/*
    * 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.access;
  
  import java.io.ByteArrayInputStream;
  import java.io.DataInput;
  import java.io.DataInputStream;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.hadoop.hbase.HColumnDescriptor;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.catalog.MetaReader;
  import org.apache.hadoop.hbase.client.Delete;
  import org.apache.hadoop.hbase.client.Get;
  import org.apache.hadoop.hbase.client.HTable;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.ResultScanner;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
  import org.apache.hadoop.hbase.filter.QualifierFilter;
  import org.apache.hadoop.hbase.filter.RegexStringComparator;
  import org.apache.hadoop.hbase.io.compress.Compression;
  import org.apache.hadoop.hbase.master.MasterServices;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.AccessControlProtos;
  import org.apache.hadoop.hbase.regionserver.BloomType;
  import org.apache.hadoop.hbase.regionserver.HRegion;
  import org.apache.hadoop.hbase.regionserver.InternalScanner;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.hadoop.io.Text;
  
  import com.google.common.collect.ArrayListMultimap;
  import com.google.common.collect.ListMultimap;
  import com.google.protobuf.InvalidProtocolBufferException;
  
  /**
   * Maintains lists of permission grants to users and groups to allow for
   * authorization checks by {@link AccessController}.
   *
   * <p>
   * Access control lists are stored in an "internal" metadata table named
   * {@code _acl_}. Each table's permission grants are stored as a separate row,
   * keyed by the table name. KeyValues for permissions assignments are stored
   * in one of the formats:
   * <pre>
   * Key                      Desc
   * --------                 --------
   * user                     table level permissions for a user [R=read, W=write]
   * group                    table level permissions for a group
   * user,family              column family level permissions for a user
   * group,family             column family level permissions for a group
   * user,family,qualifier    column qualifier level permissions for a user
   * group,family,qualifier   column qualifier level permissions for a group
   * </pre>
   * All values are encoded as byte arrays containing the codes from the
   * org.apache.hadoop.hbase.security.access.TablePermission.Action enum.
   * </p>
   */
  public class AccessControlLists {
    /** Internal storage table for access control lists */
    public static final String ACL_TABLE_NAME_STR = "_acl_";
    public static final byte[] ACL_TABLE_NAME = Bytes.toBytes(ACL_TABLE_NAME_STR);
    public static final byte[] ACL_GLOBAL_NAME = ACL_TABLE_NAME;
    /** Column family used to store ACL grants */
    public static final String ACL_LIST_FAMILY_STR = "l";
    public static final byte[] ACL_LIST_FAMILY = Bytes.toBytes(ACL_LIST_FAMILY_STR);
  
    /** Table descriptor for ACL internal table */
    public static final HTableDescriptor ACL_TABLEDESC = new HTableDescriptor(
       ACL_TABLE_NAME);
   static {
     ACL_TABLEDESC.addFamily(
         new HColumnDescriptor(ACL_LIST_FAMILY,
             10, // Ten is arbitrary number.  Keep versions to help debugging.
             Compression.Algorithm.NONE.getName(), true, true, 8 * 1024,
             HConstants.FOREVER, BloomType.NONE.toString(),
             HConstants.REPLICATION_SCOPE_LOCAL));
   }
 
   /**
    * Delimiter to separate user, column family, and qualifier in
    * _acl_ table info: column keys */
   public static final char ACL_KEY_DELIMITER = ',';
   /** Prefix character to denote group names */
   public static final String GROUP_PREFIX = "@";
   /** Configuration key for superusers */
   public static final String SUPERUSER_CONF_KEY = "hbase.superuser";
 
   private static Log LOG = LogFactory.getLog(AccessControlLists.class);
 
   /**
    * Check for existence of {@code _acl_} table and create it if it does not exist
    * @param master reference to HMaster
    */
   static void init(MasterServices master) throws IOException {
     if (!MetaReader.tableExists(master.getCatalogTracker(), ACL_TABLE_NAME_STR)) {
       master.createTable(ACL_TABLEDESC, null);
     }
   }
 
