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/*
* Copyright 2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except
* in compliance with the License. A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.amazonaws.encryptionsdk.jce;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import com.amazonaws.encryptionsdk.CryptoAlgorithm;
import com.amazonaws.encryptionsdk.DataKey;
import com.amazonaws.encryptionsdk.EncryptedDataKey;
import com.amazonaws.encryptionsdk.MasterKey;
import com.amazonaws.encryptionsdk.exception.AwsCryptoException;
import com.amazonaws.encryptionsdk.exception.UnsupportedProviderException;
import com.amazonaws.encryptionsdk.internal.EncryptionContextSerializer;
/**
* Represents a {@link MasterKey} backed by one (or more) JCE {@link Key}s. Instances of this should
* only be acquired using {@link #getInstance(SecretKey, String, String, String)} or
* {@link #getInstance(PublicKey, PrivateKey, String, String, String)}.
*/
public abstract class JceMasterKey extends MasterKey {
private static final byte[] EMPTY_ARRAY = new byte[0];
private final SecureRandom rnd = new SecureRandom();
private final Key wrappingKey_;
private final Key unwrappingKey_;
private final String providerName_;
private final String keyId_;
private final byte[] keyIdBytes_;
/**
* Returns a {@code JceMasterKey} backed by {@code key} using {@code wrappingAlgorithm}.
* Currently "{@code AES/GCM/NoPadding}" is the only supported value for
* {@code wrappingAlgorithm}.
*
* @param key
* key used to wrap/unwrap (encrypt/decrypt) {@link DataKey}s
* @param provider
* @param keyId
* @param wrappingAlgorithm
* @return
*/
public static JceMasterKey getInstance(final SecretKey key, final String provider, final String keyId,
final String wrappingAlgorithm) {
switch (wrappingAlgorithm) {
case "AES/GCM/NoPadding":
return new AesGcm(key, provider, keyId);
default:
throw new IllegalArgumentException("Right now only AES/GCM/NoPadding is supported");
}
}
/**
* Returns a {@code JceMasterKey} backed by {@code unwrappingKey} and {@code wrappingKey} using
* {@code wrappingAlgorithm}. Currently only RSA algorithms are supported for
* {@code wrappingAlgorithm}. {@code wrappingAlgorithm}. If {@code unwrappingKey} is
* {@code null} then the returned {@link JceMasterKey} can only be used for encryption.
*
* @param wrappingKey
* key used to wrap (encrypt) {@link DataKey}s
* @param unwrappingKey
* (Optional) key used to unwrap (decrypt) {@link DataKey}s.
*/
public static JceMasterKey getInstance(final PublicKey wrappingKey, final PrivateKey unwrappingKey,
final String provider, final String keyId,
final String wrappingAlgorithm) {
if (wrappingAlgorithm.toUpperCase().startsWith("RSA/ECB/")) {
return new Rsa(wrappingKey, unwrappingKey, provider, keyId, wrappingAlgorithm);
}
throw new UnsupportedOperationException("Currently only RSA asymmetric algorithms are supported");
}
protected JceMasterKey(final Key wrappingKey, final Key unwrappingKey, final String providerName,
final String keyId) {
wrappingKey_ = wrappingKey;
unwrappingKey_ = unwrappingKey;
providerName_ = providerName;
keyId_ = keyId;
keyIdBytes_ = keyId_.getBytes(StandardCharsets.UTF_8);
}
@Override
public String getProviderId() {
return providerName_;
}
@Override
public String getKeyId() {
return keyId_;
}
@Override
public DataKey generateDataKey(final CryptoAlgorithm algorithm,
final Map encryptionContext) {
final byte[] rawKey = new byte[algorithm.getDataKeyLength()];
rnd.nextBytes(rawKey);
final SecretKeySpec key = new SecretKeySpec(rawKey, algorithm.getDataKeyAlgo());
return encryptRawKey(key, rawKey, encryptionContext);
}
@Override
public DataKey encryptDataKey(final CryptoAlgorithm algorithm,
final Map encryptionContext,
final DataKey dataKey) {
final SecretKey key = dataKey.getKey();
if (!key.getFormat().equals("RAW")) {
throw new IllegalArgumentException("Can only re-encrypt data keys which are in RAW format, not "
+ dataKey.getKey().getFormat());
}
if (!key.getAlgorithm().equalsIgnoreCase(algorithm.getDataKeyAlgo())) {
throw new IllegalArgumentException("Incorrect key algorithm. Expected " + key.getAlgorithm()
+ " but got " + algorithm.getKeyAlgo());
}
final byte[] rawKey = key.getEncoded();
final DataKey result = encryptRawKey(key, rawKey, encryptionContext);
Arrays.fill(rawKey, (byte) 0);
return result;
}
protected DataKey encryptRawKey(final SecretKey key, final byte[] rawKey,
final Map encryptionContext) {
try {
final WrappingData wData = buildWrappingCipher(wrappingKey_, encryptionContext);
final Cipher cipher = wData.cipher;
final byte[] encryptedKey = cipher.doFinal(rawKey);
final byte[] provInfo = new byte[keyIdBytes_.length + wData.extraInfo.length];
System.arraycopy(keyIdBytes_, 0, provInfo, 0, keyIdBytes_.length);
System.arraycopy(wData.extraInfo, 0, provInfo, keyIdBytes_.length, wData.extraInfo.length);
return new DataKey<>(key, encryptedKey, provInfo, this);
} catch (final GeneralSecurityException gsex) {
throw new AwsCryptoException(gsex);
}
}
@Override
public DataKey decryptDataKey(final CryptoAlgorithm algorithm,
final Collection encryptedDataKeys,
final Map encryptionContext)
throws UnsupportedProviderException, AwsCryptoException {
final List exceptions = new ArrayList<>();
// Find an encrypted key who's provider and info match us
for (final EncryptedDataKey edk : encryptedDataKeys) {
try {
if (edk.getProviderId().equals(getProviderId())
&& arrayPrefixEquals(edk.getProviderInformation(), keyIdBytes_, keyIdBytes_.length)) {
final DataKey result = actualDecrypt(algorithm, edk, encryptionContext);
if (result != null) {
return result;
}
}
} catch (final Exception ex) {
exceptions.add(ex);
}
}
throw buildCannotDecryptDksException(exceptions);
}
protected DataKey actualDecrypt(final CryptoAlgorithm algorithm, final EncryptedDataKey edk,
final Map encryptionContext) throws GeneralSecurityException {
final Cipher cipher = buildUnwrappingCipher(unwrappingKey_, edk.getProviderInformation(),
keyIdBytes_.length,
encryptionContext);
final byte[] rawKey = cipher.doFinal(edk.getEncryptedDataKey());
if (rawKey.length != algorithm.getDataKeyLength()) {
// Something's wrong here. Assume that the decryption is invalid.
