+            ephemeral: bytes[8..40].try_into().unwrap(),
+            static_pub: bytes[40..88].try_into().unwrap(),
+            timestamp: bytes[88..116].try_into().unwrap(),
+            mac1: bytes[116..132].try_into().unwrap(),
+            mac2: bytes[132..148].try_into().unwrap()
+        }
+    }
+}
+
 /// Generate a handshake initiator packet and encrypt it using the given session state, starting a new handshake state
 /// # Errors
 /// This function will error if encryption was unsuccessful
@@ -18,7 +60,7 @@ use crate::qcrypto::pki::{qcrypto_dh_generate_longterm, qcrypto_dh_longterm};
 /// While containing unwraps, this function will never panic.
 #[allow(clippy::module_name_repetitions)]
 #[allow(clippy::unwrap_used)] // Safe because it is only used for type conversions in known safe ways
-pub fn handshake_init_to(session: &mut HandshakeState) -> Result<[u8; 148], NoiseError> {
+pub fn generate_handshake_init(session: &mut HandshakeState) -> Result<[u8; 148], NoiseError> {
     session.we_are_initiator = true;
     session.s_pub_i = PublicKey::from(session.s_priv_me);
     session.s_pub_r = session.s_pub_them;
@@ -75,58 +117,14 @@ pub fn handshake_init_to(session: &mut HandshakeState) -> Result<[u8; 148], Nois
     Ok(msg.to_bytes(session))
 }
 
-
+/// Parse a handshake initiator packet and decrypt it using the given session state, updating the session state with decrypted and authenticated values
-struct HandshakeInitiatorRaw {
-    sender: [u8; 4],
-    ephemeral: [u8; 32],
-    static_pub: [u8; 32 + 16],
-    timestamp: [u8; 12 + 16],
-    mac1: [u8; 16],
-    mac2: [u8; 16]
-}
-impl HandshakeInitiatorRaw {
-    fn to_bytes(&self, session: &HandshakeState) -> [u8; 148] {
-        let mut output = [0u8; 148];
-
-        output[0] = 1u8;
-        output[4..8].copy_from_slice(&self.sender);
-        output[8..40].copy_from_slice(&self.ephemeral);
-        output[40..88].copy_from_slice(&self.static_pub);
-        output[88..116].copy_from_slice(&self.timestamp);
-
-        let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), session.s_pub_i.as_bytes()), &output[..116]);
-
-        output[116..132].copy_from_slice(&mac1);
-
-        let mac2 = if needs_cookie(session) { qcrypto_mac(&session.cookies[session.cookies.len() - 1].cookie, &output[..132]) } else { [0u8; 16] };
-
-        output[132..148].copy_from_slice(&mac2);
-
-        output
-    }
-
-    #[allow(clippy::unwrap_used)] // Only used for type conversions in known safe ways
-    fn from_bytes(bytes: [u8; 148]) -> Self {
-        Self {
-            sender: bytes[4..8].try_into().unwrap(),
-            ephemeral: bytes[8..40].try_into().unwrap(),
-            static_pub: bytes[40..88].try_into().unwrap(),
-            timestamp: bytes[88..116].try_into().unwrap(),
-            mac1: bytes[116..132].try_into().unwrap(),
-            mac2: bytes[132..148].try_into().unwrap()
-        }
-    }
-}
-
-/// Parse a handshake initiator packet and encrypt it using the given session state, updating the session state with decrypted and authenticated values
 /// # Errors
 /// This function will error if decryption was unsuccessful
 /// # Panics
 /// While containing unwraps, this function will never panic.
 #[allow(clippy::module_name_repetitions)]
 #[allow(clippy::unwrap_used)] // Only used for type conversions in known safe ways
-pub fn handshake_init_from(session: &mut HandshakeState, packet: [u8; 148]) -> Result<(), NoiseError> {
+pub fn parse_handshake_init(session: &mut HandshakeState, packet: [u8; 148]) -> Result<(), NoiseError> {
-    let s_pub_i = session.s_pub_them;
     let s_pub_r = PublicKey::from(session.s_priv_me);
 
     let msg = HandshakeInitiatorRaw::from_bytes(packet);
@@ -152,14 +150,14 @@ pub fn handshake_init_from(session: &mut HandshakeState, packet: [u8; 148]) -> R
     // This unwrap is safe because the output length is a known constant with these inputs
 
