storage: Add OfflineSession object to backend storage.

server/handlers.go

@@ -682,6 +682,75 @@ func (s *Server) handleAuthCode(w http.ResponseWriter, r *http.Request, client s
 			s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 			return
 		}
+
+		// deleteToken determines if we need to delete the newly created refresh token
+		// due to a failure in updating/creating the OfflineSession object for the
+		// corresponding user.
+		var deleteToken bool
+		defer func() {
+			if deleteToken {
+				// Delete newly created refresh token from storage.
+				if err := s.storage.DeleteRefresh(refresh.ID); err != nil {
+					s.logger.Errorf("failed to delete refresh token: %v", err)
+					s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+					return
+				}
+			}
+		}()
+
+		tokenRef := storage.RefreshTokenRef{
+			ID:        refresh.ID,
+			ClientID:  refresh.ClientID,
+			CreatedAt: refresh.CreatedAt,
+			LastUsed:  refresh.LastUsed,
+		}
+
+		// Try to retrieve an existing OfflineSession object for the corresponding user.
+		if session, err := s.storage.GetOfflineSessions(refresh.Claims.UserID, refresh.ConnectorID); err != nil {
+			if err != storage.ErrNotFound {
+				s.logger.Errorf("failed to get offline session: %v", err)
+				s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+				deleteToken = true
+				return
+			}
+			offlineSessions := storage.OfflineSessions{
+				UserID:  refresh.Claims.UserID,
+				ConnID:  refresh.ConnectorID,
+				Refresh: make(map[string]*storage.RefreshTokenRef),
+			}
+			offlineSessions.Refresh[tokenRef.ClientID] = &tokenRef
+
+			// Create a new OfflineSession object for the user and add a reference object for
+			// the newly recieved refreshtoken.
+			if err := s.storage.CreateOfflineSessions(offlineSessions); err != nil {
+				s.logger.Errorf("failed to create offline session: %v", err)
+				s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+				deleteToken = true
+				return
+			}
+		} else {
+			if oldTokenRef, ok := session.Refresh[tokenRef.ClientID]; ok {
+				// Delete old refresh token from storage.
+				if err := s.storage.DeleteRefresh(oldTokenRef.ID); err != nil {
+					s.logger.Errorf("failed to delete refresh token: %v", err)
+					s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+					deleteToken = true
+					return
+				}
+			}
+
+			// Update existing OfflineSession obj with new RefreshTokenRef.
+			if err := s.storage.UpdateOfflineSessions(session.UserID, session.ConnID, func(old storage.OfflineSessions) (storage.OfflineSessions, error) {
+				old.Refresh[tokenRef.ClientID] = &tokenRef
+				return old, nil
+			}); err != nil {
+				s.logger.Errorf("failed to update offline session: %v", err)
+				s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+				deleteToken = true
+				return
+			}
+
+		}
 	}
 	s.writeAccessToken(w, idToken, accessToken, refreshToken, expiry)
 }
@@ -815,6 +884,7 @@ func (s *Server) handleRefreshToken(w http.ResponseWriter, r *http.Request, clie
 		return
 	}
 
+	lastUsed := s.now()
 	updater := func(old storage.RefreshToken) (storage.RefreshToken, error) {
 		if old.Token != refresh.Token {
 			return old, errors.New("refresh token claimed twice")
@@ -828,14 +898,31 @@ func (s *Server) handleRefreshToken(w http.ResponseWriter, r *http.Request, clie
 		old.Claims.EmailVerified = ident.EmailVerified
 		old.Claims.Groups = ident.Groups
 		old.ConnectorData = ident.ConnectorData
-		old.LastUsed = s.now()
+		old.LastUsed = lastUsed
 		return old, nil
 	}
+
+	// Update LastUsed time stamp in refresh token reference object
+	// in offline session for the user.
+	if err := s.storage.UpdateOfflineSessions(refresh.Claims.UserID, refresh.ConnectorID, func(old storage.OfflineSessions) (storage.OfflineSessions, error) {
+		if old.Refresh[refresh.ClientID].ID != refresh.ID {
+			return old, errors.New("refresh token invalid")
+		}
+		old.Refresh[refresh.ClientID].LastUsed = lastUsed
+		return old, nil
+	}); err != nil {
+		s.logger.Errorf("failed to update offline session: %v", err)
+		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+		return
+	}
+
+	// Update refresh token in the storage.
 	if err := s.storage.UpdateRefreshToken(refresh.ID, updater); err != nil {
 		s.logger.Errorf("failed to update refresh token: %v", err)
 		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 		return
 	}
+
 	s.writeAccessToken(w, idToken, accessToken, rawNewToken, expiry)
 }
 

