/**
    * 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.visibility;
  
  import static org.apache.hadoop.hbase.HConstants.OperationStatusCode.SANITY_CHECK_FAILURE;
  import static org.apache.hadoop.hbase.HConstants.OperationStatusCode.SUCCESS;
  import static org.apache.hadoop.hbase.security.visibility.VisibilityConstants.LABELS_TABLE_FAMILY;
  import static org.apache.hadoop.hbase.security.visibility.VisibilityConstants.LABELS_TABLE_NAME;
  
  import java.io.IOException;
  import java.net.InetAddress;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.AuthUtil;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellScanner;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.CoprocessorEnvironment;
  import org.apache.hadoop.hbase.DoNotRetryIOException;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.HColumnDescriptor;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.MetaTableAccessor;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.Tag;
  import org.apache.hadoop.hbase.TagRewriteCell;
  import org.apache.hadoop.hbase.TagType;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.client.Append;
  import org.apache.hadoop.hbase.client.Delete;
  import org.apache.hadoop.hbase.client.Get;
  import org.apache.hadoop.hbase.client.Increment;
  import org.apache.hadoop.hbase.client.Mutation;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.constraint.ConstraintException;
  import org.apache.hadoop.hbase.coprocessor.BaseMasterAndRegionObserver;
  import org.apache.hadoop.hbase.coprocessor.BaseRegionServerObserver;
  import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
  import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
  import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
  import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
  import org.apache.hadoop.hbase.coprocessor.ObserverContext;
  import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
  import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessorEnvironment;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.hadoop.hbase.exceptions.FailedSanityCheckException;
  import org.apache.hadoop.hbase.filter.Filter;
  import org.apache.hadoop.hbase.filter.FilterBase;
  import org.apache.hadoop.hbase.filter.FilterList;
  import org.apache.hadoop.hbase.io.hfile.HFile;
  import org.apache.hadoop.hbase.ipc.RpcServer;
  import org.apache.hadoop.hbase.master.MasterServices;
  import org.apache.hadoop.hbase.protobuf.ResponseConverter;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.RegionActionResult;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.GetAuthsRequest;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.GetAuthsResponse;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.ListLabelsRequest;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.ListLabelsResponse;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.SetAuthsRequest;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.VisibilityLabel;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.VisibilityLabelsRequest;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.VisibilityLabelsResponse;
  import org.apache.hadoop.hbase.protobuf.generated.VisibilityLabelsProtos.VisibilityLabelsService;
  import org.apache.hadoop.hbase.regionserver.BloomType;
  import org.apache.hadoop.hbase.regionserver.DeleteTracker;
  import org.apache.hadoop.hbase.regionserver.DisabledRegionSplitPolicy;
  import org.apache.hadoop.hbase.regionserver.InternalScanner;
  import org.apache.hadoop.hbase.regionserver.MiniBatchOperationInProgress;
  import org.apache.hadoop.hbase.regionserver.OperationStatus;
  import org.apache.hadoop.hbase.regionserver.Region;
  import org.apache.hadoop.hbase.regionserver.RegionScanner;
  import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
 import org.apache.hadoop.hbase.security.AccessDeniedException;
 import org.apache.hadoop.hbase.security.Superusers;
 import org.apache.hadoop.hbase.security.User;
 import org.apache.hadoop.hbase.security.access.AccessController;
 import org.apache.hadoop.hbase.util.ByteStringer;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.Pair;
 
 import com.google.common.collect.Lists;
 import com.google.common.collect.MapMaker;
 import com.google.protobuf.ByteString;
 import com.google.protobuf.RpcCallback;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.Service;
 
 /**
  * Coprocessor that has both the MasterObserver and RegionObserver implemented that supports in
  * visibility labels
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
 public class VisibilityController extends BaseMasterAndRegionObserver implements
     VisibilityLabelsService.Interface, CoprocessorService {
 
   private static final Log LOG = LogFactory.getLog(VisibilityController.class);
   private static final Log AUDITLOG = LogFactory.getLog("SecurityLogger."
       + VisibilityController.class.getName());
   // flags if we are running on a region of the 'labels' table
   private boolean labelsRegion = false;
   // Flag denoting whether AcessController is available or not.
   private boolean accessControllerAvailable = false;
   private Configuration conf;
   private volatile boolean initialized = false;
   private boolean checkAuths = false;
   /** Mapping of scanner instances to the user who created them */
   private Map<InternalScanner,String> scannerOwners =
       new MapMaker().weakKeys().makeMap();
 
   private VisibilityLabelService visibilityLabelService;
 
   /** if we are active, usually true, only not true if "hbase.security.authorization"
     has been set to false in site configuration */
   boolean authorizationEnabled;
 
   // Add to this list if there are any reserved tag types
   private static ArrayList<Byte> RESERVED_VIS_TAG_TYPES = new ArrayList<Byte>();
   static {
     RESERVED_VIS_TAG_TYPES.add(TagType.VISIBILITY_TAG_TYPE);
     RESERVED_VIS_TAG_TYPES.add(TagType.VISIBILITY_EXP_SERIALIZATION_FORMAT_TAG_TYPE);
     RESERVED_VIS_TAG_TYPES.add(TagType.STRING_VIS_TAG_TYPE);
   }
 
