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	/*
	* Copyright (c) 2012, 2017, 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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.security.provider.certpath;

	import java.io.IOException;
	import java.math.BigInteger;
	import java.net.URI;
	import java.net.URISyntaxException;
	import java.security.AccessController;
	import java.security.InvalidAlgorithmParameterException;
	import java.security.NoSuchAlgorithmException;
	import java.security.PrivilegedAction;
	import java.security.PublicKey;
	import java.security.Security;
	import java.security.cert.CertPathValidatorException.BasicReason;
	import java.security.cert.Extension;
	import java.security.cert.*;
	import java.util.*;
	import javax.security.auth.x500.X500Principal;

	import static sun.security.provider.certpath.OCSP.*;
	import static sun.security.provider.certpath.PKIX.*;
	import sun.security.x509.*;
	import static sun.security.x509.PKIXExtensions.*;
	import sun.security.util.Debug;

	class RevocationChecker extends PKIXRevocationChecker {

	private static final Debug debug = Debug.getInstance("certpath");

	private TrustAnchor anchor;
	private ValidatorParams params;
	private boolean onlyEE;
	private boolean softFail;
	private boolean crlDP;
	private URI responderURI;
	private X509Certificate responderCert;
	private List<CertStore> certStores;
	private Map<X509Certificate, byte[]> ocspResponses;
	private List<Extension> ocspExtensions;
	private final boolean legacy;
	private LinkedList<CertPathValidatorException> softFailExceptions =
	new LinkedList<>();

	// state variables
	private OCSPResponse.IssuerInfo issuerInfo;
	private PublicKey prevPubKey;
	private boolean crlSignFlag;
	private int certIndex;

	private enum Mode { PREFER_OCSP, PREFER_CRLS, ONLY_CRLS, ONLY_OCSP };
	private Mode mode = Mode.PREFER_OCSP;

	private static class RevocationProperties {
	boolean onlyEE;
	boolean ocspEnabled;
	boolean crlDPEnabled;
	String ocspUrl;
	String ocspSubject;
	String ocspIssuer;
	String ocspSerial;
	}

	RevocationChecker() {
	legacy = false;
	}

	RevocationChecker(TrustAnchor anchor, ValidatorParams params)
	throws CertPathValidatorException
	{
	legacy = true;
	init(anchor, params);
	}

	void init(TrustAnchor anchor, ValidatorParams params)
	throws CertPathValidatorException
	{
	RevocationProperties rp = getRevocationProperties();
	URI uri = getOcspResponder();
	responderURI = (uri == null) ? toURI(rp.ocspUrl) : uri;
	X509Certificate cert = getOcspResponderCert();
	responderCert = (cert == null)
	? getResponderCert(rp, params.trustAnchors(),
	params.certStores())
	: cert;
	Set<Option> options = getOptions();
	for (Option option : options) {
	switch (option) {
	case ONLY_END_ENTITY:
	case PREFER_CRLS:
	case SOFT_FAIL:
	case NO_FALLBACK:
	break;
	default:
	throw new CertPathValidatorException(
	"Unrecognized revocation parameter option: " + option);
	}
	}
	softFail = options.contains(Option.SOFT_FAIL);

	// set mode, only end entity flag
	if (legacy) {
	mode = (rp.ocspEnabled) ? Mode.PREFER_OCSP : Mode.ONLY_CRLS;
	onlyEE = rp.onlyEE;
	} else {
	if (options.contains(Option.NO_FALLBACK)) {
	if (options.contains(Option.PREFER_CRLS)) {
	mode = Mode.ONLY_CRLS;
	} else {
	mode = Mode.ONLY_OCSP;
	}
	} else if (options.contains(Option.PREFER_CRLS)) {
	mode = Mode.PREFER_CRLS;
	}
	onlyEE = options.contains(Option.ONLY_END_ENTITY);
	}
	if (legacy) {
	crlDP = rp.crlDPEnabled;
	} else {
	crlDP = true;
	}
	ocspResponses = getOcspResponses();
	ocspExtensions = getOcspExtensions();

	this.anchor = anchor;
	this.params = params;
	this.certStores = new ArrayList<>(params.certStores());
	try {
	this.certStores.add(CertStore.getInstance("Collection",
	new CollectionCertStoreParameters(params.certificates())));
	} catch (InvalidAlgorithmParameterException \|
	NoSuchAlgorithmException e) {
	// should never occur but not necessarily fatal, so log it,
	// ignore and continue
	if (debug != null) {
	debug.println("RevocationChecker: " +
	"error creating Collection CertStore: " + e);
	}
	}
	}

	private static URI toURI(String uriString)
	throws CertPathValidatorException
	{
	try {
	if (uriString != null) {
	return new URI(uriString);
	}
	return null;
	} catch (URISyntaxException e) {
	throw new CertPathValidatorException(
	"cannot parse ocsp.responderURL property", e);
	}
	}

