Add AuthenticationSteps support to AwsIamAuthentication.

AwsIamAuthentication can now be used with AuthenticationSteps for reactive/non-blocking usage. AwsIamAuthentication fetches AWS credentials on AuthenticationSteps creation to prevent blocking access during login.

Closes gh-338.

spring-vault-core/src/main/java/org/springframework/vault/authentication/AwsIamAuthentication.java

@@ -24,6 +24,7 @@ import java.util.Map.Entry;
 
 import com.amazonaws.DefaultRequest;
 import com.amazonaws.auth.AWS4Signer;
+import com.amazonaws.auth.AWSCredentials;
 import com.amazonaws.http.HttpMethodName;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -65,7 +66,8 @@ import org.springframework.web.client.RestOperations;
  * href="http://docs.aws.amazon.com/STS/latest/APIReference/API_GetCallerIdentity.html">AWS:
  * GetCallerIdentity</a>
  */
-public class AwsIamAuthentication implements ClientAuthentication {
+public class AwsIamAuthentication implements ClientAuthentication,
+		AuthenticationStepsFactory {
 
 	private static final Log logger = LogFactory.getLog(AwsIamAuthentication.class);
 
@@ -98,11 +100,45 @@ public class AwsIamAuthentication implements ClientAuthentication {
 		this.vaultRestOperations = vaultRestOperations;
 	}
 
+	/**
+	 * Creates a {@link AuthenticationSteps} for AWS-IAM authentication given
+	 * {@link AwsIamAuthenticationOptions}. The resulting {@link AuthenticationSteps}
+	 * reuse eagerly-fetched {@link AWSCredentials} to prevent blocking I/O during
+	 * authentication.
+	 *
+	 * @param options must not be {@literal null}.
+	 * @return {@link AuthenticationSteps} for AWS-IAM authentication.
+	 * @since 2.2
+	 */
+	public static AuthenticationSteps createAuthenticationSteps(
+			AwsIamAuthenticationOptions options) {
+
+		Assert.notNull(options, "AwsIamAuthenticationOptions must not be null");
+
+		AWSCredentials credentials = options.getCredentialsProvider().getCredentials();
+
+		return createAuthenticationSteps(options, credentials);
+	}
+
+	protected static AuthenticationSteps createAuthenticationSteps(
+			AwsIamAuthenticationOptions options, AWSCredentials credentials) {
+
+		return AuthenticationSteps.fromSupplier(
+				() -> createRequestBody(options, credentials)) //
+				.login("auth/{mount}/login", options.getPath());
+	}
+
 	@Override
 	public VaultToken login() throws VaultException {
 		return createTokenUsingAwsIam();
 	}
 
+	@Override
+	public AuthenticationSteps getAuthenticationSteps() {
+		return createAuthenticationSteps(this.options, this.options
+				.getCredentialsProvider().getCredentials());
+	}
+
 	@SuppressWarnings("unchecked")
 	private VaultToken createTokenUsingAwsIam() {
 
@@ -147,6 +183,19 @@ public class AwsIamAuthentication implements ClientAuthentication {
 	 */
 	protected static Map<String, String> createRequestBody(
 			AwsIamAuthenticationOptions options) {
+		return createRequestBody(options, options.getCredentialsProvider()
+				.getCredentials());
+	}
+
+	/**
+	 * Create the request body to perform a Vault login using the AWS-IAM authentication
+	 * method.
+	 *
+	 * @param options must not be {@literal null}.
+	 * @return the map containing body key-value pairs.
+	 */
+	private static Map<String, String> createRequestBody(
+			AwsIamAuthenticationOptions options, AWSCredentials credentials) {
 
 		Map<String, String> login = new HashMap<>();
 
@@ -155,7 +204,7 @@ public class AwsIamAuthentication implements ClientAuthentication {
 				.toString().getBytes()));
 		login.put("iam_request_body", REQUEST_BODY_BASE64_ENCODED);
 
-		String headerJson = getSignedHeaders(options);
+		String headerJson = getSignedHeaders(options, credentials);
 
 		login.put("iam_request_headers",
 				Base64Utils.encodeToString(headerJson.getBytes()));
@@ -166,7 +215,8 @@ public class AwsIamAuthentication implements ClientAuthentication {
 		return login;
 	}
 
-	private static String getSignedHeaders(AwsIamAuthenticationOptions options) {
+	private static String getSignedHeaders(AwsIamAuthenticationOptions options,
+			AWSCredentials credentials) {
 
 		Map<String, String> headers = createIamRequestHeaders(options);
 
@@ -180,7 +230,7 @@ public class AwsIamAuthentication implements ClientAuthentication {
 		request.setEndpoint(options.getEndpointUri());
 
 		signer.setServiceName(request.getServiceName());
-		signer.sign(request, options.getCredentialsProvider().getCredentials());
+		signer.sign(request, credentials);
 
 		Map<String, Object> map = new LinkedHashMap<>();
 

spring-vault-core/src/test/java/org/springframework/vault/authentication/AwsIamAuthenticationUnitTests.java

@@ -46,7 +46,7 @@ public class AwsIamAuthenticationUnitTests {
 	private MockRestServiceServer mockRest;
 
 	@Before
-	public void before() throws Exception {
+	public void before() {
 
 		RestTemplate restTemplate = VaultClients.createRestTemplate();
 		restTemplate.setUriTemplateHandler(new PrefixAwareUriTemplateHandler());
@@ -85,4 +85,39 @@ public class AwsIamAuthenticationUnitTests {
 				Duration.ofSeconds(10));
 		assertThat(((LoginToken) login).isRenewable()).isTrue();
 	}
+
+	@Test
+	public void shouldUsingAuthenticationSteps() {
+
+		mockRest.expect(requestTo("/auth/aws/login"))
+				.andExpect(method(HttpMethod.POST))
+				.andExpect(jsonPath("$.iam_http_request_method").value("POST"))
+				.andExpect(jsonPath("$.iam_request_url").exists())
+				.andExpect(jsonPath("$.iam_request_body").exists())
+				.andExpect(jsonPath("$.iam_request_headers").exists())
+				.andExpect(jsonPath("$.role").value("foo-role"))
+				.andRespond(
+						withSuccess()
+								.contentType(MediaType.APPLICATION_JSON)
+								.body("{"
+										+ "\"auth\":{\"client_token\":\"my-token\", \"renewable\": true, \"lease_duration\": 10}"
+										+ "}"));
+
+		AwsIamAuthenticationOptions options = AwsIamAuthenticationOptions.builder()
+				.role("foo-role").credentials(new BasicAWSCredentials("foo", "bar"))
+				.build();
+
+		AuthenticationSteps steps = AwsIamAuthentication
+				.createAuthenticationSteps(options);
+		AuthenticationStepsExecutor executor = new AuthenticationStepsExecutor(steps,
+				restTemplate);
+
+		VaultToken login = executor.login();
+
+		assertThat(login).isInstanceOf(LoginToken.class);
+		assertThat(login.getToken()).isEqualTo("my-token");
+		assertThat(((LoginToken) login).getLeaseDuration()).isEqualTo(
+				Duration.ofSeconds(10));
+		assertThat(((LoginToken) login).isRenewable()).isTrue();
+	}
 }