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/*
* Copyright (C) 2015 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.ct;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.conscrypt.Internal;
import org.conscrypt.NativeCrypto;
import org.conscrypt.OpenSSLX509Certificate;
/**
* @hide
*/
@Internal
public class CTVerifier {
private final CTLogStore store;
public CTVerifier(CTLogStore store) {
this.store = store;
}
public CTVerificationResult verifySignedCertificateTimestamps(List chain,
byte[] tlsData, byte[] ocspData) throws CertificateEncodingException {
OpenSSLX509Certificate[] certs = new OpenSSLX509Certificate[chain.size()];
int i = 0;
for(X509Certificate cert : chain) {
certs[i++] = OpenSSLX509Certificate.fromCertificate(cert);
}
return verifySignedCertificateTimestamps(certs, tlsData, ocspData);
}
/**
* Verify a certificate chain for transparency.
* Signed timestamps are extracted from the leaf certificate, TLS extension, and stapled ocsp
* response, and verified against the list of known logs.
* @throws IllegalArgumentException if the chain is empty
*/
public CTVerificationResult verifySignedCertificateTimestamps(OpenSSLX509Certificate[] chain,
byte[] tlsData, byte[] ocspData) throws CertificateEncodingException {
if (chain.length == 0) {
throw new IllegalArgumentException("Chain of certificates mustn't be empty.");
}
OpenSSLX509Certificate leaf = chain[0];
CTVerificationResult result = new CTVerificationResult();
List tlsScts = getSCTsFromTLSExtension(tlsData);
verifyExternalSCTs(tlsScts, leaf, result);
List ocspScts = getSCTsFromOCSPResponse(ocspData, chain);
verifyExternalSCTs(ocspScts, leaf, result);
List embeddedScts = getSCTsFromX509Extension(chain[0]);
verifyEmbeddedSCTs(embeddedScts, chain, result);
return result;
}
/**
* Verify a list of SCTs which were embedded from an X509 certificate.
* The result of the verification for each sct is added to {@code result}.
*/
private void verifyEmbeddedSCTs(List scts,
OpenSSLX509Certificate[] chain,
CTVerificationResult result) {
// Avoid creating the cert entry if we don't need it
if (scts.isEmpty()) {
return;
}
CertificateEntry precertEntry = null;
if (chain.length >= 2) {
OpenSSLX509Certificate leaf = chain[0];
OpenSSLX509Certificate issuer = chain[1];
try {
precertEntry = CertificateEntry.createForPrecertificate(leaf, issuer);
} catch (CertificateException e) {
// Leave precertEntry as null, we handle it just below
}
}
if (precertEntry == null) {
markSCTsAsInvalid(scts, result);
return;
}
for (SignedCertificateTimestamp sct: scts) {
VerifiedSCT.Status status = verifySingleSCT(sct, precertEntry);
result.add(new VerifiedSCT(sct, status));
}
}
/**
* Verify a list of SCTs which were not embedded in an X509 certificate, that is received
* through the TLS or OCSP extensions.
* The result of the verification for each sct is added to {@code result}.
*/
private void verifyExternalSCTs(List scts,
OpenSSLX509Certificate leaf,
CTVerificationResult result) {
// Avoid creating the cert entry if we don't need it
if (scts.isEmpty()) {
return;
}
CertificateEntry x509Entry;
try {
x509Entry = CertificateEntry.createForX509Certificate(leaf);
} catch (CertificateException e) {
markSCTsAsInvalid(scts, result);
return;
}
for (SignedCertificateTimestamp sct: scts) {
VerifiedSCT.Status status = verifySingleSCT(sct, x509Entry);
result.add(new VerifiedSCT(sct, status));
}
}
/**
* Verify a single SCT for the given Certificate Entry
*/
private VerifiedSCT.Status verifySingleSCT(SignedCertificateTimestamp sct,
CertificateEntry certEntry) {
CTLogInfo log = store.getKnownLog(sct.getLogID());
if (log == null) {
return VerifiedSCT.Status.UNKNOWN_LOG;
}
return log.verifySingleSCT(sct, certEntry);
}
/**
* Add every SCT in {@code scts} to {@code result} with INVALID_SCT as status
*/
private void markSCTsAsInvalid(List scts,
CTVerificationResult result) {
for (SignedCertificateTimestamp sct: scts) {
result.add(new VerifiedSCT(sct, VerifiedSCT.Status.INVALID_SCT));
}
}
/**
* Parse an encoded SignedCertificateTimestampList into a list of SignedCertificateTimestamp
* instances, as described by RFC6962.
