qssl 0.1.0-alpha

//! True Quantum-Native Protocol Implementation
//!
//! This is NOT just TLS/SSH with quantum crypto - it's designed from the ground up
//! to be resistant to quantum analysis attacks.

pub mod frame;
pub mod handshake;
pub mod transport;
pub mod stealth;
pub mod sphincs_kem;  // Using SPHINCS+/Falcon instead of vulnerable Kyber

use crate::crypto::{symmetric, hash};
use self::sphincs_kem::{SphincsKem, HybridKem};
use crate::{QsslError, QsslResult};
use rand::RngCore;
use std::time::{SystemTime, UNIX_EPOCH};

/// Quantum-native protocol version
pub const QNSP_VERSION: u16 = 0x0100;  // 1.0

/// Fixed frame size to prevent traffic analysis
pub const QUANTUM_FRAME_SIZE: usize = 768;  // Matches Kyber ciphertext size

/// Frame types (encrypted, so adversary can't distinguish)
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FrameType {
    Noise = 0x00,      // Dummy traffic to hide patterns
    Handshake = 0x01,  // Handshake messages
    Data = 0x02,       // Application data
    Control = 0x03,    // Control messages
    Quantum = 0x04,    // QKD or quantum-specific data
}

/// Quantum-native connection state
pub struct QuantumConnection {
    /// Current frame sequence number
    sequence: u64,

    /// Master secret for key derivation
    master_secret: Vec<u8>,

    /// Frame encryption key (rotated frequently)
    frame_key: symmetric::SymmetricKey,

    /// Channel encryption key (session lifetime)
    channel_key: symmetric::SymmetricKey,

    /// Authentication key
    auth_key: Vec<u8>,

    /// Continuous stream of frames
    frame_stream: FrameStream,

    /// Stealth mode settings
    stealth_config: StealthConfig,
}

/// Configuration for stealth/obfuscation features
#[derive(Debug, Clone)]
pub struct StealthConfig {
    /// Enable maximum traffic padding
    pub max_padding: bool,

    /// Generate dummy traffic
    pub dummy_traffic: bool,

    /// Randomize timing between frames
    pub timing_obfuscation: bool,

    /// Minimum frames per second (for dummy traffic)
    pub min_frame_rate: u32,

    /// Use quantum RNG if available
    pub quantum_rng: bool,
}

impl Default for StealthConfig {
    fn default() -> Self {
        Self {
            max_padding: true,           // Always pad to hide message sizes
            dummy_traffic: true,          // Generate noise frames
            timing_obfuscation: true,     // Randomize timing
            min_frame_rate: 10,           // At least 10 frames/sec
            quantum_rng: false,           // Use if available
        }
    }
}

/// Continuous bidirectional frame stream
pub struct FrameStream {
    /// Incoming frame buffer
    incoming: Vec<QuantumFrame>,

    /// Outgoing frame buffer
    outgoing: Vec<QuantumFrame>,

    /// Noise generator for dummy traffic
    noise_generator: NoiseGenerator,
}

/// Quantum frame structure - all frames are exactly 768 bytes
#[repr(C)]
pub struct QuantumFrame {
    /// Encrypted header (17 bytes)
    header: EncryptedHeader,

    /// Payload (719 bytes) - includes random padding
    payload: [u8; 719],

    /// MAC for authentication (32 bytes)
    mac: [u8; 32],
}

/// Encrypted frame header
#[repr(C)]
struct EncryptedHeader {
    sequence: [u8; 8],     // Sequence number (encrypted)
    timestamp: [u8; 8],    // Microsecond timestamp (encrypted)
    frame_type: u8,        // Frame type (encrypted)
}

/// Generate dummy traffic to hide real communication patterns
struct NoiseGenerator {
    enabled: bool,
    rate: u32,  // Frames per second
    last_noise: SystemTime,
}

impl NoiseGenerator {
    fn new(rate: u32) -> Self {
        Self {
            enabled: true,
            rate,
            last_noise: SystemTime::now(),
        }
    }

    /// Generate a noise frame if needed
    fn maybe_generate_noise(&mut self) -> Option<QuantumFrame> {
        if !self.enabled {
            return None;
        }

        let elapsed = self.last_noise.elapsed().unwrap_or_default();
        let interval = std::time::Duration::from_millis(1000 / self.rate as u64);

        if elapsed >= interval {
            self.last_noise = SystemTime::now();
            Some(self.generate_noise_frame())
        } else {
            None
        }
    }

    /// Generate a random noise frame
    fn generate_noise_frame(&self) -> QuantumFrame {
        let mut frame = QuantumFrame {
            header: EncryptedHeader {
                sequence: [0; 8],
                timestamp: [0; 8],
                frame_type: FrameType::Noise as u8,
            },
            payload: [0; 719],
            mac: [0; 32],
        };

