com.squareup.okhttp.internal.tls.CertificateChainCleaner Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.squareup.okhttp.internal.tls;
import java.security.GeneralSecurityException;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;
import javax.net.ssl.SSLPeerUnverifiedException;
/**
* Computes the effective certificate chain from the raw array returned by Java's built in TLS APIs.
* Cleaning a chain returns a list of certificates where the first element is {@code chain[0]}, each
* certificate is signed by the certificate that follows, and the last certificate is a trusted CA
* certificate.
*
* Use of the chain cleaner is necessary to omit unexpected certificates that aren't relevant to
* the TLS handshake and to extract the trusted CA certificate for the benefit of certificate
* pinning.
*
*
This class includes code from Conscrypt's {@code
* TrustManagerImpl} and {@code TrustedCertificateIndex}.
*/
public final class CertificateChainCleaner {
/** The maximum number of signers in a chain. We use 9 for consistency with OpenSSL. */
private static final int MAX_SIGNERS = 9;
private final TrustRootIndex trustRootIndex;
public CertificateChainCleaner(TrustRootIndex trustRootIndex) {
this.trustRootIndex = trustRootIndex;
}
/**
* Returns a cleaned chain for {@code chain}.
*
*
This method throws if the complete chain to a trusted CA certificate cannot be constructed.
* This is unexpected unless the trust root index in this class has a different trust manager than
* what was used to establish {@code chain}.
*/
public List clean(List chain) throws SSLPeerUnverifiedException {
Deque queue = new ArrayDeque<>(chain);
List result = new ArrayList<>();
result.add(queue.removeFirst());
boolean foundTrustedCertificate = false;
followIssuerChain:
for (int c = 0; c < MAX_SIGNERS; c++) {
X509Certificate toVerify = (X509Certificate) result.get(result.size() - 1);
// If this cert has been signed by a trusted cert, use that. Add the trusted certificate to
// the end of the chain unless it's already present. (That would happen if the first
// certificate in the chain is itself a self-signed and trusted CA certificate.)
X509Certificate trustedCert = trustRootIndex.findByIssuerAndSignature(toVerify);
if (trustedCert != null) {
if (result.size() > 1 || !toVerify.equals(trustedCert)) {
result.add(trustedCert);
}
if (verifySignature(trustedCert, trustedCert)) {
return result; // The self-signed cert is a root CA. We're done.
}
foundTrustedCertificate = true;
continue;
}
// Search for the certificate in the chain that signed this certificate. This is typically the
// next element in the chain, but it could be any element.
for (Iterator i = queue.iterator(); i.hasNext(); ) {
X509Certificate signingCert = (X509Certificate) i.next();
if (verifySignature(toVerify, signingCert)) {
i.remove();
result.add(signingCert);
continue followIssuerChain;
}
}
// We've reached the end of the chain. If any cert in the chain is trusted, we're done.
if (foundTrustedCertificate) {
return result;
}
// The last link isn't trusted. Fail.
throw new SSLPeerUnverifiedException("Failed to find a trusted cert that signed " + toVerify);
}
throw new SSLPeerUnverifiedException("Certificate chain too long: " + result);
}
/** Returns true if {@code toVerify} was signed by {@code signingCert}'s public key. */
private boolean verifySignature(X509Certificate toVerify, X509Certificate signingCert) {
if (!toVerify.getIssuerDN().equals(signingCert.getSubjectDN())) return false;
try {
toVerify.verify(signingCert.getPublicKey());
return true;
} catch (GeneralSecurityException verifyFailed) {
return false;
}
}
}