fix(web): trust service CA and send a known target for TTS

soundtouch-web's "Speak" feature proxies to the AfterTouch service's
/setup/tts/speak endpoint. Two issues blocked it end to end.

1. TLS: the proxy used http.DefaultClient, which trusts only system
   roots, so the HTTPS call to a service using its own self-signed CA
   failed with "x509: certificate signed by unknown authority". Add a
   --service-ca flag (SERVICE_CA env) that loads the CA PEM, appends it
   to the system pool, and uses a custom client for the TTS call.

2. Target: soundtouch-web sent device.Client.Host() (a full base URL
   like http://ip:8090), but the service's SSRF guard exact-matches the
   target against bare datastore IPs, returning "host ... is not a known
   device". Prefer the device ID (the canonical key) and send a bare-IP
   host fallback. Also normalize the incoming host in resolveTTSHost so a
   URL/host:port form still resolves; it still only ever returns a
   datastore IP, so the SSRF guarantee is unchanged.

Adds unit tests for the CA client builder, hostOnly, and resolveTTSHost
(including the preserved unknown-host/device rejections). Documents
--service-ca in the soundtouch-web README and TROUBLESHOOTING guide.
Wires SERVICE_URL and SERVICE_CA (empty defaults) into the Raspberry Pi
install-web.sh env file and documents them in the Pi guide.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

pkg/service/handlers/handlers_tts.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"net"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -152,9 +153,15 @@ func (s *Server) HandleSpeakerAuth(w http.ResponseWriter, _ *http.Request) {
 // baseURL -> the outbound request). Match by DeviceID, or by Host equal to a
 // known device's IP; either way the returned string is the datastore's
 // IPAddress, not the caller-supplied value.
+//
+// The incoming Host is normalized to a bare host (scheme and port stripped)
+// before the match so callers that pass a base URL (e.g. "http://ip:8090",
+// which is what a client's Host() returns) still resolve. This only makes the
+// needle comparable to the datastore's bare IPs; the result is still always a
+// datastore IP, so the SSRF guarantee is unchanged.
 func (s *Server) resolveTTSHost(req ttsSpeakRequest) (string, error) {
 	deviceID := strings.TrimSpace(req.DeviceID)
-	host := strings.TrimSpace(req.Host)
+	host := ttsHostOnly(strings.TrimSpace(req.Host))
 
 	if deviceID == "" && host == "" {
 		return "", fmt.Errorf("either deviceId or host is required")
@@ -183,6 +190,25 @@ func (s *Server) resolveTTSHost(req ttsSpeakRequest) (string, error) {
 	return "", fmt.Errorf("host %s is not a known device", host)
 }
 
+// ttsHostOnly reduces a base URL or host:port to a bare host so it can be
+// compared against the datastore's bare IPs. Inputs that are already bare are
+// returned unchanged. The empty string maps to the empty string.
+func ttsHostOnly(raw string) string {
+	if raw == "" {
+		return ""
+	}
+
+	if u, err := url.Parse(raw); err == nil && u.Host != "" {
+		return u.Hostname()
+	}
+
+	if host, _, err := net.SplitHostPort(raw); err == nil {
+		return host
+	}
+
+	return raw
+}
+
 // HandleTTSMedia serves a synthesized clip by id for the speaker to fetch.
 func (s *Server) HandleTTSMedia(w http.ResponseWriter, r *http.Request) {
 	svc := s.ttsSvc()

