support multiple subjects in oidc ping

Validate the subject in an oidc ping against a list of logged in subjects.

This resolves the issue that multiple connected FRP clients with different
OIDC clients result in a failing ping. The ping would fail because the
subject in memory would be the value of the last logged in FRPC.

This change also changes the constructor of OidcAuthVerifier to take
a TokenVerifier interface. This will not change production behavior, but makes
testing easier because we can inject a mock verifier during testing.

Resolves: fatedier#4466

pkg/auth/auth.go

@@ -50,7 +50,8 @@ func NewAuthVerifier(cfg v1.AuthServerConfig) (authVerifier Verifier) {
 	case v1.AuthMethodToken:
 		authVerifier = NewTokenAuth(cfg.AdditionalScopes, cfg.Token)
 	case v1.AuthMethodOIDC:
-		authVerifier = NewOidcAuthVerifier(cfg.AdditionalScopes, cfg.OIDC)
+		tokenVerifier := NewTokenVerifier(cfg.OIDC)
+		authVerifier = NewOidcAuthVerifier(cfg.AdditionalScopes, tokenVerifier)
 	}
 	return authVerifier
 }

pkg/auth/oidc.go

@@ -87,14 +87,18 @@ func (auth *OidcAuthProvider) SetNewWorkConn(newWorkConnMsg *msg.NewWorkConn) (e
 	return err
 }
 
+type TokenVerifier interface {
+	Verify(context.Context, string) (*oidc.IDToken, error)
+}
+
 type OidcAuthConsumer struct {
 	additionalAuthScopes []v1.AuthScope
 
-	verifier         *oidc.IDTokenVerifier
-	subjectFromLogin string
+	verifier          TokenVerifier
+	subjectsFromLogin []string
 }
 
-func NewOidcAuthVerifier(additionalAuthScopes []v1.AuthScope, cfg v1.AuthOIDCServerConfig) *OidcAuthConsumer {
+func NewTokenVerifier(cfg v1.AuthOIDCServerConfig) TokenVerifier {
 	provider, err := oidc.NewProvider(context.Background(), cfg.Issuer)
 	if err != nil {
 		panic(err)
@@ -105,9 +109,14 @@ func NewOidcAuthVerifier(additionalAuthScopes []v1.AuthScope, cfg v1.AuthOIDCSer
 		SkipExpiryCheck:   cfg.SkipExpiryCheck,
 		SkipIssuerCheck:   cfg.SkipIssuerCheck,
 	}
+	return provider.Verifier(&verifierConf)
+}
+
+func NewOidcAuthVerifier(additionalAuthScopes []v1.AuthScope, verifier TokenVerifier) *OidcAuthConsumer {
 	return &OidcAuthConsumer{
 		additionalAuthScopes: additionalAuthScopes,
-		verifier:             provider.Verifier(&verifierConf),
+		verifier:             verifier,
+		subjectsFromLogin:    []string{},
 	}
 }
 
@@ -116,7 +125,9 @@ func (auth *OidcAuthConsumer) VerifyLogin(loginMsg *msg.Login) (err error) {
 	if err != nil {
 		return fmt.Errorf("invalid OIDC token in login: %v", err)
 	}
-	auth.subjectFromLogin = token.Subject
+	if !slices.Contains(auth.subjectsFromLogin, token.Subject) {
+		auth.subjectsFromLogin = append(auth.subjectsFromLogin, token.Subject)
+	}
 	return nil
 }
 
@@ -125,11 +136,11 @@ func (auth *OidcAuthConsumer) verifyPostLoginToken(privilegeKey string) (err err
 	if err != nil {
 		return fmt.Errorf("invalid OIDC token in ping: %v", err)
 	}
-	if token.Subject != auth.subjectFromLogin {
+	if !slices.Contains(auth.subjectsFromLogin, token.Subject) {
 		return fmt.Errorf("received different OIDC subject in login and ping. "+
-			"original subject: %s, "+
+			"original subjects: %s, "+
 			"new subject: %s",
-			auth.subjectFromLogin, token.Subject)
+			auth.subjectsFromLogin, token.Subject)
 	}
 	return nil
 }

pkg/auth/oidc_test.go

@@ -0,0 +1,64 @@
+package auth_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/coreos/go-oidc/v3/oidc"
+	"github.com/stretchr/testify/require"
+
+	"github.com/fatedier/frp/pkg/auth"
+	v1 "github.com/fatedier/frp/pkg/config/v1"
+	"github.com/fatedier/frp/pkg/msg"
+)
+
+type mockTokenVerifier struct{}
+
+func (m *mockTokenVerifier) Verify(ctx context.Context, subject string) (*oidc.IDToken, error) {
+	return &oidc.IDToken{
+		Subject: subject,
+	}, nil
+}
+
+func TestPingWithEmptySubjectFromLoginFails(t *testing.T) {
+	r := require.New(t)
+	consumer := auth.NewOidcAuthVerifier([]v1.AuthScope{v1.AuthScopeHeartBeats}, &mockTokenVerifier{})
+	err := consumer.VerifyPing(&msg.Ping{
+		PrivilegeKey: "ping-without-login",
+		Timestamp:    time.Now().UnixMilli(),
+	})
+	r.Error(err)
+	r.Contains(err.Error(), "received different OIDC subject in login and ping")
+}
+
+func TestPingAfterLoginWithNewSubjectSucceeds(t *testing.T) {
+	r := require.New(t)
+	consumer := auth.NewOidcAuthVerifier([]v1.AuthScope{v1.AuthScopeHeartBeats}, &mockTokenVerifier{})
+	err := consumer.VerifyLogin(&msg.Login{
+		PrivilegeKey: "ping-after-login",
+	})
+	r.NoError(err)
+
+	err = consumer.VerifyPing(&msg.Ping{
+		PrivilegeKey: "ping-after-login",
+		Timestamp:    time.Now().UnixMilli(),
+	})
+	r.NoError(err)
+}
+
+func TestPingAfterLoginWithDifferentSubjectFails(t *testing.T) {
+	r := require.New(t)
+	consumer := auth.NewOidcAuthVerifier([]v1.AuthScope{v1.AuthScopeHeartBeats}, &mockTokenVerifier{})
+	err := consumer.VerifyLogin(&msg.Login{
+		PrivilegeKey: "login-with-first-subject",
+	})
+	r.NoError(err)
+
+	err = consumer.VerifyPing(&msg.Ping{
+		PrivilegeKey: "ping-with-different-subject",
+		Timestamp:    time.Now().UnixMilli(),
+	})
+	r.Error(err)
+	r.Contains(err.Error(), "received different OIDC subject in login and ping")
+}