   @Override
   public void start(CoprocessorEnvironment env) throws IOException {
     this.conf = env.getConfiguration();
 
     authorizationEnabled = conf.getBoolean(User.HBASE_SECURITY_AUTHORIZATION_CONF_KEY, true);
     if (!authorizationEnabled) {
       LOG.warn("The VisibilityController has been loaded with authorization checks disabled.");
     }
 
     if (HFile.getFormatVersion(conf) < HFile.MIN_FORMAT_VERSION_WITH_TAGS) {
       throw new RuntimeException("A minimum HFile version of " + HFile.MIN_FORMAT_VERSION_WITH_TAGS
         + " is required to persist visibility labels. Consider setting " + HFile.FORMAT_VERSION_KEY
         + " accordingly.");
     }
 
     if (env instanceof RegionServerCoprocessorEnvironment) {
       throw new RuntimeException("Visibility controller should not be configured as "
           + "'hbase.coprocessor.regionserver.classes'.");
     }
     // Do not create for master CPs
     if (!(env instanceof MasterCoprocessorEnvironment)) {
       visibilityLabelService = VisibilityLabelServiceManager.getInstance()
           .getVisibilityLabelService(this.conf);
     }
   }
 
   @Override
   public void stop(CoprocessorEnvironment env) throws IOException {
 
   }
 
   /********************************* Master related hooks **********************************/
 
   @Override
   public void postStartMaster(ObserverContext<MasterCoprocessorEnvironment> ctx) throws IOException {
     // Need to create the new system table for labels here
     MasterServices master = ctx.getEnvironment().getMasterServices();
     if (!MetaTableAccessor.tableExists(master.getConnection(), LABELS_TABLE_NAME)) {
       HTableDescriptor labelsTable = new HTableDescriptor(LABELS_TABLE_NAME);
       HColumnDescriptor labelsColumn = new HColumnDescriptor(LABELS_TABLE_FAMILY);
       labelsColumn.setBloomFilterType(BloomType.NONE);
       labelsColumn.setBlockCacheEnabled(false); // We will cache all the labels. No need of normal
                                                  // table block cache.
       labelsTable.addFamily(labelsColumn);
       // Let the "labels" table having only one region always. We are not expecting too many labels in
       // the system.
       labelsTable.setValue(HTableDescriptor.SPLIT_POLICY,
           DisabledRegionSplitPolicy.class.getName());
       labelsTable.setValue(Bytes.toBytes(HConstants.DISALLOW_WRITES_IN_RECOVERING),
           Bytes.toBytes(true));
       master.createTable(labelsTable, null, HConstants.NO_NONCE, HConstants.NO_NONCE);
     }
   }
 
   @Override
   public void preModifyTable(ObserverContext<MasterCoprocessorEnvironment> ctx,
       TableName tableName, HTableDescriptor htd) throws IOException {
     if (!authorizationEnabled) {
       return;
     }
     if (LABELS_TABLE_NAME.equals(tableName)) {
       throw new ConstraintException("Cannot alter " + LABELS_TABLE_NAME);
     }
   }
 
   @Override
   public void preAddColumn(ObserverContext<MasterCoprocessorEnvironment> ctx, TableName tableName,
       HColumnDescriptor column) throws IOException {
     if (!authorizationEnabled) {
       return;
     }
     if (LABELS_TABLE_NAME.equals(tableName)) {
       throw new ConstraintException("Cannot alter " + LABELS_TABLE_NAME);
     }
   }
 
   @Override
   public void preModifyColumn(ObserverContext<MasterCoprocessorEnvironment> ctx,
       TableName tableName, HColumnDescriptor descriptor) throws IOException {
     if (!authorizationEnabled) {
       return;
     }
     if (LABELS_TABLE_NAME.equals(tableName)) {
       throw new ConstraintException("Cannot alter " + LABELS_TABLE_NAME);
     }
   }
 
   @Override
   public void preDeleteColumn(ObserverContext<MasterCoprocessorEnvironment> ctx,
       TableName tableName, byte[] c) throws IOException {
     if (!authorizationEnabled) {
       return;
     }
     if (LABELS_TABLE_NAME.equals(tableName)) {
       throw new ConstraintException("Cannot alter " + LABELS_TABLE_NAME);
     }
   }
 
   @Override
   public void preDisableTable(ObserverContext<MasterCoprocessorEnvironment> ctx, TableName tableName)
       throws IOException {
     if (!authorizationEnabled) {
       return;
     }
     if (LABELS_TABLE_NAME.equals(tableName)) {
       throw new ConstraintException("Cannot disable " + LABELS_TABLE_NAME);
     }
   }
 
   /****************************** Region related hooks ******************************/
 
   @Override
   public void postOpen(ObserverContext<RegionCoprocessorEnvironment> e) {
     // Read the entire labels table and populate the zk
     if (e.getEnvironment().getRegion().getRegionInfo().getTable().equals(LABELS_TABLE_NAME)) {
       this.labelsRegion = true;
       this.accessControllerAvailable = CoprocessorHost.getLoadedCoprocessors()
           .contains(AccessController.class.getName());
       // Defer the init of VisibilityLabelService on labels region until it is in recovering state.
       if (!e.getEnvironment().getRegion().isRecovering()) {
         initVisibilityLabelService(e.getEnvironment());
       }
     } else {
       checkAuths = e.getEnvironment().getConfiguration()
           .getBoolean(VisibilityConstants.CHECK_AUTHS_FOR_MUTATION, false);
       initVisibilityLabelService(e.getEnvironment());
     }
   }
 
   @Override
   public void postLogReplay(ObserverContext<RegionCoprocessorEnvironment> e) {
     if (this.labelsRegion) {
       initVisibilityLabelService(e.getEnvironment());
       LOG.debug("post labels region log replay");
     }
   }
 
   private void initVisibilityLabelService(RegionCoprocessorEnvironment env) {
     try {
       this.visibilityLabelService.init(env);
       this.initialized = true;
     } catch (IOException ioe) {
       LOG.error("Error while initializing VisibilityLabelService..", ioe);
       throw new RuntimeException(ioe);
     }
   }
 