* Individual SCTs which fail to be parsed are skipped. If the data is null, or the encompassing
* list fails to be parsed, an empty list is returned.
* @param origin used to create the SignedCertificateTimestamp instances.
*/
private List getSCTsFromSCTList(byte[] data,
SignedCertificateTimestamp.Origin origin) {
if (data == null) {
return Collections.emptyList();
}
byte[][] sctList;
try {
sctList = Serialization.readList(data, CTConstants.SCT_LIST_LENGTH_BYTES,
CTConstants.SERIALIZED_SCT_LENGTH_BYTES);
} catch (SerializationException e) {
return Collections.emptyList();
}
List scts = new ArrayList();
for (byte[] encodedSCT: sctList) {
try {
SignedCertificateTimestamp sct = SignedCertificateTimestamp.decode(encodedSCT, origin);
scts.add(sct);
} catch (SerializationException e) {
// Ignore errors
}
}
return scts;
}
/**
* Extract a list of SignedCertificateTimestamp from a TLS "signed_certificate_timestamp"
* extension as described by RFC6962.
* Individual SCTs which fail to be parsed are skipped. If the data is null, or the encompassing
* list fails to be parsed, an empty list is returned.
* @param data contents of the TLS extension to be decoded
*/
private List getSCTsFromTLSExtension(byte[] data) {
return getSCTsFromSCTList(data, SignedCertificateTimestamp.Origin.TLS_EXTENSION);
}
/**
* Extract a list of SignedCertificateTimestamp contained in an OCSP response.
* If the data is null, or parsing the OCSP response fails, an empty list is returned.
* Individual SCTs which fail to be parsed are skipped.
* @param data contents of the OCSP response
* @param chain certificate chain for which to get SCTs. Must contain at least the leaf and it's
* issuer in order to identify the relevant SingleResponse from the OCSP response,
* or an empty list is returned
*/
private List getSCTsFromOCSPResponse(byte[] data,
OpenSSLX509Certificate[] chain) {
if (data == null || chain.length < 2) {
return Collections.emptyList();
}
byte[] extData = NativeCrypto.get_ocsp_single_extension(data, CTConstants.OCSP_SCT_LIST_OID,
chain[0].getContext(), chain[0],
chain[1].getContext(), chain[1]);
if (extData == null) {
return Collections.emptyList();
}
try {
return getSCTsFromSCTList(
Serialization.readDEROctetString(
Serialization.readDEROctetString(extData)),
SignedCertificateTimestamp.Origin.OCSP_RESPONSE);
} catch (SerializationException e) {
return Collections.emptyList();
}
}
/**
* Extract a list of SignedCertificateTimestamp embedded in an X509 certificate.
*
* If the certificate does not contain any SCT extension, or the encompassing encoded list fails
* to be parsed, an empty list is returned. Individual SCTs which fail to be parsed are ignored.
*/
private List getSCTsFromX509Extension(OpenSSLX509Certificate leaf) {
byte[] extData = leaf.getExtensionValue(CTConstants.X509_SCT_LIST_OID);
if (extData == null) {
return Collections.emptyList();
}
try {
return getSCTsFromSCTList(
Serialization.readDEROctetString(
Serialization.readDEROctetString(extData)),
SignedCertificateTimestamp.Origin.EMBEDDED);
} catch (SerializationException e) {
return Collections.emptyList();
}
}
}
