001/**
002 *
003 * Copyright 2013-2020 Florian Schmaus
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.jivesoftware.smack.util.dns;
018
019import java.net.InetAddress;
020import java.net.UnknownHostException;
021import java.util.Arrays;
022import java.util.Collection;
023import java.util.List;
024import java.util.logging.Level;
025import java.util.logging.Logger;
026
027import org.jivesoftware.smack.ConnectionConfiguration.DnssecMode;
028import org.jivesoftware.smack.util.rce.RemoteConnectionEndpointLookupFailure;
029
030import org.minidns.dnsname.DnsName;
031import org.minidns.record.SRV;
032
033/**
034 * Implementations of this interface define a class that is capable of resolving DNS addresses.
035 *
036 */
037public abstract class DNSResolver {
038
039    protected static final Logger LOGGER = Logger.getLogger(DNSResolver.class.getName());
040
041    private final boolean supportsDnssec;
042
043    protected DNSResolver(boolean supportsDnssec) {
044        this.supportsDnssec = supportsDnssec;
045    }
046
047    /**
048     * Gets a list of service records for the specified service.
049     *
050     * @param name The symbolic name of the service.
051     * @param lookupFailures list of exceptions that occurred during lookup.
052     * @param dnssecMode security mode.
053     * @return The list of SRV records mapped to the service name.
054     */
055    public final Collection<SRV> lookupSrvRecords(DnsName name,
056                    List<RemoteConnectionEndpointLookupFailure> lookupFailures, DnssecMode dnssecMode) {
057        checkIfDnssecRequestedAndSupported(dnssecMode);
058        return lookupSrvRecords0(name, lookupFailures, dnssecMode);
059    }
060
061    protected abstract Collection<SRV> lookupSrvRecords0(DnsName name,
062                    List<RemoteConnectionEndpointLookupFailure> lookupFailures, DnssecMode dnssecMode);
063
064    public final List<InetAddress> lookupHostAddress(DnsName name,
065                    List<RemoteConnectionEndpointLookupFailure> lookupFailures, DnssecMode dnssecMode) {
066        checkIfDnssecRequestedAndSupported(dnssecMode);
067        return lookupHostAddress0(name, lookupFailures, dnssecMode);
068    }
069
070    /**
071     * Lookup the IP addresses of a given host name. Returns <code>null</code> if there was an error, in which the error
072     * reason will be added in form of a <code>HostAddress</code> to <code>failedAddresses</code>. Returns a empty list
073     * in case the DNS name exists but has no associated A or AAAA resource records. Otherwise, if the resolution was
074     * successful <em>and</em> there is at least one A or AAAA resource record, then a non-empty list will be returned.
075     * <p>
076     * Concrete DNS resolver implementations are free to overwrite this, but have to stick to the interface contract.
077     * </p>
078     *
079     * @param name the DNS name to lookup
080     * @param lookupFailures list of exceptions that occurred during lookup.
081     * @param dnssecMode the selected DNSSEC mode
082     * @return A list, either empty or non-empty, or <code>null</code>
083     */
084    protected List<InetAddress> lookupHostAddress0(DnsName name, List<RemoteConnectionEndpointLookupFailure> lookupFailures, DnssecMode dnssecMode) {
085        // Default implementation of a DNS name lookup for A/AAAA records. It is assumed that this method does never
086        // support DNSSEC. Subclasses are free to override this method.
087        if (dnssecMode != DnssecMode.disabled) {
088            throw new UnsupportedOperationException("This resolver does not support DNSSEC");
089        }
090
091        InetAddress[] inetAddressArray;
092        try {
093            inetAddressArray = InetAddress.getAllByName(name.toString());
094        } catch (UnknownHostException e) {
095            lookupFailures.add(new RemoteConnectionEndpointLookupFailure.DnsLookupFailure(name, e));
096            return null;
097        }
098
099        return Arrays.asList(inetAddressArray);
100    }
101
102    protected static boolean shouldContinue(CharSequence name, CharSequence hostname, List<InetAddress> hostAddresses) {
103        if (hostAddresses == null) {
104            return true;
105        }
106
107        // If hostAddresses is not null but empty, then the DNS resolution was successful but the domain did not
108        // have any A or AAAA resource records.
109        if (hostAddresses.isEmpty()) {
110            LOGGER.log(Level.INFO, "The DNS name " + name + ", points to a hostname (" + hostname
111                            + ") which has neither A or AAAA resource records. This is an indication of a broken DNS setup.");
112            return true;
113        }
114
115        return false;
116    }
117
118    private void checkIfDnssecRequestedAndSupported(DnssecMode dnssecMode) {
119        if (dnssecMode != DnssecMode.disabled && !supportsDnssec) {
120            throw new UnsupportedOperationException("This resolver does not support DNSSEC");
121        }
122    }
123}