forked from TrueCloudLab/distribution
82 lines
2.2 KiB
Go
82 lines
2.2 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
|
||
|
|
|
||
|
|
import (
|
||
|
|
"encoding/binary"
|
||
|
|
|
||
|
|
"golang.org/x/crypto/chacha20"
|
||
|
|
"golang.org/x/crypto/internal/alias"
|
||
|
|
"golang.org/x/crypto/internal/poly1305"
|
||
|
|
)
|
||
|
|
|
||
|
|
func writeWithPadding(p *poly1305.MAC, b []byte) {
|
||
|
|
p.Write(b)
|
||
|
|
if rem := len(b) % 16; rem != 0 {
|
||
|
|
var buf [16]byte
|
||
|
|
padLen := 16 - rem
|
||
|
|
p.Write(buf[:padLen])
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func writeUint64(p *poly1305.MAC, n int) {
|
||
|
|
var buf [8]byte
|
||
|
|
binary.LittleEndian.PutUint64(buf[:], uint64(n))
|
||
|
|
p.Write(buf[:])
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *chacha20poly1305) sealGeneric(dst, nonce, plaintext, additionalData []byte) []byte {
|
||
|
|
ret, out := sliceForAppend(dst, len(plaintext)+poly1305.TagSize)
|
||
|
|
ciphertext, tag := out[:len(plaintext)], out[len(plaintext):]
|
||
|
|
if alias.InexactOverlap(out, plaintext) {
|
||
|
|
panic("chacha20poly1305: invalid buffer overlap")
|
||
|
|
}
|
||
|
|
|
||
|
|
var polyKey [32]byte
|
||
|
|
s, _ := chacha20.NewUnauthenticatedCipher(c.key[:], nonce)
|
||
|
|
s.XORKeyStream(polyKey[:], polyKey[:])
|
||
|
|
s.SetCounter(1) // set the counter to 1, skipping 32 bytes
|
||
|
|
s.XORKeyStream(ciphertext, plaintext)
|
||
|
|
|
||
|
|
p := poly1305.New(&polyKey)
|
||
|
|
writeWithPadding(p, additionalData)
|
||
|
|
writeWithPadding(p, ciphertext)
|
||
|
|
writeUint64(p, len(additionalData))
|
||
|
|
writeUint64(p, len(plaintext))
|
||
|
|
p.Sum(tag[:0])
|
||
|
|
|
||
|
|
return ret
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *chacha20poly1305) openGeneric(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
|
||
|
|
tag := ciphertext[len(ciphertext)-16:]
|
||
|
|
ciphertext = ciphertext[:len(ciphertext)-16]
|
||
|
|
|
||
|
|
var polyKey [32]byte
|
||
|
|
s, _ := chacha20.NewUnauthenticatedCipher(c.key[:], nonce)
|
||
|
|
s.XORKeyStream(polyKey[:], polyKey[:])
|
||
|
|
s.SetCounter(1) // set the counter to 1, skipping 32 bytes
|
||
|
|
|
||
|
|
p := poly1305.New(&polyKey)
|
||
|
|
writeWithPadding(p, additionalData)
|
||
|
|
writeWithPadding(p, ciphertext)
|
||
|
|
writeUint64(p, len(additionalData))
|
||
|
|
writeUint64(p, len(ciphertext))
|
||
|
|
|
||
|
|
ret, out := sliceForAppend(dst, len(ciphertext))
|
||
|
|
if alias.InexactOverlap(out, ciphertext) {
|
||
|
|
panic("chacha20poly1305: invalid buffer overlap")
|
||
|
|
}
|
||
|
|
if !p.Verify(tag) {
|
||
|
|
for i := range out {
|
||
|
|
out[i] = 0
|
||
|
|
}
|
||
|
|
return nil, errOpen
|
||
|
|
}
|
||
|
|
|
||
|
|
s.XORKeyStream(out, ciphertext)
|
||
|
|
return ret, nil
|
||
|
|
}
|