	private static RevocationProperties getRevocationProperties() {
	return AccessController.doPrivileged(
	new PrivilegedAction<RevocationProperties>() {
	public RevocationProperties run() {
	RevocationProperties rp = new RevocationProperties();
	String onlyEE = Security.getProperty(
	"com.sun.security.onlyCheckRevocationOfEECert");
	rp.onlyEE = onlyEE != null
	&& onlyEE.equalsIgnoreCase("true");
	String ocspEnabled = Security.getProperty("ocsp.enable");
	rp.ocspEnabled = ocspEnabled != null
	&& ocspEnabled.equalsIgnoreCase("true");
	rp.ocspUrl = Security.getProperty("ocsp.responderURL");
	rp.ocspSubject
	= Security.getProperty("ocsp.responderCertSubjectName");
	rp.ocspIssuer
	= Security.getProperty("ocsp.responderCertIssuerName");
	rp.ocspSerial
	= Security.getProperty("ocsp.responderCertSerialNumber");
	rp.crlDPEnabled
	= Boolean.getBoolean("com.sun.security.enableCRLDP");
	return rp;
	}
	}
	);
	}

	private static X509Certificate getResponderCert(RevocationProperties rp,
	Set<TrustAnchor> anchors,
	List<CertStore> stores)
	throws CertPathValidatorException
	{
	if (rp.ocspSubject != null) {
	return getResponderCert(rp.ocspSubject, anchors, stores);
	} else if (rp.ocspIssuer != null && rp.ocspSerial != null) {
	return getResponderCert(rp.ocspIssuer, rp.ocspSerial,
	anchors, stores);
	} else if (rp.ocspIssuer != null \|\| rp.ocspSerial != null) {
	throw new CertPathValidatorException(
	"Must specify both ocsp.responderCertIssuerName and " +
	"ocsp.responderCertSerialNumber properties");
	}
	return null;
	}

	private static X509Certificate getResponderCert(String subject,
	Set<TrustAnchor> anchors,
	List<CertStore> stores)
	throws CertPathValidatorException
	{
	X509CertSelector sel = new X509CertSelector();
	try {
	sel.setSubject(new X500Principal(subject));
	} catch (IllegalArgumentException e) {
	throw new CertPathValidatorException(
	"cannot parse ocsp.responderCertSubjectName property", e);
	}
	return getResponderCert(sel, anchors, stores);
	}

	private static X509Certificate getResponderCert(String issuer,
	String serial,
	Set<TrustAnchor> anchors,
	List<CertStore> stores)
	throws CertPathValidatorException
	{
	X509CertSelector sel = new X509CertSelector();
	try {
	sel.setIssuer(new X500Principal(issuer));
	} catch (IllegalArgumentException e) {
	throw new CertPathValidatorException(
	"cannot parse ocsp.responderCertIssuerName property", e);
	}
	try {
	sel.setSerialNumber(new BigInteger(stripOutSeparators(serial), 16));
	} catch (NumberFormatException e) {
	throw new CertPathValidatorException(
	"cannot parse ocsp.responderCertSerialNumber property", e);
	}
	return getResponderCert(sel, anchors, stores);
	}

	private static X509Certificate getResponderCert(X509CertSelector sel,
	Set<TrustAnchor> anchors,
	List<CertStore> stores)
	throws CertPathValidatorException
	{
	// first check TrustAnchors
	for (TrustAnchor anchor : anchors) {
	X509Certificate cert = anchor.getTrustedCert();
	if (cert == null) {
	continue;
	}
	if (sel.match(cert)) {
	return cert;
	}
	}
	// now check CertStores
	for (CertStore store : stores) {
	try {
	Collection<? extends Certificate> certs =
	store.getCertificates(sel);
	if (!certs.isEmpty()) {
	return (X509Certificate)certs.iterator().next();
	}
	} catch (CertStoreException e) {
	// ignore and try next CertStore
	if (debug != null) {
	debug.println("CertStore exception:" + e);
	}
	continue;
	}
	}
	throw new CertPathValidatorException(
	"Cannot find the responder's certificate " +
	"(set using the OCSP security properties).");
	}

	@Override
	public void init(boolean forward) throws CertPathValidatorException {
	if (forward) {
	throw new
	CertPathValidatorException("forward checking not supported");
	}
	if (anchor != null) {
	issuerInfo = new OCSPResponse.IssuerInfo(anchor);
	prevPubKey = issuerInfo.getPublicKey();

	}
	crlSignFlag = true;
	if (params != null && params.certPath() != null) {
	certIndex = params.certPath().getCertificates().size() - 1;
	} else {
	certIndex = -1;
	}
	softFailExceptions.clear();
	}

	@Override
	public boolean isForwardCheckingSupported() {
	return false;
	}

	@Override
	public Set<String> getSupportedExtensions() {
	return null;
	}

	@Override
	public List<CertPathValidatorException> getSoftFailExceptions() {
	return Collections.unmodifiableList(softFailExceptions);
	}

