0.2.65 - End Credits wiring / Gateway: 0.1.45 - Credits

server/README.md

@@ -331,15 +331,27 @@ leaves the server. `MEMBY_RADARR_TTL` controls the shared calendar cache lifetim
 `https://mserver.sublogue.com/admin/` — a self-contained console for library imports,
 maintenance, engagement and journeys. Set `MEMBY_ADMIN_TOKEN` to enable it; unset, every
 `/admin` route 404s so it cannot be left exposed by accident. The page first uses the same
-discreet Emby login gate as the private installer. After successful verification it
+discreet Emby login gate as the private installer, and additionally requires that the
+account **administers Emby** — `Policy.IsAdministrator`, which Emby returns with the
+authentication itself, so the check costs no extra request. Knowing a household password
+is not the qualification for reaching the console: `/install` is public by design, and any
+viewer may sign in there. A refusal is worded exactly as a wrong password, so nothing
+discloses that the account was right but the person is not an administrator; the operator
+sees the reason in the log. An Emby that returns no policy at all is asked directly rather
+than read as a refusal, and one that will not answer refuses the sign-in — silence is
+never taken as permission.
+
+The two sign-ins issue the *same* cookie, so they are separated by being signed with their
+own purpose: an installer session cannot satisfy the console's gate, while an
+administrator's session satisfies the installer's. After successful verification the page
 establishes the HttpOnly admin cookie, but browser API requests require both that cookie
-and the current 12-hour Emby-verified session. The old admin cookie therefore cannot
+and the current 90-day Emby-verified admin session. The old admin cookie therefore cannot
 bypass the gate after the browser session expires. Scripts may continue to use
 `Authorization: Bearer <MEMBY_ADMIN_TOKEN>` without a browser session.
 
-Those 12 hours are idle time, not a hard limit: opening an admin page, making any change,
+Those 90 days are idle time, not a hard limit: opening an admin page, making any change,
 or reading one while interacting with it slides the expiry forward once it is inside the
-last six hours. What deliberately does **not** extend it is the page's own status
+last 45 days. What deliberately does **not** extend it is the page's own status
 poll — a console left open on a second monitor still times out, which is the whole point
 of the TTL. The page marks its own requests with `X-Memby-Admin-Active` when there has
 been interaction in the last five minutes, and on a 401 it reloads, so an expiry lands as

server/cmd/memby-credits/main.go

@@ -51,6 +51,10 @@ func run(itemID string) error {
 		cfg.EmbyURL, cfg.EmbyPublicURL, cfg.ClientName, cfg.GatewayClientName,
 		cfg.UpstreamTimeout,
 	)
+	// The bench measures the path the service actually takes, so it must read bytes from the
+	// same address the service reads them from. Benchmarking the public route and deploying
+	// the internal one would report a number belonging to neither.
+	embyClient.SetMediaURL(cfg.EmbyMediaURL)
 	resolver := credits.NewEmbyResolver(embyClient, emby.Credentials{
 		UserID: cfg.SyncUserID, Token: cfg.SyncAPIKey,
 		DeviceID: "memby-credits-bench", DeviceName: "MbyGateway Credits", Gateway: true,

server/cmd/memby-server/main.go

@@ -116,6 +116,7 @@ func run(log *slog.Logger, events *logging.Buffer) error {
 		cfg.EmbyURL, cfg.EmbyPublicURL, cfg.ClientName, cfg.GatewayClientName,
 		cfg.UpstreamTimeout,
 	)
+	embyClient.SetMediaURL(cfg.EmbyMediaURL)
 	mdblistClient := mdblist.New(mdblist.DefaultBaseURL, cfg.UpstreamTimeout)
 	var sonarrClient *sonarr.Client
 	if cfg.SonarrURL != "" {
@@ -217,10 +218,15 @@ func run(log *slog.Logger, events *logging.Buffer) error {
 			Config:    creditsConfig,
 		})
 		go creditsService.Run(ctx)
+		// media_url is on this line rather than the ready line because credits detection is
+		// the only thing that uses it, and because reading it back is the only way an
+		// operator can tell that a scan is taking the short path. Where it equals EmbyURL
+		// the scans go out the public way, which on a split host is the whole cost.
 		log.Info("credits detection enabled",
 			"prefetch", creditsConfig.PrefetchEpisodes,
 			"queue_limit", creditsConfig.QueueLimit,
-			"visual", detector != nil)
+			"visual", detector != nil,
+			"media_url", cfg.EmbyMediaURL)
 	}
 
 	// The administrative event bus, the integration dispatcher that subscribes to it and

server/internal/api/admin.go

@@ -185,7 +185,7 @@ func (s *Server) adminAuth(h http.HandlerFunc) http.Handler {
 			}
 		}
 		if subtle.ConstantTimeCompare([]byte(presented), []byte(s.cfg.AdminToken)) != 1 ||
-			(browser && !s.validInstallerSession(r)) {
+			(browser && !s.validAdminSession(r)) {
 			writeError(w, http.StatusUnauthorized, "invalid admin token")
 			return
 		}

