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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2020 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 randutil
import (
cryptorand "crypto/rand"
"encoding/base64"
"fmt"
"os"
"strings"
)
// CryptoTokenBytes returns a crypthographically secure token of
// nbytes random bytes.
func CryptoTokenBytes(nbytes int) ([]byte, error) {
b := make([]byte, nbytes)
_, err := cryptorand.Read(b)
if err != nil {
return nil, fmt.Errorf("cannot obtain %d crypto random bytes: %v", nbytes, err)
}
return b, nil
}
// CryptoToken returns a crypthographically secure token string
// encoding nbytes random bytes.
// The result is URL-safe.
func CryptoToken(nbytes int) (string, error) {
b, err := CryptoTokenBytes(nbytes)
if err != nil {
return "", err
}
return base64.RawURLEncoding.EncodeToString(b), nil
}
// Allow mocking of the path through an exported reference.
var kernelUUIDPath = "/proc/sys/kernel/random/uuid"
// RandomKernelUUID will return a UUID from the kernel's procfs API at
// /proc/sys/kernel/random/uuid. Only to be used in very specific uses, most
// random code should use CryptoToken(Bytes) instead.
func RandomKernelUUID() (string, error) {
b, err := os.ReadFile(kernelUUIDPath)
if err != nil {
return "", fmt.Errorf("cannot read kernel generated uuid: %w", err)
}
return strings.TrimSpace(string(b)), nil
}
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