org.apache.hadoop.hbase.security.access.PermissionStorage.java Source code

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/*
 * 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.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;

import org.apache.commons.lang3.StringUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.AuthUtil;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.Cell.Type;
import org.apache.hadoop.hbase.CellBuilderFactory;
import org.apache.hadoop.hbase.CellBuilderType;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.CompareOperator;
import org.apache.hadoop.hbase.NamespaceDescriptor;
import org.apache.hadoop.hbase.PrivateCellUtil;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.Tag;
import org.apache.hadoop.hbase.TagType;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.client.Delete;
import org.apache.hadoop.hbase.client.Get;
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.client.Table;
import org.apache.hadoop.hbase.client.TableDescriptor;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.filter.QualifierFilter;
import org.apache.hadoop.hbase.filter.RegexStringComparator;
import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.protobuf.generated.AccessControlProtos;
import org.apache.hadoop.hbase.regionserver.InternalScanner;
import org.apache.hadoop.hbase.regionserver.Region;
import org.apache.hadoop.hbase.security.User;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableFactories;
import org.apache.hadoop.io.WritableUtils;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.hbase.thirdparty.com.google.common.collect.ArrayListMultimap;
import org.apache.hbase.thirdparty.com.google.common.collect.ListMultimap;
import org.apache.hbase.thirdparty.com.google.common.collect.Lists;

/**
 * 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>
 * <p>
 * All values are encoded as byte arrays containing the codes from the
 * org.apache.hadoop.hbase.security.access.TablePermission.Action enum.
 * </p>
 */
@InterfaceAudience.Private
public final class PermissionStorage {
    /** Internal storage table for access control lists */
    public static final TableName ACL_TABLE_NAME = TableName.valueOf(NamespaceDescriptor.SYSTEM_NAMESPACE_NAME_STR,
            "acl");
    public static final byte[] ACL_GLOBAL_NAME = ACL_TABLE_NAME.getName();
    /** 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);
    /** KV tag to store per cell access control lists */
    public static final byte ACL_TAG_TYPE = TagType.ACL_TAG_TYPE;

    public static final char NAMESPACE_PREFIX = '@';

    /**
     * Delimiter to separate user, column family, and qualifier in
     * _acl_ table info: column keys */
    public static final char ACL_KEY_DELIMITER = ',';

    private static final Logger LOG = LoggerFactory.getLogger(PermissionStorage.class);

    private PermissionStorage() {
    }

    /**
     * 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
     * @param t acl table instance. It is closed upon method return.
     * @throws IOException in the case of an error accessing the metadata table
     */
    public static void addUserPermission(Configuration conf, UserPermission userPerm, Table t,
            boolean mergeExistingPermissions) throws IOException {
        Permission permission = userPerm.getPermission();
        Permission.Action[] actions = permission.getActions();
        byte[] rowKey = userPermissionRowKey(permission);
        Put p = new Put(rowKey);
        byte[] key = userPermissionKey(userPerm);

        if ((actions == null) || (actions.length == 0)) {
            String msg = "No actions associated with user '" + userPerm.getUser() + "'";
            LOG.warn(msg);
            throw new IOException(msg);
        }

        Set<Permission.Action> actionSet = new TreeSet<Permission.Action>();
        if (mergeExistingPermissions) {
            List<UserPermission> perms = getUserPermissions(conf, rowKey, null, null, null, false);
            UserPermission currentPerm = null;
            for (UserPermission perm : perms) {
                if (userPerm.equalsExceptActions(perm)) {
                    currentPerm = perm;
                    break;
                }
            }

            if (currentPerm != null && currentPerm.getPermission().getActions() != null) {
                actionSet.addAll(Arrays.asList(currentPerm.getPermission().getActions()));
            }
        }

        // merge current action with new action.
        actionSet.addAll(Arrays.asList(actions));

