WordPress REST API OAuth 2.0 Authentication Method

OAuth 2.0 is the most opted method for authenticating access to the APIs. OAuth 2.0 allows authorization without the need providing user's email address or password to external application. This method of WordPress REST API OAuth 2.0 Authentication involves the use of OAuth 2.0 protocol flow to obtain the security access token or id token (JWT token) and that token will be used to authenticate the WordPress REST API endpoints. Each time a request to access the WordPress REST API endpoint will be made, the authentication will be done against that access token/id token (JWT token), and on the basis of the verification of that API Bearer token, the resources for that API request will be allowed to access.

The token provided using the OAuth 2.0 Authentication Method is highly encrypted and secure, hence security is not compromised. It is the most secure method to authenticate/ protect WordPress REST API endpoints. This method is somewhat similar to the JWT authentication method but far more secure due to various benefits of OAuth 2.0 protocol.

Pre-requisites : Download And Installation

• Log into your WordPress instance as an admin.
• Go to the WordPress Dashboard -> Plugins and click on Add New.
• Search for a WordPress REST API Authentication plugin and click on Install Now.
• Once installed click on Activate.

UseCase: Securing REST API with OAuth 2.0 Authentication Method

1. Password Grant:

Use Case: Register WordPress user or Authenticate /login users in external platforms based on WordPress credentials via WordPress REST API

Suppose you have a login form in your application and want to authenticate the user on the basis of their WordPress login credentials, then OAuth 2.0 Authentication in REST API method will help you in achieving that. The plugin provides a WordPress login API. You can easily pass the WordPress credentials of that user to this API and based on the validation, you will receive the authentication and response.
Also, Implementing OAuth 2.0 Authentication in REST API method can also be used to register users in WordPress using the admin credentials of WordPress user. Using the plugin OAuth 2.0 token endpoint, you can pass WordPress user credentials which have administrator capabilities such that token generated will have admin capabilties can be used to perform operations like user registration for which administrative privileges are required. Once you have the token, you can use this token with wordPress ‘/users’ API to register users in WordPress via REST API request.

2. Client Credentials:

Use Case: Authenticate/ protect WordPress REST API Endpoints securely or register users in WordPress without using admin user credentials.

If you want to access the WordPress REST API without passing the WordPress user credentials or want to register the users in WordPress securely without need to pass the admin user credentials of WordPress and instead pass the client credentials provided by the plugin, then this method is the perfect solution such that there won’t be any chance of user credentials getting compromised.
The plugin acts both as a OAuth 2.0 Identity provider(Server) which provides the token and REST APIs authenticator for authentication of these WordPress REST API endpoints on the basis of the token. Hence it provides utmost security to obtain the token and that token can be used to authenticate the REST API request.

• The flow for implementing OAuth 2.0 Authentication method in REST API methods is explained below:

1. The REST API request will be made with appropriate parameters to obtain the token for our plugin. Our plugin will act as an OAuth 2.0 Identity provider and provides the access token.

2. The actual REST API request to access the resource will be made with the access token received from the last step passed in the Authorization header with token type as Bearer. The plugin now acts as Authenticator to authenticate the API on the basis of token validity. If the token is validated successfully then the API requester will be allowed to access the resource else on the failed validation the error response will be returned.

Related Usecase:

• How to login or register users using WordPress REST API?
• How to authenticate WordPress users using the API?

Read Use Cases for the following Rest API Authentication Methods:

Api Key Authentication

JWT Authentication

Basic Authentication

Third Party Provider Authentication

WordPress REST API OAuth 2.0 using Password Grant:

• In the plugin, go to the Configure API Authentication tab and click on OAuth 2.0 Authentication as the API Authentication method.
• Select the OAuth 2.0 grant Type as Password Grant.
• Now you can opt for any of the Token Type as Access Token or JWT Token.
  The Access Token is random string associated with the user for whom it is generated while the JWT Token or id-token is formed as per JWT standard which consits of user detials encoded in it for whom the token is generated. This token can be decoded using its key and the user details can be parsed. Hence this token is recommended in those cased in which user WP profile detials needs to be fetched later on.

