SslBundle integration with FeignClients

Recently, in spring-boot 3.1, spring team introduced the SslBundles component as a convenient way to configure SSL connection to RestTemplate and RestClient.

As reference: https://spring.io/blog/2023/06/07/securing-spring-boot-applications-with-ssl

I similar approach would be interesting to exist in the spring-cloud-openfeign.

I am currently taking the following approach:

application.yml

spring:
 ssl:
   bundle:
     jks:
       secure-service:
         key:
           alias: "secure-service"
         keystore:
           location: "classpath:keystore.p12"
           password: "myStrongPassword"
           type: "PKCS12"

    @Bean
    @ConditionalOnProperty(prefix = "spring.ssl.bundle.jks.secure-service.key", name = "alias")
    public Client feignClient(SslBundles sslBundles) throws Exception {
        // "secure-service" is defined in application properties
        try {
            SslBundle sslBundle = sslBundles.getBundle("secure-service");
            SSLContext sslContext = sslBundle.createSslContext();
            log.info("Configuring SSL Context for FeignClient");
            return new Client.Default(sslContext.getSocketFactory(), new DefaultHostnameVerifier());
        } catch (NoSuchSslBundleException ex) {
            log.error("SSLContext not provided. Creating FeignClient without sslContext.");
            throw new IllegalStateException("spring.ssl.bundle.jks.secure-service.key.alias not configure correctly. Please change your application properties, yml or environment configuration.");
        }
    }

I proposed approach would be similar to this:

    @Bean
    public restTemplate(RestTemplateBuilder restTemplateBuilder, SslBundles sslBundles) {
        this.restTemplate = restTemplateBuilder.setSslBundle(sslBundles.getBundle("secure-service")).build();
    }

Further reference: https://www.baeldung.com/spring-boot-security-ssl-bundles

Start with the Feign client configuration entry points and compare the shown SslBundles/SSLContext approach with RestTemplateBuilder.setSslBundle. Trace how Feign clients construct their Client and determine where an SSL bundle could be selected. Done means FeignClients can use a configured Spring Boot SSL bundle, with behavior and failure handling covered by tests.