Add REST handler for PKI delegation

client/rest-high-level/build.gradle

@@ -83,6 +83,7 @@ processTestResources {
   from({ zipTree(configurations.restSpec.singleFile) }) {
     include 'rest-api-spec/api/**'
   }
+  from(project(':client:rest-high-level').file('src/test/resources'))
 }
 
 dependencyLicenses {
@@ -115,6 +116,7 @@ if (isEclipse) {
 
 File nodeCert = file("./testnode.crt")
 File nodeTrustStore = file("./testnode.jks")
+File pkiTrustCert = file("./src/test/resources/org/elasticsearch/client/security/delegate_pki/testRootCA.crt")
 
 integTest.runner {
   systemProperty 'tests.rest.cluster.username', System.getProperty('tests.rest.cluster.username', 'test_user')
@@ -132,11 +134,18 @@ testClusters.integTest {
   // Truststore settings are not used since TLS is not enabled. Included for testing the get certificates API
   setting 'xpack.security.http.ssl.certificate_authorities', 'testnode.crt'
   setting 'xpack.security.transport.ssl.truststore.path', 'testnode.jks'
+  setting 'xpack.security.authc.realms.file.default_file.order', '0'
+  setting 'xpack.security.authc.realms.native.default_native.order', '1'
+  setting 'xpack.security.authc.realms.pki.pki1.order', '2'
+  setting 'xpack.security.authc.realms.pki.pki1.certificate_authorities', '[ "testRootCA.crt" ]'
+  setting 'xpack.security.authc.realms.pki.pki1.delegation.enabled', 'true'
+
   setting 'indices.lifecycle.poll_interval', '1000ms'
   keystore 'xpack.security.transport.ssl.truststore.secure_password', 'testnode'
   user username:  System.getProperty('tests.rest.cluster.username', 'test_user'),
           password:  System.getProperty('tests.rest.cluster.password', 'test-password')
 
   extraConfigFile nodeCert.name, nodeCert
   extraConfigFile nodeTrustStore.name, nodeTrustStore
+  extraConfigFile pkiTrustCert.name, pkiTrustCert
 }

client/rest-high-level/src/main/java/org/elasticsearch/client/SecurityClient.java

@@ -31,6 +31,8 @@
 import org.elasticsearch.client.security.CreateApiKeyResponse;
 import org.elasticsearch.client.security.CreateTokenRequest;
 import org.elasticsearch.client.security.CreateTokenResponse;
+import org.elasticsearch.client.security.DelegatePkiAuthenticationRequest;
+import org.elasticsearch.client.security.DelegatePkiAuthenticationResponse;
 import org.elasticsearch.client.security.DeletePrivilegesRequest;
 import org.elasticsearch.client.security.DeletePrivilegesResponse;
 import org.elasticsearch.client.security.DeleteRoleMappingRequest;
@@ -969,4 +971,38 @@ public void invalidateApiKeyAsync(final InvalidateApiKeyRequest request, final R
         restHighLevelClient.performRequestAsyncAndParseEntity(request, SecurityRequestConverters::invalidateApiKey, options,
                 InvalidateApiKeyResponse::fromXContent, listener, emptySet());
     }
+
+    /**
+     * Get an Elasticsearch access token from an {@code X509Certificate} chain. The certificate chain is that of the client from a mutually
+     * authenticated TLS session, and it is validated by the PKI realms with {@code delegation.enabled} toggled to {@code true}.<br>
+     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-delegate-pki-authentication.html"> the
+     * docs</a> for more details.
+     * 
+     * @param request the request containing the certificate chain
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @return the response from the delegate-pki-authentication API key call
+     * @throws IOException in case there is a problem sending the request or parsing back the response
+     */
+    public DelegatePkiAuthenticationResponse delegatePkiAuthentication(DelegatePkiAuthenticationRequest request, RequestOptions options)
+            throws IOException {
+        return restHighLevelClient.performRequestAndParseEntity(request, SecurityRequestConverters::delegatePkiAuthentication, options,
+                DelegatePkiAuthenticationResponse::fromXContent, emptySet());
+    }
+
+    /**
+     * Asynchronously get an Elasticsearch access token from an {@code X509Certificate} chain. The certificate chain is that of the client
+     * from a mutually authenticated TLS session, and it is validated by the PKI realms with {@code delegation.enabled} toggled to
+     * {@code true}.<br>
+     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-delegate-pki-authentication.html"> the
+     * docs</a> for more details.
+     * 
+     * @param request the request containing the certificate chain
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @param listener the listener to be notified upon request completion
+     */
+    public void delegatePkiAuthenticationAsync(DelegatePkiAuthenticationRequest request, RequestOptions options,
+            ActionListener<DelegatePkiAuthenticationResponse> listener) {
+        restHighLevelClient.performRequestAsyncAndParseEntity(request, SecurityRequestConverters::delegatePkiAuthentication, options,
+                DelegatePkiAuthenticationResponse::fromXContent, listener, emptySet());
+    }
 }

client/rest-high-level/src/main/java/org/elasticsearch/client/SecurityRequestConverters.java

