gopkg.in/ubuntu-core/snappy.v0@v0.0.0-20210902073436-25a8614f10a6/randutil/crypto.go (about) 1 // -*- Mode: Go; indent-tabs-mode: t -*- 2 3 /* 4 * Copyright (C) 2020 Canonical Ltd 5 * 6 * This program is free software: you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 3 as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program. If not, see <http://www.gnu.org/licenses/>. 17 * 18 */ 19 20 package randutil 21 22 import ( 23 cryptorand "crypto/rand" 24 "encoding/base64" 25 "fmt" 26 "io/ioutil" 27 "strings" 28 ) 29 30 // CryptoTokenBytes returns a crypthographically secure token of 31 // nbytes random bytes. 32 func CryptoTokenBytes(nbytes int) ([]byte, error) { 33 b := make([]byte, nbytes) 34 _, err := cryptorand.Read(b) 35 if err != nil { 36 return nil, fmt.Errorf("cannot obtain %d crypto random bytes: %v", nbytes, err) 37 } 38 return b, nil 39 } 40 41 // CryptoToken returns a crypthographically secure token string 42 // encoding nbytes random bytes. 43 // The result is URL-safe. 44 func CryptoToken(nbytes int) (string, error) { 45 b, err := CryptoTokenBytes(nbytes) 46 if err != nil { 47 return "", err 48 } 49 return base64.RawURLEncoding.EncodeToString(b), nil 50 } 51 52 // RandomKernelUUID will return a UUID from the kernel's procfs API at 53 // /proc/sys/kernel/random/uuid. Only to be used in very specific uses, most 54 // random code should use CryptoToken(Bytes) instead. 55 func RandomKernelUUID() string { 56 b, err := ioutil.ReadFile("/proc/sys/kernel/random/uuid") 57 if err != nil { 58 panic("cannot read kernel generated uuid") 59 } 60 return strings.TrimSpace(string(b)) 61 }