	@Override
	public void check(Certificate cert, Collection<String> unresolvedCritExts)
	throws CertPathValidatorException
	{
	check((X509Certificate)cert, unresolvedCritExts,
	prevPubKey, crlSignFlag);
	}

	private void check(X509Certificate xcert,
	Collection<String> unresolvedCritExts,
	PublicKey pubKey, boolean crlSignFlag)
	throws CertPathValidatorException
	{
	if (debug != null) {
	debug.println("RevocationChecker.check: checking cert" +
	"\n SN: " + Debug.toHexString(xcert.getSerialNumber()) +
	"\n Subject: " + xcert.getSubjectX500Principal() +
	"\n Issuer: " + xcert.getIssuerX500Principal());
	}
	try {
	if (onlyEE && xcert.getBasicConstraints() != -1) {
	if (debug != null) {
	debug.println("Skipping revocation check; cert is not " +
	"an end entity cert");
	}
	return;
	}
	switch (mode) {
	case PREFER_OCSP:
	case ONLY_OCSP:
	checkOCSP(xcert, unresolvedCritExts);
	break;
	case PREFER_CRLS:
	case ONLY_CRLS:
	checkCRLs(xcert, unresolvedCritExts, null,
	pubKey, crlSignFlag);
	break;
	}
	} catch (CertPathValidatorException e) {
	if (e.getReason() == BasicReason.REVOKED) {
	throw e;
	}
	boolean eSoftFail = isSoftFailException(e);
	if (eSoftFail) {
	if (mode == Mode.ONLY_OCSP \|\| mode == Mode.ONLY_CRLS) {
	return;
	}
	} else {
	if (mode == Mode.ONLY_OCSP \|\| mode == Mode.ONLY_CRLS) {
	throw e;
	}
	}
	CertPathValidatorException cause = e;
	// Otherwise, failover
	if (debug != null) {
	debug.println("RevocationChecker.check() " + e.getMessage());
	debug.println("RevocationChecker.check() preparing to failover");
	}
	try {
	switch (mode) {
	case PREFER_OCSP:
	checkCRLs(xcert, unresolvedCritExts, null,
	pubKey, crlSignFlag);
	break;
	case PREFER_CRLS:
	checkOCSP(xcert, unresolvedCritExts);
	break;
	}
	} catch (CertPathValidatorException x) {
	if (debug != null) {
	debug.println("RevocationChecker.check() failover failed");
	debug.println("RevocationChecker.check() " + x.getMessage());
	}
	if (x.getReason() == BasicReason.REVOKED) {
	throw x;
	}
	if (!isSoftFailException(x)) {
	cause.addSuppressed(x);
	throw cause;
	} else {
	// only pass if both exceptions were soft failures
	if (!eSoftFail) {
	throw cause;
	}
	}
	}
	} finally {
	updateState(xcert);
	}
	}

	private boolean isSoftFailException(CertPathValidatorException e) {
	if (softFail &&
	e.getReason() == BasicReason.UNDETERMINED_REVOCATION_STATUS)
	{
	// recreate exception with correct index
	CertPathValidatorException e2 = new CertPathValidatorException(
	e.getMessage(), e.getCause(), params.certPath(), certIndex,
	e.getReason());
	softFailExceptions.addFirst(e2);
	return true;
	}
	return false;
	}

	private void updateState(X509Certificate cert)
	throws CertPathValidatorException
	{
	issuerInfo = new OCSPResponse.IssuerInfo(anchor, cert);

	// Make new public key if parameters are missing
	PublicKey pubKey = cert.getPublicKey();
	if (PKIX.isDSAPublicKeyWithoutParams(pubKey)) {
	// pubKey needs to inherit DSA parameters from prev key
	pubKey = BasicChecker.makeInheritedParamsKey(pubKey, prevPubKey);
	}
	prevPubKey = pubKey;
	crlSignFlag = certCanSignCrl(cert);
	if (certIndex > 0) {
	certIndex--;
	}
	}

	// Maximum clock skew in milliseconds (15 minutes) allowed when checking
	// validity of CRLs
	private static final long MAX_CLOCK_SKEW = 900000;
	private void checkCRLs(X509Certificate cert,
	Collection<String> unresolvedCritExts,
	Set<X509Certificate> stackedCerts,
	PublicKey pubKey, boolean signFlag)
	throws CertPathValidatorException
	{
	checkCRLs(cert, pubKey, null, signFlag, true,
	stackedCerts, params.trustAnchors());
	}

	static boolean isCausedByNetworkIssue(String type, CertStoreException cse) {
	boolean result;
	Throwable t = cse.getCause();

