internet 0.0.3

//! Handshake encoding following [RFC 2246].
//!
//! Encoding is supported for the following structures:
//!
//!  - [`HandshakeType`]
//!  - [`Handshake`]
//!  - [`HelloRequest`]
//!  - [`Random`]
//!  - [`SessionId`]
//!  - [`CompressionMethod`]
//!  - [`ClientHello`]
//!  - [`ServerHello`]
//!  - [`Asn1Cert`]
//!  - [`Certificate`]
//!  - [`KeyExchangeAlgorithm`]
//!  - [`SignatureAlgorithm`]
//!  - [`ClientCertificateType`]
//!  - [`Signature`]
//!  - [`CertificateRequest`]
//!  - [`ServerHelloDone`]
//!  - [`CertificateVerify`]
//!  - [`Finished`]
//!
//! [RFC 2246]: https://datatracker.ietf.org/doc/html/rfc2246

use crate::{
    Buf,
    BufError::{self},
    BufMut, BufResult, Codec, Cursor,
    tls::{LengthPrefix, ProtocolVersion, TlsVec, u24},
    tls1_0::CipherSuite,
};

/// A Handshake Type following [Section A.4.1].
///
/// [Section A.4.1]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.1
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(u8)]
pub enum HandshakeType {
    /// hello_request(0)
    HelloRequest = 0,
    /// client_hello(1)
    ClientHello = 1,
    /// server_hello(2)
    ServerHello = 2,
    /// certificate(11)
    Certificate = 11,
    /// server_key_exchange(12)
    ServerKeyExchange = 12,
    /// certificate_request(13)
    CertificateRequest = 13,
    /// server_hello_done(14)
    ServerHelloDone = 14,
    /// certificate_verify(15)
    CertificateVerify = 15,
    /// client_key_exchange(16)
    ClientKeyExchange = 16,
    /// finished(20)
    Finished = 20,
}

impl Codec for HandshakeType {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        (*self as u8).encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        match u8::decode(reader, ())? {
            x if x == (Self::HelloRequest as u8) => Ok(Self::HelloRequest),
            x if x == (Self::ClientHello as u8) => Ok(Self::ClientHello),
            x if x == (Self::ServerHello as u8) => Ok(Self::ServerHello),
            x if x == (Self::Certificate as u8) => Ok(Self::Certificate),
            x if x == (Self::ServerKeyExchange as u8) => Ok(Self::ServerKeyExchange),
            x if x == (Self::CertificateRequest as u8) => Ok(Self::CertificateRequest),
            x if x == (Self::ServerHelloDone as u8) => Ok(Self::ServerHelloDone),
            x if x == (Self::CertificateVerify as u8) => Ok(Self::CertificateVerify),
            x if x == (Self::ClientKeyExchange as u8) => Ok(Self::ClientKeyExchange),
            x if x == (Self::Finished as u8) => Ok(Self::Finished),
            _ => Err(BufError::UnexpectedValue),
        }
    }
}

/// A Handshake message following [Section A.4.2].
///
/// [Section A.4.2]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.2
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Handshake {
    /// The type of the handshake message.
    pub msg_type: HandshakeType,
    /// The body of the handshake message.
    pub msg: Vec<u8>,
}

impl Codec for Handshake {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.msg_type.encode(writer, ())?;
        let len = u24::from_usize(self.msg.len())?;
        len.encode(writer, ())?;
        writer.write_slice(&self.msg)
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        let msg_type = HandshakeType::decode(reader, ())?;
        let length_u24 = u24::decode(reader, ())?;
        let length = length_u24.as_usize();

        if reader.remaining() < length {
            return Err(BufError::UnexpectedEof);
        }

        let mut msg = vec![0u8; length];
        reader.read_into(&mut msg)?;

        Ok(Self { msg_type, msg })
    }
}

/// A Hello Request message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct HelloRequest;

impl Codec for HelloRequest {
    fn encode<W: BufMut>(&self, _writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        Ok(())
    }

    fn decode<R: Buf>(_reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self)
    }
}

/// A Random structure following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Random(pub [u8; 32]);

impl Random {
    /// Creates a new Random structure with placeholder values.
    pub fn random() -> Self {
        Self([0x32u8; 32])
    }
}

impl Codec for Random {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        writer.write_array(&self.0)
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self(reader.read_array::<32>()?))
    }
}