pkg/service/handlers/handlers_tts_test.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/gesellix/bose-soundtouch/pkg/models"
 	"github.com/gesellix/bose-soundtouch/pkg/service/datastore"
 	"github.com/gesellix/bose-soundtouch/pkg/service/tts"
 	"github.com/go-chi/chi/v5"
@@ -181,3 +182,61 @@ func TestHandleTTSSpeakValidation(t *testing.T) {
 		})
 	}
 }
+
+// TestResolveTTSHost covers the SSRF guard plus the host-normalization that
+// lets a base URL (what a client's Host() returns, e.g. soundtouch-web sends
+// "http://ip:8090") resolve to a known device. The result is always the
+// datastore's bare IP, never the caller's value.
+func TestResolveTTSHost(t *testing.T) {
+	ds := datastore.NewDataStore(t.TempDir())
+	if err := ds.Initialize(); err != nil {
+		t.Fatalf("Initialize: %v", err)
+	}
+
+	if err := ds.SaveDeviceInfo("1000001", "DEVICEID01", &models.ServiceDeviceInfo{
+		DeviceID:  "DEVICEID01",
+		AccountID: "1000001",
+		IPAddress: "192.0.2.10",
+	}); err != nil {
+		t.Fatalf("SaveDeviceInfo: %v", err)
+	}
+
+	server := NewServer(ds, nil, "http://localhost:8001", false, false, false)
+
+	cases := []struct {
+		name    string
+		req     ttsSpeakRequest
+		want    string
+		wantErr bool
+	}{
+		{"bare ip", ttsSpeakRequest{Host: "192.0.2.10"}, "192.0.2.10", false},
+		{"base url", ttsSpeakRequest{Host: "http://192.0.2.10:8090"}, "192.0.2.10", false},
+		{"host:port", ttsSpeakRequest{Host: "192.0.2.10:8090"}, "192.0.2.10", false},
+		{"by device id", ttsSpeakRequest{DeviceID: "DEVICEID01"}, "192.0.2.10", false},
+		// SSRF guard intact: unknown targets are rejected even in URL form.
+		{"unknown host url", ttsSpeakRequest{Host: "http://203.0.113.99:8090"}, "", true},
+		{"unknown device", ttsSpeakRequest{DeviceID: "NOPE"}, "", true},
+		{"no target", ttsSpeakRequest{}, "", true},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := server.resolveTTSHost(tc.req)
+			if tc.wantErr {
+				if err == nil {
+					t.Fatalf("expected error, got %q", got)
+				}
+
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			if got != tc.want {
+				t.Fatalf("got %q, want %q", got, tc.want)
+			}
+		})
+	}
+}

pkg/service/soundtouchweb/handler.go

@@ -42,9 +42,26 @@ type WebApp struct {
 	RepoURL    string
 	ServiceURL string
 
+	// ServiceClient is used for server-side calls to the AfterTouch service
+	// (currently the TTS proxy). When nil, serviceHTTPClient falls back to
+	// http.DefaultClient. Set it via NewServiceHTTPClient to trust the
+	// service's self-signed CA.
+	ServiceClient *http.Client
+
 	discoveryStatus atomic.Value // stores *webtypes.DiscoveryStatus
 }
 
+// serviceHTTPClient returns the client used for outbound calls to the
+// AfterTouch service, falling back to http.DefaultClient when no CA-trusting
+// client was configured.
+func (app *WebApp) serviceHTTPClient() *http.Client {
+	if app.ServiceClient != nil {
+		return app.ServiceClient
+	}
+
+	return http.DefaultClient
+}
+
 // DeviceEntry pairs a device id with its connection. Used by
 // DeviceSnapshot so callers can iterate without holding the lock.
 type DeviceEntry struct {

pkg/service/soundtouchweb/handlers_tts.go

@@ -5,12 +5,36 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
+	"net/url"
 	"strings"
 
 	"github.com/go-chi/chi/v5"
 )
 
+// hostOnly reduces a base URL or host:port to a bare host (IP or hostname).
+// device.Client.Host() returns a full base URL like "http://192.168.0.2:8090",
+// but the AfterTouch service matches the TTS target against bare datastore IPs,
+// so we strip the scheme and port before sending it. Inputs that are already
+// bare ("192.168.0.2") are returned unchanged.
+func hostOnly(raw string) string {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return ""
+	}
+
+	if u, err := url.Parse(raw); err == nil && u.Host != "" {
+		return u.Hostname()
+	}
+
+	if host, _, err := net.SplitHostPort(raw); err == nil {
+		return host
+	}
+
+	return raw
+}
+
 // HandleAPISpeakText synthesizes and plays text on a device. The Web UI talks
 // to speakers directly for most controls, but TTS synthesis (Google Cloud) and
 // the Bose app_key live in the AfterTouch service, so this proxies to the
@@ -60,10 +84,22 @@ func (app *WebApp) HandleAPISpeakText(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Identify the target speaker for the service. Prefer the DeviceID (the
+	// canonical, unambiguous key the service matches in its datastore). Also
+	// send a bare-IP host as a fallback: device.Client.Host() is a full base
+	// URL (http://ip:8090), which the service's exact-match SSRF guard
+	// (resolveTTSHost) would reject, so strip it down to host-only.
 	payload := map[string]interface{}{
-		"host": device.Client.Host(),
 		"text": req.Text,
 	}
+	if device.DeviceInfo != nil && device.DeviceInfo.DeviceID != "" {
+		payload["deviceId"] = device.DeviceInfo.DeviceID
+	}
+
+	if h := hostOnly(device.Client.Host()); h != "" {
+		payload["host"] = h
+	}
+
 	if req.Language != "" {
 		payload["language"] = req.Language
 	}
@@ -90,7 +126,7 @@ func (app *WebApp) HandleAPISpeakText(w http.ResponseWriter, r *http.Request) {
 
 	upstream.Header.Set("Content-Type", "application/json")
 
