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/*
* Copyright 2020-2022 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.services.s3.internal.crypto.keywrap;
import static com.amazonaws.util.Throwables.failure;
import java.nio.charset.StandardCharsets;
import java.security.Key;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import com.amazonaws.services.s3.internal.crypto.JceEncryptionConstants;
import javax.crypto.Cipher;
import javax.crypto.spec.OAEPParameterSpec;
import javax.crypto.spec.PSource;
import javax.crypto.spec.SecretKeySpec;
public final class RsaOaepKeyWrapper implements KeyWrapper {
private static final String CIPHER_ALGORITHM = "RSA/ECB/OAEPPadding";
private static final Map DIGEST_SCHEME_MAP;
private static final Map MGF1_SCHEME_MAP;
static {
Map mdMap = new HashMap<>();
mdMap.put(InternalKeyWrapAlgorithm.RSA_OAEP_SHA1, "SHA-1");
DIGEST_SCHEME_MAP = Collections.unmodifiableMap(mdMap);
Map mgf1Map = new HashMap<>();
mgf1Map.put(InternalKeyWrapAlgorithm.RSA_OAEP_SHA1, Mgf1Scheme.MGF1_SHA1);
MGF1_SCHEME_MAP = Collections.unmodifiableMap(mgf1Map);
}
private final CipherProvider cipherProvider;
private final String digestScheme;
private final Mgf1Scheme mgf1Scheme;
private final InternalKeyWrapAlgorithm cryptoKeyWrapAlgorithm;
private final String cekAlgorithm;
private final byte[] encodedCekAlgorithm;
private RsaOaepKeyWrapper(Builder b) {
this.cipherProvider = validateNotNull(b.cipherProvider, "cipherProvider");
this.cryptoKeyWrapAlgorithm = validateNotNull(b.cryptoKeyWrapAlgorithm, "cryptoKeyAlgorithm");
this.cekAlgorithm = validateNotNull(b.cekAlgorithm, "cekAlgorithm");
this.encodedCekAlgorithm = b.cekAlgorithm.getBytes(StandardCharsets.UTF_8);
this.digestScheme = DIGEST_SCHEME_MAP.get(this.cryptoKeyWrapAlgorithm);
this.mgf1Scheme = MGF1_SCHEME_MAP.get(this.cryptoKeyWrapAlgorithm);
if (this.mgf1Scheme == null) {
throw new IllegalArgumentException("No valid MGF1 scheme could be found for cryptoKeyAlgorithm '" +
this.cryptoKeyWrapAlgorithm.algorithmName() + "'");
}
}
public static Builder builder() {
return new Builder();
}
/**
* The cipher algorithm name is the string used to correctly configure the cipher provider.
* Do not confuse with {@link InternalKeyWrapAlgorithm#algorithmName()} which is an agreed-upon term
* within Amazon Web Services.
*/
public static String cipherAlgorithm() {
return CIPHER_ALGORITHM;
}
@Override
public byte[] unwrapCek(byte[] wrappedCek, Key key) {
Cipher cipher = this.cipherProvider.createCipher();
OAEPParameterSpec oaepParams =
new OAEPParameterSpec(digestScheme, "MGF1", mgf1Scheme.getMgf1ParameterSpec(), PSource.PSpecified.DEFAULT);
try {
cipher.init(Cipher.UNWRAP_MODE, key, oaepParams);
Key unwrappedKey =
cipher.unwrap(wrappedCek, JceEncryptionConstants.SYMMETRIC_KEY_ALGORITHM, Cipher.SECRET_KEY);
return splitConcatenatedKey(unwrappedKey.getEncoded());
} catch (Exception e) {
throw failure(e, "An exception was thrown when attempting to decrypt the Content Encryption Key");
}
}
@Override
public byte[] wrapCek(byte[] unwrappedCek, Key key) {
Cipher cipher = this.cipherProvider.createCipher();
OAEPParameterSpec oaepParams =
new OAEPParameterSpec(digestScheme, "MGF1", mgf1Scheme.getMgf1ParameterSpec(), PSource.PSpecified.DEFAULT);
try {
cipher.init(Cipher.WRAP_MODE, key, oaepParams);
return cipher.wrap(new SecretKeySpec(createCompositeCek(unwrappedCek),
JceEncryptionConstants.SYMMETRIC_KEY_ALGORITHM));
} catch (Exception e) {
throw failure(e, "An exception was thrown when attempting to encrypt the Content Encryption Key");
}
}
public CipherProvider cipherProvider() {
return cipherProvider;
}
public Mgf1Scheme mgf1Scheme() {
return mgf1Scheme;
}
public String cekAlgorithm() {
return this.cekAlgorithm;
}
private T validateNotNull(T obj, String propertyName) {
if (obj == null) {
throw new NullPointerException("Error initializing RsaOaepKeyWrapper: '" + propertyName +
"' cannot be null");
}
return obj;
}
private byte[] createCompositeCek(byte[] cek) {
int concatenatedKeyLength = 1 + cek.length + encodedCekAlgorithm.length;
byte[] concatenatedKeyValue = new byte[concatenatedKeyLength];
concatenatedKeyValue[0] = (byte) cek.length;
System.arraycopy(cek, 0, concatenatedKeyValue, 1, cek.length);
System.arraycopy(encodedCekAlgorithm, 0, concatenatedKeyValue, 1 + cek.length, encodedCekAlgorithm.length);
return concatenatedKeyValue;
}
private byte[] splitConcatenatedKey(byte[] concatenatedKek) {
int keyLength = concatenatedKek[0];
int algoLength = concatenatedKek.length - keyLength - 1;
if (!isValidKeyLength(keyLength)) {
throw new SecurityException("invalid key length in composite CEK");
}
if (algoLength <= 0) {
throw new SecurityException("invalid algorithm length in composite CEK");
}
byte[] cek = new byte[keyLength];
byte[] algo = new byte[algoLength];
System.arraycopy(concatenatedKek, 1, cek, 0, keyLength);
System.arraycopy(concatenatedKek, 1 + keyLength, algo, 0, algoLength);
if (!Arrays.equals(algo, this.encodedCekAlgorithm)) {
throw new SecurityException("The content encryption algorithm used at encryption time does not match the " +
"algorithm stored for decryption time. The object may be altered or " +
"corrupted.");
}
return cek;
}
private static boolean isValidKeyLength(int keyLength) {
return keyLength == 16 || keyLength == 24 || keyLength == 32;
}
public final static class Builder {
private CipherProvider cipherProvider;
private InternalKeyWrapAlgorithm cryptoKeyWrapAlgorithm;
private String cekAlgorithm;
private Builder() {
}
public Builder cipherProvider(CipherProvider cipherProvider) {
this.cipherProvider = cipherProvider;
return this;
}
public Builder cryptoKeyWrapAlgorithm(InternalKeyWrapAlgorithm cryptoKeyWrapAlgorithm) {
this.cryptoKeyWrapAlgorithm = cryptoKeyWrapAlgorithm;
return this;
}
public Builder cekAlgorithm(String cekAlgorithm) {
this.cekAlgorithm = cekAlgorithm;
return this;
}
public RsaOaepKeyWrapper build() {
return new RsaOaepKeyWrapper(this);
}
}
}
