com.google.crypto.tink.signature.RsaSsaPkcs1Parameters Maven / Gradle / Ivy
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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.signature;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.Immutable;
import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.InvalidAlgorithmParameterException;
import java.util.Objects;
import javax.annotation.Nullable;
/**
* Describes the parameters of a {@link RsaSsaPkcs1PublicKey} and {@link RsaSsaPkcs1PrivateKey}.
*
* Standard: https://www.rfc-editor.org/rfc/rfc8017.txt
*/
public final class RsaSsaPkcs1Parameters extends SignatureParameters {
/**
* Describes details of the signature.
*
*
The usual key is used for variant "NO_PREFIX". Other variants slightly change how the
* signature is computed, or add a prefix to every computation depending on the key id.
*/
@Immutable
public static final class Variant {
public static final Variant TINK = new Variant("TINK");
public static final Variant CRUNCHY = new Variant("CRUNCHY");
public static final Variant LEGACY = new Variant("LEGACY");
public static final Variant NO_PREFIX = new Variant("NO_PREFIX");
private final String name;
private Variant(String name) {
this.name = name;
}
@Override
public String toString() {
return name;
}
}
/** The Hash algorithm used. */
@Immutable
public static final class HashType {
public static final HashType SHA256 = new HashType("SHA256");
public static final HashType SHA384 = new HashType("SHA384");
public static final HashType SHA512 = new HashType("SHA512");
private final String name;
private HashType(String name) {
this.name = name;
}
@Override
public String toString() {
return name;
}
}
public static final BigInteger F4 = BigInteger.valueOf(65537);
/** Builds a new RsaSsaPkcs1Parameters instance. */
public static final class Builder {
@Nullable private Integer modulusSizeBits = null;
@Nullable private BigInteger publicExponent = F4;
@Nullable private HashType hashType = null;
private Variant variant = Variant.NO_PREFIX;
private Builder() {}
@CanIgnoreReturnValue
public Builder setModulusSizeBits(int modulusSizeBits) {
this.modulusSizeBits = modulusSizeBits;
return this;
}
@CanIgnoreReturnValue
public Builder setPublicExponent(BigInteger e) {
this.publicExponent = e;
return this;
}
@CanIgnoreReturnValue
public Builder setVariant(Variant variant) {
this.variant = variant;
return this;
}
@CanIgnoreReturnValue
public Builder setHashType(HashType hashType) {
this.hashType = hashType;
return this;
}
private static final BigInteger TWO = BigInteger.valueOf(2);
private static final BigInteger PUBLIC_EXPONENT_UPPER_BOUND = TWO.pow(256);
private void validatePublicExponent(BigInteger publicExponent)
throws InvalidAlgorithmParameterException {
// We use the validation of the public exponent as defined in
// https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf, B.3
int c = publicExponent.compareTo(F4);
if (c == 0) {
// publicExponent is F4.
return;
}
if (c < 0) {
// publicExponent is smaller than F4.
throw new InvalidAlgorithmParameterException("Public exponent must be at least 65537.");
}
if (publicExponent.mod(TWO).equals(BigInteger.ZERO)) {
// publicExponent is even. This is invalid since it is not co-prime to p-1.
throw new InvalidAlgorithmParameterException("Invalid public exponent");
}
if (publicExponent.compareTo(PUBLIC_EXPONENT_UPPER_BOUND) > 0) {
// publicExponent is larger than PUBLIC_EXPONENT_UPPER_BOUND.
throw new InvalidAlgorithmParameterException(
"Public exponent cannot be larger than 2^256.");
}
}
public RsaSsaPkcs1Parameters build() throws GeneralSecurityException {
if (modulusSizeBits == null) {
throw new GeneralSecurityException("key size is not set");
}
if (publicExponent == null) {
throw new GeneralSecurityException("publicExponent is not set");
}
if (hashType == null) {
throw new GeneralSecurityException("hash type is not set");
}
if (variant == null) {
throw new GeneralSecurityException("variant is not set");
}
if (modulusSizeBits < 2048) {
throw new InvalidAlgorithmParameterException(
String.format(
"Invalid key size in bytes %d; must be at least 2048 bits", modulusSizeBits));
}
validatePublicExponent(publicExponent);
return new RsaSsaPkcs1Parameters(modulusSizeBits, publicExponent, variant, hashType);
}
}
private final int modulusSizeBits;
private final BigInteger publicExponent;
private final Variant variant;
private final HashType hashType;
private RsaSsaPkcs1Parameters(
int modulusSizeBits, BigInteger publicExponent, Variant variant, HashType hashType) {
this.modulusSizeBits = modulusSizeBits;
this.publicExponent = publicExponent;
this.variant = variant;
this.hashType = hashType;
}
public static Builder builder() {
return new Builder();
}
public int getModulusSizeBits() {
return modulusSizeBits;
}
public BigInteger getPublicExponent() {
return publicExponent;
}
public Variant getVariant() {
return variant;
}
public HashType getHashType() {
return hashType;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof RsaSsaPkcs1Parameters)) {
return false;
}
RsaSsaPkcs1Parameters that = (RsaSsaPkcs1Parameters) o;
return that.getModulusSizeBits() == getModulusSizeBits()
&& Objects.equals(that.getPublicExponent(), getPublicExponent())
&& that.getVariant() == getVariant()
&& that.getHashType() == getHashType();
}
@Override
public int hashCode() {
return Objects.hash(
RsaSsaPkcs1Parameters.class, modulusSizeBits, publicExponent, variant, hashType);
}
@Override
public boolean hasIdRequirement() {
return variant != Variant.NO_PREFIX;
}
@Override
public String toString() {
return "RSA SSA PKCS1 Parameters (variant: "
+ variant
+ ", hashType: "
+ hashType
+ ", publicExponent: "
+ publicExponent
+ ", and "
+ modulusSizeBits
+ "-bit modulus)";
}
}