   @Override
   public void preBatchMutate(ObserverContext<RegionCoprocessorEnvironment> c,
       MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
     if (c.getEnvironment().getRegion().getRegionInfo().getTable().isSystemTable()) {
       return;
     }
     // TODO this can be made as a global LRU cache at HRS level?
     Map<String, List<Tag>> labelCache = new HashMap<String, List<Tag>>();
     for (int i = 0; i < miniBatchOp.size(); i++) {
       Mutation m = miniBatchOp.getOperation(i);
       CellVisibility cellVisibility = null;
       try {
         cellVisibility = m.getCellVisibility();
       } catch (DeserializationException de) {
         miniBatchOp.setOperationStatus(i,
             new OperationStatus(SANITY_CHECK_FAILURE, de.getMessage()));
         continue;
       }
       boolean sanityFailure = false;
       boolean modifiedTagFound = false;
       Pair<Boolean, Tag> pair = new Pair<Boolean, Tag>(false, null);
       for (CellScanner cellScanner = m.cellScanner(); cellScanner.advance();) {
         pair = checkForReservedVisibilityTagPresence(cellScanner.current(), pair);
         if (!pair.getFirst()) {
           // Don't disallow reserved tags if authorization is disabled
           if (authorizationEnabled) {
             miniBatchOp.setOperationStatus(i, new OperationStatus(SANITY_CHECK_FAILURE,
               "Mutation contains cell with reserved type tag"));
             sanityFailure = true;
           }
           break;
         } else {
           // Indicates that the cell has a the tag which was modified in the src replication cluster
           Tag tag = pair.getSecond();
           if (cellVisibility == null && tag != null) {
             // May need to store only the first one
             cellVisibility = new CellVisibility(Bytes.toString(tag.getBuffer(), tag.getTagOffset(),
                 tag.getTagLength()));
             modifiedTagFound = true;
           }
         }
       }
       if (!sanityFailure) {
         if (cellVisibility != null) {
           String labelsExp = cellVisibility.getExpression();
           List<Tag> visibilityTags = labelCache.get(labelsExp);
           if (visibilityTags == null) {
             // Don't check user auths for labels with Mutations when the user is super user
             boolean authCheck = authorizationEnabled && checkAuths && !(isSystemOrSuperUser());
             try {
               visibilityTags = this.visibilityLabelService.createVisibilityExpTags(labelsExp, true,
                   authCheck);
             } catch (InvalidLabelException e) {
               miniBatchOp.setOperationStatus(i,
                   new OperationStatus(SANITY_CHECK_FAILURE, e.getMessage()));
             }
             if (visibilityTags != null) {
               labelCache.put(labelsExp, visibilityTags);
             }
           }
           if (visibilityTags != null) {
             List<Cell> updatedCells = new ArrayList<Cell>();
             for (CellScanner cellScanner = m.cellScanner(); cellScanner.advance();) {
               Cell cell = cellScanner.current();
               List<Tag> tags = Tag.asList(cell.getTagsArray(), cell.getTagsOffset(),
                   cell.getTagsLength());
               if (modifiedTagFound) {
                 // Rewrite the tags by removing the modified tags.
                 removeReplicationVisibilityTag(tags);
               }
               tags.addAll(visibilityTags);
               Cell updatedCell = new TagRewriteCell(cell, Tag.fromList(tags));
               updatedCells.add(updatedCell);
             }
             m.getFamilyCellMap().clear();
             // Clear and add new Cells to the Mutation.
             for (Cell cell : updatedCells) {
               if (m instanceof Put) {
                 Put p = (Put) m;
                 p.add(cell);
               } else if (m instanceof Delete) {
                 Delete d = (Delete) m;
                 d.addDeleteMarker(cell);
               }
             }
           }
         }
       }
     }
   }
 
   @Override
   public void prePrepareTimeStampForDeleteVersion(
       ObserverContext<RegionCoprocessorEnvironment> ctx, Mutation delete, Cell cell,
       byte[] byteNow, Get get) throws IOException {
     // Nothing to do if we are not filtering by visibility
     if (!authorizationEnabled) {
       return;
     }
 
     CellVisibility cellVisibility = null;
     try {
       cellVisibility = delete.getCellVisibility();
     } catch (DeserializationException de) {
       throw new IOException("Invalid cell visibility specified " + delete, de);
     }
     // The check for checkForReservedVisibilityTagPresence happens in preBatchMutate happens.
     // It happens for every mutation and that would be enough.
     List<Tag> visibilityTags = new ArrayList<Tag>();
     if (cellVisibility != null) {
       String labelsExp = cellVisibility.getExpression();
       try {
         visibilityTags = this.visibilityLabelService.createVisibilityExpTags(labelsExp, false,
             false);
       } catch (InvalidLabelException e) {
         throw new IOException("Invalid cell visibility specified " + labelsExp, e);
       }
     }
     get.setFilter(new DeleteVersionVisibilityExpressionFilter(visibilityTags,
         VisibilityConstants.SORTED_ORDINAL_SERIALIZATION_FORMAT));
     List<Cell> result = ctx.getEnvironment().getRegion().get(get, false);
 
     if (result.size() < get.getMaxVersions()) {
       // Nothing to delete
       CellUtil.updateLatestStamp(cell, Long.MIN_VALUE);
       return;
     }
     if (result.size() > get.getMaxVersions()) {
       throw new RuntimeException("Unexpected size: " + result.size()
           + ". Results more than the max versions obtained.");
     }
     Cell getCell = result.get(get.getMaxVersions() - 1);
     CellUtil.setTimestamp(cell, getCell.getTimestamp());
 
