Java example source code file (KdcComm.java)
The KdcComm.java Java example source code
/*
* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/*
*
* (C) Copyright IBM Corp. 1999 All Rights Reserved.
* Copyright 1997 The Open Group Research Institute. All rights reserved.
*/
package sun.security.krb5;
import java.security.PrivilegedAction;
import java.security.Security;
import java.util.Locale;
import sun.security.krb5.internal.Krb5;
import sun.security.krb5.internal.NetClient;
import java.io.IOException;
import java.net.SocketTimeoutException;
import java.util.StringTokenizer;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import java.security.PrivilegedActionException;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.HashSet;
import java.util.Iterator;
import sun.security.krb5.internal.KRBError;
/**
* KDC-REQ/KDC-REP communication. No more base class for KrbAsReq and
* KrbTgsReq. This class is now communication only.
*/
public final class KdcComm {
// The following settings can be configured in [libdefaults]
// section of krb5.conf, which are global for all realms. Each of
// them can also be defined in a realm, which overrides value here.
/**
* max retry time for a single KDC, default Krb5.KDC_RETRY_LIMIT (3)
*/
private static int defaultKdcRetryLimit;
/**
* timeout requesting a ticket from KDC, in millisec, default 30 sec
*/
private static int defaultKdcTimeout;
/**
* max UDP packet size, default unlimited (-1)
*/
private static int defaultUdpPrefLimit;
private static final boolean DEBUG = Krb5.DEBUG;
private static final String BAD_POLICY_KEY = "krb5.kdc.bad.policy";
/**
* What to do when a KDC is unavailable, specified in the
* java.security file with key krb5.kdc.bad.policy.
* Possible values can be TRY_LAST or TRY_LESS. Reloaded when refreshed.
*/
private enum BpType {
NONE, TRY_LAST, TRY_LESS
}
private static int tryLessMaxRetries = 1;
private static int tryLessTimeout = 5000;
private static BpType badPolicy;
static {
initStatic();
}
/**
* Read global settings
*/
public static void initStatic() {
String value = AccessController.doPrivileged(
new PrivilegedAction<String>() {
public String run() {
return Security.getProperty(BAD_POLICY_KEY);
}
});
if (value != null) {
value = value.toLowerCase(Locale.ENGLISH);
String[] ss = value.split(":");
if ("tryless".equals(ss[0])) {
if (ss.length > 1) {
String[] params = ss[1].split(",");
try {
int tmp0 = Integer.parseInt(params[0]);
if (params.length > 1) {
tryLessTimeout = Integer.parseInt(params[1]);
}
// Assign here in case of exception at params[1]
tryLessMaxRetries = tmp0;
} catch (NumberFormatException nfe) {
// Ignored. Please note that tryLess is recognized and
// used, parameters using default values
if (DEBUG) {
System.out.println("Invalid " + BAD_POLICY_KEY +
" parameter for tryLess: " +
value + ", use default");
}
}
}
badPolicy = BpType.TRY_LESS;
} else if ("trylast".equals(ss[0])) {
badPolicy = BpType.TRY_LAST;
} else {
badPolicy = BpType.NONE;
}
} else {
badPolicy = BpType.NONE;
}
int timeout = -1;
int max_retries = -1;
int udp_pref_limit = -1;
try {
Config cfg = Config.getInstance();
String temp = cfg.get("libdefaults", "kdc_timeout");
timeout = parsePositiveIntString(temp);
temp = cfg.get("libdefaults", "max_retries");
max_retries = parsePositiveIntString(temp);
temp = cfg.get("libdefaults", "udp_preference_limit");
udp_pref_limit = parsePositiveIntString(temp);
} catch (Exception exc) {
// ignore any exceptions; use default values
if (DEBUG) {
System.out.println ("Exception in getting KDC communication " +
"settings, using default value " +
exc.getMessage());
}
}
defaultKdcTimeout = timeout > 0 ? timeout : 30*1000; // 30 seconds
defaultKdcRetryLimit =
max_retries > 0 ? max_retries : Krb5.KDC_RETRY_LIMIT;
if (udp_pref_limit < 0) {
defaultUdpPrefLimit = Krb5.KDC_DEFAULT_UDP_PREF_LIMIT;
} else if (udp_pref_limit > Krb5.KDC_HARD_UDP_LIMIT) {
defaultUdpPrefLimit = Krb5.KDC_HARD_UDP_LIMIT;
} else {
defaultUdpPrefLimit = udp_pref_limit;
}
KdcAccessibility.reset();
}
/**
* The instance fields
*/
private String realm;
public KdcComm(String realm) throws KrbException {
if (realm == null) {
realm = Config.getInstance().getDefaultRealm();
if (realm == null) {
throw new KrbException(Krb5.KRB_ERR_GENERIC,
"Cannot find default realm");
}
}
this.realm = realm;
}
public byte[] send(byte[] obuf)
throws IOException, KrbException {
int udpPrefLimit = getRealmSpecificValue(
realm, "udp_preference_limit", defaultUdpPrefLimit);
boolean useTCP = (udpPrefLimit > 0 &&