server/server_test.go

@@ -971,3 +971,108 @@ func TestKeyCacher(t *testing.T) {
 		}
 	}
 }
+
+type oauth2Client struct {
+	config *oauth2.Config
+	token  *oauth2.Token
+	server *httptest.Server
+}
+
+// TestRefreshTokenFlow tests the refresh token code flow for oauth2. The test verifies
+// that only valid refresh tokens can be used to refresh an expired token.
+func TestRefreshTokenFlow(t *testing.T) {
+	state := "state"
+	now := func() time.Time { return time.Now() }
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	httpServer, s := newTestServer(ctx, t, func(c *Config) {
+		c.Now = now
+	})
+	defer httpServer.Close()
+
+	p, err := oidc.NewProvider(ctx, httpServer.URL)
+	if err != nil {
+		t.Fatalf("failed to get provider: %v", err)
+	}
+
+	var oauth2Client oauth2Client
+
+	oauth2Client.server = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/callback" {
+			// User is visiting app first time. Redirect to dex.
+			http.Redirect(w, r, oauth2Client.config.AuthCodeURL(state), http.StatusSeeOther)
+			return
+		}
+
+		// User is at '/callback' so they were just redirected _from_ dex.
+		q := r.URL.Query()
+
+		if errType := q.Get("error"); errType != "" {
+			if desc := q.Get("error_description"); desc != "" {
+				t.Errorf("got error from server %s: %s", errType, desc)
+			} else {
+				t.Errorf("got error from server %s", errType)
+			}
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+
+		// Grab code, exchange for token.
+		if code := q.Get("code"); code != "" {
+			token, err := oauth2Client.config.Exchange(ctx, code)
+			if err != nil {
+				t.Errorf("failed to exchange code for token: %v", err)
+				return
+			}
+			oauth2Client.token = token
+		}
+
+		// Ensure state matches.
+		if gotState := q.Get("state"); gotState != state {
+			t.Errorf("state did not match, want=%q got=%q", state, gotState)
+		}
+		w.WriteHeader(http.StatusOK)
+		return
+	}))
+	defer oauth2Client.server.Close()
+
+	// Register the client above with dex.
+	redirectURL := oauth2Client.server.URL + "/callback"
+	client := storage.Client{
+		ID:           "testclient",
+		Secret:       "testclientsecret",
+		RedirectURIs: []string{redirectURL},
+	}
+	if err := s.storage.CreateClient(client); err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	oauth2Client.config = &oauth2.Config{
+		ClientID:     client.ID,
+		ClientSecret: client.Secret,
+		Endpoint:     p.Endpoint(),
+		Scopes:       []string{oidc.ScopeOpenID, "email", "offline_access"},
+		RedirectURL:  redirectURL,
+	}
+
+	if _, err = http.Get(oauth2Client.server.URL + "/login"); err != nil {
+		t.Fatalf("get failed: %v", err)
+	}
+
+	tok := &oauth2.Token{
+		RefreshToken: oauth2Client.token.RefreshToken,
+		Expiry:       time.Now().Add(-time.Hour),
+	}
+
+	// Login in again to recieve a new token.
+	if _, err = http.Get(oauth2Client.server.URL + "/login"); err != nil {
+		t.Fatalf("get failed: %v", err)
+	}
+
+	// try to refresh expired token with old refresh token.
+	newToken, err := oauth2Client.config.TokenSource(ctx, tok).Token()
+	if newToken != nil {
+		t.Errorf("Token refreshed with invalid refresh token.")
+	}
+}

storage/conformance/conformance.go

@@ -47,6 +47,7 @@ func RunTests(t *testing.T, newStorage func() storage.Storage) {
 		{"RefreshTokenCRUD", testRefreshTokenCRUD},
 		{"PasswordCRUD", testPasswordCRUD},
 		{"KeysCRUD", testKeysCRUD},
+		{"OfflineSessionCRUD", testOfflineSessionCRUD},
 		{"GarbageCollection", testGC},
 		{"TimezoneSupport", testTimezones},
 	})
@@ -340,6 +341,60 @@ func testPasswordCRUD(t *testing.T, s storage.Storage) {
 
 }
 
+func testOfflineSessionCRUD(t *testing.T, s storage.Storage) {
+	session := storage.OfflineSessions{
+		UserID:  "User",
+		ConnID:  "Conn",
+		Refresh: make(map[string]*storage.RefreshTokenRef),
+	}
+
+	// Creating an OfflineSession with an empty Refresh list to ensure that
+	// an empty map is translated as expected by the storage.
+	if err := s.CreateOfflineSessions(session); err != nil {
+		t.Fatalf("create offline session: %v", err)
+	}
+
+	getAndCompare := func(userID string, connID string, want storage.OfflineSessions) {
+		gr, err := s.GetOfflineSessions(userID, connID)
+		if err != nil {
+			t.Errorf("get offline session: %v", err)
+			return
+		}
+		if diff := pretty.Compare(want, gr); diff != "" {
+			t.Errorf("offline session retrieved from storage did not match: %s", diff)
+		}
+	}
+
+	getAndCompare("User", "Conn", session)
+
+	id := storage.NewID()
+	tokenRef := storage.RefreshTokenRef{
+		ID:        id,
+		ClientID:  "client_id",
+		CreatedAt: time.Now().UTC().Round(time.Millisecond),
+		LastUsed:  time.Now().UTC().Round(time.Millisecond),
+	}
+	session.Refresh[tokenRef.ClientID] = &tokenRef
+
+	if err := s.UpdateOfflineSessions(session.UserID, session.ConnID, func(old storage.OfflineSessions) (storage.OfflineSessions, error) {
+		old.Refresh[tokenRef.ClientID] = &tokenRef
+		return old, nil
+	}); err != nil {
+		t.Fatalf("failed to update offline session: %v", err)
+	}
+
+	getAndCompare("User", "Conn", session)
+
+	if err := s.DeleteOfflineSessions(session.UserID, session.ConnID); err != nil {
+		t.Fatalf("failed to delete offline session: %v", err)
+	}
+
+	if _, err := s.GetOfflineSessions(session.UserID, session.ConnID); err != storage.ErrNotFound {
+		t.Errorf("after deleting offline session expected storage.ErrNotFound, got %v", err)
+	}
+
+}
+
 func testKeysCRUD(t *testing.T, s storage.Storage) {
 	updateAndCompare := func(k storage.Keys) {
 		err := s.UpdateKeys(func(oldKeys storage.Keys) (storage.Keys, error) {

storage/kubernetes/client.go

@@ -58,6 +58,12 @@ func (c *client) idToName(s string) string {
 	return idToName(s, c.hash)
 }
 
+// offlineTokenName maps two arbitrary IDs, to a single Kubernetes object name.
+// This is used when more than one field is used to uniquely identify the object.
+func (c *client) offlineTokenName(userID string, connID string) string {
+	return offlineTokenName(userID, connID, c.hash)
+}
+
 // Kubernetes names must match the regexp '[a-z0-9]([-a-z0-9]*[a-z0-9])?'.
 var encoding = base32.NewEncoding("abcdefghijklmnopqrstuvwxyz234567")
 
@@ -65,6 +71,12 @@ func idToName(s string, h func() hash.Hash) string {
 	return strings.TrimRight(encoding.EncodeToString(h().Sum([]byte(s))), "=")
 }
 
+func offlineTokenName(userID string, connID string, h func() hash.Hash) string {
+	h().Write([]byte(userID))
+	h().Write([]byte(connID))
+	return strings.TrimRight(encoding.EncodeToString(h().Sum(nil)), "=")
+}
+
 func (c *client) urlFor(apiVersion, namespace, resource, name string) string {
 	basePath := "apis/"
 	if apiVersion == "v1" {

storage/kubernetes/storage.go

@@ -21,6 +21,7 @@ const (
 	kindRefreshToken    = "RefreshToken"
 	kindKeys            = "SigningKey"
 	kindPassword        = "Password"
+	kindOfflineSessions = "OfflineSessions"
 )
 
 const (
@@ -30,6 +31,7 @@ const (
 	resourceRefreshToken    = "refreshtokens"
 	resourceKeys            = "signingkeies" // Kubernetes attempts to pluralize.
 	resourcePassword        = "passwords"
+	resourceOfflineSessions = "offlinesessions"
 )
 
 // Config values for the Kubernetes storage type.
@@ -156,6 +158,10 @@ func (cli *client) CreateRefresh(r storage.RefreshToken) error {
 	return cli.post(resourceRefreshToken, cli.fromStorageRefreshToken(r))
 }
 
