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// Copyright 2024 OpenPubkey
//
// 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.
//
// SPDX-License-Identifier: Apache-2.0
package cosigner
import (
"crypto"
"crypto/hmac"
"encoding/binary"
"encoding/hex"
"fmt"
"sync/atomic"
)
type AuthIDIssuer struct {
authIdIter atomic.Uint64
hmacKey []byte
}
func NewAuthIDIssuer(hmacKey []byte) *AuthIDIssuer {
return &AuthIDIssuer{
authIdIter: atomic.Uint64{},
hmacKey: hmacKey,
}
}
func (i *AuthIDIssuer) CreateAuthID(timeNow uint64) (string, error) {
authIdInt := i.authIdIter.Add(1)
iterAndTime := []byte{}
iterAndTime = binary.LittleEndian.AppendUint64(iterAndTime, uint64(authIdInt))
iterAndTime = binary.LittleEndian.AppendUint64(iterAndTime, timeNow)
mac := hmac.New(crypto.SHA3_256.New, i.hmacKey)
if n, err := mac.Write(iterAndTime); err != nil {
return "", err
} else if n != 16 {
return "", fmt.Errorf("unexpected number of bytes read by HMAC, expected 16, got %d", n)
} else {
return hex.EncodeToString(mac.Sum(nil)), nil
}
}
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