fix: improve login_hint usage on IDPs (#6899)

* only set prompt if no login_hint is set

* update to current state and cleanup

(cherry picked from commit 0386fe7f96)

internal/api/ui/login/external_provider_handler.go

@@ -1173,8 +1173,9 @@ func mapExternalNotFoundOptionFormDataToLoginUser(formData *externalNotFoundOpti
 	}
 }
 
-func (l *Login) sessionParamsFromAuthRequest(ctx context.Context, authReq *domain.AuthRequest, identityProviderID string) []any {
-	params := []any{authReq.AgentID}
+func (l *Login) sessionParamsFromAuthRequest(ctx context.Context, authReq *domain.AuthRequest, identityProviderID string) []idp.Parameter {
+	params := make([]idp.Parameter, 1, 2)
+	params[0] = idp.UserAgentID(authReq.AgentID)
 
 	if authReq.UserID != "" && identityProviderID != "" {
 		links, err := l.getUserLinks(ctx, authReq.UserID, identityProviderID)
@@ -1183,27 +1184,21 @@ func (l *Login) sessionParamsFromAuthRequest(ctx context.Context, authReq *domai
 			return params
 		}
 		if len(links.Links) == 1 {
-			return append(params, keyAndValueToAuthURLOpt("login_hint", links.Links[0].ProvidedUsername))
+			return append(params, idp.LoginHintParam(links.Links[0].ProvidedUsername))
 		}
 	}
 	if authReq.UserName != "" {
-		return append(params, keyAndValueToAuthURLOpt("login_hint", authReq.UserName))
+		return append(params, idp.LoginHintParam(authReq.UserName))
 	}
 	if authReq.LoginName != "" {
-		return append(params, keyAndValueToAuthURLOpt("login_hint", authReq.LoginName))
+		return append(params, idp.LoginHintParam(authReq.LoginName))
 	}
 	if authReq.LoginHint != "" {
-		return append(params, keyAndValueToAuthURLOpt("login_hint", authReq.LoginHint))
+		return append(params, idp.LoginHintParam(authReq.LoginHint))
 	}
 	return params
 }
 
-func keyAndValueToAuthURLOpt(key, value string) rp.AuthURLOpt {
-	return func() []oauth2.AuthCodeOption {
-		return []oauth2.AuthCodeOption{oauth2.SetAuthURLParam(key, value)}
-	}
-}
-
 func (l *Login) getUserLinks(ctx context.Context, userID, idpID string) (*query.IDPUserLinks, error) {
 	userIDQuery, err := query.NewIDPUserLinksUserIDSearchQuery(userID)
 	if err != nil {

internal/idp/provider.go

@@ -11,7 +11,7 @@ import (
 // Provider is the minimal implementation for a 3rd party authentication provider
 type Provider interface {
 	Name() string
-	BeginAuth(ctx context.Context, state string, params ...any) (Session, error)
+	BeginAuth(ctx context.Context, state string, params ...Parameter) (Session, error)
 	IsLinkingAllowed() bool
 	IsCreationAllowed() bool
 	IsAutoCreation() bool
@@ -34,3 +34,18 @@ type User interface {
 	GetAvatarURL() string
 	GetProfile() string
 }
+
+// Parameter allows to pass specific parameter to the BeginAuth function
+type Parameter interface {
+	setValue()
+}
+
+// UserAgentID allows to pass the user agent ID of the auth request to BeginAuth
+type UserAgentID string
+
+func (p UserAgentID) setValue() {}
+
+// LoginHintParam allows to pass a login_hint to BeginAuth
+type LoginHintParam string
+
+func (p LoginHintParam) setValue() {}

internal/idp/providers/jwt/jwt.go

@@ -91,13 +91,10 @@ func (p *Provider) Name() string {
 // BeginAuth implements the [idp.Provider] interface.
 // It will create a [Session] with an AuthURL, pointing to the jwtEndpoint
 // with the authRequest and encrypted userAgent ids.
-func (p *Provider) BeginAuth(ctx context.Context, state string, params ...any) (idp.Session, error) {
-	if len(params) < 1 {
-		return nil, ErrMissingUserAgentID
-	}
-	userAgentID, ok := params[0].(string)
-	if !ok {
-		return nil, ErrMissingUserAgentID
+func (p *Provider) BeginAuth(ctx context.Context, state string, params ...idp.Parameter) (idp.Session, error) {
+	userAgentID, err := userAgentIDFromParams(params...)
+	if err != nil {
+		return nil, err
 	}
 	redirect, err := url.Parse(p.jwtEndpoint)
 	if err != nil {
@@ -114,6 +111,15 @@ func (p *Provider) BeginAuth(ctx context.Context, state string, params ...any) (
 	return &Session{AuthURL: redirect.String()}, nil
 }
 