server/internal/api/admin_access_test.go

@@ -0,0 +1,192 @@
+package api
+
+import (
+	"io"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/ponzischeme89/memby/server/internal/config"
+	"github.com/ponzischeme89/memby/server/internal/emby"
+)
+
+// embyAccessLevel stands in for an Emby whose answer about a person's access level is
+// under the test's control. userPolicy is the policy the authentication response carries
+// ("" for a server that sends none, which is what sends the gate to ask again), and
+// lookupPolicy is what a direct read of the account then answers ("" to fail that read).
+func embyAccessLevel(t *testing.T, userPolicy, lookupPolicy string) *Server {
+	t.Helper()
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.URL.Path == "/Users/AuthenticateByName":
+			policy := ""
+			if userPolicy != "" {
+				policy = `,"Policy":` + userPolicy
+			}
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = io.WriteString(w, `{
+				"User":{"Id":"emby-user","Name":"Viewer"`+policy+`},
+				"AccessToken":"temporary-emby-token",
+				"ServerId":"emby-server"
+			}`)
+		case r.URL.Path == "/Users/emby-user":
+			if lookupPolicy == "" {
+				http.Error(w, "no", http.StatusInternalServerError)
+				return
+			}
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = io.WriteString(w,
+				`{"Id":"emby-user","Name":"Viewer","Policy":`+lookupPolicy+`}`)
+		case r.URL.Path == "/Sessions/Logout":
+			w.WriteHeader(http.StatusNoContent)
+		case r.URL.Path == "/Devices":
+			if r.Method == http.MethodGet {
+				_, _ = io.WriteString(w, `{"Items":[]}`)
+				return
+			}
+			w.WriteHeader(http.StatusNoContent)
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	t.Cleanup(upstream.Close)
+
+	return &Server{
+		cfg: config.Config{
+			AdminToken:          "secret",
+			ReleasePublishToken: "release-secret",
+			SyncUserID:          "service-user", SyncAPIKey: "service-token",
+		},
+		emby: emby.New(upstream.URL, upstream.URL, "MbyATV", "MbyGateway", 2*time.Second),
+		log:  slog.New(slog.NewTextHandler(io.Discard, nil)),
+	}
+}
+
+func signIn(s *Server, next string) *httptest.ResponseRecorder {
+	form := url.Values{
+		"username": {"Viewer"}, "password": {"correct horse"}, "next": {next},
+	}
+	req := httptest.NewRequest(http.MethodPost, "/install/login",
+		strings.NewReader(form.Encode()))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	rec := httptest.NewRecorder()
+	s.handleInstallLogin(rec, req)
+	return rec
+}
+
+func sessionCookie(rec *httptest.ResponseRecorder) *http.Cookie {
+	for _, cookie := range rec.Result().Cookies() {
+		if cookie.Name == installerCookieName {
+			return cookie
+		}
+	}
+	return nil
+}
+
+// The console administers the server, so knowing a household password is not the
+// qualification for reaching it. Emby's own user policy is the authority on who may, and
+// it is the one an operator already manages.
+func TestAdminSignInRequiresAnEmbyAdministrator(t *testing.T) {
+	s := embyAccessLevel(t, `{"IsAdministrator":false}`, "")
+
+	rec := signIn(s, "/admin/")
+
+	if rec.Code != http.StatusForbidden {
+		t.Fatalf("non-administrator sign-in = %d, want 403", rec.Code)
+	}
+	if sessionCookie(rec) != nil {
+		t.Fatal("a refused admin sign-in issued a session anyway")
+	}
+	// The wording must not separate "wrong password" from "right password, wrong person":
+	// somebody who may not administer the server has no business learning either.
+	if !strings.Contains(rec.Body.String(), "Sign-in failed.") {
+		t.Fatalf("refusal discloses more than a failed sign-in: %s", rec.Body.String())
+	}
+}
+
+// The installer is the other half of the same gate and is public by design: a viewer
+// putting Memby on a new television signs in there and must still be able to.
+func TestNonAdministratorMayStillUseTheInstaller(t *testing.T) {
+	s := embyAccessLevel(t, `{"IsAdministrator":false}`, "")
+
+	rec := signIn(s, "/install")
+
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("installer sign-in = %d, want 303", rec.Code)
+	}
+	cookie := sessionCookie(rec)
+	if cookie == nil {
+		t.Fatal("installer sign-in issued no session")
+	}
+	req := httptest.NewRequest(http.MethodGet, "/install", nil)
+	req.AddCookie(cookie)
+	if !s.validInstallerSession(req) {
+		t.Fatal("a viewer's installer session was not accepted by the installer")
+	}
+	if s.validAdminSession(req) {
+		t.Fatal("a viewer's installer session was accepted as an admin session")
+	}
+}
+
+func TestAdministratorSignInMintsAnAdminSession(t *testing.T) {
+	s := embyAccessLevel(t, `{"IsAdministrator":true}`, "")
+
+	rec := signIn(s, "/admin/overview")
+
+	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/admin/overview" {
+		t.Fatalf("admin sign-in = %d %q", rec.Code, rec.Header().Get("Location"))
+	}
+	cookie := sessionCookie(rec)
+	if cookie == nil {
+		t.Fatal("admin sign-in issued no session")
+	}
+	if cookie.MaxAge != int(adminSessionTTL/time.Second) {
+		t.Fatalf("admin cookie MaxAge = %d, want %d",
+			cookie.MaxAge, int(adminSessionTTL/time.Second))
+	}
+	req := httptest.NewRequest(http.MethodGet, "/admin/api/status", nil)
+	req.AddCookie(cookie)
+	if !s.validAdminSession(req) {
+		t.Fatal("an administrator's session was not accepted by the console")
+	}
+}
+
+// An Emby that returns no policy at all is a question, not a refusal — reading its silence
+// as "not an administrator" would lock an operator out of their own console.
+func TestAdminSignInAsksEmbyWhenTheAuthResponseCarriesNoPolicy(t *testing.T) {
+	s := embyAccessLevel(t, "", `{"IsAdministrator":true}`)
+
+	rec := signIn(s, "/admin/")
+
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("sign-in = %d, want the policy to be read directly and accepted", rec.Code)
+	}
+	cookie := sessionCookie(rec)
+	if cookie == nil {
+		t.Fatal("no session issued after the access level was read directly")
+	}
+	req := httptest.NewRequest(http.MethodGet, "/admin/api/status", nil)
+	req.AddCookie(cookie)
+	if !s.validAdminSession(req) {
+		t.Fatal("the session issued was not an admin session")
+	}
+}
+
+// And an Emby that will not answer either way must not be guessed at in the permissive
+// direction: no answer means no session.
+func TestAdminSignInIsRefusedWhenTheAccessLevelCannotBeRead(t *testing.T) {
+	s := embyAccessLevel(t, "", "")
+
+	rec := signIn(s, "/admin/")
+
+	if rec.Code != http.StatusBadGateway {
+		t.Fatalf("unreadable access level = %d, want 502", rec.Code)
+	}
+	if sessionCookie(rec) != nil {
+		t.Fatal("a session was issued without knowing the access level")
+	}
+}