     // We are bypassing here because in the HRegion.updateDeleteLatestVersionTimeStamp we would
     // update with the current timestamp after again doing a get. As the hook as already determined
     // the needed timestamp we need to bypass here.
     // TODO : See if HRegion.updateDeleteLatestVersionTimeStamp() could be
     // called only if the hook is not called.
     ctx.bypass();
   }
 
   /**
    * Checks whether cell contains any tag with type as VISIBILITY_TAG_TYPE. This
    * tag type is reserved and should not be explicitly set by user.
    *
    * @param cell
    *          - the cell under consideration
    * @param pair - an optional pair of type <Boolean, Tag> which would be reused
    *               if already set and new one will be created if null is passed
    * @return a pair<Boolean, Tag> - if the boolean is false then it indicates
    *         that the cell has a RESERVERD_VIS_TAG and with boolean as true, not
    *         null tag indicates that a string modified tag was found.
    */
   private Pair<Boolean, Tag> checkForReservedVisibilityTagPresence(Cell cell,
       Pair<Boolean, Tag> pair) throws IOException {
     if (pair == null) {
       pair = new Pair<Boolean, Tag>(false, null);
     } else {
       pair.setFirst(false);
       pair.setSecond(null);
     }
     // Bypass this check when the operation is done by a system/super user.
     // This is done because, while Replication, the Cells coming to the peer cluster with reserved
     // typed tags and this is fine and should get added to the peer cluster table
     if (isSystemOrSuperUser()) {
       // Does the cell contain special tag which indicates that the replicated
       // cell visiblilty tags
       // have been modified
       Tag modifiedTag = null;
       if (cell.getTagsLength() > 0) {
         Iterator<Tag> tagsIterator = CellUtil.tagsIterator(cell.getTagsArray(),
             cell.getTagsOffset(), cell.getTagsLength());
         while (tagsIterator.hasNext()) {
           Tag tag = tagsIterator.next();
           if (tag.getType() == TagType.STRING_VIS_TAG_TYPE) {
             modifiedTag = tag;
             break;
           }
         }
       }
       pair.setFirst(true);
       pair.setSecond(modifiedTag);
       return pair;
     }
     if (cell.getTagsLength() > 0) {
       Iterator<Tag> tagsItr = CellUtil.tagsIterator(cell.getTagsArray(), cell.getTagsOffset(),
           cell.getTagsLength());
       while (tagsItr.hasNext()) {
         if (RESERVED_VIS_TAG_TYPES.contains(tagsItr.next().getType())) {
           return pair;
         }
       }
     }
     pair.setFirst(true);
     return pair;
   }
 
   /**
    * Checks whether cell contains any tag with type as VISIBILITY_TAG_TYPE. This
    * tag type is reserved and should not be explicitly set by user. There are
    * two versions of this method one that accepts pair and other without pair.
    * In case of preAppend and preIncrement the additional operations are not
    * needed like checking for STRING_VIS_TAG_TYPE and hence the API without pair
    * could be used.
    *
    * @param cell
    * @return true or false
    * @throws IOException
    */
   private boolean checkForReservedVisibilityTagPresence(Cell cell) throws IOException {
     // Bypass this check when the operation is done by a system/super user.
     // This is done because, while Replication, the Cells coming to the peer
     // cluster with reserved
     // typed tags and this is fine and should get added to the peer cluster
     // table
     if (isSystemOrSuperUser()) {
       return true;
     }
     if (cell.getTagsLength() > 0) {
       Iterator<Tag> tagsItr = CellUtil.tagsIterator(cell.getTagsArray(), cell.getTagsOffset(),
           cell.getTagsLength());
       while (tagsItr.hasNext()) {
         if (RESERVED_VIS_TAG_TYPES.contains(tagsItr.next().getType())) {
           return false;
         }
       }
     }
     return true;
   }
 
   private void removeReplicationVisibilityTag(List<Tag> tags) throws IOException {
     Iterator<Tag> iterator = tags.iterator();
     while (iterator.hasNext()) {
       Tag tag = iterator.next();
       if (tag.getType() == TagType.STRING_VIS_TAG_TYPE) {
         iterator.remove();
         break;
       }
     }
   }
 
   @Override
   public RegionScanner preScannerOpen(ObserverContext<RegionCoprocessorEnvironment> e, Scan scan,
       RegionScanner s) throws IOException {
     if (!initialized) {
       throw new VisibilityControllerNotReadyException("VisibilityController not yet initialized!");
     }
     // Nothing to do if authorization is not enabled
     if (!authorizationEnabled) {
       return s;
     }
     Region region = e.getEnvironment().getRegion();
     Authorizations authorizations = null;
     try {
       authorizations = scan.getAuthorizations();
     } catch (DeserializationException de) {
       throw new IOException(de);
     }
     if (authorizations == null) {
       // No Authorizations present for this scan/Get!
       // In case of system tables other than "labels" just scan with out visibility check and
       // filtering. Checking visibility labels for META and NAMESPACE table is not needed.
       TableName table = region.getRegionInfo().getTable();
       if (table.isSystemTable() && !table.equals(LABELS_TABLE_NAME)) {
         return s;
       }
     }
 
     Filter visibilityLabelFilter = VisibilityUtils.createVisibilityLabelFilter(region,
         authorizations);
     if (visibilityLabelFilter != null) {
       Filter filter = scan.getFilter();
       if (filter != null) {
         scan.setFilter(new FilterList(filter, visibilityLabelFilter));
       } else {
         scan.setFilter(visibilityLabelFilter);
       }
     }
     return s;
   }
 
