1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package chacha20poly1305
import (
"bytes"
"fmt"
"github.com/tink-crypto/tink-go/v2/insecuresecretdataaccess"
"github.com/tink-crypto/tink-go/v2/internal/aead"
"github.com/tink-crypto/tink-go/v2/key"
"github.com/tink-crypto/tink-go/v2/subtle/random"
"github.com/tink-crypto/tink-go/v2/tink"
)
type fullAEAD struct {
rawAEAD *aead.ChaCha20Poly1305InsecureNonce
prefix []byte
variant Variant
}
var _ tink.AEAD = (*fullAEAD)(nil)
func newAEAD(key *Key) (tink.AEAD, error) {
rawAEAD, err := aead.NewChaCha20Poly1305InsecureNonce(key.KeyBytes().Data(insecuresecretdataaccess.Token{}))
if err != nil {
return nil, fmt.Errorf("chacha20_poly1305: %w", err)
}
return &fullAEAD{
rawAEAD: rawAEAD,
prefix: key.OutputPrefix(),
variant: key.parameters.Variant(),
}, nil
}
// Encrypt encrypts plaintext with associatedData.
func (ca *fullAEAD) Encrypt(plaintext []byte, associatedData []byte) ([]byte, error) {
nonce := random.GetRandomBytes(aead.ChaCha20Poly1305InsecureNonceSize)
ciphertext := make([]byte, 0, len(ca.prefix)+len(nonce)+len(plaintext)+aead.ChaCha20Poly1305InsecureTagSize)
ciphertext = append(ciphertext, ca.prefix...)
ciphertext = append(ciphertext, nonce...)
ciphertext, err := ca.rawAEAD.Encrypt(ciphertext, nonce, plaintext, associatedData)
if err != nil {
return nil, fmt.Errorf("chacha20_poly1305: encryption failed: %w", err)
}
return ciphertext, nil
}
// Decrypt decrypts ciphertext with associatedData.
func (ca *fullAEAD) Decrypt(ciphertext []byte, associatedData []byte) ([]byte, error) {
if !bytes.HasPrefix(ciphertext, ca.prefix) {
return nil, fmt.Errorf("chacha20_poly1305: ciphertext has invalid prefix")
}
ciphertextNoPrefix := ciphertext[len(ca.prefix):]
minCiphertextLength := aead.ChaCha20Poly1305InsecureNonceSize + aead.ChaCha20Poly1305InsecureTagSize
if len(ciphertextNoPrefix) < minCiphertextLength {
return nil, fmt.Errorf("chacha20_poly1305: ciphertext is too short: got %d, want at least %d", len(ciphertextNoPrefix), minCiphertextLength)
}
nonce := ciphertextNoPrefix[:aead.ChaCha20Poly1305InsecureNonceSize]
ciphertextAndTag := ciphertextNoPrefix[aead.ChaCha20Poly1305InsecureNonceSize:]
plaintext, err := ca.rawAEAD.Decrypt(nonce, ciphertextAndTag, associatedData)
if err != nil {
return nil, err
}
return plaintext, nil
}
func primitiveConstructor(key key.Key) (any, error) {
that, ok := key.(*Key)
if !ok {
return nil, fmt.Errorf("key is not a *chacha20poly1305.Key")
}
return newAEAD(that)
}
|