 
-    session.s_pub_i = PublicKey::from(<Vec<u8> as TryInto<[u8; 32]>>::try_into(match qcrypto_aead_decrypt(&k, 0, &msg.static_pub, &h) {
+    let s_pub_i = PublicKey::from(<Vec<u8> as TryInto<[u8; 32]>>::try_into(match qcrypto_aead_decrypt(&k, 0, &msg.static_pub, &h) {
         Ok(s) => s,
         Err(e) => return Err(NoiseError::ChaCha20Error(e))
     }).unwrap());
 
     let h = qcrypto_hash_twice(&h, &msg.static_pub);
 
-    let ci_k_pair = qcrypto_hkdf::<2>(&ck, qcrypto_dh_longterm(session.s_priv_me, &session.s_pub_i).as_bytes());
+    let ci_k_pair = qcrypto_hkdf::<2>(&ck, qcrypto_dh_longterm(session.s_priv_me, &s_pub_i).as_bytes());
     let ck = ci_k_pair[0];
     let k = ci_k_pair[1];
 
@@ -173,7 +171,7 @@ pub fn handshake_init_from(session: &mut HandshakeState, packet: [u8; 148]) -> R
 
     // we need to check mac1 and mac2
 
-    let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), session.s_pub_i.as_bytes()), &packet[..116]);
+    let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), s_pub_i.as_bytes()), &packet[..116]);
     let mac2 = if needs_cookie(session) { qcrypto_mac(&session.cookies[session.cookies.len() - 1].cookie, &packet[..132]) } else { [0u8; 16] };
 
     if mac1 != msg.mac1 || mac2 != msg.mac2 {

quicktap/src/noise/handshake/mod.rs

@@ -4,6 +4,7 @@ use std::fmt::{Debug, Formatter};
 use rand::rngs::OsRng;
 use tai64::Tai64N;
 use x25519_dalek::{PublicKey, StaticSecret};
+use crate::noise::rfc6479::ShiftWindow;
 
 use crate::qcrypto::hkdf::qcrypto_hkdf;
 use crate::qcrypto::timestamp;
@@ -26,6 +27,22 @@ pub const HANDSHAKE_INITIATOR_CHAIN_KEY_HASH: [u8; 32] = [
     147, 232, 183, 14, 225, 156, 101, 186, 7, 158, 243,
 ];
 
+/// Represents what mode the handshake state machine currently is in.
+pub enum HandshakeMode {
+    /// No state is currently present; an init has not been sent or received.
+    Ready,
+    /// We have received an init from the other peer, and need to send the ack packet.
+    InitReceived,
+    /// We have sent an init to the other peer, and are waiting for their ack packet
+    InitSent,
+    /// We have received the ack packet from the other peer, and are ready to derive data keys and begin transport.
+    AckReceived,
+    /// We have sent the ack packet to the other peer, and are ready to derive data keys and begin transport.
+    AckSent,
+    /// We have derived data keys and are ready to send data.
+    Data
+}
+
 /// Represents a cookie we got from the other peer
 #[derive(Debug)]
 pub struct Cookie {
@@ -63,7 +80,11 @@ pub struct HandshakeState<'a> {
     pub n_send: u64,
     pub n_recv: u64,
 
-    pub we_are_initiator: bool
+    pub we_are_initiator: bool,
+
+    pub bitfield: ShiftWindow,
+    
+    pub mode: HandshakeMode
 }
 impl<'a> HandshakeState<'a> {
     /// Determines if the state variables of this `HandshakeState` are the same as another
@@ -94,7 +115,7 @@ impl<'a> HandshakeState<'a> {
 
