61 lines
1.6 KiB
Go
61 lines
1.6 KiB
Go
// Package siv_aead wraps the functions provided by siv
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// in a crypto.AEAD interface.
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package siv_aead
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import (
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"crypto/cipher"
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"github.com/jacobsa/crypto/siv"
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)
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type sivAead struct {
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key []byte
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}
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var _ cipher.AEAD = &sivAead{}
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// New returns a new cipher.AEAD implementation.
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func New(key []byte) cipher.AEAD {
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return &sivAead{
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key: key,
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}
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}
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func (s *sivAead) NonceSize() int {
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// SIV supports any nonce size, but in gocryptfs we exclusively use 16.
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return 16
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}
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func (s *sivAead) Overhead() int {
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return 16
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}
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// Seal encrypts "in" using "nonce" and "authData" and append the result to "dst"
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func (s *sivAead) Seal(dst, nonce, plaintext, authData []byte) []byte {
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if len(nonce) != 16 {
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// SIV supports any nonce size, but in gocryptfs we exclusively use 16.
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panic("nonce must be 16 bytes long")
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}
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// https://github.com/jacobsa/crypto/blob/master/siv/encrypt.go#L48:
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// As per RFC 5297 section 3, you may use this function for nonce-based
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// authenticated encryption by passing a nonce as the last associated
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// data element.
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associated := [][]byte{authData, nonce}
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out, err := siv.Encrypt(dst, s.key, plaintext, associated)
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if err != nil {
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panic(err)
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}
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return out
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}
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// Open decrypts "in" using "nonce" and "authData" and append the result to "dst"
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func (s *sivAead) Open(dst, nonce, ciphertext, authData []byte) ([]byte, error) {
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if len(nonce) != 16 {
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// SIV supports any nonce size, but in gocryptfs we exclusively use 16.
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panic("nonce must be 16 bytes long")
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}
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associated := [][]byte{authData, nonce}
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dec, err := siv.Decrypt(s.key, ciphertext, associated)
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return append(dst, dec...), err
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}
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