feat: support multiple token URLs

.github/workflows/format.yml

@@ -11,7 +11,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v3
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - run: make format
       - name: Indicate formatting issues
         run: git diff HEAD --exit-code --color

.github/workflows/licenses.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-go@v2
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - uses: actions/setup-node@v2
         with:
           node-version: "18"

.github/workflows/oidc-conformity-master.yml

@@ -17,7 +17,7 @@ jobs:
           ref: master
       - uses: actions/setup-go@v2
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - name: Update fosite
         run: |
           go mod edit -replace github.com/ory/fosite=github.com/ory/fosite@${{ github.sha }}

.github/workflows/oidc-conformity.yml

@@ -17,7 +17,7 @@ jobs:
           ref: master
       - uses: actions/setup-go@v2
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - name: Update fosite
         run: |
           go mod edit -replace github.com/ory/fosite=github.com/${{ github.event.pull_request.head.repo.full_name }}@${{ github.event.pull_request.head.sha }}

.github/workflows/test.yml

@@ -11,5 +11,5 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v3
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - run: make test

client_authentication.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"strings"
 	"time"
 
 	"github.com/ory/x/errorsx"
@@ -149,7 +150,7 @@ func (f *Fosite) DefaultClientAuthenticationStrategy(ctx context.Context, r *htt
 		var jti string
 		if !claims.VerifyIssuer(clientID, true) {
 			return nil, errorsx.WithStack(ErrInvalidClient.WithHint("Claim 'iss' from 'client_assertion' must match the 'client_id' of the OAuth 2.0 Client."))
-		} else if f.Config.GetTokenURL(ctx) == "" {
+		} else if len(f.Config.GetTokenURLs(ctx)) == 0 {
 			return nil, errorsx.WithStack(ErrMisconfiguration.WithHint("The authorization server's token endpoint URL has not been set."))
 		} else if sub, ok := claims["sub"].(string); !ok || sub != clientID {
 			return nil, errorsx.WithStack(ErrInvalidClient.WithHint("Claim 'sub' from 'client_assertion' must match the 'client_id' of the OAuth 2.0 Client."))
@@ -180,22 +181,10 @@ func (f *Fosite) DefaultClientAuthenticationStrategy(ctx context.Context, r *htt
 			return nil, err
 		}
 
-		if auds, ok := claims["aud"].([]interface{}); !ok {
-			if !claims.VerifyAudience(f.Config.GetTokenURL(ctx), true) {
-				return nil, errorsx.WithStack(ErrInvalidClient.WithHintf("Claim 'audience' from 'client_assertion' must match the authorization server's token endpoint '%s'.", f.Config.GetTokenURL(ctx)))
-			}
-		} else {
-			var found bool
-			for _, aud := range auds {
-				if a, ok := aud.(string); ok && a == f.Config.GetTokenURL(ctx) {
-					found = true
-					break
-				}
-			}
-
-			if !found {
-				return nil, errorsx.WithStack(ErrInvalidClient.WithHintf("Claim 'audience' from 'client_assertion' must match the authorization server's token endpoint '%s'.", f.Config.GetTokenURL(ctx)))
-			}
+		if !audienceMatchesTokenURLs(claims, f.Config.GetTokenURLs(ctx)) {
+			return nil, errorsx.WithStack(ErrInvalidClient.WithHintf(
+				"Claim 'audience' from 'client_assertion' must match the authorization server's token endpoint '%s'.",
+				strings.Join(f.Config.GetTokenURLs(ctx), "' or '")))
 		}
 
 		return client, nil
@@ -235,6 +224,27 @@ func (f *Fosite) DefaultClientAuthenticationStrategy(ctx context.Context, r *htt
 	return client, nil
 }
 
