Repository navigation
Expand file tree
/
Copy pathprivate.go
More file actions
397 lines (350 loc) · 11.7 KB
/
Copy pathprivate.go
File metadata and controls
397 lines (350 loc) · 11.7 KB
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
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
// Copyright (c) 2021 Andreas Auernhammer. All rights reserved.
// Use of this source code is governed by a license that can be
// found in the LICENSE file.
package minisign
import (
"crypto"
"crypto/ed25519"
"crypto/rand"
"crypto/subtle"
"encoding/base64"
"encoding/binary"
"errors"
"fmt"
"io"
"os"
"strconv"
"strings"
"time"
"golang.org/x/crypto/blake2b"
"golang.org/x/crypto/scrypt"
)
// PrivateKeyFromFile reads and decrypts the private key
// file with the given password.
func PrivateKeyFromFile(password, path string) (PrivateKey, error) {
bytes, err := os.ReadFile(path)
if err != nil {
return PrivateKey{}, err
}
return DecryptKey(password, bytes)
}
// PrivateKey is a minisign private key.
//
// A private key can sign messages to prove their origin and authenticity.
//
// PrivateKey implements the crypto.Signer interface.
type PrivateKey struct {
_ [0]func() // prevent direct comparison: p1 == p2.
id uint64
bytes [ed25519.PrivateKeySize]byte
}
var _ crypto.Signer = (*PrivateKey)(nil) // compiler check
// ID returns the 64 bit key ID.
func (p PrivateKey) ID() uint64 { return p.id }
// Public returns the corresponding public key.
func (p PrivateKey) Public() crypto.PublicKey {
var bytes [ed25519.PublicKeySize]byte
copy(bytes[:], p.bytes[32:])
return PublicKey{
id: p.ID(),
bytes: bytes,
}
}
// Sign signs the given message.
//
// The minisign signature scheme relies on Ed25519 and supports
// plain as well as pre-hashed messages. Therefore, opts can be
// either crypto.Hash(0) to signal that the message has not been
// hashed or crypto.BLAKE2b_512 to signal that the message is a
// BLAKE2b-512 digest. If opts is crypto.BLAKE2b_512 then message
// must be a 64 bytes long.
//
// Minisign signatures are deterministic such that no randomness
// is necessary.
func (p PrivateKey) Sign(_ io.Reader, message []byte, opts crypto.SignerOpts) (signature []byte, err error) {
var (
trustedComment = "timestamp:" + strconv.FormatInt(time.Now().Unix(), 10)
)
switch h := opts.HashFunc(); h {
case crypto.Hash(0):
const isHashed = false
return sign(p, message, trustedComment, untrustedComment, isHashed), nil
case crypto.BLAKE2b_512:
const isHashed = true
if n := len(message); n != blake2b.Size {
return nil, errors.New("minisign: invalid message length " + strconv.Itoa(n))
}
return sign(p, message, trustedComment, untrustedComment, isHashed), nil
default:
return nil, errors.New("minisign: cannot sign messages hashed with " + strconv.Itoa(int(h)))
}
}
// Equal returns true if and only if p and x have equivalent values.
func (p PrivateKey) Equal(x crypto.PrivateKey) bool {
xx, ok := x.(PrivateKey)
if !ok {
return false
}
return p.id == xx.id && subtle.ConstantTimeCompare(p.bytes[:], xx.bytes[:]) == 1
}
// MarshalText returns a textual representation of the private key.
//
// For password-protected private keys refer to [EncryptKey].
func (p PrivateKey) MarshalText() ([]byte, error) {
// A non-encrypted private key has the same format as an encrypted one.
// However, the salt, and auth. tag are set to all zero.
var b [privateKeySize]byte
binary.LittleEndian.PutUint16(b[:], EdDSA)
binary.LittleEndian.PutUint16(b[2:], algorithmNone)
binary.LittleEndian.PutUint16(b[4:], algorithmBlake2b)
binary.LittleEndian.PutUint64(b[54:], p.id)
copy(b[62:], p.bytes[:])
// It seems odd that the comment says: "encrypted secret key".
// However, the original C implementation behaves like this.
const comment = "untrusted comment: minisign encrypted secret key\n"
encodedBytes := make([]byte, len(comment)+base64.StdEncoding.EncodedLen(len(b)))
copy(encodedBytes, []byte(comment))
base64.StdEncoding.Encode(encodedBytes[len(comment):], b[:])
return encodedBytes, nil
}
// UnmarshalText decodes a textual representation of the private key into p.
