OAuth 2.0 is an industry-standard protocol for authorization that provides secure, delegated access to server resources without exposing user credentials. One of the key features of OAuth 2.0 is the Refresh Token, which enables a client to maintain access to resources without repeatedly prompting the user for authentication.
In this article, we'll dive into the concept of refresh tokens in PingFederate, explore their use cases, and provide examples to demonstrate how they work in real-world applications.
What is a Refresh Token?
A Refresh Token is a long-lived token used to obtain new access tokens after the original access token expires. Access tokens, which are typically short-lived, grant access to protected resources. When an access token expires, the refresh token is exchanged for a new one without requiring the user to authenticate again.
Why Use Refresh Tokens?
- Enhance User Experience: Users don’t have to log in again every time an access token expires.
- Security: Access tokens are short-lived, reducing the risk of misuse, while the refresh token ensures a secure, seamless user session.
- Delegated Access: Ideal for long-term sessions, such as applications running in the background, where continuous access to resources is required.
How Refresh Tokens Work in PingFederate
When an OAuth 2.0 access token expires, the client can use the refresh token to obtain a new access token without requiring the user to re-authenticate.
Token Flow with Refresh Token:
Initial Authorization:
- The client requests authorization, typically using an Authorization Code Grant or Resource Owner Password Credentials (ROPC) Grant.
- Once authenticated, PingFederate issues an access token and a refresh token.
Access Token Expiry:
- The access token is short-lived (e.g., 30 minutes to 1 hour).
- When the access token expires, the client can no longer access protected resources.
Use Refresh Token to Get New Access Token:
- Instead of asking the user to authenticate again, the client sends a token refresh request using the refresh token.
- PingFederate validates the refresh token and issues a new access token (and optionally, a new refresh token).
New Access Token Granted:
- The client receives the new access token, which it can use to access protected resources without interrupting the user session.
Example of Refresh Token Flow in PingFederate
Here’s an example of how the refresh token process works using the Authorization Code Grant type:
Step 1: Initial Authorization Request
The client sends the user to PingFederate's authorization endpoint:
httpGET /as/authorization.oauth2?response_type=code&client_id=client_id&redirect_uri=https://client-app/callback&scope=openid profile offline_access HTTP/1.1 Host: pingfederate-server.com
Step 2: Authorization Code Response
PingFederate authenticates the user and redirects back with an authorization code:
httphttps://client-app/callback?code=authorization_code
Step 3: Token Request
The client exchanges the authorization code for access and refresh tokens:
httpPOST /as/token.oauth2 HTTP/1.1 Host: pingfederate-server.com Authorization: Basic Base64(client_id:client_secret) Content-Type: application/x-www-form-urlencoded grant_type=authorization_code& code=authorization_code& redirect_uri=https://client-app/callback
Step 4: Token Response
PingFederate responds with an access token and a refresh token:
json
{
"access_token": "eyJhbGci...",
"refresh_token": "OXP0ZA...",
"expires_in": 3600,
"token_type": "Bearer"
}
Step 5: Access Token Expiry & Token Refresh Request
When the access token expires, the client uses the refresh token to obtain a new access token:
httpPOST /as/token.oauth2 HTTP/1.1 Host: pingfederate-server.com Authorization: Basic Base64(client_id:client_secret) Content-Type: application/x-www-form-urlencoded grant_type=refresh_token& refresh_token=OXP0ZA...
Step 6: New Token Response
PingFederate responds with a new access token:
json
{
"access_token": "new_access_token...",
"expires_in": 3600,
"token_type": "Bearer"
}
Use Cases for Refresh Tokens in PingFederate
1. Mobile Applications
Mobile apps frequently use refresh tokens because they often need to maintain long-term access to APIs. The refresh token can ensure continuous access without requiring the user to repeatedly log in.
2. Web Applications with Long Sessions
For web applications, refresh tokens allow for a seamless user experience, even after the user’s initial access token expires. For example, a user might stay logged in to a website for several hours or days, and refresh tokens allow the site to issue new access tokens in the background.
3. Background Processes and API Integration
In systems where backend services or APIs need to access resources on behalf of a user, refresh tokens can ensure that the application can continue working even after the access token has expired. This is especially useful for long-running processes or scheduled tasks.
Security Considerations for Refresh Tokens
While refresh tokens provide significant advantages, they also introduce certain security risks. Here are some best practices to mitigate these risks:
1. Secure Storage of Refresh Tokens
Refresh tokens should be stored securely. For example:
- Mobile apps: Use encrypted storage mechanisms such as the iOS Keychain or Android Keystore.
- Web applications: Store tokens in HTTP-only, secure cookies to prevent access by JavaScript.
2. Token Expiry and Revocation
- Set an appropriate expiration time for refresh tokens to limit potential misuse if they are compromised.
- Use PingFederate's token revocation endpoint to invalidate refresh tokens when a user logs out or if the token is no longer needed.
3. Use of scope=offline_access
Ensure that your OAuth clients request the offline_access scope when requesting refresh tokens. Without this scope, PingFederate will not issue a refresh token.
4. Refresh Token Rotation
PingFederate can issue a new refresh token every time a refresh token is used. This reduces the risk of token reuse attacks. If an attacker gets access to an old refresh token, it will no longer be valid after it is used once.
Conclusion
Refresh tokens in PingFederate are a powerful feature of OAuth 2.0 that improve the user experience by allowing long-lived sessions without re-authentication. By following security best practices and leveraging PingFederate’s advanced features, organizations can implement secure and seamless access management in their applications.
With real-world use cases like mobile applications, web apps, and background processes, refresh tokens offer a practical solution for extending access while maintaining security. Understanding how to properly configure, manage, and secure refresh tokens in PingFederate is key to building robust OAuth 2.0 systems.
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