Support Google Cloud Source repositories (#1278)

* Extract transport configuration to TransportConfigCallbackFactory

* Authenticate against Google Cloud Source repositories

Fixes gh-1260

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

@@ -334,6 +334,17 @@ AWS EC2 instances may use https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ia
 NOTE: The `aws-java-sdk-core` jar is an optional dependency.
 If the `aws-java-sdk-core` jar is not on your classpath, the AWS Code Commit credential provider is not created, regardless of the git server URI.
 
+===== Authentication with Google Cloud Source
+
+Spring Cloud Config Server also supports authenticating against https://cloud.google.com/source-repositories/[Google Cloud Source] repositories.
+
+If your Git URI uses the `http` or `https` protocol and the domain name is `source.developers.google.com`, the Google Cloud Source credentials provider will be used. A Google Cloud Source repository URI has the format `https://source.developers.google.com/p/${GCP_PROJECT}/r/${REPO}`. To obtain the URI for your repository, click on "Clone" in the Google Cloud Source UI, and select "Manually generated credentials". Do not generate any credentials, simply copy the displayed URI.
+
+The Google Cloud Source credentials provider will use Google Cloud Platform application default credentials. See https://cloud.google.com/sdk/gcloud/reference/auth/application-default/login[Google Cloud SDK documentation] on how to create application default credentials for a system. This approach will work for user accounts in dev environments and for service accounts in production environments.
+
+NOTE: `com.google.auth:google-auth-library-oauth2-http` is an optional dependency.
+If the `google-auth-library-oauth2-http` jar is not on your classpath, the Google Cloud Source credential provider is not created, regardless of the git server URI.
+
 ===== Git SSH configuration using properties
 
 By default, the JGit library used by Spring Cloud Config Server uses SSH configuration files such as `~/.ssh/known_hosts` and `/etc/ssh/ssh_config` when connecting to Git repositories by using an SSH URI.

pom.xml

@@ -70,6 +70,11 @@
 				<artifactId>aws-java-sdk-core</artifactId>
 				<version>1.11.52</version>
 			</dependency>
+			<dependency>
+				<groupId>com.google.auth</groupId>
+				<artifactId>google-auth-library-oauth2-http</artifactId>
+				<version>0.15.0</version>
+			</dependency>
 		</dependencies>
 	</dependencyManagement>
 	<profiles>

spring-cloud-config-server/pom.xml

@@ -85,6 +85,11 @@
 			<artifactId>spring-boot-autoconfigure-processor</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>com.google.auth</groupId>
+			<artifactId>google-auth-library-oauth2-http</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>com.h2database</groupId>
 			<artifactId>h2</artifactId>

spring-cloud-config-server/src/main/java/org/springframework/cloud/config/server/config/EnvironmentRepositoryConfiguration.java

@@ -64,6 +64,8 @@ import org.springframework.cloud.config.server.environment.SvnKitEnvironmentRepo
 import org.springframework.cloud.config.server.environment.VaultEnvironmentProperties;
 import org.springframework.cloud.config.server.environment.VaultEnvironmentRepository;
 import org.springframework.cloud.config.server.environment.VaultEnvironmentRepositoryFactory;
+import org.springframework.cloud.config.server.support.GoogleCloudSourceSupport;
+import org.springframework.cloud.config.server.support.TransportConfigCallbackFactory;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
@@ -91,7 +93,8 @@ import org.springframework.jdbc.core.JdbcTemplate;
 		VaultRepositoryConfiguration.class, CredhubConfiguration.class,
 		CredhubRepositoryConfiguration.class, SvnRepositoryConfiguration.class,
 		NativeRepositoryConfiguration.class, GitRepositoryConfiguration.class,
-		RedisRepositoryConfiguration.class, DefaultRepositoryConfiguration.class })
+		RedisRepositoryConfiguration.class, GoogleCloudSourceConfiguration.class,
+		DefaultRepositoryConfiguration.class })
 public class EnvironmentRepositoryConfiguration {
 
 	@Bean
@@ -137,9 +140,13 @@ public class EnvironmentRepositoryConfiguration {
 		public MultipleJGitEnvironmentRepositoryFactory gitEnvironmentRepositoryFactory(
 				ConfigurableEnvironment environment, ConfigServerProperties server,
 				Optional<ConfigurableHttpConnectionFactory> jgitHttpConnectionFactory,
-				Optional<TransportConfigCallback> customTransportConfigCallback) {
+				Optional<TransportConfigCallback> customTransportConfigCallback,
+				Optional<GoogleCloudSourceSupport> googleCloudSourceSupport) {
+			final TransportConfigCallbackFactory transportConfigCallbackFactory = new TransportConfigCallbackFactory(
+					customTransportConfigCallback.orElse(null),
+					googleCloudSourceSupport.orElse(null));
 			return new MultipleJGitEnvironmentRepositoryFactory(environment, server,
-					jgitHttpConnectionFactory, customTransportConfigCallback);
+					jgitHttpConnectionFactory, transportConfigCallbackFactory);
 		}
 