   @Override
   public DeleteTracker postInstantiateDeleteTracker(
       ObserverContext<RegionCoprocessorEnvironment> ctx, DeleteTracker delTracker)
       throws IOException {
     // Nothing to do if we are not filtering by visibility
     if (!authorizationEnabled) {
       return delTracker;
     }
     Region region = ctx.getEnvironment().getRegion();
     TableName table = region.getRegionInfo().getTable();
     if (table.isSystemTable()) {
       return delTracker;
     }
     // We are creating a new type of delete tracker here which is able to track
     // the timestamps and also the
     // visibility tags per cell. The covering cells are determined not only
     // based on the delete type and ts
     // but also on the visibility expression matching.
     return new VisibilityScanDeleteTracker();
   }
 
   @Override
   public RegionScanner postScannerOpen(final ObserverContext<RegionCoprocessorEnvironment> c,
       final Scan scan, final RegionScanner s) throws IOException {
     User user = VisibilityUtils.getActiveUser();
     if (user != null && user.getShortName() != null) {
       scannerOwners.put(s, user.getShortName());
     }
     return s;
   }
 
   @Override
   public boolean preScannerNext(final ObserverContext<RegionCoprocessorEnvironment> c,
       final InternalScanner s, final List<Result> result, final int limit, final boolean hasNext)
       throws IOException {
     requireScannerOwner(s);
     return hasNext;
   }
 
   @Override
   public void preScannerClose(final ObserverContext<RegionCoprocessorEnvironment> c,
       final InternalScanner s) throws IOException {
     requireScannerOwner(s);
   }
 
   @Override
   public void postScannerClose(final ObserverContext<RegionCoprocessorEnvironment> c,
       final InternalScanner s) throws IOException {
     // clean up any associated owner mapping
     scannerOwners.remove(s);
   }
 
   /**
    * Verify, when servicing an RPC, that the caller is the scanner owner. If so, we assume that
    * access control is correctly enforced based on the checks performed in preScannerOpen()
    */
   private void requireScannerOwner(InternalScanner s) throws AccessDeniedException {
     if (!RpcServer.isInRpcCallContext())
       return;
     String requestUName = RpcServer.getRequestUserName();
     String owner = scannerOwners.get(s);
     if (authorizationEnabled && owner != null && !owner.equals(requestUName)) {
       throw new AccessDeniedException("User '" + requestUName + "' is not the scanner owner!");
     }
   }
 
   @Override
   public void preGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get,
       List<Cell> results) throws IOException {
     if (!initialized) {
       throw new VisibilityControllerNotReadyException("VisibilityController not yet initialized");
     }
     // Nothing useful to do if authorization is not enabled
     if (!authorizationEnabled) {
       return;
     }
     Region region = e.getEnvironment().getRegion();
     Authorizations authorizations = null;
     try {
       authorizations = get.getAuthorizations();
     } catch (DeserializationException de) {
       throw new IOException(de);
     }
     if (authorizations == null) {
       // No Authorizations present for this scan/Get!
       // In case of system tables other than "labels" just scan with out visibility check and
       // filtering. Checking visibility labels for META and NAMESPACE table is not needed.
       TableName table = region.getRegionInfo().getTable();
       if (table.isSystemTable() && !table.equals(LABELS_TABLE_NAME)) {
         return;
       }
     }
     Filter visibilityLabelFilter = VisibilityUtils.createVisibilityLabelFilter(e.getEnvironment()
         .getRegion(), authorizations);
     if (visibilityLabelFilter != null) {
       Filter filter = get.getFilter();
       if (filter != null) {
         get.setFilter(new FilterList(filter, visibilityLabelFilter));
       } else {
         get.setFilter(visibilityLabelFilter);
       }
     }
   }
 
   private boolean isSystemOrSuperUser() throws IOException {
     return Superusers.isSuperUser(VisibilityUtils.getActiveUser());
   }
 
   @Override
   public Result preAppend(ObserverContext<RegionCoprocessorEnvironment> e, Append append)
       throws IOException {
     // If authorization is not enabled, we don't care about reserved tags
     if (!authorizationEnabled) {
       return null;
     }
     for (CellScanner cellScanner = append.cellScanner(); cellScanner.advance();) {
       if (!checkForReservedVisibilityTagPresence(cellScanner.current())) {
         throw new FailedSanityCheckException("Append contains cell with reserved type tag");
       }
     }
     return null;
   }
 
   @Override
   public Result preIncrement(ObserverContext<RegionCoprocessorEnvironment> e, Increment increment)
       throws IOException {
     // If authorization is not enabled, we don't care about reserved tags
     if (!authorizationEnabled) {
       return null;
     }
     for (CellScanner cellScanner = increment.cellScanner(); cellScanner.advance();) {
       if (!checkForReservedVisibilityTagPresence(cellScanner.current())) {
         throw new FailedSanityCheckException("Increment contains cell with reserved type tag");
       }
     }
     return null;
   }
 