-	resp, err := http.DefaultClient.Do(upstream)
+	resp, err := app.serviceHTTPClient().Do(upstream)
 	if err != nil {
 		app.sendError(w, fmt.Sprintf("TTS service request failed: %v", err), http.StatusBadGateway)
 		return

pkg/service/soundtouchweb/service_client.go

@@ -0,0 +1,49 @@
+package soundtouchweb
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+)
+
+// NewServiceHTTPClient builds an *http.Client that trusts the AfterTouch
+// service's CA certificate (PEM at caPath) in addition to the system trust
+// store. soundtouch-web uses it for the only server-side call it makes to the
+// service (the TTS proxy in handlers_tts.go): the service serves a self-signed
+// certificate signed by its own "AfterTouch Local Root CA", which isn't in any
+// system trust store, so http.DefaultClient would reject it with
+// "x509: certificate signed by unknown authority".
+//
+// The CA is appended to a copy of the system pool (not a fresh empty one) so a
+// deployment whose service URL happens to use a publicly trusted certificate
+// keeps working.
+func NewServiceHTTPClient(caPath string) (*http.Client, error) {
+	pem, err := os.ReadFile(caPath)
+	if err != nil {
+		return nil, fmt.Errorf("read CA: %w", err)
+	}
+
+	pool, err := x509.SystemCertPool()
+	if err != nil || pool == nil {
+		pool = x509.NewCertPool()
+	}
+
+	if !pool.AppendCertsFromPEM(pem) {
+		return nil, fmt.Errorf("no valid certificate found in %s", caPath)
+	}
+
+	return &http.Client{
+		// TTS round-trips through Google Cloud synthesis and speaker playback,
+		// so allow more than the bare connect time.
+		Timeout: 30 * time.Second,
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{
+				RootCAs:    pool,
+				MinVersion: tls.VersionTLS12,
+			},
+		},
+	}, nil
+}

pkg/service/soundtouchweb/service_client_test.go

@@ -0,0 +1,100 @@
+package soundtouchweb
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"net/http"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+// writeTestCA generates a throwaway self-signed CA and returns its PEM path.
+func writeTestCA(t *testing.T) string {
+	t.Helper()
+
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("generate key: %v", err)
+	}
+
+	tmpl := &x509.Certificate{
+		SerialNumber:          big.NewInt(1),
+		Subject:               pkix.Name{CommonName: "Test CA"},
+		NotBefore:             time.Now().Add(-time.Hour),
+		NotAfter:              time.Now().Add(time.Hour),
+		IsCA:                  true,
+		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageDigitalSignature,
+		BasicConstraintsValid: true,
+	}
+
+	der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &key.PublicKey, key)
+	if err != nil {
+		t.Fatalf("create cert: %v", err)
+	}
+
+	path := filepath.Join(t.TempDir(), "ca.crt")
+	if err := os.WriteFile(path, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: der}), 0o600); err != nil {
+		t.Fatalf("write ca: %v", err)
+	}
+
+	return path
+}
+
+func TestNewServiceHTTPClientValidCA(t *testing.T) {
+	client, err := NewServiceHTTPClient(writeTestCA(t))
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	tr, ok := client.Transport.(*http.Transport)
+	if !ok {
+		t.Fatalf("transport type = %T, want *http.Transport", client.Transport)
+	}
+
+	if tr.TLSClientConfig == nil || tr.TLSClientConfig.RootCAs == nil {
+		t.Fatal("expected a non-nil RootCAs pool")
+	}
+
+	if client.Timeout == 0 {
+		t.Fatal("expected a non-zero timeout")
+	}
+}
+
+func TestNewServiceHTTPClientMissingFile(t *testing.T) {
+	if _, err := NewServiceHTTPClient(filepath.Join(t.TempDir(), "absent.crt")); err == nil {
+		t.Fatal("expected an error for a missing file")
+	}
+}
+
+func TestNewServiceHTTPClientNoCertInFile(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "junk.crt")
+	if err := os.WriteFile(path, []byte("not a pem certificate"), 0o600); err != nil {
+		t.Fatalf("write junk: %v", err)
+	}
+
+	if _, err := NewServiceHTTPClient(path); err == nil {
+		t.Fatal("expected an error for a file with no certificate")
+	}
+}
+
+func TestHostOnly(t *testing.T) {
+	cases := map[string]string{
+		"http://192.168.178.35:8090": "192.168.178.35",
+		"https://soundtouch.local":   "soundtouch.local",
+		"192.168.178.35:8090":        "192.168.178.35",
+		"192.168.178.35":             "192.168.178.35",
+		"":                           "",
+	}
+
+	for in, want := range cases {
+		if got := hostOnly(in); got != want {
+			t.Errorf("hostOnly(%q) = %q, want %q", in, got, want)
+		}
+	}
+}