        // serialize to byte array.
        byte[] value = new byte[actionSet.size()];
        int index = 0;
        for (Permission.Action action : actionSet) {
            value[index++] = action.code();
        }
        p.add(CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY).setRow(p.getRow()).setFamily(ACL_LIST_FAMILY)
                .setQualifier(key).setTimestamp(p.getTimestamp()).setType(Type.Put).setValue(value).build());
        if (LOG.isDebugEnabled()) {
            LOG.debug("Writing permission with rowKey " + Bytes.toString(rowKey) + " " + Bytes.toString(key) + ": "
                    + Bytes.toStringBinary(value));
        }
        try {
            t.put(p);
        } finally {
            t.close();
        }
    }

    static void addUserPermission(Configuration conf, UserPermission userPerm, Table t) throws IOException {
        addUserPermission(conf, userPerm, t, false);
    }

    /**
     * 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
     * @param t acl table
     * @throws IOException if there is an error accessing the metadata table
     */
    public static void removeUserPermission(Configuration conf, UserPermission userPerm, Table t)
            throws IOException {
        if (null == userPerm.getPermission().getActions() || userPerm.getPermission().getActions().length == 0) {
            removePermissionRecord(conf, userPerm, t);
        } else {
            // Get all the global user permissions from the acl table
            List<UserPermission> permsList = getUserPermissions(conf,
                    userPermissionRowKey(userPerm.getPermission()), null, null, null, false);
            List<Permission.Action> remainingActions = new ArrayList<>();
            List<Permission.Action> dropActions = Arrays.asList(userPerm.getPermission().getActions());
            for (UserPermission perm : permsList) {
                // Find the user and remove only the requested permissions
                if (perm.getUser().equals(userPerm.getUser())) {
                    for (Permission.Action oldAction : perm.getPermission().getActions()) {
                        if (!dropActions.contains(oldAction)) {
                            remainingActions.add(oldAction);
                        }
                    }
                    if (!remainingActions.isEmpty()) {
                        perm.getPermission().setActions(
                                remainingActions.toArray(new Permission.Action[remainingActions.size()]));
                        addUserPermission(conf, perm, t);
                    } else {
                        removePermissionRecord(conf, userPerm, t);
                    }
                    break;
                }
            }
        }
        if (LOG.isDebugEnabled()) {
            LOG.debug("Removed permission " + userPerm.toString());
        }
    }

    private static void removePermissionRecord(Configuration conf, UserPermission userPerm, Table t)
            throws IOException {
        Delete d = new Delete(userPermissionRowKey(userPerm.getPermission()));
        d.addColumns(ACL_LIST_FAMILY, userPermissionKey(userPerm));
        try {
            t.delete(d);
        } finally {
            t.close();
        }
    }

    /**
     * Remove specified table from the _acl_ table.
     */
    static void removeTablePermissions(Configuration conf, TableName tableName, Table t) throws IOException {
        Delete d = new Delete(tableName.getName());

        if (LOG.isDebugEnabled()) {
            LOG.debug("Removing permissions of removed table " + tableName);
        }
        try {
            t.delete(d);
        } finally {
            t.close();
        }
    }

    /**
     * Remove specified namespace from the acl table.
     */
    static void removeNamespacePermissions(Configuration conf, String namespace, Table t) throws IOException {
        Delete d = new Delete(Bytes.toBytes(toNamespaceEntry(namespace)));

        if (LOG.isDebugEnabled()) {
            LOG.debug("Removing permissions of removed namespace " + namespace);
        }

        try {
            t.delete(d);
        } finally {
            t.close();
        }
    }

    static private void removeTablePermissions(TableName tableName, byte[] column, Table table, boolean closeTable)
            throws IOException {
        Scan scan = new Scan();
        scan.addFamily(ACL_LIST_FAMILY);

