rustls 0.24.0-dev.2

use alloc::boxed::Box;
use alloc::vec::Vec;
use core::ops::Deref;
use core::{fmt, mem};

use pki_types::FipsStatus;

pub use crate::common_state::Side;
use crate::common_state::{ConnectionOutputs, Protocol};
use crate::conn::{
    Accepted, Connection, MessageIter, MessageIterMode, ServerNext, SideData, Transport,
    VerifyPeerIdentity, sealed,
};
use crate::crypto::cipher::{AeadKey, Iv, Payload};
use crate::crypto::tls13::{Hkdf, HkdfExpander, OkmBlock};
use crate::error::{ApiMisuse, Error};
use crate::msgs::{Message, MessagePayload, ServerExtensionsInput, TransportParameters};
use crate::server::{ServerConfig, ServerSide};
use crate::suites::SupportedCipherSuite;
use crate::sync::Arc;
use crate::tls13::Tls13CipherSuite;
use crate::tls13::key_schedule::{
    hkdf_expand_label, hkdf_expand_label_aead_key, hkdf_expand_label_block,
};
use crate::{ClientSide, TlsInputBuffer};
impl Connection<ServerSide, Quic> {
    /// Make a new QUIC server [`Connection`]
    ///
    /// This differs from `Connection::new()` in that it takes an extra `params` argument,
    /// which contains the TLS-encoded transport parameters to send.
    pub fn new_quic(
        config: Arc<ServerConfig>,
        version: Version,
        params: Vec<u8>,
    ) -> Result<Self, Error> {
        check_server_config(&config)?;
        let exts = ServerExtensionsInput {
            transport_parameters: Some(match version {
                Version::V1 | Version::V2 => TransportParameters::Quic(Payload::new(params)),
            }),
        };

        Self::for_server(
            config,
            exts,
            Quic {
                version,
                ..Quic::default()
            },
        )
    }
}

/// An in-progress TLS server handshake.
#[non_exhaustive]
#[derive(Debug)]
pub enum ServerHandshake {
    /// More data needs to be received to make progress.
    NeedsInput(NeedsInput),

    /// A complete `ClientHello` has been received.
    ///
    /// The handshake can be progressed by choosing a [`ServerConfig`] based on
    /// [`Accepted::client_hello()`] and providing it to [`Accepted::choose_config()`].
    Accepted(Accepted<Quic>),

    /// The client's presented identity must be verified.
    ///
    /// See [`VerifyPeerIdentity<ServerSide, Quic>`] for how to proceed.
    VerifyClientIdentity(VerifyPeerIdentity<ServerSide, Quic>),

    /// The handshake is complete.
    Complete(Connection<ServerSide, Quic>),
}

impl ServerHandshake {
    /// Creates a new QUIC [`ServerHandshake`] via the payload of the [`ServerHandshake::NeedsInput`] variant.
    ///
    /// It is a fundamental fact of server TLS connections that the server reads first; this is reflected
    /// in the returned type.
    ///
    /// You may wrap this in the [`ServerHandshake::NeedsInput`] variant to generalise the type to a
    /// [`ServerHandshake`].
    ///
    /// The returned object should be fed data from a single potential client.
    pub fn start(version: Version) -> NeedsInput {
        NeedsInput(Connection::for_acceptor(Quic {
            version,
            ..Quic::default()
        }))
    }
}

impl FromConn<ServerSide> for ServerHandshake {
    fn from_conn(
        mut conn: Connection<ServerSide, Quic>,
        output: &mut Vec<QuicEvent>,
    ) -> Result<Self, Error> {
        output.extend(conn.transport.events());

        Ok(match ServerNext::try_from(conn)? {
            ServerNext::NeedsInput(conn) => Self::NeedsInput(NeedsInput(conn)),

            ServerNext::ChooseConfig(accepted) => Self::Accepted(accepted),

            ServerNext::VerifyClientIdentity(verify) => Self::VerifyClientIdentity(verify),

            ServerNext::Complete(conn) => Self::Complete(conn),
        })
    }
}

impl Accepted<Quic> {
    /// Choose a [`ServerConfig`] to progress the handshake.
    ///
    /// Resolves an [`Accepted`], providing the [`ServerConfig`] that should be used for
    /// the session, and the TLS-encoded QUIC transport parameters to send.
    ///
    /// Returns an error if configuration-dependent validation of the received
    /// `ClientHello` message fails.
    ///
    /// Events are appended to `output`.
    pub fn choose_config(
        self,
        config: Arc<ServerConfig>,
        params: Vec<u8>,
        output: &mut Vec<QuicEvent>,
    ) -> Result<ServerHandshake, Error> {
        check_server_config(&config)?;

        let exts = ServerExtensionsInput {
            transport_parameters: Some(match self.conn.transport.version {
                Version::V1 | Version::V2 => TransportParameters::Quic(Payload::new(params)),
            }),
        };

        let mut tls = Vec::new();
        let conn = self.partial_choose_config(config, exts, &mut tls)?;

