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// Copyright 2020 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 subtle
import (
"crypto/ed25519"
"errors"
"fmt"
)
var errInvalidED25519Signature = errors.New("ed25519: invalid signature")
// ED25519Verifier is an implementation of Verifier for ED25519.
// At the moment, the implementation only accepts signatures with strict DER encoding.
type ED25519Verifier struct {
publicKey *ed25519.PublicKey
}
// NewED25519Verifier creates a new instance of ED25519Verifier.
func NewED25519Verifier(pub []byte) (*ED25519Verifier, error) {
publicKey := ed25519.PublicKey(pub)
return NewED25519VerifierFromPublicKey(&publicKey)
}
// NewED25519VerifierFromPublicKey creates a new instance of ED25519Verifier.
func NewED25519VerifierFromPublicKey(publicKey *ed25519.PublicKey) (*ED25519Verifier, error) {
return &ED25519Verifier{
publicKey: publicKey,
}, nil
}
// Verify verifies whether the given signature is valid for the given data.
// It returns an error if the signature is not valid; nil otherwise.
func (e *ED25519Verifier) Verify(signature, data []byte) error {
if len(signature) != ed25519.SignatureSize {
return fmt.Errorf("the length of the signature is not %d", ed25519.SignatureSize)
}
if !ed25519.Verify(*e.publicKey, data, signature) {
return errInvalidED25519Signature
}
return nil
}
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