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// Copyright 2017 Google LLC
//
// 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 com.google.crypto.tink.mac;
import com.google.crypto.tink.Key;
import com.google.crypto.tink.Mac;
import com.google.crypto.tink.internal.KeysetHandleInterface;
import com.google.crypto.tink.internal.LegacyProtoKey;
import com.google.crypto.tink.internal.MonitoringClient;
import com.google.crypto.tink.internal.MonitoringUtil;
import com.google.crypto.tink.internal.MutableMonitoringRegistry;
import com.google.crypto.tink.internal.MutablePrimitiveRegistry;
import com.google.crypto.tink.internal.PrefixMap;
import com.google.crypto.tink.internal.PrimitiveConstructor;
import com.google.crypto.tink.internal.PrimitiveRegistry;
import com.google.crypto.tink.internal.PrimitiveSet;
import com.google.crypto.tink.internal.PrimitiveWrapper;
import com.google.crypto.tink.mac.internal.LegacyFullMac;
import com.google.crypto.tink.util.Bytes;
import java.security.GeneralSecurityException;
/**
* MacWrapper is the implementation of PrimitiveWrapper for the Mac primitive.
*
* The returned primitive works with a keyset (rather than a single key). To compute a MAC tag,
* it uses the primary key in the keyset, and prepends to the tag a certain prefix associated with
* the primary key. To verify a tag, the primitive uses the prefix of the tag to efficiently select
* the right key in the set. If the keys associated with the prefix do not validate the tag, the
* primitive tries all keys with {@link com.google.crypto.tink.proto.OutputPrefixType#RAW}.
*/
public class MacWrapper implements PrimitiveWrapper {
private static class MacWithId {
public MacWithId(Mac mac, int id) {
this.mac = mac;
this.id = id;
}
public final Mac mac;
public final int id;
}
private static final MacWrapper WRAPPER = new MacWrapper();
private static final PrimitiveConstructor
LEGACY_FULL_MAC_PRIMITIVE_CONSTRUCTOR =
PrimitiveConstructor.create(LegacyFullMac::create, LegacyProtoKey.class, Mac.class);
private static Bytes getOutputPrefix(Key key) throws GeneralSecurityException {
if (key instanceof MacKey) {
return ((MacKey) key).getOutputPrefix();
}
if (key instanceof LegacyProtoKey) {
return ((LegacyProtoKey) key).getOutputPrefix();
}
throw new GeneralSecurityException(
"Cannot get output prefix for key of class "
+ key.getClass().getName()
+ " with parameters "
+ key.getParameters());
}
private static class WrappedMac implements Mac {
private final MacWithId primary;
private final PrefixMap allMacs;
private final MonitoringClient.Logger computeLogger;
private final MonitoringClient.Logger verifyLogger;
private WrappedMac(
MacWithId primary,
PrefixMap allMacs,
MonitoringClient.Logger computeLogger,
MonitoringClient.Logger verifyLogger) {
this.primary = primary;
this.allMacs = allMacs;
this.computeLogger = computeLogger;
this.verifyLogger = verifyLogger;
}
@Override
public byte[] computeMac(final byte[] data) throws GeneralSecurityException {
try {
byte[] output = primary.mac.computeMac(data);
computeLogger.log(primary.id, data.length);
return output;
} catch (GeneralSecurityException e) {
computeLogger.logFailure();
throw e;
}
}
@Override
public void verifyMac(final byte[] mac, final byte[] data) throws GeneralSecurityException {
for (MacWithId macWithId : allMacs.getAllWithMatchingPrefix(mac)) {
try {
macWithId.mac.verifyMac(mac, data);
verifyLogger.log(macWithId.id, data.length);
// If there is no exception, the MAC is valid and we can return.
return;
} catch (GeneralSecurityException e) {
// Ignored as we want to continue verification with the remaining keys.
}
}
verifyLogger.logFailure();
throw new GeneralSecurityException("invalid MAC");
}
}
MacWrapper() {}
@Override
public Mac wrap(final PrimitiveSet primitives) throws GeneralSecurityException {
PrefixMap.Builder builder = new PrefixMap.Builder<>();
KeysetHandleInterface keysetHandle = primitives.getKeysetHandle();
for (int i = 0; i < keysetHandle.size(); i++) {
KeysetHandleInterface.Entry entry = keysetHandle.getAt(i);
Mac mac = primitives.getPrimitiveForEntry(entry);
builder.put(getOutputPrefix(entry.getKey()), new MacWithId(mac, entry.getId()));
}
MonitoringClient.Logger computeLogger;
MonitoringClient.Logger verifyLogger;
if (!primitives.getAnnotations().isEmpty()) {
MonitoringClient client = MutableMonitoringRegistry.globalInstance().getMonitoringClient();
computeLogger =
client.createLogger(keysetHandle, primitives.getAnnotations(), "mac", "compute");
verifyLogger =
client.createLogger(keysetHandle, primitives.getAnnotations(), "mac", "verify");
} else {
computeLogger = MonitoringUtil.DO_NOTHING_LOGGER;
verifyLogger = MonitoringUtil.DO_NOTHING_LOGGER;
}
Mac primaryMac = primitives.getPrimitiveForEntry(keysetHandle.getPrimary());
return new WrappedMac(
new MacWithId(primaryMac, keysetHandle.getPrimary().getId()),
builder.build(),
computeLogger,
verifyLogger);
}
@Override
public Class getPrimitiveClass() {
return Mac.class;
}
@Override
public Class getInputPrimitiveClass() {
return Mac.class;
}
static void register() throws GeneralSecurityException {
MutablePrimitiveRegistry.globalInstance().registerPrimitiveWrapper(WRAPPER);
MutablePrimitiveRegistry.globalInstance()
.registerPrimitiveConstructor(LEGACY_FULL_MAC_PRIMITIVE_CONSTRUCTOR);
}
/**
* registerToInternalPrimitiveRegistry is a non-public method (it takes an argument of an
* internal-only type) registering an instance of {@code MacWrapper} to the provided {@code
* PrimitiveRegistry.Builder}.
*/
public static void registerToInternalPrimitiveRegistry(
PrimitiveRegistry.Builder primitiveRegistryBuilder) throws GeneralSecurityException {
primitiveRegistryBuilder.registerPrimitiveWrapper(WRAPPER);
}
}