        // In QUIC mode, handshake output is emitted via `QuicEvent`s, not `tls`.
        debug_assert!(tls.is_empty());
        ServerHandshake::from_conn(conn, output)
    }
}

impl FromConn<ClientSide> for () {
    fn from_conn(
        _conn: Connection<ClientSide, Quic>,
        _output: &mut Vec<QuicEvent>,
    ) -> Result<(), Error> {
        todo!("nyi")
    }
}

pub(crate) trait FromConn<Side: SideData> {
    fn from_conn(
        conn: Connection<Side, Quic>,
        output: &mut Vec<QuicEvent>,
    ) -> Result<Side::QuicHandshake, Error>;
}

/// More data needs to be processed to make progress.
///
/// Provide the data to [`Self::process()`].
///
/// This type dereferences to [`ConnectionOutputs`]. Individual outputs are `None`
/// until they are learned during the handshake.
pub struct NeedsInput(Connection<ServerSide, Quic>);

impl NeedsInput {
    /// Return the TLS-encoded transport parameters received from the peer.
    ///
    /// While the transport parameters are available before the handshake completes,
    /// they cannot be fully trusted until then. Reliance on them should be minimized.
    /// Any tampering with the parameters will cause the handshake to fail.
    pub fn quic_transport_parameters(&self) -> Option<&[u8]> {
        self.0.transport.transport_parameters()
    }

    /// Compute the keys for decrypting 0-RTT packets, if available.
    pub fn zero_rtt_keys(&self) -> Option<DirectionalKeys> {
        self.0.transport.zero_rtt_keys(&self.0)
    }

    /// Progress the handshake by receiving further unencrypted TLS handshake data.
    ///
    /// The input should be ordered QUIC CRYPTO stream data for one encryption level.
    ///
    /// Handshake data obtained from separate encryption levels should be supplied in separate calls.
    ///
    /// How much of the `input` buffer is consumed is recorded by a call to
    /// [`TlsInputBuffer::discard()`].  Unconsumed data should be presented again on the next call.
    ///
    /// An error from this function is fatal to the connection, as it consumes the [`NeedsInput`]
    /// object.
    ///
    /// On success, this returns:
    ///
    /// - a [`ServerHandshake::NeedsInput`] if more data is required.
    /// - a [`ServerHandshake::Accepted`] if a whole `ClientHello` has been received,
    ///   and a choice of [`ServerConfig`] is required to continue.
    /// - a [`ServerHandshake::VerifyClientIdentity`] if the client's identity requires
    ///   verification.
    /// - a [`ServerHandshake::Complete`] if the handshake is complete.
    ///
    /// `output` has any resulting handshake messages or key changes appended to it.
    pub fn process(
        mut self,
        input: &mut dyn TlsInputBuffer,
        output: &mut Vec<QuicEvent>,
    ) -> Result<ServerHandshake, Error> {
        self.0
            .common
            .recv
            .deframer
            .input_quic(input.slice_mut())?;

        self.0.process(input, &mut Vec::new())?;
        ServerHandshake::from_conn(self.0, output)
    }

    /// Returns data learned during the connection, specific to being a server.
    pub fn side(&self) -> &ServerSide {
        &self.0.side
    }
}

impl Deref for NeedsInput {
    type Target = ConnectionOutputs;

    fn deref(&self) -> &Self::Target {
        self.0.deref()
    }
}

impl fmt::Debug for NeedsInput {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("quic::NeedsInput")
            .finish_non_exhaustive()
    }
}

fn check_server_config(config: &ServerConfig) -> Result<(), Error> {
    let suites = &config.provider.tls13_cipher_suites;
    if suites.is_empty() {
        return Err(ApiMisuse::QuicRequiresTls13Support.into());
    }

    if !suites
        .iter()
        .any(|scs| scs.quic.is_some())
    {
        return Err(ApiMisuse::NoQuicCompatibleCipherSuites.into());
    }

    if config.max_early_data_size != 0 && config.max_early_data_size != 0xffff_ffff {
        return Err(ApiMisuse::QuicRestrictsMaxEarlyDataSize.into());
    }