+func userAgentIDFromParams(params ...idp.Parameter) (string, error) {
+	for _, param := range params {
+		if id, ok := param.(idp.UserAgentID); ok {
+			return string(id), nil
+		}
+	}
+	return "", ErrMissingUserAgentID
+}
+
 // IsLinkingAllowed implements the [idp.Provider] interface.
 func (p *Provider) IsLinkingAllowed() bool {
 	return p.isLinkingAllowed

internal/idp/providers/jwt/jwt_test.go

@@ -23,7 +23,7 @@ func TestProvider_BeginAuth(t *testing.T) {
 		encryptionAlg func(t *testing.T) crypto.EncryptionAlgorithm
 	}
 	type args struct {
-		params []any
+		params []idp.Parameter
 	}
 	type want struct {
 		session idp.Session
@@ -55,28 +55,6 @@ func TestProvider_BeginAuth(t *testing.T) {
 				},
 			},
 		},
-		{
-			name: "invalid userAgentID error",
-			fields: fields{
-				issuer:       "https://jwt.com",
-				jwtEndpoint:  "https://auth.com/jwt",
-				keysEndpoint: "https://jwt.com/keys",
-				headerName:   "jwt-header",
-				encryptionAlg: func(t *testing.T) crypto.EncryptionAlgorithm {
-					return crypto.CreateMockEncryptionAlg(gomock.NewController(t))
-				},
-			},
-			args: args{
-				params: []any{
-					0,
-				},
-			},
-			want: want{
-				err: func(err error) bool {
-					return errors.Is(err, ErrMissingUserAgentID)
-				},
-			},
-		},
 		{
 			name: "successful auth",
 			fields: fields{
@@ -89,8 +67,8 @@ func TestProvider_BeginAuth(t *testing.T) {
 				},
 			},
 			args: args{
-				params: []any{
-					"agent",
+				params: []idp.Parameter{
+					idp.UserAgentID("agent"),
 				},
 			},
 			want: want{

internal/idp/providers/ldap/ldap.go

@@ -211,7 +211,7 @@ func (p *Provider) Name() string {
 	return p.name
 }
 
-func (p *Provider) BeginAuth(ctx context.Context, state string, params ...any) (idp.Session, error) {
+func (p *Provider) BeginAuth(ctx context.Context, state string, _ ...idp.Parameter) (idp.Session, error) {
 	return &Session{
 		Provider: p,
 		loginUrl: p.loginUrl + state,

internal/idp/providers/oauth/oauth2.go

@@ -87,17 +87,28 @@ func (p *Provider) Name() string {
 
 // BeginAuth implements the [idp.Provider] interface.
 // It will create a [Session] with an OAuth2.0 authorization request as AuthURL.
-func (p *Provider) BeginAuth(ctx context.Context, state string, params ...any) (idp.Session, error) {
-	opts := []rp.AuthURLOpt{rp.WithPrompt(oidc.PromptSelectAccount)}
+func (p *Provider) BeginAuth(ctx context.Context, state string, params ...idp.Parameter) (idp.Session, error) {
+	opts := make([]rp.AuthURLOpt, 0)
+	var loginHintSet bool
 	for _, param := range params {
-		if option, ok := param.(rp.AuthURLOpt); ok {
-			opts = append(opts, option)
+		if username, ok := param.(idp.LoginHintParam); ok {
+			loginHintSet = true
+			opts = append(opts, loginHint(string(username)))
 		}
 	}
+	if !loginHintSet {
+		opts = append(opts, rp.WithPrompt(oidc.PromptSelectAccount))
+	}
 	url := rp.AuthURL(state, p.RelyingParty, opts...)
 	return &Session{AuthURL: url, Provider: p}, nil
 }
 