server/internal/api/admin_spa.go

@@ -100,7 +100,7 @@ func (s *Server) handleAdminConsole(w http.ResponseWriter, r *http.Request) {
 		_, _ = w.Write([]byte(adminUnavailablePage))
 		return
 	}
-	if !s.validInstallerSession(r) {
+	if !s.validAdminSession(r) {
 		// The sign-in form is still the gateway's, server-rendered, and returns to
 		// wherever the operator was trying to go. It is deliberately not part of the SPA:
 		// a login page that has to be downloaded from the thing it guards is one more
@@ -109,7 +109,7 @@ func (s *Server) handleAdminConsole(w http.ResponseWriter, r *http.Request) {
 		s.renderAccessLogin(w, r, "", http.StatusOK, r.URL.Path)
 		return
 	}
-	// Opening a page is somebody at the keyboard, so it starts the twelve-hour clock again.
+	// Opening a page is somebody at the keyboard, so it starts the clock again.
 	s.renewAdminSession(w, r)
 	s.setAdminTokenCookie(w, r)
 	preventDiscovery(w)

server/internal/api/admin_test.go

@@ -123,13 +123,15 @@ func TestHealthAndAdminStayReachableDuringMaintenance(t *testing.T) {
 	}
 }
 
-// installerSessionExpiring mints a session with a chosen life left, which is the only way
-// to reach the renewal window without waiting six hours in a test.
-func installerSessionExpiring(t *testing.T, s *Server, remaining time.Duration) *http.Cookie {
+// browserSessionExpiring mints a session of one purpose with a chosen life left, which is
+// the only way to reach the renewal window without waiting weeks in a test.
+func browserSessionExpiring(
+	t *testing.T, s *Server, purpose string, remaining time.Duration,
+) *http.Cookie {
 	t.Helper()
 	payload := make([]byte, 8+16)
 	binary.BigEndian.PutUint64(payload[:8], uint64(time.Now().Add(remaining).Unix()))
-	signature := s.signInstallerValue("session", payload)
+	signature := s.signInstallerValue(purpose, payload)
 	return &http.Cookie{
 		Name: installerCookieName,
 		Value: base64.RawURLEncoding.EncodeToString(payload) + "." +
@@ -137,10 +139,15 @@ func installerSessionExpiring(t *testing.T, s *Server, remaining time.Duration)
 	}
 }
 
+func adminSessionExpiring(t *testing.T, s *Server, remaining time.Duration) *http.Cookie {
+	t.Helper()
+	return browserSessionExpiring(t, s, adminSessionPurpose, remaining)
+}
+
 func adminRequest(s *Server, remaining time.Duration, t *testing.T) *http.Request {
 	req := httptest.NewRequest(http.MethodGet, "/admin/api/status", nil)
 	req.AddCookie(&http.Cookie{Name: adminCookieName, Value: s.cfg.AdminToken})
-	req.AddCookie(installerSessionExpiring(t, s, remaining))
+	req.AddCookie(adminSessionExpiring(t, s, remaining))
 	return req
 }
 
@@ -182,7 +189,7 @@ func TestAdminSessionIsExtendedWhileTheOperatorIsWorking(t *testing.T) {
 	}
 	follow := httptest.NewRequest(http.MethodGet, "/admin/api/status", nil)
 	follow.AddCookie(cookie)
-	expires, ok := server.installerSessionExpiry(follow)
+	expires, ok := server.browserSessionExpiry(follow, adminSessionPurpose)
 	if !ok || time.Until(expires) < adminSessionTTL-time.Minute {
 		t.Fatalf("renewed session should carry a full TTL, has %v (ok=%v)",
 			time.Until(expires), ok)
@@ -242,7 +249,7 @@ func TestAdminMutationExtendsTheSessionWithoutTheActivityHeader(t *testing.T) {
 
 	req := httptest.NewRequest(http.MethodPost, "/admin/api/sync", nil)
 	req.AddCookie(&http.Cookie{Name: adminCookieName, Value: server.cfg.AdminToken})
-	req.AddCookie(installerSessionExpiring(t, server, 2*time.Minute))
+	req.AddCookie(adminSessionExpiring(t, server, 2*time.Minute))
 	rec := httptest.NewRecorder()
 	handler.ServeHTTP(rec, req)
 