	switch (type) {
	case "LDAP":
	if (t != null) {
	// These two exception classes are inside java.naming module
	String cn = t.getClass().getName();
	result = (cn.equals("javax.naming.ServiceUnavailableException") \|\|
	cn.equals("javax.naming.CommunicationException"));
	} else {
	result = false;
	}
	break;
	case "SSLServer":
	result = (t != null && t instanceof IOException);
	break;
	case "URI":
	result = (t != null && t instanceof IOException);
	break;
	default:
	// we don't know about any other remote CertStore types
	return false;
	}
	return result;
	}

	private void checkCRLs(X509Certificate cert, PublicKey prevKey,
	X509Certificate prevCert, boolean signFlag,
	boolean allowSeparateKey,
	Set<X509Certificate> stackedCerts,
	Set<TrustAnchor> anchors)
	throws CertPathValidatorException
	{
	if (debug != null) {
	debug.println("RevocationChecker.checkCRLs()" +
	" ---checking revocation status ...");
	}

	// Reject circular dependencies - RFC 5280 is not explicit on how
	// to handle this, but does suggest that they can be a security
	// risk and can create unresolvable dependencies
	if (stackedCerts != null && stackedCerts.contains(cert)) {
	if (debug != null) {
	debug.println("RevocationChecker.checkCRLs()" +
	" circular dependency");
	}
	throw new CertPathValidatorException
	("Could not determine revocation status", null, null, -1,
	BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}

	Set<X509CRL> possibleCRLs = new HashSet<>();
	Set<X509CRL> approvedCRLs = new HashSet<>();
	X509CRLSelector sel = new X509CRLSelector();
	sel.setCertificateChecking(cert);
	CertPathHelper.setDateAndTime(sel, params.date(), MAX_CLOCK_SKEW);

	// First, check user-specified CertStores
	CertPathValidatorException networkFailureException = null;
	for (CertStore store : certStores) {
	try {
	for (CRL crl : store.getCRLs(sel)) {
	possibleCRLs.add((X509CRL)crl);
	}
	} catch (CertStoreException e) {
	if (debug != null) {
	debug.println("RevocationChecker.checkCRLs() " +
	"CertStoreException: " + e.getMessage());
	}
	if (networkFailureException == null &&
	isCausedByNetworkIssue(store.getType(),e)) {
	// save this exception, we may need to throw it later
	networkFailureException = new CertPathValidatorException(
	"Unable to determine revocation status due to " +
	"network error", e, null, -1,
	BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}
	}
	}

	if (debug != null) {
	debug.println("RevocationChecker.checkCRLs() " +
	"possible crls.size() = " + possibleCRLs.size());
	}
	boolean[] reasonsMask = new boolean[9];
	if (!possibleCRLs.isEmpty()) {
	// Now that we have a list of possible CRLs, see which ones can
	// be approved
	approvedCRLs.addAll(verifyPossibleCRLs(possibleCRLs, cert, prevKey,
	signFlag, reasonsMask,
	anchors));
	}

	if (debug != null) {
	debug.println("RevocationChecker.checkCRLs() " +
	"approved crls.size() = " + approvedCRLs.size());
	}

	// make sure that we have at least one CRL that _could_ cover
	// the certificate in question and all reasons are covered
	if (!approvedCRLs.isEmpty() &&
	Arrays.equals(reasonsMask, ALL_REASONS))
	{
	checkApprovedCRLs(cert, approvedCRLs);
	} else {
	// Check Distribution Points
	// all CRLs returned by the DP Fetcher have also been verified
	try {
	if (crlDP) {
	approvedCRLs.addAll(DistributionPointFetcher.getCRLs(
	sel, signFlag, prevKey, prevCert,
	params.sigProvider(), certStores, reasonsMask,
	anchors, null, params.variant(), anchor));
	}
	} catch (CertStoreException e) {
	if (e instanceof CertStoreTypeException) {
	CertStoreTypeException cste = (CertStoreTypeException)e;
	if (isCausedByNetworkIssue(cste.getType(), e)) {
	throw new CertPathValidatorException(
	"Unable to determine revocation status due to " +
	"network error", e, null, -1,
	BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}
	}
	throw new CertPathValidatorException(e);
	}
	if (!approvedCRLs.isEmpty() &&
	Arrays.equals(reasonsMask, ALL_REASONS))
	{
	checkApprovedCRLs(cert, approvedCRLs);
	} else {
	if (allowSeparateKey) {
	try {
	verifyWithSeparateSigningKey(cert, prevKey, signFlag,
	stackedCerts);
	return;
	} catch (CertPathValidatorException cpve) {
	if (networkFailureException != null) {
	// if a network issue previously prevented us from
	// retrieving a CRL from one of the user-specified
	// CertStores, throw it now so it can be handled
	// appropriately
	throw networkFailureException;
	}
	throw cpve;
	}
	} else {
	if (networkFailureException != null) {
	// if a network issue previously prevented us from
	// retrieving a CRL from one of the user-specified
	// CertStores, throw it now so it can be handled
	// appropriately
	throw networkFailureException;
	}
	throw new CertPathValidatorException(
	"Could not determine revocation status", null, null, -1,
	BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}
	}
	}
	}

	private void checkApprovedCRLs(X509Certificate cert,
	Set<X509CRL> approvedCRLs)
	throws CertPathValidatorException
	{
	// See if the cert is in the set of approved crls.
	if (debug != null) {
	BigInteger sn = cert.getSerialNumber();
	debug.println("RevocationChecker.checkApprovedCRLs() " +
	"starting the final sweep...");
	debug.println("RevocationChecker.checkApprovedCRLs()" +
	" cert SN: " + sn.toString());
	}

