Programmatically: How to create custom Magento REST API authentication

Step 1: Create a new module

Create a new directory for your module in app/code and create the following files: ModuleName.xml (in app/code/ModuleName/etc) Module.php (in app/code/ModuleName/Module.php) etc/api.xml (in app/code/ModuleName/etc/api.xml) etc/auth.xml (in app/code/ModuleName/etc/auth.xml)

Step 2: Configure the module

In ModuleName.xml, add the following code:

	<?xml version="1.0"?>
	<config>
		<modules>
			<ModuleName>
				<codePool>local</codePool>
				<version>1.0.0</version>
			</ModuleName>
		</modules>
	</config>
	

Step 3: Create the API

In etc/api.xml, add the following code:

    <?xml version="1.0"?>
    <api>
        <resources>
            <resource alias="moduleName" />
        </resources>
        <acl>
            <resources>
                <resource alias="moduleName" />
            </resources>
        </acl>
    </api>
	

Step 4: Implement the authentication logic

In Module.php, add the following code:

	use Magento\Framework\REST\AuthenticationInterface;
	use Magento\Framework\REST\AuthenticationInterfaceFactory;
	use Magento\Framework\HTTP\Header;

	class Module extends \Magento\Framework AppModule
   {
    // ...

    public function getAuthentication()
    {
        $auth = new \ModuleName\Auth();
        return $auth;
    }
   }
	

Step 5: Create the authentication class

In etc/auth.xml, add the following code:

    <?xml version="1.0"?>
    <config>
        <modules>
            <ModuleName_auth>
                <active>true</active>
                <class>Module_NameAuth</class>
            </ModuleName_auth>
        </modules>
    </config>
	

In Module/Auth.php, add the following code:

	class Module\Auth implements AuthenticationInterface
    {
    public function authenticate($username, $password)
    {
        // Custom authentication logic here
        // For example, you could check against a custom database table or a external service
        if ($username === 'myuser' && $password === 'mypassword') {
            return new \stdClass();
        }
        return null;
    }
   }
	

Step 6: Register the authentication class

In Module.php, add the following code:

		public function registerAuthentication()
  {
    $this->getAuthenticationInterfaceFactory()->register('moduleName', 'Module_NameAuth');
  }
	

Step 7: Test the authentication

To test the authentication, you can use a tool like curl or a REST client like Postman. Send a request to http://your-magento-url/index.php/rest/V1/integration/customer/token with the following headers:

Authorization: Bearer YOUR_API_KEY Content-Type: application/json

And in the request body, provide the following JSON:

		{
    "username": "myuser",
    "password": "mypassword"
	   }