oximedia-net 0.1.5

//! DTLS (Datagram Transport Layer Security) wrapper.
//!
//! This module provides DTLS encryption for WebRTC connections.

#![allow(dead_code)]
#![allow(clippy::too_many_arguments)]

use crate::error::{NetError, NetResult};
use rustls::pki_types::{CertificateDer, PrivateKeyDer};
use sha2::{Digest, Sha256};
use std::sync::Arc;
use tokio::net::UdpSocket;

/// DTLS role.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DtlsRole {
    /// Client role (active).
    Client,
    /// Server role (passive).
    Server,
}

impl DtlsRole {
    /// Parses from SDP setup attribute.
    #[must_use]
    pub fn from_setup(setup: &str) -> Option<Self> {
        match setup {
            "active" => Some(Self::Client),
            "passive" => Some(Self::Server),
            "actpass" => Some(Self::Server), // Default to server
            _ => None,
        }
    }

    /// Returns the SDP setup attribute.
    #[must_use]
    pub const fn to_setup(&self) -> &'static str {
        match self {
            Self::Client => "active",
            Self::Server => "passive",
        }
    }
}

/// DTLS fingerprint.
#[derive(Debug, Clone)]
pub struct DtlsFingerprint {
    /// Hash algorithm.
    pub algorithm: String,
    /// Fingerprint value (hex).
    pub value: String,
}

impl DtlsFingerprint {
    /// Creates a SHA-256 fingerprint from certificate.
    #[must_use]
    pub fn from_certificate(cert: &CertificateDer) -> Self {
        let mut hasher = Sha256::new();
        hasher.update(cert.as_ref());
        let hash = hasher.finalize();

        let value = hash
            .iter()
            .map(|b| format!("{b:02X}"))
            .collect::<Vec<_>>()
            .join(":");

        Self {
            algorithm: "sha-256".to_string(),
            value,
        }
    }

    /// Formats for SDP.
    #[must_use]
    pub fn to_sdp(&self) -> String {
        format!("{} {}", self.algorithm, self.value)
    }
}

/// DTLS configuration.
pub struct DtlsConfig {
    /// Certificate chain.
    pub certificates: Vec<CertificateDer<'static>>,
    /// Private key.
    pub private_key: PrivateKeyDer<'static>,
    /// DTLS role.
    pub role: DtlsRole,
}

impl DtlsConfig {
    /// Creates a new configuration with self-signed certificate.
    pub fn new_self_signed(role: DtlsRole) -> NetResult<Self> {
        let (cert, key) = generate_self_signed_cert()?;

        Ok(Self {
            certificates: vec![cert],
            private_key: key,
            role,
        })
    }

    /// Gets the fingerprint.
    #[must_use]
    pub fn fingerprint(&self) -> DtlsFingerprint {
        DtlsFingerprint::from_certificate(&self.certificates[0])
    }
}

/// DTLS endpoint.
pub struct DtlsEndpoint {
    /// Configuration.
    config: DtlsConfig,
    /// UDP socket.
    socket: Arc<UdpSocket>,
}

impl DtlsEndpoint {
    /// Creates a new DTLS endpoint.
    #[must_use]
    pub fn new(config: DtlsConfig, socket: Arc<UdpSocket>) -> Self {
        Self { config, socket }
    }

    /// Performs DTLS handshake.
    ///
    /// Note: This is a simplified implementation. A production system would
    /// use a full DTLS library like openssl or rustls with DTLS support.
    pub async fn handshake(&self) -> NetResult<DtlsConnection> {
        // In a real implementation, we would:
        // 1. Perform DTLS handshake using rustls or similar
        // 2. Verify remote fingerprint
        // 3. Derive SRTP keys
        // 4. Return established connection

        // For now, return a mock connection
        Ok(DtlsConnection {
            socket: self.socket.clone(),
            srtp_key: vec![0u8; 16],
            srtp_salt: vec![0u8; 14],
        })
    }

    /// Gets the local fingerprint.
    #[must_use]
    pub fn fingerprint(&self) -> DtlsFingerprint {
        self.config.fingerprint()
    }
}

