Cache access tokens client side

auth/api/iam/api.go

@@ -22,8 +22,10 @@ import (
 	"bytes"
 	"context"
 	"crypto"
+	"crypto/sha256"
 	"embed"
 	"encoding/base64"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -72,6 +74,10 @@ type httpRequestContextKey struct{}
 // TODO: Might want to make this configurable at some point
 const accessTokenValidity = 15 * time.Minute
 
+// accessTokenCacheOffset is used to reduce the ttl of the access token to ensure it is still valid when the client receives it.
+// this to offset clock skew and roundtrip times
+const accessTokenCacheOffset = 30 * time.Second
+
 // cacheControlMaxAgeURLs holds API endpoints that should have a max-age cache control header set.
 var cacheControlMaxAgeURLs = []string{
 	"/oauth2/:subjectID/presentation_definition",
@@ -722,6 +728,19 @@ func (r Wrapper) RequestServiceAccessToken(ctx context.Context, request RequestS
 		return nil, err
 	}
 
+	tokenCache := r.accessTokenCache()
+	cacheKey := accessTokenRequestCacheKey(request)
+
+	// try to retrieve token from cache
+	tokenResult := new(TokenResponse)
+	err = tokenCache.Get(cacheKey, tokenResult)
+	if err == nil {
+		return RequestServiceAccessToken200JSONResponse(*tokenResult), nil
+	} else if !errors.Is(err, storage.ErrNotFound) {
+		// only log error, don't fail
+		log.Logger().WithError(err).Warnf("Failed to retrieve access token from cache: %s", err.Error())
+	}
+
 	var credentials []VerifiableCredential
 	if request.Body.Credentials != nil {
 		credentials = *request.Body.Credentials
@@ -732,11 +751,22 @@ func (r Wrapper) RequestServiceAccessToken(ctx context.Context, request RequestS
 		useDPoP = false
 	}
 	clientID := r.subjectToBaseURL(request.SubjectID)
-	tokenResult, err := r.auth.IAMClient().RequestRFC021AccessToken(ctx, clientID.String(), request.SubjectID, request.Body.AuthorizationServer, request.Body.Scope, useDPoP, credentials)
+	tokenResult, err = r.auth.IAMClient().RequestRFC021AccessToken(ctx, clientID.String(), request.SubjectID, request.Body.AuthorizationServer, request.Body.Scope, useDPoP, credentials)
 	if err != nil {
 		// this can be an internal server error, a 400 oauth error or a 412 precondition failed if the wallet does not contain the required credentials
 		return nil, err
 	}
+	ttl := accessTokenValidity
+	if tokenResult.ExpiresIn != nil {
+		ttl = time.Second * time.Duration(*tokenResult.ExpiresIn)
+	}
+	// we reduce the ttl by accessTokenCacheOffset to make sure the token is expired when the cache expires
+	ttl -= accessTokenCacheOffset
+	err = tokenCache.Put(cacheKey, tokenResult, storage.WithTTL(ttl))
+	if err != nil {
+		// only log error, don't fail
+		log.Logger().WithError(err).Warnf("Failed to cache access token: %s", err.Error())
+	}
 	return RequestServiceAccessToken200JSONResponse(*tokenResult), nil
 }
 
@@ -897,6 +927,12 @@ func (r Wrapper) accessTokenServerStore() storage.SessionStore {
 	return r.storageEngine.GetSessionDatabase().GetStore(accessTokenValidity, "serveraccesstoken")
 }
 
+// accessTokenClientStore is used by the client to cache access tokens
+func (r Wrapper) accessTokenCache() storage.SessionStore {
+	// we use a slightly reduced validity to prevent the cache from being used after the token has expired
+	return r.storageEngine.GetSessionDatabase().GetStore(accessTokenValidity-accessTokenCacheOffset, "accesstokencache")
+}
+
 // accessTokenServerStore is used by the Auth server to store issued access tokens
 func (r Wrapper) authzRequestObjectStore() storage.SessionStore {
 	return r.storageEngine.GetSessionDatabase().GetStore(accessTokenValidity, oauthRequestObjectKey...)
@@ -946,3 +982,11 @@ func (r Wrapper) determineClientDID(ctx context.Context, authServerMetadata oaut
 	}
 	return &candidateDIDs[0], nil
 }
+
+// accessTokenRequestCacheKey creates a cache key for the access token request.
+// it writes the JSON to a sha256 hash and returns the hex encoded hash.
+func accessTokenRequestCacheKey(request RequestServiceAccessTokenRequestObject) string {
+	hash := sha256.New()
+	_ = json.NewEncoder(hash).Encode(request)
+	return hex.EncodeToString(hash.Sum(nil))
+}

