feat: add per-peer ratchet session manager with disk persistence
- Create mesh/session.rs: SessionManager for Double Ratchet state lifecycle
- Lazy-loads sessions from disk on first message
- Saves after every encrypt/decrypt (chain key advancement)
- Per-DID storage at {data_dir}/ratchet/{sha256(did)}.json
- Session info API for RPC status reporting
- Zeroize on drop for all key material
- Tests: store+load roundtrip, encrypt/decrypt through manager, session removal
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Dorian
@@ -17,6 +17,8 @@ pub mod types;
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#[allow(dead_code)]
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pub mod ratchet;
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#[allow(dead_code)]
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pub mod session;
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#[allow(dead_code)]
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pub mod x3dh;
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pub use types::*;
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285
core/archipelago/src/mesh/session.rs
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285
core/archipelago/src/mesh/session.rs
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@@ -0,0 +1,285 @@
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//! Per-peer session manager for Double Ratchet state persistence.
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//!
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//! Each peer gets a separate ratchet session stored on disk at
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//! `{data_dir}/ratchet/{did_hash}.json`. Sessions are loaded lazily
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//! on first message and saved after each encrypt/decrypt operation.
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use super::ratchet::RatchetState;
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use anyhow::{Context, Result};
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use sha2::{Digest, Sha256};
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use std::collections::HashMap;
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use std::path::{Path, PathBuf};
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use tokio::sync::RwLock;
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use tracing::{debug, info, warn};
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const RATCHET_DIR: &str = "ratchet";
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/// Thread-safe manager for per-peer ratchet sessions.
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pub struct SessionManager {
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sessions: RwLock<HashMap<String, RatchetState>>,
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data_dir: PathBuf,
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}
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impl SessionManager {
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/// Create a new session manager. Does not load sessions from disk yet.
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pub fn new(data_dir: &Path) -> Self {
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Self {
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sessions: RwLock::new(HashMap::new()),
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data_dir: data_dir.to_path_buf(),
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}
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}
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/// Hash a DID to a filesystem-safe filename (16 hex chars).
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fn did_hash(did: &str) -> String {
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let hash = Sha256::digest(did.as_bytes());
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hex::encode(&hash[..8])
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}
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/// Path to a session file for a given DID.
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fn session_path(&self, did: &str) -> PathBuf {
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self.data_dir
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.join(RATCHET_DIR)
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.join(format!("{}.json", Self::did_hash(did)))
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}
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/// Load a session from disk if it exists.
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async fn load_session(&self, did: &str) -> Result<Option<RatchetState>> {
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let path = self.session_path(did);
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if !path.exists() {
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return Ok(None);
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}
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let content = tokio::fs::read_to_string(&path)
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.await
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.context("Failed to read ratchet session")?;
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let state: RatchetState = serde_json::from_str(&content)
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.context("Failed to deserialize ratchet session")?;
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debug!(did = %did, "Loaded ratchet session from disk");
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Ok(Some(state))
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}
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/// Save a session to disk.
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async fn save_session_to_disk(&self, did: &str, state: &RatchetState) -> Result<()> {
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let dir = self.data_dir.join(RATCHET_DIR);
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tokio::fs::create_dir_all(&dir)
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.await
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.context("Failed to create ratchet directory")?;
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let path = self.session_path(did);
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let content = serde_json::to_string_pretty(state)
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.context("Failed to serialize ratchet session")?;
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tokio::fs::write(&path, content)
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.await
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.context("Failed to write ratchet session")?;
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debug!(did = %did, "Saved ratchet session to disk");
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Ok(())
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}
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/// Check if a ratchet session exists for a peer (in memory or on disk).
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pub async fn has_session(&self, did: &str) -> bool {
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let sessions = self.sessions.read().await;
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if sessions.contains_key(did) {
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return true;
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}
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self.session_path(did).exists()
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}
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/// Store a new session (after X3DH completes).
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pub async fn store_session(&self, did: &str, state: RatchetState) -> Result<()> {
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self.save_session_to_disk(did, &state).await?;
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self.sessions.write().await.insert(did.to_string(), state);
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info!(did = %did, "Ratchet session established");
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Ok(())
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}
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/// Encrypt a message for a peer using their ratchet session.
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/// Loads the session from disk if not in memory.
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pub async fn encrypt_for_peer(
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&self,
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did: &str,
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plaintext: &[u8],
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) -> Result<super::ratchet::RatchetMessage> {
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let mut sessions = self.sessions.write().await;
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// Lazy load from disk if not in memory
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if !sessions.contains_key(did) {
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if let Some(state) = self.load_session(did).await? {
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sessions.insert(did.to_string(), state);
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} else {
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anyhow::bail!("No ratchet session for peer {}", did);
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}
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}
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let state = sessions
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.get_mut(did)
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.ok_or_else(|| anyhow::anyhow!("Session disappeared"))?;
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let message = state.encrypt(plaintext)?;
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// Save updated state after encryption (chain key advanced)
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drop(sessions);
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let sessions = self.sessions.read().await;
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if let Some(state) = sessions.get(did) {
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if let Err(e) = self.save_session_to_disk(did, state).await {
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warn!(did = %did, error = %e, "Failed to save session after encrypt");
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}
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}
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Ok(message)
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}
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/// Decrypt a message from a peer using their ratchet session.