@@ -550,7 +557,7 @@ func TestAdminAuthAcceptsPersistentCookie(t *testing.T) {
 	})
 	req := httptest.NewRequest(http.MethodGet, "/admin/api/status", nil)
 	req.AddCookie(&http.Cookie{Name: adminCookieName, Value: "secret"})
-	addInstallerSession(t, server, req)
+	req.AddCookie(adminSessionExpiring(t, server, adminSessionTTL))
 	rec := httptest.NewRecorder()
 
 	handler.ServeHTTP(rec, req)
@@ -560,6 +567,43 @@ func TestAdminAuthAcceptsPersistentCookie(t *testing.T) {
 	}
 }
 
+// The installer is public: any member of the household signs in there to put Memby on a
+// new television. One cookie serves both gates, so the console has to be able to tell the
+// two sign-ins apart — otherwise a viewer's installer session reached /admin/, which then
+// handed them the admin token cookie.
+func TestInstallerSessionCannotReachTheAdminConsole(t *testing.T) {
+	server := testServer(config.Config{
+		AdminToken: "secret", ReleasePublishToken: "release-secret",
+	})
+	handler := server.adminAuth(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	})
+	req := httptest.NewRequest(http.MethodGet, "/admin/api/status", nil)
+	req.AddCookie(&http.Cookie{Name: adminCookieName, Value: "secret"})
+	addInstallerSession(t, server, req)
+	rec := httptest.NewRecorder()
+
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusUnauthorized {
+		t.Fatalf("an installer session reached the admin API: %d", rec.Code)
+	}
+}
+
+// The other direction is deliberately allowed: somebody who may administer the server may
+// certainly download the app.
+func TestAdminSessionIsAcceptedByTheInstaller(t *testing.T) {
+	server := testServer(config.Config{
+		AdminToken: "secret", ReleasePublishToken: "release-secret",
+	})
+	req := httptest.NewRequest(http.MethodGet, "/install", nil)
+	req.AddCookie(adminSessionExpiring(t, server, adminSessionTTL))
+
+	if !server.validInstallerSession(req) {
+		t.Fatal("an administrator's session should satisfy the installer gate")
+	}
+}
+
 func TestAdminPageRequiresDiscreetEmbyGate(t *testing.T) {
 	server := testServer(config.Config{
 		AdminToken: "secret", ReleasePublishToken: "release-secret",

server/internal/api/credits_detection.go

@@ -2,7 +2,6 @@ package api
 
 import (
 	"context"
-	"fmt"
 	"time"
 
 	"github.com/ponzischeme89/memby/server/internal/scheduler"
@@ -98,18 +97,6 @@ func (s *Server) RegisterCreditsTasks(sched *scheduler.Scheduler) {
 	})
 }
 
-// creditsQueueDetail is the one line the admin console prints about the queue.
-func (s *Server) creditsQueueDetail() string {
-	if s.credits == nil {
-		return ""
-	}
-	depth := s.credits.QueueDepth()
-	if depth == 0 {
-		return ""
-	}
-	return fmt.Sprintf("%d episode%s awaiting credits detection", depth, plural(depth))
-}
-
 // playbackSessionKey identifies one stream for the load gauge.
 //
 // The play session where Emby issued one, because that is what distinguishes two
@@ -122,10 +109,3 @@ func playbackSessionKey(deviceID, playSessionID string) string {
 	}
 	return deviceID
 }
-
-func plural(count int) string {
-	if count == 1 {
-		return ""
-	}
-	return "s"
-}

server/internal/api/features.go

@@ -88,9 +88,10 @@ var featureCatalogue = []featureDefinition{
 	{
 		Key: featureEndCredits, Name: "Speed through the credits", Area: "Playback",
 		Description: "Shrink the picture and run the closing credits at double speed with " +
-			"the next episode beside them, from the credits marker Emby writes. It is read " +
-			"from the same chapter list as the title sequence, so turning this off saves no " +
-			"request unless that is off too.",
+			"the next episode beside them. Emby's own marker is preferred where it has one, " +
+			"and where it has none the position discovered for the episodes the household " +
+			"is about to watch is used instead. It is read from the same chapter list as the " +
+			"title sequence, so turning this off saves no request unless that is off too.",
 		DefaultEnabled: true, MinimumProtocol: 1, Capability: "end_credits_v1",
 		Recovery: "Takes effect the next time playback starts; the credits simply play out full size.",
 	},

server/internal/api/installer_auth.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"context"
 	"crypto/hmac"
 	"crypto/rand"
 	"crypto/sha256"
@@ -17,12 +18,29 @@ import (
 const (
 	installerCookieName = "memby_installer"
 	installerSessionTTL = 30 * time.Minute
-	adminSessionTTL     = 12 * time.Hour
-	installerDeviceID   = "memby-web-installer"
+	// adminSessionTTL is deliberately long. The console is reached from the household's
+	// own machines, the sign-in behind it is an Emby password check, and an operator who
+	// opens it once a month was being asked for that password every single visit — which
+	// is the shape of a gate people work around rather than one that protects anything.
+	// Ninety days of idle time matches MEMBY_SESSION_IDLE_EXPIRY, so a browser and a
+	// television are forgotten on the same schedule.
+	adminSessionTTL   = 90 * 24 * time.Hour
+	installerDeviceID = "memby-web-installer"
 
 	// adminRenewWithin is how close to expiry a session must be before an operator's own
 	// request re-issues it. Half the TTL avoids rewriting the cookie on every request.
 	adminRenewWithin = adminSessionTTL / 2
+
+	// A browser session says what it may be used for, and it says so by being signed with
+	// its own purpose rather than by carrying a claim the holder could edit. The two gates
+	// are not one gate: /install is public by design — any member of the household signs
+	// in there to install Memby on a new television — while the console administers the
+	// server. One cookie serves both, so without this separation an ordinary viewer's
+	// installer sign-in satisfied the console's gate, and opening /admin/ then handed them
+	// the admin token cookie. An admin session is accepted at /install as well, since
+	// somebody who may administer the server may certainly download the app.
+	installerSessionPurpose = "session"
+	adminSessionPurpose     = "admin session"
 )
 