 	}

spring-cloud-config-server/src/main/java/org/springframework/cloud/config/server/config/GoogleCloudSourceConfiguration.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2013-2019 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.config.server.config;
+
+import com.google.auth.oauth2.GoogleCredentials;
+import org.eclipse.jgit.api.TransportConfigCallback;
+
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.cloud.config.server.support.GoogleCloudSourceSupport;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * Adds Google Cloud Source OAuth2 support, if
+ * com.google.auth:google-auth-library-oauth2-http library is on classpath.
+ *
+ * @author Eduard Wirch
+ */
+@Configuration
+@ConditionalOnClass({ GoogleCredentials.class, TransportConfigCallback.class })
+public class GoogleCloudSourceConfiguration {
+
+	@Bean
+	public GoogleCloudSourceSupport createGoogleCloudSourceSupport() {
+		return new GoogleCloudSourceSupport();
+	}
+
+}

spring-cloud-config-server/src/main/java/org/springframework/cloud/config/server/environment/MultipleJGitEnvironmentRepositoryFactory.java

@@ -18,12 +18,10 @@ package org.springframework.cloud.config.server.environment;
 
 import java.util.Optional;
 
-import org.eclipse.jgit.api.TransportConfigCallback;
 import org.eclipse.jgit.transport.HttpTransport;
 
 import org.springframework.cloud.config.server.config.ConfigServerProperties;
-import org.springframework.cloud.config.server.ssh.FileBasedSshTransportConfigCallback;
-import org.springframework.cloud.config.server.ssh.PropertiesBasedSshTransportConfigCallback;
+import org.springframework.cloud.config.server.support.TransportConfigCallbackFactory;
 import org.springframework.core.env.ConfigurableEnvironment;
 
 /**
@@ -38,23 +36,23 @@ public class MultipleJGitEnvironmentRepositoryFactory implements
 
 	private Optional<ConfigurableHttpConnectionFactory> connectionFactory;
 
-	private Optional<TransportConfigCallback> customTransportConfigCallback;
+	private final TransportConfigCallbackFactory transportConfigCallbackFactory;
 
 	@Deprecated
 	public MultipleJGitEnvironmentRepositoryFactory(ConfigurableEnvironment environment,
 			ConfigServerProperties server,
-			Optional<TransportConfigCallback> customTransportConfigCallback) {
-		this(environment, server, Optional.empty(), customTransportConfigCallback);
+			TransportConfigCallbackFactory transportConfigCallbackFactory) {
+		this(environment, server, Optional.empty(), transportConfigCallbackFactory);
 	}
 
 	public MultipleJGitEnvironmentRepositoryFactory(ConfigurableEnvironment environment,
 			ConfigServerProperties server,
 			Optional<ConfigurableHttpConnectionFactory> connectionFactory,
-			Optional<TransportConfigCallback> customTransportConfigCallback) {
+			TransportConfigCallbackFactory transportConfigCallbackFactory) {
 		this.environment = environment;
 		this.server = server;
 		this.connectionFactory = connectionFactory;
-		this.customTransportConfigCallback = customTransportConfigCallback;
+		this.transportConfigCallbackFactory = transportConfigCallbackFactory;
 	}
 
 	@Override
@@ -67,21 +65,12 @@ public class MultipleJGitEnvironmentRepositoryFactory implements
 
 		MultipleJGitEnvironmentRepository repository = new MultipleJGitEnvironmentRepository(
 				this.environment, environmentProperties);
-		repository.setTransportConfigCallback(this.customTransportConfigCallback
-				.orElse(buildTransportConfigCallback(environmentProperties)));
+		repository.setTransportConfigCallback(
+				transportConfigCallbackFactory.build(environmentProperties));
 		if (this.server.getDefaultLabel() != null) {
 			repository.setDefaultLabel(this.server.getDefaultLabel());
 		}
 		return repository;
 	}
 
