/*
    *
    * 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;
  
  import java.io.IOException;
  import java.security.PrivilegedAction;
  import java.security.PrivilegedExceptionAction;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ExecutionException;
  import com.google.common.cache.LoadingCache;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Methods;
  import org.apache.hadoop.security.Groups;
  import org.apache.hadoop.security.SecurityUtil;
  import org.apache.hadoop.security.UserGroupInformation;
  import org.apache.hadoop.security.token.Token;
  import org.apache.hadoop.security.token.TokenIdentifier;
  
  /**
   * Wrapper to abstract out usage of user and group information in HBase.
   *
   * <p>
   * This class provides a common interface for interacting with user and group
   * information across changing APIs in different versions of Hadoop.  It only
   * provides access to the common set of functionality in
   * {@link org.apache.hadoop.security.UserGroupInformation} currently needed by
   * HBase, but can be extended as needs change.
   * </p>
   */
  @InterfaceAudience.Public
  @InterfaceStability.Stable
  public abstract class User {
    public static final String HBASE_SECURITY_CONF_KEY =
        "hbase.security.authentication";
    public static final String HBASE_SECURITY_AUTHORIZATION_CONF_KEY =
        "hbase.security.authorization";
  
    protected UserGroupInformation ugi;
  
    public UserGroupInformation getUGI() {
      return ugi;
    }
  
    /**
     * Returns the full user name.  For Kerberos principals this will include
     * the host and realm portions of the principal name.
     *
     * @return User full name.
     */
    public String getName() {
      return ugi.getUserName();
    }
  
    /**
     * Returns the list of groups of which this user is a member.  On secure
     * Hadoop this returns the group information for the user as resolved on the
     * server.  For 0.20 based Hadoop, the group names are passed from the client.
     */
    public String[] getGroupNames() {
      return ugi.getGroupNames();
    }
  
    /**
     * Returns the shortened version of the user name -- the portion that maps
     * to an operating system user name.
     *
     * @return Short name
     */
    public abstract String getShortName();
  
    /**
     * Executes the given action within the context of this user.
     */
    public abstract <T> T runAs(PrivilegedAction<T> action);
  
    /**
    * Executes the given action within the context of this user.
    */
   public abstract <T> T runAs(PrivilegedExceptionAction<T> action)
       throws IOException, InterruptedException;
 
   /**
    * Returns the Token of the specified kind associated with this user,
    * or null if the Token is not present.
    *
    * @param kind the kind of token
    * @param service service on which the token is supposed to be used
    * @return the token of the specified kind.
    */
   public Token<?> getToken(String kind, String service) throws IOException {
     for (Token<?> token : ugi.getTokens()) {
       if (token.getKind().toString().equals(kind) &&
           (service != null && token.getService().toString().equals(service))) {
         return token;
       }
     }
     return null;
   }
 
   /**
    * Returns all the tokens stored in the user's credentials.
    */
   public Collection<Token<? extends TokenIdentifier>> getTokens() {
     return ugi.getTokens();
   }
 
   /**
    * Adds the given Token to the user's credentials.
    *
    * @param token the token to add
    */
   public void addToken(Token<? extends TokenIdentifier> token) {
     ugi.addToken(token);
   }
 
   @Override
   public boolean equals(Object o) {
     if (this == o) {
       return true;
     }
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
     return ugi.equals(((User) o).ugi);
   }
 
   @Override
   public int hashCode() {
     return ugi.hashCode();
   }
 
   @Override
   public String toString() {
     return ugi.toString();
   }
 
   /**
    * Returns the {@code User} instance within current execution context.
    */
   public static User getCurrent() throws IOException {
     User user = new SecureHadoopUser();
     if (user.getUGI() == null) {
       return null;
     }
     return user;
   }
 
   /**
    * Executes the given action as the login user
    * @param action
    * @return the result of the action
    * @throws IOException
    */
   @SuppressWarnings({ "rawtypes", "unchecked" })
   public static <T> T runAsLoginUser(PrivilegedExceptionAction<T> action) throws IOException {
     try {
       Class c = Class.forName("org.apache.hadoop.security.SecurityUtil");
       Class [] types = new Class[]{PrivilegedExceptionAction.class};
       Object[] args = new Object[]{action};
       return (T) Methods.call(c, null, "doAsLoginUser", types, args);
     } catch (Throwable e) {
       throw new IOException(e);
     }
   }
 
   /**
    * Wraps an underlying {@code UserGroupInformation} instance.
    * @param ugi The base Hadoop user
    * @return User
    */
   public static User create(UserGroupInformation ugi) {
     if (ugi == null) {
       return null;
     }
     return new SecureHadoopUser(ugi);
   }
 
   /**
    * Generates a new {@code User} instance specifically for use in test code.
    * @param name the full username
    * @param groups the group names to which the test user will belong
    * @return a new <code>User</code> instance
    */
   public static User createUserForTesting(Configuration conf,
       String name, String[] groups) {
     User userForTesting = SecureHadoopUser.createUserForTesting(conf, name, groups);
     return userForTesting;
   }
 
