feat: route every console session through the agent relay

server/internal/api/console.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"errors"
 	"net"
 	"net/http"
 	"os"
@@ -33,6 +34,15 @@ func consoleConnect(c *gin.Context) {
 		return
 	}
 
+	if srv.Status != "active" {
+		c.JSON(http.StatusConflict, gin.H{
+			"error": "agent_offline",
+			"message": "The agent on this server is not connected. " +
+				"Console sessions are relayed by the agent, so it must be online.",
+		})
+		return
+	}
+
 	sess, err := services.CreateConsoleSession(auth.InstanceID(c), body.ServerID, body.Protocol, body.KeyID, actorFromCtx(c), c.ClientIP())
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
@@ -59,7 +69,7 @@ func consoleConnect(c *gin.Context) {
 	}
 
 	services.LogEvent(auth.InstanceID(c), "console.opened", actorFromCtx(c), srv.ServerID, "",
-		"console session opened ("+body.Protocol+")")
+		"console session opened ("+body.Protocol+", agent-relayed)")
 
 	c.JSON(http.StatusOK, gin.H{
 		"session_id": sess.SessionID,
@@ -124,7 +134,25 @@ func consoleTunnel(c *gin.Context) {
 			return
 		}
 	}
-	gp, err := services.BuildGuacParams(srv, sess.Protocol, sess.SSHUsername, privKey, passphrase, rdpUser, rdpPass)
+	targetPort, err := services.TargetPort(srv, sess.Protocol)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	relay, err := services.OpenConsoleProxy(instanceID, srv.ServerID, targetPort)
+	if err != nil {
+		if errors.Is(err, services.ErrAgentOffline) {
+			c.JSON(http.StatusConflict, gin.H{"error": "agent_offline"})
+			return
+		}
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "could not open relay"})
+		return
+	}
+	defer relay.Close()
+
+	gp, err := services.BuildGuacParams(sess.Protocol, sess.SSHUsername, privKey, passphrase,
+		rdpUser, rdpPass, relay.Host, relay.Port)
 	if err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
 		return
@@ -162,6 +190,11 @@ func consoleTunnel(c *gin.Context) {
 
 	wsServer := guac.NewWebsocketServer(connect)
 	wsServer.OnDisconnect = func(id string, r *http.Request, t guac.Tunnel) {
+		if reason := relay.Reason(); reason != "" {
+			services.LogEvent(instanceID, "console.proxy_failed", actorFromCtx(c), srv.ServerID, "",
+				"console relay failed: "+reason)
+		}
+		relay.Close()
 		_ = services.EndConsoleSession(instanceID, sessionID)
 	}
 	wsServer.ServeHTTP(c.Writer, c.Request)

server/internal/services/console.go

@@ -77,20 +77,37 @@ type GuacParams struct {
 	Params   map[string]string
 }
 
-func portOr(v, def int) string {
+func portOr(v, def int) int {
 	if v == 0 {
-		v = def
+		return def
 	}
-	return strconv.Itoa(v)
+	return v
 }
 
-func BuildGuacParams(srv *models.Server, protocol, sshUser, privateKey, passphrase, rdpUser, rdpPass string) (*GuacParams, error) {
-	host := srv.IPAddress
+// TargetPort is the port on the managed server that the agent will dial on its
+// own loopback address.
+func TargetPort(srv *models.Server, protocol string) (int, error) {
+	switch protocol {
+	case "ssh":
+		return portOr(srv.SSHPort, 22), nil
+	case "rdp":
+		return portOr(srv.RDPPort, 3389), nil
+	case "vnc":
+		return 5900, nil
+	default:
+		return 0, fmt.Errorf("unsupported protocol %q", protocol)
+	}
+}
+
+// BuildGuacParams points guacd at the relay listener, never at the managed
+// server: on a cloud deployment the server's address is not routable from here.
+func BuildGuacParams(protocol, sshUser, privateKey, passphrase, rdpUser, rdpPass, relayHost string, relayPort int) (*GuacParams, error) {
+	port := strconv.Itoa(relayPort)
 	switch protocol {
 	case "ssh":
 		p := map[string]string{
-			"hostname": host,
-			"port":     portOr(srv.SSHPort, 22),
+			"hostname": relayHost,
+			"port":     port,
 		}
 		if sshUser == "" {
 			sshUser = "root"
@@ -105,8 +122,8 @@ func BuildGuacParams(srv *models.Server, protocol, sshUser, privateKey, passphra
 		return &GuacParams{Protocol: "ssh", Params: p}, nil
 	case "rdp":
 		return &GuacParams{Protocol: "rdp", Params: map[string]string{
-			"hostname":    host,
-			"port":        portOr(srv.RDPPort, 3389),
+			"hostname":    relayHost,
+			"port":        port,
 			"username":    rdpUser,
 			"password":    rdpPass,
 			"security":    "any",
@@ -114,8 +131,8 @@ func BuildGuacParams(srv *models.Server, protocol, sshUser, privateKey, passphra
 		}}, nil
 	case "vnc":
 		return &GuacParams{Protocol: "vnc", Params: map[string]string{
-			"hostname": host,
-			"port":     "5900",
+			"hostname": relayHost,
+			"port":     port,
 			"password": rdpPass,
 		}}, nil
 	default: