server: update refresh tokens instead of deleting and creating another

The server implements a strategy called "Refresh Token Rotation" to
ensure refresh tokens can only be claimed once.

ref: https://tools.ietf.org/html/rfc6819#section-5.2.2.3

Previously "refresh_token" values in token responses where just the
ID of the internal refresh object. To implement rotation, when a
client redeemed a refresh token, the object would be deleted, a new
one created, and the new ID returned as the new "refresh_token".

However, this means there was no consistent ID for refresh tokens
internally, making things like foreign keys very hard to implement.
This is problematic for revocation features like showing all the
refresh tokens a user or client has out.

This PR updates the "refresh_token" to be an encoded protobuf
message, which holds the internal ID and a nonce. When a refresh
token is used, the nonce is updated to prevent reuse, but the ID
remains the same. Additionally it adds the timestamp of each
token's last use.

Makefile

@@ -55,7 +55,7 @@ fmt:
 	@go fmt $(shell go list ./... | grep -v '/vendor/')
 
 lint:
-	@for package in $(shell go list ./... | grep -v '/vendor/' | grep -v '/api'); do \
+	@for package in $(shell go list ./... | grep -v '/vendor/' | grep -v '/api' | grep -v '/server/internal'); do \
       golint -set_exit_status $$package $$i || exit 1; \
 	done
 
@@ -81,12 +81,15 @@ aci: clean-release _output/bin/dex _output/images/library-alpine-3.4.aci
 docker-image: clean-release _output/bin/dex
 	@sudo docker build -t $(DOCKER_IMAGE) .
 
-.PHONY: grpc
-grpc: api/api.pb.go
+.PHONY: proto
+proto: api/api.pb.go server/internal/types.pb.go
 
 api/api.pb.go: api/api.proto bin/protoc bin/protoc-gen-go
 	@protoc --go_out=plugins=grpc:. api/*.proto
 
+server/internal/types.pb.go: server/internal/types.proto bin/protoc bin/protoc-gen-go
+	@protoc --go_out=. server/internal/*.proto
+
 bin/protoc: scripts/get-protoc
 	@./scripts/get-protoc bin/protoc
 

server/handlers.go

@@ -2,6 +2,7 @@ package server
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -16,6 +17,7 @@ import (
 	jose "gopkg.in/square/go-jose.v2"
 
 	"github.com/coreos/dex/connector"
+	"github.com/coreos/dex/server/internal"
 	"github.com/coreos/dex/storage"
 )
 
@@ -645,20 +647,32 @@ func (s *Server) handleAuthCode(w http.ResponseWriter, r *http.Request, client s
 	var refreshToken string
 	if reqRefresh {
 		refresh := storage.RefreshToken{
-			RefreshToken:  storage.NewID(),
+			ID:            storage.NewID(),
+			Token:         storage.NewID(),
 			ClientID:      authCode.ClientID,
 			ConnectorID:   authCode.ConnectorID,
 			Scopes:        authCode.Scopes,
 			Claims:        authCode.Claims,
 			Nonce:         authCode.Nonce,
 			ConnectorData: authCode.ConnectorData,
+			CreatedAt:     s.now(),
+			LastUsed:      s.now(),
 		}
+		token := &internal.RefreshToken{
+			RefreshId: refresh.ID,
+			Token:     refresh.Token,
+		}
+		if refreshToken, err = internal.Marshal(token); err != nil {
+			s.logger.Errorf("failed to marshal refresh token: %v", err)
+			s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
+			return
+		}
+
 		if err := s.storage.CreateRefresh(refresh); err != nil {
 			s.logger.Errorf("failed to create refresh token: %v", err)
 			s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 			return
 		}
-		refreshToken = refresh.RefreshToken
 	}
 	s.writeAccessToken(w, idToken, refreshToken, expiry)
 }
@@ -672,16 +686,37 @@ func (s *Server) handleRefreshToken(w http.ResponseWriter, r *http.Request, clie
 		return
 	}
 
-	refresh, err := s.storage.GetRefresh(code)
-	if err != nil || refresh.ClientID != client.ID {
-		if err != storage.ErrNotFound {
-			s.logger.Errorf("failed to get auth code: %v", err)
-			s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
-		} else {
+	token := new(internal.RefreshToken)
+	if err := internal.Unmarshal(code, token); err != nil {
+		// For backward compatibility, assume the refresh_token is a raw refresh token ID
+		// if it fails to decode.
+		//
+		// Because refresh_token values that aren't unmarshable were generated by servers
+		// that don't have a Token value, we'll still reject any attempts to claim a
+		// refresh_token twice.
+		token = &internal.RefreshToken{RefreshId: code, Token: ""}
+	}
+
+	refresh, err := s.storage.GetRefresh(token.RefreshId)
+	if err != nil {
+		s.logger.Errorf("failed to get refresh token: %v", err)
+		if err == storage.ErrNotFound {
 			s.tokenErrHelper(w, errInvalidRequest, "Refresh token is invalid or has already been claimed by another client.", http.StatusBadRequest)
+		} else {
+			s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 		}
 		return
 	}
+	if refresh.ClientID != client.ID {
+		s.logger.Errorf("client %s trying to claim token for client %s", client.ID, refresh.ClientID)
+		s.tokenErrHelper(w, errInvalidRequest, "Refresh token is invalid or has already been claimed by another client.", http.StatusBadRequest)
+		return
+	}
+	if refresh.Token != token.Token {
+		s.logger.Errorf("refresh token with id %s claimed twice", refresh.ID)
+		s.tokenErrHelper(w, errInvalidRequest, "Refresh token is invalid or has already been claimed by another client.", http.StatusBadRequest)
+		return
+	}
 