(obuf != null && obuf.length > udpPrefLimit));
return send(obuf, useTCP);
}
private byte[] send(byte[] obuf, boolean useTCP)
throws IOException, KrbException {
if (obuf == null)
return null;
Config cfg = Config.getInstance();
if (realm == null) {
realm = cfg.getDefaultRealm();
if (realm == null) {
throw new KrbException(Krb5.KRB_ERR_GENERIC,
"Cannot find default realm");
}
}
String kdcList = cfg.getKDCList(realm);
if (kdcList == null) {
throw new KrbException("Cannot get kdc for realm " + realm);
}
// tempKdc may include the port number also
Iterator<String> tempKdc = KdcAccessibility.list(kdcList).iterator();
if (!tempKdc.hasNext()) {
throw new KrbException("Cannot get kdc for realm " + realm);
}
byte[] ibuf = null;
try {
ibuf = sendIfPossible(obuf, tempKdc.next(), useTCP);
} catch(Exception first) {
boolean ok = false;
while(tempKdc.hasNext()) {
try {
ibuf = sendIfPossible(obuf, tempKdc.next(), useTCP);
ok = true;
break;
} catch(Exception ignore) {}
}
if (!ok) throw first;
}
if (ibuf == null) {
throw new IOException("Cannot get a KDC reply");
}
return ibuf;
}
// send the AS Request to the specified KDC
// failover to using TCP if useTCP is not set and response is too big
private byte[] sendIfPossible(byte[] obuf, String tempKdc, boolean useTCP)
throws IOException, KrbException {
try {
byte[] ibuf = send(obuf, tempKdc, useTCP);
KRBError ke = null;
try {
ke = new KRBError(ibuf);
} catch (Exception e) {
// OK
}
if (ke != null && ke.getErrorCode() ==
Krb5.KRB_ERR_RESPONSE_TOO_BIG) {
ibuf = send(obuf, tempKdc, true);
}
KdcAccessibility.removeBad(tempKdc);
return ibuf;
} catch(Exception e) {
if (DEBUG) {
System.out.println(">>> KrbKdcReq send: error trying " +
tempKdc);
e.printStackTrace(System.out);
}
KdcAccessibility.addBad(tempKdc);
throw e;
}
}
// send the AS Request to the specified KDC
private byte[] send(byte[] obuf, String tempKdc, boolean useTCP)
throws IOException, KrbException {
if (obuf == null)
return null;
int port = Krb5.KDC_INET_DEFAULT_PORT;
int retries = getRealmSpecificValue(
realm, "max_retries", defaultKdcRetryLimit);
int timeout = getRealmSpecificValue(
realm, "kdc_timeout", defaultKdcTimeout);
if (badPolicy == BpType.TRY_LESS &&
KdcAccessibility.isBad(tempKdc)) {
if (retries > tryLessMaxRetries) {
retries = tryLessMaxRetries; // less retries
}
if (timeout > tryLessTimeout) {
timeout = tryLessTimeout; // less time
}
}
String kdc = null;
String portStr = null;
if (tempKdc.charAt(0) == '[') { // Explicit IPv6 in []
int pos = tempKdc.indexOf(']', 1);
if (pos == -1) {
throw new IOException("Illegal KDC: " + tempKdc);
}
kdc = tempKdc.substring(1, pos);
if (pos != tempKdc.length() - 1) { // with port number
if (tempKdc.charAt(pos+1) != ':') {
throw new IOException("Illegal KDC: " + tempKdc);
}
portStr = tempKdc.substring(pos+2);
}
} else {
int colon = tempKdc.indexOf(':');
if (colon == -1) { // Hostname or IPv4 host only
kdc = tempKdc;
} else {
int nextColon = tempKdc.indexOf(':', colon+1);
if (nextColon > 0) { // >=2 ":", IPv6 with no port
kdc = tempKdc;
} else { // 1 ":", hostname or IPv4 with port
kdc = tempKdc.substring(0, colon);
portStr = tempKdc.substring(colon+1);
}
}
}
if (portStr != null) {
int tempPort = parsePositiveIntString(portStr);
if (tempPort > 0)
port = tempPort;
}
if (DEBUG) {
System.out.println(">>> KrbKdcReq send: kdc=" + kdc
+ (useTCP ? " TCP:":" UDP:")
+ port + ", timeout="
+ timeout
+ ", number of retries ="
+ retries
+ ", #bytes=" + obuf.length);
}
KdcCommunication kdcCommunication =
new KdcCommunication(kdc, port, useTCP, timeout, retries, obuf);
try {
byte[] ibuf = AccessController.doPrivileged(kdcCommunication);
if (DEBUG) {
System.out.println(">>> KrbKdcReq send: #bytes read="
+ (ibuf != null ? ibuf.length : 0));
}
return ibuf;
} catch (PrivilegedActionException e) {
Exception wrappedException = e.getException();
if (wrappedException instanceof IOException) {
throw (IOException) wrappedException;
} else {
throw (KrbException) wrappedException;
}
}
}
private static class KdcCommunication
implements PrivilegedExceptionAction<byte[]> {
private String kdc;
private int port;
private boolean useTCP;
private int timeout;
private int retries;
private byte[] obuf;
public KdcCommunication(String kdc, int port, boolean useTCP,
int timeout, int retries, byte[] obuf) {
this.kdc = kdc;
this.port = port;
this.useTCP = useTCP;
this.timeout = timeout;
this.retries = retries;
this.obuf = obuf;
}
// The caller only casts IOException and KrbException so don't
// add any new ones!
