Github user alopresto commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2085#discussion_r174658418
--- Diff:
nifi-nar-bundles/nifi-oauth-bundle/nifi-oauth/src/main/java/org/apache/nifi/oauth/OAuth2ClientCredentialsGrantControllerService.java
---
@@ -0,0 +1,167 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.
+ * <p>
+ * Created on 7/25/17.
+ */
+
+package org.apache.nifi.oauth;
+
+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnDisabled;
+import org.apache.nifi.annotation.lifecycle.OnEnabled;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.oauth.httpclient.OAuthHTTPConnectionClient;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.reporting.InitializationException;
+import org.apache.oltu.oauth2.client.HttpClient;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest;
+import org.apache.oltu.oauth2.common.exception.OAuthProblemException;
+import org.apache.oltu.oauth2.common.exception.OAuthSystemException;
+import org.apache.oltu.oauth2.common.message.types.GrantType;
+
+@Tags({ "oauth2", "client", "secret", "post"})
+@CapabilityDescription("POSTs the ClientId and ClientSecret to the OAuth2
authentication server to retrieve the" +
+ " access token. The access token is stored locally in the
controller service and used by processors " +
+ "referencing this controller service.")
+public class OAuth2ClientCredentialsGrantControllerService
+ extends AbstractOAuthControllerService
+ implements OAuth2ClientService {
+
+ public static final PropertyDescriptor CLIENT_ID = new
PropertyDescriptor
+ .Builder().name("OAuth2 Client ID")
+ .displayName("OAuth2 Client ID")
+ .description("OAuth2 Client ID passed to the authorization
server")
+ .required(true)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor CLIENT_SECRET = new
PropertyDescriptor
+ .Builder().name("OAuth2 Client Secret")
+ .displayName("OAuth2 Client Secret")
+ .description("OAuth2 Client Secret that will be passed to the
authorization server in exchange for an access token")
+ .sensitive(true)
+ .required(true)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ private static final List<PropertyDescriptor> properties;
+
+ static {
+ final List<PropertyDescriptor> props = new ArrayList<>();
+ props.add(AUTH_SERVER_URL);
+ props.add(CLIENT_ID);
+ props.add(CLIENT_SECRET);
+ props.add(RESPONSE_ACCESS_TOKEN_FIELD_NAME);
+ props.add(RESPONSE_EXPIRE_TIME_FIELD_NAME);
+ props.add(RESPONSE_EXPIRE_IN_FIELD_NAME);
+ props.add(RESPONSE_SCOPE_FIELD_NAME);
+ props.add(RESPONSE_TOKEN_TYPE_FIELD_NAME);
+ properties = Collections.unmodifiableList(props);
+ }
+
+ @Override
+ protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+ return properties;
+ }
+
+ private String clientId = null;
+ private String clientSecret = null;
+ private Base64.Encoder enc = Base64.getEncoder();
+
+ /**
+ * @param context the configuration context
+ * @throws InitializationException if unable to create a database
connection
+ */
+ @OnEnabled
+ public void onEnabled(final ConfigurationContext context) throws
InitializationException {
+
+ super.onEnabled(context);
+
+ clientId = context.getProperty(CLIENT_ID).getValue();
+ clientSecret = context.getProperty(CLIENT_SECRET).getValue();
+ }
+
+ public boolean authenticate() {
+ HttpClient con = null;
+
+ try {
+
+ String base64String = enc.encodeToString((clientId + ":" +
clientSecret).getBytes());
--- End diff --
From [Understanding
OAuth2](http://www.bubblecode.net/en/2016/01/22/understanding-oauth2/):
> HTTPS
> OAuth2 requires the use of HTTPS for communication between the client and
the authorization server because of sensitive data passing between the two
(tokens and possibly resource owner credentials). In fact you are not forced to
do so if you implement your own authorization server but you must know that you
are opening a big security hole by doing this.
---
