blob: 248d6b636c71e5127df524bd81771f129aa22fe5 [file] [log] [blame]
package seed
import (
crand "crypto/rand"
var (
m sync.Mutex
secure int32
seeded int32
func cryptoSeed() error {
defer atomic.StoreInt32(&seeded, 1)
var err error
var n *big.Int
n, err = crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
if err != nil {
return err
atomic.StoreInt32(&secure, 1)
return nil
// Init provides best-effort seeding (which is better than running with Go's
// default seed of 1). If `/dev/urandom` is available, Init() will seed Go's
// runtime with entropy from `/dev/urandom` and return true because the runtime
// was securely seeded. If Init() has already initialized the random number or
// it had failed to securely initialize the random number generation, Init()
// will return false. See MustInit().
func Init() (seededSecurely bool, err error) {
if atomic.LoadInt32(&seeded) == 1 {
return false, nil
// Slow-path
defer m.Unlock()
if err := cryptoSeed(); err != nil {
return false, err
return true, nil
// MustInit provides guaranteed secure seeding. If `/dev/urandom` is not
// available, MustInit will panic() with an error indicating why reading from
// `/dev/urandom` failed. MustInit() will upgrade the seed if for some reason a
// call to Init() failed in the past.
func MustInit() {
if atomic.LoadInt32(&secure) == 1 {
// Slow-path
defer m.Unlock()
if err := cryptoSeed(); err != nil {
panic(fmt.Sprintf("Unable to seed the random number generator: %v", err))
// Secure returns true if a cryptographically secure seed was used to
// initialize rand.
func Secure() bool {
return atomic.LoadInt32(&secure) == 1
// Seeded returns true if Init has seeded the random number generator.
func Seeded() bool {
return atomic.LoadInt32(&seeded) == 1