        String columnName = Bytes.toString(column);
        scan.setFilter(new QualifierFilter(CompareOperator.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<>(Bytes.BYTES_COMPARATOR);
        ResultScanner scanner = null;
        try {
            scanner = table.getScanner(scan);
            for (Result res : scanner) {
                for (byte[] q : res.getFamilyMap(ACL_LIST_FAMILY).navigableKeySet()) {
                    qualifierSet.add(q);
                }
            }

            if (qualifierSet.size() > 0) {
                Delete d = new Delete(tableName.getName());
                for (byte[] qualifier : qualifierSet) {
                    d.addColumns(ACL_LIST_FAMILY, qualifier);
                }
                table.delete(d);
            }
        } finally {
            if (scanner != null) {
                scanner.close();
            }
            if (closeTable) {
                table.close();
            }
        }
    }

    /**
     * Remove specified table column from the acl table.
     */
    static void removeTablePermissions(Configuration conf, TableName tableName, byte[] column, Table t)
            throws IOException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Removing permissions of removed column " + Bytes.toString(column) + " from table "
                    + tableName);
        }
        removeTablePermissions(tableName, column, t, true);
    }

    static byte[] userPermissionRowKey(Permission permission) {
        byte[] row;
        if (permission instanceof TablePermission) {
            TablePermission tablePerm = (TablePermission) permission;
            row = tablePerm.getTableName().getName();
        } else if (permission instanceof NamespacePermission) {
            NamespacePermission nsPerm = (NamespacePermission) permission;
            row = Bytes.toBytes(toNamespaceEntry(nsPerm.getNamespace()));
        } else {
            // permission instanceof TablePermission
            row = ACL_GLOBAL_NAME;
        }
        return row;
    }

    /**
     * Build qualifier key from user permission:
     *  username
     *  username,family
     *  username,family,qualifier
     */
    static byte[] userPermissionKey(UserPermission permission) {
        byte[] key = Bytes.toBytes(permission.getUser());
        byte[] qualifier = null;
        byte[] family = null;
        if (permission.getPermission().getAccessScope() == Permission.Scope.TABLE) {
            TablePermission tablePermission = (TablePermission) permission.getPermission();
            family = tablePermission.getFamily();
            qualifier = tablePermission.getQualifier();
        }

        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(Region region) {
        return ACL_TABLE_NAME.equals(region.getTableDescriptor().getTableName());
    }

    /**
     * Returns {@code true} if the given table is {@code _acl_} metadata table.
     */
    static boolean isAclTable(TableDescriptor desc) {
        return ACL_TABLE_NAME.equals(desc.getTableName());
    }

    /**
     * Loads all of the permission grants stored in a region of the {@code _acl_}
     * table.
     *
     * @param aclRegion the acl region
     * @return a map of the permissions for this table.
     * @throws IOException if an error occurs
     */
    static Map<byte[], ListMultimap<String, UserPermission>> loadAll(Region aclRegion) throws IOException {
        if (!isAclRegion(aclRegion)) {
            throw new IOException("Can only load permissions from " + ACL_TABLE_NAME);
        }

        Map<byte[], ListMultimap<String, UserPermission>> allPerms = new TreeMap<>(Bytes.BYTES_RAWCOMPARATOR);

        // 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<Cell> row = new ArrayList<>();

                boolean hasNext = iScanner.next(row);
                ListMultimap<String, UserPermission> perms = ArrayListMultimap.create();
                byte[] entry = null;
                for (Cell kv : row) {
                    if (entry == null) {
                        entry = CellUtil.cloneRow(kv);
                    }
                    Pair<String, Permission> permissionsOfUserOnTable = parsePermissionRecord(entry, kv, null, null,
                            false, null);
                    if (permissionsOfUserOnTable != null) {
                        String username = permissionsOfUserOnTable.getFirst();
                        Permission permission = permissionsOfUserOnTable.getSecond();
                        perms.put(username, new UserPermission(username, permission));
                    }
                }
                if (entry != null) {
                    allPerms.put(entry, 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, UserPermission>> loadAll(Configuration conf) throws IOException {
        Map<byte[], ListMultimap<String, UserPermission>> allPerms = new TreeMap<>(Bytes.BYTES_RAWCOMPARATOR);

