Enable X-Forwarded Headers. (#748)

docs/src/main/asciidoc/spring-cloud-openfeign.adoc

@@ -842,6 +842,15 @@ For `Request`, you need to implement and define `LoadBalancerFeignRequestTransfo
 If multiple transformers are defined, they are applied in the order in which beans are defined.
 Alternatively, you can use `LoadBalancerFeignRequestTransformer.DEFAULT_ORDER` to specify the order.
 
+=== X-Forwarded Headers Support
+
+`X-Forwarded-Host` and `X-Forwarded-Proto` support can be enabled by setting following flag:
+
+[source,properties]
+----
+spring.cloud.loadbalancer.x-forwarded.enabled=true
+----
+
 == Configuration properties
 
 To see the list of all Spring Cloud OpenFeign related configuration properties please check link:appendix.html[the Appendix page].

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/loadbalancer/FeignLoadBalancerAutoConfiguration.java

@@ -23,6 +23,7 @@ import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration;
 import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
@@ -30,6 +31,7 @@ import org.springframework.cloud.loadbalancer.config.BlockingLoadBalancerClientA
 import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
 import org.springframework.cloud.openfeign.FeignAutoConfiguration;
 import org.springframework.cloud.openfeign.support.FeignHttpClientProperties;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 
@@ -39,6 +41,7 @@ import org.springframework.context.annotation.Import;
  *
  * @author Olga Maciaszek-Sharma
  * @author Nguyen Ky Thanh
+ * @author changjin wei(魏昌进)
  * @since 2.2.0
  */
 @ConditionalOnClass(Feign.class)
@@ -54,4 +57,11 @@ import org.springframework.context.annotation.Import;
 		HttpClient5FeignLoadBalancerConfiguration.class, DefaultFeignLoadBalancerConfiguration.class })
 public class FeignLoadBalancerAutoConfiguration {
 
+	@Bean
+	@ConditionalOnBean(LoadBalancerClientFactory.class)
+	@ConditionalOnMissingBean(XForwardedHeadersTransformer.class)
+	public XForwardedHeadersTransformer xForwarderHeadersFeignTransformer(LoadBalancerClientFactory factory) {
+		return new XForwardedHeadersTransformer(factory);
+	}
+
 }

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/loadbalancer/XForwardedHeadersTransformer.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2013-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.openfeign.loadbalancer;
+
+import java.net.URI;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import feign.Request;
+
+import org.springframework.cloud.client.ServiceInstance;
+import org.springframework.cloud.client.loadbalancer.LoadBalancerProperties;
+import org.springframework.cloud.client.loadbalancer.reactive.ReactiveLoadBalancer;
+
+/**
+ * To add X-Forwarded-Host and X-Forwarded-Proto Headers.
+ *
+ * @author changjin wei(魏昌进)
+ */
+public class XForwardedHeadersTransformer implements LoadBalancerFeignRequestTransformer {
+
+	private final ReactiveLoadBalancer.Factory<ServiceInstance> factory;
+
+	public XForwardedHeadersTransformer(ReactiveLoadBalancer.Factory<ServiceInstance> factory) {
+		this.factory = factory;
+	}
+
+	@Override
+	public Request transformRequest(Request request, ServiceInstance instance) {
+		if (instance == null) {
+			return request;
+		}
+		LoadBalancerProperties.XForwarded xForwarded = factory.getProperties(instance.getServiceId()).getXForwarded();
+		if (xForwarded.isEnabled()) {
+			Map<String, Collection<String>> headers = new HashMap<>(request.headers());
+			URI uri = URI.create(request.url());
+			String xForwardedHost = uri.getHost();
+			String xForwardedProto = uri.getScheme();
+			headers.put("X-Forwarded-Host", Collections.singleton(xForwardedHost));
+			headers.put("X-Forwarded-Proto", Collections.singleton(xForwardedProto));
+			request = Request.create(request.httpMethod(), request.url(), headers, request.body(), request.charset(),
+					request.requestTemplate());
+		}
+		return request;
+	}
+
+}

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/loadbalancer/XForwardedHeadersTransformerTests.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2013-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.openfeign.loadbalancer;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import feign.Request;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.cloud.client.DefaultServiceInstance;
+import org.springframework.cloud.client.ServiceInstance;
+import org.springframework.cloud.client.loadbalancer.LoadBalancerProperties;
+import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Tests for
+ * {@link XForwardedHeadersTransformer}.
+ *
+ * @author changjin wei(魏昌进)
+ */
+class XForwardedHeadersTransformerTests {
+
+	private final LoadBalancerClientFactory loadBalancerClientFactory = mock(LoadBalancerClientFactory.class);
+
+	private final LoadBalancerProperties loadBalancerProperties = new LoadBalancerProperties();
+
+	private final ServiceInstance serviceInstance = new DefaultServiceInstance("test1", "test", "test.org", 8080,
+			false);
+
+	private final Request request = testRequest();
+
+	private Request testRequest() {
+		return testRequest("spring.io");
+	}
+
+	private Request testRequest(String host) {
+		return Request.create(Request.HttpMethod.GET, "https://" + host + "/path", testHeaders(), "hello".getBytes(),
+				StandardCharsets.UTF_8, null);
+	}
+
+	private Map<String, Collection<String>> testHeaders() {
+		Map<String, Collection<String>> feignHeaders = new HashMap<>();
+		feignHeaders.put(HttpHeaders.CONTENT_TYPE, Collections.singletonList(MediaType.APPLICATION_JSON_VALUE));
+		return feignHeaders;
+
+	}
+
+	@Test
+	void shouldAppendXForwardedHeadersIfEnabled() {
+		loadBalancerProperties.getXForwarded().setEnabled(true);
+		when(loadBalancerClientFactory.getProperties("test")).thenReturn(loadBalancerProperties);
+		XForwardedHeadersTransformer transformer = new XForwardedHeadersTransformer(loadBalancerClientFactory);
+
+		Request newRequest = transformer.transformRequest(request, serviceInstance);
+
+		assertThat(newRequest.headers()).containsKey("X-Forwarded-Host");
+		assertThat(newRequest.headers()).containsEntry("X-Forwarded-Host", Collections.singleton("spring.io"));
+		assertThat(newRequest.headers()).containsKey("X-Forwarded-Proto");
+		assertThat(newRequest.headers()).containsEntry("X-Forwarded-Proto", Collections.singleton("https"));
+
+	}
+
+	@Test
+	void shouldNotAppendXForwardedHeadersIfDefault() {
+		when(loadBalancerClientFactory.getProperties("test")).thenReturn(loadBalancerProperties);
+		XForwardedHeadersTransformer transformer = new XForwardedHeadersTransformer(loadBalancerClientFactory);
+
+		Request newRequest = transformer.transformRequest(request, serviceInstance);
+
+		assertThat(newRequest.headers()).doesNotContainKey("X-Forwarded-Host");
+		assertThat(newRequest.headers()).doesNotContainKey("X-Forwarded-Proto");
+	}
+
+}