return null;
}
return new DataKey<>(
new SecretKeySpec(rawKey, algorithm.getDataKeyAlgo()),
edk.getEncryptedDataKey(),
edk.getProviderInformation(), this);
}
protected static boolean arrayPrefixEquals(final byte[] a, final byte[] b, final int len) {
if (a == null || b == null || a.length < len || b.length < len) {
return false;
}
for (int x = 0; x < len; x++) {
if (a[x] != b[x]) {
return false;
}
}
return true;
}
protected abstract WrappingData buildWrappingCipher(Key key, Map encryptionContext)
throws GeneralSecurityException;
protected abstract Cipher buildUnwrappingCipher(Key key, byte[] extraInfo, int offset,
Map encryptionContext) throws GeneralSecurityException;
private static class WrappingData {
public final Cipher cipher;
public final byte[] extraInfo;
public WrappingData(final Cipher cipher, final byte[] extraInfo) {
super();
this.cipher = cipher;
this.extraInfo = extraInfo != null ? extraInfo : EMPTY_ARRAY;
}
}
private static class Rsa extends JceMasterKey {
private final String transformation_;
private Rsa(PublicKey wrappingKey, PrivateKey unwrappingKey, String providerName, String keyId,
String transformation) {
super(wrappingKey, unwrappingKey, providerName, keyId);
transformation_ = transformation;
}
@Override
protected WrappingData buildWrappingCipher(Key key, Map encryptionContext)
throws GeneralSecurityException {
// We require BouncyCastle to avoid some bugs in the default Java implementation
// of OAEP.
final Cipher cipher = Cipher.getInstance(transformation_, "BC");
cipher.init(Cipher.ENCRYPT_MODE, key);
return new WrappingData(cipher, EMPTY_ARRAY);
}
@Override
protected Cipher buildUnwrappingCipher(Key key, byte[] extraInfo, int offset,
Map encryptionContext) throws GeneralSecurityException {
if (extraInfo.length != offset) {
throw new IllegalArgumentException("Extra info must be empty for RSA keys");
}
// We require BouncyCastle to avoid some bugs in the default Java implementation
// of OAEP.
final Cipher cipher = Cipher.getInstance(transformation_, "BC");
cipher.init(Cipher.DECRYPT_MODE, key);
return cipher;
}
}
private static class AesGcm extends JceMasterKey {
private static final int NONCE_LENGTH = 12;
private static final int TAG_LENGTH = 128;
private static final String TRANSFORMATION = "AES/GCM/NoPadding";
private final SecureRandom rnd = new SecureRandom();
public AesGcm(final SecretKey key, final String providerName, final String keyId) {
super(key, key, providerName, keyId);
}
private static byte[] specToBytes(final GCMParameterSpec spec) {
final byte[] nonce = spec.getIV();
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
try (final DataOutputStream dos = new DataOutputStream(baos)) {
dos.writeInt(spec.getTLen());
dos.writeInt(nonce.length);
dos.write(nonce);
dos.close();
baos.close();
} catch (final IOException ex) {
throw new AssertionError("Impossible exception", ex);
}
return baos.toByteArray();
}
private static GCMParameterSpec bytesToSpec(final byte[] data, final int offset) {
final ByteArrayInputStream bais = new ByteArrayInputStream(data, offset, data.length - offset);
try (final DataInputStream dis = new DataInputStream(bais)) {
final int tagLen = dis.readInt();
final int nonceLen = dis.readInt();
final byte[] nonce = new byte[nonceLen];
dis.readFully(nonce);
return new GCMParameterSpec(tagLen, nonce);
} catch (final IOException ex) {
throw new AssertionError("Impossible exception", ex);
}
}
@Override
protected WrappingData buildWrappingCipher(final Key key, final Map encryptionContext)
throws GeneralSecurityException {
final byte[] nonce = new byte[NONCE_LENGTH];
rnd.nextBytes(nonce);
final GCMParameterSpec spec = new GCMParameterSpec(TAG_LENGTH, nonce);
final Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
final byte[] aad = EncryptionContextSerializer.serialize(encryptionContext);
cipher.updateAAD(aad);
return new WrappingData(cipher, specToBytes(spec));
}
@Override
protected Cipher buildUnwrappingCipher(final Key key, final byte[] extraInfo, final int offset,
final Map encryptionContext) throws GeneralSecurityException {
final GCMParameterSpec spec = bytesToSpec(extraInfo, offset);
final Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.DECRYPT_MODE, key, spec);
final byte[] aad = EncryptionContextSerializer.serialize(encryptionContext);
cipher.updateAAD(aad);
return cipher;
}
}
}