        // Fill with random data
        rand::thread_rng().fill_bytes(&mut frame.payload);
        rand::thread_rng().fill_bytes(&mut frame.mac);

        frame
    }
}

impl QuantumConnection {
    /// Create new quantum-native connection
    pub async fn new(stealth_config: StealthConfig) -> QsslResult<Self> {
        // Generate initial keys
        let master_secret = {
            let mut secret = vec![0u8; 48];
            rand::thread_rng().fill_bytes(&mut secret);
            secret
        };

        // Derive keys
        let frame_key = symmetric::SymmetricKey::generate(
            crate::crypto::SymmetricCipher::ChaCha20Poly1305
        );
        let channel_key = symmetric::SymmetricKey::generate(
            crate::crypto::SymmetricCipher::Aes256Gcm
        );

        let mut auth_key = vec![0u8; 32];
        rand::thread_rng().fill_bytes(&mut auth_key);

        Ok(Self {
            sequence: 0,
            master_secret,
            frame_key,
            channel_key,
            auth_key,
            frame_stream: FrameStream {
                incoming: Vec::new(),
                outgoing: Vec::new(),
                noise_generator: NoiseGenerator::new(stealth_config.min_frame_rate),
            },
            stealth_config,
        })
    }

    /// Perform quantum-native handshake
    pub async fn handshake(&mut self, is_client: bool) -> QsslResult<()> {
        if is_client {
            self.client_handshake().await
        } else {
            self.server_handshake().await
        }
    }

    /// Client-side handshake (indistinguishable from noise)
    async fn client_handshake(&mut self) -> QsslResult<()> {
        // Generate SPHINCS+/Falcon KEM (not vulnerable Kyber)
        let kem = SphincsKem::new()?;

        // Send public key hidden in noise frames
        use pqcrypto_traits::sign::PublicKey as _;
        let pk_bytes = kem.identity_pk.as_bytes();
        self.send_handshake_data(pk_bytes).await?;

        // Receive ciphertext hidden in noise frames
        let ciphertext_bytes = self.receive_handshake_data().await?;

        // Get peer's public key (sent separately)
        let peer_pk = self.receive_handshake_data().await?;

        // Decapsulate using SPHINCS+ KEM
        let shared_secret = kem.decapsulate(&ciphertext_bytes, &peer_pk)?;

        // Derive new keys from shared secret
        self.derive_session_keys(&shared_secret)?;

        Ok(())
    }

    /// Server-side handshake (indistinguishable from noise)
    async fn server_handshake(&mut self) -> QsslResult<()> {
        // Generate our KEM
        let kem = SphincsKem::new()?;

        // Receive peer's public key hidden in noise frames
        let peer_pk_bytes = self.receive_handshake_data().await?;

        // Encapsulate using SPHINCS+
        let (ciphertext, shared_secret) = kem.encapsulate(&peer_pk_bytes)?;

        // Send ciphertext and our public key hidden in noise frames
        self.send_handshake_data(&ciphertext).await?;

        use pqcrypto_traits::sign::PublicKey as _;
        let our_pk = kem.identity_pk.as_bytes();
        self.send_handshake_data(our_pk).await?;

        // Derive new keys from shared secret
        self.derive_session_keys(&shared_secret)?;

        Ok(())
    }

    /// Send handshake data hidden in noise frames
    async fn send_handshake_data(&mut self, data: &[u8]) -> QsslResult<()> {
        // Fragment data across multiple noise frames
        // Each frame carries only a small part to avoid patterns

        let chunk_size = 64;  // Small chunks to hide in noise

        for chunk in data.chunks(chunk_size) {
            // Generate several noise frames
            for _ in 0..rand::random::<u8>() % 5 + 1 {
                self.send_noise_frame().await?;
            }

            // Send actual data frame (looks like noise)
            self.send_frame(FrameType::Handshake, chunk).await?;

            // More noise frames
            for _ in 0..rand::random::<u8>() % 3 + 1 {
                self.send_noise_frame().await?;
            }

            // Random delay to prevent timing analysis
            if self.stealth_config.timing_obfuscation {
                let delay = std::time::Duration::from_micros(
                    rand::random::<u64>() % 10000
                );
                tokio::time::sleep(delay).await;
            }
        }

        Ok(())
    }

    /// Receive handshake data from noise frames
    async fn receive_handshake_data(&mut self) -> QsslResult<Vec<u8>> {
        let mut data = Vec::new();
        let expected_size = 800;  // Kyber768 public key size

        while data.len() < expected_size {
            // Process incoming frames
            let frame = self.receive_frame().await?;

