Single Sign-Out (SSO Logout)

Introduction

Single Sign-Out (SSO Logout) is a feature that allows you to log a user out from all applications in an organization simultaneously. When a user logs out from one application, they are automatically logged out from all other applications that are part of the same SSO ecosystem.

This is particularly useful in scenarios such as:

Security incidents: Immediately terminate all active sessions when a security breach is detected
Organization-wide logout policies: Enforce logout across all services when users leave the organization or change roles
Compliance requirements: Ensure users are completely logged out from all systems when required by regulations
User-initiated logout: Allow users to log out from all applications with a single action

How SSO Logout Works

Casdoor supports two logout modes controlled by the logoutAll parameter:

Full SSO Logout (default, when logoutAll=true or not specified):

Delete all active sessions: All active sessions for the user across all applications in the organization are terminated
Expire all access tokens: All access tokens that were issued to the user are immediately invalidated
Clear the current session: The user's current session and authentication state are cleared
Send logout notifications: Notification providers receive the logout event with all session IDs and token hashes

This ensures that the user is completely logged out from all integrated applications and cannot access any resources without re-authenticating.

Session-Level Logout (when logoutAll=false):

Delete current session: Only the current session is terminated
Clear current authentication state: The user's current session and token are cleared
Send targeted notification: Notification providers receive the logout event with only the current session ID

This allows users to logout from a specific device or browser while remaining logged in on other sessions. This is useful when users share accounts across multiple devices or have concurrent sessions they want to manage individually.

Logout Notifications

When SSO logout occurs, Casdoor automatically notifies all notification providers configured in the application where the user registered. The notifications now include session-level information and cryptographic signatures for security.

Each notification provider receives a POST request with the following payload:

{
  "owner": "org-name",
  "name": "username",
  "displayName": "John Doe",
  "email": "user@example.com",
  "phone": "+1234567890",
  "id": "user-id",
  "event": "sso-logout",
  "sessionIds": ["session-123", "session-456"],
  "accessTokenHashes": ["hash-abc", "hash-def"],
  "nonce": "random-nonce-xyz",
  "timestamp": 1699900000,
  "signature": "hmac-sha256-signature"
}

New security fields:

sessionIds: List of session IDs being logged out (enables targeted session invalidation)
accessTokenHashes: Hashes of access tokens being expired (helps identify specific tokens to revoke)
nonce: Random value for replay attack protection
timestamp: Unix timestamp when the notification was generated
signature: HMAC-SHA256 signature computed using the application's client secret

Verifying Logout Notifications

To prevent malicious logout requests, you should verify the signature of incoming logout notifications:

// Example verification in Go
func verifyLogoutNotification(notification *SsoLogoutNotification, clientSecret string) bool {
    data := fmt.Sprintf("%s|%s|%s|%d|%s|%s",
        notification.Owner,
        notification.Name,
        notification.Nonce,
        notification.Timestamp,
        strings.Join(notification.SessionIds, ","),
        strings.Join(notification.AccessTokenHashes, ","))
    
    expectedSignature := hmacSHA256(clientSecret, data)
    return notification.Signature == expectedSignature
}

// Example verification in JavaScript
const crypto = require('crypto');

function verifyLogoutNotification(notification, clientSecret) {
  const data = `${notification.owner}|${notification.name}|${notification.nonce}|${notification.timestamp}|${notification.sessionIds.join(',')}|${notification.accessTokenHashes.join(',')}`;
  
  const expectedSignature = crypto
    .createHmac('sha256', clientSecret)
    .update(data)
    .digest('hex');
  
  return notification.signature === expectedSignature;
}

Configuration

To receive logout notifications, configure a notification provider (such as Custom HTTP, Telegram, or Slack) in your Casdoor application's notification provider settings. For Custom HTTP providers:

Set Receiver to your application's webhook endpoint (e.g., https://app.example.com/api/logout-webhook)
Set Method to POST
Set Title to content (the parameter name for the JSON payload)

Your application can then verify the signature, check the timestamp to prevent replay attacks, and use the session IDs and token hashes to perform targeted logout operations. For more details on configuring notification providers, see the Notification Providers documentation.