+func loginHint(hint string) rp.AuthURLOpt {
+	return func() []oauth2.AuthCodeOption {
+		return []oauth2.AuthCodeOption{oauth2.SetAuthURLParam("login_hint", hint)}
+	}
+}
+
 // IsLinkingAllowed implements the [idp.Provider] interface.
 func (p *Provider) IsLinkingAllowed() bool {
 	return p.isLinkingAllowed

internal/idp/providers/oidc/oidc.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/zitadel/oidc/v3/pkg/client/rp"
 	"github.com/zitadel/oidc/v3/pkg/oidc"
+	"golang.org/x/oauth2"
 
 	"github.com/zitadel/zitadel/internal/idp"
 )
@@ -22,7 +23,7 @@ type Provider struct {
 	isAutoUpdate      bool
 	useIDToken        bool
 	userInfoMapper    func(info *oidc.UserInfo) idp.User
-	authOptions       []rp.AuthURLOpt
+	authOptions       []func(bool) rp.AuthURLOpt
 }
 
 type ProviderOpts func(provider *Provider)
@@ -70,10 +71,15 @@ func WithRelyingPartyOption(option rp.Option) ProviderOpts {
 	}
 }
 
-// WithSelectAccount adds the select_account prompt to the auth request
+// WithSelectAccount adds the select_account prompt to the auth request (if no login_hint is set)
 func WithSelectAccount() ProviderOpts {
 	return func(p *Provider) {
-		p.authOptions = append(p.authOptions, rp.WithPrompt(oidc.PromptSelectAccount))
+		p.authOptions = append(p.authOptions, func(loginHintSet bool) rp.AuthURLOpt {
+			if loginHintSet {
+				return nil
+			}
+			return rp.WithPrompt(oidc.PromptSelectAccount)
+		})
 	}
 }
 
@@ -81,7 +87,9 @@ func WithSelectAccount() ProviderOpts {
 func WithResponseMode(mode oidc.ResponseMode) ProviderOpts {
 	return func(p *Provider) {
 		paramOpt := rp.WithResponseModeURLParam(mode)
-		p.authOptions = append(p.authOptions, rp.AuthURLOpt(paramOpt))
+		p.authOptions = append(p.authOptions, func(_ bool) rp.AuthURLOpt {
+			return rp.AuthURLOpt(paramOpt)
+		})
 	}
 }
 
@@ -128,17 +136,30 @@ func (p *Provider) Name() string {
 
 // BeginAuth implements the [idp.Provider] interface.
 // It will create a [Session] with an OIDC authorization request as AuthURL.
-func (p *Provider) BeginAuth(ctx context.Context, state string, params ...any) (idp.Session, error) {
-	opts := p.authOptions
+func (p *Provider) BeginAuth(ctx context.Context, state string, params ...idp.Parameter) (idp.Session, error) {
+	opts := make([]rp.AuthURLOpt, 0)
+	var loginHintSet bool
 	for _, param := range params {
-		if option, ok := param.(rp.AuthURLOpt); ok {
-			opts = append(opts, option)
+		if username, ok := param.(idp.LoginHintParam); ok {
+			loginHintSet = true
+			opts = append(opts, loginHint(string(username)))
+		}
+	}
+	for _, option := range p.authOptions {
+		if opt := option(loginHintSet); opt != nil {
+			opts = append(opts, opt)
 		}
 	}
 	url := rp.AuthURL(state, p.RelyingParty, opts...)
 	return &Session{AuthURL: url, Provider: p}, nil
 }
 
+func loginHint(hint string) rp.AuthURLOpt {
+	return func() []oauth2.AuthCodeOption {
+		return []oauth2.AuthCodeOption{oauth2.SetAuthURLParam("login_hint", hint)}
+	}
+}
+
 // IsLinkingAllowed implements the [idp.Provider] interface.
 func (p *Provider) IsLinkingAllowed() bool {
 	return p.isLinkingAllowed

internal/idp/providers/saml/saml.go

@@ -162,7 +162,7 @@ func (p *Provider) GetSP() (*samlsp.Middleware, error) {
 	return sp, nil
 }
 
-func (p *Provider) BeginAuth(ctx context.Context, state string, params ...any) (idp.Session, error) {
+func (p *Provider) BeginAuth(ctx context.Context, state string, _ ...idp.Parameter) (idp.Session, error) {
 	m, err := p.GetSP()
 	if err != nil {
 		return nil, err