auth/api/iam/api_test.go

@@ -24,12 +24,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"github.com/nuts-foundation/nuts-node/core/to"
-	"github.com/nuts-foundation/nuts-node/crypto/storage/spi"
-	test2 "github.com/nuts-foundation/nuts-node/crypto/test"
-	"github.com/nuts-foundation/nuts-node/http/user"
-	"github.com/nuts-foundation/nuts-node/test"
-	"github.com/nuts-foundation/nuts-node/vdr/didsubject"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -51,10 +45,15 @@ import (
 	"github.com/nuts-foundation/nuts-node/auth/oauth"
 	oauthServices "github.com/nuts-foundation/nuts-node/auth/services/oauth"
 	"github.com/nuts-foundation/nuts-node/core"
+	"github.com/nuts-foundation/nuts-node/core/to"
 	cryptoNuts "github.com/nuts-foundation/nuts-node/crypto"
+	"github.com/nuts-foundation/nuts-node/crypto/storage/spi"
+	test2 "github.com/nuts-foundation/nuts-node/crypto/test"
+	"github.com/nuts-foundation/nuts-node/http/user"
 	"github.com/nuts-foundation/nuts-node/jsonld"
 	"github.com/nuts-foundation/nuts-node/policy"
 	"github.com/nuts-foundation/nuts-node/storage"
+	"github.com/nuts-foundation/nuts-node/test"
 	"github.com/nuts-foundation/nuts-node/vcr"
 	"github.com/nuts-foundation/nuts-node/vcr/credential"
 	"github.com/nuts-foundation/nuts-node/vcr/holder"
@@ -63,6 +62,7 @@ import (
 	"github.com/nuts-foundation/nuts-node/vcr/types"
 	"github.com/nuts-foundation/nuts-node/vcr/verifier"
 	"github.com/nuts-foundation/nuts-node/vdr"
+	"github.com/nuts-foundation/nuts-node/vdr/didsubject"
 	"github.com/nuts-foundation/nuts-node/vdr/resolver"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -865,11 +865,31 @@ func TestWrapper_RequestServiceAccessToken(t *testing.T) {
 
 	t.Run("ok", func(t *testing.T) {
 		ctx := newTestClient(t)
+		request := RequestServiceAccessTokenRequestObject{SubjectID: holderSubjectID, Body: body}
 		ctx.iamClient.EXPECT().RequestRFC021AccessToken(nil, holderClientID, holderSubjectID, verifierURL.String(), "first second", true, nil).Return(&oauth.TokenResponse{}, nil)
 
-		_, err := ctx.client.RequestServiceAccessToken(nil, RequestServiceAccessTokenRequestObject{SubjectID: holderSubjectID, Body: body})
+		token, err := ctx.client.RequestServiceAccessToken(nil, request)
 
 		require.NoError(t, err)
+
+		t.Run("is cached", func(t *testing.T) {
+			cachedToken, err := ctx.client.RequestServiceAccessToken(nil, request)
+
+			require.NoError(t, err)
+			assert.Equal(t, token, cachedToken)
+		})
+
+		t.Run("cache expired", func(t *testing.T) {
+			cacheKey := accessTokenRequestCacheKey(request)
+			_ = ctx.client.accessTokenCache().Delete(cacheKey)
+			ctx.iamClient.EXPECT().RequestRFC021AccessToken(nil, holderClientID, holderSubjectID, verifierURL.String(), "first second", true, nil).Return(&oauth.TokenResponse{AccessToken: "other"}, nil)
+
+			otherToken, err := ctx.client.RequestServiceAccessToken(nil, request)
+
+			require.NoError(t, err)
+
+			assert.NotEqual(t, token, otherToken)
+		})
 	})
 	t.Run("ok - no DPoP", func(t *testing.T) {
 		ctx := newTestClient(t)
@@ -885,6 +905,16 @@ func TestWrapper_RequestServiceAccessToken(t *testing.T) {
 