 // gatewayDeviceName is what Emby records for a device row the gateway creates for itself.
@@ -62,23 +80,24 @@ func (s *Server) signInstallerValue(purpose string, payload []byte) []byte {
 }
 
 func (s *Server) newInstallerSession() (string, error) {
-	return s.newBrowserSession(installerSessionTTL)
+	return s.newBrowserSession(installerSessionPurpose, installerSessionTTL)
 }
 
-func (s *Server) newBrowserSession(ttl time.Duration) (string, error) {
+func (s *Server) newBrowserSession(purpose string, ttl time.Duration) (string, error) {
 	payload := make([]byte, 8+16)
 	binary.BigEndian.PutUint64(payload[:8], uint64(time.Now().Add(ttl).Unix()))
 	if _, err := rand.Read(payload[8:]); err != nil {
 		return "", err
 	}
-	signature := s.signInstallerValue("session", payload)
+	signature := s.signInstallerValue(purpose, payload)
 	return base64.RawURLEncoding.EncodeToString(payload) + "." +
 		base64.RawURLEncoding.EncodeToString(signature), nil
 }
 
-// installerSessionExpiry reports when the request's session runs out. A cookie that is
-// missing, malformed, forged or already expired is reported the same way: no session.
-func (s *Server) installerSessionExpiry(r *http.Request) (time.Time, bool) {
+// browserSessionExpiry reports when the request's session of this purpose runs out. A
+// cookie that is missing, malformed, forged, signed for a different purpose or already
+// expired is reported the same way: no session.
+func (s *Server) browserSessionExpiry(r *http.Request, purpose string) (time.Time, bool) {
 	if len(s.installerSecret()) == 0 {
 		return time.Time{}, false
 	}
@@ -95,7 +114,7 @@ func (s *Server) installerSessionExpiry(r *http.Request) (time.Time, bool) {
 		return time.Time{}, false
 	}
 	signature, err := base64.RawURLEncoding.DecodeString(parts[1])
-	if err != nil || !hmac.Equal(signature, s.signInstallerValue("session", payload)) {
+	if err != nil || !hmac.Equal(signature, s.signInstallerValue(purpose, payload)) {
 		return time.Time{}, false
 	}
 	expires := int64(binary.BigEndian.Uint64(payload[:8]))
@@ -106,8 +125,20 @@ func (s *Server) installerSessionExpiry(r *http.Request) (time.Time, bool) {
 	return time.Unix(expires, 0), true
 }
 
+// validInstallerSession gates the public installer, which an administrator's own session
+// satisfies too.
 func (s *Server) validInstallerSession(r *http.Request) bool {
-	_, ok := s.installerSessionExpiry(r)
+	if s.validAdminSession(r) {
+		return true
+	}
+	_, ok := s.browserSessionExpiry(r, installerSessionPurpose)
+	return ok
+}
+
+// validAdminSession gates the console. Only a sign-in Emby confirmed as an administrator
+// mints one of these, so a household member's installer cookie cannot reach it.
+func (s *Server) validAdminSession(r *http.Request) bool {
+	_, ok := s.browserSessionExpiry(r, adminSessionPurpose)
 	return ok
 }
 
@@ -118,11 +149,11 @@ func (s *Server) validInstallerSession(r *http.Request) bool {
 // an operator actually made — see operatorPresent — or an abandoned tab's own polling
 // would keep the session alive indefinitely, which is what the TTL exists to stop.
 func (s *Server) renewAdminSession(w http.ResponseWriter, r *http.Request) {
-	expires, ok := s.installerSessionExpiry(r)
+	expires, ok := s.browserSessionExpiry(r, adminSessionPurpose)
 	if !ok || time.Until(expires) > adminRenewWithin {
 		return
 	}
-	session, err := s.newBrowserSession(adminSessionTTL)
+	session, err := s.newBrowserSession(adminSessionPurpose, adminSessionTTL)
 	if err != nil {
 		s.loggerFor(r.Context()).Error("installer session renewal failed", "error", err)
 		return
@@ -183,6 +214,26 @@ func (s *Server) allowedReleaseDownload(r *http.Request, filename string) bool {
 	return expected != "" && hmac.Equal([]byte(presented), []byte(expected))
 }
 