SSO Logout API

Endpoint

GET or POST /api/sso-logout?logoutAll=<true|false>

The SSO logout endpoint accepts both GET and POST requests, making it flexible for different integration scenarios.

Parameters

logoutAll (optional): Controls logout scope. Accepts true, 1, or empty string (default: true for backward compatibility)
- true or 1 or empty: Logout from all sessions across all applications
- Any other value (e.g., false, 0): Logout from current session only

Authentication

This endpoint requires the user to be authenticated. You can use any of the authentication methods supported by Casdoor:

Access token: Include the access token in the Authorization header
Session cookie: Use the session cookie that was set during login
Client credentials: Use the application's client ID and secret for machine-to-machine scenarios

For more details on authentication methods, see the Casdoor Public API documentation.

Request Examples

Logout from All Sessions (Default)

curl -X POST https://door.casdoor.com/api/sso-logout \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN"

# Or explicitly specify logoutAll=true
curl -X POST "https://door.casdoor.com/api/sso-logout?logoutAll=true" \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN"

Logout from Current Session Only

curl -X POST "https://door.casdoor.com/api/sso-logout?logoutAll=false" \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN"

curl -X POST https://door.casdoor.com/api/sso-logout \
  --cookie "casdoor_session_id=abc123def456"

Using JavaScript Fetch API

// Logout from all sessions
fetch('https://door.casdoor.com/api/sso-logout', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${accessToken}`
  },
  credentials: 'include'
})
  .then(response => response.json())
  .then(data => {
    console.log('Logout successful:', data);
    window.location.href = '/login';
  })
  .catch(error => {
    console.error('Logout failed:', error);
  });

// Logout from current session only
fetch('https://door.casdoor.com/api/sso-logout?logoutAll=false', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${accessToken}`
  },
  credentials: 'include'
})
  .then(response => response.json())
  .then(data => {
    console.log('Logged out from current session:', data);
    window.location.href = '/login';
  });

Response

The API returns a standard Casdoor response:

{
  "status": "ok",
  "msg": "",
  "data": ""
}

Response Fields:

status: Indicates whether the operation was successful ("ok") or failed ("error")
msg: Contains an error message if the operation failed, otherwise empty
data: Additional data returned by the API, typically empty for logout operations

Implementing SSO Logout in Your Application

Using Casdoor SDKs

Most Casdoor SDKs provide built-in support for SSO logout. Here are examples for different platforms:

Go SDK

import "github.com/casdoor/casdoor-go-sdk/casdoorsdk"

func logout(w http.ResponseWriter, r *http.Request) {
    // Get the access token from the session or request
    token := getAccessTokenFromSession(r)
    
    // Call the SSO logout endpoint
    err := casdoorsdk.Logout(token)
    if err != nil {
        http.Error(w, "Logout failed", http.StatusInternalServerError)
        return
    }
    
    // Clear local session
    clearSession(w, r)
    
    // Redirect to login page
    http.Redirect(w, r, "/login", http.StatusFound)
}

JavaScript SDK

import Sdk from "casdoor-js-sdk";

const CasdoorSDK = new Sdk({
  serverUrl: "https://door.casdoor.com",
  clientId: "YOUR_CLIENT_ID",
  appName: "YOUR_APP_NAME",
  organizationName: "YOUR_ORG_NAME",
});

async function handleLogout() {
  try {
    // Call the SSO logout endpoint
    await CasdoorSDK.logout();
    
    // Clear local state
    localStorage.removeItem('casdoor_token');
    sessionStorage.clear();
    
    // Redirect to login page
    window.location.href = '/login';
  } catch (error) {
    console.error('Logout failed:', error);
  }
}