   @Override
   public Cell postMutationBeforeWAL(ObserverContext<RegionCoprocessorEnvironment> ctx,
       MutationType opType, Mutation mutation, Cell oldCell, Cell newCell) throws IOException {
     List<Tag> tags = Lists.newArrayList();
     CellVisibility cellVisibility = null;
     try {
       cellVisibility = mutation.getCellVisibility();
     } catch (DeserializationException e) {
       throw new IOException(e);
     }
     if (cellVisibility == null) {
       return newCell;
     }
     // Prepend new visibility tags to a new list of tags for the cell
     // Don't check user auths for labels with Mutations when the user is super user
     boolean authCheck = authorizationEnabled && checkAuths && !(isSystemOrSuperUser());
     tags.addAll(this.visibilityLabelService.createVisibilityExpTags(cellVisibility.getExpression(),
         true, authCheck));
     // Save an object allocation where we can
     if (newCell.getTagsLength() > 0) {
       // Carry forward all other tags
       Iterator<Tag> tagsItr = CellUtil.tagsIterator(newCell.getTagsArray(),
           newCell.getTagsOffset(), newCell.getTagsLength());
       while (tagsItr.hasNext()) {
         Tag tag = tagsItr.next();
         if (tag.getType() != TagType.VISIBILITY_TAG_TYPE
             && tag.getType() != TagType.VISIBILITY_EXP_SERIALIZATION_FORMAT_TAG_TYPE) {
           tags.add(tag);
         }
       }
     }
 
     Cell rewriteCell = new TagRewriteCell(newCell, Tag.fromList(tags));
     return rewriteCell;
   }
 
   @Override
   public Service getService() {
     return VisibilityLabelsProtos.VisibilityLabelsService.newReflectiveService(this);
   }
 
   /****************************** VisibilityEndpoint service related methods ******************************/
   @Override
   public synchronized void addLabels(RpcController controller, VisibilityLabelsRequest request,
       RpcCallback<VisibilityLabelsResponse> done) {
     VisibilityLabelsResponse.Builder response = VisibilityLabelsResponse.newBuilder();
     List<VisibilityLabel> visLabels = request.getVisLabelList();
     if (!initialized) {
       setExceptionResults(visLabels.size(),
         new VisibilityControllerNotReadyException("VisibilityController not yet initialized!"),
         response);
     } else {
       List<byte[]> labels = new ArrayList<byte[]>(visLabels.size());
       try {
         if (authorizationEnabled) {
           checkCallingUserAuth();
         }
         RegionActionResult successResult = RegionActionResult.newBuilder().build();
         for (VisibilityLabel visLabel : visLabels) {
           byte[] label = visLabel.getLabel().toByteArray();
           labels.add(label);
           response.addResult(successResult); // Just mark as success. Later it will get reset
                                              // based on the result from
                                              // visibilityLabelService.addLabels ()
         }
         if (!labels.isEmpty()) {
           OperationStatus[] opStatus = this.visibilityLabelService.addLabels(labels);
           logResult(true, "addLabels", "Adding labels allowed", null, labels, null);
           int i = 0;
           for (OperationStatus status : opStatus) {
             while (response.getResult(i) != successResult)
               i++;
             if (status.getOperationStatusCode() != SUCCESS) {
               RegionActionResult.Builder failureResultBuilder = RegionActionResult.newBuilder();
               failureResultBuilder.setException(ResponseConverter
                   .buildException(new DoNotRetryIOException(status.getExceptionMsg())));
               response.setResult(i, failureResultBuilder.build());
             }
             i++;
           }
         }
       } catch (AccessDeniedException e) {
         logResult(false, "addLabels", e.getMessage(), null, labels, null);
         LOG.error("User is not having required permissions to add labels", e);
         setExceptionResults(visLabels.size(), e, response);
       } catch (IOException e) {
         LOG.error(e);
         setExceptionResults(visLabels.size(), e, response);
       }
     }
     done.run(response.build());
   }
 
   private void setExceptionResults(int size, IOException e,
       VisibilityLabelsResponse.Builder response) {
     RegionActionResult.Builder failureResultBuilder = RegionActionResult.newBuilder();
     failureResultBuilder.setException(ResponseConverter.buildException(e));
     RegionActionResult failureResult = failureResultBuilder.build();
     for (int i = 0; i < size; i++) {
       response.addResult(i, failureResult);
     }
   }
 
   @Override
   public synchronized void setAuths(RpcController controller, SetAuthsRequest request,
       RpcCallback<VisibilityLabelsResponse> done) {
     VisibilityLabelsResponse.Builder response = VisibilityLabelsResponse.newBuilder();
     List<ByteString> auths = request.getAuthList();
     if (!initialized) {
       setExceptionResults(auths.size(),
         new VisibilityControllerNotReadyException("VisibilityController not yet initialized!"),
         response);
     } else {
       byte[] user = request.getUser().toByteArray();
       List<byte[]> labelAuths = new ArrayList<byte[]>(auths.size());
       try {
         if (authorizationEnabled) {
           checkCallingUserAuth();
         }
         for (ByteString authBS : auths) {
           labelAuths.add(authBS.toByteArray());
         }
         OperationStatus[] opStatus = this.visibilityLabelService.setAuths(user, labelAuths);
         logResult(true, "setAuths", "Setting authorization for labels allowed", user, labelAuths,
           null);
         RegionActionResult successResult = RegionActionResult.newBuilder().build();
         for (OperationStatus status : opStatus) {
           if (status.getOperationStatusCode() == SUCCESS) {
             response.addResult(successResult);
           } else {
             RegionActionResult.Builder failureResultBuilder = RegionActionResult.newBuilder();
             failureResultBuilder.setException(ResponseConverter
                 .buildException(new DoNotRetryIOException(status.getExceptionMsg())));
             response.addResult(failureResultBuilder.build());
           }
         }
       } catch (AccessDeniedException e) {
         logResult(false, "setAuths", e.getMessage(), user, labelAuths, null);
         LOG.error("User is not having required permissions to set authorization", e);
         setExceptionResults(auths.size(), e, response);
       } catch (IOException e) {
         LOG.error(e);
         setExceptionResults(auths.size(), e, response);
       }
     }
     done.run(response.build());
   }
 
