Add appservice auth mode behind AUTH_MODE; land device grant

Two things, entangled in the working tree because 20d1f92 was mislabeled (its message claimed "device grant" but it only deleted registration.yaml.example and left the failed appservice+/sync hybrid in client.go): 1. Land the MAS OAuth 2.0 device grant that was running in prod but never committed: masauth.go + client.go rewrite. Bot stays a normal user so /sync works; refresh token persisted in data/mas_auth.json. 2. Add "appservice" as an alternate transport behind AUTH_MODE (default "masdevice" = unchanged device-grant path, instant rollback): - internal/bot/session.go: Session abstraction unifying both transports (OnEventType/Run/Stop); NewSession dispatches on AuthMode. - internal/bot/appservice.go: as_token auth (MAS-durable, no login/MFA/expiry), cryptohelper MSC4190 device creation, crypto machine fed from Synapse transaction pushes (to-device/device-lists/OTK) instead of /sync, inbound decrypt+redispatch, and lazy per-room StateStore backfill (encryption + members) so replies in encrypted rooms encrypt to the right recipients. - main.go: NewSession/sess.OnEventType/sess.Run in place of the /sync loop. - .env.example: AUTH_MODE, AS_REGISTRATION, AS_LISTEN_HOST/PORT, HOMESERVER_DOMAIN. The appservice path fixes the earlier hybrid's fatal flaw (Synapse forbids AS users from /sync) by using the transaction/push model. Bot-side only; Synapse registration + experimental_features (msc2409/msc3202/msc4190) and E2EE cutover are the next steps. Build + vet green (CGO=1 -tags goolm).
2026-07-15 08:32:41 +00:00 · 2026-07-03 17:11:58 -07:00
parent 20d1f92f97
commit 6387380d0a
9 changed files with 889 additions and 143 deletions
--- a/internal/bot/appservice.go
+++ b/internal/bot/appservice.go
@@ -0,0 +1,204 @@
+package bot
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/rs/zerolog"
+	"maunium.net/go/mautrix"
+	"maunium.net/go/mautrix/appservice"
+	"maunium.net/go/mautrix/crypto/cryptohelper"
+	"maunium.net/go/mautrix/event"
+	"maunium.net/go/mautrix/id"
+)
+
+// cryptoToDeviceTypes are the to-device event types the crypto machine must see
+// to establish Olm/Megolm sessions and share/receive room keys. In /sync mode
+// the cryptohelper gets these automatically; under the appservice transaction
+// model we route each one to mach.HandleToDeviceEvent ourselves.
+var cryptoToDeviceTypes = []event.Type{
+	event.ToDeviceEncrypted,
+	event.ToDeviceRoomKey,
+	event.ToDeviceForwardedRoomKey,
+	event.ToDeviceRoomKeyRequest,
+	event.ToDeviceRoomKeyWithheld,
+	event.ToDeviceOrgMatrixRoomKeyWithheld,
+	event.ToDeviceSecretRequest,
+	event.ToDeviceSecretSend,
+	event.ToDeviceDummy,
+}
+
+// newAppserviceSession builds the appservice-mode Session: as_token auth, a
+// cryptohelper that mints the bot's device via MSC4190, and an EventProcessor
+// fed by Synapse's transaction pushes (in place of /sync). The bot is an
+// appservice user — Synapse forbids AS users from /sync, so all events, plus the
+// E2EE extensions (to-device / device lists / OTK counts), arrive over the
+// transaction API instead.
+func newAppserviceSession(cfg Config) (*Session, error) {
+	if err := os.MkdirAll(cfg.DataDir, 0o755); err != nil {
+		return nil, fmt.Errorf("create data dir: %w", err)
+	}
+	if cfg.UserID == "" {
+		return nil, fmt.Errorf("BOT_USER_ID is required")
+	}
+	if cfg.RegistrationPath == "" {
+		return nil, fmt.Errorf("AS_REGISTRATION is required in appservice mode")
+	}
+	if cfg.HomeserverDomain == "" {
+		return nil, fmt.Errorf("HOMESERVER_DOMAIN is required in appservice mode (server_name, e.g. parodia.dev)")
+	}
+	if !((&appservice.HostConfig{Hostname: cfg.ListenHost, Port: cfg.ListenPort}).IsConfigured()) {
+		return nil, fmt.Errorf("AS_LISTEN_HOST/AS_LISTEN_PORT must be set in appservice mode")
+	}
+
+	ctx := context.Background()
+
+	reg, err := appservice.LoadRegistration(cfg.RegistrationPath)
+	if err != nil {
+		return nil, fmt.Errorf("load appservice registration %q: %w", cfg.RegistrationPath, err)
+	}
+	// Gate for to-device delivery: handleTransaction only pumps to-device events
+	// when this is set (appservice/http.go). Force it on regardless of the yaml so
+	// E2EE key exchange can't silently break on a missing field.
+	reg.EphemeralEvents = true
+
+	as, err := appservice.CreateFull(appservice.CreateOpts{
+		Registration:     reg,
+		HomeserverDomain: cfg.HomeserverDomain,
+		HomeserverURL:    cfg.Homeserver,
+		HostConfig:       appservice.HostConfig{Hostname: cfg.ListenHost, Port: cfg.ListenPort},
+	})
+	if err != nil {
+		return nil, fmt.Errorf("create appservice: %w", err)
+	}
+	// Surface the HTTP listener + transaction logs (default is a silent Nop).
+	as.Log = zerolog.New(os.Stderr).With().Timestamp().Str("component", "appservice").Logger().
