aivpn-server 0.4.0

//! Passive Mask Distribution (Phase 4)
//!
//! Implements steganographic mask delivery through public channels
//!
//! Features:
//! - DNS TXT record decoding
//! - Image LSB steganography
//! - Blockchain OP_RETURN decoding
//! - Telegram/Discord webhook monitoring

use base64::Engine;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use tracing::{debug, info};

use aivpn_common::error::Result;
use aivpn_common::mask::MaskProfile;

/// Passive distribution configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PassiveDistributionConfig {
    /// Enable passive distribution
    pub enable: bool,

    /// DNS TXT record domains to monitor
    pub dns_domains: Vec<String>,

    /// Image URLs for LSB steganography
    pub image_urls: Vec<String>,

    /// Blockchain networks to monitor
    pub blockchain_networks: Vec<BlockchainNetwork>,

    /// Check interval (seconds)
    pub check_interval_secs: u64,
}

impl Default for PassiveDistributionConfig {
    fn default() -> Self {
        Self {
            enable: false,
            dns_domains: vec![
                "mask1.aivpn.network".to_string(),
                "mask2.aivpn.network".to_string(),
            ],
            image_urls: vec![],
            blockchain_networks: vec![BlockchainNetwork::Bitcoin, BlockchainNetwork::Ethereum],
            check_interval_secs: 300, // 5 minutes
        }
    }
}

/// Supported blockchain networks
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub enum BlockchainNetwork {
    Bitcoin,
    Ethereum,
}

/// Mask delivery methods
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum DeliveryMethod {
    DnsTxt {
        domain: String,
        record_type: String,
    },
    ImageLsb {
        url: String,
        extraction_key: u32,
    },
    BlockchainOpReturn {
        network: BlockchainNetwork,
        txid_prefix: String,
    },
    Webhook {
        url: String,
        secret: String,
    },
}

/// Passive mask receiver
pub struct PassiveMaskReceiver {
    config: PassiveDistributionConfig,

    /// Cached masks (mask_id -> mask_data)
    cached_masks: HashMap<String, MaskProfile>,

    /// Known mask IDs (to avoid duplicates)
    known_mask_ids: Vec<String>,
}

impl PassiveMaskReceiver {
    /// Create new passive receiver
    pub fn new(config: PassiveDistributionConfig) -> Self {
        Self {
            config,
            cached_masks: HashMap::new(),
            known_mask_ids: Vec::new(),
        }
    }

    /// Check for new masks (main polling function)
    pub async fn poll_masks(&mut self) -> Result<Vec<MaskProfile>> {
        if !self.config.enable {
            return Ok(vec![]);
        }

        let mut new_masks = Vec::new();

        // Check DNS TXT records
        for domain in &self.config.dns_domains {
            if let Ok(Some(mask)) = self.check_dns_txt(domain).await {
                if !self.known_mask_ids.contains(&mask.mask_id) {
                    info!("Discovered new mask via DNS: {}", mask.mask_id);
                    new_masks.push(mask);
                }
            }
        }

        // Check image LSB (if configured)
        for image_url in &self.config.image_urls {
            if let Ok(Some(mask)) = self.check_image_lsb(image_url).await {
                if !self.known_mask_ids.contains(&mask.mask_id) {
                    info!("Discovered new mask via image: {}", mask.mask_id);
                    new_masks.push(mask);
                }
            }
        }

        // Cache new masks
        for mask in &new_masks {
            self.known_mask_ids.push(mask.mask_id.clone());
            self.cached_masks.insert(mask.mask_id.clone(), mask.clone());
        }

        Ok(new_masks)
    }

    /// Check DNS TXT record for mask
    async fn check_dns_txt(&self, domain: &str) -> Result<Option<MaskProfile>> {
        // For MVP, return None
        // In production, use DNS-over-HTTPS API

        debug!("Checking DNS TXT for mask: {}", domain);

        // Example DNS TXT format:
        // mask1.aivpn.network. IN TXT "aivpn-mask-v1:<base64_encoded_mask>"

        Ok(None)
    }

    /// Check image LSB for steganographic mask
    async fn check_image_lsb(&self, url: &str) -> Result<Option<MaskProfile>> {
        // For MVP, return None
        // In production:
        // 1. Download image
        // 2. Extract LSB from pixels
        // 3. Decode 96 bytes (64 bytes mask + 32 bytes signature)
        // 4. Verify Ed25519 signature
        // 5. Deserialize MaskProfile

        debug!("Checking image LSB for mask: {}", url);

        Ok(None)
    }

    /// Decode mask from steganographic payload
    #[allow(dead_code)]
    fn decode_mask_payload(&self, payload: &[u8]) -> Result<Option<MaskProfile>> {
        use aivpn_common::error::Error;

        if payload.len() < 96 {
            return Err(Error::InvalidPacket("Payload too short"));
        }

        // Format: [64 bytes mask_latent_vector][32 bytes Ed25519 signature]
        let _mask_latent = &payload[0..64];
        let _signature = &payload[64..96];

        // In production:
        // 1. Verify signature against server's signing key
        // 2. Decode latent vector into MaskProfile

        debug!("Decoded {} bytes of mask payload", payload.len());

        Ok(None) // Placeholder
    }

    /// Get cached mask by ID
    pub fn get_cached_mask(&self, mask_id: &str) -> Option<&MaskProfile> {
        self.cached_masks.get(mask_id)
    }

    /// Get all cached masks
    pub fn get_all_masks(&self) -> Vec<&MaskProfile> {
        self.cached_masks.values().collect()
    }

    /// Clear cache (for security)
    pub fn clear_cache(&mut self) {
        self.cached_masks.clear();
    }
}

/// Steganographic encoder (for server-side mask publishing)
pub struct SteganographicEncoder {
    /// Server's Ed25519 signing key
    _signing_key: [u8; 64],
}

impl SteganographicEncoder {
    /// Create new encoder
    pub fn new(signing_key: [u8; 64]) -> Self {
        Self {
            _signing_key: signing_key,
        }
    }

    /// Encode mask for DNS TXT record
    pub fn encode_for_dns(&self, mask: &MaskProfile) -> Result<String> {
        // Serialize mask to bytes
        let mask_bytes = rmp_serde::to_vec(mask)?;

        // Create signature
        // In production: sign with Ed25519

        let encoded = base64::engine::general_purpose::STANDARD.encode(&mask_bytes);

        // Format: "aivpn-mask-v1:<base64>"
        Ok(format!("aivpn-mask-v1:{}", encoded))
    }

    /// Encode mask for image LSB steganography.
    pub fn encode_for_image(&self, _mask: &MaskProfile) -> Result<Vec<u8>> {
        unimplemented!("image LSB steganography encoding is not yet implemented")
    }

    /// Encode mask for blockchain OP_RETURN.
    pub fn encode_for_blockchain(&self, _mask: &MaskProfile) -> Result<Vec<u8>> {
        unimplemented!("blockchain OP_RETURN encoding is not yet implemented")
    }
}