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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
|
// Written in 2015 by Dmitry Chestnykh.
package miscreant
import (
"crypto/cipher"
"crypto/rand"
"io"
)
// Minimum nonce size for which we'll allow the generation of random nonces
const minimumRandomNonceSize = 16
// aead is a wrapper for Cipher implementing cipher.AEAD interface.
type aead struct {
// miscreant.Cipher instance underlying this AEAD
c *Cipher
// Size of the nonce required
nonceSize int
}
// GenerateKey generates a random 32-byte or 64-byte encryption key.
// Panics if the key size is unsupported or source of randomness fails.
func GenerateKey(length int) []byte {
if length != 32 && length != 64 {
panic("miscreant.GenerateKey: invalid key size: " + string(length))
}
key := make([]byte, length)
_, err := io.ReadFull(rand.Reader, key[:])
if err != nil {
panic(err)
}
return key
}
// GenerateNonce generates a random nonce for the given `cipher.AEAD`.
// Panics if the configured nonce size is less than 16-bytes (128-bits)
func GenerateNonce(c cipher.AEAD) []byte {
if c.NonceSize() < minimumRandomNonceSize {
panic("miscreant.GenerateNonce: nonce size is too small: " + string(c.NonceSize()))
}
nonce := make([]byte, c.NonceSize())
_, err := io.ReadFull(rand.Reader, nonce[:])
if err != nil {
panic(err)
}
return nonce
}
// NewAEAD returns an AES-SIV instance implementing cipher.AEAD interface,
// with the given cipher, nonce size, and a key which must be twice as long
// as an AES key, either 32 or 64 bytes to select AES-128 (AES-SIV-256)
// or AES-256 (AES-SIV-512).
//
// Unless the given nonce size is less than zero, Seal and Open will panic when
// passed nonce of a different size.
func NewAEAD(alg string, key []byte, nonceSize int) (cipher.AEAD, error) {
switch alg {
case "AES-SIV", "AES-CMAC-SIV":
c, err := NewAESCMACSIV(key)
if err != nil {
return nil, err
}
return &aead{c: c, nonceSize: nonceSize}, nil
case "AES-PMAC-SIV":
c, err := NewAESPMACSIV(key)
if err != nil {
return nil, err
}
return &aead{c: c, nonceSize: nonceSize}, nil
default:
panic("NewAEAD: unknown cipher: " + alg)
}
}
func (a *aead) NonceSize() int { return a.nonceSize }
func (a *aead) Overhead() int { return a.c.Overhead() }
func (a *aead) Seal(dst, nonce, plaintext, data []byte) (out []byte) {
if len(nonce) != a.nonceSize && a.nonceSize >= 0 {
panic("miscreant.AEAD: incorrect nonce length")
}
var err error
if data == nil {
out, err = a.c.Seal(dst, plaintext, nonce)
} else {
out, err = a.c.Seal(dst, plaintext, data, nonce)
}
if err != nil {
panic("miscreant.AEAD: " + err.Error())
}
return out
}
func (a *aead) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
if len(nonce) != a.nonceSize && a.nonceSize >= 0 {
panic("miscreant.AEAD: incorrect nonce length")
}
if data == nil {
return a.c.Open(dst, ciphertext, nonce)
}
return a.c.Open(dst, ciphertext, data, nonce)
}
|