Python SDK

from casdoor import CasdoorSDK

sdk = CasdoorSDK(
    endpoint="https://door.casdoor.com",
    client_id="YOUR_CLIENT_ID",
    client_secret="YOUR_CLIENT_SECRET",
    certificate="YOUR_CERT",
    org_name="YOUR_ORG_NAME",
    app_name="YOUR_APP_NAME",
)

def logout(access_token):
    try:
        # Call the SSO logout endpoint
        result = sdk.logout(access_token)
        
        if result['status'] == 'ok':
            # Clear local session
            clear_session()
            return True
        else:
            print(f"Logout failed: {result['msg']}")
            return False
    except Exception as e:
        print(f"Logout error: {e}")
        return False

Manual Implementation

If you're not using a Casdoor SDK, you can implement SSO logout manually by making an HTTP request to the logout endpoint:

async function logout() {
  const accessToken = localStorage.getItem('access_token');
  
  try {
    // Use the full Casdoor server URL in your application
    const response = await fetch('https://door.casdoor.com/api/sso-logout', {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${accessToken}`,
        'Content-Type': 'application/json'
      },
      credentials: 'include'
    });
    
    const result = await response.json();
    
    if (result.status === 'ok') {
      // Clear local storage
      localStorage.removeItem('access_token');
      localStorage.removeItem('user_info');
      sessionStorage.clear();
      
      // Redirect to login page
      window.location.href = '/login';
    } else {
      console.error('Logout failed:', result.msg);
    }
  } catch (error) {
    console.error('Logout error:', error);
  }
}

Best Practices

1. Clear Local State

After calling the SSO logout endpoint, make sure to clear all local authentication state:

Remove access tokens from local storage or session storage
Clear any cached user information
Invalidate any local session cookies
Reset application state to the logged-out state

2. Handle Logout Errors Gracefully

Even if the SSO logout endpoint fails, you should still clear local authentication state to ensure the user appears logged out from your application:

async function logout() {
  try {
    await callSSOLogout();
  } catch (error) {
    console.error('SSO logout failed, clearing local state anyway:', error);
  } finally {
    // Always clear local state
    clearLocalAuthenticationState();
    redirectToLogin();
  }
}

3. Provide User Feedback

Give users clear feedback about the logout process:

async function logout() {
  // Show loading indicator
  showLoadingIndicator('Logging out...');
  
  try {
    await callSSOLogout();
    showSuccessMessage('Logged out successfully');
  } catch (error) {
    showErrorMessage('Logout failed, but you have been logged out locally');
  } finally {
    clearLocalAuthenticationState();
    // Redirect after a short delay to allow users to see the message
    setTimeout(() => redirectToLogin(), 1000);
  }
}

4. Implement Logout Timeout

Set a reasonable timeout for the logout request to prevent users from waiting indefinitely:

async function logout() {
  const timeout = 5000; // 5 seconds
  
  try {
    await Promise.race([
      callSSOLogout(),
      new Promise((_, reject) => 
        setTimeout(() => reject(new Error('Logout timeout')), timeout)
      )
    ]);
  } catch (error) {
    console.error('Logout error:', error);
  } finally {
    clearLocalAuthenticationState();
    redirectToLogin();
  }
}

Security Considerations

1. Verify Logout Notification Signatures

Always verify the HMAC-SHA256 signature of logout notifications to prevent malicious logout requests. The signature is computed using your application's client secret and includes all critical fields (owner, name, nonce, timestamp, sessionIds, accessTokenHashes). Reject any notification with an invalid signature.

2. Check Notification Timestamp

Implement timestamp validation to prevent replay attacks. Reject notifications that are too old (e.g., more than 5 minutes old):

function isNotificationValid(notification) {
  const maxAge = 5 * 60 * 1000; // 5 minutes in milliseconds
  const now = Date.now();
  const notificationTime = notification.timestamp * 1000; // Convert to milliseconds
  
  if (now - notificationTime > maxAge) {
    console.error('Notification is too old, possible replay attack');
    return false;
  }
  
  return verifyLogoutNotification(notification, clientSecret);
}

3. Secure Communication

Always use HTTPS when calling the SSO logout endpoint to prevent token interception:

// ✅ Good: Uses HTTPS
const logoutUrl = 'https://door.casdoor.com/api/sso-logout';

// ❌ Bad: Uses HTTP (insecure)
const logoutUrl = 'http://door.casdoor.com/api/sso-logout';

4. Token Validation

Casdoor validates the access token before processing the logout request. Ensure your token is valid and has not expired before making the logout call.

