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/*
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 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.
 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.
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package sun.security.krb5.internal;

import sun.security.krb5.*;
import sun.security.util.DerValue;

import java.io.IOException;
import java.util.LinkedList;
import java.util.List;

This class is a utility that contains much of the TGS-Exchange protocol. It is used by ../Credentials.java for service ticket acquisition in both the normal and the x-realm case.
/** * This class is a utility that contains much of the TGS-Exchange * protocol. It is used by ../Credentials.java for service ticket * acquisition in both the normal and the x-realm case. */
public class CredentialsUtil { private static boolean DEBUG = sun.security.krb5.internal.Krb5.DEBUG; private static enum S4U2Type { NONE, SELF, PROXY }
Used by a middle server to acquire credentials on behalf of a client to itself using the S4U2self extension.
Params:
  • client – the client to impersonate
  • ccreds – the TGT of the middle service
Returns:the new creds (cname=client, sname=middle)
/** * Used by a middle server to acquire credentials on behalf of a * client to itself using the S4U2self extension. * @param client the client to impersonate * @param ccreds the TGT of the middle service * @return the new creds (cname=client, sname=middle) */
public static Credentials acquireS4U2selfCreds(PrincipalName client, Credentials ccreds) throws KrbException, IOException { if (!ccreds.isForwardable()) { throw new KrbException("S4U2self needs a FORWARDABLE ticket"); } PrincipalName sname = ccreds.getClient(); String uRealm = client.getRealmString(); String localRealm = ccreds.getClient().getRealmString(); if (!uRealm.equals(localRealm)) { // Referrals will be required because the middle service // and the client impersonated are on different realms. if (Config.DISABLE_REFERRALS) { throw new KrbException("Cross-realm S4U2Self request not" + " possible when referrals are disabled."); } if (ccreds.getClientAlias() != null) { // If the name was canonicalized, the user pick // has preference. This gives the possibility of // using FQDNs that KDCs may use to return referrals. // I.e.: a SVC/host.realm-2.com@REALM-1.COM name // may be used by REALM-1.COM KDC to return a // referral to REALM-2.COM. sname = ccreds.getClientAlias(); } sname = new PrincipalName(sname.getNameType(), sname.getNameStrings(), new Realm(uRealm)); } Credentials creds = serviceCreds( KDCOptions.with(KDCOptions.FORWARDABLE), ccreds, ccreds.getClient(), sname, null, new PAData[] { new PAData(Krb5.PA_FOR_USER, new PAForUserEnc(client, ccreds.getSessionKey()).asn1Encode()), new PAData(Krb5.PA_PAC_OPTIONS, new PaPacOptions() .setResourceBasedConstrainedDelegation(true) .setClaims(true) .asn1Encode()) }, S4U2Type.SELF); if (!creds.getClient().equals(client)) { throw new KrbException("S4U2self request not honored by KDC"); } if (!creds.isForwardable()) { throw new KrbException("S4U2self ticket must be FORWARDABLE"); } return creds; }
Used by a middle server to acquire a service ticket to a backend server using the S4U2proxy extension.
Params:
  • backend – the name of the backend service
  • second – the client's service ticket to the middle server
  • ccreds – the TGT of the middle server
Returns:the creds (cname=client, sname=backend)
/** * Used by a middle server to acquire a service ticket to a backend * server using the S4U2proxy extension. * @param backend the name of the backend service * @param second the client's service ticket to the middle server * @param ccreds the TGT of the middle server * @return the creds (cname=client, sname=backend) */
public static Credentials acquireS4U2proxyCreds( String backend, Ticket second, PrincipalName client, Credentials ccreds) throws KrbException, IOException { PrincipalName backendPrincipal = new PrincipalName(backend); String backendRealm = backendPrincipal.getRealmString(); String localRealm = ccreds.getClient().getRealmString(); if (!backendRealm.equals(localRealm)) { // The middle service and the backend service are on // different realms, so referrals will be required. if (Config.DISABLE_REFERRALS) { throw new KrbException("Cross-realm S4U2Proxy request not" + " possible when referrals are disabled."); } backendPrincipal = new PrincipalName( backendPrincipal.getNameType(), backendPrincipal.getNameStrings(), new Realm(localRealm)); } Credentials creds = serviceCreds(KDCOptions.with( KDCOptions.CNAME_IN_ADDL_TKT, KDCOptions.FORWARDABLE), ccreds, ccreds.getClient(), backendPrincipal, new Ticket[] {second}, new PAData[] { new PAData(Krb5.PA_PAC_OPTIONS, new PaPacOptions() .setResourceBasedConstrainedDelegation(true) .setClaims(true) .asn1Encode()) }, S4U2Type.PROXY); if (!creds.getClient().equals(client)) { throw new KrbException("S4U2proxy request not honored by KDC"); } return creds; }
Acquires credentials for a specified service using initial credential. When the service has a different realm from the initial credential, we do cross-realm authentication - first, we use the current credential to get a cross-realm credential from the local KDC, then use that cross-realm credential to request service credential from the foreign KDC.