/// A Session ID following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct SessionId(pub TlsVec<u8, u8>);

impl Codec for SessionId {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.0.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self(TlsVec::<u8, u8>::decode(reader, ())?))
    }
}

/// A Compression Method following [Section A.3].
///
/// [Section A.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(u8)]
pub enum CompressionMethod {
    /// null(0)
    Null = 0,
}

impl Codec for CompressionMethod {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        (*self as u8).encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        match u8::decode(reader, ())? {
            x if x == (Self::Null as u8) => Ok(Self::Null),
            _ => Err(BufError::UnexpectedValue),
        }
    }
}

/// A Client Hello message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ClientHello {
    /// The protocol version.
    pub client_version: ProtocolVersion,
    /// The random structure.
    pub random: Random,
    /// The session ID.
    pub session_id: SessionId,
    /// The cipher suites.
    pub cipher_suites: TlsVec<CipherSuite, u16>,
    /// The compression methods.
    pub compression_methods: TlsVec<CompressionMethod, u8>,
}

impl Codec for ClientHello {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.client_version.encode(writer, ())?;
        self.random.encode(writer, ())?;
        self.session_id.encode(writer, ())?;
        self.cipher_suites.encode(writer, ())?;
        self.compression_methods.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self {
            client_version: ProtocolVersion::decode(reader, ())?,
            random: Random::decode(reader, ())?,
            session_id: SessionId::decode(reader, ())?,
            cipher_suites: TlsVec::<CipherSuite, u16>::decode(reader, ())?,
            compression_methods: TlsVec::<CompressionMethod, u8>::decode(reader, ())?,
        })
    }
}

/// A Server Hello message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ServerHello {
    /// The protocol version.
    pub server_version: ProtocolVersion,
    /// The random structure.
    pub random: Random,
    /// The session ID.
    pub session_id: SessionId,
    /// The cipher suite.
    pub cipher_suite: CipherSuite,
    /// The compression method.
    pub compression_method: CompressionMethod,
}

impl Codec for ServerHello {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.server_version.encode(writer, ())?;
        self.random.encode(writer, ())?;
        self.session_id.encode(writer, ())?;
        self.cipher_suite.encode(writer, ())?;
        self.compression_method.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self {
            server_version: ProtocolVersion::decode(reader, ())?,
            random: Random::decode(reader, ())?,
            session_id: SessionId::decode(reader, ())?,
            cipher_suite: CipherSuite::decode(reader, ())?,
            compression_method: CompressionMethod::decode(reader, ())?,
        })
    }
}

/// An ASN.1 Certificate following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Asn1Cert(pub TlsVec<u8, u24>);

impl Codec for Asn1Cert {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.0.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self(TlsVec::<u8, u24>::decode(reader, ())?))
    }
}

/// A Certificate message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Certificate {
    /// The list of certificates.
    pub certificate_list: TlsVec<Asn1Cert, u24>,
}

impl Codec for Certificate {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.certificate_list.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self {
            certificate_list: TlsVec::<Asn1Cert, u24>::decode(reader, ())?,
        })
    }
}

/// A Key Exchange Algorithm following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(u8)]
pub enum KeyExchangeAlgorithm {
    /// rsa
    Rsa = 0,
    /// diffie_hellman
    DiffieHellman = 1,
}

impl Codec for KeyExchangeAlgorithm {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        (*self as u8).encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        match u8::decode(reader, ())? {
            x if x == (Self::Rsa as u8) => Ok(Self::Rsa),
            x if x == (Self::DiffieHellman as u8) => Ok(Self::DiffieHellman),
            _ => Err(BufError::UnexpectedValue),
        }
    }
}

/// A Signature Algorithm following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(u8)]
pub enum SignatureAlgorithm {
    /// anonymous
    Anonymous = 0,
    /// rsa
    Rsa = 1,
    /// dsa
    Dsa = 2,
}

impl Codec for SignatureAlgorithm {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        (*self as u8).encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        match u8::decode(reader, ())? {
            x if x == (Self::Anonymous as u8) => Ok(Self::Anonymous),
            x if x == (Self::Rsa as u8) => Ok(Self::Rsa),
            x if x == (Self::Dsa as u8) => Ok(Self::Dsa),
            _ => Err(BufError::UnexpectedValue),
        }
    }
}