/// Established DTLS connection.
pub struct DtlsConnection {
    /// UDP socket.
    socket: Arc<UdpSocket>,
    /// SRTP master key.
    srtp_key: Vec<u8>,
    /// SRTP master salt.
    srtp_salt: Vec<u8>,
}

impl DtlsConnection {
    /// Sends encrypted data.
    pub async fn send(&self, data: &[u8]) -> NetResult<()> {
        // In a real implementation, encrypt with DTLS
        self.socket
            .send(data)
            .await
            .map_err(|e| NetError::connection(format!("Failed to send: {e}")))?;
        Ok(())
    }

    /// Receives encrypted data.
    pub async fn recv(&self, buf: &mut [u8]) -> NetResult<usize> {
        // In a real implementation, decrypt with DTLS
        self.socket
            .recv(buf)
            .await
            .map_err(|e| NetError::connection(format!("Failed to recv: {e}")))
    }

    /// Gets SRTP keying material.
    #[must_use]
    pub fn srtp_keying_material(&self) -> (&[u8], &[u8]) {
        (&self.srtp_key, &self.srtp_salt)
    }

    /// Gets the underlying socket.
    #[must_use]
    pub fn socket(&self) -> &Arc<UdpSocket> {
        &self.socket
    }
}

/// Generates a self-signed certificate.
fn generate_self_signed_cert() -> NetResult<(CertificateDer<'static>, PrivateKeyDer<'static>)> {
    use ed25519_dalek::pkcs8::EncodePrivateKey;
    use ed25519_dalek::SigningKey;
    use rand::Rng;

    let mut secret = [0u8; 32];
    rand::rng().fill_bytes(&mut secret);
    let signing_key = SigningKey::from_bytes(&secret);
    let pkcs8_doc = signing_key
        .to_pkcs8_der()
        .map_err(|e| NetError::protocol(format!("Failed to encode key as PKCS8: {e}")))?;

    // Create a simple self-signed certificate
    // In production, use rcgen or similar
    let cert_der = create_dummy_cert();
    let key_der = PrivateKeyDer::Pkcs8(pkcs8_doc.as_bytes().to_vec().into());

    Ok((cert_der, key_der))
}

/// Creates a dummy certificate for testing.
fn create_dummy_cert() -> CertificateDer<'static> {
    // This is a minimal valid X.509 certificate structure
    // In production, use rcgen or x509-certificate crate
    let cert_bytes = vec![
        0x30, 0x82, 0x01,
        0x00, // SEQUENCE
             // ... rest of certificate structure
             // This is simplified - a real cert would be much longer
    ];

    CertificateDer::from(cert_bytes)
}

// =============================================
// Extended DTLS simulation types
// =============================================

/// DTLS cipher suite.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DtlsCipherSuite {
    /// TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256 (16-byte key).
    TlsEcdhEcdsaWithAes128GcmSha256,
    /// TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384 (32-byte key).
    TlsEcdhEcdsaWithAes256GcmSha384,
    /// TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (16-byte key).
    TlsEcdheRsaWithAes128GcmSha256,
}

impl DtlsCipherSuite {
    /// Returns the key length in bytes for this cipher suite.
    #[must_use]
    pub const fn key_length_bytes(self) -> usize {
        match self {
            Self::TlsEcdhEcdsaWithAes128GcmSha256 => 16,
            Self::TlsEcdhEcdsaWithAes256GcmSha384 => 32,
            Self::TlsEcdheRsaWithAes128GcmSha256 => 16,
        }
    }
}

/// DTLS handshake state for the simulated session.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DtlsHandshakeState {
    /// New, not yet started.
    New,
    /// Handshake in progress.
    Connecting,
    /// Handshake complete and connection established.
    Connected,
    /// Connection closed.
    Closed,
    /// Handshake failed.
    Failed,
}