//
// It returns an error if the private key is encrypted. For decrypting
// password-protected private keys refer to [DecryptKey].
func (p *PrivateKey) UnmarshalText(text []byte) error {
text = trimUntrustedComment(text)
b := make([]byte, base64.StdEncoding.DecodedLen(len(text)))
n, err := base64.StdEncoding.Decode(b, text)
if err != nil {
return fmt.Errorf("minisign: invalid private key: %v", err)
}
b = b[:n]
if len(b) != privateKeySize {
return errors.New("minisign: invalid private key")
}
var (
kType = binary.LittleEndian.Uint16(b)
kdf = binary.LittleEndian.Uint16(b[2:])
hType = binary.LittleEndian.Uint16(b[4:])
key = b[54:126]
)
if kType != EdDSA {
return fmt.Errorf("minisign: invalid private key: invalid key type '%d'", kType)
}
if kdf == algorithmScrypt {
return errors.New("minisign: private key is encrypted")
}
if kdf != algorithmNone {
return fmt.Errorf("minisign: invalid private key: invalid KDF '%d'", kdf)
}
if hType != algorithmBlake2b {
return fmt.Errorf("minisign: invalid private key: invalid hash type '%d'", hType)
}
p.id = binary.LittleEndian.Uint64(key)
copy(p.bytes[:], key[8:])
return nil
}
const (
algorithmNone = 0x0000 // hex value for KDF when key is not encrypted
algorithmScrypt = 0x6353 // hex value for "Sc"
algorithmBlake2b = 0x3242 // hex value for "B2"
scryptOpsLimit = 0x2000000 // max. Scrypt ops limit based on libsodium
scryptMemLimit = 0x40000000 // max. Scrypt mem limit based on libsodium
privateKeySize = 158 // 2 + 2 + 2 + 32 + 8 + 8 + 104
)
// EncryptKey encrypts the private key with the given password
// using some entropy from the RNG of the OS.
func EncryptKey(password string, privateKey PrivateKey) ([]byte, error) {
var privateKeyBytes [72]byte
binary.LittleEndian.PutUint64(privateKeyBytes[:], privateKey.ID())
copy(privateKeyBytes[8:], privateKey.bytes[:])
var salt [32]byte
if _, err := io.ReadFull(rand.Reader, salt[:]); err != nil {
return nil, err
}
var bytes [privateKeySize]byte
binary.LittleEndian.PutUint16(bytes[0:], EdDSA)
binary.LittleEndian.PutUint16(bytes[2:], algorithmScrypt)
binary.LittleEndian.PutUint16(bytes[4:], algorithmBlake2b)
const ( // TODO(aead): Callers may want to customize the cost parameters
defaultOps = 33554432 // libsodium OPS_LIMIT_SENSITIVE
defaultMem = 1073741824 // libsodium MEM_LIMIT_SENSITIVE
)
copy(bytes[6:38], salt[:])
binary.LittleEndian.PutUint64(bytes[38:], defaultOps)
binary.LittleEndian.PutUint64(bytes[46:], defaultMem)
copy(bytes[54:], encryptKey(password, salt[:], defaultOps, default
8000
Mem, privateKeyBytes[:]))
const comment = "untrusted comment: minisign encrypted secret key\n"
encodedBytes := make([]byte, len(comment)+base64.StdEncoding.EncodedLen(len(bytes)))
copy(encodedBytes, []byte(comment))
base64.StdEncoding.Encode(encodedBytes[len(comment):], bytes[:])
return encodedBytes, nil
}
// IsEncrypted reports whether the private key is encrypted.
func IsEncrypted(privateKey []byte) bool {
privateKey = trimUntrustedComment(privateKey)
bytes := make([]byte, base64.StdEncoding.DecodedLen(len(privateKey)))
n, err := base64.StdEncoding.Decode(bytes, privateKey)
if err != nil {
return false
}
bytes = bytes[:n]
return len(bytes) >= 4 && binary.LittleEndian.Uint16(bytes[2:]) == algorithmScrypt
}
var errDecrypt = errors.New("minisign: decryption failed")
// DecryptKey tries to decrypt the encrypted private key with
// the given password.
