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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.aead;
import com.google.crypto.tink.Aead;
import com.google.crypto.tink.Key;
import com.google.crypto.tink.aead.internal.LegacyFullAead;
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.util.Bytes;
import java.security.GeneralSecurityException;
/**
* AeadWrapper is the implementation of SetWrapper for the Aead primitive.
*
* Key rotation works as follows: each ciphertext is prefixed with the keyId. When decrypting, we
* first try all primitives whose keyId starts with the prefix of the ciphertext. If none of these
* succeed, we try the raw primitives. If any succeeds, we return the ciphertext, otherwise we
* simply throw a GeneralSecurityException.
*/
public class AeadWrapper implements PrimitiveWrapper {
private static class AeadWithId {
public AeadWithId(Aead aead, int id) {
this.aead = aead;
this.id = id;
}
public final Aead aead;
public final int id;
}
private static final AeadWrapper WRAPPER = new AeadWrapper();
private static final PrimitiveConstructor
LEGACY_FULL_AEAD_PRIMITIVE_CONSTRUCTOR =
PrimitiveConstructor.create(LegacyFullAead::create, LegacyProtoKey.class, Aead.class);
private static Bytes getOutputPrefix(Key key) throws GeneralSecurityException {
if (key instanceof AeadKey) {
return ((AeadKey) 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 WrappedAead implements Aead {
private final AeadWithId primary;
private final PrefixMap allAeads;
private final MonitoringClient.Logger encLogger;
private final MonitoringClient.Logger decLogger;
private WrappedAead(
AeadWithId primary,
PrefixMap allAeads,
MonitoringClient.Logger encLogger,
MonitoringClient.Logger decLogger) {
this.primary = primary;
this.allAeads = allAeads;
this.encLogger = encLogger;
this.decLogger = decLogger;
}
@Override
public byte[] encrypt(final byte[] plaintext, final byte[] associatedData)
throws GeneralSecurityException {
try {
byte[] result = primary.aead.encrypt(plaintext, associatedData);
encLogger.log(primary.id, plaintext.length);
return result;
} catch (GeneralSecurityException e) {
encLogger.logFailure();
throw e;
}
}
@Override
public byte[] decrypt(final byte[] ciphertext, final byte[] associatedData)
throws GeneralSecurityException {
for (AeadWithId aeadWithId : allAeads.getAllWithMatchingPrefix(ciphertext)) {
try {
byte[] result = aeadWithId.aead.decrypt(ciphertext, associatedData);
decLogger.log(aeadWithId.id, ciphertext.length);
return result;
} catch (GeneralSecurityException ignored) {
// ignore and continue trying
}
}
decLogger.logFailure();
// nothing works.
throw new GeneralSecurityException("decryption failed");
}
}
AeadWrapper() {}
@Override
public Aead wrap(final PrimitiveSet pset) throws GeneralSecurityException {
PrefixMap.Builder builder = new PrefixMap.Builder<>();
KeysetHandleInterface keysetHandle = pset.getKeysetHandle();
for (int i = 0; i < keysetHandle.size(); i++) {
KeysetHandleInterface.Entry entry = keysetHandle.getAt(i);
builder.put(
getOutputPrefix(entry.getKey()),
new AeadWithId(pset.getPrimitiveForEntry(entry), entry.getId()));
}
MonitoringClient.Logger encLogger;
MonitoringClient.Logger decLogger;
if (!pset.getAnnotations().isEmpty()) {
MonitoringClient client = MutableMonitoringRegistry.globalInstance().getMonitoringClient();
encLogger = client.createLogger(keysetHandle, pset.getAnnotations(), "aead", "encrypt");
decLogger = client.createLogger(keysetHandle, pset.getAnnotations(), "aead", "decrypt");
} else {
encLogger = MonitoringUtil.DO_NOTHING_LOGGER;
decLogger = MonitoringUtil.DO_NOTHING_LOGGER;
}
return new WrappedAead(
new AeadWithId(
pset.getPrimitiveForEntry(keysetHandle.getPrimary()),
keysetHandle.getPrimary().getId()),
builder.build(),
encLogger,
decLogger);
}
@Override
public Class getPrimitiveClass() {
return Aead.class;
}
@Override
public Class getInputPrimitiveClass() {
return Aead.class;
}
public static void register() throws GeneralSecurityException {
MutablePrimitiveRegistry.globalInstance().registerPrimitiveWrapper(WRAPPER);
MutablePrimitiveRegistry.globalInstance()
.registerPrimitiveConstructor(LEGACY_FULL_AEAD_PRIMITIVE_CONSTRUCTOR);
}
/**
* registerToInternalPrimitiveRegistry is a non-public method (it takes an argument of an
* internal-only type) registering an instance of {@code AeadWrapper} to the provided {@code
* PrimitiveRegistry.Builder}.
*/
public static void registerToInternalPrimitiveRegistry(
PrimitiveRegistry.Builder primitiveRegistryBuilder) throws GeneralSecurityException {
primitiveRegistryBuilder.registerPrimitiveWrapper(WRAPPER);
}
}