/// A Client Certificate Type following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(u8)]
pub enum ClientCertificateType {
    /// rsa_sign(1)
    RsaSign = 1,
    /// dss_sign(2)
    DssSign = 2,
    /// rsa_fixed_dh(3)
    RsaFixedDh = 3,
    /// dss_fixed_dh(4)
    DssFixedDh = 4,
}

impl Codec for ClientCertificateType {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        (*self as u8).encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        match u8::decode(reader, ())? {
            x if x == (Self::RsaSign as u8) => Ok(Self::RsaSign),
            x if x == (Self::DssSign as u8) => Ok(Self::DssSign),
            x if x == (Self::RsaFixedDh as u8) => Ok(Self::RsaFixedDh),
            x if x == (Self::DssFixedDh as u8) => Ok(Self::DssFixedDh),
            _ => Err(BufError::UnexpectedValue),
        }
    }
}

/// A Signature following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Signature(pub TlsVec<u8, u16>);

impl Codec for Signature {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.0.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self(TlsVec::<u8, u16>::decode(reader, ())?))
    }
}

/// A Distinguished Name following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct DistinguishedName(pub TlsVec<u8, u16>);

impl Codec for DistinguishedName {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.0.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self(TlsVec::<u8, u16>::decode(reader, ())?))
    }
}

/// A Certificate Request message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct CertificateRequest {
    /// The certificate types.
    pub certificate_types: TlsVec<ClientCertificateType, u8>,
    /// The certificate authorities.
    pub certificate_authorities: TlsVec<DistinguishedName, u16>,
}

impl Codec for CertificateRequest {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.certificate_types.encode(writer, ())?;
        self.certificate_authorities.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self {
            certificate_types: TlsVec::<ClientCertificateType, u8>::decode(reader, ())?,
            certificate_authorities: TlsVec::<DistinguishedName, u16>::decode(reader, ())?,
        })
    }
}

/// A Server Hello Done message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ServerHelloDone;

impl Codec for ServerHelloDone {
    fn encode<W: BufMut>(&self, _writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        Ok(())
    }

    fn decode<R: Buf>(_reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self)
    }
}

/// A Certificate Verify message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct CertificateVerify {
    /// The signature.
    pub signature: Signature,
}

impl Codec for CertificateVerify {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.signature.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self {
            signature: Signature::decode(reader, ())?,
        })
    }
}

/// A Finished message following [Section A.4.3].
///
/// [Section A.4.3]: https://datatracker.ietf.org/doc/html/rfc2246#appendix-A.4.3
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Finished {
    /// The verify data.
    pub verify_data: [u8; 12],
}

impl Codec for Finished {
    fn encode<W: BufMut>(&self, writer: &mut Cursor<W>, _: ()) -> BufResult<()> {
        self.verify_data.encode(writer, ())
    }

    fn decode<R: Buf>(reader: &mut Cursor<R>, _: ()) -> BufResult<Self> {
        Ok(Self {
            verify_data: reader.read_array::<12>()?,
        })
    }
}

#[cfg(test)]
mod tests {
    use core::fmt::Debug;

    use super::{HandshakeType, HelloRequest};
    use crate::{Codec, Cursor};

    fn codec_roundtrip<T: Codec<C> + Debug + Eq, C: Copy>(
        etalon_struct: T,
        etalon_bytes: &[u8],
        context: C,
    ) {
        let mut encoded_bytes = vec![];
        {
            let writer = &mut Cursor::new(&mut encoded_bytes);
            etalon_struct.encode(writer, context).unwrap();
        }
        assert_eq!(etalon_bytes, &encoded_bytes);

        let decoded_struct = {
            let reader = &mut Cursor::new(&mut encoded_bytes);
            T::decode(reader, context).unwrap()
        };
        assert_eq!(etalon_struct, decoded_struct);

        encoded_bytes.fill(0x00);
        {
            let writer = &mut Cursor::new(&mut encoded_bytes);
            decoded_struct.encode(writer, context).unwrap();
        }
        assert_eq!(etalon_bytes, &encoded_bytes);
    }

    #[test]
    fn handshake_type() {
        let etalon_bytes = &[0x01];
        let etalon_struct = HandshakeType::ClientHello;

        codec_roundtrip(etalon_struct, etalon_bytes, ());
    }

    #[test]
    fn hello_request() {
        let etalon_bytes = &[];
        let etalon_struct = HelloRequest;

        codec_roundtrip(etalon_struct, etalon_bytes, ());
    }
}