     /// Create a new handshake state representing a brand-new handshake.
     /// This function initializes the important values with their appropriate initialization vectors, and zeroes out all other values.
-    pub fn new(private_key: &'a StaticSecret, other_pubkey: PublicKey, pre_shared_key: Option<[u8; 32]>) -> Self {
+    pub fn new(private_key: &'a StaticSecret) -> Self {
         Self {
             h: [0u8; 32],
             ck: [0u8; 32],
@@ -104,16 +125,18 @@ impl<'a> HandshakeState<'a> {
             s_pub_r: PublicKey::from([0u8; 32]),
             e_priv_me: StaticSecret::new(OsRng),
             s_priv_me: private_key,
-            s_pub_them: other_pubkey,
+            s_pub_them: PublicKey::from([0u8; 32]),
             i_i: 0,
             i_r: 0,
-            q: pre_shared_key.unwrap_or([0u8; 32]),
+            q: [0u8; 32],
             cookies: vec![],
             t_send: [0u8; 32],
             t_recv: [0u8; 32],
-            n_send: 0,
+            n_send: 1,
-            n_recv: 0,
+            n_recv: 1,
             we_are_initiator: false,
+            bitfield: ShiftWindow::new(),
+            mode: HandshakeMode::Ready
         }
     }
 }

quicktap/src/noise/handshake/response.rs

@@ -10,102 +10,6 @@ use crate::qcrypto::hkdf::qcrypto_hkdf;
 use crate::qcrypto::LABEL_MAC1;
 use crate::qcrypto::pki::{qcrypto_dh_generate_longterm, qcrypto_dh_longterm};
 
