Client Authentication Support

Client Credentials

Authenticate using client_secret_basic

Client Authentication with HTTP Basic is supported out of the box and no customization is necessary to enable it. The default implementation is provided by DefaultOAuth2TokenRequestHeadersConverter.spring-doc.cn

Given the following Spring Boot properties for an OAuth 2.0 client registration:spring-doc.cn

spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: client-id
            client-secret: client-secret
            client-authentication-method: client_secret_basic
            authorization-grant-type: authorization_code
            ...

The following example shows how to configure WebClientReactiveAuthorizationCodeTokenResponseClient to disable URL encoding of the client credentials:spring-doc.cn

DefaultOAuth2TokenRequestHeadersConverter<OAuth2AuthorizationCodeGrantRequest> headersConverter =
		new DefaultOAuth2TokenRequestHeadersConverter<>();
headersConverter.setEncodeClientCredentials(false);

WebClientReactiveAuthorizationCodeTokenResponseClient tokenResponseClient =
		new WebClientReactiveAuthorizationCodeTokenResponseClient();
tokenResponseClient.setHeadersConverter(headersConverter);
val headersConverter = DefaultOAuth2TokenRequestHeadersConverter<OAuth2AuthorizationCodeGrantRequest>()
headersConverter.setEncodeClientCredentials(false)

val tokenResponseClient = WebClientReactiveAuthorizationCodeTokenResponseClient()
tokenResponseClient.setHeadersConverter(headersConverter)

Authenticate using client_secret_post

Client Authentication with client credentials included in the request-body is supported out of the box and no customization is necessary to enable it.spring-doc.cn

The following Spring Boot properties for an OAuth 2.0 client registration demonstrate the configuration:spring-doc.cn

spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: client-id
            client-secret: client-secret
            client-authentication-method: client_secret_post
            authorization-grant-type: authorization_code
            ...

JWT Bearer

Please refer to JSON Web Token (JWT) Profile for OAuth 2.0 Client Authentication and Authorization Grants for further details on JWT Bearer Client Authentication.spring-doc.cn

The default implementation for JWT Bearer Client Authentication is NimbusJwtClientAuthenticationParametersConverter, which is a Converter that customizes the Token Request parameters by adding a signed JSON Web Token (JWS) in the client_assertion parameter.spring-doc.cn

The java.security.PrivateKey or javax.crypto.SecretKey used for signing the JWS is supplied by the com.nimbusds.jose.jwk.JWK resolver associated with NimbusJwtClientAuthenticationParametersConverter.spring-doc.cn

Authenticate using private_key_jwt

Given the following Spring Boot properties for an OAuth 2.0 Client registration:spring-doc.cn

spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-authentication-method: private_key_jwt
            authorization-grant-type: authorization_code
            ...

The following example shows how to configure WebClientReactiveAuthorizationCodeTokenResponseClient:spring-doc.cn

Function<ClientRegistration, JWK> jwkResolver = (clientRegistration) -> {
	if (clientRegistration.getClientAuthenticationMethod().equals(ClientAuthenticationMethod.PRIVATE_KEY_JWT)) {
		// Assuming RSA key type
		RSAPublicKey publicKey = ...
		RSAPrivateKey privateKey = ...
		return new RSAKey.Builder(publicKey)
				.privateKey(privateKey)
				.keyID(UUID.randomUUID().toString())
				.build();
	}
	return null;
};

WebClientReactiveAuthorizationCodeTokenResponseClient tokenResponseClient =
		new WebClientReactiveAuthorizationCodeTokenResponseClient();
tokenResponseClient.addParametersConverter(
		new NimbusJwtClientAuthenticationParametersConverter<>(jwkResolver));
val jwkResolver: Function<ClientRegistration, JWK> =
    Function<ClientRegistration, JWK> { clientRegistration ->
        if (clientRegistration.clientAuthenticationMethod.equals(ClientAuthenticationMethod.PRIVATE_KEY_JWT)) {
            // Assuming RSA key type
            var publicKey: RSAPublicKey = ...
            var privateKey: RSAPrivateKey = ...
            RSAKey.Builder(publicKey)
                    .privateKey(privateKey)
                    .keyID(UUID.randomUUID().toString())
                .build()
        }
        null
    }

val tokenResponseClient = WebClientReactiveAuthorizationCodeTokenResponseClient()
tokenResponseClient.addParametersConverter(
    NimbusJwtClientAuthenticationParametersConverter(jwkResolver)
)

Authenticate using client_secret_jwt

Given the following Spring Boot properties for an OAuth 2.0 Client registration:spring-doc.cn

spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            client-authentication-method: client_secret_jwt
            authorization-grant-type: client_credentials
            ...