@@ -28,6 +28,7 @@
 import org.elasticsearch.client.security.ClearRolesCacheRequest;
 import org.elasticsearch.client.security.CreateApiKeyRequest;
 import org.elasticsearch.client.security.CreateTokenRequest;
+import org.elasticsearch.client.security.DelegatePkiAuthenticationRequest;
 import org.elasticsearch.client.security.DeletePrivilegesRequest;
 import org.elasticsearch.client.security.DeleteRoleMappingRequest;
 import org.elasticsearch.client.security.DeleteRoleRequest;
@@ -221,6 +222,12 @@ static Request createToken(CreateTokenRequest createTokenRequest) throws IOExcep
         return request;
     }
 
+    static Request delegatePkiAuthentication(DelegatePkiAuthenticationRequest delegatePkiAuthenticationRequest) throws IOException {
+        Request request = new Request(HttpPost.METHOD_NAME, "/_security/delegate_pki");
+        request.setEntity(createEntity(delegatePkiAuthenticationRequest, REQUEST_BODY_CONTENT_TYPE));
+        return request;
+    }
+
     static Request invalidateToken(InvalidateTokenRequest invalidateTokenRequest) throws IOException {
         Request request = new Request(HttpDelete.METHOD_NAME, "/_security/oauth2/token");
         request.setEntity(createEntity(invalidateTokenRequest, REQUEST_BODY_CONTENT_TYPE));

client/rest-high-level/src/main/java/org/elasticsearch/client/security/DelegatePkiAuthenticationRequest.java

@@ -0,0 +1,107 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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
+ *
+ *    http://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.elasticsearch.client.security;
+
+import org.elasticsearch.client.Validatable;
+import org.elasticsearch.client.ValidationException;
+import org.elasticsearch.common.xcontent.ToXContentObject;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+
+import java.io.IOException;
+import java.security.cert.CertificateEncodingException;
+import java.security.cert.X509Certificate;
+import java.util.Base64;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+
+import static java.util.Collections.unmodifiableList;
+
+public final class DelegatePkiAuthenticationRequest implements Validatable, ToXContentObject {
+
+    private final List<X509Certificate> x509CertificateChain;
+
+    public DelegatePkiAuthenticationRequest(final List<X509Certificate> x509CertificateChain) {
+        if (x509CertificateChain == null || x509CertificateChain.isEmpty()) {
+            throw new IllegalArgumentException("certificate chain must not be empty or null");
+        }
+        this.x509CertificateChain = unmodifiableList(x509CertificateChain);
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject().startArray("x509_certificate_chain");
+        try {
+            for (X509Certificate cert : x509CertificateChain) {
+                 builder.value(Base64.getEncoder().encodeToString(cert.getEncoded()));
+             }
+         } catch (CertificateEncodingException e) {
+             throw new IOException(e);
+         }
+         return builder.endArray().endObject();
+    }
+
+    public List<X509Certificate> getCertificateChain() {
+        return this.x509CertificateChain;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        final DelegatePkiAuthenticationRequest that = (DelegatePkiAuthenticationRequest) o;
+        return Objects.equals(x509CertificateChain, that.x509CertificateChain);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(x509CertificateChain);
+    }
+
+    @Override
+    public Optional<ValidationException> validate() {
+        ValidationException validationException = new ValidationException();
+        if (false == isOrderedCertificateChain(x509CertificateChain)) {
+            validationException.addValidationError("certificates chain must be an ordered chain");
+        }
+        return validationException.validationErrors().isEmpty() ? Optional.empty() : Optional.of(validationException);
+    }
+
+    /**
+     * Checks that the {@code X509Certificate} list is ordered, such that the end-entity certificate is first and it is followed by any
+     * certificate authorities'. The check validates that the {@code issuer} of every certificate is the {@code subject} of the certificate
+     * in the next array position. No other certificate attributes are checked.
+     */
+    private static boolean isOrderedCertificateChain(List<X509Certificate> chain) {
+        for (int i = 1; i < chain.size(); i++) {
+            X509Certificate cert = chain.get(i - 1);
+            X509Certificate issuer = chain.get(i);
+            if (false == cert.getIssuerX500Principal().equals(issuer.getSubjectX500Principal())) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+}

client/rest-high-level/src/main/java/org/elasticsearch/client/security/DelegatePkiAuthenticationResponse.java