-/// Creates a handshake response packet using the current active handshake session.
-/// # Errors
-/// This function will error if an encryption step is unsuccessful
-/// # Panics
-/// This function, while containing unwraps, will never panic.
-#[allow(clippy::unwrap_used)] // Used for known safe type conversions only
-pub fn handshake_response_to(session: &mut HandshakeState) -> Result<[u8; 92], NoiseError> {
-    let eph_keypair = qcrypto_dh_generate_longterm();
-
-    let mut msg = HandshakeResponseRaw {
-        sender: [0u8; 4],
-        receiver: [0u8; 4],
-        ephemeral: [0u8; 32],
-        empty: [0u8; 16],
-        mac1: [0u8; 16],
-        mac2: [0u8; 16]
-    };
-
-    session.ck = qcrypto_hkdf::<1>(&session.ck, eph_keypair.1.as_bytes())[0];
-
-    msg.ephemeral = eph_keypair.1.to_bytes();
-
-    session.h = qcrypto_hash_twice(&session.h, &msg.ephemeral);
-
-    session.ck = qcrypto_hkdf::<1>(&session.ck, qcrypto_dh_longterm(&eph_keypair.0, &session.e_pub_i).as_bytes())[0];
-    session.ck = qcrypto_hkdf::<1>(&session.ck, qcrypto_dh_longterm(&eph_keypair.0, &session.s_pub_i).as_bytes())[0];
-
-    let cr_t_k = qcrypto_hkdf::<3>(&session.ck, &session.q);
-    session.ck = cr_t_k[0];
-    let t = cr_t_k[1];
-    let k = cr_t_k[2];
-
-    session.h = qcrypto_hash_twice(&session.h, &t);
-
-    println!("{:?} {:?} {:?}", k, 0, session.h);
-    msg.empty = match qcrypto_aead(&k, 0, &[], &session.h) {
-        Ok(s) => s.try_into().unwrap(),
-        Err(e) => return Err(NoiseError::ChaCha20Error(e))
-    };
-
-    session.h = qcrypto_hash_twice(&session.h, &msg.empty);
-
-    Ok(msg.to_bytes(session))
-}
-
-/// Decrypts a handshake response packet using the current active handshake session.
-/// # Errors
-/// This function will error if a decryption step is unsuccessful
-/// # Panics
-/// This function, while containing unwraps, will never panic.
-pub fn handshake_response_from(session: &mut HandshakeState, packet: [u8; 92]) -> Result<(), NoiseError> {
-    let msg = HandshakeResponseRaw::from_bytes(packet);
-
-    let e_pub_r = PublicKey::from(msg.ephemeral);
-
-    let mut ck = qcrypto_hkdf::<1>(&session.ck, e_pub_r.as_bytes())[0];
-    let mut h = qcrypto_hash_twice(&session.h, &msg.ephemeral);
-
-    ck = qcrypto_hkdf::<1>(&ck, qcrypto_dh_longterm(&session.e_priv_me, &e_pub_r).as_bytes())[0];
-    ck = qcrypto_hkdf::<1>(&ck, qcrypto_dh_longterm(session.s_priv_me, &e_pub_r).as_bytes())[0];
-
-    let cr_t_k = qcrypto_hkdf::<3>(&ck, &session.q);
-    ck = cr_t_k[0];
-    let t = cr_t_k[1];
-    let k = cr_t_k[2];
-
-    h = qcrypto_hash_twice(&h, &t);
-
-    println!("here");
-    println!("{:?} {:?} {:?}", k, 0, h);
-
-    let empty = match qcrypto_aead_decrypt(&k, 0, &msg.empty, &h) {
-        Ok(s) => s,
-        Err(e) => return Err(NoiseError::ChaCha20Error(e))
-    };
-
-    if !empty.is_empty() {
-        return Err(NoiseError::PacketUnauthenticated)
-    }
-
-    h = qcrypto_hash_twice(&h, &msg.empty);
-
-    let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), session.s_pub_i.as_bytes()), &packet[..60]);
-    let mac2 = if needs_cookie(session) { qcrypto_mac(&session.cookies[session.cookies.len() - 1].cookie, &packet[..76]) } else { [0u8; 16] };
-
-    if mac1 != msg.mac1 || mac2 != msg.mac2 {
-        return Err(NoiseError::PacketUnauthenticated)
-    }
-
-    session.e_pub_r = e_pub_r;
-    session.ck = ck;
-    session.h = h;
-
-    Ok(())
-}
-
 struct HandshakeResponseRaw {
     sender: [u8; 4],
     receiver: [u8; 4],
@@ -147,3 +51,103 @@ impl HandshakeResponseRaw {
         }
     }
 }
+
+/// Creates a handshake response packet using the current active handshake session.
+/// # Errors
+/// This function will error if an encryption step is unsuccessful
+/// # Panics
+/// This function, while containing unwraps, will never panic.
+#[allow(clippy::unwrap_used)] // Used for known safe type conversions only
+pub fn generate_handshake_response(session: &mut HandshakeState) -> Result<[u8; 92], NoiseError> {
+    let eph_keypair = qcrypto_dh_generate_longterm();
+
+    let mut msg = HandshakeResponseRaw {
+        sender: [0u8; 4],
+        receiver: [0u8; 4],
+        ephemeral: [0u8; 32],
+        empty: [0u8; 16],
+        mac1: [0u8; 16],
+        mac2: [0u8; 16]
+    };
+
+    msg.receiver = session.i_i.to_le_bytes();
+    msg.sender = session.i_r.to_le_bytes();
+
+    session.ck = qcrypto_hkdf::<1>(&session.ck, eph_keypair.1.as_bytes())[0];
+
+    msg.ephemeral = eph_keypair.1.to_bytes();
+
+    session.h = qcrypto_hash_twice(&session.h, &msg.ephemeral);
+
+    session.ck = qcrypto_hkdf::<1>(&session.ck, qcrypto_dh_longterm(&eph_keypair.0, &session.e_pub_i).as_bytes())[0];
+    session.ck = qcrypto_hkdf::<1>(&session.ck, qcrypto_dh_longterm(&eph_keypair.0, &session.s_pub_i).as_bytes())[0];
+
+    let cr_t_k = qcrypto_hkdf::<3>(&session.ck, &session.q);
+    session.ck = cr_t_k[0];
+    let t = cr_t_k[1];
+    let k = cr_t_k[2];
+
+    session.h = qcrypto_hash_twice(&session.h, &t);
+
+    println!("{:?} {:?} {:?}", k, 0, session.h);
+    msg.empty = match qcrypto_aead(&k, 0, &[], &session.h) {
+        Ok(s) => s.try_into().unwrap(),
+        Err(e) => return Err(NoiseError::ChaCha20Error(e))
+    };
+
+    session.h = qcrypto_hash_twice(&session.h, &msg.empty);
+
+    Ok(msg.to_bytes(session))
+}
+
+/// Decrypts a handshake response packet using the current active handshake session.
+/// # Errors
+/// This function will error if a decryption step is unsuccessful
+/// # Panics
+/// This function, while containing unwraps, will never panic.
+pub fn parse_handshake_response(session: &mut HandshakeState, packet: [u8; 92]) -> Result<(), NoiseError> {
+    let msg = HandshakeResponseRaw::from_bytes(packet);
+
+    let e_pub_r = PublicKey::from(msg.ephemeral);
+
+    let mut ck = qcrypto_hkdf::<1>(&session.ck, e_pub_r.as_bytes())[0];
+    let mut h = qcrypto_hash_twice(&session.h, &msg.ephemeral);
+
+    ck = qcrypto_hkdf::<1>(&ck, qcrypto_dh_longterm(&session.e_priv_me, &e_pub_r).as_bytes())[0];
+    ck = qcrypto_hkdf::<1>(&ck, qcrypto_dh_longterm(session.s_priv_me, &e_pub_r).as_bytes())[0];
+
+    let cr_t_k = qcrypto_hkdf::<3>(&ck, &session.q);
+    ck = cr_t_k[0];
+    let t = cr_t_k[1];
+    let k = cr_t_k[2];
+
+    h = qcrypto_hash_twice(&h, &t);
+
+    let empty = match qcrypto_aead_decrypt(&k, 0, &msg.empty, &h) {
+        Ok(s) => s,
+        Err(e) => return Err(NoiseError::ChaCha20Error(e))
+    };
+
+    if !empty.is_empty() {
+        return Err(NoiseError::PacketUnauthenticated)
+    }
+
+    h = qcrypto_hash_twice(&h, &msg.empty);
+
+    let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), session.s_pub_i.as_bytes()), &packet[..60]);
+    let mac2 = if needs_cookie(session) { qcrypto_mac(&session.cookies[session.cookies.len() - 1].cookie, &packet[..76]) } else { [0u8; 16] };
+
+    if mac1 != msg.mac1 || mac2 != msg.mac2 {
+        return Err(NoiseError::PacketUnauthenticated)
+    }
+
+    if msg.receiver != session.i_i.to_le_bytes() {
+        return Err(NoiseError::UnrelatedHandshakePacket)
+    }
+
+    session.e_pub_r = e_pub_r;
+    session.ck = ck;
+    session.h = h;
+
+    Ok(())
+}

