75 lines
2.3 KiB
Go
75 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
|
||
|
|
|
||
|
|
import (
|
||
|
|
"encoding/binary"
|
||
|
|
|
||
|
|
"golang.org/x/crypto/internal/chacha20"
|
||
|
|
"golang.org/x/crypto/poly1305"
|
||
|
|
)
|
||
|
|
|
||
|
|
func roundTo16(n int) int {
|
||
|
|
return 16 * ((n + 15) / 16)
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *chacha20poly1305) sealGeneric(dst, nonce, plaintext, additionalData []byte) []byte {
|
||
|
|
ret, out := sliceForAppend(dst, len(plaintext)+poly1305.TagSize)
|
||
|
|
|
||
|
|
var polyKey [32]byte
|
||
|
|
s := chacha20.New(c.key, [3]uint32{
|
||
|
|
binary.LittleEndian.Uint32(nonce[0:4]),
|
||
|
|
binary.LittleEndian.Uint32(nonce[4:8]),
|
||
|
|
binary.LittleEndian.Uint32(nonce[8:12]),
|
||
|
|
})
|
||
|
|
s.XORKeyStream(polyKey[:], polyKey[:])
|
||
|
|
s.Advance() // skip the next 32 bytes
|
||
|
|
s.XORKeyStream(out, plaintext)
|
||
|
|
|
||
|
|
polyInput := make([]byte, roundTo16(len(additionalData))+roundTo16(len(plaintext))+8+8)
|
||
|
|
copy(polyInput, additionalData)
|
||
|
|
copy(polyInput[roundTo16(len(additionalData)):], out[:len(plaintext)])
|
||
|
|
binary.LittleEndian.PutUint64(polyInput[len(polyInput)-16:], uint64(len(additionalData)))
|
||
|
|
binary.LittleEndian.PutUint64(polyInput[len(polyInput)-8:], uint64(len(plaintext)))
|
||
|
|
|
||
|
|
var tag [poly1305.TagSize]byte
|
||
|
|
poly1305.Sum(&tag, polyInput, &polyKey)
|
||
|
|
copy(out[len(plaintext):], tag[:])
|
||
|
|
|
||
|
|
return ret
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *chacha20poly1305) openGeneric(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
|
||
|
|
var tag [poly1305.TagSize]byte
|
||
|
|
copy(tag[:], ciphertext[len(ciphertext)-16:])
|
||
|
|
ciphertext = ciphertext[:len(ciphertext)-16]
|
||
|
|
|
||
|
|
var polyKey [32]byte
|
||
|
|
s := chacha20.New(c.key, [3]uint32{
|
||
|
|
binary.LittleEndian.Uint32(nonce[0:4]),
|
||
|
|
binary.LittleEndian.Uint32(nonce[4:8]),
|
||
|
|
binary.LittleEndian.Uint32(nonce[8:12]),
|
||
|
|
})
|
||
|
|
s.XORKeyStream(polyKey[:], polyKey[:])
|
||
|
|
s.Advance() // skip the next 32 bytes
|
||
|
|
|
||
|
|
polyInput := make([]byte, roundTo16(len(additionalData))+roundTo16(len(ciphertext))+8+8)
|
||
|
|
copy(polyInput, additionalData)
|
||
|
|
copy(polyInput[roundTo16(len(additionalData)):], ciphertext)
|
||
|
|
binary.LittleEndian.PutUint64(polyInput[len(polyInput)-16:], uint64(len(additionalData)))
|
||
|
|
binary.LittleEndian.PutUint64(polyInput[len(polyInput)-8:], uint64(len(ciphertext)))
|
||
|
|
|
||
|
|
ret, out := sliceForAppend(dst, len(ciphertext))
|
||
|
|
if !poly1305.Verify(&tag, polyInput, &polyKey) {
|
||
|
|
for i := range out {
|
||
|
|
out[i] = 0
|
||
|
|
}
|
||
|
|
return nil, errOpen
|
||
|
|
}
|
||
|
|
|
||
|
|
s.XORKeyStream(out, ciphertext)
|
||
|
|
return ret, nil
|
||
|
|
}
|