org.conscrypt.ChainStrengthAnalyzer Maven / Gradle / Ivy
/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed 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 org.conscrypt;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.security.interfaces.DSAPublicKey;
import java.security.interfaces.ECPublicKey;
import java.security.interfaces.RSAPublicKey;
import java.util.List;
/**
* Analyzes the cryptographic strength of a chain of X.509 certificates.
*/
@Internal
public final class ChainStrengthAnalyzer {
private static final int MIN_RSA_MODULUS_LEN_BITS = 1024;
private static final int MIN_EC_FIELD_SIZE_BITS = 160;
private static final int MIN_DSA_P_LEN_BITS = 1024;
private static final int MIN_DSA_Q_LEN_BITS = 160;
private static final String[] SIGNATURE_ALGORITHM_OID_BLACKLIST = {
"1.2.840.113549.1.1.2", // md2WithRSAEncryption
"1.2.840.113549.1.1.3", // md4WithRSAEncryption
"1.2.840.113549.1.1.4", // md5WithRSAEncryption
"1.2.840.113549.1.1.5", // sha1WithRSAEncryption
"1.2.840.10040.4.3", //dsa-with-sha1
"1.2.840.10045.4.1", //ecdsa-with-sha1
};
public static final void check(X509Certificate[] chain) throws CertificateException {
for (X509Certificate cert : chain) {
try {
checkCert(cert);
} catch (CertificateException e) {
throw new CertificateException("Unacceptable certificate: "
+ cert.getSubjectX500Principal(), e);
}
}
}
public static final void check(List chain) throws CertificateException {
for (X509Certificate cert : chain) {
try {
checkCert(cert);
} catch (CertificateException e) {
throw new CertificateException("Unacceptable certificate: "
+ cert.getSubjectX500Principal(), e);
}
}
}
public static final void checkCert(X509Certificate cert) throws CertificateException {
checkKeyLength(cert);
checkSignatureAlgorithm(cert);
}
private static void checkKeyLength(X509Certificate cert) throws CertificateException {
Object pubkey = cert.getPublicKey();
if (pubkey instanceof RSAPublicKey) {
int modulusLength = ((RSAPublicKey) pubkey).getModulus().bitLength();
if (modulusLength < MIN_RSA_MODULUS_LEN_BITS) {
throw new CertificateException(
"RSA modulus is < " + MIN_RSA_MODULUS_LEN_BITS + " bits");
}
} else if (pubkey instanceof ECPublicKey) {
int fieldSizeBits =
((ECPublicKey) pubkey).getParams().getCurve().getField().getFieldSize();
if (fieldSizeBits < MIN_EC_FIELD_SIZE_BITS) {
throw new CertificateException(
"EC key field size is < " + MIN_EC_FIELD_SIZE_BITS + " bits");
}
} else if (pubkey instanceof DSAPublicKey) {
int pLength = ((DSAPublicKey) pubkey).getParams().getP().bitLength();
int qLength = ((DSAPublicKey) pubkey).getParams().getQ().bitLength();
if ((pLength < MIN_DSA_P_LEN_BITS) || (qLength < MIN_DSA_Q_LEN_BITS)) {
throw new CertificateException(
"DSA key length is < (" + MIN_DSA_P_LEN_BITS + ", " + MIN_DSA_Q_LEN_BITS
+ ") bits");
}
} else {
// Unknown keys will be of type X509PublicKey.
throw new CertificateException("Rejecting unknown key class " + pubkey.getClass().getName());
}
}
private static void checkSignatureAlgorithm(
X509Certificate cert) throws CertificateException {
String oid = cert.getSigAlgOID();
for (String blacklisted : SIGNATURE_ALGORITHM_OID_BLACKLIST) {
if (oid.equals(blacklisted)) {
throw new CertificateException("Signature uses an insecure hash function: " + oid);
}
}
}
}