    Ok(())
}

/// QUIC events that should be handled by the caller.
#[expect(clippy::large_enum_variant)]
#[derive(Debug)]
#[non_exhaustive]
pub enum QuicEvent {
    /// These bytes should be handled as an unencrypted TLS handshake message.
    Message(Vec<u8>),

    /// The key material should be changed.
    KeyChange(KeyChange),
}

impl<Side: SideData> Connection<Side, Quic> {
    /// Consume unencrypted TLS handshake data.
    ///
    /// Handshake data obtained from separate encryption levels should be supplied in separate calls.
    ///
    /// How much of the `input` buffer is consumed is recorded by a call to
    /// [`TlsInputBuffer::discard()`].  Unconsumed data should be presented again on the next call.
    pub fn read_hs(&mut self, input: &mut dyn TlsInputBuffer) -> Result<(), Error> {
        self.common
            .recv
            .deframer
            .input_quic(input.slice_mut())?;

        let mut tls = Vec::new();
        let mut iter = MessageIter::new(input, &mut tls, self, MessageIterMode::All);

        let result = match iter.next(false) {
            Some(Ok(_)) | None => Ok(()),
            Some(Err(e)) => Err(e),
        };

        input.discard(self.common.recv.deframer.take_discard());
        result
    }

    /// Obtain pending events that the caller should process.
    ///
    /// All pending events are returned as an iterator.
    pub fn events(&mut self) -> impl Iterator<Item = QuicEvent> {
        self.transport.events()
    }

    /// Compute the keys for encrypting/decrypting 0-RTT packets, if available
    pub fn zero_rtt_keys(&self) -> Option<DirectionalKeys> {
        self.transport.zero_rtt_keys(self)
    }

    /// Return the TLS-encoded transport parameters for the session's peer.
    ///
    /// While the transport parameters are technically available prior to the
    /// completion of the handshake, they cannot be fully trusted until the
    /// handshake completes, and reliance on them should be minimized.
    /// However, any tampering with the parameters will cause the handshake
    /// to fail.
    pub fn quic_transport_parameters(&self) -> Option<&[u8]> {
        self.transport.transport_parameters()
    }
}

/// The QUIC transport: TLS handshake messages and key changes delivered as [`QuicEvent`]s.
#[derive(Default)]
pub struct Quic {
    pub(crate) version: Version,
    /// QUIC transport parameters received from the peer during the handshake
    pub(crate) params: Option<Vec<u8>>,
    pub(crate) events: Vec<QuicEvent>,
    pub(crate) early_secret: Option<OkmBlock>,
}

impl Quic {
    pub(crate) fn send_msg(&mut self, m: Message<'_>, _must_encrypt: bool) {
        if let MessagePayload::Alert(_) = m.payload {
            // alerts are sent out-of-band in QUIC mode
            return;
        }

        debug_assert!(
            matches!(
                m.payload,
                MessagePayload::Handshake { .. } | MessagePayload::HandshakeFlight(_)
            ),
            "QUIC uses TLS for the cryptographic handshake only"
        );
        let mut bytes = Vec::new();
        m.payload.encode(&mut bytes);
        self.events
            .push(QuicEvent::Message(bytes));
    }

    pub(crate) fn events(&mut self) -> impl Iterator<Item = QuicEvent> {
        mem::take(&mut self.events).into_iter()
    }

    fn zero_rtt_keys(&self, outputs: &ConnectionOutputs) -> Option<DirectionalKeys> {
        let suite = outputs
            .negotiated_cipher_suite()
            .and_then(|suite| match suite {
                SupportedCipherSuite::Tls13(suite) => Some(suite),
                _ => None,
            })?;

        let suite = Suite {
            inner: suite,
            quic: suite.quic?,
        };

        Some(DirectionalKeys::new(
            suite,
            self.early_secret.as_ref()?,
            self.version,
        ))
    }

    fn transport_parameters(&self) -> Option<&[u8]> {
        self.params.as_ref().map(|v| v.as_ref())
    }
}

impl Transport for Quic {}

impl sealed::Transport for Quic {
    fn protocol(&self) -> Protocol {
        Protocol::Quic(self.version)
    }

    fn quic(&mut self) -> Option<&mut dyn QuicOutput> {
        Some(self)
    }
}

impl QuicOutput for Quic {
    fn transport_parameters(&mut self, params: Vec<u8>) {
        self.params = Some(params);
    }

    fn early_secret(&mut self, secret: Option<OkmBlock>) {
        self.early_secret = secret;
    }