   /**
    * Stores a new user permission grant in the access control lists table.
    * @param conf the configuration
    * @param userPerm the details of the permission to be granted
    * @throws IOException in the case of an error accessing the metadata table
    */
   static void addUserPermission(Configuration conf, UserPermission userPerm)
       throws IOException {
     Permission.Action[] actions = userPerm.getActions();
 
     Put p = new Put(userPerm.isGlobal() ? ACL_GLOBAL_NAME : userPerm.getTable());
     byte[] key = userPermissionKey(userPerm);
 
     if ((actions == null) || (actions.length == 0)) {
       String msg = "No actions associated with user '" + Bytes.toString(userPerm.getUser()) + "'";
       LOG.warn(msg);
       throw new IOException(msg);
     }
 
     byte[] value = new byte[actions.length];
     for (int i = 0; i < actions.length; i++) {
       value[i] = actions[i].code();
     }
     p.add(ACL_LIST_FAMILY, key, value);
     if (LOG.isDebugEnabled()) {
       LOG.debug("Writing permission for table "+
           Bytes.toString(userPerm.getTable())+" "+
           Bytes.toString(key)+": "+Bytes.toStringBinary(value)
       );
     }
     HTable acls = null;
     try {
       acls = new HTable(conf, ACL_TABLE_NAME);
       acls.put(p);
     } finally {
       if (acls != null) acls.close();
     }
   }
 
   /**
    * Removes a previously granted permission from the stored access control
    * lists.  The {@link TablePermission} being removed must exactly match what
    * is stored -- no wildcard matching is attempted.  Ie, if user "bob" has
    * been granted "READ" access to the "data" table, but only to column family
    * plus qualifier "info:colA", then trying to call this method with only
    * user "bob" and the table name "data" (but without specifying the
    * column qualifier "info:colA") will have no effect.
    *
    * @param conf the configuration
    * @param userPerm the details of the permission to be revoked
    * @throws IOException if there is an error accessing the metadata table
    */
   static void removeUserPermission(Configuration conf, UserPermission userPerm)
       throws IOException {
 
     Delete d = new Delete(userPerm.isGlobal() ? ACL_GLOBAL_NAME : userPerm.getTable());
     byte[] key = userPermissionKey(userPerm);
 
     if (LOG.isDebugEnabled()) {
       LOG.debug("Removing permission "+ userPerm.toString());
     }
     d.deleteColumns(ACL_LIST_FAMILY, key);
     HTable acls = null;
     try {
       acls = new HTable(conf, ACL_TABLE_NAME);
       acls.delete(d);
     } finally {
       if (acls != null) acls.close();
     }
   }
 
   /**
    * Remove specified table from the _acl_ table.
    */
   static void removeTablePermissions(Configuration conf, byte[] tableName)
       throws IOException{
     Delete d = new Delete(tableName);
 
     if (LOG.isDebugEnabled()) {
       LOG.debug("Removing permissions of removed table "+ Bytes.toString(tableName));
     }
 
     HTable acls = null;
     try {
       acls = new HTable(conf, ACL_TABLE_NAME);
       acls.delete(d);
     } finally {
       if (acls != null) acls.close();
     }
   }
 
   /**
    * Remove specified table column from the _acl_ table.
    */
   static void removeTablePermissions(Configuration conf, byte[] tableName, byte[] column)
       throws IOException{
 
     if (LOG.isDebugEnabled()) {
       LOG.debug("Removing permissions of removed column " + Bytes.toString(column) +
                 " from table "+ Bytes.toString(tableName));
     }
 
     HTable acls = null;
     try {
       acls = new HTable(conf, ACL_TABLE_NAME);
 
       Scan scan = new Scan();
       scan.addFamily(ACL_LIST_FAMILY);
 
