Keycloak JS Adapter Bug: Missing Ui_locales Parameter With OnLoad Check-sso

July 13, 2025 by StackCamp Team 76 views

Keycloak JS Adapter Bug ui_locales Parameter Missing with onLoad check-sso

This article addresses a critical bug encountered in the Keycloak JS adapter, specifically concerning the ui_locales parameter when using the onLoad: 'check-sso' option. Keycloak, a leading open-source identity and access management solution, relies on the keycloak-js adapter for seamless integration with JavaScript applications. The issue arises when initializing the adapter with a specified locale and utilizing the check-sso option, which is designed to silently authenticate users if an existing session is present. The problem is that the ui_locales parameter, essential for localizing the Keycloak login screen, is not included in the authentication request when onLoad is set to check-sso. This behavior deviates from the expected functionality and the OpenID Connect (OIDC) 1.0 specification, which mandates the inclusion of the ui_locales parameter in all authentication requests. The absence of this parameter leads to a non-localized login experience, potentially confusing users and hindering the overall user experience. This article delves into the details of the bug, its impact, steps to reproduce it, and the expected versus actual behavior, providing a comprehensive understanding of the issue and its implications for Keycloak users.

Understanding the Keycloak JS Adapter

The Keycloak JS adapter serves as a crucial bridge between JavaScript applications and Keycloak servers, facilitating secure authentication and authorization processes. This adapter simplifies the integration of Keycloak's robust identity management features into web applications, allowing developers to focus on building application logic rather than wrestling with complex security protocols. Keycloak, as a comprehensive Identity and Access Management (IAM) solution, offers a wide array of functionalities, including single sign-on (SSO), identity brokering, and user federation. The keycloak-js adapter encapsulates the necessary logic to interact with Keycloak's authentication endpoints, manage tokens, and handle user sessions within a JavaScript environment. This adapter is particularly important for Single Page Applications (SPAs) and other JavaScript-heavy applications where maintaining a secure and seamless user experience is paramount.

Keycloak Initialization Options

When initializing the keycloak-js adapter, developers have several options at their disposal to configure the authentication flow. Among these, the onLoad option plays a pivotal role in determining how the adapter handles the initial authentication process. The two primary values for onLoad are 'login-required' and 'check-sso'. The 'login-required' option forces an immediate redirect to the Keycloak login page if the user is not already authenticated. This approach ensures that the user is always prompted to log in if no existing session is found. On the other hand, the 'check-sso' option attempts to silently authenticate the user by checking for an existing SSO session. If a session is present, the user is automatically authenticated without any intervention. If no session is found, the user remains unauthenticated, and the application can then decide how to proceed, such as displaying a login button or redirecting to the login page. The locale option is another critical configuration setting, allowing developers to specify the desired language for the Keycloak login screen and other user-facing elements. This option is crucial for providing a localized user experience, ensuring that users are greeted with a login interface in their preferred language. The ui_locales parameter, as defined in the OpenID Connect (OIDC) specification, is the mechanism by which the requested locale is communicated to the authentication server.

The Bug: Missing ui_locales Parameter with check-sso

Problem Description

The core issue at hand is the absence of the ui_locales parameter in the authentication request when the keycloak-js adapter is initialized with the onLoad: 'check-sso' option. This bug prevents the Keycloak login screen from being displayed in the user's preferred language, despite the locale option being correctly set during initialization. According to the OpenID Connect (OIDC) 1.0 specification, the ui_locales parameter should be included in all authentication requests to ensure proper localization. This discrepancy leads to an inconsistent user experience, as the login screen may appear in a default language rather than the user's chosen language. This can cause confusion and frustration for users, especially in multilingual environments where providing a localized experience is crucial. The bug specifically manifests when the adapter attempts to silently authenticate the user using the check-sso option. If the user does not have an existing session, they are redirected to the Keycloak login page. However, because the ui_locales parameter is missing, the login page defaults to the server's configured language, ignoring the application's locale setting.

Expected vs. Actual Behavior

Expected Behavior: When the keycloak-js adapter is initialized with the locale option (e.g., locale: 'fr') and onLoad: 'check-sso', the authentication request sent to the Keycloak server should include the ui_locales parameter (e.g., ui_locales=fr). This ensures that the login screen is displayed in the specified language, providing a consistent and localized user experience. Regardless of the onLoad option, the ui_locales parameter should always be present in the authentication request when a locale is specified.

Actual Behavior: When using onLoad: 'check-sso', the authentication request sent to the Keycloak server does not include the ui_locales parameter, even if the locale option is set. This results in the login screen not being localized according to the specified locale. In contrast, when using onLoad: 'login-required', the ui_locales parameter is correctly included in the authentication request, and the login screen is displayed in the appropriate language. This inconsistency highlights the bug's specific impact on the check-sso flow.