Params:
  • service – the name of service principal
  • ccreds – client's initial credential
/** * Acquires credentials for a specified service using initial * credential. When the service has a different realm from the initial * credential, we do cross-realm authentication - first, we use the * current credential to get a cross-realm credential from the local KDC, * then use that cross-realm credential to request service credential * from the foreign KDC. * * @param service the name of service principal * @param ccreds client's initial credential */
public static Credentials acquireServiceCreds( String service, Credentials ccreds) throws KrbException, IOException { PrincipalName sname = new PrincipalName(service, PrincipalName.KRB_NT_UNKNOWN); return serviceCreds(sname, ccreds); }
Gets a TGT to another realm
Params:
  • localRealm – this realm
  • serviceRealm – the other realm, cannot equals to localRealm
  • ccreds – TGT in this realm
  • okAsDelegate – an [out] argument to receive the okAsDelegate property. True only if all realms allow delegation.
Throws:
Returns:the TGT for the other realm, null if cannot find a path
/** * Gets a TGT to another realm * @param localRealm this realm * @param serviceRealm the other realm, cannot equals to localRealm * @param ccreds TGT in this realm * @param okAsDelegate an [out] argument to receive the okAsDelegate * property. True only if all realms allow delegation. * @return the TGT for the other realm, null if cannot find a path * @throws KrbException if something goes wrong */
private static Credentials getTGTforRealm(String localRealm, String serviceRealm, Credentials ccreds, boolean[] okAsDelegate) throws KrbException { // Get a list of realms to traverse String[] realms = Realm.getRealmsList(localRealm, serviceRealm); int i = 0, k = 0; Credentials cTgt = null, newTgt = null, theTgt = null; PrincipalName tempService = null; String newTgtRealm = null; okAsDelegate[0] = true; for (cTgt = ccreds, i = 0; i < realms.length;) { tempService = PrincipalName.tgsService(serviceRealm, realms[i]); if (DEBUG) { System.out.println( ">>> Credentials acquireServiceCreds: main loop: [" + i +"] tempService=" + tempService); } try { newTgt = serviceCreds(tempService, cTgt); } catch (Exception exc) { newTgt = null; } if (newTgt == null) { if (DEBUG) { System.out.println(">>> Credentials acquireServiceCreds: " + "no tgt; searching thru capath"); } /* * No tgt found. Let's go thru the realms list one by one. */ for (newTgt = null, k = i+1; newTgt == null && k < realms.length; k++) { tempService = PrincipalName.tgsService(realms[k], realms[i]); if (DEBUG) { System.out.println( ">>> Credentials acquireServiceCreds: " + "inner loop: [" + k + "] tempService=" + tempService); } try { newTgt = serviceCreds(tempService, cTgt); } catch (Exception exc) { newTgt = null; } } } // Ends 'if (newTgt == null)' if (newTgt == null) { if (DEBUG) { System.out.println(">>> Credentials acquireServiceCreds: " + "no tgt; cannot get creds"); } break; } /* * We have a tgt. It may or may not be for the target. * If it's for the target realm, we're done looking for a tgt. */ newTgtRealm = newTgt.getServer().getInstanceComponent(); if (okAsDelegate[0] && !newTgt.checkDelegate()) { if (DEBUG) { System.out.println(">>> Credentials acquireServiceCreds: " + "global OK-AS-DELEGATE turned off at " + newTgt.getServer()); } okAsDelegate[0] = false; } if (DEBUG) { System.out.println(">>> Credentials acquireServiceCreds: " + "got tgt"); } if (newTgtRealm.equals(serviceRealm)) { /* We got the right tgt */ theTgt = newTgt; break; } /* * The new tgt is not for the target realm. * See if the realm of the new tgt is in the list of realms * and continue looking from there. */ for (k = i+1; k < realms.length; k++) { if (newTgtRealm.equals(realms[k])) { break; } } if (k < realms.length) { /* * (re)set the counter so we start looking * from the realm we just obtained a tgt for. */ i = k; cTgt = newTgt; if (DEBUG) { System.out.println(">>> Credentials acquireServiceCreds: " + "continuing with main loop counter reset to " + i); } continue; } else { /* * The new tgt's realm is not in the hierarchy of realms. * It's probably not safe to get a tgt from * a tgs that is outside the known list of realms. * Give up now. */ break; } } // Ends outermost/main 'for' loop return theTgt; } /* * This method does the real job to request the service credential. */ private static Credentials serviceCreds( PrincipalName service, Credentials ccreds) throws KrbException, IOException { return serviceCreds(new KDCOptions(), ccreds, ccreds.getClient(), service, null, null, S4U2Type.NONE); } /* * Obtains credentials for a service (TGS). * Cross-realm referrals are handled if enabled. A fallback scheme * without cross-realm referrals supports is used in case of server * error to maintain backward compatibility. */ private static Credentials serviceCreds( KDCOptions options, Credentials asCreds, PrincipalName cname, PrincipalName sname, Ticket[] additionalTickets, PAData[] extraPAs, S4U2Type s4u2Type) throws KrbException, IOException { if (!Config.DISABLE_REFERRALS) { try { return