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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.internal.EllipticCurvesUtil;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.Immutable;
import java.security.GeneralSecurityException;
import java.security.spec.ECParameterSpec;
import java.util.Objects;
import java.util.Optional;
/** Describes the parameters of a {@code JwtEcdsaPrivateKey} or a {@code JwtEcdsaPublicKey}. */
public final class JwtEcdsaParameters extends JwtSignatureParameters {
/** Specifies how the "kid" header is handled. */
@Immutable
public static final class KidStrategy {
/**
* The "kid" is the URL safe (RFC 4648 Section 5) base64-encoded big-endian key_id in the
* keyset.
*
* <p>In {@code PublicKeySign#signAndEncode} Tink always adds the KID.
*
* <p>In {@code PublicKeyVerify#verifyAndDecode} Tink checks that the kid is present and equal
* to this value.
*
* <p>This strategy is recommended by Tink.
*/
public static final KidStrategy BASE64_ENCODED_KEY_ID =
new KidStrategy("BASE64_ENCODED_KEY_ID");
/**
* The "kid" header is ignored.
*
* <p>In {@code PublicKeySign#signAndEncode} Tink does not write a "kid" header.
*
* <p>In {@code PublicKeyVerify#verifyAndDecode} Tink ignores the "kid" header.
*/
public static final KidStrategy IGNORED = new KidStrategy("IGNORED");
/**
* The "kid" is fixed. It can be obtained from {@code parameters.getCustomKid()}.
*
* <p>In {@code PublicKeySign#signAndEncode} Tink writes the "kid" header to the value given by
* {@code parameters.getCustomKid()}.
*
* <p>In {@code PublicKeyVerify#verifyAndDecode}, if the kid is present, it needs to match
* {@code parameters.getCustomKid()}. If the kid is absent, it will be accepted.
*
* <p>Note: Tink does not allow to randomly generate new {@link JwtEcdsaKey} objects from
* parameters objects with {@code KidStrategy} equals to {@code CUSTOM}.
*/
public static final KidStrategy CUSTOM = new KidStrategy("CUSTOM");
private final String name;
private KidStrategy(String name) {
this.name = name;
}
@Override
public String toString() {
return name;
}
}
/** The algorithm to be used for the signature computation. */
@Immutable
public static final class Algorithm {
/** ECDSA using P-256 and SHA-256 */
public static final Algorithm ES256 =
new Algorithm("ES256", EllipticCurvesUtil.NIST_P256_PARAMS);
/** ECDSA using P-384 and SHA-384 */
public static final Algorithm ES384 =
new Algorithm("ES384", EllipticCurvesUtil.NIST_P384_PARAMS);
/** ECDSA using P-521 and SHA-512 */
public static final Algorithm ES512 =
new Algorithm("ES512", EllipticCurvesUtil.NIST_P521_PARAMS);
private final String name;
@SuppressWarnings("Immutable") // ECParameterSpec is immutable
private final ECParameterSpec ecParameterSpec;
private Algorithm(String name, ECParameterSpec ecParameterSpec) {
this.name = name;
this.ecParameterSpec = ecParameterSpec;
}
@Override
public String toString() {
return name;
}
public String getStandardName() {
return name;
}
ECParameterSpec getECParameterSpec() {
return ecParameterSpec;
}
}
/** Helps creating a {@code JwtEcdsaParameters} object. */
public static final class Builder {
Optional<KidStrategy> kidStrategy = Optional.empty();
Optional<Algorithm> algorithm = Optional.empty();
@CanIgnoreReturnValue
public Builder setKidStrategy(KidStrategy kidStrategy) {
this.kidStrategy = Optional.of(kidStrategy);
return this;
}
@CanIgnoreReturnValue
public Builder setAlgorithm(Algorithm algorithm) {
this.algorithm = Optional.of(algorithm);
return this;
}
public JwtEcdsaParameters build() throws GeneralSecurityException {
if (!algorithm.isPresent()) {
throw new GeneralSecurityException("Algorithm must be set");
}
if (!kidStrategy.isPresent()) {
throw new GeneralSecurityException("KidStrategy must be set");
}
return new JwtEcdsaParameters(kidStrategy.get(), algorithm.get());
}
private Builder() {}
}
public static Builder builder() {
return new Builder();
}
private JwtEcdsaParameters(KidStrategy kidStrategy, Algorithm algorithm) {
this.kidStrategy = kidStrategy;
this.algorithm = algorithm;
}
private final KidStrategy kidStrategy;
private final Algorithm algorithm;
public KidStrategy getKidStrategy() {
return kidStrategy;
}
public Algorithm getAlgorithm() {
return algorithm;
}
@Override
public boolean hasIdRequirement() {
return kidStrategy.equals(KidStrategy.BASE64_ENCODED_KEY_ID);
}
@Override
public boolean allowKidAbsent() {
return kidStrategy.equals(KidStrategy.CUSTOM) || kidStrategy.equals(KidStrategy.IGNORED);
}
@Override
public boolean equals(Object o) {
if (!(o instanceof JwtEcdsaParameters)) {
return false;
}
JwtEcdsaParameters that = (JwtEcdsaParameters) o;
return that.kidStrategy.equals(kidStrategy) && that.algorithm.equals(algorithm);
}
@Override
public int hashCode() {
return Objects.hash(JwtEcdsaParameters.class, kidStrategy, algorithm);
}
@Override
public String toString() {
return "JWT ECDSA Parameters (kidStrategy: " + kidStrategy + ", Algorithm " + algorithm + ")";
}
}
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