The following example shows how to configure WebClientReactiveClientCredentialsTokenResponseClient:spring-doc.cn

Function<ClientRegistration, JWK> jwkResolver = (clientRegistration) -> {
	if (clientRegistration.getClientAuthenticationMethod().equals(ClientAuthenticationMethod.CLIENT_SECRET_JWT)) {
		SecretKeySpec secretKey = new SecretKeySpec(
				clientRegistration.getClientSecret().getBytes(StandardCharsets.UTF_8),
				"HmacSHA256");
		return new OctetSequenceKey.Builder(secretKey)
				.keyID(UUID.randomUUID().toString())
				.build();
	}
	return null;
};

WebClientReactiveClientCredentialsTokenResponseClient tokenResponseClient =
		new WebClientReactiveClientCredentialsTokenResponseClient();
tokenResponseClient.addParametersConverter(
		new NimbusJwtClientAuthenticationParametersConverter<>(jwkResolver));
val jwkResolver = Function<ClientRegistration, JWK?> { clientRegistration: ClientRegistration ->
    if (clientRegistration.clientAuthenticationMethod == ClientAuthenticationMethod.CLIENT_SECRET_JWT) {
        val secretKey = SecretKeySpec(
            clientRegistration.clientSecret.toByteArray(StandardCharsets.UTF_8),
            "HmacSHA256"
        )
        OctetSequenceKey.Builder(secretKey)
            .keyID(UUID.randomUUID().toString())
            .build()
    }
    null
}

val tokenResponseClient = WebClientReactiveClientCredentialsTokenResponseClient()
tokenResponseClient.addParametersConverter(
    NimbusJwtClientAuthenticationParametersConverter(jwkResolver)
)

Customizing the JWT assertion

The JWT produced by NimbusJwtClientAuthenticationParametersConverter contains the iss, sub, aud, jti, iat and exp claims by default. You can customize the headers and/or claims by providing a Consumer<NimbusJwtClientAuthenticationParametersConverter.JwtClientAuthenticationContext<T>> to setJwtClientAssertionCustomizer(). The following example shows how to customize claims of the JWT:spring-doc.cn

Function<ClientRegistration, JWK> jwkResolver = ...

NimbusJwtClientAuthenticationParametersConverter<OAuth2ClientCredentialsGrantRequest> converter =
		new NimbusJwtClientAuthenticationParametersConverter<>(jwkResolver);
converter.setJwtClientAssertionCustomizer((context) -> {
	context.getHeaders().header("custom-header", "header-value");
	context.getClaims().claim("custom-claim", "claim-value");
});
val jwkResolver = ...

val converter: NimbusJwtClientAuthenticationParametersConverter<OAuth2ClientCredentialsGrantRequest> =
    NimbusJwtClientAuthenticationParametersConverter(jwkResolver)
converter.setJwtClientAssertionCustomizer { context ->
    context.headers.header("custom-header", "header-value")
    context.claims.claim("custom-claim", "claim-value")
}

Public Authentication

Public Client Authentication is supported out of the box and no customization is necessary to enable it.spring-doc.cn

The following Spring Boot properties for an OAuth 2.0 client registration demonstrate the configuration:spring-doc.cn

spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: client-id
            client-authentication-method: none
            authorization-grant-type: authorization_code
            ...

Public Clients are supported using Proof Key for Code Exchange (PKCE). PKCE will automatically be used when client-authentication-method is set to "none" (ClientAuthenticationMethod.NONE).spring-doc.cn