+		Level(zerolog.InfoLevel)
+
+	userID := id.UserID(cfg.UserID)
+	if as.BotMXID() != userID {
+		return nil, fmt.Errorf("registration sender_localpart resolves to %s but BOT_USER_ID is %s", as.BotMXID(), userID)
+	}
+
+	client := as.BotClient() // as_token auth + SetAppServiceUserID (?user_id=) assertion
+
+	// Validate the token + identity before we start listening.
+	whoami, err := client.Whoami(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("appservice token validation failed (whoami): %w", err)
+	}
+	if whoami.UserID != userID {
+		return nil, fmt.Errorf("appservice identity mismatch: token resolves to %s but BOT_USER_ID is %s", whoami.UserID, userID)
+	}
+	slog.Info("appservice token valid", "user_id", whoami.UserID)
+
+	// ---- E2EE via cryptohelper (MSC4190 device creation, no /login) ----
+	cryptoDBPath := filepath.Join(cfg.DataDir, "crypto.db")
+	ch, err := cryptohelper.NewCryptoHelper(client, []byte("gogobee_pickle_key"), cryptoDBPath)
+	if err != nil {
+		return nil, fmt.Errorf("init crypto helper: %w", err)
+	}
+	// MSC4190: the appservice creates/refreshes its own device via PUT /devices
+	// instead of the UIA-gated login. The crypto store persists the device ID, so
+	// restarts reuse it. LoginAs carries only the display name (never calls /login
+	// in MSC4190 mode). client.Syncer is nil here, so Init does NOT wire /sync
+	// handlers — we drive the crypto machine from transactions below instead.
+	ch.MSC4190 = true
+	ch.LoginAs = &mautrix.ReqLogin{InitialDeviceDisplayName: cfg.DisplayName}
+	if err := ch.Init(ctx); err != nil {
+		return nil, fmt.Errorf("crypto helper init (MSC4190 device create): %w", err)
+	}
+	client.Crypto = ch
+
+	// ---- Event processor: replicate the cryptohelper's /sync wiring against
+	// the appservice transaction channels ----
+	ep := appservice.NewEventProcessor(as)
+	mach := ch.Machine()
+
+	// Crypto plumbing that /sync would otherwise carry:
+	ep.OnOTK(mach.HandleOTKCounts)
+	ep.OnDeviceList(mach.HandleDeviceLists)
+	for _, t := range cryptoToDeviceTypes {
+		ep.On(t, mach.HandleToDeviceEvent)
+	}
+
+	// Keep the client's StateStore current so outgoing sends know which rooms are
+	// encrypted and who to share keys with (no /sync backfill here), and let the
+	// crypto machine track membership for key sharing. PrependHandler so state is
+	// updated before app handlers (auto-join/moderation) run for the same event.
+	ep.PrependHandler(event.StateEncryption, func(ctx context.Context, evt *event.Event) {
+		mautrix.UpdateStateStore(ctx, as.StateStore, evt)
+	})
+	ep.PrependHandler(event.StateMember, func(ctx context.Context, evt *event.Event) {
+		mautrix.UpdateStateStore(ctx, as.StateStore, evt)
+		mach.HandleMemberEvent(ctx, evt)
+	})
+
+	// Without /sync there is no state backfill, so the client's StateStore starts
+	// empty. Before we hand off a decrypted event (whose reply may need to be
+	// encrypted), resolve the room once: mark it encrypted and populate its member
+	// list. Otherwise outbound sends go plaintext (IsEncrypted=false) and, worse,
+	// the group session is shared to nobody (GetRoomJoinedOrInvitedMembers empty)
+	// so recipients can't decrypt the bot's replies.
+	var resolved sync.Map // roomID -> struct{}, resolved once
+	resolveRoom := func(ctx context.Context, roomID id.RoomID) {
+		if _, done := resolved.LoadOrStore(roomID, struct{}{}); done {
+			return
+		}
+		var enc event.EncryptionEventContent
+		if err := client.StateEvent(ctx, roomID, event.StateEncryption, "", &enc); err == nil && enc.Algorithm != "" {
+			_ = as.StateStore.SetEncryptionEvent(ctx, roomID, &enc)
+		}
+		if members, err := client.Members(ctx, roomID); err == nil {
+			_ = as.StateStore.ReplaceCachedMembers(ctx, roomID, members.Chunk)
+		} else {
+			slog.Warn("appservice: failed to fetch room members; will retry", "room", roomID, "err", err)
+			resolved.Delete(roomID) // allow a later event to retry
+		}
+	}
+
+	// Decrypt inbound encrypted room events and re-dispatch the plaintext so the
+	// normal message/reaction handlers fire (mirrors cryptohelper.HandleEncrypted).
+	ep.On(event.EventEncrypted, func(ctx context.Context, evt *event.Event) {
+		resolveRoom(ctx, evt.RoomID)
+		decrypted, err := ch.Decrypt(ctx, evt)
+		if err != nil {
+			slog.Warn("appservice: failed to decrypt event", "room", evt.RoomID, "event", evt.ID, "err", err)
+			return
+		}
+		ep.Dispatch(ctx, decrypted)
+	})
+
+	return &Session{
+		Client: client,
+		mode:   "appservice",
+		as:     as,
+		ep:     ep,
+	}, nil
+}
+
+// runAppservice starts the transaction dispatchers and the HTTP listener, then
+// blocks until ctx is cancelled.
+func (s *Session) runAppservice(ctx context.Context) error {
+	s.ep.Start(ctx)
+	s.as.Ready = true
+
+	errCh := make(chan struct{})
+	go func() {
+		s.as.Start() // blocks in ListenAndServe until Stop()
+		close(errCh)
+	}()
+
+	slog.Info("appservice listener started", "address", s.as.Host.Address())
+
+	select {
+	case <-ctx.Done():
+		return nil
+	case <-errCh:
+		return fmt.Errorf("appservice HTTP listener exited unexpectedly")
+	}
+}