[client] Pass the login hint to GetOAuthFlow at construction

GetOAuthFlow was the only flow factory without a hint parameter, which
forced its callers to apply the hint afterwards through a local setter
interface and a type assertion. Give it the same constructor-style hint
as NewOAuthFlow and set the hint on the concrete flows before they are
handed out as the interface, so a flow is always complete when built
and the caller-side ordering constraint disappears.

An empty hint is a valid value meaning the IdP chooses the account, so
the flows set it unconditionally.

client/android/login.go

@@ -191,20 +191,13 @@ func (a *Auth) login(urlOpener URLOpener, isAndroidTV bool) error {
 	return nil
 }
 
-// loginHintSetter is implemented by both concrete flows (PKCE and device code)
-// but absent from the OAuthFlow interface, hence the assertion below — the same
-// way internal/auth wires it in authenticateWithPKCEFlow.
-type loginHintSetter interface {
-	SetLoginHint(hint string)
-}
-
 func (a *Auth) foregroundGetTokenInfo(authClient *auth.Auth, urlOpener URLOpener, isAndroidTV bool) (*auth.TokenInfo, error) {
-	oAuthFlow, err := authClient.GetOAuthFlow(a.ctx, isAndroidTV)
+	oAuthFlow, err := authClient.GetOAuthFlow(a.ctx, isAndroidTV, profileLoginHint(a.cfgPath))
 	if err != nil {
 		return nil, fmt.Errorf("failed to get OAuth flow: %v", err)
 	}
 
-	return runOAuthFlow(a.ctx, oAuthFlow, profileLoginHint(a.cfgPath), urlOpener, nil)
+	return runOAuthFlow(a.ctx, oAuthFlow, urlOpener, nil)
 }
 
 // profileLoginHint returns the stored account email for the profile at cfgPath.
@@ -217,21 +210,15 @@ func profileLoginHint(cfgPath string) string {
 	return readProfileEmail(cfgPath)
 }
 
-// runOAuthFlow drives an already acquired OAuth flow to a token: applies the
-// login hint, requests the flow info, presents the verification URL through
-// the opener and waits for the browser round-trip. Open is called
-// synchronously — it is what marks the surface as opened on the client side,
-// and a fast token's OnLoginSuccess is a no-op until it has, so the dismissal
-// would be dropped rather than delayed. Openers must therefore not block:
-// they post their UI work and return. onWaiting, when set, runs after the URL
-// is shown, right before the blocking wait.
-func runOAuthFlow(ctx context.Context, flow auth.OAuthFlow, hint string, urlOpener URLOpener, onWaiting func()) (*auth.TokenInfo, error) {
-	if hint != "" {
-		if setter, ok := flow.(loginHintSetter); ok {
-			setter.SetLoginHint(hint)
-		}
-	}
-
+// runOAuthFlow drives an already acquired OAuth flow to a token: requests the
+// flow info, presents the verification URL through the opener and waits for
+// the browser round-trip. Open is called synchronously — it is what marks the
+// surface as opened on the client side, and a fast token's OnLoginSuccess is
+// a no-op until it has, so the dismissal would be dropped rather than
+// delayed. Openers must therefore not block: they post their UI work and
+// return. onWaiting, when set, runs after the URL is shown, right before the
+// blocking wait.
+func runOAuthFlow(ctx context.Context, flow auth.OAuthFlow, urlOpener URLOpener, onWaiting func()) (*auth.TokenInfo, error) {
 	flowInfo, err := flow.RequestAuthInfo(ctx)
 	if err != nil {
 		return nil, fmt.Errorf("request auth info: %w", err)

client/android/ssh_client.go

@@ -476,14 +476,14 @@ func (s *SSHClient) requestJWTToken(cfg *profilemanager.Config, cfgPath string)
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
 	defer cancel()
 
-	flow, err := auth.NewOAuthFlow(ctx, cfg, false, true, "")
+	flow, err := auth.NewOAuthFlow(ctx, cfg, false, true, profileLoginHint(cfgPath))
 	if err != nil {
 		return "", fmt.Errorf("create oauth flow: %w", err)
 	}
 
