/*
 * 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
 *
 *     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.apache.hadoop.hbase.security.token;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.Coprocessor;
import org.apache.hadoop.hbase.CoprocessorEnvironment;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
import org.apache.hadoop.hbase.ipc.RpcServer;
import org.apache.hadoop.hbase.ipc.RpcServerInterface;
import org.apache.hadoop.hbase.protobuf.generated.AuthenticationProtos;
import org.apache.hadoop.hbase.security.AccessDeniedException;
import org.apache.hadoop.hbase.security.User;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.UserGroupInformation.AuthenticationMethod;
import org.apache.hadoop.security.token.SecretManager;
import org.apache.hadoop.security.token.Token;

import com.google.protobuf.RpcCallback;
import com.google.protobuf.RpcController;
import com.google.protobuf.Service;

/**
 * Provides a service for obtaining authentication tokens via the
 * {@link AuthenticationProtos} AuthenticationService coprocessor service.
 */
@InterfaceAudience.Private
public class TokenProvider implements AuthenticationProtos.AuthenticationService.Interface,
    Coprocessor, CoprocessorService {

  private static final Log LOG = LogFactory.getLog(TokenProvider.class);

  private AuthenticationTokenSecretManager secretManager;


  @Override
  public void start(CoprocessorEnvironment env) {
    // if running at region
    if (env instanceof RegionCoprocessorEnvironment) {
      RegionCoprocessorEnvironment regionEnv =
          (RegionCoprocessorEnvironment)env;
      RpcServerInterface server = regionEnv.getRegionServerServices().getRpcServer();
      SecretManager<?> mgr = ((RpcServer)server).getSecretManager();
      if (mgr instanceof AuthenticationTokenSecretManager) {
        secretManager = (AuthenticationTokenSecretManager)mgr;
      }
    }
  }

  @Override
  public void stop(CoprocessorEnvironment env) throws IOException {
  }

  /**
   * @param ugi A user group information.
   * @return true if delegation token operation is allowed
   */
  private boolean isAllowedDelegationTokenOp(UserGroupInformation ugi) throws IOException {
    AuthenticationMethod authMethod = ugi.getAuthenticationMethod();
    if (authMethod == AuthenticationMethod.PROXY) {
      authMethod = ugi.getRealUser().getAuthenticationMethod();
    }
    if (authMethod != AuthenticationMethod.KERBEROS
        && authMethod != AuthenticationMethod.KERBEROS_SSL
        && authMethod != AuthenticationMethod.CERTIFICATE) {
      return false;
    }
    return true;
  }

  // AuthenticationService implementation

  @Override
  public Service getService() {
    return AuthenticationProtos.AuthenticationService.newReflectiveService(this);
  }

  @Override
  public void getAuthenticationToken(RpcController controller,
                                     AuthenticationProtos.GetAuthenticationTokenRequest request,
                                     RpcCallback<AuthenticationProtos.GetAuthenticationTokenResponse> done) {
    AuthenticationProtos.GetAuthenticationTokenResponse.Builder response =
        AuthenticationProtos.GetAuthenticationTokenResponse.newBuilder();

    try {
      if (secretManager == null) {
        throw new IOException(
            "No secret manager configured for token authentication");
      }

      User currentUser = RpcServer.getRequestUser();
      UserGroupInformation ugi = null;
      if (currentUser != null) {
        ugi = currentUser.getUGI();
      }
      if (currentUser == null) {
        throw new AccessDeniedException("No authenticated user for request!");
      } else if (!isAllowedDelegationTokenOp(ugi)) {
        LOG.warn("Token generation denied for user="+currentUser.getName()
            +", authMethod="+ugi.getAuthenticationMethod());
        throw new AccessDeniedException(
            "Token generation only allowed for Kerberos authenticated clients");
      }

      Token<AuthenticationTokenIdentifier> token =
          secretManager.generateToken(currentUser.getName());
      response.setToken(TokenUtil.toToken(token)).build();
    } catch (IOException ioe) {
      CoprocessorRpcUtils.setControllerException(controller, ioe);
    }
    done.run(response.build());
  }

  @Override
  public void whoAmI(RpcController controller, AuthenticationProtos.WhoAmIRequest request,
                     RpcCallback<AuthenticationProtos.WhoAmIResponse> done) {
    User requestUser = RpcServer.getRequestUser();
    AuthenticationProtos.WhoAmIResponse.Builder response =
        AuthenticationProtos.WhoAmIResponse.newBuilder();
    if (requestUser != null) {
      response.setUsername(requestUser.getShortName());
      AuthenticationMethod method = requestUser.getUGI().getAuthenticationMethod();
      if (method != null) {
        response.setAuthMethod(method.name());
      }
    }
    done.run(response.build());
  }
}