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/*
This file is part of the iText (R) project.
Copyright (c) 1998-2023 Apryse Group NV
Authors: Apryse Software.
This program is offered under a commercial and under the AGPL license.
For commercial licensing, contact us at https://itextpdf.com/sales. For AGPL licensing, see below.
AGPL licensing:
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see .
*/
package com.itextpdf.signatures;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.net.URL;
import java.security.GeneralSecurityException;
import java.security.cert.X509CRL;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
/**
* Class that allows you to verify a certificate against
* one or more Certificate Revocation Lists.
*/
public class CRLVerifier extends RootStoreVerifier {
/** The Logger instance */
protected static final Logger LOGGER = LoggerFactory.getLogger(CRLVerifier.class);
/** The list of CRLs to check for revocation date. */
List crls;
/**
* Creates a CRLVerifier instance.
* @param verifier the next verifier in the chain
* @param crls a list of CRLs
*/
public CRLVerifier(CertificateVerifier verifier, List crls) {
super(verifier);
this.crls = crls;
}
/**
* Verifies if a a valid CRL is found for the certificate.
* If this method returns false, it doesn't mean the certificate isn't valid.
* It means we couldn't verify it against any CRL that was available.
* @param signCert the certificate that needs to be checked
* @param issuerCert its issuer
* @return a list of VerificationOK objects.
* The list will be empty if the certificate couldn't be verified.
* @see com.itextpdf.signatures.RootStoreVerifier#verify(java.security.cert.X509Certificate,
* java.security.cert.X509Certificate, java.util.Date)
*/
public List verify(X509Certificate signCert, X509Certificate issuerCert, Date signDate)
throws GeneralSecurityException {
List result = new ArrayList<>();
int validCrlsFound = 0;
// first check the list of CRLs that is provided
if (crls != null) {
for (X509CRL crl : crls) {
if (verify(crl, signCert, issuerCert, signDate)) {
validCrlsFound++;
}
}
}
// then check online if allowed
boolean online = false;
if (onlineCheckingAllowed && validCrlsFound == 0) {
if (verify(getCRL(signCert, issuerCert), signCert, issuerCert, signDate)) {
validCrlsFound++;
online = true;
}
}
// show how many valid CRLs were found
LOGGER.info("Valid CRLs found: " + validCrlsFound);
if (validCrlsFound > 0) {
result.add(new VerificationOK(signCert, this.getClass(),
"Valid CRLs found: " + validCrlsFound + (online ? " (online)" : "")));
}
if (verifier != null) {
result.addAll(verifier.verify(signCert, issuerCert, signDate));
}
// verify using the previous verifier in the chain (if any)
return result;
}
/**
* Verifies a certificate against a single CRL.
* @param crl the Certificate Revocation List
* @param signCert a certificate that needs to be verified
* @param issuerCert its issuer
* @param signDate the sign date
* @return true if the verification succeeded
* @throws GeneralSecurityException thrown when certificate has been revoked
*/
public boolean verify(X509CRL crl, X509Certificate signCert, X509Certificate issuerCert, Date signDate)
throws GeneralSecurityException {
if (crl == null || signDate == TimestampConstants.UNDEFINED_TIMESTAMP_DATE) {
return false;
}
// We only check CRLs valid on the signing date for which the issuer matches
if (crl.getIssuerX500Principal().equals(signCert.getIssuerX500Principal())
&& signDate.before(crl.getNextUpdate())) {
// the signing certificate may not be revoked
if (isSignatureValid(crl, issuerCert) && crl.isRevoked(signCert)) {
throw new VerificationException(signCert, "The certificate has been revoked.");
}
return true;
}
return false;
}
/**
* Fetches a CRL for a specific certificate online (without further checking).
* @param signCert the certificate
* @param issuerCert its issuer
* @return an X509CRL object
*/
public X509CRL getCRL(X509Certificate signCert, X509Certificate issuerCert) {
if (issuerCert == null) {
issuerCert = signCert;
}
try {
// gets the URL from the certificate
String crlurl = CertificateUtil.getCRLURL(signCert);
if (crlurl == null) {
return null;
}
LOGGER.info("Getting CRL from " + crlurl);
return (X509CRL) SignUtils.parseCrlFromStream(new URL(crlurl).openStream());
} catch (IOException | GeneralSecurityException e) {
return null;
}
}
/**
* Checks if a CRL verifies against the issuer certificate or a trusted anchor.
* @param crl the CRL
* @param crlIssuer the trusted anchor
* @return true if the CRL can be trusted
*/
public boolean isSignatureValid(X509CRL crl, X509Certificate crlIssuer) {
// check if the CRL was issued by the issuer
if (crlIssuer != null) {
try {
crl.verify(crlIssuer.getPublicKey());
return true;
} catch (GeneralSecurityException e) {
LOGGER.warn("CRL not issued by the same authority as the certificate that is being checked");
}
}
// check the CRL against trusted anchors
if (rootStore == null)
return false;
try {
// loop over the certificate in the key store
for (X509Certificate anchor : SignUtils.getCertificates(rootStore)) {
try {
// check if the crl was signed by a trusted party (indirect CRLs)
crl.verify(anchor.getPublicKey());
return true;
} catch (GeneralSecurityException e) {
// do nothing and continue
}
}
}
catch (GeneralSecurityException e) {
// do nothing and return false at the end
}
return false;
}
}