	CRLReason reasonCode = CRLReason.UNSPECIFIED;
	X509CRLEntryImpl entry = null;
	for (X509CRL crl : approvedCRLs) {
	X509CRLEntry e = crl.getRevokedCertificate(cert);
	if (e != null) {
	try {
	entry = X509CRLEntryImpl.toImpl(e);
	} catch (CRLException ce) {
	throw new CertPathValidatorException(ce);
	}
	if (debug != null) {
	debug.println("RevocationChecker.checkApprovedCRLs()"
	+ " CRL entry: " + entry.toString());
	}

	/*
	* Abort CRL validation and throw exception if there are any
	* unrecognized critical CRL entry extensions (see section
	* 5.3 of RFC 5280).
	*/
	Set<String> unresCritExts = entry.getCriticalExtensionOIDs();
	if (unresCritExts != null && !unresCritExts.isEmpty()) {
	/* remove any that we will process */
	unresCritExts.remove(ReasonCode_Id.toString());
	unresCritExts.remove(CertificateIssuer_Id.toString());
	if (!unresCritExts.isEmpty()) {
	throw new CertPathValidatorException(
	"Unrecognized critical extension(s) in revoked " +
	"CRL entry");
	}
	}

	reasonCode = entry.getRevocationReason();
	if (reasonCode == null) {
	reasonCode = CRLReason.UNSPECIFIED;
	}
	Date revocationDate = entry.getRevocationDate();
	if (revocationDate.before(params.date())) {
	Throwable t = new CertificateRevokedException(
	revocationDate, reasonCode,
	crl.getIssuerX500Principal(), entry.getExtensions());
	throw new CertPathValidatorException(
	t.getMessage(), t, null, -1, BasicReason.REVOKED);
	}
	}
	}
	}

	private void checkOCSP(X509Certificate cert,
	Collection<String> unresolvedCritExts)
	throws CertPathValidatorException
	{
	X509CertImpl currCert = null;
	try {
	currCert = X509CertImpl.toImpl(cert);
	} catch (CertificateException ce) {
	throw new CertPathValidatorException(ce);
	}

	// The algorithm constraints of the OCSP trusted responder certificate
	// does not need to be checked in this code. The constraints will be
	// checked when the responder's certificate is validated.

	OCSPResponse response = null;
	CertId certId = null;
	try {
	certId = new CertId(issuerInfo.getName(), issuerInfo.getPublicKey(),
	currCert.getSerialNumberObject());

	// check if there is a cached OCSP response available
	byte[] responseBytes = ocspResponses.get(cert);
	if (responseBytes != null) {
	if (debug != null) {
	debug.println("Found cached OCSP response");
	}
	response = new OCSPResponse(responseBytes);

	// verify the response
	byte[] nonce = null;
	for (Extension ext : ocspExtensions) {
	if (ext.getId().equals("1.3.6.1.5.5.7.48.1.2")) {
	nonce = ext.getValue();
	}
	}
	response.verify(Collections.singletonList(certId), issuerInfo,
	responderCert, params.date(), nonce, params.variant());

	} else {
	URI responderURI = (this.responderURI != null)
	? this.responderURI
	: OCSP.getResponderURI(currCert);
	if (responderURI == null) {
	throw new CertPathValidatorException(
	"Certificate does not specify OCSP responder", null,
	null, -1);
	}

	response = OCSP.check(Collections.singletonList(certId),
	responderURI, issuerInfo, responderCert, null,
	ocspExtensions, params.variant());
	}
	} catch (IOException e) {
	throw new CertPathValidatorException(
	"Unable to determine revocation status due to network error",
	e, null, -1, BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}

	RevocationStatus rs =
	(RevocationStatus)response.getSingleResponse(certId);
	RevocationStatus.CertStatus certStatus = rs.getCertStatus();
	if (certStatus == RevocationStatus.CertStatus.REVOKED) {
	Date revocationTime = rs.getRevocationTime();
	if (revocationTime.before(params.date())) {
	Throwable t = new CertificateRevokedException(
	revocationTime, rs.getRevocationReason(),
	response.getSignerCertificate().getSubjectX500Principal(),
	rs.getSingleExtensions());
	throw new CertPathValidatorException(t.getMessage(), t, null,
	-1, BasicReason.REVOKED);
	}
	} else if (certStatus == RevocationStatus.CertStatus.UNKNOWN) {
	throw new CertPathValidatorException(
	"Certificate's revocation status is unknown", null,
	params.certPath(), -1,
	BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}
	}

