1 files changed, 103 insertions, 0 deletions
diff --git a/src/main/java/eu/siacs/conversations/utils/DNSHelper.java b/src/main/java/eu/siacs/conversations/utils/DNSHelper.java
new file mode 100644
index 00000000..79a8c854
--- /dev/null
+++ b/src/main/java/eu/siacs/conversations/utils/DNSHelper.java
@@ -0,0 +1,103 @@
+package eu.siacs.conversations.utils;
+
+import de.measite.minidns.Client;
+import de.measite.minidns.DNSMessage;
+import de.measite.minidns.Record;
+import de.measite.minidns.Record.TYPE;
+import de.measite.minidns.Record.CLASS;
+import de.measite.minidns.record.SRV;
+import de.measite.minidns.record.Data;
+import de.measite.minidns.util.NameUtil;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.util.TreeSet;
+import java.util.regex.Pattern;
+
+import de.thedevstack.android.logcat.Logging;
+import de.thedevstack.conversationsplus.dto.SrvRecord;
+
+import eu.siacs.conversations.Config;
+import eu.siacs.conversations.xmpp.jid.Jid;
+
+public class DNSHelper {
+    private static final String CLIENT_SRV_PREFIX = "_xmpp-client._tcp.";
+    private static final Pattern PATTERN_IPV4 = Pattern.compile("\\A(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
+    private static final Pattern PATTERN_IPV6_HEX4DECCOMPRESSED = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?) ::((?:[0-9A-Fa-f]{1,4}:)*)(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
+    private static final Pattern PATTERN_IPV6_6HEX4DEC = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}:){6,6})(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
+    private static final Pattern PATTERN_IPV6_HEXCOMPRESSED = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)::((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)\\z");
+    private static final Pattern PATTERN_IPV6 = Pattern.compile("\\A(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}\\z");
+
+	protected static Client client = new Client();
+
+    /**
+     * Queries the SRV record for the server JID.
+     * This method uses all available Domain Name Servers.
+     * @param jid the server JID
+     * @return TreeSet with SrvRecords. If no SRV record is found for JID an empty TreeSet is returned.
+     */
+    public static final TreeSet<SrvRecord> querySrvRecord(Jid jid) {
+        String host = jid.getDomainpart();
+        String dns[] = client.findDNS();
+        TreeSet<SrvRecord> result = new TreeSet<>();
+
+        if (dns != null) {
+            for (String dnsserver : dns) {
+                result = querySrvRecord(host, dnsserver);
+                if (!result.isEmpty()) {
+                    break;
+                }
+            }
+        }
+
+        return result;
+    }
+
+    /**
+     * Queries the SRV record for an host from the given Domain Name Server.
+     * @param host the host to query for
+     * @param dnsserver the DNS to query on
+     * @return TreeSet with SrvRecords.
+     */
+    private static final TreeSet<SrvRecord> querySrvRecord(String host, String dnsserver) {
+        TreeSet<SrvRecord> result = new TreeSet<>();
+        try {
+            InetAddress dnsServerAddress = InetAddress.getByName(dnsserver);
+            String qname = CLIENT_SRV_PREFIX + host;
+            DNSMessage message = client.query(qname, TYPE.SRV, CLASS.IN, dnsServerAddress.getHostAddress());
+            Record[] rrset = message.getAnswers();
+            for (Record rr : rrset) {
+                Data d = rr.getPayload();
+                if (d instanceof SRV && NameUtil.idnEquals(qname, rr.getName())) {
+                    SRV srv = (SRV) d;
+                    SrvRecord srvRecord = new SrvRecord(srv.getPriority(), srv.getName(), srv.getPort());
+                    result.add(srvRecord);
+                }
+            }
+        } catch (IOException e) {
+            Logging.d("dns", "Error while retrieving SRV record for '" + host + "' from DNS '" + dnsserver + "': " + e.getMessage());
+        }
+        return result;
+    }
+
+    /**
+     * Checks whether the given server is an IP address or not.
+     * The following patterns are treated as valid IP addresses:
+     * <ul>
+     *     <li>{@link #PATTERN_IPV4}</li>
+     *     <li>{@link #PATTERN_IPV6}</li>
+     *     <li>{@link #PATTERN_IPV6_6HEX4DEC}</li>
+     *     <li>{@link #PATTERN_IPV6_HEX4DECCOMPRESSED}</li>
+     *     <li>{@link #PATTERN_IPV6_HEXCOMPRESSED}</li>
+     * </ul>
+     * @param server the string to check
+     * @return <code>true</code> if one of the patterns is matched <code>false</code> otherwise
+     */
+	public static boolean isIp(final String server) {
+		return PATTERN_IPV4.matcher(server).matches()
+				|| PATTERN_IPV6.matcher(server).matches()
+				|| PATTERN_IPV6_6HEX4DEC.matcher(server).matches()
+				|| PATTERN_IPV6_HEX4DECCOMPRESSED.matcher(server).matches()
+				|| PATTERN_IPV6_HEXCOMPRESSED.matcher(server).matches();
+	}
+}