mirror of
https://github.com/restic/restic.git
synced 2024-09-09 04:40:07 +02:00
84 lines
2.3 KiB
Go
84 lines
2.3 KiB
Go
|
// Copyright 2016 The Go Authors. All rights reserved.
|
||
|
// Use of this source code is governed by a BSD-style
|
||
|
// license that can be found in the LICENSE file.
|
||
|
|
||
|
// Package chacha20poly1305 implements the ChaCha20-Poly1305 AEAD as specified in RFC 7539.
|
||
|
package chacha20poly1305 // import "golang.org/x/crypto/chacha20poly1305"
|
||
|
|
||
|
import (
|
||
|
"crypto/cipher"
|
||
|
"errors"
|
||
|
)
|
||
|
|
||
|
const (
|
||
|
// KeySize is the size of the key used by this AEAD, in bytes.
|
||
|
KeySize = 32
|
||
|
// NonceSize is the size of the nonce used with this AEAD, in bytes.
|
||
|
NonceSize = 12
|
||
|
)
|
||
|
|
||
|
type chacha20poly1305 struct {
|
||
|
key [32]byte
|
||
|
}
|
||
|
|
||
|
// New returns a ChaCha20-Poly1305 AEAD that uses the given, 256-bit key.
|
||
|
func New(key []byte) (cipher.AEAD, error) {
|
||
|
if len(key) != KeySize {
|
||
|
return nil, errors.New("chacha20poly1305: bad key length")
|
||
|
}
|
||
|
ret := new(chacha20poly1305)
|
||
|
copy(ret.key[:], key)
|
||
|
return ret, nil
|
||
|
}
|
||
|
|
||
|
func (c *chacha20poly1305) NonceSize() int {
|
||
|
return NonceSize
|
||
|
}
|
||
|
|
||
|
func (c *chacha20poly1305) Overhead() int {
|
||
|
return 16
|
||
|
}
|
||
|
|
||
|
func (c *chacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
|
||
|
if len(nonce) != NonceSize {
|
||
|
panic("chacha20poly1305: bad nonce length passed to Seal")
|
||
|
}
|
||
|
|
||
|
if uint64(len(plaintext)) > (1<<38)-64 {
|
||
|
panic("chacha20poly1305: plaintext too large")
|
||
|
}
|
||
|
|
||
|
return c.seal(dst, nonce, plaintext, additionalData)
|
||
|
}
|
||
|
|
||
|
var errOpen = errors.New("chacha20poly1305: message authentication failed")
|
||
|
|
||
|
func (c *chacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
|
||
|
if len(nonce) != NonceSize {
|
||
|
panic("chacha20poly1305: bad nonce length passed to Open")
|
||
|
}
|
||
|
if len(ciphertext) < 16 {
|
||
|
return nil, errOpen
|
||
|
}
|
||
|
if uint64(len(ciphertext)) > (1<<38)-48 {
|
||
|
panic("chacha20poly1305: ciphertext too large")
|
||
|
}
|
||
|
|
||
|
return c.open(dst, nonce, ciphertext, additionalData)
|
||
|
}
|
||
|
|
||
|
// sliceForAppend takes a slice and a requested number of bytes. It returns a
|
||
|
// slice with the contents of the given slice followed by that many bytes and a
|
||
|
// second slice that aliases into it and contains only the extra bytes. If the
|
||
|
// original slice has sufficient capacity then no allocation is performed.
|
||
|
func sliceForAppend(in []byte, n int) (head, tail []byte) {
|
||
|
if total := len(in) + n; cap(in) >= total {
|
||
|
head = in[:total]
|
||
|
} else {
|
||
|
head = make([]byte, total)
|
||
|
copy(head, in)
|
||
|
}
|
||
|
tail = head[len(in):]
|
||
|
return
|
||
|
}
|