        // do a full scan of _acl_, filtering on only first table region rows

        Scan scan = new Scan();
        scan.addFamily(ACL_LIST_FAMILY);

        ResultScanner scanner = null;
        // TODO: Pass in a Connection rather than create one each time.
        try (Connection connection = ConnectionFactory.createConnection(conf)) {
            try (Table table = connection.getTable(ACL_TABLE_NAME)) {
                scanner = table.getScanner(scan);
                try {
                    for (Result row : scanner) {
                        ListMultimap<String, UserPermission> resultPerms = parsePermissions(row.getRow(), row, null,
                                null, null, false);
                        allPerms.put(row.getRow(), resultPerms);
                    }
                } finally {
                    if (scanner != null) {
                        scanner.close();
                    }
                }
            }
        }

        return allPerms;
    }

    public static ListMultimap<String, UserPermission> getTablePermissions(Configuration conf, TableName tableName)
            throws IOException {
        return getPermissions(conf, tableName != null ? tableName.getName() : null, null, null, null, null, false);
    }

    @VisibleForTesting
    public static ListMultimap<String, UserPermission> getNamespacePermissions(Configuration conf, String namespace)
            throws IOException {
        return getPermissions(conf, Bytes.toBytes(toNamespaceEntry(namespace)), null, null, null, null, false);
    }

    /**
     * Reads user permission assignments stored in the <code>l:</code> column family of the first
     * table row in <code>_acl_</code>.
     * <p>
     * See {@link PermissionStorage class documentation} for the key structure used for storage.
     * </p>
     */
    static ListMultimap<String, UserPermission> getPermissions(Configuration conf, byte[] entryName, Table t,
            byte[] cf, byte[] cq, String user, boolean hasFilterUser) throws IOException {
        if (entryName == null) {
            entryName = ACL_GLOBAL_NAME;
        }
        // for normal user tables, we just read the table row from _acl_
        ListMultimap<String, UserPermission> perms = ArrayListMultimap.create();
        Get get = new Get(entryName);
        get.addFamily(ACL_LIST_FAMILY);
        Result row = null;
        if (t == null) {
            try (Connection connection = ConnectionFactory.createConnection(conf)) {
                try (Table table = connection.getTable(ACL_TABLE_NAME)) {
                    row = table.get(get);
                }
            }
        } else {
            row = t.get(get);
        }
        if (!row.isEmpty()) {
            perms = parsePermissions(entryName, row, cf, cq, user, hasFilterUser);
        } else {
            LOG.info("No permissions found in " + ACL_TABLE_NAME + " for acl entry " + Bytes.toString(entryName));
        }

        return perms;
    }

    /**
     * Returns the currently granted permissions for a given table as the specified user plus
     * associated permissions.
     */
    public static List<UserPermission> getUserTablePermissions(Configuration conf, TableName tableName, byte[] cf,
            byte[] cq, String userName, boolean hasFilterUser) throws IOException {
        return getUserPermissions(conf, tableName == null ? null : tableName.getName(), cf, cq, userName,
                hasFilterUser);
    }

    /**
     * Returns the currently granted permissions for a given namespace as the specified user plus
     * associated permissions.
     */
    public static List<UserPermission> getUserNamespacePermissions(Configuration conf, String namespace,
            String user, boolean hasFilterUser) throws IOException {
        return getUserPermissions(conf, Bytes.toBytes(toNamespaceEntry(namespace)), null, null, user,
                hasFilterUser);
    }

    /**
     * Returns the currently granted permissions for a given table/namespace with associated
     * permissions based on the specified column family, column qualifier and user name.
     * @param conf the configuration
     * @param entryName Table name or the namespace
     * @param cf Column family
     * @param cq Column qualifier
     * @param user User name to be filtered from permission as requested
     * @param hasFilterUser true if filter user is provided, otherwise false.
     * @return List of UserPermissions
     * @throws IOException on failure
     */
    public static List<UserPermission> getUserPermissions(Configuration conf, byte[] entryName, byte[] cf,
            byte[] cq, String user, boolean hasFilterUser) throws IOException {
        ListMultimap<String, UserPermission> allPerms = getPermissions(conf, entryName, null, cf, cq, user,
                hasFilterUser);
        List<UserPermission> perms = new ArrayList<>();
        for (Map.Entry<String, UserPermission> entry : allPerms.entries()) {
            perms.add(entry.getValue());
        }
        return perms;
    }