quicktap/src/noise/handshake/tests.rs

@@ -1,8 +1,8 @@
 #![allow(clippy::unwrap_used)] // this is a test harness, we want to panic
 
 use crate::noise::handshake::HandshakeState;
-use crate::noise::handshake::initiator::{handshake_init_from, handshake_init_to};
+use crate::noise::handshake::initiator::{parse_handshake_init, generate_handshake_init};
-use crate::noise::handshake::response::{handshake_response_from, handshake_response_to};
+use crate::noise::handshake::response::{parse_handshake_response, generate_handshake_response};
 use crate::qcrypto::pki::qcrypto_dh_generate_longterm;
 
 #[test]
@@ -10,11 +10,13 @@ fn noise_halfhandshake_test() {
     let alice_keypair = qcrypto_dh_generate_longterm();
     let bob_keypair = qcrypto_dh_generate_longterm();
 
-    let mut alice_session = HandshakeState::new(&alice_keypair.0, bob_keypair.1, None);
+    let mut alice_session = HandshakeState::new(&alice_keypair.0);
-    let mut bob_session = HandshakeState::new(&bob_keypair.0, alice_keypair.1, None);
+    alice_session.s_pub_them = bob_keypair.1;
+    let mut bob_session = HandshakeState::new(&bob_keypair.0);
+    bob_session.s_pub_them = alice_keypair.1;
 
-    let handshake_init = handshake_init_to(&mut alice_session).unwrap();
+    let handshake_init = generate_handshake_init(&mut alice_session).unwrap();
-    handshake_init_from(&mut bob_session, handshake_init).unwrap();
+    parse_handshake_init(&mut bob_session, handshake_init).unwrap();
 
     println!("{:?}", alice_session);
     println!("{:?}", bob_session);
@@ -27,14 +29,16 @@ fn noise_nocookie_handshake_test() {
     let alice_keypair = qcrypto_dh_generate_longterm();
     let bob_keypair = qcrypto_dh_generate_longterm();
 
