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// Copyright 2023 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.jwt;
import com.google.crypto.tink.AccessesPartialKey;
import com.google.crypto.tink.InsecureSecretKeyAccess;
import com.google.crypto.tink.Key;
import com.google.crypto.tink.internal.EllipticCurvesUtil;
import com.google.crypto.tink.util.SecretBigInteger;
import com.google.errorprone.annotations.Immutable;
import com.google.errorprone.annotations.RestrictedApi;
import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.spec.ECPoint;
/**
* Represents a key for computing JWT ECDSA signatures (ES256, ES384, ES512).
*
* See https://datatracker.ietf.org/doc/html/rfc7518 for more information.
*/
@Immutable
public final class JwtEcdsaPrivateKey extends JwtSignaturePrivateKey {
public final JwtEcdsaPublicKey publicKey;
public final SecretBigInteger privateKeyValue;
private static void validatePrivateValue(
BigInteger privateValue, ECPoint publicPoint, JwtEcdsaParameters.Algorithm algorithm)
throws GeneralSecurityException {
BigInteger order = algorithm.getECParameterSpec().getOrder();
if ((privateValue.signum() <= 0) || (privateValue.compareTo(order) >= 0)) {
throw new GeneralSecurityException("Invalid private value");
}
ECPoint p =
EllipticCurvesUtil.multiplyByGenerator(privateValue, algorithm.getECParameterSpec());
if (!p.equals(publicPoint)) {
throw new GeneralSecurityException("Invalid private value");
}
}
@RestrictedApi(
explanation = "Accessing parts of keys can produce unexpected incompatibilities, annotate the function with @AccessesPartialKey",
link = "https://developers.google.com/tink/design/access_control#accessing_partial_keys",
allowedOnPath = ".*Test\\.java",
allowlistAnnotations = {AccessesPartialKey.class})
@AccessesPartialKey
public static JwtEcdsaPrivateKey create(
JwtEcdsaPublicKey publicKey, SecretBigInteger privateValue) throws GeneralSecurityException {
validatePrivateValue(
privateValue.getBigInteger(InsecureSecretKeyAccess.get()),
publicKey.getPublicPoint(),
publicKey.getParameters().getAlgorithm());
return new JwtEcdsaPrivateKey(publicKey, privateValue);
}
private JwtEcdsaPrivateKey(JwtEcdsaPublicKey publicKey, SecretBigInteger privateKeyValue) {
this.publicKey = publicKey;
this.privateKeyValue = privateKeyValue;
}
@RestrictedApi(
explanation = "Accessing parts of keys can produce unexpected incompatibilities, annotate the function with @AccessesPartialKey",
link = "https://developers.google.com/tink/design/access_control#accessing_partial_keys",
allowedOnPath = ".*Test\\.java",
allowlistAnnotations = {AccessesPartialKey.class})
public SecretBigInteger getPrivateValue() {
return privateKeyValue;
}
@Override
public JwtEcdsaParameters getParameters() {
return publicKey.getParameters();
}
@Override
public JwtEcdsaPublicKey getPublicKey() {
return publicKey;
}
@Override
public boolean equalsKey(Key o) {
if (!(o instanceof JwtEcdsaPrivateKey)) {
return false;
}
JwtEcdsaPrivateKey that = (JwtEcdsaPrivateKey) o;
return that.publicKey.equalsKey(publicKey)
&& privateKeyValue.equalsSecretBigInteger(that.privateKeyValue);
}
}