    /**
     * Parse and filter permission based on the specified column family, column qualifier and user
     * name.
     */
    private static ListMultimap<String, UserPermission> parsePermissions(byte[] entryName, Result result, byte[] cf,
            byte[] cq, String user, boolean hasFilterUser) {
        ListMultimap<String, UserPermission> perms = ArrayListMultimap.create();
        if (result != null && result.size() > 0) {
            for (Cell kv : result.rawCells()) {
                Pair<String, Permission> permissionsOfUserOnTable = parsePermissionRecord(entryName, kv, cf, cq,
                        hasFilterUser, user);

                if (permissionsOfUserOnTable != null) {
                    String username = permissionsOfUserOnTable.getFirst();
                    Permission permission = permissionsOfUserOnTable.getSecond();
                    perms.put(username, new UserPermission(username, permission));
                }
            }
        }
        return perms;
    }

    private static Pair<String, Permission> parsePermissionRecord(byte[] entryName, Cell kv, byte[] cf, byte[] cq,
            boolean filterPerms, String filterUser) {
        // return X given a set of permissions encoded in the permissionRecord kv.
        byte[] family = CellUtil.cloneFamily(kv);
        if (!Bytes.equals(family, ACL_LIST_FAMILY)) {
            return null;
        }

        byte[] key = CellUtil.cloneQualifier(kv);
        byte[] value = CellUtil.cloneValue(kv);
        if (LOG.isDebugEnabled()) {
            LOG.debug("Read acl: entry[" + Bytes.toStringBinary(entryName) + "], 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);

        // Retrieve group list for the filterUser if cell key is a group.
        // Group list is not required when filterUser itself a group
        List<String> filterUserGroups = null;
        if (filterPerms) {
            if (username.charAt(0) == '@' && !StringUtils.isEmpty(filterUser) && filterUser.charAt(0) != '@') {
                filterUserGroups = AccessChecker.getUserGroups(filterUser);
            }
        }

        // Handle namespace entry
        if (isNamespaceEntry(entryName)) {
            // Filter the permissions cell record if client query
            if (filterPerms && !validateFilterUser(username, filterUser, filterUserGroups)) {
                return null;
            }

            return new Pair<>(username, Permission.newBuilder(Bytes.toString(fromNamespaceEntry(entryName)))
                    .withActionCodes(value).build());
        }

        // Handle global entry
        if (isGlobalEntry(entryName)) {
            // Filter the permissions cell record if client query
            if (filterPerms && !validateFilterUser(username, filterUser, filterUserGroups)) {
                return null;
            }

            return new Pair<>(username, Permission.newBuilder().withActionCodes(value).build());
        }

        // Handle table entry
        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);
            }
        }

        // Filter the permissions cell record if client query
        if (filterPerms) {
            // ACL table contain 3 types of cell key entries; hbase:Acl, namespace and table. So to filter
            // the permission cell records additional validations are required at CF, CQ and username.
            // Here we can proceed based on client input whether it contain filterUser.
            // Validate the filterUser when specified
            if (filterUser != null && !validateFilterUser(username, filterUser, filterUserGroups)) {
                return null;
            }
            if (!validateCFAndCQ(permFamily, cf, permQualifier, cq)) {
                return null;
            }
        }

        return new Pair<>(username, Permission.newBuilder(TableName.valueOf(entryName)).withFamily(permFamily)
                .withQualifier(permQualifier).withActionCodes(value).build());
    }

