| // 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.subtle; |
| |
| import com.google.crypto.tink.Aead; |
| import com.google.crypto.tink.config.TinkFips; |
| import java.security.GeneralSecurityException; |
| import java.security.spec.AlgorithmParameterSpec; |
| import javax.crypto.Cipher; |
| import javax.crypto.SecretKey; |
| import javax.crypto.spec.GCMParameterSpec; |
| import javax.crypto.spec.IvParameterSpec; |
| import javax.crypto.spec.SecretKeySpec; |
| |
| /** |
| * This primitive implements AesGcm using JCE. |
| * |
| * @since 1.0.0 |
| */ |
| public final class AesGcmJce implements Aead { |
| public static final TinkFips.AlgorithmFipsCompatibility FIPS = |
| TinkFips.AlgorithmFipsCompatibility.ALGORITHM_REQUIRES_BORINGCRYPTO; |
| |
| private static final ThreadLocal<Cipher> localCipher = |
| new ThreadLocal<Cipher>() { |
| @Override |
| protected Cipher initialValue() { |
| try { |
| return EngineFactory.CIPHER.getInstance("AES/GCM/NoPadding"); |
| } catch (GeneralSecurityException ex) { |
| throw new IllegalStateException(ex); |
| } |
| } |
| }; |
| |
| // All instances of this class use a 12 byte IV and a 16 byte tag. |
| private static final int IV_SIZE_IN_BYTES = 12; |
| private static final int TAG_SIZE_IN_BYTES = 16; |
| |
| private final SecretKey keySpec; |
| |
| public AesGcmJce(final byte[] key) throws GeneralSecurityException { |
| if (!FIPS.isCompatible()) { |
| throw new GeneralSecurityException( |
| "Can not use AES-GCM in FIPS-mode, as BoringCrypto module is not available."); |
| } |
| Validators.validateAesKeySize(key.length); |
| keySpec = new SecretKeySpec(key, "AES"); |
| } |
| |
| @Override |
| /** |
| * On Android KitKat (API level 19) this method does not support non null or non empty {@code |
| * associatedData}. It might not work at all in older versions. |
| */ |
| public byte[] encrypt(final byte[] plaintext, final byte[] associatedData) |
| throws GeneralSecurityException { |
| // Check that ciphertext is not longer than the max. size of a Java array. |
| if (plaintext.length > Integer.MAX_VALUE - IV_SIZE_IN_BYTES - TAG_SIZE_IN_BYTES) { |
| throw new GeneralSecurityException("plaintext too long"); |
| } |
| byte[] ciphertext = new byte[IV_SIZE_IN_BYTES + plaintext.length + TAG_SIZE_IN_BYTES]; |
| byte[] iv = Random.randBytes(IV_SIZE_IN_BYTES); |
| System.arraycopy(iv, 0, ciphertext, 0, IV_SIZE_IN_BYTES); |
| |
| AlgorithmParameterSpec params = getParams(iv); |
| localCipher.get().init(Cipher.ENCRYPT_MODE, keySpec, params); |
| if (associatedData != null && associatedData.length != 0) { |
| localCipher.get().updateAAD(associatedData); |
| } |
| int written = |
| localCipher.get().doFinal(plaintext, 0, plaintext.length, ciphertext, IV_SIZE_IN_BYTES); |
| // For security reasons, AES-GCM encryption must always use tag of TAG_SIZE_IN_BYTES bytes. If |
| // so, written must be equal to plaintext.length + TAG_SIZE_IN_BYTES. |
| |
| if (written != plaintext.length + TAG_SIZE_IN_BYTES) { |
| // The tag is shorter than expected. |
| int actualTagSize = written - plaintext.length; |
| throw new GeneralSecurityException( |
| String.format( |
| "encryption failed; GCM tag must be %s bytes, but got only %s bytes", |
| TAG_SIZE_IN_BYTES, actualTagSize)); |
| } |
| return ciphertext; |
| } |
| |
| @Override |
| /** |
| * On Android KitKat (API level 19) this method does not support non null or non empty {@code |
| * associatedData}. It might not work at all in older versions. |
| */ |
| public byte[] decrypt(final byte[] ciphertext, final byte[] associatedData) |
| throws GeneralSecurityException { |
| if (ciphertext.length < IV_SIZE_IN_BYTES + TAG_SIZE_IN_BYTES) { |
| throw new GeneralSecurityException("ciphertext too short"); |
| } |
| |
| AlgorithmParameterSpec params = getParams(ciphertext, 0, IV_SIZE_IN_BYTES); |
| localCipher.get().init(Cipher.DECRYPT_MODE, keySpec, params); |
| if (associatedData != null && associatedData.length != 0) { |
| localCipher.get().updateAAD(associatedData); |
| } |
| return localCipher |
| .get() |
| .doFinal(ciphertext, IV_SIZE_IN_BYTES, ciphertext.length - IV_SIZE_IN_BYTES); |
| } |
| |
| private static AlgorithmParameterSpec getParams(final byte[] iv) throws GeneralSecurityException { |
| return getParams(iv, 0, iv.length); |
| } |
| |
| private static AlgorithmParameterSpec getParams(final byte[] buf, int offset, int len) |
| throws GeneralSecurityException { |
| if (SubtleUtil.isAndroid() && SubtleUtil.androidApiLevel() <= 19) { |
| // GCMParameterSpec should always be present in Java 7 or newer, but it's unsupported on |
| // Android devices with API level <= 19. Fortunately, if a modern copy of Conscrypt is present |
| // (either through GMS Core or bundled with the app) we can initialize the cipher with just an |
| // IvParameterSpec. |
| // It will use a tag size of 128 bits. We'd double check the tag size in encrypt(). |
| return new IvParameterSpec(buf, offset, len); |
| } |
| return new GCMParameterSpec(8 * TAG_SIZE_IN_BYTES, buf, offset, len); |
| } |
| }; |