    fn handshake_secrets(&mut self, secrets: SecretUpdate) {
        self.events
            .push(QuicEvent::KeyChange(KeyChange::Handshake {
                keys: Keys::new(&Secrets::new(secrets, self.version)),
            }));
    }

    fn traffic_secrets(&mut self, secrets: SecretUpdate) {
        let mut secrets = Secrets::new(secrets, self.version);
        let keys = Keys::new(&secrets);
        secrets.update();
        self.events
            .push(QuicEvent::KeyChange(KeyChange::OneRtt {
                keys,
                next: secrets,
            }));
    }

    fn send_msg(&mut self, m: Message<'_>, must_encrypt: bool) {
        self.send_msg(m, must_encrypt);
    }
}

pub(crate) trait QuicOutput {
    fn transport_parameters(&mut self, params: Vec<u8>);

    fn early_secret(&mut self, secret: Option<OkmBlock>);

    fn handshake_secrets(&mut self, secrets: SecretUpdate);

    fn traffic_secrets(&mut self, secrets: SecretUpdate);

    fn send_msg(&mut self, m: Message<'_>, must_encrypt: bool);
}

/// Secrets used to encrypt/decrypt traffic
#[derive(Clone)]
pub struct Secrets {
    /// Secret used to encrypt packets transmitted by the client
    pub(crate) client: OkmBlock,
    /// Secret used to encrypt packets transmitted by the server
    pub(crate) server: OkmBlock,
    /// Cipher suite used with these secrets
    suite: Suite,
    side: Side,
    version: Version,
}

impl Secrets {
    pub(crate) fn new(update: SecretUpdate, version: Version) -> Self {
        Self {
            client: update.client,
            server: update.server,
            suite: update.suite,
            side: update.side,
            version,
        }
    }

    /// Derive the next set of packet keys
    pub fn next_packet_keys(&mut self) -> PacketKeySet {
        let keys = PacketKeySet::new(self);
        self.update();
        keys
    }

    pub(crate) fn update(&mut self) {
        self.client = hkdf_expand_label_block(
            self.suite
                .inner
                .hkdf_provider
                .expander_for_okm(&self.client)
                .as_ref(),
            self.version.key_update_label(),
            &[],
        );
        self.server = hkdf_expand_label_block(
            self.suite
                .inner
                .hkdf_provider
                .expander_for_okm(&self.server)
                .as_ref(),
            self.version.key_update_label(),
            &[],
        );
    }

    fn local_remote(&self) -> (&OkmBlock, &OkmBlock) {
        match self.side {
            Side::Client => (&self.client, &self.server),
            Side::Server => (&self.server, &self.client),
        }
    }
}

pub(crate) struct SecretUpdate {
    pub(crate) client: OkmBlock,
    pub(crate) server: OkmBlock,
    pub(crate) suite: Suite,
    pub(crate) side: Side,
}

/// Keys used to communicate in a single direction
#[expect(clippy::exhaustive_structs)]
pub struct DirectionalKeys {
    /// Encrypts or decrypts a packet's headers
    pub header: Box<dyn HeaderProtectionKey>,
    /// Encrypts or decrypts the payload of a packet
    pub packet: Box<dyn PacketKey>,
}

impl DirectionalKeys {
    pub(crate) fn new(suite: Suite, secret: &OkmBlock, version: Version) -> Self {
        let builder = KeyBuilder::new(secret, version, suite.quic, suite.inner.hkdf_provider);
        Self {
            header: builder.header_protection_key(),
            packet: builder.packet_key(),
        }
    }
}

/// All AEADs we support have 16-byte tags.
const TAG_LEN: usize = 16;

/// Authentication tag from an AEAD seal operation.
pub struct Tag([u8; TAG_LEN]);

impl From<&[u8]> for Tag {
    fn from(value: &[u8]) -> Self {
        let mut array = [0u8; TAG_LEN];
        array.copy_from_slice(value);
        Self(array)
    }
}

impl AsRef<[u8]> for Tag {
    fn as_ref(&self) -> &[u8] {
        &self.0
    }
}

/// How a [`Tls13CipherSuite`] generates [`PacketKey`]s and [`HeaderProtectionKey`]s.
pub trait Algorithm: Send + Sync {
    /// Produce a [`PacketKey`] for this suite.
    ///
    /// `key` and `iv` is the key material to use.
    fn packet_key(&self, key: AeadKey, iv: Iv) -> Box<dyn PacketKey>;

