What's the Client_Credentials grant type?

Posted 2023-03-30 Chuck Lu

What\'s the Client_Credentials grant type?

The Client Credentials grant type is a type of OAuth2 authentication flow that enables a client to authenticate with a server using its own credentials, rather than on behalf of a user.

In this flow, the client sends its own credentials (usually a client ID and a client secret) to the authorization server to obtain an access token. The access token can then be used to access protected resources on behalf of the client itself.

This grant type is typically used for machine-to-machine (M2M) authentication scenarios where there is no user involved. Examples of such scenarios include API-to-API communication, background tasks, and server-to-server communication.

 

When will the token expire after get it through Client Credentials flow?

The expiration time of the access token obtained through the Client Credentials grant type is determined by the authorization server. Typically, the token is valid for a fixed period of time, such as 1 hour or 24 hours, depending on the configuration of the authorization server. You can find the expiration time of the token in the "expires_in" field of the token response. It is recommended to always check the expiration time of the token and obtain a new token using the Client Credentials flow before the current token expires, to ensure uninterrupted access to the protected resources.

 

 

What if I get a new access token every time I need to access the resources?

Getting a new access token every time you need to access a resource is a valid approach. In fact, many API clients and applications use this approach. However, it may be less efficient than using a token that has a longer lifespan, since acquiring a new access token requires making an HTTP request to the authorization server. Additionally, some authorization servers may limit the number of access token requests that can be made within a certain time period, which could result in rate limiting or throttling.

Therefore, it is usually recommended to use access tokens with a longer lifespan if possible, and to refresh them using a refresh token when they expire. This can help reduce the number of requests made to the authorization server and improve performance. However, it is important to balance the need for security and efficiency with the requirements of your specific use case.

 

 

Is there a limitation for such kind of token on azure ad?

 

Yes, there are certain limitations on Azure AD tokens, including those obtained through the Client Credentials flow. Specifically, Azure AD Access Tokens have a maximum lifetime of 1 hour by default, and can be configured for a maximum of up to 24 hours. Refresh Tokens obtained through the OAuth 2.0 protocol have a maximum lifetime of 90 days by default, but this can also be configured. Additionally, there are limits on the number of access tokens that can be issued for a given application or user within a specific timeframe to prevent abuse and limit exposure in case of a breach. It is important to design your token management strategy accordingly and ensure that you are adhering to best practices for securing access tokens.