 	// Per the OAuth2 spec, if the client has omitted the scopes, default to the original
 	// authorized scopes.
@@ -720,59 +755,78 @@ func (s *Server) handleRefreshToken(w http.ResponseWriter, r *http.Request, clie
 		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 		return
 	}
+	ident := connector.Identity{
+		UserID:        refresh.Claims.UserID,
+		Username:      refresh.Claims.Username,
+		Email:         refresh.Claims.Email,
+		EmailVerified: refresh.Claims.EmailVerified,
+		Groups:        refresh.Claims.Groups,
+		ConnectorData: refresh.ConnectorData,
+	}
 
 	// Can the connector refresh the identity? If so, attempt to refresh the data
 	// in the connector.
 	//
 	// TODO(ericchiang): We may want a strict mode where connectors that don't implement
 	// this interface can't perform refreshing.
 	if refreshConn, ok := conn.Connector.(connector.RefreshConnector); ok {
-		ident := connector.Identity{
-			UserID:        refresh.Claims.UserID,
-			Username:      refresh.Claims.Username,
-			Email:         refresh.Claims.Email,
-			EmailVerified: refresh.Claims.EmailVerified,
-			Groups:        refresh.Claims.Groups,
-			ConnectorData: refresh.ConnectorData,
-		}
-		ident, err := refreshConn.Refresh(r.Context(), parseScopes(scopes), ident)
+		newIdent, err := refreshConn.Refresh(r.Context(), parseScopes(scopes), ident)
 		if err != nil {
 			s.logger.Errorf("failed to refresh identity: %v", err)
 			s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 			return
 		}
+		ident = newIdent
+	}
 
-		// Update the claims of the refresh token.
-		//
-		// UserID intentionally ignored for now.
-		refresh.Claims.Username = ident.Username
-		refresh.Claims.Email = ident.Email
-		refresh.Claims.EmailVerified = ident.EmailVerified
-		refresh.Claims.Groups = ident.Groups
-		refresh.ConnectorData = ident.ConnectorData
+	claims := storage.Claims{
+		UserID:        ident.UserID,
+		Username:      ident.Username,
+		Email:         ident.Email,
+		EmailVerified: ident.EmailVerified,
+		Groups:        ident.Groups,
 	}
 
-	idToken, expiry, err := s.newIDToken(client.ID, refresh.Claims, scopes, refresh.Nonce)
+	idToken, expiry, err := s.newIDToken(client.ID, claims, scopes, refresh.Nonce)
 	if err != nil {
 		s.logger.Errorf("failed to create ID token: %v", err)
 		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 		return
 	}
 
-	// Refresh tokens are claimed exactly once. Delete the current token and
-	// create a new one.
-	if err := s.storage.DeleteRefresh(code); err != nil {
-		s.logger.Errorf("failed to delete auth code: %v", err)
+	newToken := &internal.RefreshToken{
+		RefreshId: refresh.ID,
+		Token:     storage.NewID(),
+	}
+	rawNewToken, err := internal.Marshal(newToken)
+	if err != nil {
+		s.logger.Errorf("failed to marshal refresh token: %v", err)
 		s.tokenErrHelper(w, errServerError, "", http.StatusInternalServerError)
 		return
 	}
-	refresh.RefreshToken = storage.NewID()
-	if err := s.storage.CreateRefresh(refresh); err != nil {
-		s.logger.Errorf("failed to create refresh token: %v", err)
+
+	updater := func(old storage.RefreshToken) (storage.RefreshToken, error) {
+		if old.Token != refresh.Token {
+			return old, errors.New("refresh token claimed twice")
+		}
+		old.Token = newToken.Token
+		// Update the claims of the refresh token.
+		//
+		// UserID intentionally ignored for now.
+		old.Claims.Username = ident.Username
+		old.Claims.Email = ident.Email
+		old.Claims.EmailVerified = ident.EmailVerified
+		old.Claims.Groups = ident.Groups
+		old.ConnectorData = ident.ConnectorData
+		old.LastUsed = s.now()
+		return old, nil
+	}
+	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, refresh.RefreshToken, expiry)
+	s.writeAccessToken(w, idToken, rawNewToken, expiry)
 }
 
 func (s *Server) writeAccessToken(w http.ResponseWriter, idToken, refreshToken string, expiry time.Time) {

server/internal/codec.go

@@ -0,0 +1,25 @@
+package internal
+
+import (
+	"encoding/base64"
+
+	"github.com/golang/protobuf/proto"
+)
+
+// Marshal converts a protobuf message to a URL legal string.
+func Marshal(message proto.Message) (string, error) {
+	data, err := proto.Marshal(message)
+	if err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(data), nil
+}
+
+// Unmarshal decodes a protobuf message.
+func Unmarshal(s string, message proto.Message) error {
+	data, err := base64.RawURLEncoding.DecodeString(s)
+	if err != nil {
+		return err
+	}
+	return proto.Unmarshal(data, message)
+}

server/internal/types.proto

@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+// Package internal holds protobuf types used by the server
+package internal;
+
+// RefreshToken is a message that holds refresh token data used by dex.
+message RefreshToken {
+  string refresh_id = 1;
+  string token = 2;
+}

server/server_test.go

@@ -237,6 +237,10 @@ func TestOAuth2CodeFlow(t *testing.T) {
 				if token.RefreshToken == newToken.RefreshToken {
 					return fmt.Errorf("old refresh token was the same as the new token %q", token.RefreshToken)
 				}
+
+				if _, err := config.TokenSource(ctx, token).Token(); err == nil {
+					return errors.New("was able to redeem the same refresh token twice")
+				}
 				return nil
 			},
 		},