| // Copyright 2017 Google Inc. |
| // |
| // 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.KeyManagerBase; |
| import com.google.crypto.tink.Mac; |
| import com.google.crypto.tink.proto.HashType; |
| import com.google.crypto.tink.proto.HmacKey; |
| import com.google.crypto.tink.proto.HmacKeyFormat; |
| import com.google.crypto.tink.proto.HmacParams; |
| import com.google.crypto.tink.proto.KeyData.KeyMaterialType; |
| import com.google.crypto.tink.subtle.MacJce; |
| import com.google.crypto.tink.subtle.Random; |
| import com.google.crypto.tink.subtle.Validators; |
| import com.google.protobuf.ByteString; |
| import com.google.protobuf.InvalidProtocolBufferException; |
| import java.security.GeneralSecurityException; |
| import javax.crypto.spec.SecretKeySpec; |
| |
| /** |
| * This key manager generates new {@code HmacKey} keys and produces new instances of {@code MacJce}. |
| */ |
| class HmacKeyManager extends KeyManagerBase<Mac, HmacKey, HmacKeyFormat> { |
| public HmacKeyManager() { |
| super(Mac.class, HmacKey.class, HmacKeyFormat.class, TYPE_URL); |
| } |
| /** Type url that this manager does support. */ |
| public static final String TYPE_URL = "type.googleapis.com/google.crypto.tink.HmacKey"; |
| /** Current version of this key manager. Keys with version equal or smaller are supported. */ |
| private static final int VERSION = 0; |
| |
| /** Minimum key size in bytes. */ |
| private static final int MIN_KEY_SIZE_IN_BYTES = 16; |
| |
| /** Minimum tag size in bytes. This provides minimum 80-bit security strength. */ |
| private static final int MIN_TAG_SIZE_IN_BYTES = 10; |
| |
| /** @param serializedKey serialized {@code HmacKey} proto */ |
| @Override |
| public Mac getPrimitiveFromKey(HmacKey keyProto) throws GeneralSecurityException { |
| HashType hash = keyProto.getParams().getHash(); |
| byte[] keyValue = keyProto.getKeyValue().toByteArray(); |
| SecretKeySpec keySpec = new SecretKeySpec(keyValue, "HMAC"); |
| int tagSize = keyProto.getParams().getTagSize(); |
| switch (hash) { |
| case SHA1: |
| return new MacJce("HMACSHA1", keySpec, tagSize); |
| case SHA256: |
| return new MacJce("HMACSHA256", keySpec, tagSize); |
| case SHA512: |
| return new MacJce("HMACSHA512", keySpec, tagSize); |
| default: |
| throw new GeneralSecurityException("unknown hash"); |
| } |
| } |
| |
| /** |
| * @param serializedKeyFormat serialized {@code HmacKeyFormat} proto |
| * @return new {@code HmacKey} proto |
| */ |
| @Override |
| public HmacKey newKeyFromFormat(HmacKeyFormat format) throws GeneralSecurityException { |
| return HmacKey.newBuilder() |
| .setVersion(VERSION) |
| .setParams(format.getParams()) |
| .setKeyValue(ByteString.copyFrom(Random.randBytes(format.getKeySize()))) |
| .build(); |
| } |
| |
| @Override |
| public int getVersion() { |
| return VERSION; |
| } |
| |
| @Override |
| protected KeyMaterialType keyMaterialType() { |
| return KeyMaterialType.SYMMETRIC; |
| } |
| |
| @Override |
| protected HmacKey parseKeyProto(ByteString byteString) |
| throws InvalidProtocolBufferException { |
| return HmacKey.parseFrom(byteString); |
| } |
| |
| @Override |
| protected HmacKeyFormat parseKeyFormatProto(ByteString byteString) |
| throws InvalidProtocolBufferException { |
| return HmacKeyFormat.parseFrom(byteString); |
| } |
| |
| @Override |
| protected void validateKey(HmacKey key) throws GeneralSecurityException { |
| Validators.validateVersion(key.getVersion(), VERSION); |
| if (key.getKeyValue().size() < MIN_KEY_SIZE_IN_BYTES) { |
| throw new GeneralSecurityException("key too short"); |
| } |
| validate(key.getParams()); |
| } |
| |
| @Override |
| protected void validateKeyFormat(HmacKeyFormat format) throws GeneralSecurityException { |
| if (format.getKeySize() < MIN_KEY_SIZE_IN_BYTES) { |
| throw new GeneralSecurityException("key too short"); |
| } |
| validate(format.getParams()); |
| } |
| |
| private void validate(HmacParams params) throws GeneralSecurityException { |
| if (params.getTagSize() < MIN_TAG_SIZE_IN_BYTES) { |
| throw new GeneralSecurityException("tag size too small"); |
| } |
| switch (params.getHash()) { |
| case SHA1: |
| if (params.getTagSize() > 20) { |
| throw new GeneralSecurityException("tag size too big"); |
| } |
| break; |
| case SHA256: |
| if (params.getTagSize() > 32) { |
| throw new GeneralSecurityException("tag size too big"); |
| } |
| break; |
| case SHA512: |
| if (params.getTagSize() > 64) { |
| throw new GeneralSecurityException("tag size too big"); |
| } |
| break; |
| default: |
| throw new GeneralSecurityException("unknown hash type"); |
| } |
| } |
| } |