   private void logResult(boolean isAllowed, String request, String reason, byte[] user,
       List<byte[]> labelAuths, String regex) {
     if (AUDITLOG.isTraceEnabled()) {
       // This is more duplicated code!
       InetAddress remoteAddr = RpcServer.getRemoteAddress();
       List<String> labelAuthsStr = new ArrayList<>();
       if (labelAuths != null) {
         int labelAuthsSize = labelAuths.size();
         labelAuthsStr = new ArrayList<>(labelAuthsSize);
         for (int i = 0; i < labelAuthsSize; i++) {
           labelAuthsStr.add(Bytes.toString(labelAuths.get(i)));
         }
       }
 
       User requestingUser = null;
       try {
         requestingUser = VisibilityUtils.getActiveUser();
       } catch (IOException e) {
         LOG.warn("Failed to get active system user.");
         LOG.debug("Details on failure to get active system user.", e);
       }
       AUDITLOG.trace("Access " + (isAllowed ? "allowed" : "denied") + " for user "
           + (requestingUser != null ? requestingUser.getShortName() : "UNKNOWN") + "; reason: "
           + reason + "; remote address: " + (remoteAddr != null ? remoteAddr : "") + "; request: "
           + request + "; user: " + (user != null ? Bytes.toShort(user) : "null") + "; labels: "
           + labelAuthsStr + "; regex: " + regex);
     }
   }
 
   @Override
   public synchronized void getAuths(RpcController controller, GetAuthsRequest request,
       RpcCallback<GetAuthsResponse> done) {
     GetAuthsResponse.Builder response = GetAuthsResponse.newBuilder();
     if (!initialized) {
       controller.setFailed("VisibilityController not yet initialized");
     } else {
       byte[] user = request.getUser().toByteArray();
       List<String> labels = null;
       try {
         // We do ACL check here as we create scanner directly on region. It will not make calls to
         // AccessController CP methods.
         if (authorizationEnabled && accessControllerAvailable && !isSystemOrSuperUser()) {
           User requestingUser = VisibilityUtils.getActiveUser();
           throw new AccessDeniedException("User '"
               + (requestingUser != null ? requestingUser.getShortName() : "null")
               + "' is not authorized to perform this action.");
         }
         if (AuthUtil.isGroupPrincipal(Bytes.toString(user))) {
           // For backward compatibility. Previous custom visibilityLabelService
           // implementation may not have getGroupAuths
           try {
             this.visibilityLabelService.getClass().getDeclaredMethod("getGroupAuths",
                 new Class[] { String[].class, Boolean.TYPE });
           } catch (SecurityException e) {
             throw new AccessDeniedException("Failed to obtain getGroupAuths implementation");
           } catch (NoSuchMethodException e) {
             throw new AccessDeniedException(
                 "Get group auth is not supported in this implementation");
           }
           String group = AuthUtil.getGroupName(Bytes.toString(user));
           labels = this.visibilityLabelService.getGroupAuths(new String[] { group }, false);
         } else {
           labels = this.visibilityLabelService.getAuths(user, false);
         }
         logResult(true, "getAuths", "Get authorizations for user allowed", user, null, null);
       } catch (AccessDeniedException e) {
         logResult(false, "getAuths", e.getMessage(), user, null, null);
         ResponseConverter.setControllerException(controller, e);
       } catch (IOException e) {
         ResponseConverter.setControllerException(controller, e);
       }
       response.setUser(request.getUser());
       if (labels != null) {
         for (String label : labels) {
           response.addAuth(ByteStringer.wrap(Bytes.toBytes(label)));
         }
       }
     }
     done.run(response.build());
   }
 
   @Override
   public synchronized void clearAuths(RpcController controller, SetAuthsRequest request,
       RpcCallback<VisibilityLabelsResponse> done) {
     VisibilityLabelsResponse.Builder response = VisibilityLabelsResponse.newBuilder();
     List<ByteString> auths = request.getAuthList();
     if (!initialized) {
       setExceptionResults(auths.size(), new CoprocessorException(
           "VisibilityController not yet initialized"), response);
     } else {
       byte[] requestUser = request.getUser().toByteArray();
       List<byte[]> labelAuths = new ArrayList<byte[]>(auths.size());
       try {
         // When AC is ON, do AC based user auth check
         if (authorizationEnabled && accessControllerAvailable && !isSystemOrSuperUser()) {
           User user = VisibilityUtils.getActiveUser();
           throw new AccessDeniedException("User '" + (user != null ? user.getShortName() : "null")
               + " is not authorized to perform this action.");
         }
         if (authorizationEnabled) {
           checkCallingUserAuth(); // When AC is not in place the calling user should have
                                   // SYSTEM_LABEL auth to do this action.
         }
         for (ByteString authBS : auths) {
           labelAuths.add(authBS.toByteArray());
         }
 