-	private TransportConfigCallback buildTransportConfigCallback(
-			MultipleJGitEnvironmentProperties gitEnvironmentProperties) {
-		if (gitEnvironmentProperties.isIgnoreLocalSshSettings()) {
-			return new PropertiesBasedSshTransportConfigCallback(
-					gitEnvironmentProperties);
-		}
-		return new FileBasedSshTransportConfigCallback(gitEnvironmentProperties);
-	}
-
 }

spring-cloud-config-server/src/main/java/org/springframework/cloud/config/server/support/GoogleCloudSourceSupport.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2013-2019 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.config.server.support;
+
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+
+import com.google.auth.oauth2.GoogleCredentials;
+import org.eclipse.jgit.api.TransportConfigCallback;
+import org.eclipse.jgit.transport.Transport;
+import org.eclipse.jgit.transport.TransportHttp;
+import org.eclipse.jgit.transport.URIish;
+
+import static java.util.stream.Collectors.toMap;
+
+/**
+ * Provides credentials for Google Cloud Source repositories by adding a
+ * {@code Authenticate} http header.
+ * <p/>
+ * It does so by acting as a transport configurer. If a transport instance targets a
+ * Google Cloud Source repository, this implementation retrieves Google Cloud application
+ * default credentials and adds them as a http header.
+ *
+ * @author Eduard Wirch
+ * @see <a href=
+ * "https://cloud.google.com/sdk/gcloud/reference/auth/application-default/login"> gcloud
+ * auth application-default login</a>
+ */
+public final class GoogleCloudSourceSupport {
+
+	boolean canHandle(String uri) {
+		try {
+			return GCSTransportConfigCallback.canHandle(new URIish(uri));
+		}
+		catch (URISyntaxException e) {
+			return false;
+		}
+	}
+
+	// This detour via GCSTransportConfigCallback was necessary because:
+	// - we want the Google Cloud credentials provider to be a bean, so we can use
+	// @ConditionalOnClass to conditionally disable support, if required classes
+	// are not on the class path.
+	// - We cannot make a class implementing TransportConfigCallback a bean,
+	// because Spring would populate customTransportConfigCallback with this bean
+	// (see JGitFactoryConfig.gitEnvironmentRepositoryFactory()), and report a
+	// conflict whenever there is a real "custom" TransportConfigCallback
+	// implementation in the Spring context.
+	// This is why GoogleCloudSourceSupport is the optional bean, which can provide
+	// the TransportConfigCallback on request.
+	TransportConfigCallback createTransportConfigCallback() {
+		return new GCSTransportConfigCallback(
+				new ApplicationDefaultCredentialsProvider());
+	}
+
+	TransportConfigCallback createTransportConfigCallback(
+			CredentialsProvider credentialsProvider) {
+		return new GCSTransportConfigCallback(credentialsProvider);
+	}
+
+	private static final class GCSTransportConfigCallback
+			implements TransportConfigCallback {
+
+		private static final String GOOGLE_CLOUD_SOURCE_HOST = "source.developers.google.com";
+
+		private final CredentialsProvider credentialsProvider;
+
+		private GCSTransportConfigCallback(CredentialsProvider credentialsProvider) {
+			this.credentialsProvider = credentialsProvider;
+		}
+
+		@Override
+		public void configure(Transport transport) {
+			if (transport instanceof TransportHttp && canHandle(transport.getURI())) {
+				addHeaders((TransportHttp) transport,
+						credentialsProvider.getAuthorizationHeaders());
+			}
+		}
+
+		private static boolean canHandle(URIish uri) {
+			return isHttpScheme(uri) && isGoogleCloudSourceHost(uri);
+		}
+
+		private static boolean isHttpScheme(URIish uri) {
+			final String scheme = uri.getScheme();
+			return Objects.equals(scheme, "http") || Objects.equals(scheme, "https");
+		}
+
+		private static boolean isGoogleCloudSourceHost(URIish uri) {
+			return Objects.equals(uri.getHost(), GOOGLE_CLOUD_SOURCE_HOST);
+		}
+
+		private void addHeaders(TransportHttp transport, Map<String, String> headers) {
+			transport.setAdditionalHeaders(headers);
+		}
+
+	}
+
+	interface CredentialsProvider {
+
+		Map<String, String> getAuthorizationHeaders();
+
+	}
+
+	private static class ApplicationDefaultCredentialsProvider
+			implements CredentialsProvider {
+
+		@Override
+		public Map<String, String> getAuthorizationHeaders() {
+			try {
+				return GoogleCredentials.getApplicationDefault().getRequestMetadata()
+						.entrySet().stream()
+						.collect(toMap(Entry::getKey, this::joinValues));
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException(ex);
+			}
+		}
+
+		private String joinValues(Entry<?, List<String>> entry) {
+			return String.join(", ", entry.getValue());
+		}
+
+	}
+
+}