+func (cli *client) CreateOfflineSessions(o storage.OfflineSessions) error {
+	return cli.post(resourceOfflineSessions, cli.fromStorageOfflineSessions(o))
+}
+
 func (cli *client) GetAuthRequest(id string) (storage.AuthRequest, error) {
 	var req AuthRequest
 	if err := cli.get(resourceAuthRequest, id, &req); err != nil {
@@ -235,6 +241,25 @@ func (cli *client) getRefreshToken(id string) (r RefreshToken, err error) {
 	return
 }
 
+func (cli *client) GetOfflineSessions(userID string, connID string) (storage.OfflineSessions, error) {
+	o, err := cli.getOfflineSessions(userID, connID)
+	if err != nil {
+		return storage.OfflineSessions{}, err
+	}
+	return toStorageOfflineSessions(o), nil
+}
+
+func (cli *client) getOfflineSessions(userID string, connID string) (o OfflineSessions, err error) {
+	name := cli.offlineTokenName(userID, connID)
+	if err = cli.get(resourceOfflineSessions, name, &o); err != nil {
+		return OfflineSessions{}, err
+	}
+	if userID != o.UserID || connID != o.ConnID {
+		return OfflineSessions{}, fmt.Errorf("get offline session: wrong session retrieved")
+	}
+	return o, nil
+}
+
 func (cli *client) ListClients() ([]storage.Client, error) {
 	return nil, errors.New("not implemented")
 }
@@ -292,6 +317,15 @@ func (cli *client) DeletePassword(email string) error {
 	return cli.delete(resourcePassword, p.ObjectMeta.Name)
 }
 
+func (cli *client) DeleteOfflineSessions(userID string, connID string) error {
+	// Check for hash collition.
+	o, err := cli.getOfflineSessions(userID, connID)
+	if err != nil {
+		return err
+	}
+	return cli.delete(resourceOfflineSessions, o.ObjectMeta.Name)
+}
+
 func (cli *client) UpdateRefreshToken(id string, updater func(old storage.RefreshToken) (storage.RefreshToken, error)) error {
 	r, err := cli.getRefreshToken(id)
 	if err != nil {
@@ -342,6 +376,22 @@ func (cli *client) UpdatePassword(email string, updater func(old storage.Passwor
 	return cli.put(resourcePassword, p.ObjectMeta.Name, newPassword)
 }
 
+func (cli *client) UpdateOfflineSessions(userID string, connID string, updater func(old storage.OfflineSessions) (storage.OfflineSessions, error)) error {
+	o, err := cli.getOfflineSessions(userID, connID)
+	if err != nil {
+		return err
+	}
+
+	updated, err := updater(toStorageOfflineSessions(o))
+	if err != nil {
+		return err
+	}
+
+	newOfflineSessions := cli.fromStorageOfflineSessions(updated)
+	newOfflineSessions.ObjectMeta = o.ObjectMeta
+	return cli.put(resourceOfflineSessions, o.ObjectMeta.Name, newOfflineSessions)
+}
+
 func (cli *client) UpdateKeys(updater func(old storage.Keys) (storage.Keys, error)) error {
 	firstUpdate := false
 	var keys Keys

storage/kubernetes/types.go

@@ -66,6 +66,14 @@ var thirdPartyResources = []k8sapi.ThirdPartyResource{
 		Description: "Passwords managed by the OIDC server.",
 		Versions:    []k8sapi.APIVersion{{Name: "v1"}},
 	},
+	{
+		ObjectMeta: k8sapi.ObjectMeta{
+			Name: "offline-sessions.oidc.coreos.com",
+		},
+		TypeMeta:    tprMeta,
+		Description: "User sessions with an active refresh token.",
+		Versions:    []k8sapi.APIVersion{{Name: "v1"}},
+	},
 }
 
