libgocryptfs/internal/cryptocore/nonce.go

46 lines
971 B
Go

package cryptocore
import (
"bytes"
"crypto/rand"
"encoding/binary"
"encoding/hex"
"fmt"
"log"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// RandBytes gets "n" random bytes from /dev/urandom or panics
func RandBytes(n int) []byte {
b := make([]byte, n)
_, err := rand.Read(b)
if err != nil {
log.Panic("Failed to read random bytes: " + err.Error())
}
return b
}
// RandUint64 returns a secure random uint64
func RandUint64() uint64 {
b := RandBytes(8)
return binary.BigEndian.Uint64(b)
}
type nonceGenerator struct {
lastNonce []byte
nonceLen int // bytes
}
// Get a random "nonceLen"-byte nonce
func (n *nonceGenerator) Get() []byte {
nonce := RandBytes(n.nonceLen)
tlog.Debug.Printf("nonceGenerator.Get(): %s\n", hex.EncodeToString(nonce))
if bytes.Equal(nonce, n.lastNonce) {
m := fmt.Sprintf("Got the same nonce twice: %s. This should never happen!", hex.EncodeToString(nonce))
log.Panic(m)
}
n.lastNonce = nonce
return nonce
}