spring-cloud-config-server/src/main/java/org/springframework/cloud/config/server/support/TransportConfigCallbackFactory.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2013-2019 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.config.server.support;
+
+import javax.annotation.Nullable;
+
+import org.eclipse.jgit.api.TransportConfigCallback;
+
+import org.springframework.cloud.config.server.environment.MultipleJGitEnvironmentProperties;
+import org.springframework.cloud.config.server.ssh.FileBasedSshTransportConfigCallback;
+import org.springframework.cloud.config.server.ssh.PropertiesBasedSshTransportConfigCallback;
+
+public class TransportConfigCallbackFactory {
+
+	@Nullable
+	private final TransportConfigCallback customTransportConfigCallback;
+
+	@Nullable
+	private final GoogleCloudSourceSupport googleCloudSourceSupport;
+
+	public TransportConfigCallbackFactory(
+			TransportConfigCallback customTransportConfigCallback,
+			GoogleCloudSourceSupport googleCloudSourceSupport) {
+
+		this.customTransportConfigCallback = customTransportConfigCallback;
+		this.googleCloudSourceSupport = googleCloudSourceSupport;
+	}
+
+	public TransportConfigCallback build(
+			MultipleJGitEnvironmentProperties environmentProperties) {
+
+		// customTransportConfigCallback has the highest priority. If someone put
+		// a TransportConfigCallback bean in to the Spring context, we use it for
+		// all repositories.
+		if (customTransportConfigCallback != null) {
+			return customTransportConfigCallback;
+		}
+
+		// If the currently configured repository is a Google Cloud Source repository
+		// we use GoogleCloudSourceSupport.
+		if (googleCloudSourceSupport != null) {
+			final String uri = environmentProperties.getUri();
+			if (googleCloudSourceSupport.canHandle(uri)) {
+				return googleCloudSourceSupport.createTransportConfigCallback();
+			}
+		}
+
+		// Otherwise - legacy behaviour - use SshTransportConfigCallback for all
+		// repositories.
+		return buildSshTransportConfigCallback(environmentProperties);
+	}
+
+	private TransportConfigCallback buildSshTransportConfigCallback(
+			MultipleJGitEnvironmentProperties gitEnvironmentProperties) {
+
+		if (gitEnvironmentProperties.isIgnoreLocalSshSettings()) {
+			return new PropertiesBasedSshTransportConfigCallback(
+					gitEnvironmentProperties);
+		}
+		return new FileBasedSshTransportConfigCallback(gitEnvironmentProperties);
+	}
+
+}

spring-cloud-config-server/src/test/java/org/springframework/cloud/config/server/CompositeClasspathTests.java

@@ -114,4 +114,23 @@ public class CompositeClasspathTests {
 
 	}
 
+	@RunWith(ModifiedClassPathRunner.class)
+	@ClassPathExclusions("google-auth-library-oauth2-http-*.jar")
+	public static class GoogleAuthTests {
+
+		@Test
+		public void contextLoads() {
+			new WebApplicationContextRunner()
+					.withUserConfiguration(ConfigServerApplication.class)
+					.withPropertyValues("spring.profiles.active:test,composite",
+							"spring.jmx.enabled=false", "spring.config.name:configserver",
+							"spring.cloud.config.server.composite[0].uri:https://source.developers.google.com",
+							"spring.cloud.config.server.composite[0].type:git")
+					.run(context -> {
+						CompositeUtils.getCompositeTypeList(context.getEnvironment());
+					});
+		}
+
+	}
+
 }

spring-cloud-config-server/src/test/java/org/springframework/cloud/config/server/support/GoogleCloudSourceSupportTests.java