 // There will only ever be a single keys resource. Maintain this by setting a
@@ -465,3 +473,38 @@ func toStorageKeys(keys Keys) storage.Keys {
 		NextRotation:     keys.NextRotation,
 	}
 }
+
+// OfflineSessions is a mirrored struct from storage with JSON struct tags and Kubernetes
+// type metadata.
+type OfflineSessions struct {
+	k8sapi.TypeMeta   `json:",inline"`
+	k8sapi.ObjectMeta `json:"metadata,omitempty"`
+
+	UserID  string                              `json:"userID,omitempty"`
+	ConnID  string                              `json:"connID,omitempty"`
+	Refresh map[string]*storage.RefreshTokenRef `json:"refresh,omitempty"`
+}
+
+func (cli *client) fromStorageOfflineSessions(o storage.OfflineSessions) OfflineSessions {
+	return OfflineSessions{
+		TypeMeta: k8sapi.TypeMeta{
+			Kind:       kindOfflineSessions,
+			APIVersion: cli.apiVersion,
+		},
+		ObjectMeta: k8sapi.ObjectMeta{
+			Name:      cli.offlineTokenName(o.UserID, o.ConnID),
+			Namespace: cli.namespace,
+		},
+		UserID:  o.UserID,
+		ConnID:  o.ConnID,
+		Refresh: o.Refresh,
+	}
+}
+
+func toStorageOfflineSessions(o OfflineSessions) storage.OfflineSessions {
+	return storage.OfflineSessions{
+		UserID:  o.UserID,
+		ConnID:  o.ConnID,
+		Refresh: o.Refresh,
+	}
+}

storage/memory/memory.go

@@ -18,6 +18,7 @@ func New(logger logrus.FieldLogger) storage.Storage {
 		refreshTokens:   make(map[string]storage.RefreshToken),
 		authReqs:        make(map[string]storage.AuthRequest),
 		passwords:       make(map[string]storage.Password),
+		offlineSessions: make(map[offlineSessionID]storage.OfflineSessions),
 		logger:          logger,
 	}
 }
@@ -42,12 +43,18 @@ type memStorage struct {
 	refreshTokens   map[string]storage.RefreshToken
 	authReqs        map[string]storage.AuthRequest
 	passwords       map[string]storage.Password
+	offlineSessions map[offlineSessionID]storage.OfflineSessions
 
 	keys storage.Keys
 
 	logger logrus.FieldLogger
 }
 
+type offlineSessionID struct {
+	userID string
+	connID string
+}
+
 func (s *memStorage) tx(f func()) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -130,6 +137,32 @@ func (s *memStorage) CreatePassword(p storage.Password) (err error) {
 	return
 }
 
+func (s *memStorage) CreateOfflineSessions(o storage.OfflineSessions) (err error) {
+	id := offlineSessionID{
+		userID: o.UserID,
+		connID: o.ConnID,
+	}
+	s.tx(func() {
+		if _, ok := s.offlineSessions[id]; ok {
+			err = storage.ErrAlreadyExists
+		} else {
+			s.offlineSessions[id] = o
+		}
+	})
+	return
+}
+
+func (s *memStorage) GetAuthCode(id string) (c storage.AuthCode, err error) {
+	s.tx(func() {
+		var ok bool
+		if c, ok = s.authCodes[id]; !ok {
+			err = storage.ErrNotFound
+			return
+		}
+	})
+	return
+}
+
 func (s *memStorage) GetPassword(email string) (p storage.Password, err error) {
 	email = strings.ToLower(email)
 	s.tx(func() {
@@ -156,10 +189,10 @@ func (s *memStorage) GetKeys() (keys storage.Keys, err error) {
 	return
 }
 
-func (s *memStorage) GetRefresh(token string) (tok storage.RefreshToken, err error) {
+func (s *memStorage) GetRefresh(id string) (tok storage.RefreshToken, err error) {
 	s.tx(func() {
 		var ok bool
-		if tok, ok = s.refreshTokens[token]; !ok {
+		if tok, ok = s.refreshTokens[id]; !ok {
 			err = storage.ErrNotFound
 			return
 		}
@@ -178,6 +211,21 @@ func (s *memStorage) GetAuthRequest(id string) (req storage.AuthRequest, err err
 	return
 }
 
+func (s *memStorage) GetOfflineSessions(userID string, connID string) (o storage.OfflineSessions, err error) {
+	id := offlineSessionID{
+		userID: userID,
+		connID: connID,
+	}
+	s.tx(func() {
+		var ok bool
+		if o, ok = s.offlineSessions[id]; !ok {
+			err = storage.ErrNotFound
+			return
+		}
+	})
+	return
+}
+
 func (s *memStorage) ListClients() (clients []storage.Client, err error) {
 	s.tx(func() {
 		for _, client := range s.clients {
@@ -228,13 +276,13 @@ func (s *memStorage) DeleteClient(id string) (err error) {
 	return
 }
 