    /// Produce a [`HeaderProtectionKey`] for this suite.
    ///
    /// `key` is the key material, which is [`Self::aead_key_len()`] bytes in length.
    fn header_protection_key(&self, key: AeadKey) -> Box<dyn HeaderProtectionKey>;

    /// The length in bytes of keys for this Algorithm.
    ///
    /// This controls the size of [`AeadKey`]s presented to [`Self::packet_key()`] and
    /// [`Self::header_protection_key()`].
    fn aead_key_len(&self) -> usize;

    /// The FIPS validation status of this algorithm.
    fn fips(&self) -> FipsStatus {
        FipsStatus::Unvalidated
    }
}

/// A QUIC header protection key
pub trait HeaderProtectionKey: Send + Sync {
    /// Adds QUIC Header Protection.
    ///
    /// `sample` must contain the sample of encrypted payload; see
    /// [Header Protection Sample].
    ///
    /// `first` must reference the first byte of the header, referred to as
    /// `packet[0]` in [Header Protection Application].
    ///
    /// `packet_number` must reference the Packet Number field; this is
    /// `packet[pn_offset:pn_offset+pn_length]` in [Header Protection Application].
    ///
    /// Returns an error without modifying anything if `sample` is not
    /// the correct length (see [Header Protection Sample] and [`Self::sample_len()`]),
    /// or `packet_number` is longer than allowed (see [Packet Number Encoding and Decoding]).
    ///
    /// Otherwise, `first` and `packet_number` will have the header protection added.
    ///
    /// [Header Protection Application]: https://datatracker.ietf.org/doc/html/rfc9001#section-5.4.1
    /// [Header Protection Sample]: https://datatracker.ietf.org/doc/html/rfc9001#section-5.4.2
    /// [Packet Number Encoding and Decoding]: https://datatracker.ietf.org/doc/html/rfc9000#section-17.1
    fn encrypt_in_place(
        &self,
        sample: &[u8],
        first: &mut u8,
        packet_number: &mut [u8],
    ) -> Result<(), Error>;

    /// Removes QUIC Header Protection.
    ///
    /// `sample` must contain the sample of encrypted payload; see
    /// [Header Protection Sample].
    ///
    /// `first` must reference the first byte of the header, referred to as
    /// `packet[0]` in [Header Protection Application].
    ///
    /// `packet_number` must reference the Packet Number field; this is
    /// `packet[pn_offset:pn_offset+pn_length]` in [Header Protection Application].
    ///
    /// Returns an error without modifying anything if `sample` is not
    /// the correct length (see [Header Protection Sample] and [`Self::sample_len()`]),
    /// or `packet_number` is longer than allowed (see
    /// [Packet Number Encoding and Decoding]).
    ///
    /// Otherwise, `first` and `packet_number` will have the header protection removed.
    ///
    /// [Header Protection Application]: https://datatracker.ietf.org/doc/html/rfc9001#section-5.4.1
    /// [Header Protection Sample]: https://datatracker.ietf.org/doc/html/rfc9001#section-5.4.2
    /// [Packet Number Encoding and Decoding]: https://datatracker.ietf.org/doc/html/rfc9000#section-17.1
    fn decrypt_in_place(
        &self,
        sample: &[u8],
        first: &mut u8,
        packet_number: &mut [u8],
    ) -> Result<(), Error>;

    /// Expected sample length for the key's algorithm
    fn sample_len(&self) -> usize;
}

/// Keys to encrypt or decrypt the payload of a packet
pub trait PacketKey: Send + Sync {
    /// Encrypt a QUIC packet
    ///
    /// Takes a `packet_number` and optional `path_id`, used to derive the nonce; the packet
    /// `header`, which is used as the additional authenticated data; and the `payload`. The
    /// authentication tag is returned if encryption succeeds.
    ///
    /// Fails if and only if the payload is longer than allowed by the cipher suite's AEAD algorithm.
    ///
    /// When provided, the `path_id` is used for multipath encryption as described in
    /// <https://www.ietf.org/archive/id/draft-ietf-quic-multipath-15.html#section-2.4>.
    fn encrypt_in_place(
        &self,
        packet_number: u64,
        header: &[u8],
        payload: &mut [u8],
        path_id: Option<u32>,
    ) -> Result<Tag, Error>;

    /// Decrypt a QUIC packet
    ///
    /// Takes a `packet_number` and optional `path_id`, used to derive the nonce; the packet
    /// `header`, which is used as the additional authenticated data, and the `payload`, which
    /// includes the authentication tag.
    ///
    /// On success, returns the slice of `payload` containing the decrypted data.
    ///
    /// When provided, the `path_id` is used for multipath encryption as described in
    /// <https://www.ietf.org/archive/id/draft-ietf-quic-multipath-15.html#section-2.4>.
    fn decrypt_in_place<'a>(
        &self,
        packet_number: u64,
        header: &[u8],
        payload: &'a mut [u8],
        path_id: Option<u32>,
    ) -> Result<&'a [u8], Error>;