       String columnName = Bytes.toString(column);
       scan.setFilter(new QualifierFilter(CompareOp.EQUAL, new RegexStringComparator(
                      String.format("(%s%s%s)|(%s%s)$",
                      ACL_KEY_DELIMITER, columnName, ACL_KEY_DELIMITER,
                      ACL_KEY_DELIMITER, columnName))));
 
       Set<byte[]> qualifierSet = new TreeSet<byte[]>(Bytes.BYTES_COMPARATOR);
       ResultScanner scanner = acls.getScanner(scan);
       try {
         for (Result res : scanner) {
           for (byte[] q : res.getFamilyMap(ACL_LIST_FAMILY).navigableKeySet()) {
             qualifierSet.add(q);
           }
         }
       } finally {
         scanner.close();
       }
 
       if (qualifierSet.size() > 0) {
         Delete d = new Delete(tableName);
         for (byte[] qualifier : qualifierSet) {
           d.deleteColumns(ACL_LIST_FAMILY, qualifier);
         }
         acls.delete(d);
       }
     } finally {
       if (acls != null) acls.close();
     }
   }
 
   /**
    * Build qualifier key from user permission:
    *  username
    *  username,family
    *  username,family,qualifier
    */
   static byte[] userPermissionKey(UserPermission userPerm) {
     byte[] qualifier = userPerm.getQualifier();
     byte[] family = userPerm.getFamily();
     byte[] key = userPerm.getUser();
 
     if (family != null && family.length > 0) {
       key = Bytes.add(key, Bytes.add(new byte[]{ACL_KEY_DELIMITER}, family));
       if (qualifier != null && qualifier.length > 0) {
         key = Bytes.add(key, Bytes.add(new byte[]{ACL_KEY_DELIMITER}, qualifier));
       }
     }
 
     return key;
   }
 
   /**
    * Returns {@code true} if the given region is part of the {@code _acl_}
    * metadata table.
    */
   static boolean isAclRegion(HRegion region) {
     return Bytes.equals(ACL_TABLE_NAME, region.getTableDesc().getName());
   }
 
   /**
    * Returns {@code true} if the given table is {@code _acl_} metadata table.
    */
   static boolean isAclTable(HTableDescriptor desc) {
     return Bytes.equals(ACL_TABLE_NAME, desc.getName());
   }
 
   /**
    * Loads all of the permission grants stored in a region of the {@code _acl_}
    * table.
    *
    * @param aclRegion
    * @return a map of the permissions for this table.
    * @throws IOException
    */
   static Map<byte[],ListMultimap<String,TablePermission>> loadAll(
       HRegion aclRegion)
     throws IOException {
 
     if (!isAclRegion(aclRegion)) {
       throw new IOException("Can only load permissions from "+ACL_TABLE_NAME_STR);
     }
 
     Map<byte[],ListMultimap<String,TablePermission>> allPerms =
         new TreeMap<byte[],ListMultimap<String,TablePermission>>(Bytes.BYTES_COMPARATOR);
 
     // do a full scan of _acl_ table
 
     Scan scan = new Scan();
     scan.addFamily(ACL_LIST_FAMILY);
 
     InternalScanner iScanner = null;
     try {
       iScanner = aclRegion.getScanner(scan);
 
       while (true) {
         List<KeyValue> row = new ArrayList<KeyValue>();
 
         boolean hasNext = iScanner.next(row);
         ListMultimap<String,TablePermission> perms = ArrayListMultimap.create();
         byte[] table = null;
         for (KeyValue kv : row) {
           if (table == null) {
             table = kv.getRow();
           }
           Pair<String,TablePermission> permissionsOfUserOnTable =
               parseTablePermissionRecord(table, kv);
           if (permissionsOfUserOnTable != null) {
             String username = permissionsOfUserOnTable.getFirst();
             TablePermission permissions = permissionsOfUserOnTable.getSecond();
             perms.put(username, permissions);
           }
         }
         if (table != null) {
           allPerms.put(table, perms);
         }
         if (!hasNext) {
           break;
         }
       }
     } finally {
       if (iScanner != null) {
         iScanner.close();
       }
     }
 