-func (s *memStorage) DeleteRefresh(token string) (err error) {
+func (s *memStorage) DeleteRefresh(id string) (err error) {
 	s.tx(func() {
-		if _, ok := s.refreshTokens[token]; !ok {
+		if _, ok := s.refreshTokens[id]; !ok {
 			err = storage.ErrNotFound
 			return
 		}
-		delete(s.refreshTokens, token)
+		delete(s.refreshTokens, id)
 	})
 	return
 }
@@ -261,13 +309,17 @@ func (s *memStorage) DeleteAuthRequest(id string) (err error) {
 	return
 }
 
-func (s *memStorage) GetAuthCode(id string) (c storage.AuthCode, err error) {
+func (s *memStorage) DeleteOfflineSessions(userID string, connID string) (err error) {
+	id := offlineSessionID{
+		userID: userID,
+		connID: connID,
+	}
 	s.tx(func() {
-		var ok bool
-		if c, ok = s.authCodes[id]; !ok {
+		if _, ok := s.offlineSessions[id]; !ok {
 			err = storage.ErrNotFound
 			return
 		}
+		delete(s.offlineSessions, id)
 	})
 	return
 }
@@ -338,3 +390,21 @@ func (s *memStorage) UpdateRefreshToken(id string, updater func(p storage.Refres
 	})
 	return
 }
+
+func (s *memStorage) UpdateOfflineSessions(userID string, connID string, updater func(o storage.OfflineSessions) (storage.OfflineSessions, error)) (err error) {
+	id := offlineSessionID{
+		userID: userID,
+		connID: connID,
+	}
+	s.tx(func() {
+		r, ok := s.offlineSessions[id]
+		if !ok {
+			err = storage.ErrNotFound
+			return
+		}
+		if r, err = updater(r); err == nil {
+			s.offlineSessions[id] = r
+		}
+	})
+	return
+}

storage/sql/crud.go

@@ -624,6 +624,75 @@ func scanPassword(s scanner) (p storage.Password, err error) {
 	return p, nil
 }
 
+func (c *conn) CreateOfflineSessions(s storage.OfflineSessions) error {
+	_, err := c.Exec(`
+		insert into offline_session (
+			user_id, conn_id, refresh
+		)
+		values (
+			$1, $2, $3
+		);
+	`,
+		s.UserID, s.ConnID, encoder(s.Refresh),
+	)
+	if err != nil {
+		return fmt.Errorf("insert offline session: %v", err)
+	}
+	return nil
+}
+
+func (c *conn) UpdateOfflineSessions(userID string, connID string, updater func(s storage.OfflineSessions) (storage.OfflineSessions, error)) error {
+	return c.ExecTx(func(tx *trans) error {
+		s, err := getOfflineSessions(tx, userID, connID)
+		if err != nil {
+			return err
+		}
+
+		newSession, err := updater(s)
+		if err != nil {
+			return err
+		}
+		_, err = tx.Exec(`
+			update offline_session
+			set
+				refresh = $1
+			where user_id = $2 AND conn_id = $3;
+		`,
+			encoder(newSession.Refresh), s.UserID, s.ConnID,
+		)
+		if err != nil {
+			return fmt.Errorf("update offline session: %v", err)
+		}
+		return nil
+	})
+}
+
+func (c *conn) GetOfflineSessions(userID string, connID string) (storage.OfflineSessions, error) {
+	return getOfflineSessions(c, userID, connID)
+}
+
+func getOfflineSessions(q querier, userID string, connID string) (storage.OfflineSessions, error) {
+	return scanOfflineSessions(q.QueryRow(`
+		select
+			user_id, conn_id, refresh
+		from offline_session
+		where user_id = $1 AND conn_id = $2;
+		`, userID, connID))
+}
+
+func scanOfflineSessions(s scanner) (o storage.OfflineSessions, err error) {
+	err = s.Scan(
+		&o.UserID, &o.ConnID, decoder(&o.Refresh),
+	)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return o, storage.ErrNotFound
+		}
+		return o, fmt.Errorf("select offline session: %v", err)
+	}
+	return o, nil
+}
+
 func (c *conn) DeleteAuthRequest(id string) error { return c.delete("auth_request", "id", id) }
 func (c *conn) DeleteAuthCode(id string) error    { return c.delete("auth_code", "id", id) }
 func (c *conn) DeleteClient(id string) error      { return c.delete("client", "id", id) }
@@ -632,6 +701,24 @@ func (c *conn) DeletePassword(email string) error {
 	return c.delete("password", "email", strings.ToLower(email))
 }
 