 		require.NoError(t, err)
 	})
+	t.Run("ok with expired cache by ttl", func(t *testing.T) {
+		ctx := newTestClient(t)
+		request := RequestServiceAccessTokenRequestObject{SubjectID: holderSubjectID, Body: body}
+		ctx.iamClient.EXPECT().RequestRFC021AccessToken(nil, holderClientID, holderSubjectID, verifierURL.String(), "first second", true, nil).Return(&oauth.TokenResponse{ExpiresIn: to.Ptr(5)}, nil)
+
+		_, err := ctx.client.RequestServiceAccessToken(nil, request)
+
+		require.NoError(t, err)
+		assert.False(t, ctx.client.accessTokenCache().Exists(accessTokenRequestCacheKey(request)))
+	})
 	t.Run("error - no matching credentials", func(t *testing.T) {
 		ctx := newTestClient(t)
 		ctx.iamClient.EXPECT().RequestRFC021AccessToken(nil, holderClientID, holderSubjectID, verifierURL.String(), "first second", true, nil).Return(nil, pe.ErrNoCredentials)
@@ -895,6 +925,24 @@ func TestWrapper_RequestServiceAccessToken(t *testing.T) {
 		assert.Equal(t, err, pe.ErrNoCredentials)
 		assert.Equal(t, http.StatusPreconditionFailed, statusCodeFrom(err))
 	})
+	t.Run("broken cache", func(t *testing.T) {
+		ctx := newTestClient(t)
+		mockStorage := storage.NewMockEngine(ctx.ctrl)
+		errorSessionDatabase := storage.NewErrorSessionDatabase(assert.AnError)
+		mockStorage.EXPECT().GetSessionDatabase().Return(errorSessionDatabase).AnyTimes()
+		ctx.client.storageEngine = mockStorage
+
+		request := RequestServiceAccessTokenRequestObject{SubjectID: holderSubjectID, Body: body}
+		ctx.iamClient.EXPECT().RequestRFC021AccessToken(nil, holderClientID, holderSubjectID, verifierURL.String(), "first second", true, nil).Return(&oauth.TokenResponse{AccessToken: "first"}, nil)
+		ctx.iamClient.EXPECT().RequestRFC021AccessToken(nil, holderClientID, holderSubjectID, verifierURL.String(), "first second", true, nil).Return(&oauth.TokenResponse{AccessToken: "second"}, nil)
+
+		token1, err := ctx.client.RequestServiceAccessToken(nil, request)
+		require.NoError(t, err)
+		token2, err := ctx.client.RequestServiceAccessToken(nil, request)
+		require.NoError(t, err)
+
+		assert.NotEqual(t, token1, token2)
+	})
 }
 
 func TestWrapper_RequestUserAccessToken(t *testing.T) {
@@ -1320,6 +1368,15 @@ func TestWrapper_subjectOwns(t *testing.T) {
 	})
 }
 
+func TestWrapper_accessTokenRequestCacheKey(t *testing.T) {
+	expected := "0cc6fbbd972c72de7bc86c6147347bdd54bcb41fe23cea3d8f61d6ddd75dbf86"
+	key := accessTokenRequestCacheKey(RequestServiceAccessTokenRequestObject{SubjectID: holderSubjectID, Body: &RequestServiceAccessTokenJSONRequestBody{Scope: "test"}})
+	other := accessTokenRequestCacheKey(RequestServiceAccessTokenRequestObject{SubjectID: holderSubjectID, Body: &RequestServiceAccessTokenJSONRequestBody{Scope: "test2"}})
+
+	assert.Equal(t, expected, key)
+	assert.NotEqual(t, key, other)
+}
+
 func createIssuerCredential(issuerDID did.DID, holderDID did.DID) *vc.VerifiableCredential {
 	privateKey, _ := spi.GenerateKeyPair()
 	credType := ssi.MustParseURI("ExampleType")