func DecryptKey(password string, privateKey []byte) (PrivateKey, error) {
privateKey = trimUntrustedComment(privateKey)
b := make([]byte, base64.StdEncoding.DecodedLen(len(privateKey)))
n, err := base64.StdEncoding.Decode(b, privateKey)
if err != nil {
return PrivateKey{}, err
}
b = b[:n]
if len(b) != privateKeySize {
return PrivateKey{}, errDecrypt
}
var (
kType = binary.LittleEndian.Uint16(b)
kdf = binary.LittleEndian.Uint16(b[2:])
hType = binary.LittleEndian.Uint16(b[4:])
salt = b[6:38]
scryptOps = binary.LittleEndian.Uint64(b[38:])
scryptMem = binary.LittleEndian.Uint64(b[46:])
ciphertext = b[54:]
)
if kType != EdDSA {
return PrivateKey{}, errDecrypt
}
if kdf != algorithmScrypt {
return PrivateKey{}, errDecrypt
}
if hType != algorithmBlake2b {
return PrivateKey{}, errDecrypt
}
if scryptOps > scryptOpsLimit {
return PrivateKey{}, errDecrypt
}
if scryptMem > scryptMemLimit {
return PrivateKey{}, errDecrypt
}
plaintext, err := decryptKey(password, salt, scryptOps, scryptMem, ciphertext)
if err != nil {
return PrivateKey{}, err
}
key := PrivateKey{
id: binary.LittleEndian.Uint64(plaintext),
}
copy(key.bytes[:], plaintext[8:])
return key, nil
}
// encryptKey encrypts the plaintext and returns a ciphertext by:
// 1. tag = BLAKE2b-256(EdDSA-const || plaintext)
// 2. keystream = Scrypt(password, salt, convert(ops, mem))
// 3. ciphertext = (plaintext || tag) ⊕ keystream
//
// Therefore, decryptKey converts the ops and mem cost parameters
// to the (N, r, p)-tuple expected by Scrypt.
//
// The plaintext must be a private key ID concatenated with a raw
// Ed25519 private key, and therefore, 72 bytes long.
func encryptKey(password string, salt []byte, ops, mem uint64, plaintext []byte) []byte {
const (
plaintextLen = 72
messageLen = 74
ciphertextLen = 104
)
N, r, p := convertScryptParameters(ops, mem)
keystream, err := scrypt.Key([]byte(password), salt, N, r, p, ciphertextLen)
if err != nil {
panic(err)
}
var message [messageLen]byte
binary.LittleEndian.PutUint16(message[:2], EdDSA)
copy(message[2:], plaintext)
checksum := blake2b.Sum256(message[:])
var ciphertext [ciphertextLen]byte
copy(ciphertext[:plaintextLen], plaintext)
copy(ciphertext[plaintextLen:], checksum[:])
for i, k := range keystream {
ciphertext[i] ^= k
}
return ciphertext[:]
}
// decryptKey decrypts the ciphertext and returns a plaintext by:
// 1. keystream = Scrypt(password, salt, convert(ops, mem))
// 2. plaintext || tag = ciphertext ⊕ keystream
// 3. Check that: tag == BLAKE2b-256(EdDSA-const || plaintext)
//
// Therefore, decryptKey converts the ops and mem cost parameters to
// the (N, r, p)-tuple expected by Scrypt.
//
// It returns an error if the ciphertext is not valid - i.e. if the
// tag does not match the BLAKE2b-256 hash value.
func decryptKey(password string, salt []byte, ops, mem uint64, ciphertext []byte) ([]byte, error) {
const (
plaintextLen = 72
messageLen = 74
ciphertextLen = 104
)
if len(ciphertext) != ciphertextLen {
return nil, errDecrypt
}
N, r, p := convertScryptParameters(ops, mem)
keystream, err := scrypt.Key([]byte(password), salt, N, r, p, ciphertextLen)
if err != nil {
return nil, err
}
var plaintext [ciphertextLen]byte
for i, k := range keystream {
plaintext[i] = ciphertext[i] ^ k
}
var (
privateKeyBytes = plaintext[:plaintextLen]
checksum = plaintext[plaintextLen:]
)
var message [messageLen]byte
binary.LittleEndian.PutUint16(message[:2], EdDSA)
copy(message[2:], privateKeyBytes)
if sum := blake2b.Sum256(message[:]); subtle.ConstantTimeCompare(sum[:], checksum) != 1 {
return nil, errDecrypt
}
return privateKeyBytes, nil
}
// convertScryptParameters converts the operational and memory cost
// to the Scrypt parameters N, r and p.
//
// N is the overall memory / CPU cost and r * p has to be lower then
// 2³⁰. Refer to the scrypt.Key docs for more information.
func convertScryptParameters(ops, mem uint64) (N, r, p int) {
const (
minOps = 1 << 15
maxRP = 0x3fffffff
)
if ops < minOps {
ops = minOps
}
if ops < mem/32 {
r, p = 8, 1
for n := 1; n < 63; n++ {
if N = 1 << n; uint64(N) > (ops / (8 * uint64(r))) {
break
}
}
} else {
r = 8
for n := 1; n < 63; n++ {
if N = 1 << n; uint64(N) > (mem / (256 * uint64(r))) {
break
}
}
if rp := (ops / 4) / uint64(N); rp < maxRP {
p = int(rp) / r
} else {
p = maxRP / r
}
}
return N, r, p
}