-    let mut alice_session = HandshakeState::new(&alice_keypair.0, bob_keypair.1, None);
+    let mut alice_session = HandshakeState::new(&alice_keypair.0);
-    let mut bob_session = HandshakeState::new(&bob_keypair.0, alice_keypair.1, None);
+    alice_session.s_pub_them = bob_keypair.1;
+    let mut bob_session = HandshakeState::new(&bob_keypair.0);
+    bob_session.s_pub_them = alice_keypair.1;
 
-    let handshake_init = handshake_init_to(&mut alice_session).unwrap();
+    let handshake_init = generate_handshake_init(&mut alice_session).unwrap();
-    handshake_init_from(&mut bob_session, handshake_init).unwrap();
+    parse_handshake_init(&mut bob_session, handshake_init).unwrap();
 
-    let handshake_response = handshake_response_to(&mut bob_session).unwrap();
+    let handshake_response = generate_handshake_response(&mut bob_session).unwrap();
-    handshake_response_from(&mut alice_session, handshake_response).unwrap();
+    parse_handshake_response(&mut alice_session, handshake_response).unwrap();
 
     println!("{:?}", alice_session);
     println!("{:?}", bob_session);

quicktap/src/noise/mod.rs

@@ -5,3 +5,4 @@ pub mod data;
 
 #[cfg(test)]
 pub mod tests;
+pub mod rfc6479;

quicktap/src/noise/rfc6479/mod.rs

@@ -0,0 +1,95 @@
+//! A Rust implementation of the anti-replay algorithm described in [RFC 6479](https://rfc-editor.org/rfc6479).
+
+const SIZE_OF_INTEGER: usize = std::mem::size_of::<usize>() * 8;
+const BITMAP_LEN: usize = 1024 / SIZE_OF_INTEGER;
+const BITMAP_INDEX_MASK: u64 = BITMAP_LEN as u64 - 1;
+const REDUNDANT_BIT_SHIFTS: u64 = 5;
+const REDUNDANT_BITS: u64 = 1 << REDUNDANT_BIT_SHIFTS;
+const BITMAP_LOC_MASK: u64 = REDUNDANT_BITS - 1;
+const WINDOW_SIZE: u64 = 512;
+
+#[derive(Default)]
+/// An implementation of the RFC6479 anti-replay algorithm
+pub struct ShiftWindow {
+    replaywin_lastseq: u64,
+    replaywin_bitmap: [usize; BITMAP_LEN],
+}
+
+impl ShiftWindow {
+    /// Create a new ShiftWindow with default values
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Check if a given sequence value is okay given the current state of the shift window
+    pub fn check_replay_window(&self, seq: u64) -> bool {
+        println!("sequence {} {}", seq, self.replaywin_lastseq);
+
+        // first == 0 or wrapped
+        if seq == 0 {
+            return false;
+        }
+
+        // larger is always good
+        if seq > self.replaywin_lastseq {
+            return true;
+        }
+
+        // too old
+        if (seq + WINDOW_SIZE) < self.replaywin_lastseq {
+            return false;
+        }
+
+        let bit_location = seq & BITMAP_LOC_MASK;
+        let index = (seq >> REDUNDANT_BIT_SHIFTS) & BITMAP_INDEX_MASK;
+
+        self.replaywin_bitmap[index as usize] & (1 << bit_location) == 0
+    }
+
+    /// Update the internal state of the replay window to mark the given sequence number as used and disallow future use of it.
+    pub fn update_replay_window(&mut self, seq: u64) {
+        if !self.check_replay_window(seq) {
+            return;
+        }
+
+        let index = seq >> REDUNDANT_BIT_SHIFTS;
+
+        if seq > self.replaywin_lastseq {
+            let index_cur = self.replaywin_lastseq >> REDUNDANT_BIT_SHIFTS;
+            let mut diff = index - index_cur;
+
+            if diff > BITMAP_LEN as u64 {
+                diff = BITMAP_LEN as u64;
+            }
+
+            for id in 0..diff {
+                let iindex = (id + index_cur + 1) & BITMAP_INDEX_MASK;
+                self.replaywin_bitmap[iindex as usize] = 0;
+            }
+
+            self.replaywin_lastseq = seq;
+        }
+
+        let index = index & BITMAP_INDEX_MASK;
+        let bit_location = seq & BITMAP_LOC_MASK;
+
+        self.replaywin_bitmap[index as usize] |= 1 << bit_location;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::noise::rfc6479::ShiftWindow;
+
+    #[test]
+    pub fn rfc6479_tests() {
+        let mut shiftwin = ShiftWindow::new();
+
+        assert!(!shiftwin.check_replay_window(0));
+        assert!(shiftwin.check_replay_window(1));
+        shiftwin.update_replay_window(1);
+        assert!(!shiftwin.check_replay_window(1));
+        shiftwin.update_replay_window(329_846_324_987);
+        assert!(!shiftwin.check_replay_window(2));
+    }
+}