serviceCredsReferrals(options, asCreds, cname, sname, s4u2Type, additionalTickets, extraPAs); } catch (KrbException e) { // Server may raise an error if CANONICALIZE is true. // Try CANONICALIZE false. } } return serviceCredsSingle(options, asCreds, cname, asCreds.getClientAlias(), sname, sname, s4u2Type, additionalTickets, extraPAs); } /* * Obtains credentials for a service (TGS). * May handle and follow cross-realm referrals as defined by RFC 6806. */ private static Credentials serviceCredsReferrals( KDCOptions options, Credentials asCreds, PrincipalName cname, PrincipalName sname, S4U2Type s4u2Type, Ticket[] additionalTickets, PAData[] extraPAs) throws KrbException, IOException { options = new KDCOptions(options.toBooleanArray()); options.set(KDCOptions.CANONICALIZE, true); PrincipalName cSname = sname; PrincipalName refSname = sname; // May change with referrals Credentials creds = null; boolean isReferral = false; List<String> referrals = new LinkedList<>(); PrincipalName clientAlias = asCreds.getClientAlias(); while (referrals.size() <= Config.MAX_REFERRALS) { ReferralsCache.ReferralCacheEntry ref = ReferralsCache.get(cname, sname, refSname.getRealmString()); String toRealm = null; if (ref == null) { creds = serviceCredsSingle(options, asCreds, cname, clientAlias, refSname, cSname, s4u2Type, additionalTickets, extraPAs); PrincipalName server = creds.getServer(); if (!refSname.equals(server)) { String[] serverNameStrings = server.getNameStrings(); if (serverNameStrings.length == 2 && serverNameStrings[0].equals( PrincipalName.TGS_DEFAULT_SRV_NAME) && !refSname.getRealmAsString().equals( serverNameStrings[1])) { // Server Name (sname) has the following format: // krbtgt/TO-REALM.COM@FROM-REALM.COM if (s4u2Type == S4U2Type.NONE) { // Do not store S4U2Self or S4U2Proxy referral // TGTs in the cache. Caching such tickets is not // defined in MS-SFU and may cause unexpected // results when using them in a different context. ReferralsCache.put(cname, sname, server.getRealmString(), serverNameStrings[1], creds); } toRealm = serverNameStrings[1]; isReferral = true; } } } else { creds = ref.getCreds(); toRealm = ref.getToRealm(); isReferral = true; } if (isReferral) { if (s4u2Type == S4U2Type.PROXY) { Credentials[] credsInOut = new Credentials[] {creds, null}; toRealm = handleS4U2ProxyReferral(asCreds, credsInOut, sname); creds = credsInOut[0]; if (additionalTickets == null || additionalTickets.length == 0 || credsInOut[1] == null) { throw new KrbException("Additional tickets expected" + " for S4U2Proxy."); } additionalTickets[0] = credsInOut[1].getTicket(); } else if (s4u2Type == S4U2Type.SELF) { handleS4U2SelfReferral(extraPAs, asCreds, creds); } if (referrals.contains(toRealm)) { // Referrals loop detected return null; } asCreds = creds; refSname = new PrincipalName(refSname.getNameString(), refSname.getNameType(), toRealm); referrals.add(toRealm); isReferral = false; continue; } break; } return creds; } /* * Obtains credentials for a service (TGS). * If the service realm is different than the one in the TGT, a new TGT for * the service realm is obtained first (see getTGTforRealm call). This is * not expected when following cross-realm referrals because the referral * TGT realm matches the service realm. */ private static Credentials serviceCredsSingle( KDCOptions options, Credentials asCreds, PrincipalName cname, PrincipalName clientAlias, PrincipalName refSname, PrincipalName sname, S4U2Type s4u2Type, Ticket[] additionalTickets, PAData[] extraPAs) throws KrbException, IOException { Credentials theCreds = null; boolean[] okAsDelegate = new boolean[]{true}; String[] serverAsCredsNames = asCreds.getServer().getNameStrings(); String tgtRealm = serverAsCredsNames[1]; String serviceRealm = refSname.getRealmString(); if (!serviceRealm.equals(tgtRealm)) { // This is a cross-realm service request if (DEBUG) { System.out.println(">>> serviceCredsSingle:" + " cross-realm authentication"); System.out.println(">>> serviceCredsSingle:" + " obtaining credentials from " + tgtRealm + " to " + serviceRealm); } Credentials newTgt = getTGTforRealm(tgtRealm, serviceRealm, asCreds, okAsDelegate); if (newTgt == null) { throw new KrbApErrException(Krb5.KRB_AP_ERR_GEN_CRED, "No service creds"); } if (DEBUG) { System.out.println(">>> Cross-realm TGT Credentials" + " serviceCredsSingle: "); Credentials.printDebug(newTgt); } if (s4u2Type == S4U2Type.SELF) { handleS4U2SelfReferral(extraPAs, asCreds, newTgt); } asCreds = newTgt; cname = asCreds.getClient(); } else if (DEBUG) { System.out.println(">>> Credentials serviceCredsSingle:" + " same realm"); } KrbTgsReq req = new KrbTgsReq(options, asCreds, cname, clientAlias, refSname, sname, additionalTickets, extraPAs); theCreds = req.sendAndGetCreds(); if (theCreds != null) { if (DEBUG) { System.out.println(">>> TGS credentials serviceCredsSingle:"); Credentials.printDebug(theCreds); } if (!okAsDelegate[0]) { theCreds.resetDelegate(); } } return theCreds; }
PA-FOR-USER may need to be regenerated if credentials change. This may happen when obtaining a TGT for a different realm or when using a referral TGT.