	/*
	* Removes any non-hexadecimal characters from a string.
	*/
	private static final String HEX_DIGITS = "0123456789ABCDEFabcdef";
	private static String stripOutSeparators(String value) {
	char[] chars = value.toCharArray();
	StringBuilder hexNumber = new StringBuilder();
	for (int i = 0; i < chars.length; i++) {
	if (HEX_DIGITS.indexOf(chars[i]) != -1) {
	hexNumber.append(chars[i]);
	}
	}
	return hexNumber.toString();
	}

	/**
	* Checks that a cert can be used to verify a CRL.
	*
	* @param cert an X509Certificate to check
	* @return a boolean specifying if the cert is allowed to vouch for the
	* validity of a CRL
	*/
	static boolean certCanSignCrl(X509Certificate cert) {
	// if the cert doesn't include the key usage ext, or
	// the key usage ext asserts cRLSigning, return true,
	// otherwise return false.
	boolean[] keyUsage = cert.getKeyUsage();
	if (keyUsage != null) {
	return keyUsage[6];
	}
	return false;
	}

	/**
	* Internal method that verifies a set of possible_crls,
	* and sees if each is approved, based on the cert.
	*
	* @param crls a set of possible CRLs to test for acceptability
	* @param cert the certificate whose revocation status is being checked
	* @param signFlag <code>true</code> if prevKey was trusted to sign CRLs
	* @param prevKey the public key of the issuer of cert
	* @param reasonsMask the reason code mask
	* @param trustAnchors a <code>Set</code> of <code>TrustAnchor</code>s>
	* @return a collection of approved crls (or an empty collection)
	*/
	private static final boolean[] ALL_REASONS =
	{true, true, true, true, true, true, true, true, true};
	private Collection<X509CRL> verifyPossibleCRLs(Set<X509CRL> crls,
	X509Certificate cert,
	PublicKey prevKey,
	boolean signFlag,
	boolean[] reasonsMask,
	Set<TrustAnchor> anchors)
	throws CertPathValidatorException
	{
	try {
	X509CertImpl certImpl = X509CertImpl.toImpl(cert);
	if (debug != null) {
	debug.println("RevocationChecker.verifyPossibleCRLs: " +
	"Checking CRLDPs for "
	+ certImpl.getSubjectX500Principal());
	}
	CRLDistributionPointsExtension ext =
	certImpl.getCRLDistributionPointsExtension();
	List<DistributionPoint> points = null;
	if (ext == null) {
	// assume a DP with reasons and CRLIssuer fields omitted
	// and a DP name of the cert issuer.
	// TODO add issuerAltName too
	X500Name certIssuer = (X500Name)certImpl.getIssuerDN();
	DistributionPoint point = new DistributionPoint(
	new GeneralNames().add(new GeneralName(certIssuer)),
	null, null);
	points = Collections.singletonList(point);
	} else {
	points = ext.get(CRLDistributionPointsExtension.POINTS);
	}
	Set<X509CRL> results = new HashSet<>();
	for (DistributionPoint point : points) {
	for (X509CRL crl : crls) {
	if (DistributionPointFetcher.verifyCRL(
	certImpl, point, crl, reasonsMask, signFlag,
	prevKey, null, params.sigProvider(), anchors,
	certStores, params.date(), params.variant(), anchor))
	{
	results.add(crl);
	}
	}
	if (Arrays.equals(reasonsMask, ALL_REASONS))
	break;
	}
	return results;
	} catch (CertificateException \| CRLException \| IOException e) {
	if (debug != null) {
	debug.println("Exception while verifying CRL: "+e.getMessage());
	e.printStackTrace();
	}
	return Collections.emptySet();
	}
	}

	/**
	* We have a cert whose revocation status couldn't be verified by
	* a CRL issued by the cert that issued the CRL. See if we can
	* find a valid CRL issued by a separate key that can verify the
	* revocation status of this certificate.
	* <p>
	* Note that this does not provide support for indirect CRLs,
	* only CRLs signed with a different key (but the same issuer
	* name) as the certificate being checked.
	*
	* @param currCert the <code>X509Certificate</code> to be checked
	* @param prevKey the <code>PublicKey</code> that failed
	* @param signFlag <code>true</code> if that key was trusted to sign CRLs
	* @param stackedCerts a <code>Set</code> of <code>X509Certificate</code>s>
	* whose revocation status depends on the
	* non-revoked status of this cert. To avoid
	* circular dependencies, we assume they're
	* revoked while checking the revocation
	* status of this cert.
	* @throws CertPathValidatorException if the cert's revocation status
	* cannot be verified successfully with another key
	*/
	private void verifyWithSeparateSigningKey(X509Certificate cert,
	PublicKey prevKey,
	boolean signFlag,
	Set<X509Certificate> stackedCerts)
	throws CertPathValidatorException
	{
	String msg = "revocation status";
	if (debug != null) {
	debug.println(
	"RevocationChecker.verifyWithSeparateSigningKey()" +
	" ---checking " + msg + "...");
	}