quicktap/src/noise/tests.rs

@@ -3,8 +3,8 @@
 
 use crate::noise::data::{deencapsulate, encapsulate};
 use crate::noise::handshake::HandshakeState;
-use crate::noise::handshake::initiator::{handshake_init_from, handshake_init_to};
+use crate::noise::handshake::initiator::{parse_handshake_init, generate_handshake_init};
-use crate::noise::handshake::response::{handshake_response_from, handshake_response_to};
+use crate::noise::handshake::response::{parse_handshake_response, generate_handshake_response};
 use crate::qcrypto::pki::qcrypto_dh_generate_longterm;
 
 #[test]
@@ -12,14 +12,16 @@ pub fn noise_transport_test() {
     let alice_keypair = qcrypto_dh_generate_longterm();
     let bob_keypair = qcrypto_dh_generate_longterm();
 
-    let mut alice_session = HandshakeState::new(&alice_keypair.0, bob_keypair.1, None);
+    let mut alice_session = HandshakeState::new(&alice_keypair.0);
-    let mut bob_session = HandshakeState::new(&bob_keypair.0, alice_keypair.1, None);
+    alice_session.s_pub_them = bob_keypair.1;
+    let mut bob_session = HandshakeState::new(&bob_keypair.0);
+    bob_session.s_pub_them = alice_keypair.1;
 
-    let handshake_init = handshake_init_to(&mut alice_session).unwrap();
+    let handshake_init = generate_handshake_init(&mut alice_session).unwrap();
-    handshake_init_from(&mut bob_session, handshake_init).unwrap();
+    parse_handshake_init(&mut bob_session, handshake_init).unwrap();
 
-    let handshake_response = handshake_response_to(&mut bob_session).unwrap();
+    let handshake_response = generate_handshake_response(&mut bob_session).unwrap();
-    handshake_response_from(&mut alice_session, handshake_response).unwrap();
+    parse_handshake_response(&mut alice_session, handshake_response).unwrap();
 
     alice_session.derive_transport();
     bob_session.derive_transport();

