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package cryptfs
import (
"encoding/binary"
"encoding/hex"
"sync"
"crypto/rand"
)
type nonce96 struct {
lock sync.Mutex
high32 uint32
low64 uint64
ready int
}
var gcmNonce nonce96
// Get "n" random bytes from /dev/urandom or panic
func RandBytes(n int) []byte {
b := make([]byte, n)
_, err := rand.Read(b)
if err != nil {
panic("Could not get random bytes for nonce")
}
return b
}
func (n *nonce96) init() {
b := RandBytes(8)
n.low64 = binary.BigEndian.Uint64(b)
b = RandBytes(4)
n.high32 = binary.BigEndian.Uint32(b)
n.ready = 1
return
}
func (n *nonce96) Get() []byte {
n.lock.Lock()
if n.ready == 0 {
n.init()
}
n.low64++
if n.low64 == 0 {
// Counter has wrapped
n.high32++
}
r := make([]byte, 12)
binary.BigEndian.PutUint32(r[0:4], n.high32)
binary.BigEndian.PutUint64(r[4:12], n.low64)
n.lock.Unlock()
Debug.Printf("nonce96.Get(): %s\n", hex.EncodeToString(r))
return r
}
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