    /// Tag length for the underlying AEAD algorithm
    fn tag_len(&self) -> usize;

    /// Number of QUIC packets that can be safely encrypted with a single key of this type.
    ///
    /// Once a `PacketKey` produced for this suite has encrypted more than
    /// `confidentiality_limit` packets, an attacker gains an advantage in distinguishing it
    /// from an ideal pseudorandom permutation (PRP).
    ///
    /// This is to be set on the assumption that packets are maximally sized --
    /// 2 ** 16. For non-QUIC TCP connections see [`CipherSuiteCommon::confidentiality_limit`][csc-limit].
    ///
    /// [csc-limit]: crate::crypto::CipherSuiteCommon::confidentiality_limit
    fn confidentiality_limit(&self) -> u64;

    /// Number of QUIC packets that can be safely decrypted with a single key of this type
    ///
    /// Once a `PacketKey` produced for this suite has failed to decrypt `integrity_limit`
    /// packets, an attacker gains an advantage in forging packets.
    ///
    /// This is not relevant for TLS over TCP (which is also implemented in this crate)
    /// because a single failed decryption is fatal to the connection.
    /// However, this quantity is used by QUIC.
    fn integrity_limit(&self) -> u64;
}

/// Packet protection keys for bidirectional 1-RTT communication
#[expect(clippy::exhaustive_structs)]
pub struct PacketKeySet {
    /// Encrypts outgoing packets
    pub local: Box<dyn PacketKey>,
    /// Decrypts incoming packets
    pub remote: Box<dyn PacketKey>,
}

impl PacketKeySet {
    fn new(secrets: &Secrets) -> Self {
        let (local, remote) = secrets.local_remote();
        let (version, alg, hkdf) = (
            secrets.version,
            secrets.suite.quic,
            secrets.suite.inner.hkdf_provider,
        );

        Self {
            local: KeyBuilder::new(local, version, alg, hkdf).packet_key(),
            remote: KeyBuilder::new(remote, version, alg, hkdf).packet_key(),
        }
    }
}

/// Helper for building QUIC packet and header protection keys
pub struct KeyBuilder<'a> {
    expander: Box<dyn HkdfExpander>,
    version: Version,
    alg: &'a dyn Algorithm,
}

impl<'a> KeyBuilder<'a> {
    /// Create a new KeyBuilder
    pub fn new(
        secret: &OkmBlock,
        version: Version,
        alg: &'a dyn Algorithm,
        hkdf: &'a dyn Hkdf,
    ) -> Self {
        Self {
            expander: hkdf.expander_for_okm(secret),
            version,
            alg,
        }
    }

    /// Derive packet keys
    pub fn packet_key(&self) -> Box<dyn PacketKey> {
        let aead_key_len = self.alg.aead_key_len();
        let packet_key = hkdf_expand_label_aead_key(
            self.expander.as_ref(),
            aead_key_len,
            self.version.packet_key_label(),
            &[],
        );

        let packet_iv =
            hkdf_expand_label(self.expander.as_ref(), self.version.packet_iv_label(), &[]);
        self.alg
            .packet_key(packet_key, packet_iv)
    }

    /// Derive header protection keys
    pub fn header_protection_key(&self) -> Box<dyn HeaderProtectionKey> {
        let header_key = hkdf_expand_label_aead_key(
            self.expander.as_ref(),
            self.alg.aead_key_len(),
            self.version.header_key_label(),
            &[],
        );
        self.alg
            .header_protection_key(header_key)
    }
}

/// Produces QUIC initial keys from a TLS 1.3 ciphersuite and a QUIC key generation algorithm.
#[non_exhaustive]
#[derive(Clone, Copy)]
pub struct Suite {
    /// The TLS 1.3 ciphersuite used to derive keys.
    pub inner: &'static Tls13CipherSuite,
    /// The QUIC key generation algorithm used to derive keys.
    pub quic: &'static dyn Algorithm,
}

impl Suite {
    /// Produce a set of initial keys given the connection ID, side and version
    pub fn keys(&self, client_dst_connection_id: &[u8], side: Side, version: Version) -> Keys {
        Keys::initial(version, *self, client_dst_connection_id, side)
    }
}

impl TryFrom<&'static Tls13CipherSuite> for Suite {
    type Error = ApiMisuse;

    fn try_from(suite: &'static Tls13CipherSuite) -> Result<Self, Self::Error> {
        Ok(Self {
            inner: suite,
            quic: suite
                .quic
                .ok_or(ApiMisuse::NoQuicCompatibleCipherSuites)?,
        })
    }
}

impl fmt::Debug for Suite {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Suite")
            .field("inner", &self.inner)
            .finish_non_exhaustive()
    }
}