• This method provides you with an additional secuirty facility as follows -

1. Refresh Token - You can enable this option if you want to receive the refresh token as well along with access-token or JWT token in the token endpoint request. With this token you can regenerate the access-token/JWT token as they are meant to expire shortly to increase security.

The sample example of regenerating the access token/JWT token from a refresh token using the refresh token grant is explained further below.

2. Revoke Token - You can enable this option if you want to enable the facility to revoke the existing generated access-token/JWT token to make a token as invalid and hence can not be able to authenticate the WP REST APIs further.

• Now click on Save Configuration button to save the OAuth 2.0 authentication settings and enable this authenticate method to secure WordPress REST API endpoints.
• Once you click on the Save Configuration, you will get the Client ID, Client Secret & Token Endpoint (the endpoint to which an API call need to be made to receive the security token).

Now the plugin setup part has been done successfully. Below comes the part in which the actual security access/JWT token will be obtained and used further for accessing the WordPress REST APIs.

• Now, you would need to make two calls:

I : Get the Token

• To get the access token/JWT Token, you would need to make an API Call to OAuth 2.0 Token endpoint provided by our plugin shown as below

Request: POST https://<domain-name>/wp-json/api/v1/token
Body:
grant_type =<password>
&username =<wordpress username>
&password = <wordpress password>
&client_id =<client id>

Sample curl Request Format-
curl -d "grant_type=password&username=<wordpress_username>&password=<wordpress_password>&client_id=<client_id>"
-X POST http://<wp_base_url>/wp-json/api/v1/token

• Using Refresh Token

Request: POST  https://<domain-name>/wp-json/api/v1/token
Body:
grant_type = <refresh_token>
&refresh_token =  <Refresh Token>

Sample curl Request Format-
curl -d "grant_type=refresh_token&refresh_token=<refresh_token>&client_id=<client_id>&client_secret=<client_secret>"
-X POST http://<wp_base_url>/wp-json/api/v1/token

II : Send actual WordPress REST API Request

• Once you get the access_token / id_token (JWT token) using the OAuth 2.0 password grant flow, you can use it to request the access to the WordPress REST API endpoints as shown below.

Request: GET https://<domain-name>/wp-json/wp/v2/posts
Header: Authorization :Bearer <access_token /id_token>

• NOTE: Above token is valid for 1 hour by default. The same token can be used multiple times for multiple REST API requests before its expiration time. Once the token is expired, new token needs to be created to request the WordPress REST API endpoint access.
• Check out the Error Response for OAuth 2.0 using Password Grant.

WordPress REST API OAuth 2.0 using Client Credentials Grant:

• In the plugin, go to the Configure API Authentication tab and click on OAuth 2.0 Authentication as the API Authentication method.
• Now Select the OAuth 2.0 grant Type as Client Credentials Grant.

• Once you click on the save configuration, you will get the Client ID, Client Secret and Token Endpoint.
• Here you would need to make two calls:

I : Get the Token

• After saving above configuration, you will get the Client ID, Client-Secret & Token Endpoint.
• get the token, you need to send a token request as shown below

Request: POST https://<domain-name>/wp-json/api/v1/token
Body:
grant_type = <client_credentials>
&client_id = <client id>
&client_secret = <client secret>

Sample curl Request Format-
curl -d "grant_type=client_credentials&client_id=<client_id>&client_secret=<client_secret>"
-X POST http://<wp_base_url>/wp-json/api/v1/token

• Using Refresh Token

Request: POST https://<domain-name>/wp-json/api/v1/token
Body:
grant_type = <refresh_token>
&refresh_token = <Refresh Token>

Sample curl Request Format-
curl -d "grant_type=refresh_token&refresh_token=<refresh_token>&client_id=<client_id>&client_secret=<client_secret>"
-X POST http://<wp_base_url>/wp-json/api/v1/token

II : Send API Request

• Once you get the access_token / id_token by OAuth 2.0 client credentials, you can use it to request the access to the WordPress REST API endpoint as shown below.