 	// The status callback covers the browser round-trip, which would
 	// otherwise leave the terminal blank.
-	tokenInfo, err := runOAuthFlow(ctx, flow, profileLoginHint(cfgPath), urlOpener, func() {
+	tokenInfo, err := runOAuthFlow(ctx, flow, urlOpener, func() {
 		s.notifyStatus("Waiting for browser authentication...")
 	})
 	if err != nil {

client/internal/auth/auth.go

@@ -138,26 +138,37 @@ func (a *Auth) IsSSOSupported(ctx context.Context) (bool, error) {
 
 // GetOAuthFlow returns an OAuth flow (PKCE or Device) using the existing management connection
 // This avoids creating a new connection to the management server
-func (a *Auth) GetOAuthFlow(ctx context.Context, forceDeviceAuth bool) (OAuthFlow, error) {
+func (a *Auth) GetOAuthFlow(ctx context.Context, forceDeviceAuth bool, hint string) (OAuthFlow, error) {
 	var flow OAuthFlow
-	var err error
 
-	err = a.withRetry(ctx, func(client *mgm.GrpcClient) error {
+	err := a.withRetry(ctx, func(client *mgm.GrpcClient) error {
 		if forceDeviceAuth {
-			flow, err = a.getDeviceFlow(client)
-			return err
+			deviceFlow, err := a.getDeviceFlow(client)
+			if err != nil {
+				return err
+			}
+			deviceFlow.SetLoginHint(hint)
+			flow = deviceFlow
+			return nil
 		}
 
 		// Try PKCE flow first
-		flow, err = a.getPKCEFlow(client)
+		pkceFlow, err := a.getPKCEFlow(client)
 		if err != nil {
 			// If PKCE not supported, try Device flow
 			if s, ok := status.FromError(err); ok && (s.Code() == codes.NotFound || s.Code() == codes.Unimplemented) {
-				flow, err = a.getDeviceFlow(client)
-				return err
+				deviceFlow, err := a.getDeviceFlow(client)
+				if err != nil {
+					return err
+				}
+				deviceFlow.SetLoginHint(hint)
+				flow = deviceFlow
+				return nil
 			}
 			return err
 		}
+		pkceFlow.SetLoginHint(hint)
+		flow = pkceFlow
 		return nil
 	})
 

client/internal/auth/oauth.go

@@ -97,9 +97,7 @@ func authenticateWithPKCEFlow(ctx context.Context, config *profilemanager.Config
 		return nil, fmt.Errorf("getting pkce authorization flow info failed with error: %v", err)
 	}
 
-	if hint != "" {
-		pkceFlowInfo.SetLoginHint(hint)
-	}
+	pkceFlowInfo.SetLoginHint(hint)
 
 	return pkceFlowInfo, nil
 }
@@ -127,9 +125,7 @@ func authenticateWithDeviceCodeFlow(ctx context.Context, config *profilemanager.
 		}
 	}
 
-	if hint != "" {
-		deviceFlowInfo.SetLoginHint(hint)
-	}
+	deviceFlowInfo.SetLoginHint(hint)
 
 	return deviceFlowInfo, nil
 }

client/ios/NetBirdSDK/login.go

@@ -323,7 +323,7 @@ func (a *Auth) login(urlOpener URLOpener, forceDeviceAuth bool, deviceName strin
 const authInfoRequestTimeout = 30 * time.Second
 
 func (a *Auth) foregroundGetTokenInfo(authClient *auth.Auth, urlOpener URLOpener, forceDeviceAuth bool) (*auth.TokenInfo, error) {
-	oAuthFlow, err := authClient.GetOAuthFlow(a.ctx, forceDeviceAuth)
+	oAuthFlow, err := authClient.GetOAuthFlow(a.ctx, forceDeviceAuth, "")
 	if err != nil {
 		return nil, fmt.Errorf("failed to get OAuth flow: %v", err)
 	}