/// Complete set of keys used to communicate with the peer
#[expect(clippy::exhaustive_structs)]
pub struct Keys {
    /// Encrypts outgoing packets
    pub local: DirectionalKeys,
    /// Decrypts incoming packets
    pub remote: DirectionalKeys,
}

impl Keys {
    /// Construct keys for use with initial packets
    pub fn initial(
        version: Version,
        suite: Suite,
        client_dst_connection_id: &[u8],
        side: Side,
    ) -> Self {
        const CLIENT_LABEL: &[u8] = b"client in";
        const SERVER_LABEL: &[u8] = b"server in";
        let salt = version.initial_salt();
        let hs_secret = suite
            .inner
            .hkdf_provider
            .extract_from_secret(Some(salt), client_dst_connection_id);

        let secrets = Secrets {
            client: hkdf_expand_label_block(hs_secret.as_ref(), CLIENT_LABEL, &[]),
            server: hkdf_expand_label_block(hs_secret.as_ref(), SERVER_LABEL, &[]),
            suite,
            side,
            version,
        };

        Self::new(&secrets)
    }

    fn new(secrets: &Secrets) -> Self {
        let (local, remote) = secrets.local_remote();
        Self {
            local: DirectionalKeys::new(secrets.suite, local, secrets.version),
            remote: DirectionalKeys::new(secrets.suite, remote, secrets.version),
        }
    }
}

/// Key material for use in QUIC packet spaces
///
/// QUIC uses 4 different sets of keys (and progressive key updates for long-running connections):
///
/// * Initial: these can be created from [`Keys::initial()`]
/// * 0-RTT keys: can be retrieved from [`Connection::zero_rtt_keys()`]
/// * Handshake: these are returned from [`Connection::events()`] after `ClientHello` and
///   `ServerHello` messages have been exchanged
/// * 1-RTT keys: these are returned from [`Connection::events()`] after the handshake is done
///
/// Once the 1-RTT keys have been exchanged, either side may initiate a key update. Progressive
/// update keys can be obtained from the [`Secrets`] returned in [`KeyChange::OneRtt`]. Note that
/// only packet keys are updated by key updates; header protection keys remain the same.
#[expect(clippy::exhaustive_enums)]
pub enum KeyChange {
    /// Keys for the handshake space
    Handshake {
        /// Header and packet keys for the handshake space
        keys: Keys,
    },
    /// Keys for 1-RTT data
    OneRtt {
        /// Header and packet keys for 1-RTT data
        keys: Keys,
        /// Secrets to derive updated keys from
        next: Secrets,
    },
}

impl fmt::Debug for KeyChange {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Handshake { .. } => f
                .debug_struct("Handshake")
                .finish_non_exhaustive(),
            Self::OneRtt { .. } => f
                .debug_struct("OneRtt")
                .finish_non_exhaustive(),
        }
    }
}

/// QUIC protocol version
///
/// Governs version-specific behavior in the TLS layer
#[non_exhaustive]
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
pub enum Version {
    /// First stable RFC
    #[default]
    V1,
    /// Anti-ossification variant of V1
    V2,
}

impl Version {
    fn initial_salt(self) -> &'static [u8; 20] {
        match self {
            Self::V1 => &[
                // https://www.rfc-editor.org/rfc/rfc9001.html#name-initial-secrets
                0x38, 0x76, 0x2c, 0xf7, 0xf5, 0x59, 0x34, 0xb3, 0x4d, 0x17, 0x9a, 0xe6, 0xa4, 0xc8,
                0x0c, 0xad, 0xcc, 0xbb, 0x7f, 0x0a,
            ],
            Self::V2 => &[
                // https://tools.ietf.org/html/rfc9369.html#name-initial-salt
                0x0d, 0xed, 0xe3, 0xde, 0xf7, 0x00, 0xa6, 0xdb, 0x81, 0x93, 0x81, 0xbe, 0x6e, 0x26,
                0x9d, 0xcb, 0xf9, 0xbd, 0x2e, 0xd9,
            ],
        }
    }