     return allPerms;
   }
 
   /**
    * Load all permissions from the region server holding {@code _acl_},
    * primarily intended for testing purposes.
    */
   static Map<byte[],ListMultimap<String,TablePermission>> loadAll(
       Configuration conf) throws IOException {
     Map<byte[],ListMultimap<String,TablePermission>> allPerms =
         new TreeMap<byte[],ListMultimap<String,TablePermission>>(Bytes.BYTES_COMPARATOR);
 
     // do a full scan of _acl_, filtering on only first table region rows
 
     Scan scan = new Scan();
     scan.addFamily(ACL_LIST_FAMILY);
 
     HTable acls = null;
     ResultScanner scanner = null;
     try {
       acls = new HTable(conf, ACL_TABLE_NAME);
       scanner = acls.getScanner(scan);
       for (Result row : scanner) {
         ListMultimap<String,TablePermission> resultPerms =
             parseTablePermissions(row.getRow(), row);
         allPerms.put(row.getRow(), resultPerms);
       }
     } finally {
       if (scanner != null) scanner.close();
       if (acls != null) acls.close();
     }
 
     return allPerms;
   }
 
   /**
    * Reads user permission assignments stored in the <code>l:</code> column
    * family of the first table row in <code>_acl_</code>.
    *
    * <p>
    * See {@link AccessControlLists class documentation} for the key structure
    * used for storage.
    * </p>
    */
   static ListMultimap<String, TablePermission> getTablePermissions(Configuration conf,
       byte[] tableName) throws IOException {
     if (tableName == null) tableName = ACL_TABLE_NAME;
 
     // for normal user tables, we just read the table row from _acl_
     ListMultimap<String, TablePermission> perms = ArrayListMultimap.create();
     HTable acls = null;
     try {
       acls = new HTable(conf, ACL_TABLE_NAME);
       Get get = new Get(tableName);
       get.addFamily(ACL_LIST_FAMILY);
       Result row = acls.get(get);
       if (!row.isEmpty()) {
         perms = parseTablePermissions(tableName, row);
       } else {
         LOG.info("No permissions found in " + ACL_TABLE_NAME_STR + " for table "
             + Bytes.toString(tableName));
       }
     } finally {
       if (acls != null) acls.close();
     }
 
     return perms;
   }
 
   /**
    * Returns the currently granted permissions for a given table as a list of
    * user plus associated permissions.
    */
   static List<UserPermission> getUserPermissions(
       Configuration conf, byte[] tableName)
   throws IOException {
     ListMultimap<String,TablePermission> allPerms = getTablePermissions(
       conf, tableName);
 
     List<UserPermission> perms = new ArrayList<UserPermission>();
 
     for (Map.Entry<String, TablePermission> entry : allPerms.entries()) {
       UserPermission up = new UserPermission(Bytes.toBytes(entry.getKey()),
           entry.getValue().getTable(), entry.getValue().getFamily(),
           entry.getValue().getQualifier(), entry.getValue().getActions());
       perms.add(up);
     }
     return perms;
   }
 
   private static ListMultimap<String,TablePermission> parseTablePermissions(
       byte[] table, Result result) {
     ListMultimap<String,TablePermission> perms = ArrayListMultimap.create();
     if (result != null && result.size() > 0) {
       for (KeyValue kv : result.raw()) {
 