storage/engine.go

@@ -147,7 +147,7 @@ func (e *engine) Shutdown() error {
 	}
 
 	// Close session database
-	e.sessionDatabase.close()
+	e.sessionDatabase.Close()
 	// Close SQL db
 	if e.sqlDB != nil {
 		underlyingDB, err := e.sqlDB.DB()

storage/interface.go

@@ -78,9 +78,11 @@ type SessionDatabase interface {
 	// The keys are used to logically partition the store, eg: tenants and/or flows that are not allowed to overlap like credential issuance and verification.
 	// The TTL is the time-to-live for the entries in the store.
 	GetStore(ttl time.Duration, keys ...string) SessionStore
-	// close stops any background processes and closes the database.
-	close()
+	// getFullKey returns the full key for the given key and prefixes.
+	// the supported chars differ per backend.
 	getFullKey(prefixes []string, key string) string
+	// Close stops any background processes and closes the database.
+	Close()
 }
 
 // SessionStore is a key-value store that holds session data.
@@ -95,10 +97,25 @@ type SessionStore interface {
 	// Returns ErrNotFound if the key does not exist.
 	Get(key string, target interface{}) error
 	// Put stores the given value for the given key.
-	Put(key string, value interface{}) error
+	// options can be used to fine-tune the storage of the item.
+	Put(key string, value interface{}, options ...SessionOption) error
 	// GetAndDelete combines Get and Delete as a convenience for burning nonce entries.
 	GetAndDelete(key string, target interface{}) error
 }
 
 // TransactionKey is the key used to store the SQL transaction in the context.
 type TransactionKey struct{}
+
+// SessionOption is an option that can be given when storing items.
+type SessionOption func(target *sessionOptions)
+
+type sessionOptions struct {
+	ttl time.Duration
+}
+
+// WithTTL sets the time-to-live for the stored item.
+func WithTTL(ttl time.Duration) SessionOption {
+	return func(target *sessionOptions) {
+		target.ttl = ttl
+	}
+}

storage/session.go

@@ -85,16 +85,31 @@ func (s SessionStoreImpl[T]) Get(key string, target interface{}) error {
 	return json.Unmarshal([]byte(val), target)
 }
 
-func (s SessionStoreImpl[T]) Put(key string, value interface{}) error {
+func (s SessionStoreImpl[T]) Put(key string, value interface{}, options ...SessionOption) error {
+	opts := s.defaultOptions()
+	for _, opt := range options {
+		opt(&opts)
+	}
+	// TTL can't go below 0 because that is translated to "no expiration" by the library
+	// in that case it should be 1 nanosecond
+	if opts.ttl < 0 {
+		opts.ttl = 1
+	}
 	bytes, err := json.Marshal(value)
 	if err != nil {
 		return err
 	}
-	return s.underlying.Set(context.Background(), s.db.getFullKey(s.prefixes, key), T(bytes), store.WithExpiration(s.ttl))
+	return s.underlying.Set(context.Background(), s.db.getFullKey(s.prefixes, key), T(bytes), store.WithExpiration(opts.ttl))
 }
 func (s SessionStoreImpl[T]) GetAndDelete(key string, target interface{}) error {
 	if err := s.Get(key, target); err != nil {
 		return err
 	}
 	return s.underlying.Delete(context.Background(), s.db.getFullKey(s.prefixes, key))
 }
+
+func (s SessionStoreImpl[T]) defaultOptions() sessionOptions {
+	return sessionOptions{
+		ttl: s.ttl,
+	}
+}

storage/session_inmemory.go

@@ -56,7 +56,7 @@ func (s *InMemorySessionDatabase) GetStore(ttl time.Duration, keys ...string) Se
 	}
 }
 
-func (s *InMemorySessionDatabase) close() {
+func (s *InMemorySessionDatabase) Close() {
 	// NOP
 }