Request: GET https://<domain-name>/wp-json/wp/v2/posts
Header: Authorization : Bearer <access_token /id_token>

• NOTE: Above token is valid for 1 hour by default. The same token can be used multiple times for multiple REST API requests before its expiration time. Once the token is expired, new token needs to be created to request the WordPress REST API endpoint access.
• Check out the Error Response for OAuth 2.0 using Client Credentials Grant.
• Check out the developer documentation for more details.

Postman Samples:

a) OAuth 2.0 password Grant method:

• Sample request to obtain token:
• You can download the postman request sample from here.
• Now extract the zip file and import the extracted json file into the postman application.

• Example

• Sample request format to request resources using the token obtained in the last step.
• You can download the postman request sample from here.
• Now extract the zip file and import the extracted json file into the postman application.

• Example

b) OAuth 2.0 Client Credentials Grant Method:

• Sample request to obtain token:
• You can download the postman request sample from here.
• Now extract the zip file and import the extracted json file into the postman application.

• Example

c) REST API request to obtain the actual resource:

• You can download the postman request sample from here.
• Now extract the zip file and import the extracted json file into the postman application.

• Example

Feature Description

1. Role Based REST API Restriction:

This feature allows restricting the REST API access based on the user roles. You can whitelist the roles for which you want to allow access to the requested resource for the REST APIs. So whenever a REST API request is made by a user, his role will be fetched and only allowed to access the resource if his role is whitelisted.

How to configure it?

• First, go to the plugin ‘Advanced Settings’ tab.
• Then, in the Role based Restriction section, all the roles by default will be allowed to access the APIs. You can enable the checkbox of the roles for which you want to restrict access.

• In the above screenshot, the subscriber role checkbox is enabled. So whenever an API request is made by the user with his role as subscriber then that user won’t be allowed to access the requested resource.

Note: The Role based restriction feature is valid for Basic authentication (Username: password), JWT method, and OAuth 2.0 (Password grant).

2. Custom Header

This feature provides an option to choose a custom header rather than the default ‘Authorization’ header.

It will increase the security as you have the header named with your ‘custom name’, so if someone makes the REST API request with a header as ‘Authorization’ then he won’t be able to access the APIs.

How to configure it?

• First, go to the plugin ‘Advanced Settings’ tab.
• Then in the ‘Custom Header’ section, you can edit the textbox to enter the custom name you want.


3. Exclude REST APIs

This feature allows you to whitelist your REST APIs so these can be accessed directly without any authentication. Hence all these whitelisted REST APIs are publicly available.

How to configure it?

• First, go to the plugin ‘Advanced Settings’ tab.
• Then in the ‘Exclude REST APIs’, you can enter your APIs in the prescribed format which needs to be whitelisted for public access.

• Example: Suppose if you want to exclude the REST API ‘ '<your domain> /wp-json/wp/v2/posts’ then you have to enter ‘/wp/v2/posts’ in the textbox.

4. Custom Token Expiry

This feature is applicable for JWT and OAuth 2.0 methods which uses time based tokens to authenticate the WordPress REST API endpoints. This feature allows you to set the custom expiry for the tokens such that the token will no longer be valid once the token expires.

How to configure it?

• First, go to the plugin ‘Advanced Settings’ tab.
• Then in the ‘Token Expiry Configuration’ section, the access token validity and refresh token(used for OAuth 2.0 method) can be altered. By default the access token expiry time is set to 60 minutes and the refresh token expiry time is set to 14 days. Hence with this feature, the expiry can be adjusted accordingly as per the requirements.