	// Reject circular dependencies - RFC 5280 is not explicit on how
	// to handle this, but does suggest that they can be a security
	// risk and can create unresolvable dependencies
	if ((stackedCerts != null) && stackedCerts.contains(cert)) {
	if (debug != null) {
	debug.println(
	"RevocationChecker.verifyWithSeparateSigningKey()" +
	" circular dependency");
	}
	throw new CertPathValidatorException
	("Could not determine revocation status", null, null, -1,
	BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}

	// Try to find another key that might be able to sign
	// CRLs vouching for this cert.
	// If prevKey wasn't trusted, maybe we just didn't have the right
	// path to it. Don't rule that key out.
	if (!signFlag) {
	buildToNewKey(cert, null, stackedCerts);
	} else {
	buildToNewKey(cert, prevKey, stackedCerts);
	}
	}

	/**
	* Tries to find a CertPath that establishes a key that can be
	* used to verify the revocation status of a given certificate.
	* Ignores keys that have previously been tried. Throws a
	* CertPathValidatorException if no such key could be found.
	*
	* @param currCert the <code>X509Certificate</code> to be checked
	* @param prevKey the <code>PublicKey</code> of the certificate whose key
	* cannot be used to vouch for the CRL and should be ignored
	* @param stackedCerts a <code>Set</code> of <code>X509Certificate</code>s>
	* whose revocation status depends on the
	* establishment of this path.
	* @throws CertPathValidatorException on failure
	*/
	private static final boolean [] CRL_SIGN_USAGE =
	{ false, false, false, false, false, false, true };
	private void buildToNewKey(X509Certificate currCert,
	PublicKey prevKey,
	Set<X509Certificate> stackedCerts)
	throws CertPathValidatorException
	{

	if (debug != null) {
	debug.println("RevocationChecker.buildToNewKey()" +
	" starting work");
	}
	Set<PublicKey> badKeys = new HashSet<>();
	if (prevKey != null) {
	badKeys.add(prevKey);
	}
	X509CertSelector certSel = new RejectKeySelector(badKeys);
	certSel.setSubject(currCert.getIssuerX500Principal());
	certSel.setKeyUsage(CRL_SIGN_USAGE);

	Set<TrustAnchor> newAnchors = anchor == null ?
	params.trustAnchors() :
	Collections.singleton(anchor);

	PKIXBuilderParameters builderParams;
	try {
	builderParams = new PKIXBuilderParameters(newAnchors, certSel);
	} catch (InvalidAlgorithmParameterException iape) {
	throw new RuntimeException(iape); // should never occur
	}
	builderParams.setInitialPolicies(params.initialPolicies());
	builderParams.setCertStores(certStores);
	builderParams.setExplicitPolicyRequired
	(params.explicitPolicyRequired());
	builderParams.setPolicyMappingInhibited
	(params.policyMappingInhibited());
	builderParams.setAnyPolicyInhibited(params.anyPolicyInhibited());
	// Policy qualifiers must be rejected, since we don't have
	// any way to convey them back to the application.
	// That's the default, so no need to write code.
	builderParams.setDate(params.date());
	builderParams.setCertPathCheckers(params.certPathCheckers());
	builderParams.setSigProvider(params.sigProvider());

	// Skip revocation during this build to detect circular
	// references. But check revocation afterwards, using the
	// key (or any other that works).
	builderParams.setRevocationEnabled(false);

	// check for AuthorityInformationAccess extension
	if (Builder.USE_AIA == true) {
	X509CertImpl currCertImpl = null;
	try {
	currCertImpl = X509CertImpl.toImpl(currCert);
	} catch (CertificateException ce) {
	// ignore but log it
	if (debug != null) {
	debug.println("RevocationChecker.buildToNewKey: " +
	"error decoding cert: " + ce);
	}
	}
	AuthorityInfoAccessExtension aiaExt = null;
	if (currCertImpl != null) {
	aiaExt = currCertImpl.getAuthorityInfoAccessExtension();
	}
	if (aiaExt != null) {
	List<AccessDescription> adList = aiaExt.getAccessDescriptions();
	if (adList != null) {
	for (AccessDescription ad : adList) {
	CertStore cs = URICertStore.getInstance(ad);
	if (cs != null) {
	if (debug != null) {
	debug.println("adding AIAext CertStore");
	}
	builderParams.addCertStore(cs);
	}
	}
	}
	}
	}