    /*
     * Validate the cell key with the client filterUser if specified in the query input. 1. If cell
     * key (username) is not a group then check whether client filterUser is equal to username 2. If
     * cell key (username) is a group then check whether client filterUser belongs to the cell key
     * group (username) 3. In case when both filterUser and username are group names then cell will be
     * filtered if not equal.
     */
    private static boolean validateFilterUser(String username, String filterUser, List<String> filterUserGroups) {
        if (filterUserGroups == null) {
            // Validate user name or group names whether equal
            if (filterUser.equals(username)) {
                return true;
            }
        } else {
            // Check whether filter user belongs to the cell key group.
            return filterUserGroups.contains(username.substring(1));
        }
        return false;
    }

    /*
     * Validate the cell with client CF and CQ if specified in the query input. 1. If CF is NULL, then
     * no need of further validation, result should include all CF and CQ. 2. IF CF specified and
     * equal then validation required at CQ level if CF specified in client input, otherwise return
     * all CQ records.
     */
    private static boolean validateCFAndCQ(byte[] permFamily, byte[] cf, byte[] permQualifier, byte[] cq) {
        boolean include = true;
        if (cf != null) {
            if (Bytes.equals(cf, permFamily)) {
                if (cq != null && !Bytes.equals(cq, permQualifier)) {
                    // if CQ specified and didn't match then ignore this cell
                    include = false;
                }
            } else {
                // if CF specified and didn't match then ignore this cell
                include = false;
            }
        }
        return include;
    }

    /**
     * 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, UserPermission> perms, Configuration conf) {
        return ProtobufUtil.prependPBMagic(AccessControlUtil.toUserTablePermissions(perms).toByteArray());
    }

    // This is part of the old HbaseObjectWritableFor96Migration.
    private static final int LIST_CODE = 61;

    private static final int WRITABLE_CODE = 14;

    private static final int WRITABLE_NOT_ENCODED = 0;

    private static List<Permission> readWritableUserPermission(DataInput in, Configuration conf)
            throws IOException, ClassNotFoundException {
        assert WritableUtils.readVInt(in) == LIST_CODE;
        int length = in.readInt();
        List<Permission> list = new ArrayList<>(length);
        for (int i = 0; i < length; i++) {
            assert WritableUtils.readVInt(in) == WRITABLE_CODE;
            assert WritableUtils.readVInt(in) == WRITABLE_NOT_ENCODED;
            String className = Text.readString(in);
            Class<? extends Writable> clazz = conf.getClassByName(className).asSubclass(Writable.class);
            Writable instance = WritableFactories.newInstance(clazz, conf);
            instance.readFields(in);
            list.add((Permission) instance);
        }
        return list;
    }

    @VisibleForTesting
    public static ListMultimap<String, UserPermission> readUserPermission(byte[] data, Configuration conf)
            throws DeserializationException {
        if (ProtobufUtil.isPBMagicPrefix(data)) {
            int pblen = ProtobufUtil.lengthOfPBMagic();
            try {
                AccessControlProtos.UsersAndPermissions.Builder builder = AccessControlProtos.UsersAndPermissions
                        .newBuilder();
                ProtobufUtil.mergeFrom(builder, data, pblen, data.length - pblen);
                return AccessControlUtil.toUserPermission(builder.build());
            } catch (IOException e) {
                throw new DeserializationException(e);
            }
        } else {
            // TODO: We have to re-write non-PB data as PB encoded. Otherwise we will carry old Writables
            // forever (here and a couple of other places).
            ListMultimap<String, UserPermission> userPermission = 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<Permission> perms = readWritableUserPermission(in, conf);
                    for (Permission p : perms) {
                        userPermission.put(user, new UserPermission(user, p));
                    }
                }
            } catch (IOException | ClassNotFoundException e) {
                throw new DeserializationException(e);
            }
            return userPermission;
        }
    }

