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// Copyright 2022 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 signature
import (
"crypto"
"crypto/rsa"
"hash"
"github.com/tink-crypto/tink-go/v2/subtle"
"github.com/tink-crypto/tink-go/v2/tink"
)
// RSA_SSA_PKCS1_Verifier is an implementation of Verifier for RSA-SSA-PKCS1.
type RSA_SSA_PKCS1_Verifier struct {
publicKey *rsa.PublicKey
hashFunc func() hash.Hash
hashID crypto.Hash
}
var _ tink.Verifier = (*RSA_SSA_PKCS1_Verifier)(nil)
// New_RSA_SSA_PKCS1_Verifier creates a new intance of RSASSAPKCS1Verifier.
func New_RSA_SSA_PKCS1_Verifier(hashAlg string, pubKey *rsa.PublicKey) (*RSA_SSA_PKCS1_Verifier, error) {
if err := validRSAPublicKey(pubKey); err != nil {
return nil, err
}
hashFunc, hashID, err := rsaHashFunc(hashAlg)
if err != nil {
return nil, err
}
return &RSA_SSA_PKCS1_Verifier{
publicKey: pubKey,
hashFunc: hashFunc,
hashID: hashID,
}, nil
}
// Verify verifies whether the given signaure is valid for the given data.
// It returns an error if the signature is not valid; nil otherwise.
func (v *RSA_SSA_PKCS1_Verifier) Verify(signature, data []byte) error {
hashed, err := subtle.ComputeHash(v.hashFunc, data)
if err != nil {
return err
}
return rsa.VerifyPKCS1v15(v.publicKey, v.hashID, hashed, signature)
}
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