	CertPathBuilder builder = null;
	try {
	builder = CertPathBuilder.getInstance("PKIX");
	} catch (NoSuchAlgorithmException nsae) {
	throw new CertPathValidatorException(nsae);
	}
	while (true) {
	try {
	if (debug != null) {
	debug.println("RevocationChecker.buildToNewKey()" +
	" about to try build ...");
	}
	PKIXCertPathBuilderResult cpbr =
	(PKIXCertPathBuilderResult)builder.build(builderParams);

	if (debug != null) {
	debug.println("RevocationChecker.buildToNewKey()" +
	" about to check revocation ...");
	}
	// Now check revocation of all certs in path, assuming that
	// the stackedCerts are revoked.
	if (stackedCerts == null) {
	stackedCerts = new HashSet<X509Certificate>();
	}
	stackedCerts.add(currCert);
	TrustAnchor ta = cpbr.getTrustAnchor();
	PublicKey prevKey2 = ta.getCAPublicKey();
	if (prevKey2 == null) {
	prevKey2 = ta.getTrustedCert().getPublicKey();
	}
	boolean signFlag = true;
	List<? extends Certificate> cpList =
	cpbr.getCertPath().getCertificates();
	try {
	for (int i = cpList.size() - 1; i >= 0; i--) {
	X509Certificate cert = (X509Certificate) cpList.get(i);

	if (debug != null) {
	debug.println("RevocationChecker.buildToNewKey()"
	+ " index " + i + " checking "
	+ cert);
	}
	checkCRLs(cert, prevKey2, null, signFlag, true,
	stackedCerts, newAnchors);
	signFlag = certCanSignCrl(cert);
	prevKey2 = cert.getPublicKey();
	}
	} catch (CertPathValidatorException cpve) {
	// ignore it and try to get another key
	badKeys.add(cpbr.getPublicKey());
	continue;
	}

	if (debug != null) {
	debug.println("RevocationChecker.buildToNewKey()" +
	" got key " + cpbr.getPublicKey());
	}
	// Now check revocation on the current cert using that key and
	// the corresponding certificate.
	// If it doesn't check out, try to find a different key.
	// And if we can't find a key, then return false.
	PublicKey newKey = cpbr.getPublicKey();
	X509Certificate newCert = cpList.isEmpty() ?
	null : (X509Certificate) cpList.get(0);
	try {
	checkCRLs(currCert, newKey, newCert,
	true, false, null, params.trustAnchors());
	// If that passed, the cert is OK!
	return;
	} catch (CertPathValidatorException cpve) {
	// If it is revoked, rethrow exception
	if (cpve.getReason() == BasicReason.REVOKED) {
	throw cpve;
	}
	// Otherwise, ignore the exception and
	// try to get another key.
	}
	badKeys.add(newKey);
	} catch (InvalidAlgorithmParameterException iape) {
	throw new CertPathValidatorException(iape);
	} catch (CertPathBuilderException cpbe) {
	throw new CertPathValidatorException
	("Could not determine revocation status", null, null,
	-1, BasicReason.UNDETERMINED_REVOCATION_STATUS);
	}
	}
	}

	/*
	* This inner class extends the X509CertSelector to add an additional
	* check to make sure the subject public key isn't on a particular list.
	* This class is used by buildToNewKey() to make sure the builder doesn't
	* end up with a CertPath to a public key that has already been rejected.
	*/
	private static class RejectKeySelector extends X509CertSelector {
	private final Set<PublicKey> badKeySet;

	/**
	* Creates a new <code>RejectKeySelector</code>.
	*
	* @param badPublicKeys a <code>Set</code> of
	* <code>PublicKey</code>s that
	* should be rejected (or <code>null</code>
	* if no such check should be done)
	*/
	RejectKeySelector(Set<PublicKey> badPublicKeys) {
	this.badKeySet = badPublicKeys;
	}

	/**
	* Decides whether a <code>Certificate</code> should be selected.
	*
	* @param cert the <code>Certificate</code> to be checked
	* @return <code>true</code> if the <code>Certificate</code> should be
	* selected, <code>false</code> otherwise
	*/
	@Override
	public boolean match(Certificate cert) {
	if (!super.match(cert))
	return(false);

	if (badKeySet.contains(cert.getPublicKey())) {
	if (debug != null)
	debug.println("RejectKeySelector.match: bad key");
	return false;
	}

	if (debug != null)
	debug.println("RejectKeySelector.match: returning true");
	return true;
	}

	/**
	* Return a printable representation of the <code>CertSelector</code>.
	*
	* @return a <code>String</code> describing the contents of the
	* <code>CertSelector</code>
	*/
	@Override
	public String toString() {
	StringBuilder sb = new StringBuilder();
	sb.append("RejectKeySelector: [\n");
	sb.append(super.toString());
	sb.append(badKeySet);
	sb.append("]");
	return sb.toString();
	}
	}
	}

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