/// Fingerprint hash algorithm.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FingerprintAlgorithm {
    /// SHA-256.
    Sha256,
    /// SHA-384.
    Sha384,
    /// SHA-512.
    Sha512,
}

impl FingerprintAlgorithm {
    /// Returns the algorithm name as used in SDP fingerprint attributes.
    #[must_use]
    pub const fn name(self) -> &'static str {
        match self {
            Self::Sha256 => "sha-256",
            Self::Sha384 => "sha-384",
            Self::Sha512 => "sha-512",
        }
    }
}

/// A DTLS fingerprint with algorithm and hex value.
#[derive(Debug, Clone)]
pub struct DtlsFingerprintTyped {
    /// Hash algorithm.
    pub algorithm: FingerprintAlgorithm,
    /// Fingerprint hex value (colon-separated octets).
    pub value: String,
}

impl DtlsFingerprintTyped {
    /// Formats the fingerprint for an SDP attribute.
    #[must_use]
    pub fn to_sdp(&self) -> String {
        format!("{} {}", self.algorithm.name(), self.value)
    }
}

/// Simulated DTLS session (state-machine only, no real crypto).
#[derive(Debug)]
pub struct DtlsSession {
    /// Role (client or server).
    pub role: DtlsRole,
    /// Current handshake state.
    pub state: DtlsHandshakeState,
    /// Local fingerprint.
    pub local_fingerprint: DtlsFingerprintTyped,
    /// Remote fingerprint (set after receiving remote's Hello).
    pub remote_fingerprint: Option<DtlsFingerprintTyped>,
    /// Negotiated cipher suite.
    pub cipher_suite: Option<DtlsCipherSuite>,
    /// Simple session key derived at connect time (for simulation XOR).
    session_key: Vec<u8>,
}

impl DtlsSession {
    /// Creates a new DTLS session with a simulated fingerprint.
    #[must_use]
    pub fn new(role: DtlsRole) -> Self {
        // Generate a deterministic simulated fingerprint from role + timestamp.
        use std::time::{SystemTime, UNIX_EPOCH};
        let ts = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .map(|d| d.as_millis() as u64)
            .unwrap_or(0xDEAD_BEEF);

        // Build a fake 32-byte fingerprint.
        let mut bytes = Vec::with_capacity(32);
        for i in 0..32u8 {
            bytes.push(
                ((ts >> (i % 8)) as u8)
                    .wrapping_add(i)
                    .wrapping_add(if role == DtlsRole::Client { 0xAA } else { 0x55 }),
            );
        }
        let value = bytes
            .iter()
            .map(|b| format!("{b:02X}"))
            .collect::<Vec<_>>()
            .join(":");

        Self {
            role,
            state: DtlsHandshakeState::New,
            local_fingerprint: DtlsFingerprintTyped {
                algorithm: FingerprintAlgorithm::Sha256,
                value,
            },
            remote_fingerprint: None,
            cipher_suite: None,
            session_key: vec![0u8; 16],
        }
    }

    /// Performs the simulated DTLS handshake, transitioning to Connected.
    ///
    /// Returns `true` if the handshake succeeds.
    pub fn connect(&mut self) -> bool {
        self.state = DtlsHandshakeState::Connecting;

        // Select cipher suite.
        self.cipher_suite = Some(DtlsCipherSuite::TlsEcdhEcdsaWithAes128GcmSha256);

        // Derive a simple session key (deterministic for simulation).
        let key_len = self
            .cipher_suite
            .map(|cs| cs.key_length_bytes())
            .unwrap_or(16);
        self.session_key = (0..key_len as u8).collect();

        self.state = DtlsHandshakeState::Connected;
        true
    }

    /// Protects (encrypts) data with a simple XOR using the session key.
    #[must_use]
    pub fn protect(&self, data: &[u8]) -> Vec<u8> {
        if self.session_key.is_empty() {
            return data.to_vec();
        }
        data.iter()
            .enumerate()
            .map(|(i, &b)| b ^ self.session_key[i % self.session_key.len()])
            .collect()
    }

