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mac.go
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mac.go
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// Copyright 2016 ETH Zurich
//
// 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 scrypto
import (
"crypto/aes"
"crypto/sha256"
"hash"
"github.com/dchest/cmac"
"golang.org/x/crypto/pbkdf2"
"github.com/scionproto/scion/pkg/private/common"
"github.com/scionproto/scion/pkg/private/serrors"
)
const (
ErrCipherFailure common.ErrMsg = "Unable to initialize AES cipher"
ErrMacFailure common.ErrMsg = "Unable to initialize Mac"
)
var (
hfMacSalt = []byte("Derive OF Key")
)
func InitMac(key []byte) (hash.Hash, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, serrors.Wrap(ErrCipherFailure, err)
}
mac, err := cmac.New(block)
if err != nil {
return nil, serrors.Wrap(ErrMacFailure, err)
}
return mac, nil
}
func HFMacFactory(key []byte) (func() hash.Hash, error) {
// Generate keys
// This uses 16B keys with 1000 hash iterations, which is the same as the
// defaults used by pycrypto.
hfGenKey := pbkdf2.Key(key, hfMacSalt, 1000, 16, sha256.New)
// First check for MAC creation errors.
if _, err := InitMac(hfGenKey); err != nil {
return nil, err
}
f := func() hash.Hash {
mac, _ := InitMac(hfGenKey)
return mac
}
return f, nil
}