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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2022 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package keys
import (
"crypto/rand"
"fmt"
"io"
"os"
"path/filepath"
"github.com/snapcore/snapd/osutil"
)
const (
// The encryption key size is set so it has the same entropy as the derived
// key.
EncryptionKeySize = 32
// XXX: needs to be in sync with
// github.com/snapcore/secboot/crypto.go:"type RecoveryKey"
// Size of the recovery key.
RecoveryKeySize = 16
// The auxiliary key is used to bind keys to models
AuxKeySize = 32
)
// used in tests
var randRead = rand.Read
// EncryptionKey is the key used to encrypt the data partition.
type EncryptionKey []byte
func NewEncryptionKey() (EncryptionKey, error) {
key := make(EncryptionKey, EncryptionKeySize)
// rand.Read() is protected against short reads
_, err := randRead(key[:])
// On return, n == len(b) if and only if err == nil
return key, err
}
// Save writes the key in the location specified by filename.
func (key EncryptionKey) Save(filename string) error {
if err := os.MkdirAll(filepath.Dir(filename), 0755); err != nil {
return err
}
return osutil.AtomicWriteFile(filename, key[:], 0600, 0)
}
// RecoveryKey is a key used to unlock the encrypted partition when
// the encryption key can't be used, for example when unseal fails.
type RecoveryKey [RecoveryKeySize]byte
func NewRecoveryKey() (RecoveryKey, error) {
var key RecoveryKey
// rand.Read() is protected against short reads
_, err := randRead(key[:])
// On return, n == len(b) if and only if err == nil
return key, err
}
// Save writes the recovery key in the location specified by filename.
func (key RecoveryKey) Save(filename string) error {
if err := os.MkdirAll(filepath.Dir(filename), 0755); err != nil {
return err
}
return osutil.AtomicWriteFile(filename, key[:], 0600, 0)
}
func RecoveryKeyFromFile(recoveryKeyFile string) (*RecoveryKey, error) {
f, err := os.Open(recoveryKeyFile)
if err != nil {
return nil, fmt.Errorf("cannot open recovery key: %v", err)
}
defer f.Close()
st, err := f.Stat()
if err != nil {
return nil, fmt.Errorf("cannot stat recovery key: %v", err)
}
if st.Size() != int64(len(RecoveryKey{})) {
return nil, fmt.Errorf("cannot read recovery key: unexpected size %v for the recovery key file %s", st.Size(), recoveryKeyFile)
}
var rkey RecoveryKey
if _, err := io.ReadFull(f, rkey[:]); err != nil {
return nil, fmt.Errorf("cannot read recovery key: %v", err)
}
return &rkey, nil
}
// AuxKey is the key to bind models to keys.
type AuxKey [AuxKeySize]byte
func NewAuxKey() (AuxKey, error) {
var key AuxKey
// rand.Read() is protected against short reads
_, err := randRead(key[:])
// On return, n == len(b) if and only if err == nil
return key, err
}
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