Reproducing the Bug

To effectively address this bug, it's essential to understand how to reproduce it. By following a series of steps, developers and testers can confirm the issue and verify that any potential fixes resolve the problem.

Step-by-Step Instructions

Install and configure the latest keycloak-js npm package: Begin by setting up a JavaScript project and installing the keycloak-js package using npm or yarn. Ensure you are using the latest version to accurately reflect the current state of the adapter.
```
npm install keycloak-js
```

Initialize Keycloak with the check-sso option and a specific locale: Create a Keycloak instance and initialize it with the onLoad: 'check-sso' option and a desired locale (e.g., 'fr' for French). This configuration is crucial for triggering the bug.

import Keycloak from 'keycloak-js';

const keycloak = new Keycloak({
  url: 'https://<keycloak-server>/auth',
  realm: 'myrealm',
  clientId: 'myclient',
});

keycloak.init({
  onLoad: 'check-sso',
  locale: 'fr',
}).then((authenticated) => {
  if (authenticated) {
    console.log('Authenticated');
  } else {
    console.log('Not Authenticated');
  }
}).catch(() => {
  console.error('Failed to initialize');
});

Inspect the authentication request: Use your browser's developer tools (usually accessed by pressing F12) to monitor the network requests. Look for the request sent to the Keycloak server's authorization endpoint. This request should contain the parameters that the keycloak-js adapter is sending.
Observe the missing ui_locales parameter: Examine the query string of the authentication request. You should find that the ui_locales=fr parameter is missing, despite setting the locale option during initialization. This is the key indicator of the bug.

Verifying the Correct Behavior with `login-required`

To further confirm the bug, repeat the steps above, but this time, initialize Keycloak with onLoad: 'login-required'. You should observe that the ui_locales parameter is correctly included in the authentication request when using this option. This comparison highlights the inconsistency in behavior between the two onLoad options and reinforces the presence of the bug in the check-sso flow.

Impact and Implications

The bug in the Keycloak JS adapter, where the ui_locales parameter is missing with onLoad: 'check-sso', has significant implications for applications aiming to provide a seamless and localized user experience. Understanding the potential impact is crucial for developers and organizations relying on Keycloak for identity and access management.

User Experience Degradation

The primary consequence of this bug is the degradation of the user experience, particularly for applications serving a global audience. When the ui_locales parameter is not included in the authentication request, the Keycloak login screen may appear in a language that the user does not understand. This can lead to confusion, frustration, and a perception of poor application quality. In scenarios where users are accustomed to interacting with applications in their native language, a non-localized login screen can create a jarring and unprofessional experience. This issue is especially critical for applications targeting multilingual user bases, where localization is a key factor in user satisfaction and engagement.

Compliance and Accessibility Concerns

In addition to user experience, the bug can also raise compliance and accessibility concerns. Many regions have regulations and guidelines mandating that applications provide content in the user's preferred language. Failure to do so can result in legal and regulatory issues. Furthermore, providing a localized experience is a crucial aspect of web accessibility. Users with disabilities, such as visual impairments, may rely on screen readers and other assistive technologies that function optimally when content is properly localized. By neglecting to include the ui_locales parameter, applications risk non-compliance with accessibility standards and potentially alienating a significant portion of their user base.

Development and Maintenance Overhead

The bug also introduces additional development and maintenance overhead. Developers may need to implement workarounds to ensure proper localization, adding complexity to the codebase and increasing the risk of introducing new issues. For example, developers might attempt to manually construct the ui_locales parameter and append it to the authentication URL, which is a fragile and error-prone approach. Maintaining these workarounds can become a burden over time, especially as the Keycloak JS adapter evolves and receives updates. A proper fix for the bug would streamline the development process and reduce the long-term maintenance costs.

Conclusion

In conclusion, the bug in the Keycloak JS adapter, where the ui_locales parameter is missing when using onLoad: 'check-sso, is a critical issue that impacts user experience, compliance, and development efforts. The absence of the ui_locales parameter prevents the Keycloak login screen from being displayed in the user's preferred language, leading to confusion and frustration. This behavior contradicts the OpenID Connect (OIDC) 1.0 specification and creates an inconsistent experience compared to the onLoad: 'login-required' option, where the parameter is correctly included. Reproducing the bug involves initializing the Keycloak adapter with check-sso and a specified locale, then observing the missing ui_locales parameter in the authentication request. The implications of this bug extend beyond mere inconvenience, potentially affecting compliance with accessibility standards and increasing development overhead due to the need for workarounds. Addressing this bug is essential for ensuring that applications using Keycloak can provide a seamless, localized, and user-friendly authentication experience. A comprehensive solution would involve modifying the keycloak-js adapter to consistently include the ui_locales parameter in all authentication requests, regardless of the onLoad option, thereby aligning with the OIDC specification and best practices for internationalization.