+func audienceMatchesTokenURLs(claims jwt.MapClaims, tokenURLs []string) bool {
+	for _, tokenURL := range tokenURLs {
+		if audienceMatchesTokenURL(claims, tokenURL) {
+			return true
+		}
+	}
+	return false
+}
+
+func audienceMatchesTokenURL(claims jwt.MapClaims, tokenURL string) bool {
+	if audiences, ok := claims["aud"].([]interface{}); ok {
+		for _, aud := range audiences {
+			if a, ok := aud.(string); ok && a == tokenURL {
+				return true
+			}
+		}
+		return false
+	}
+	return claims.VerifyAudience(tokenURL, true)
+}
+
 func (f *Fosite) checkClientSecret(ctx context.Context, client Client, clientSecret []byte) error {
 	var err error
 	err = f.Config.GetSecretsHasher(ctx).Compare(ctx, client.GetHashedSecret(), clientSecret)

config.go

@@ -247,8 +247,8 @@ type FormPostHTMLTemplateProvider interface {
 }
 
 type TokenURLProvider interface {
-	// GetTokenURL returns the token URL.
-	GetTokenURL(ctx context.Context) string
+	// GetTokenURLs returns the token URL.
+	GetTokenURLs(ctx context.Context) []string
 }
 
 // AuthorizeEndpointHandlersProvider returns the provider for configuring the authorize endpoint handlers.

config_default.go

@@ -263,8 +263,8 @@ func (c *Config) GetSecretsHasher(ctx context.Context) Hasher {
 	return c.ClientSecretsHasher
 }
 
-func (c *Config) GetTokenURL(ctx context.Context) string {
-	return c.TokenURL
+func (c *Config) GetTokenURLs(ctx context.Context) []string {
+	return []string{c.TokenURL}
 }
 
 func (c *Config) GetFormPostHTMLTemplate(ctx context.Context) *template.Template {

handler/rfc7523/handler.go

@@ -5,6 +5,7 @@ package rfc7523
 
 import (
 	"context"
+	"strings"
 	"time"
 
 	"github.com/ory/fosite/handler/oauth2"
@@ -228,13 +229,11 @@ func (c *Handler) validateTokenClaims(ctx context.Context, claims jwt.Claims, ke
 		)
 	}
 
-	if !claims.Audience.Contains(c.Config.GetTokenURL(ctx)) {
+	if !audienceMatchesTokenURLs(claims, c.Config.GetTokenURLs(ctx)) {
 		return errorsx.WithStack(fosite.ErrInvalidGrant.
 			WithHintf(
-				"The JWT in \"assertion\" request parameter MUST contain an \"aud\" (audience) claim containing a value \"%s\" that identifies the authorization server as an intended audience.",
-				c.Config.GetTokenURL(ctx),
-			),
-		)
+				`The JWT in "assertion" request parameter MUST contain an "aud" (audience) claim containing a value "%s" that identifies the authorization server as an intended audience.`,
+				strings.Join(c.Config.GetTokenURLs(ctx), `" or "`)))
 	}
 
 	if claims.Expiry == nil {
@@ -299,6 +298,15 @@ func (c *Handler) validateTokenClaims(ctx context.Context, claims jwt.Claims, ke
 	return nil
 }
 
+func audienceMatchesTokenURLs(claims jwt.Claims, tokenURLs []string) bool {
+	for _, tokenURL := range tokenURLs {
+		if claims.Audience.Contains(tokenURL) {
+			return true
+		}
+	}
+	return false
+}
+
 type extendedSession interface {
 	Session
 	fosite.Session

handler/rfc7523/handler_test.go

@@ -12,6 +12,7 @@ import (
 	mrand "math/rand"
 	"net/url"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -331,8 +332,8 @@ func (s *AuthorizeJWTGrantRequestHandlerTestSuite) TestNotValidAudienceInAsserti
 	s.EqualError(err, fosite.ErrInvalidGrant.Error(), "expected error, because of invalid audience claim in assertion")
 	s.Equal(
 		fmt.Sprintf(
-			"The JWT in \"assertion\" request parameter MUST contain an \"aud\" (audience) claim containing a value \"%s\" that identifies the authorization server as an intended audience.",
-			s.handler.Config.GetTokenURL(ctx),
+			`The JWT in "assertion" request parameter MUST contain an "aud" (audience) claim containing a value "%s" that identifies the authorization server as an intended audience.`,
+			strings.Join(s.handler.Config.GetTokenURLs(ctx), `" or "`),
 		),
 		fosite.ErrorToRFC6749Error(err).HintField,
 	)