@@ -0,0 +1,88 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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
+ *
+ *    http://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.elasticsearch.client.security;
+
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.unit.TimeValue;
+import org.elasticsearch.common.xcontent.ConstructingObjectParser;
+import org.elasticsearch.common.xcontent.XContentParser;
+
+import java.io.IOException;
+import java.util.Objects;
+
+import static org.elasticsearch.common.xcontent.ConstructingObjectParser.constructorArg;
+
+public final class DelegatePkiAuthenticationResponse {
+
+    private final String accessToken;
+    private final String type;
+    private final TimeValue expiresIn;
+
+    public DelegatePkiAuthenticationResponse(String accessToken, String type, TimeValue expiresIn) {
+        this.accessToken = accessToken;
+        this.type = type;
+        this.expiresIn = expiresIn;
+    }
+
+    public String getAccessToken() {
+        return accessToken;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public TimeValue getExpiresIn() {
+        return expiresIn;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        final DelegatePkiAuthenticationResponse that = (DelegatePkiAuthenticationResponse) o;
+        return Objects.equals(accessToken, that.accessToken) &&
+            Objects.equals(type, that.type) &&
+            Objects.equals(expiresIn, that.expiresIn);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(accessToken, type, expiresIn);
+    }
+
+    private static final ConstructingObjectParser<DelegatePkiAuthenticationResponse, Void> PARSER = new ConstructingObjectParser<>(
+            "delegate_pki_response", true,
+            args -> new DelegatePkiAuthenticationResponse((String) args[0], (String) args[1], TimeValue.timeValueSeconds((Long) args[2])));
+
+    static {
+        PARSER.declareString(constructorArg(), new ParseField("access_token"));
+        PARSER.declareString(constructorArg(), new ParseField("type"));
+        PARSER.declareLong(constructorArg(), new ParseField("expires_in"));
+    }
+
+    public static DelegatePkiAuthenticationResponse fromXContent(XContentParser parser) throws IOException {
+        return PARSER.parse(parser, null);
+    }
+}

client/rest-high-level/src/test/java/org/elasticsearch/client/SecurityRequestConvertersTests.java

@@ -26,6 +26,7 @@
 import org.elasticsearch.client.security.ChangePasswordRequest;
 import org.elasticsearch.client.security.CreateApiKeyRequest;
 import org.elasticsearch.client.security.CreateTokenRequest;
+import org.elasticsearch.client.security.DelegatePkiAuthenticationRequest;
 import org.elasticsearch.client.security.DeletePrivilegesRequest;
 import org.elasticsearch.client.security.DeleteRoleMappingRequest;
 import org.elasticsearch.client.security.DeleteRoleRequest;
@@ -58,6 +59,7 @@
 import org.elasticsearch.test.ESTestCase;
 
 import java.io.IOException;
+import java.security.cert.X509Certificate;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -67,6 +69,8 @@
 
 import static org.elasticsearch.client.RequestConvertersTests.assertToXContentBody;
 import static org.hamcrest.Matchers.equalTo;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class SecurityRequestConvertersTests extends ESTestCase {
 
@@ -304,6 +308,18 @@ public void testCreateTokenWithClientCredentialsGrant() throws Exception {
         assertToXContentBody(createTokenRequest, request.getEntity());
     }
 
+    public void testDelegatePkiAuthentication() throws Exception {
+        X509Certificate mockCertificate = mock(X509Certificate.class);
+        when(mockCertificate.getEncoded()).thenReturn(new byte[0]);
+        DelegatePkiAuthenticationRequest delegatePkiAuthenticationRequest = new DelegatePkiAuthenticationRequest(
+                Arrays.asList(mockCertificate));
+        Request request = SecurityRequestConverters.delegatePkiAuthentication(delegatePkiAuthenticationRequest);
+        assertEquals(HttpPost.METHOD_NAME, request.getMethod());
+        assertEquals("/_security/delegate_pki", request.getEndpoint());
+        assertEquals(0, request.getParameters().size());
+        assertToXContentBody(delegatePkiAuthenticationRequest, request.getEntity());
+    }
+
     public void testGetApplicationPrivilege() throws Exception {
         final String application = randomAlphaOfLength(6);
         final String privilege = randomAlphaOfLength(4);