    /// Key derivation label for packet keys.
    pub(crate) fn packet_key_label(&self) -> &'static [u8] {
        match self {
            Self::V1 => b"quic key",
            Self::V2 => b"quicv2 key",
        }
    }

    /// Key derivation label for packet "IV"s.
    pub(crate) fn packet_iv_label(&self) -> &'static [u8] {
        match self {
            Self::V1 => b"quic iv",
            Self::V2 => b"quicv2 iv",
        }
    }

    /// Key derivation for header keys.
    pub(crate) fn header_key_label(&self) -> &'static [u8] {
        match self {
            Self::V1 => b"quic hp",
            Self::V2 => b"quicv2 hp",
        }
    }

    fn key_update_label(&self) -> &'static [u8] {
        match self {
            Self::V1 => b"quic ku",
            Self::V2 => b"quicv2 ku",
        }
    }
}

#[cfg(all(test, any(target_arch = "aarch64", target_arch = "x86_64")))]
mod tests {
    use super::*;
    use crate::crypto::TLS13_TEST_SUITE;
    use crate::crypto::tls13::OkmBlock;
    use crate::quic::{HeaderProtectionKey, Side, Version};

    #[test]
    fn key_update_test_vector() {
        fn equal_okm(x: &OkmBlock, y: &OkmBlock) -> bool {
            x.as_ref() == y.as_ref()
        }

        let mut secrets = Secrets {
            // Constant dummy values for reproducibility
            client: OkmBlock::new(
                &[
                    0xb8, 0x76, 0x77, 0x08, 0xf8, 0x77, 0x23, 0x58, 0xa6, 0xea, 0x9f, 0xc4, 0x3e,
                    0x4a, 0xdd, 0x2c, 0x96, 0x1b, 0x3f, 0x52, 0x87, 0xa6, 0xd1, 0x46, 0x7e, 0xe0,
                    0xae, 0xab, 0x33, 0x72, 0x4d, 0xbf,
                ][..],
            ),
            server: OkmBlock::new(
                &[
                    0x42, 0xdc, 0x97, 0x21, 0x40, 0xe0, 0xf2, 0xe3, 0x98, 0x45, 0xb7, 0x67, 0x61,
                    0x34, 0x39, 0xdc, 0x67, 0x58, 0xca, 0x43, 0x25, 0x9b, 0x87, 0x85, 0x06, 0x82,
                    0x4e, 0xb1, 0xe4, 0x38, 0xd8, 0x55,
                ][..],
            ),
            suite: Suite {
                inner: TLS13_TEST_SUITE,
                quic: &FakeAlgorithm,
            },
            side: Side::Client,
            version: Version::V1,
        };
        secrets.update();

        assert!(equal_okm(
            &secrets.client,
            &OkmBlock::new(
                &[
                    0x42, 0xca, 0xc8, 0xc9, 0x1c, 0xd5, 0xeb, 0x40, 0x68, 0x2e, 0x43, 0x2e, 0xdf,
                    0x2d, 0x2b, 0xe9, 0xf4, 0x1a, 0x52, 0xca, 0x6b, 0x22, 0xd8, 0xe6, 0xcd, 0xb1,
                    0xe8, 0xac, 0xa9, 0x6, 0x1f, 0xce
                ][..]
            )
        ));
        assert!(equal_okm(
            &secrets.server,
            &OkmBlock::new(
                &[
                    0xeb, 0x7f, 0x5e, 0x2a, 0x12, 0x3f, 0x40, 0x7d, 0xb4, 0x99, 0xe3, 0x61, 0xca,
                    0xe5, 0x90, 0xd4, 0xd9, 0x92, 0xe1, 0x4b, 0x7a, 0xce, 0x3, 0xc2, 0x44, 0xe0,
                    0x42, 0x21, 0x15, 0xb6, 0xd3, 0x8a
                ][..]
            )
        ));
    }

    struct FakeAlgorithm;

    impl Algorithm for FakeAlgorithm {
        fn packet_key(&self, _key: AeadKey, _iv: Iv) -> Box<dyn PacketKey> {
            unimplemented!()
        }

        fn header_protection_key(&self, _key: AeadKey) -> Box<dyn HeaderProtectionKey> {
            unimplemented!()
        }

        fn aead_key_len(&self) -> usize {
            16
        }
    }

    #[test]
    fn auto_traits() {
        fn assert_auto<T: Send + Sync>() {}
        assert_auto::<Box<dyn PacketKey>>();
        assert_auto::<Box<dyn HeaderProtectionKey>>();
    }
}