5. CSRF Protection

When using session cookies for authentication, ensure CSRF protection is enabled to prevent unauthorized logout requests:

// Include CSRF token in the request headers
// Replace with your actual Casdoor server URL
fetch('https://door.casdoor.com/api/sso-logout', {
  method: 'POST',
  headers: {
    'X-CSRF-Token': getCsrfToken()
  },
  credentials: 'include'
});

6. Protect Client Secrets

Keep your application's client secret secure. It's used to sign logout notifications, so if compromised, attackers could forge valid logout requests. Store it securely (e.g., in environment variables or secret management systems) and never expose it in client-side code.

7. Audit Logging

Consider logging logout events for security auditing and compliance:

func logout(userID string, token string) error {
    // Call SSO logout
    err := casdoorsdk.Logout(token)
    
    // Log the logout event
    auditLog.Info(map[string]interface{}{
        "event": "sso_logout",
        "user_id": userID,
        "timestamp": time.Now(),
        "success": err == nil,
    })
    
    return err
}

Troubleshooting

Logout Not Working Across All Applications

If users remain logged in to some applications after SSO logout:

Verify application integration: Ensure all applications are properly integrated with Casdoor and use the same organization
Check token validation: Make sure all applications validate tokens on each request
Review session management: Applications should not rely solely on local sessions; they must validate tokens with Casdoor

Token Still Valid After Logout

If access tokens remain valid after logout:

Verify the logout endpoint: Ensure you're calling the correct endpoint (/api/sso-logout)
Check authentication: Make sure you're sending valid authentication credentials with the logout request
Review token caching: Ensure applications don't cache token validation results

Logout Endpoint Returns Error

Common error scenarios:

401 Unauthorized: The access token is invalid or expired. Clear local state and redirect to login.
403 Forbidden: The user doesn't have permission to logout. This is rare and may indicate a configuration issue.
500 Internal Server Error: Server-side error. Log the error and clear local state anyway.

async function logout() {
  try {
    // Replace with your actual Casdoor server URL
    const response = await fetch('https://door.casdoor.com/api/sso-logout', {
      method: 'POST',
      headers: { 'Authorization': `Bearer ${token}` }
    });
    
    if (!response.ok) {
      console.error(`Logout failed with status: ${response.status}`);
      // Clear local state anyway
    }
  } catch (error) {
    console.error('Logout error:', error);
  } finally {
    clearLocalAuthenticationState();
    redirectToLogin();
  }
}

Single Sign-On (SSO): Learn how to enable SSO for your applications
Casdoor Public API: Complete API reference including authentication methods
Tokens: Understand how Casdoor manages access tokens and sessions
OAuth 2.0: Learn about OAuth 2.0 flows supported by Casdoor

Introduction​

How SSO Logout Works​

Logout Notifications​

Verifying Logout Notifications​

Configuration​

SSO Logout API​

Endpoint​

Parameters​

Authentication​

Request Examples​

Logout from All Sessions (Default)​

Logout from Current Session Only​

Using Session Cookie​

Using JavaScript Fetch API​

Response​

Implementing SSO Logout in Your Application​

Using Casdoor SDKs​

Go SDK​

JavaScript SDK​

Python SDK​

Manual Implementation​

Best Practices​

1. Clear Local State​

2. Handle Logout Errors Gracefully​

3. Provide User Feedback​

4. Implement Logout Timeout​

Security Considerations​

1. Verify Logout Notification Signatures​

2. Check Notification Timestamp​

3. Secure Communication​

4. Token Validation​

5. CSRF Protection​

6. Protect Client Secrets​

7. Audit Logging​

Troubleshooting​

Logout Not Working Across All Applications​

Token Still Valid After Logout​

Logout Endpoint Returns Error​

Related Documentation​