public byte[] run() throws IOException, KrbException {
byte[] ibuf = null;
for (int i=1; i <= retries; i++) {
String proto = useTCP?"TCP":"UDP";
try (NetClient kdcClient = NetClient.getInstance(
proto, kdc, port, timeout)) {
if (DEBUG) {
System.out.println(">>> KDCCommunication: kdc=" + kdc
+ " " + proto + ":"
+ port + ", timeout="
+ timeout
+ ",Attempt =" + i
+ ", #bytes=" + obuf.length);
}
try {
/*
* Send the data to the kdc.
*/
kdcClient.send(obuf);
/*
* And get a response.
*/
ibuf = kdcClient.receive();
break;
} catch (SocketTimeoutException se) {
if (DEBUG) {
System.out.println ("SocketTimeOutException with " +
"attempt: " + i);
}
if (i == retries) {
ibuf = null;
throw se;
}
}
}
}
return ibuf;
}
}
/**
* Returns krb5.conf setting of {@code key} for a specific realm,
* which can be:
* 1. defined in the sub-stanza for the given realm inside [realms], or
* 2. defined in [libdefaults], or
* 3. defValue
* @param realm the given realm in which the setting is requested. Returns
* the global setting if null
* @param key the key for the setting
* @param defValue default value
* @return a value for the key
*/
private int getRealmSpecificValue(String realm, String key, int defValue) {
int v = defValue;
if (realm == null) return v;
int temp = -1;
try {
String value =
Config.getInstance().get("realms", realm, key);
temp = parsePositiveIntString(value);
} catch (Exception exc) {
// Ignored, defValue will be picked up
}
if (temp > 0) v = temp;
return v;
}
private static int parsePositiveIntString(String intString) {
if (intString == null)
return -1;
int ret = -1;
try {
ret = Integer.parseInt(intString);
} catch (Exception exc) {
return -1;
}
if (ret >= 0)
return ret;
return -1;
}
/**
* Maintains a KDC accessible list. Unavailable KDCs are put into a
* blacklist, when a KDC in the blacklist is available, it's removed
* from there. No insertion order in the blacklist.
*
* There are two methods to deal with KDCs in the blacklist. 1. Only try
* them when there's no KDC not on the blacklist. 2. Still try them, but
* with lesser number of retries and smaller timeout value.
*/
static class KdcAccessibility {
// Known bad KDCs
private static Set<String> bads = new HashSet<>();
private static synchronized void addBad(String kdc) {
if (DEBUG) {
System.out.println(">>> KdcAccessibility: add " + kdc);
}
bads.add(kdc);
}
private static synchronized void removeBad(String kdc) {
if (DEBUG) {
System.out.println(">>> KdcAccessibility: remove " + kdc);
}
bads.remove(kdc);
}
private static synchronized boolean isBad(String kdc) {
return bads.contains(kdc);
}
private static synchronized void reset() {
if (DEBUG) {
System.out.println(">>> KdcAccessibility: reset");
}
bads.clear();
}
// Returns a preferred KDC list by putting the bad ones at the end
private static synchronized List<String> list(String kdcList) {
StringTokenizer st = new StringTokenizer(kdcList);
List<String> list = new ArrayList<>();
if (badPolicy == BpType.TRY_LAST) {
List<String> badkdcs = new ArrayList<>();
while (st.hasMoreTokens()) {
String t = st.nextToken();
if (bads.contains(t)) badkdcs.add(t);
else list.add(t);
}
// Bad KDCs are put at last
list.addAll(badkdcs);
} else {
// All KDCs are returned in their original order,
// This include TRY_LESS and NONE
while (st.hasMoreTokens()) {
list.add(st.nextToken());
}
}
return list;
}
}
}
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