/** * PA-FOR-USER may need to be regenerated if credentials * change. This may happen when obtaining a TGT for a * different realm or when using a referral TGT. */
private static void handleS4U2SelfReferral(PAData[] pas, Credentials oldCeds, Credentials newCreds) throws Asn1Exception, KrbException, IOException { if (DEBUG) { System.out.println(">>> Handling S4U2Self referral"); } for (int i = 0; i < pas.length; i++) { PAData pa = pas[i]; if (pa.getType() == Krb5.PA_FOR_USER) { PAForUserEnc paForUser = new PAForUserEnc( new DerValue(pa.getValue()), oldCeds.getSessionKey()); pas[i] = new PAData(Krb5.PA_FOR_USER, new PAForUserEnc(paForUser.getName(), newCreds.getSessionKey()).asn1Encode()); break; } } }
This method is called after receiving the first realm referral for a S4U2Proxy request. The credentials and tickets needed for the final S4U2Proxy request (in the referrals chain) are returned. Referrals are handled as described by MS-SFU (section 3.1.5.2.2 Receives Referral).
Params:
  • asCreds – middle service credentials used for the first S4U2Proxy request
  • credsInOut – (in/out parameter): * input: first S4U2Proxy referral TGT received, null * output: referral TGT for final S4U2Proxy service request, client referral TGT for final S4U2Proxy service request (to be sent as additional-ticket)
  • sname – the backend service name
  • additionalTickets – (out parameter): the additional ticket for the last S4U2Proxy request is returned
Returns:the backend realm for the last S4U2Proxy request
/** * This method is called after receiving the first realm referral for * a S4U2Proxy request. The credentials and tickets needed for the * final S4U2Proxy request (in the referrals chain) are returned. * * Referrals are handled as described by MS-SFU (section 3.1.5.2.2 * Receives Referral). * * @param asCreds middle service credentials used for the first S4U2Proxy * request * @param credsInOut (in/out parameter): * * input: first S4U2Proxy referral TGT received, null * * output: referral TGT for final S4U2Proxy service request, * client referral TGT for final S4U2Proxy service request * (to be sent as additional-ticket) * @param sname the backend service name * @param additionalTickets (out parameter): the additional ticket for the * last S4U2Proxy request is returned * @return the backend realm for the last S4U2Proxy request */
private static String handleS4U2ProxyReferral(Credentials asCreds, Credentials[] credsInOut, PrincipalName sname) throws KrbException, IOException { if (DEBUG) { System.out.println(">>> Handling S4U2Proxy referral"); } Credentials refTGT = null; // Get a credential for the middle service to the backend so we know // the backend realm, as described in MS-SFU (section 3.1.5.2.2). Credentials middleSvcCredsInBackendRealm = serviceCreds(sname, asCreds); String backendRealm = middleSvcCredsInBackendRealm.getServer().getRealmString(); String toRealm = credsInOut[0].getServer().getNameStrings()[1]; if (!toRealm.equals(backendRealm)) { // More than 1 hop. Follow the referrals chain and obtain a // TGT for the backend realm. refTGT = getTGTforRealm(toRealm, backendRealm, credsInOut[0], new boolean[1]); } else { // There was only 1 hop. The referral TGT received is already // for the backend realm. refTGT = credsInOut[0]; } credsInOut[0] = getTGTforRealm(asCreds.getClient().getRealmString(), backendRealm, asCreds, new boolean[1]); credsInOut[1] = refTGT; return backendRealm; } }