+// embyAdministrator asks Emby whether the account that just signed in administers the
+// server — the access level in its own user policy, which is the only authority on the
+// question and the one an operator already manages. Emby answers it in the authentication
+// response, so this normally costs nothing; a response carrying no policy at all is asked
+// again directly rather than read as a refusal, because reading silence as "no" would lock
+// an operator out of their own console with no way back in.
+func (s *Server) embyAdministrator(ctx context.Context, auth *emby.AuthResult) (bool, error) {
+	if auth.User.Policy.IsAdministrator != nil {
+		return *auth.User.Policy.IsAdministrator, nil
+	}
+	user, err := s.emby.UserByID(ctx, emby.Credentials{
+		UserID: auth.User.ID, Token: auth.AccessToken,
+		DeviceID: installerDeviceID, DeviceName: s.installerDeviceName(), Gateway: true,
+	}, auth.User.ID)
+	if err != nil {
+		return false, err
+	}
+	return user.Policy.IsAdministrator, nil
+}
+
 func (s *Server) handleInstallLogin(w http.ResponseWriter, r *http.Request) {
 	if len(s.installerSecret()) == 0 {
 		http.NotFound(w, r)
@@ -222,6 +273,10 @@ func (s *Server) handleInstallLogin(w http.ResponseWriter, r *http.Request) {
 		s.renderAccessLogin(w, r, "Sign-in failed.", http.StatusUnauthorized, next)
 		return
 	}
+	// Ask before the token is retired below: the fallback lookup needs it. Whether the
+	// answer is wanted depends on where the sign-in was headed, but it is asked either way
+	// so that the cleanup underneath runs on one path rather than two.
+	administrator, adminErr := s.embyAdministrator(r.Context(), auth)
 	// Authentication creates an Emby access token. The installer needs only proof that
 	// it succeeded, so retire the upstream session immediately and never persist it.
 	if err := s.emby.Logout(r.Context(), emby.Credentials{
@@ -242,11 +297,27 @@ func (s *Server) handleInstallLogin(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	ttl := installerSessionTTL
+	purpose, ttl := installerSessionPurpose, installerSessionTTL
 	if strings.HasPrefix(next, "/admin/") {
-		ttl = adminSessionTTL
+		if adminErr != nil {
+			s.loggerFor(r.Context()).Error("admin sign-in could not read Emby access level",
+				"user", username, "error", adminErr)
+			s.renderAccessLogin(w, r, "Sign-in is temporarily unavailable.",
+				http.StatusBadGateway, next)
+			return
+		}
+		if !administrator {
+			// Deliberately the same wording an unknown password gets. Somebody who is not
+			// an administrator has no business learning that the console exists and that
+			// their password was right; the operator can see the refusal in the log.
+			s.loggerFor(r.Context()).Warn("admin sign-in refused: not an Emby administrator",
+				"user", username)
+			s.renderAccessLogin(w, r, "Sign-in failed.", http.StatusForbidden, next)
+			return
+		}
+		purpose, ttl = adminSessionPurpose, adminSessionTTL
 	}
-	session, err := s.newBrowserSession(ttl)
+	session, err := s.newBrowserSession(purpose, ttl)
 	if err != nil {
 		s.loggerFor(r.Context()).Error("installer session generation failed", "error", err)
 		writeError(w, http.StatusInternalServerError, "could not start installer session")

server/internal/api/release_test.go

@@ -252,7 +252,8 @@ func TestInstallerLoginUsesEmbyWithoutCreatingTVSession(t *testing.T) {
 		case "/Users/AuthenticateByName":
 			w.Header().Set("Content-Type", "application/json")
 			_, _ = io.WriteString(w, `{
-				"User":{"Id":"emby-user","Name":"Matt"},
+				"User":{"Id":"emby-user","Name":"Matt",
+					"Policy":{"IsAdministrator":true}},
 				"AccessToken":"temporary-emby-token",
 				"ServerId":"emby-server"
 			}`)

server/internal/buildinfo/VERSION

@@ -1 +1 @@
-0.1.42
+0.1.45

server/internal/config/config.go

@@ -22,6 +22,22 @@ type Config struct {
 	// Defaults to EmbyURL; set it when the gateway talks to Emby over a network the
 	// TVs cannot reach.
 	EmbyPublicURL string
+	// EmbyMediaURL is the address the gateway reads *media bytes* from, which is a
+	// different question from how it reads metadata and is the only place the difference
+	// costs anything.
+	//
+	// Credits detection is the one thing on the server side that opens a media file, and it
+	// does so with ranged reads over HTTP. A metadata call is a few kilobytes and does not
+	// care which way it is routed; a scan is megabytes, and where EmbyURL is a public
+	// hostname — which it legitimately may be, since the gateway and Emby need not share a
+	// network — every one of those ranged reads leaves the host for the internet-facing
+	// edge, pays TLS, and comes back in through a reverse proxy that is free to buffer the
+	// response and discard the range economy entirely.
+	//
+	// So this is stated separately rather than inferred: there is no way to look at a URL
+	// and tell whether it happens to resolve locally. Unset, it falls back to EmbyURL and
+	// nothing changes.
+	EmbyMediaURL string
 
 	DatabaseURL string
 	RedisURL    string
@@ -191,6 +207,7 @@ func Load() (Config, error) {
 		ListenAddr:        env("MEMBY_LISTEN_ADDR", ":8080"),
 		EmbyURL:           strings.TrimRight(os.Getenv("MEMBY_EMBY_URL"), "/"),
 		EmbyPublicURL:     strings.TrimRight(os.Getenv("MEMBY_EMBY_PUBLIC_URL"), "/"),
+		EmbyMediaURL:      strings.TrimRight(os.Getenv("MEMBY_EMBY_MEDIA_URL"), "/"),
 		DatabaseURL:       os.Getenv("MEMBY_DATABASE_URL"),
 		RedisURL:          env("MEMBY_REDIS_URL", "redis://localhost:6379/0"),
 		ClientName:        env("MEMBY_CLIENT_NAME", "MbyATV"),
@@ -262,6 +279,9 @@ func Load() (Config, error) {
 	if c.EmbyPublicURL == "" {
 		c.EmbyPublicURL = c.EmbyURL
 	}
+	if c.EmbyMediaURL == "" {
+		c.EmbyMediaURL = c.EmbyURL
+	}
 	if c.ReleasePublishToken != "" && c.PublicURL == "" {
 		return c, fmt.Errorf("MEMBY_PUBLIC_URL is required when release publishing is enabled")
 	}

server/internal/credits/README.md

@@ -77,6 +77,28 @@ costs a 0.3 penalty, which usually means storing nothing. **Prefer no marker to
 marker** is the governing rule throughout: a missing Skip Credits button is an absence nobody
 notices, a button during the final scene is a fault they remember.
 