   /**
    * Log in the current process using the given configuration keys for the
    * credential file and login principal.
    *
    * <p><strong>This is only applicable when
    * running on secure Hadoop</strong> -- see
    * org.apache.hadoop.security.SecurityUtil#login(Configuration,String,String,String).
    * On regular Hadoop (without security features), this will safely be ignored.
    * </p>
    *
    * @param conf The configuration data to use
    * @param fileConfKey Property key used to configure path to the credential file
    * @param principalConfKey Property key used to configure login principal
    * @param localhost Current hostname to use in any credentials
    * @throws IOException underlying exception from SecurityUtil.login() call
    */
   public static void login(Configuration conf, String fileConfKey,
       String principalConfKey, String localhost) throws IOException {
     SecureHadoopUser.login(conf, fileConfKey, principalConfKey, localhost);
   }
 
   /**
    * Returns whether or not Kerberos authentication is configured for Hadoop.
    * For non-secure Hadoop, this always returns <code>false</code>.
    * For secure Hadoop, it will return the value from
    * {@code UserGroupInformation.isSecurityEnabled()}.
    */
   public static boolean isSecurityEnabled() {
     return SecureHadoopUser.isSecurityEnabled();
   }
 
   /**
    * Returns whether or not secure authentication is enabled for HBase. Note that
    * HBase security requires HDFS security to provide any guarantees, so it is
    * recommended that secure HBase should run on secure HDFS.
    */
   public static boolean isHBaseSecurityEnabled(Configuration conf) {
     return "kerberos".equalsIgnoreCase(conf.get(HBASE_SECURITY_CONF_KEY));
   }
 
   /* Concrete implementations */
 
   /**
    * Bridges {@code User} invocations to underlying calls to
    * {@link org.apache.hadoop.security.UserGroupInformation} for secure Hadoop
    * 0.20 and versions 0.21 and above.
    */
   @InterfaceAudience.Private
    public static final class SecureHadoopUser extends User {
     private String shortName;
     private LoadingCache<String, String[]> cache;
 
     public SecureHadoopUser() throws IOException {
       ugi = UserGroupInformation.getCurrentUser();
       this.cache = null;
     }
 
     public SecureHadoopUser(UserGroupInformation ugi) {
       this.ugi = ugi;
       this.cache = null;
     }
 
     public SecureHadoopUser(UserGroupInformation ugi,
                             LoadingCache<String, String[]> cache) {
       this.ugi = ugi;
       this.cache = cache;
     }
 
     @Override
     public String getShortName() {
       if (shortName != null) return shortName;
       try {
         shortName = ugi.getShortUserName();
         return shortName;
       } catch (Exception e) {
         throw new RuntimeException("Unexpected error getting user short name",
           e);
       }
     }
 
     @Override
     public String[] getGroupNames() {
       if (cache != null) {
         try {
           return this.cache.get(getShortName());
         } catch (ExecutionException e) {
           return new String[0];
         }
       }
       return ugi.getGroupNames();
     }
 
     @Override
     public <T> T runAs(PrivilegedAction<T> action) {
       return ugi.doAs(action);
     }
 
     @Override
     public <T> T runAs(PrivilegedExceptionAction<T> action)
         throws IOException, InterruptedException {
       return ugi.doAs(action);
     }
 
     /** @see User#createUserForTesting(org.apache.hadoop.conf.Configuration, String, String[]) */
     public static User createUserForTesting(Configuration conf,
         String name, String[] groups) {
       synchronized (UserProvider.class) {
         if (!(UserProvider.groups instanceof TestingGroups)) {
           UserProvider.groups = new TestingGroups(UserProvider.groups);
         }
       }
 
       ((TestingGroups)UserProvider.groups).setUserGroups(name, groups);
       return new SecureHadoopUser(UserGroupInformation.createUserForTesting(name, groups));
     }
 
     /**
      * Obtain credentials for the current process using the configured
      * Kerberos keytab file and principal.
      * @see User#login(org.apache.hadoop.conf.Configuration, String, String, String)
      *
      * @param conf the Configuration to use
      * @param fileConfKey Configuration property key used to store the path
      * to the keytab file
      * @param principalConfKey Configuration property key used to store the
      * principal name to login as
      * @param localhost the local hostname
      */
     public static void login(Configuration conf, String fileConfKey,
         String principalConfKey, String localhost) throws IOException {
       if (isSecurityEnabled()) {
         SecurityUtil.login(conf, fileConfKey, principalConfKey, localhost);
       }
     }
 
     /**
      * Returns the result of {@code UserGroupInformation.isSecurityEnabled()}.
      */
     public static boolean isSecurityEnabled() {
       return UserGroupInformation.isSecurityEnabled();
     }
   }
 
   static class TestingGroups extends Groups {
     private final Map<String, List<String>> userToGroupsMapping =
         new HashMap<String,List<String>>();
     private Groups underlyingImplementation;
 
     TestingGroups(Groups underlyingImplementation) {
       super(new Configuration());
       this.underlyingImplementation = underlyingImplementation;
     }
 
     @Override
     public List<String> getGroups(String user) throws IOException {
       List<String> result = userToGroupsMapping.get(user);
 
       if (result == null) {
         result = underlyingImplementation.getGroups(user);
       }
 
       return result;
     }
 
     private void setUserGroups(String user, String[] groups) {
       userToGroupsMapping.put(user, Arrays.asList(groups));
     }
   }
 }