@@ -0,0 +1,161 @@
+/*
+ * Copyright 2013-2019 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.config.server.support;
+
+import java.net.URISyntaxException;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.eclipse.jgit.api.TransportConfigCallback;
+import org.eclipse.jgit.transport.SshTransport;
+import org.eclipse.jgit.transport.Transport;
+import org.eclipse.jgit.transport.TransportHttp;
+import org.eclipse.jgit.transport.URIish;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import org.springframework.cloud.config.server.support.GoogleCloudSourceSupport.CredentialsProvider;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.anyMap;
+import static org.mockito.Mockito.atMost;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+/**
+ * @author Eduard Wirch
+ */
+public class GoogleCloudSourceSupportTests {
+
+	private static final String HTTPS_GOOGLE_CLOUD_SOURCE_REPO = "https://source.developers.google.com/r/somerepo";
+
+	private static final String HTTP_GOOGLE_CLOUD_SOURCE_REPO = "http://source.developers.google.com/r/somerepo";
+
+	private static final String SSH_GOOGLE_CLOUD_SOURCE_REPO = "ssh://source.developers.google.com/r/somerepo";
+
+	private static final String HTTPS_OTHER_REPO = "https://somehub.com/r/somerepo";
+
+	@Test
+	public void verifySetsAuthHeadersForHttpsGCSRepo() throws URISyntaxException {
+		Map<String, String> authHeaders = createAuthHeaders();
+		TransportConfigCallback callback = transportConfigCallbackWith(authHeaders);
+
+		TransportHttp transport = mockTransportHttp(HTTPS_GOOGLE_CLOUD_SOURCE_REPO);
+		Map<String, String> actualHeaders = recordSetHeaders(transport);
+
+		callback.configure(transport);
+
+		assertThat(actualHeaders).containsAllEntriesOf(authHeaders);
+	}
+
+	@Test
+	public void verifySetsAuthHeadersForHttpGCSRepo() throws URISyntaxException {
+		Map<String, String> authHeaders = createAuthHeaders();
+		TransportConfigCallback callback = transportConfigCallbackWith(authHeaders);
+
+		TransportHttp transport = mockTransportHttp(HTTP_GOOGLE_CLOUD_SOURCE_REPO);
+		Map<String, String> actualHeaders = recordSetHeaders(transport);
+
+		callback.configure(transport);
+
+		assertThat(actualHeaders).containsAllEntriesOf(authHeaders);
+	}
+
+	@Test
+	public void verifyDoesNothingForSshGCSRepo() throws URISyntaxException {
+		TransportConfigCallback callback = transportConfigCallbackWith(
+				createAuthHeaders());
+		TransportHttp transport = mockTransportHttp(SSH_GOOGLE_CLOUD_SOURCE_REPO);
+
+		callback.configure(transport);
+
+		verifyOnlyValidInteraction(transport);
+	}
+
+	@Test
+	public void verifyDoesNothingForHttpsOtherRepo() throws URISyntaxException {
+		TransportConfigCallback callback = transportConfigCallbackWith(
+				createAuthHeaders());
+		TransportHttp transport = mockTransportHttp(HTTPS_OTHER_REPO);
+
+		callback.configure(transport);
+
+		verifyOnlyValidInteraction(transport);
+	}
+
+	@Test
+	public void verifyDoesNothingForNonHttpTransports() throws URISyntaxException {
+		TransportConfigCallback callback = transportConfigCallbackWith(
+				createAuthHeaders());
+		Transport transport = mockSshTransport(SSH_GOOGLE_CLOUD_SOURCE_REPO);
+
+		callback.configure(transport);
+
+		verifyOnlyValidInteraction(transport);
+	}
+
+	private void verifyOnlyValidInteraction(Transport transport) {
+		// Actually, we don't care how often getURI() was invoked, simply "allow"
+		// invocation of getURI(), so verifyNoMoreInteractions() won't complain
+		// about getURI().
+		verify(transport, atMost(10000)).getURI();
+
+		verifyNoMoreInteractions(transport);
+	}
+
+	private Map<String, String> createAuthHeaders() {
+		Map<String, String> headers = new HashMap<>();
+		headers.put("WWW-Authorization", "user:password");
+		return headers;
+	}
+
+	private Map<String, String> recordSetHeaders(TransportHttp transport) {
+		Map<String, String> headers = new HashMap<>();
+		doAnswer(invocation -> {
+			headers.putAll(invocation.getArgument(0));
+			return null;
+		}).when(transport).setAdditionalHeaders(anyMap());
+		return headers;
+	}
+
+	private TransportHttp mockTransportHttp(String uri) throws URISyntaxException {
+		TransportHttp transport = Mockito.mock(TransportHttp.class);
+
+		when(transport.getURI()).thenReturn(new URIish(uri));
+
+		return transport;
+	}
+
+	@SuppressWarnings("SameParameterValue")
+	private Transport mockSshTransport(String uri) throws URISyntaxException {
+		Transport transport = Mockito.mock(SshTransport.class);
+
+		when(transport.getURI()).thenReturn(new URIish(uri));
+
+		return transport;
+	}
+
+	private TransportConfigCallback transportConfigCallbackWith(
+			Map<String, String> authHeaders) {
+		CredentialsProvider credentialsProvider = () -> authHeaders;
+		return new GoogleCloudSourceSupport()
+				.createTransportConfigCallback(credentialsProvider);
+	}
+
+}