com.google.crypto.tink.signature.RsaSsaPkcs1PublicKey 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.crypto.tink.AccessesPartialKey;
import com.google.crypto.tink.Key;
import com.google.crypto.tink.annotations.Alpha;
import com.google.crypto.tink.util.Bytes;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.RestrictedApi;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.security.GeneralSecurityException;
import java.util.Objects;
import javax.annotation.Nullable;
/**
* Represents a public key for the RSA SSA PKCS1 signature primitive.
*
* Standard: https://www.rfc-editor.org/rfc/rfc8017.txt
*
*
This API is annotated with Alpha because it is not yet stable and might be changed in the
* future.
*/
@Alpha
public final class RsaSsaPkcs1PublicKey extends SignaturePublicKey {
private final RsaSsaPkcs1Parameters parameters;
private final BigInteger modulus;
private final Bytes outputPrefix;
@Nullable private final Integer idRequirement;
/** Builder for RsaSsaPkcs1PublicKey. */
public static class Builder {
@Nullable private RsaSsaPkcs1Parameters parameters = null;
@Nullable private BigInteger modulus = null;
@Nullable private Integer idRequirement = null;
private Builder() {}
@CanIgnoreReturnValue
public Builder setParameters(RsaSsaPkcs1Parameters parameters) {
this.parameters = parameters;
return this;
}
@CanIgnoreReturnValue
public Builder setModulus(BigInteger modulus) {
this.modulus = modulus;
return this;
}
@CanIgnoreReturnValue
public Builder setIdRequirement(@Nullable Integer idRequirement) {
this.idRequirement = idRequirement;
return this;
}
private Bytes getOutputPrefix() {
if (parameters.getVariant() == RsaSsaPkcs1Parameters.Variant.NO_PREFIX) {
return Bytes.copyFrom(new byte[] {});
}
if (parameters.getVariant() == RsaSsaPkcs1Parameters.Variant.LEGACY
|| parameters.getVariant() == RsaSsaPkcs1Parameters.Variant.CRUNCHY) {
return Bytes.copyFrom(ByteBuffer.allocate(5).put((byte) 0).putInt(idRequirement).array());
}
if (parameters.getVariant() == RsaSsaPkcs1Parameters.Variant.TINK) {
return Bytes.copyFrom(ByteBuffer.allocate(5).put((byte) 1).putInt(idRequirement).array());
}
throw new IllegalStateException(
"Unknown RsaSsaPkcs1Parameters.Variant: " + parameters.getVariant());
}
public RsaSsaPkcs1PublicKey build() throws GeneralSecurityException {
if (parameters == null) {
throw new GeneralSecurityException("Cannot build without parameters");
}
if (modulus == null) {
throw new GeneralSecurityException("Cannot build without modulus");
}
int modulusSize = modulus.bitLength();
int paramModulusSize = parameters.getModulusSizeBits();
// https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf, B.3 requires p and q
// to be chosen such that 2^(paramModulusSize-1) < modulus < 2^paramModulusSize.
if (modulusSize != paramModulusSize) {
throw new GeneralSecurityException(
"Got modulus size "
+ modulusSize
+ ", but parameters requires modulus size "
+ paramModulusSize);
}
if (parameters.hasIdRequirement() && idRequirement == null) {
throw new GeneralSecurityException(
"Cannot create key without ID requirement with parameters with ID requirement");
}
if (!parameters.hasIdRequirement() && idRequirement != null) {
throw new GeneralSecurityException(
"Cannot create key with ID requirement with parameters without ID requirement");
}
Bytes outputPrefix = getOutputPrefix();
return new RsaSsaPkcs1PublicKey(parameters, modulus, outputPrefix, idRequirement);
}
}
private RsaSsaPkcs1PublicKey(
RsaSsaPkcs1Parameters parameters,
BigInteger modulus,
Bytes outputPrefix,
@Nullable Integer idRequirement) {
this.parameters = parameters;
this.modulus = modulus;
this.outputPrefix = outputPrefix;
this.idRequirement = idRequirement;
}
@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 static Builder builder() {
return new Builder();
}
/** Returns the underlying key bytes. */
@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 BigInteger getModulus() {
return modulus;
}
@Override
public Bytes getOutputPrefix() {
return outputPrefix;
}
@Override
public RsaSsaPkcs1Parameters getParameters() {
return parameters;
}
@Override
@Nullable
public Integer getIdRequirementOrNull() {
return idRequirement;
}
@Override
public boolean equalsKey(Key o) {
if (!(o instanceof RsaSsaPkcs1PublicKey)) {
return false;
}
RsaSsaPkcs1PublicKey that = (RsaSsaPkcs1PublicKey) o;
// Since outputPrefix is a function of parameters, we can ignore it here.
return that.parameters.equals(parameters)
&& that.modulus.equals(modulus)
&& Objects.equals(that.idRequirement, idRequirement);
}
}