            // Only process handshake frames, ignore noise
            if frame.header.frame_type == FrameType::Handshake as u8 {
                // Extract actual data from frame
                let payload_len = u16::from_be_bytes([frame.payload[0], frame.payload[1]]);
                let payload = &frame.payload[2..2 + payload_len as usize];
                data.extend_from_slice(payload);
            }
        }

        Ok(data)
    }

    /// Send a frame (all frames look identical)
    async fn send_frame(&mut self, frame_type: FrameType, data: &[u8]) -> QsslResult<()> {
        let mut frame = QuantumFrame {
            header: EncryptedHeader {
                sequence: self.sequence.to_be_bytes(),
                timestamp: self.get_timestamp(),
                frame_type: frame_type as u8,
            },
            payload: [0; 719],
            mac: [0; 32],
        };

        // Add data length and data
        let data_len = data.len().min(717);  // Leave room for length field
        frame.payload[0..2].copy_from_slice(&(data_len as u16).to_be_bytes());
        frame.payload[2..2 + data_len].copy_from_slice(&data[..data_len]);

        // Fill rest with random padding
        rand::thread_rng().fill_bytes(&mut frame.payload[2 + data_len..]);

        // Encrypt header in place
        self.encrypt_header(&mut frame.header)?;

        // Calculate MAC
        frame.mac = self.calculate_mac(&frame)?;

        // Add to outgoing stream
        self.frame_stream.outgoing.push(frame);
        self.sequence += 1;

        Ok(())
    }

    /// Send noise frame
    async fn send_noise_frame(&mut self) -> QsslResult<()> {
        let mut noise = vec![0u8; 717];
        rand::thread_rng().fill_bytes(&mut noise);
        self.send_frame(FrameType::Noise, &noise).await
    }

    /// Receive a frame
    async fn receive_frame(&mut self) -> QsslResult<QuantumFrame> {
        // In real implementation, this would read from network
        // For now, simulate with dummy frame
        Ok(self.frame_stream.noise_generator.generate_noise_frame())
    }

    /// Derive session keys from shared secret
    fn derive_session_keys(&mut self, shared_secret: &[u8]) -> QsslResult<()> {
        // Use quantum-resistant KDF
        let kdf_output = hash::hkdf(
            crate::crypto::HashAlgorithm::Sha3_512,
            shared_secret,
            Some(&self.master_secret),
            b"quantum-native-session-keys",
            96,
        )?;

        // Update keys
        self.frame_key = symmetric::SymmetricKey::new(
            crate::crypto::SymmetricCipher::ChaCha20Poly1305,
            kdf_output[0..32].to_vec(),
        )?;

        self.channel_key = symmetric::SymmetricKey::new(
            crate::crypto::SymmetricCipher::Aes256Gcm,
            kdf_output[32..64].to_vec(),
        )?;

        self.auth_key = kdf_output[64..96].to_vec();

        Ok(())
    }

    /// Get current timestamp in microseconds
    fn get_timestamp(&self) -> [u8; 8] {
        let timestamp = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap_or_default()
            .as_micros() as u64;
        timestamp.to_be_bytes()
    }

    /// Encrypt header in place
    fn encrypt_header(&self, header: &mut EncryptedHeader) -> QsslResult<()> {
        // XOR with key stream for speed
        // In production, use proper AEAD
        for (i, byte) in header.sequence.iter_mut().enumerate() {
            *byte ^= self.auth_key[i % self.auth_key.len()];
        }
        for (i, byte) in header.timestamp.iter_mut().enumerate() {
            *byte ^= self.auth_key[(i + 8) % self.auth_key.len()];
        }
        header.frame_type ^= self.auth_key[16];
        Ok(())
    }

    /// Calculate MAC for frame authentication
    fn calculate_mac(&self, frame: &QuantumFrame) -> QsslResult<[u8; 32]> {
        use hmac::{Hmac, Mac};
        use sha2::Sha256;

        let mut mac = Hmac::<Sha256>::new_from_slice(&self.auth_key)
            .map_err(|e| QsslError::Crypto(format!("MAC error: {}", e)))?;

        // MAC covers everything except the MAC field itself
        mac.update(&frame.header.sequence);
        mac.update(&frame.header.timestamp);
        mac.update(&[frame.header.frame_type]);
        mac.update(&frame.payload);

        let result = mac.finalize();
        let mut mac_bytes = [0u8; 32];
        mac_bytes.copy_from_slice(result.into_bytes().as_slice());
        Ok(mac_bytes)
    }
}

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

    #[test]
    fn test_frame_size() {
        assert_eq!(std::mem::size_of::<QuantumFrame>(), QUANTUM_FRAME_SIZE);
    }

    #[tokio::test]
    async fn test_quantum_connection() {
        let config = StealthConfig::default();
        let conn = QuantumConnection::new(config).await.unwrap();
        assert_eq!(conn.sequence, 0);
    }
}