         OperationStatus[] opStatus =
             this.visibilityLabelService.clearAuths(requestUser, labelAuths);
         logResult(true, "clearAuths", "Removing authorization for labels allowed", requestUser,
           labelAuths, null);
         RegionActionResult successResult = RegionActionResult.newBuilder().build();
         for (OperationStatus status : opStatus) {
           if (status.getOperationStatusCode() == SUCCESS) {
             response.addResult(successResult);
           } else {
             RegionActionResult.Builder failureResultBuilder = RegionActionResult.newBuilder();
             failureResultBuilder.setException(ResponseConverter
                 .buildException(new DoNotRetryIOException(status.getExceptionMsg())));
             response.addResult(failureResultBuilder.build());
           }
         }
       } catch (AccessDeniedException e) {
         logResult(false, "clearAuths", e.getMessage(), requestUser, labelAuths, null);
         LOG.error("User is not having required permissions to clear authorization", e);
         setExceptionResults(auths.size(), e, response);
       } catch (IOException e) {
         LOG.error(e);
         setExceptionResults(auths.size(), e, response);
       }
     }
     done.run(response.build());
   }
 
   @Override
   public synchronized void listLabels(RpcController controller, ListLabelsRequest request,
       RpcCallback<ListLabelsResponse> done) {
     ListLabelsResponse.Builder response = ListLabelsResponse.newBuilder();
     if (!initialized) {
       controller.setFailed("VisibilityController not yet initialized");
     } else {
       List<String> labels = null;
       String regex = request.hasRegex() ? request.getRegex() : null;
       try {
         // We do ACL check here as we create scanner directly on region. It will not make calls to
         // AccessController CP methods.
         if (authorizationEnabled && accessControllerAvailable && !isSystemOrSuperUser()) {
           User requestingUser = VisibilityUtils.getActiveUser();
           throw new AccessDeniedException("User '"
               + (requestingUser != null ? requestingUser.getShortName() : "null")
               + "' is not authorized to perform this action.");
         }
         labels = this.visibilityLabelService.listLabels(regex);
         logResult(false, "listLabels", "Listing labels allowed", null, null, regex);
       } catch (AccessDeniedException e) {
         logResult(false, "listLabels", e.getMessage(), null, null, regex);
         ResponseConverter.setControllerException(controller, e);
       } catch (IOException e) {
         ResponseConverter.setControllerException(controller, e);
       }
       if (labels != null && !labels.isEmpty()) {
         for (String label : labels) {
           response.addLabel(ByteStringer.wrap(Bytes.toBytes(label)));
         }
       }
     }
     done.run(response.build());
   }
 
   private void checkCallingUserAuth() throws IOException {
     if (!authorizationEnabled) { // Redundant, but just in case
       return;
     }
     if (!accessControllerAvailable) {
       User user = VisibilityUtils.getActiveUser();
       if (user == null) {
         throw new IOException("Unable to retrieve calling user");
       }
       boolean havingSystemAuth = false;
       try {
         this.visibilityLabelService.getClass().getDeclaredMethod("havingSystemAuth",
             new Class[] { User.class });
         havingSystemAuth = this.visibilityLabelService.havingSystemAuth(user);
       } catch (SecurityException e) {
         // Just consider this as AccessDeniedException
       } catch (NoSuchMethodException e) {
         // VLS not having havingSystemAuth(User) method. Go with deprecated havingSystemAuth(byte[])
         // method invoke
         havingSystemAuth = this.visibilityLabelService.havingSystemAuth(Bytes.toBytes(user
             .getShortName()));
       }
       if (!havingSystemAuth) {
         throw new AccessDeniedException("User '" + user.getShortName()
             + "' is not authorized to perform this action.");
       }
     }
   }
 
   private static class DeleteVersionVisibilityExpressionFilter extends FilterBase {
     private List<Tag> deleteCellVisTags;
     private Byte deleteCellVisTagsFormat;
 
     public DeleteVersionVisibilityExpressionFilter(List<Tag> deleteCellVisTags,
         Byte deleteCellVisTagsFormat) {
       this.deleteCellVisTags = deleteCellVisTags;
       this.deleteCellVisTagsFormat = deleteCellVisTagsFormat;
     }
 
     @Override
     public ReturnCode filterKeyValue(Cell cell) throws IOException {
       List<Tag> putVisTags = new ArrayList<Tag>();
       Byte putCellVisTagsFormat = VisibilityUtils.extractVisibilityTags(cell, putVisTags);
       boolean matchFound = VisibilityLabelServiceManager
           .getInstance().getVisibilityLabelService()
           .matchVisibility(putVisTags, putCellVisTagsFormat, deleteCellVisTags,
               deleteCellVisTagsFormat);
       return matchFound ? ReturnCode.INCLUDE : ReturnCode.SKIP;
     }
 
     // Override here explicitly as the method in super class FilterBase might do a KeyValue recreate.
     // See HBASE-12068
     @Override
     public Cell transformCell(Cell v) {
       return v;
     }
   }
 
   /**
    * A RegionServerObserver impl that provides the custom
    * VisibilityReplicationEndpoint. This class should be configured as the
    * 'hbase.coprocessor.regionserver.classes' for the visibility tags to be
    * replicated as string.  The value for the configuration should be
    * 'org.apache.hadoop.hbase.security.visibility.VisibilityController$VisibilityReplication'.
    */
   public static class VisibilityReplication extends BaseRegionServerObserver {
     private Configuration conf;
     private VisibilityLabelService visibilityLabelService;
 
     @Override
     public void start(CoprocessorEnvironment env) throws IOException {
       this.conf = env.getConfiguration();
       visibilityLabelService = VisibilityLabelServiceManager.getInstance()
           .getVisibilityLabelService(this.conf);
     }
 
     @Override
     public void stop(CoprocessorEnvironment env) throws IOException {
     }
 
     @Override
     public ReplicationEndpoint postCreateReplicationEndPoint(
         ObserverContext<RegionServerCoprocessorEnvironment> ctx, ReplicationEndpoint endpoint) {
       return new VisibilityReplicationEndpoint(endpoint, visibilityLabelService);
     }
   }
 }