    public static ListMultimap<String, Permission> readPermissions(byte[] data, Configuration conf)
            throws DeserializationException {
        if (ProtobufUtil.isPBMagicPrefix(data)) {
            int pblen = ProtobufUtil.lengthOfPBMagic();
            try {
                AccessControlProtos.UsersAndPermissions.Builder builder = AccessControlProtos.UsersAndPermissions
                        .newBuilder();
                ProtobufUtil.mergeFrom(builder, data, pblen, data.length - pblen);
                return AccessControlUtil.toPermission(builder.build());
            } catch (IOException e) {
                throw new DeserializationException(e);
            }
        } else {
            // TODO: We have to re-write non-PB data as PB encoded. Otherwise we will carry old Writables
            // forever (here and a couple of other places).
            ListMultimap<String, Permission> 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);
                    perms.putAll(user, readWritableUserPermission(in, conf));
                }
            } catch (IOException | ClassNotFoundException e) {
                throw new DeserializationException(e);
            }
            return perms;
        }
    }

    public static boolean isGlobalEntry(byte[] entryName) {
        return entryName != null && TableName.valueOf(entryName).equals(ACL_TABLE_NAME);
    }

    public static boolean isNamespaceEntry(String entryName) {
        return entryName != null && entryName.charAt(0) == NAMESPACE_PREFIX;
    }

    public static boolean isNamespaceEntry(byte[] entryName) {
        return entryName != null && entryName.length != 0 && entryName[0] == NAMESPACE_PREFIX;
    }

    public static String toNamespaceEntry(String namespace) {
        return NAMESPACE_PREFIX + namespace;
    }

    public static String fromNamespaceEntry(String namespace) {
        if (namespace.charAt(0) != NAMESPACE_PREFIX) {
            throw new IllegalArgumentException("Argument is not a valid namespace entry");
        }
        return namespace.substring(1);
    }

    public static byte[] toNamespaceEntry(byte[] namespace) {
        byte[] ret = new byte[namespace.length + 1];
        ret[0] = NAMESPACE_PREFIX;
        System.arraycopy(namespace, 0, ret, 1, namespace.length);
        return ret;
    }

    public static byte[] fromNamespaceEntry(byte[] namespace) {
        if (namespace[0] != NAMESPACE_PREFIX) {
            throw new IllegalArgumentException(
                    "Argument is not a valid namespace entry: " + Bytes.toString(namespace));
        }
        return Arrays.copyOfRange(namespace, 1, namespace.length);
    }

    public static List<Permission> getCellPermissionsForUser(User user, Cell cell) throws IOException {
        // Save an object allocation where we can
        if (cell.getTagsLength() == 0) {
            return null;
        }
        List<Permission> results = Lists.newArrayList();
        Iterator<Tag> tagsIterator = PrivateCellUtil.tagsIterator(cell);
        while (tagsIterator.hasNext()) {
            Tag tag = tagsIterator.next();
            if (tag.getType() == ACL_TAG_TYPE) {
                // Deserialize the table permissions from the KV
                // TODO: This can be improved. Don't build UsersAndPermissions just to unpack it again,
                // use the builder
                AccessControlProtos.UsersAndPermissions.Builder builder = AccessControlProtos.UsersAndPermissions
                        .newBuilder();
                if (tag.hasArray()) {
                    ProtobufUtil.mergeFrom(builder, tag.getValueArray(), tag.getValueOffset(),
                            tag.getValueLength());
                } else {
                    ProtobufUtil.mergeFrom(builder, Tag.cloneValue(tag));
                }
                ListMultimap<String, Permission> kvPerms = AccessControlUtil.toUsersAndPermissions(builder.build());
                // Are there permissions for this user?
                List<Permission> userPerms = kvPerms.get(user.getShortName());
                if (userPerms != null) {
                    results.addAll(userPerms);
                }
                // Are there permissions for any of the groups this user belongs to?
                String[] groupNames = user.getGroupNames();
                if (groupNames != null) {
                    for (String group : groupNames) {
                        List<Permission> groupPerms = kvPerms.get(AuthUtil.toGroupEntry(group));
                        if (results != null) {
                            results.addAll(groupPerms);
                        }
                    }
                }
            }
        }
        return results;
    }
}