+func (c *conn) DeleteOfflineSessions(userID string, connID string) error {
+	result, err := c.Exec(`delete from offline_session where user_id = $1 AND conn_id = $2`, userID, connID)
+	if err != nil {
+		return fmt.Errorf("delete offline_session: user_id = %s, conn_id = %s", userID, connID)
+	}
+
+	// For now mandate that the driver implements RowsAffected. If we ever need to support
+	// a driver that doesn't implement this, we can run this in a transaction with a get beforehand.
+	n, err := result.RowsAffected()
+	if err != nil {
+		return fmt.Errorf("rows affected: %v", err)
+	}
+	if n < 1 {
+		return storage.ErrNotFound
+	}
+	return nil
+}
+
 // Do NOT call directly. Does not escape table.
 func (c *conn) delete(table, field, id string) error {
 	result, err := c.Exec(`delete from `+table+` where `+field+` = $1`, id)

storage/sql/migrate.go

@@ -153,6 +153,7 @@ var migrations = []migration{
 				signing_key_pub bytea not null,   -- JSON object
 				next_rotation timestamptz not null
 			);
+
 		`,
 	},
 	{
@@ -165,4 +166,14 @@ var migrations = []migration{
 				add column last_used timestamptz not null default '0001-01-01 00:00:00 UTC';
 		`,
 	},
+	{
+		stmt: `
+			create table offline_session (
+				user_id text not null,
+				conn_id text not null,
+				refresh bytea not null,
+				PRIMARY KEY (user_id, conn_id)
+			);
+		`,
+	},
 }

storage/storage.go

@@ -52,6 +52,7 @@ type Storage interface {
 	CreateAuthCode(c AuthCode) error
 	CreateRefresh(r RefreshToken) error
 	CreatePassword(p Password) error
+	CreateOfflineSessions(s OfflineSessions) error
 
 	// TODO(ericchiang): return (T, bool, error) so we can indicate not found
 	// requests that way instead of using ErrNotFound.
@@ -61,6 +62,7 @@ type Storage interface {
 	GetKeys() (Keys, error)
 	GetRefresh(id string) (RefreshToken, error)
 	GetPassword(email string) (Password, error)
+	GetOfflineSessions(userID string, connID string) (OfflineSessions, error)
 
 	ListClients() ([]Client, error)
 	ListRefreshTokens() ([]RefreshToken, error)
@@ -72,6 +74,7 @@ type Storage interface {
 	DeleteClient(id string) error
 	DeleteRefresh(id string) error
 	DeletePassword(email string) error
+	DeleteOfflineSessions(userID string, connID string) error
 
 	// Update methods take a function for updating an object then performs that update within
 	// a transaction. "updater" functions may be called multiple times by a single update call.
@@ -92,6 +95,7 @@ type Storage interface {
 	UpdateAuthRequest(id string, updater func(a AuthRequest) (AuthRequest, error)) error
 	UpdateRefreshToken(id string, updater func(r RefreshToken) (RefreshToken, error)) error
 	UpdatePassword(email string, updater func(p Password) (Password, error)) error
+	UpdateOfflineSessions(userID string, connID string, updater func(s OfflineSessions) (OfflineSessions, error)) error
 
 	// GarbageCollect deletes all expired AuthCodes and AuthRequests.
 	GarbageCollect(now time.Time) (GCResult, error)
@@ -241,6 +245,30 @@ type RefreshToken struct {
 	Nonce string
 }
 
+// RefreshTokenRef is a reference object that contains metadata about refresh tokens.
+type RefreshTokenRef struct {
+	ID string
+
+	// Client the refresh token is valid for.
+	ClientID string
+
+	CreatedAt time.Time
+	LastUsed  time.Time
+}
+
+// OfflineSessions objects are sessions pertaining to users with refresh tokens.
+type OfflineSessions struct {
+	// UserID of an end user who has logged in to the server.
+	UserID string
+
+	// The ID of the connector used to login the user.
+	ConnID string
+
+	// Refresh is a hash table of refresh token reference objects
+	// indexed by the ClientID of the refresh token.
+	Refresh map[string]*RefreshTokenRef
+}
+
 // Password is an email to password mapping managed by the storage.
 type Password struct {
 	// Email and identifying name of the password. Emails are assumed to be valid and