+## Where the bytes come from
+
+The gateway has no filesystem access to the media, so a scan reads Emby's own stream route
+over HTTP and `-ss` ahead of `-i` is what makes that a ranged request rather than a download.
+That optimisation is only worth anything if the range survives the trip, which is why the
+address is configurable separately from every other way the gateway reaches Emby.
+
+`MEMBY_EMBY_MEDIA_URL` is the address media bytes are read from; unset it falls back to
+`MEMBY_EMBY_URL` and nothing changes. The distinction is not cosmetic in this deployment: the
+stack runs on the NAS, Emby and the media live on the HTPC, and `MEMBY_EMBY_URL` is a public
+DDNS name. Left to fall back, every ranged read leaves the host for the internet-facing edge,
+pays TLS and returns through a reverse proxy — and a proxy that buffers its upstream turns
+the ranged read into a whole-file read, which is the single thing this package is built not to
+do. Naming the LAN address instead keeps the read on the wire between the two machines.
+
+It is **stated rather than inferred** for the usual reason: there is no way to look at a URL
+and tell whether it happens to resolve locally, and guessing wrong either sends scans the long
+way round or points them at a host that is not there. `media_url` is on the `credits detection
+enabled` start-up line so an operator can read back which path is in force, and the benchmark
+below sets it too — measuring the public route and deploying the internal one would report a
+number belonging to neither.
+
 ## Cost, and what is still unmeasured
 
 **Derived arithmetic** (checkable without hardware):

server/internal/emby/client.go

@@ -24,6 +24,7 @@ import (
 type Client struct {
 	baseURL    string
 	publicURL  string
+	mediaURL   string
 	clientName string
 	// gatewayClientName identifies the requests the gateway makes on its own behalf, so
 	// Emby's device list separates a television from the server standing behind it. The
@@ -72,8 +73,17 @@ type ItemsResult struct {
 
 type AuthResult struct {
 	User struct {
-		ID   string `json:"Id"`
-		Name string `json:"Name"`
+		ID     string `json:"Id"`
+		Name   string `json:"Name"`
+		Policy struct {
+			// IsAdministrator is a pointer because "Emby says this person is not an
+			// administrator" and "Emby did not answer the question" are different facts
+			// that must be acted on differently: the first refuses the console, the second
+			// is worth asking again rather than locking an operator out of their own
+			// server. Emby returns the policy in the authentication response itself, so
+			// the ordinary path costs no extra request.
+			IsAdministrator *bool `json:"IsAdministrator"`
+		} `json:"Policy"`
 	} `json:"User"`
 	AccessToken string `json:"AccessToken"`
 	ServerID    string `json:"ServerId"`
@@ -83,7 +93,8 @@ type User struct {
 	ID     string `json:"Id"`
 	Name   string `json:"Name"`
 	Policy struct {
-		IsDisabled bool `json:"IsDisabled"`
+		IsDisabled      bool `json:"IsDisabled"`
+		IsAdministrator bool `json:"IsAdministrator"`
 	} `json:"Policy"`
 }
 
@@ -174,6 +185,18 @@ func New(baseURL, publicURL, clientName, gatewayClientName string, timeout time.
 	}
 }
 
+// SetMediaURL names the address server-side media reads go to, which is only ever credits
+// detection. Unset — or set to nothing — media reads use the same address as metadata.
+//
+// A setter rather than a constructor argument because it is one deployment's answer to one
+// subsystem's problem, and threading it through four test call sites that will never use it
+// would be paying for it everywhere to spend it in one place. Call it during start-up,
+// before anything is serving: nothing here is synchronised, for the same reason the client's
+// other addresses are not.
+func (c *Client) SetMediaURL(mediaURL string) {
+	c.mediaURL = strings.TrimRight(strings.TrimSpace(mediaURL), "/")
+}
+
 // Authenticate signs a television in. cred carries the device the record is created for
 // and that set's ClientVersion — Emby stamps it on the record, so an empty one leaves the
 // entry claiming the gateway's own build. cred.Gateway marks a sign-in the gateway is
@@ -247,6 +270,22 @@ func (c *Client) DeleteDevice(
 	return nil
 }
 
+// UserByID reads one account with that account's own token. It exists for the admin gate
+// and is asked only when an authentication response carried no policy at all, which is
+// why it takes the credentials it does: the question is "who did I just authenticate",
+// and an Emby user may always read themselves.
+func (c *Client) UserByID(ctx context.Context, cred Credentials, userID string) (*User, error) {
+	req, err := c.newRequest(ctx, http.MethodGet, "/Users/"+url.PathEscape(userID), nil, cred, nil)
+	if err != nil {
+		return nil, err
+	}
+	var user User
+	if err := c.do(req, &user); err != nil {
+		return nil, err
+	}
+	return &user, nil
+}
+
 // Users returns the household accounts visible to an administrative/service token.
 // It is used only by the background For You builder, never on a television request.
 func (c *Client) Users(ctx context.Context, cred Credentials) ([]User, error) {
@@ -593,19 +632,29 @@ func (c *Client) StreamURL(cred Credentials, itemID string) string {
 	return fmt.Sprintf("%s/Videos/%s/stream?%s", c.publicURL, url.PathEscape(itemID), params.Encode())
 }
 