quicktap/src/stack/entry_udp.rs

@@ -0,0 +1,60 @@
+//! The ENTRY stage of the packet processing stack. Provides a `PacketEntryStage` which implements `PacketProcessingStage`.
+
+use std::error::Error;
+use std::net::SocketAddr;
+use log::{warn};
+use crate::device::QTInterface;
+use crate::drivers::error::DriverError;
+use crate::noise::handshake::{HandshakeMode, HandshakeState};
+use crate::noise::handshake::initiator::parse_handshake_init;
+use crate::stack::{PacketProcessingStage};
+
+/// The ENTRY stage of the packet processing stack for UDP packets
+pub struct UDPPacketEntryStage {}
+
+impl PacketProcessingStage for UDPPacketEntryStage {
+    #[allow(clippy::unwrap_used)] // the arrays are fixed size, with known size values
+    fn process_packet<'a>(pkt: Vec<u8>, from: &SocketAddr, interface: &'a mut QTInterface<'a>) -> Result<(), Box<dyn Error>> {
+        // packet types are determined by the first byte of the packet
+        // if it is not a known packet type, return an error and drop the packet
+        match pkt.first().ok_or(DriverError::InvalidPacketTypeRecvOnInterface)? {
+            1 => Self::handle_new_handshake(pkt.try_into().unwrap(), from, interface),
+            2 => Self::handle_handshake_response(pkt.try_into().unwrap(), from, interface),
+            3 => Self::handle_handshake_cookie_reply(pkt.try_into().unwrap(), from, interface),
+            4 => Self::handle_data_packet(pkt.try_into().unwrap(), from, interface),
+            _ => Err(DriverError::InvalidPacketTypeRecvOnInterface.into())
+        }
+    }
+}
+
+impl UDPPacketEntryStage {
+    fn handle_new_handshake<'a>(pkt: [u8; 148], from: &SocketAddr, interface: &'a mut QTInterface<'a>) -> Result<(), Box<dyn Error>> {
+        let mut new_state = HandshakeState::new(&interface.private_key);
+        parse_handshake_init(&mut new_state, pkt)?; // we have initialized the handshake
+        // now we need to update keying values, and possibly reject the handshake if the peer is unrecognized
+        if !interface.peers.contains_key(&new_state.s_pub_them) {
+            // this peer is unrecognized. ignore it and drop the packet
+            warn!("[stack/ENTRY_UDP] stack received handshake initialization packet from unrecognized peer {:?}", new_state.s_pub_them);
+            return Err(DriverError::UnrecognizedValidHandshake.into())
+        }
+        let peer = interface.peers.get_mut(&new_state.s_pub_them).ok_or(DriverError::UnrecognizedValidHandshake)?;
+        // update keying
+        new_state.q = peer.q;
+
+        // update state machine
+        new_state.mode = HandshakeMode::InitReceived;
+
+        peer.handshake_in_flight = Some(new_state);
+
+        Ok(())
+    }
+    fn handle_handshake_response(pkt: Vec<u8>, from: &SocketAddr, interface: &mut QTInterface) -> Result<(), Box<dyn Error>> {
+        unimplemented!();
+    }
+    fn handle_handshake_cookie_reply(pkt: Vec<u8>, from: &SocketAddr, interface: &mut QTInterface) -> Result<(), Box<dyn Error>> {
+        unimplemented!();
+    }
+    fn handle_data_packet(pkt: Vec<u8>, from: &SocketAddr, interface: &mut QTInterface) -> Result<(), Box<dyn Error>> {
+        unimplemented!();
+    }
+}

quicktap/src/stack/mod.rs

@@ -0,0 +1,40 @@
+//! quicktap's packet processing stack
+//! Packet processing is done in several *stages*:
+//! - ENTRY
+//! - CRYPT
+//! - ROUTING
+//! - PROCESSING
+//! - EXIT
+//! # UDP Packet Flow
+//! For a packet received on the UDP socket, the following route is taken through the processing stack:
+//! ```text
+//! UDP Socket -> ENTRY -> CRYPT -> (drop) <-----+
+//!                 |       |          ^         |
+//!                 |       |          |         |
+//!                 |       +-----> ROUTING -> CRYPT -> EXIT
+//!                 |       v
+//!                 +---> PROCESSING -> (end flow)
+//! ```
+//! # TUN Packet Flow
+//! For a packet received on the TUN interface, the following route is taken through the processing stack:
+//! ```text
+//! TUN Interface -> ENTRY -> ROUTING -> CRYPT -> EXIT
+//!                              |         |
+//!                              v         |
+//!                            (drop) <----+
+//! ```
+
+use std::error::Error;
+use std::net::SocketAddr;
+use crate::device::QTInterface;
+
+pub mod entry_udp;
+
+/// The methods and functions that need to be implemented by a stage in the packet processor
+pub trait PacketProcessingStage {
+    /// Process a raw datagram. This should go down the WHOLE routing chain - assume previous steps have already done.
+    /// For example, if you are the CRYPT layer, and are processing a tun packet, assume that the ENTRY and ROUTING stack stages have already been completed and you are being given the result of that processing.
+    /// # Errors
+    /// This function will error if an error occurs
+    fn process_packet<'a>(pkt: Vec<u8>, from: &SocketAddr, interface: &'a mut QTInterface<'a>) -> Result<(), Box<dyn Error>> where Self: Sized;
+}

quicktap/src/tests.rs

@@ -0,0 +1,8 @@
+#![allow(clippy::unwrap_used)] // we want to panic, this is a test file
+
+use crate::version;
+
+#[test] // This is one of those good ol' "just for codecov" tests. This doesn't actually need to be tested, it's for frontends, but I want that juicy 100% codecov
+pub const fn version_test() {
+    version();
+}