    /// Unprotects (decrypts) data with the same XOR (symmetric).
    #[must_use]
    pub fn unprotect(&self, data: &[u8]) -> Vec<u8> {
        // XOR is its own inverse.
        self.protect(data)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_dtls_role() {
        assert_eq!(DtlsRole::from_setup("active"), Some(DtlsRole::Client));
        assert_eq!(DtlsRole::from_setup("passive"), Some(DtlsRole::Server));
        assert_eq!(DtlsRole::Client.to_setup(), "active");
    }

    #[test]
    fn test_fingerprint_from_cert() {
        let (cert, _) = generate_self_signed_cert().expect("should succeed in test");
        let fp = DtlsFingerprint::from_certificate(&cert);
        assert_eq!(fp.algorithm, "sha-256");
        assert!(fp.value.contains(':'));
    }

    #[test]
    fn test_fingerprint_sdp() {
        let fp = DtlsFingerprint {
            algorithm: "sha-256".to_string(),
            value: "AA:BB:CC:DD".to_string(),
        };
        assert_eq!(fp.to_sdp(), "sha-256 AA:BB:CC:DD");
    }

    // ---- Extended DTLS simulation tests ----

    #[test]
    fn test_cipher_suite_key_length() {
        assert_eq!(
            DtlsCipherSuite::TlsEcdhEcdsaWithAes128GcmSha256.key_length_bytes(),
            16
        );
        assert_eq!(
            DtlsCipherSuite::TlsEcdhEcdsaWithAes256GcmSha384.key_length_bytes(),
            32
        );
        assert_eq!(
            DtlsCipherSuite::TlsEcdheRsaWithAes128GcmSha256.key_length_bytes(),
            16
        );
    }

    #[test]
    fn test_fingerprint_algorithm_name() {
        assert_eq!(FingerprintAlgorithm::Sha256.name(), "sha-256");
        assert_eq!(FingerprintAlgorithm::Sha384.name(), "sha-384");
        assert_eq!(FingerprintAlgorithm::Sha512.name(), "sha-512");
    }

    #[test]
    fn test_dtls_fingerprint_typed_sdp() {
        let fp = DtlsFingerprintTyped {
            algorithm: FingerprintAlgorithm::Sha256,
            value: "AA:BB:CC".to_string(),
        };
        assert_eq!(fp.to_sdp(), "sha-256 AA:BB:CC");
    }

    #[test]
    fn test_dtls_session_new_client() {
        let session = DtlsSession::new(DtlsRole::Client);
        assert_eq!(session.role, DtlsRole::Client);
        assert_eq!(session.state, DtlsHandshakeState::New);
        assert!(session.cipher_suite.is_none());
        assert!(session.remote_fingerprint.is_none());
        assert!(!session.local_fingerprint.value.is_empty());
    }

    #[test]
    fn test_dtls_session_new_server() {
        let session = DtlsSession::new(DtlsRole::Server);
        assert_eq!(session.role, DtlsRole::Server);
        assert_eq!(session.state, DtlsHandshakeState::New);
    }

    #[test]
    fn test_dtls_session_connect() {
        let mut session = DtlsSession::new(DtlsRole::Client);
        let ok = session.connect();
        assert!(ok);
        assert_eq!(session.state, DtlsHandshakeState::Connected);
        assert!(session.cipher_suite.is_some());
    }

    #[test]
    fn test_dtls_session_protect_unprotect() {
        let mut session = DtlsSession::new(DtlsRole::Client);
        session.connect();

        let original = b"Hello DTLS world!";
        let protected = session.protect(original);
        assert_ne!(protected, original.to_vec());

        let unprotected = session.unprotect(&protected);
        assert_eq!(unprotected, original.to_vec());
    }

    #[test]
    fn test_dtls_session_protect_empty() {
        let mut session = DtlsSession::new(DtlsRole::Server);
        session.connect();

        let protected = session.protect(b"");
        assert!(protected.is_empty());
    }

    #[test]
    fn test_dtls_handshake_state_variants() {
        let states = [
            DtlsHandshakeState::New,
            DtlsHandshakeState::Connecting,
            DtlsHandshakeState::Connected,
            DtlsHandshakeState::Closed,
            DtlsHandshakeState::Failed,
        ];
        for &s in &states {
            assert_eq!(s, s);
        }
    }
}