         Pair<String,TablePermission> permissionsOfUserOnTable =
             parseTablePermissionRecord(table, kv);
 
         if (permissionsOfUserOnTable != null) {
           String username = permissionsOfUserOnTable.getFirst();
           TablePermission permissions = permissionsOfUserOnTable.getSecond();
           perms.put(username, permissions);
         }
       }
     }
     return perms;
   }
 
   private static Pair<String,TablePermission> parseTablePermissionRecord(
       byte[] table, KeyValue kv) {
     // return X given a set of permissions encoded in the permissionRecord kv.
     byte[] family = kv.getFamily();
 
     if (!Bytes.equals(family, ACL_LIST_FAMILY)) {
       return null;
     }
 
     byte[] key = kv.getQualifier();
     byte[] value = kv.getValue();
     if (LOG.isDebugEnabled()) {
       LOG.debug("Read acl: kv ["+
                 Bytes.toStringBinary(key)+": "+
                 Bytes.toStringBinary(value)+"]");
     }
 
     // check for a column family appended to the key
     // TODO: avoid the string conversion to make this more efficient
     String username = Bytes.toString(key);
     int idx = username.indexOf(ACL_KEY_DELIMITER);
     byte[] permFamily = null;
     byte[] permQualifier = null;
     if (idx > 0 && idx < username.length()-1) {
       String remainder = username.substring(idx+1);
       username = username.substring(0, idx);
       idx = remainder.indexOf(ACL_KEY_DELIMITER);
       if (idx > 0 && idx < remainder.length()-1) {
         permFamily = Bytes.toBytes(remainder.substring(0, idx));
         permQualifier = Bytes.toBytes(remainder.substring(idx+1));
       } else {
         permFamily = Bytes.toBytes(remainder);
       }
     }
 
     return new Pair<String,TablePermission>(
         username, new TablePermission(table, permFamily, permQualifier, value));
   }
 
   /**
    * Writes a set of permissions as {@link org.apache.hadoop.io.Writable} instances
    * and returns the resulting byte array.
    *
    * Writes a set of permission [user: table permission]
    */
   public static byte[] writePermissionsAsBytes(ListMultimap<String, TablePermission> perms,
       Configuration conf) {
     return ProtobufUtil.prependPBMagic(ProtobufUtil.toUserTablePermissions(perms).toByteArray());
   }
 
   /**
    * Reads a set of permissions as {@link org.apache.hadoop.io.Writable} instances
    * from the input stream.
    */
   public static ListMultimap<String, TablePermission> readPermissions(byte[] data,
       Configuration conf)
   throws DeserializationException {
     if (ProtobufUtil.isPBMagicPrefix(data)) {
       int pblen = ProtobufUtil.lengthOfPBMagic();
       try {
         AccessControlProtos.UserTablePermissions perms =
           AccessControlProtos.UserTablePermissions.newBuilder().mergeFrom(
             data, pblen, data.length - pblen).build();
         return ProtobufUtil.toUserTablePermissions(perms);
       } catch (InvalidProtocolBufferException e) {
         throw new DeserializationException(e);
       }
     } else {
       ListMultimap<String,TablePermission> perms = ArrayListMultimap.create();
       try {
         DataInput in = new DataInputStream(new ByteArrayInputStream(data));
         int length = in.readInt();
         for (int i=0; i<length; i++) {
           String user = Text.readString(in);
           List<TablePermission> userPerms =
             (List)HbaseObjectWritableFor96Migration.readObject(in, conf);
           perms.putAll(user, userPerms);
         }
       } catch (IOException e) {
         throw new DeserializationException(e);
       }
       return perms;
     }
   }
 
   /**
    * Returns whether or not the given name should be interpreted as a group
    * principal.  Currently this simply checks if the name starts with the
    * special group prefix character ("@").
    */
   public static boolean isGroupPrincipal(String name) {
     return name != null && name.startsWith(GROUP_PREFIX);
   }
 
   /**
    * Returns the actual name for a group principal (stripped of the
    * group prefix).
    */
   public static String getGroupName(String aclKey) {
     if (!isGroupPrincipal(aclKey)) {
       return aclKey;
     }
 
     return aclKey.substring(GROUP_PREFIX.length());
   }
 }