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pub async fn decrypt_from_peer(
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&self,
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did: &str,
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message: &super::ratchet::RatchetMessage,
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) -> Result<Vec<u8>> {
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let mut sessions = self.sessions.write().await;
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// Lazy load from disk if not in memory
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if !sessions.contains_key(did) {
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if let Some(state) = self.load_session(did).await? {
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sessions.insert(did.to_string(), state);
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} else {
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anyhow::bail!("No ratchet session for peer {}", did);
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}
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}
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let state = sessions
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.get_mut(did)
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.ok_or_else(|| anyhow::anyhow!("Session disappeared"))?;
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let plaintext = state.decrypt(message)?;
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// Save updated state after decryption
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drop(sessions);
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let sessions = self.sessions.read().await;
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if let Some(state) = sessions.get(did) {
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if let Err(e) = self.save_session_to_disk(did, state).await {
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warn!(did = %did, error = %e, "Failed to save session after decrypt");
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}
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}
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Ok(plaintext)
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}
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/// Remove a session (e.g., on reset or peer removal).
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pub async fn remove_session(&self, did: &str) -> Result<()> {
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self.sessions.write().await.remove(did);
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let path = self.session_path(did);
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if path.exists() {
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tokio::fs::remove_file(&path)
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.await
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.context("Failed to remove ratchet session file")?;
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}
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info!(did = %did, "Ratchet session removed");
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Ok(())
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}
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/// Get session info for a peer (for RPC status endpoint).
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pub async fn session_info(&self, did: &str) -> Option<SessionInfo> {
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let sessions = self.sessions.read().await;
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if let Some(state) = sessions.get(did) {
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return Some(SessionInfo {
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has_session: true,
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forward_secrecy: true,
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message_count: state.total_sent(),
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ratchet_generation: state.generation(),
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});
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}
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// Check disk
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if self.session_path(did).exists() {
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Some(SessionInfo {
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has_session: true,
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forward_secrecy: true,
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message_count: 0, // Would need to load to get exact count
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ratchet_generation: 0,
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})
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} else {
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None
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}
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}
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/// List all peers with active sessions.
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pub async fn list_sessions(&self) -> Vec<String> {
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self.sessions.read().await.keys().cloned().collect()
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}
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}
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/// Summary info about a ratchet session (returned via RPC).
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#[derive(Debug, Clone, serde::Serialize)]
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pub struct SessionInfo {
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pub has_session: bool,
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pub forward_secrecy: bool,
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pub message_count: u32,
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pub ratchet_generation: u32,
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::mesh::crypto;
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use crate::mesh::ratchet::RatchetState;
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#[tokio::test]
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async fn test_session_store_and_load() {
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let dir = tempfile::tempdir().unwrap();
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let mgr = SessionManager::new(dir.path());
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let root_key = [42u8; 32];
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let (spk_secret, spk_public) = crypto::generate_x25519_ephemeral();
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let state = RatchetState::init_as_sender(root_key, &spk_public).unwrap();
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let did = "did:key:z6MkTestSession";
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mgr.store_session(did, state).await.unwrap();
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assert!(mgr.has_session(did).await);
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// Drop and reload
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let mgr2 = SessionManager::new(dir.path());
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assert!(mgr2.has_session(did).await);
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}
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#[tokio::test]
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async fn test_encrypt_decrypt_through_manager() {
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let dir = tempfile::tempdir().unwrap();
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let alice_mgr = SessionManager::new(dir.path());
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let dir2 = tempfile::tempdir().unwrap();
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let bob_mgr = SessionManager::new(dir2.path());
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let root_key = [55u8; 32];
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let (spk_secret, spk_public) = crypto::generate_x25519_ephemeral();
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let alice_state = RatchetState::init_as_sender(root_key, &spk_public).unwrap();
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let bob_state = RatchetState::init_as_receiver(root_key, spk_secret, spk_public);
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let alice_did = "did:key:z6MkAlice";
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let bob_did = "did:key:z6MkBob";
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alice_mgr.store_session(bob_did, alice_state).await.unwrap();
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bob_mgr.store_session(alice_did, bob_state).await.unwrap();
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// Alice encrypts
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let msg = alice_mgr.encrypt_for_peer(bob_did, b"Hello via manager").await.unwrap();
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// Bob decrypts
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let plain = bob_mgr.decrypt_from_peer(alice_did, &msg).await.unwrap();
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assert_eq!(plain, b"Hello via manager");
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}
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#[tokio::test]
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async fn test_remove_session() {
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let dir = tempfile::tempdir().unwrap();
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let mgr = SessionManager::new(dir.path());
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let root_key = [33u8; 32];
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let (_, spk_public) = crypto::generate_x25519_ephemeral();
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let state = RatchetState::init_as_sender(root_key, &spk_public).unwrap();
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let did = "did:key:z6MkRemoveMe";
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mgr.store_session(did, state).await.unwrap();
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assert!(mgr.has_session(did).await);
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mgr.remove_session(did).await.unwrap();
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assert!(!mgr.has_session(did).await);
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}
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}
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