-// InternalStreamURL is the same file, addressed the way the *gateway* reaches Emby rather
+// InternalStreamURL is the same file, addressed the way the *gateway* reads bytes rather
 // than the way a television does.
 //
 // It exists for credits detection, which is the only thing that reads media bytes on the
-// server side. Using StreamURL there would send a ranged read out to the public address and
-// back in through the reverse proxy — the two containers are on the same network, and a scan
-// has no business leaving it. Nothing here is ever handed to a client.
+// server side, and it reads them as ranged requests over the tail of a file. Using StreamURL
+// there would send every one of those out to the public address and back in through the
+// reverse proxy — and where a proxy buffers the response, the ranged read stops being a
+// ranged read and the whole economy of the scan is gone. Nothing here is ever handed to a
+// client.
+//
+// mediaURL is preferred and baseURL is the fallback, because how the gateway reaches Emby
+// for *metadata* is not evidence about the best path for megabytes: a deployment whose
+// MEMBY_EMBY_URL is a public hostname is an ordinary one, not a misconfiguration.
 func (c *Client) InternalStreamURL(cred Credentials, itemID string) string {
+	host := c.mediaURL
+	if host == "" {
+		host = c.baseURL
+	}
 	params := url.Values{}
 	params.Set("static", "true")
 	params.Set("api_key", cred.Token)
 	params.Set("DeviceId", cred.DeviceID)
-	return fmt.Sprintf("%s/Videos/%s/stream?%s", c.baseURL, url.PathEscape(itemID), params.Encode())
+	return fmt.Sprintf("%s/Videos/%s/stream?%s", host, url.PathEscape(itemID), params.Encode())
 }
 
 // DeliveryURL converts a PlaybackInfo URL into a TV-reachable, authenticated URL.

server/internal/emby/client_media_url_test.go

@@ -0,0 +1,74 @@
+package emby
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+// Where the gateway reads media bytes from is the one address that is not interchangeable
+// with the others, so all three are pinned against each other here: a television must never
+// be handed the internal address, and a scan must never be sent out the public way when an
+// internal one has been named.
+
+func TestInternalStreamURLPrefersTheMediaAddress(t *testing.T) {
+	client := New(
+		"https://molise.bounceme.net", "https://molise.bounceme.net",
+		"MbyATV", "MbyGateway", time.Second,
+	)
+	client.SetMediaURL("http://10.0.0.2:8096")
+
+	stream := client.InternalStreamURL(Credentials{Token: "tok", DeviceID: "dev"}, "item-1")
+	if !strings.HasPrefix(stream, "http://10.0.0.2:8096/Videos/item-1/stream?") {
+		t.Fatalf("scan should read from the media address, got %q", stream)
+	}
+}
+
+// The fallback is what makes the setting optional. A deployment that never names a media
+// address must behave exactly as it did before there was one, or adding the option would be
+// a breaking change to every install that ignores it.
+func TestInternalStreamURLFallsBackToTheGatewayAddress(t *testing.T) {
+	client := New("http://emby:8096", "https://public.example", "MbyATV", "MbyGateway", time.Second)
+
+	stream := client.InternalStreamURL(Credentials{Token: "tok", DeviceID: "dev"}, "item-1")
+	if !strings.HasPrefix(stream, "http://emby:8096/Videos/item-1/stream?") {
+		t.Fatalf("with no media address the scan should use the gateway address, got %q", stream)
+	}
+}
+
+// A blank or whitespace value is the same as unset. It arrives from an environment variable
+// somebody left empty, which is the ordinary way to turn the setting off again, and treating
+// it as an address would build "/Videos/…" and read from the gateway itself.
+func TestBlankMediaURLIsTreatedAsUnset(t *testing.T) {
+	client := New("http://emby:8096", "https://public.example", "MbyATV", "MbyGateway", time.Second)
+	client.SetMediaURL("   ")
+
+	stream := client.InternalStreamURL(Credentials{Token: "tok", DeviceID: "dev"}, "item-1")
+	if !strings.HasPrefix(stream, "http://emby:8096/Videos/") {
+		t.Fatalf("blank media address should fall back, got %q", stream)
+	}
+}
+
+// A trailing slash is what an operator actually types, and it must not reach the URL as a
+// double slash — some reverse proxies answer that with a redirect ffmpeg will not follow.
+func TestMediaURLTolerantOfATrailingSlash(t *testing.T) {
+	client := New("http://emby:8096", "https://public.example", "MbyATV", "MbyGateway", time.Second)
+	client.SetMediaURL("http://10.0.0.2:8096/")
+
+	stream := client.InternalStreamURL(Credentials{Token: "tok", DeviceID: "dev"}, "item-1")
+	if !strings.HasPrefix(stream, "http://10.0.0.2:8096/Videos/") {
+		t.Fatalf("media address should lose its trailing slash, got %q", stream)
+	}
+}
+
+// The television's URL is the public address and is not affected by any of this. Nothing
+// reachable only from the NAS may ever be handed to a set in the house.
+func TestStreamURLForTelevisionsIgnoresTheMediaAddress(t *testing.T) {
+	client := New("http://emby:8096", "https://public.example", "MbyATV", "MbyGateway", time.Second)
+	client.SetMediaURL("http://10.0.0.2:8096")
+
+	stream := client.StreamURL(Credentials{Token: "tok", DeviceID: "dev"}, "item-1")
+	if !strings.HasPrefix(stream, "https://public.example/Videos/item-1/stream?") {
+		t.Fatalf("televisions must keep the public address, got %q", stream)
+	}
+}