Implement GuruRMM Phase 1: Real-time tunnel infrastructure

Complete bidirectional tunnel communication between server and agents,
enabling persistent secure channels for future command execution and
file operations. Agents transition from heartbeat mode to tunnel mode
on-demand while maintaining WebSocket connection.

Server Implementation:
- Database layer (db/tunnel.rs): Session CRUD, ownership validation,
  cleanup on disconnect (prevents orphaned sessions)
- API endpoints (api/tunnel.rs): POST /open, POST /close, GET /status
  with JWT auth, UUID validation, proper HTTP status codes
- Protocol extension (ws/mod.rs): TunnelOpen/Close/Data messages,
  agent response handlers (TunnelReady/Data/Error)
- Migration (006_tunnel_sessions.sql): tech_sessions table with
  partial unique constraint, foreign keys with CASCADE, audit table

Agent Implementation:
- State machine (tunnel/mod.rs): AgentMode (Heartbeat ↔ Tunnel),
  channel multiplexing, concurrent session prevention
- WebSocket handlers (transport/websocket.rs): Open/close tunnel,
  mode switching without dropping connection, cleanup on disconnect
- Protocol extension (transport/mod.rs): TunnelReady/Data/Error
  messages matching server definitions
- Unit tests: Lifecycle and channel management coverage

Key Features:
- Security: JWT auth, session ownership verification, SQL injection
  prevention, constraint-based duplicate session blocking
- Cleanup: Automatic session closure on agent disconnect (both sides),
  channel cleanup, graceful state transitions
- Error handling: Proper HTTP status codes (400/403/404/409/500),
  comprehensive Result types, detailed logging
- Extensibility: Channel types ready (Terminal/File/Registry/Service),
  TunnelDataPayload enum for Phase 2+ expansion

Phase 1 Scope (Implemented):
- Tunnel session lifecycle management
- Mode switching (heartbeat ↔ tunnel)
- Protocol message routing
- Database session tracking

Phase 2 Next Steps:
- Terminal command execution (tokio::process::Command)
- Client WebSocket connections for output streaming
- Command audit logging
- File transfer operations

Verification:
- Server compiles successfully (0 errors)
- Agent unit tests pass (tunnel lifecycle, channel management)
- Code review approved (protocol alignment verified)
- Database constraints enforce referential integrity
- Cleanup tested (session closure on disconnect)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

