feat: add OpenConsoleProxy service facade

server/internal/services/consoleproxy.go

@@ -0,0 +1,122 @@
+package services
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"net"
+	"os"
+
+	"gitea.hostxtra.co.uk/mrhid6/vantage/server/internal/grpc/pb"
+	"gitea.hostxtra.co.uk/mrhid6/vantage/server/internal/proxy"
+)
+
+// ErrAgentOffline means the console cannot be opened because the target's agent
+// is not on the command stream. Every console session is relayed by the agent,
+// so this is fatal rather than a degraded mode.
+var ErrAgentOffline = errors.New("agent is not connected")
+
+// ConsoleProxy is a pending relay: a bound listener guacd can dial and a
+// dispatched command telling the agent to meet it.
+type ConsoleProxy struct {
+	ProxyID string
+	Host    string
+	Port    int
+
+	session *proxy.Session
+}
+
+func (c *ConsoleProxy) Close() {
+	proxy.Default.Remove(c.ProxyID)
+	c.session.Close("")
+}
+
+func (c *ConsoleProxy) Reason() string { return c.session.Reason() }
+
+func proxyListenHost() string {
+	if v := os.Getenv("PROXY_LISTEN_HOST"); v != "" {
+		return v
+	}
+	return "0.0.0.0"
+}
+
+func proxyAdvertiseHost() string {
+	if v := os.Getenv("PROXY_ADVERTISE_HOST"); v != "" {
+		return v
+	}
+	return "server"
+}
+
+func guacdAddr() string {
+	if v := os.Getenv("GUACD_ADDR"); v != "" {
+		return v
+	}
+	return "guacd:4822"
+}
+
+// guacdHosts resolves guacd's address to the IPs allowed to claim a relay
+// listener. An unresolvable host yields an empty set, which allows any source:
+// refusing everything would take the console down entirely, so the narrower
+// protections (ephemeral port, 10s window, single accept) carry it instead.
+func guacdHosts(addr string) []string {
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		host = addr
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		return []string{ip.String()}
+	}
+	ips, err := net.LookupHost(host)
+	if err != nil {
+		log.Printf("proxy: cannot resolve guacd host %q, allowing any relay source: %v", host, err)
+		return nil
+	}
+	return ips
+}
+
+// DispatchOpenProxy tells the agent to dial its own loopback on port and relay
+// it back under proxyID.
+func DispatchOpenProxy(serverID, proxyID string, port uint32) error {
+	return Dispatcher.dispatch(serverID, &pb.ServerCommand{
+		CommandId: proxyID,
+		OpenProxy: &pb.OpenProxyCmd{ProxyId: proxyID, Port: port},
+	})
+}
+
+// OpenConsoleProxy binds a relay listener, registers it, and asks the agent to
+// connect. The caller must Close the result.
+func OpenConsoleProxy(instanceID, serverID string, targetPort int) (*ConsoleProxy, error) {
+	if !Dispatcher.IsConnected(serverID) {
+		return nil, ErrAgentOffline
+	}
+
+	proxyID, err := proxy.NewID()
+	if err != nil {
+		return nil, fmt.Errorf("generate proxy id: %w", err)
+	}
+
+	sess, err := proxy.NewSession(proxyListenHost(), guacdHosts(guacdAddr()))
+	if err != nil {
+		return nil, err
+	}
+
+	proxy.Default.Add(&proxy.Entry{
+		ProxyID:    proxyID,
+		InstanceID: instanceID,
+		ServerID:   serverID,
+		Session:    sess,
+	})
+
+	if err := DispatchOpenProxy(serverID, proxyID, uint32(targetPort)); err != nil {
+		proxy.Default.Remove(proxyID)
+		sess.Close("dispatch_failed")
+		return nil, err
+	}
+
+	return &ConsoleProxy{
+		ProxyID: proxyID,
+		Host:    proxyAdvertiseHost(),
+		Port:    sess.Port(),
+		session: sess,
+	}, nil
+}