projects/msp-tools/guru-rmm/server/src/api/tunnel.rs

@@ -0,0 +1,231 @@
+//! Tunnel session management endpoints
+
+use axum::{
+    extract::{Path, State},
+    http::StatusCode,
+    Json,
+};
+use serde::{Deserialize, Serialize};
+use tracing::{error, warn};
+use uuid::Uuid;
+
+use crate::auth::AuthUser;
+use crate::db;
+use crate::ws::ServerMessage;
+use crate::AppState;
+
+#[derive(Debug, Deserialize)]
+pub struct OpenTunnelRequest {
+    pub agent_id: String,
+}
+
+#[derive(Debug, Serialize)]
+pub struct OpenTunnelResponse {
+    pub session_id: String,
+    pub status: String,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct CloseTunnelRequest {
+    pub session_id: String,
+}
+
+#[derive(Debug, Serialize)]
+pub struct CloseTunnelResponse {
+    pub status: String,
+}
+
+#[derive(Debug, Serialize)]
+pub struct TunnelStatusResponse {
+    pub session_id: String,
+    pub agent_id: String,
+    pub status: String,
+    pub opened_at: String,
+    pub last_activity: String,
+}
+
+/// POST /api/v1/tunnel/open
+/// Open a new tunnel session to an agent
+pub async fn open_tunnel(
+    State(state): State<AppState>,
+    user: AuthUser,
+    Json(req): Json<OpenTunnelRequest>,
+) -> Result<Json<OpenTunnelResponse>, (StatusCode, String)> {
+    // Parse agent_id
+    let agent_id = Uuid::parse_str(&req.agent_id)
+        .map_err(|_| (StatusCode::BAD_REQUEST, "Invalid agent_id format".to_string()))?;
+
+    // Check if agent exists and is online
+    let agent_connected = state.agents.read().await.is_connected(&agent_id);
+    if !agent_connected {
+        return Err((
+            StatusCode::NOT_FOUND,
+            "Agent not connected".to_string(),
+        ));
+    }
+
+    // Check for existing active session
+    let has_session = db::has_active_session(&state.db, user.user_id, agent_id)
+        .await
+        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
+
+    if has_session {
+        return Err((
+            StatusCode::CONFLICT,
+            "Active session already exists for this agent".to_string(),
+        ));
+    }
+
+    // Generate session ID
+    let session_id = Uuid::new_v4().to_string();
+
+    // Create session in database
+    let _session = db::create_tech_session(&state.db, &session_id, user.user_id, agent_id)
+        .await
+        .map_err(|e| {
+            // Handle unique constraint violation (PostgreSQL error code 23505)
+            if let Some(db_err) = e.as_database_error() {
+                if db_err.code().as_deref() == Some("23505") {
+                    return (
+                        StatusCode::CONFLICT,
+                        "Active session already exists for this agent".to_string(),
+                    );
+                }
+            }
+            error!("Failed to create tunnel session: {}", e);
+            (StatusCode::INTERNAL_SERVER_ERROR, e.to_string())
+        })?;
+
+    // Send TunnelOpen message to agent via WebSocket
+    let tunnel_open_msg = ServerMessage::TunnelOpen {
+        session_id: session_id.clone(),
+        tech_id: user.user_id,
+    };
+
+    let sent = state.agents.read().await.send_to(&agent_id, tunnel_open_msg).await;
+    if !sent {
+        // Clean up database session if send failed
+        if let Err(e) = db::close_tech_session(&state.db, &session_id).await {
+            error!("Failed to cleanup session {} after send failure: {}", session_id, e);
+        }
+        return Err((
+            StatusCode::INTERNAL_SERVER_ERROR,
+            "Failed to send tunnel open message to agent".to_string(),
+        ));
+    }
+
+    Ok(Json(OpenTunnelResponse {
+        session_id,
+        status: "active".to_string(),
+    }))
+}
+
+/// POST /api/v1/tunnel/close
+/// Close an existing tunnel session
+pub async fn close_tunnel(
+    State(state): State<AppState>,
+    user: AuthUser,
+    Json(req): Json<CloseTunnelRequest>,
+) -> Result<Json<CloseTunnelResponse>, (StatusCode, String)> {
+    // Validate session_id format
+    if Uuid::parse_str(&req.session_id).is_err() {
+        return Err((StatusCode::BAD_REQUEST, "Invalid session_id format".to_string()));
+    }
+
+    // Verify session ownership
+    let is_owner = db::verify_session_ownership(&state.db, &req.session_id, user.user_id)
+        .await
+        .map_err(|e| {
+            error!("Failed to verify session ownership: {}", e);
+            (StatusCode::INTERNAL_SERVER_ERROR, e.to_string())
+        })?;
+
+    if !is_owner {
+        return Err((
+            StatusCode::FORBIDDEN,
+            "Session not found or not owned by user".to_string(),
+        ));
+    }
+
+    // Get session to find agent_id
+    let session = db::get_tech_session(&state.db, &req.session_id)
+        .await
+        .map_err(|e| {
+            error!("Failed to get session: {}", e);
+            (StatusCode::INTERNAL_SERVER_ERROR, e.to_string())
+        })?
+        .ok_or((StatusCode::NOT_FOUND, "Session not found".to_string()))?;
+
+    // Send TunnelClose message to agent
+    let tunnel_close_msg = ServerMessage::TunnelClose {
+        session_id: req.session_id.clone(),
+    };
+
+    if !state.agents.read().await.send_to(&session.agent_id, tunnel_close_msg).await {
+        warn!(
+            "Failed to send TunnelClose message to agent {} for session {}",
+            session.agent_id, req.session_id
+        );
+    }
+
+    // Close session in database
+    match db::close_tech_session(&state.db, &req.session_id).await {
+        Ok(rows) if rows == 0 => {
+            warn!("No rows updated when closing session {}", req.session_id);
+        }
+        Ok(_) => {}
+        Err(e) => {
+            error!("Failed to close session in database: {}", e);
+            return Err((StatusCode::INTERNAL_SERVER_ERROR, e.to_string()));
+        }
+    }
+
+    Ok(Json(CloseTunnelResponse {
+        status: "closed".to_string(),
+    }))
+}
+
+/// GET /api/v1/tunnel/status/:session_id
+/// Get tunnel session status
+pub async fn get_tunnel_status(
+    State(state): State<AppState>,
+    user: AuthUser,
+    Path(session_id): Path<String>,
+) -> Result<Json<TunnelStatusResponse>, (StatusCode, String)> {
+    // Validate session_id format
+    if Uuid::parse_str(&session_id).is_err() {
+        return Err((StatusCode::BAD_REQUEST, "Invalid session_id format".to_string()));
+    }
+
+    // Verify session ownership
+    let is_owner = db::verify_session_ownership(&state.db, &session_id, user.user_id)
+        .await
+        .map_err(|e| {
+            error!("Failed to verify session ownership: {}", e);
+            (StatusCode::INTERNAL_SERVER_ERROR, e.to_string())
+        })?;
+
+    if !is_owner {
+        return Err((
+            StatusCode::FORBIDDEN,
+            "Session not found or not owned by user".to_string(),
+        ));
+    }
+
+    // Get session
+    let session = db::get_tech_session(&state.db, &session_id)
+        .await
+        .map_err(|e| {
+            error!("Failed to get session: {}", e);
+            (StatusCode::INTERNAL_SERVER_ERROR, e.to_string())
+        })?
+        .ok_or((StatusCode::NOT_FOUND, "Session not found".to_string()))?;
+
+    Ok(Json(TunnelStatusResponse {
+        session_id: session.session_id,
+        agent_id: session.agent_id.to_string(),
+        status: session.status,
+        opened_at: session.opened_at.to_rfc3339(),
+        last_activity: session.last_activity.to_rfc3339(),
+    }))
+}