aboutsummaryrefslogtreecommitdiffhomepage
path: root/vendor/golang.org/x/crypto/bcrypt/bcrypt.go
blob: aeb73f81a14c8567262ecf3f0363c20addabdcfc (plain) (blame)
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
// Copyright 2011 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 bcrypt implements Provos and Mazières's bcrypt adaptive hashing
// algorithm. See http://www.usenix.org/event/usenix99/provos/provos.pdf
package bcrypt // import "golang.org/x/crypto/bcrypt"

// The code is a port of Provos and Mazières's C implementation.
import (
	"crypto/rand"
	"crypto/subtle"
	"errors"
	"fmt"
	"io"
	"strconv"

	"golang.org/x/crypto/blowfish"
)

const (
	MinCost     int = 4  // the minimum allowable cost as passed in to GenerateFromPassword
	MaxCost     int = 31 // the maximum allowable cost as passed in to GenerateFromPassword
	DefaultCost int = 10 // the cost that will actually be set if a cost below MinCost is passed into GenerateFromPassword
)

// The error returned from CompareHashAndPassword when a password and hash do
// not match.
var ErrMismatchedHashAndPassword = errors.New("crypto/bcrypt: hashedPassword is not the hash of the given password")

// The error returned from CompareHashAndPassword when a hash is too short to
// be a bcrypt hash.
var ErrHashTooShort = errors.New("crypto/bcrypt: hashedSecret too short to be a bcrypted password")

// The error returned from CompareHashAndPassword when a hash was created with
// a bcrypt algorithm newer than this implementation.
type HashVersionTooNewError byte

func (hv HashVersionTooNewError) Error() string {
	return fmt.Sprintf("crypto/bcrypt: bcrypt algorithm version '%c' requested is newer than current version '%c'", byte(hv), majorVersion)
}

// The error returned from CompareHashAndPassword when a hash starts with something other than '$'
type InvalidHashPrefixError byte

func (ih InvalidHashPrefixError) Error() string {
	return fmt.Sprintf("crypto/bcrypt: bcrypt hashes must start with '$', but hashedSecret started with '%c'", byte(ih))
}

type InvalidCostError int

func (ic InvalidCostError) Error() string {
	return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), int(MinCost), int(MaxCost))
}

const (
	majorVersion       = '2'
	minorVersion       = 'a'
	maxSaltSize        = 16
	maxCryptedHashSize = 23
	encodedSaltSize    = 22
	encodedHashSize    = 31
	minHashSize        = 59
)

// magicCipherData is an IV for the 64 Blowfish encryption calls in
// bcrypt(). It's the string "OrpheanBeholderScryDoubt" in big-endian bytes.
var magicCipherData = []byte{
	0x4f, 0x72, 0x70, 0x68,
	0x65, 0x61, 0x6e, 0x42,
	0x65, 0x68, 0x6f, 0x6c,
	0x64, 0x65, 0x72, 0x53,
	0x63, 0x72, 0x79, 0x44,
	0x6f, 0x75, 0x62, 0x74,
}

type hashed struct {
	hash  []byte
	salt  []byte
	cost  int // allowed range is MinCost to MaxCost
	major byte
	minor byte
}

// GenerateFromPassword returns the bcrypt hash of the password at the given
// cost. If the cost given is less than MinCost, the cost will be set to
// DefaultCost, instead. Use CompareHashAndPassword, as defined in this package,
// to compare the returned hashed password with its cleartext version.
func GenerateFromPassword(password []byte, cost int) ([]byte, error) {
	p, err := newFromPassword(password, cost)
	if err != nil {
		return nil, err
	}
	return p.Hash(), nil
}

// CompareHashAndPassword compares a bcrypt hashed password with its possible
// plaintext equivalent. Returns nil on success, or an error on failure.
func CompareHashAndPassword(hashedPassword, password []byte) error {
	p, err := newFromHash(hashedPassword)
	if err != nil {
		return err
	}

	otherHash, err := bcrypt(password, p.cost, p.salt)
	if err != nil {
		return err
	}

	otherP := &hashed{otherHash, p.salt, p.cost, p.major, p.minor}
	if subtle.ConstantTimeCompare(p.Hash(), otherP.Hash()) == 1 {
		return nil
	}

	return ErrMismatchedHashAndPassword
}

// Cost returns the hashing cost used to create the given hashed
// password. When, in the future, the hashing cost of a password system needs
// to be increased in order to adjust for greater computational power, this
// function allows one to establish which passwords need to be updated.
func Cost(hashedPassword []byte) (int, error) {
	p, err := newFromHash(hashedPassword)
	if err != nil {
		return 0, err
	}
	return p.cost, nil
}

func newFromPassword(password []byte, cost int) (*hashed, error) {
	if cost < MinCost {
		cost = DefaultCost
	}
	p := new(hashed)
	p.major = majorVersion
	p.minor = minorVersion

	err := checkCost(cost)
	if err != nil {
		return nil, err
	}
	p.cost = cost

	unencodedSalt := make([]byte, maxSaltSize)
	_, err = io.ReadFull(rand.Reader, unencodedSalt)
	if err != nil {
		return nil, err
	}

	p.salt = base64Encode(unencodedSalt)
	hash, err := bcrypt(password, p.cost, p.salt)
	if err != nil {
		return nil, err
	}
	p.hash = hash
	return p, err
}

func newFromHash(hashedSecret []byte) (*hashed, error) {
	if len(hashedSecret) < minHashSize {
		return nil, ErrHashTooShort
	}
	p := new(hashed)
	n, err := p.decodeVersion(hashedSecret)
	if err != nil {
		return nil, err
	}
	hashedSecret = hashedSecret[n:]
	n, err = p.decodeCost(hashedSecret)
	if err != nil {
		return nil, err
	}
	hashedSecret = hashedSecret[n:]

	// The "+2" is here because we'll have to append at most 2 '=' to the salt
	// when base64 decoding it in expensiveBlowfishSetup().
	p.salt = make([]byte, encodedSaltSize, encodedSaltSize+2)
	copy(p.salt, hashedSecret[:encodedSaltSize])

	hashedSecret = hashedSecret[encodedSaltSize:]
	p.hash = make([]byte, len(hashedSecret))
	copy(p.hash, hashedSecret)

	return p, nil
}

func bcrypt(password []byte, cost int, salt []byte) ([]byte, error) {
	cipherData := make([]byte, len(magicCipherData))
	copy(cipherData, magicCipherData)

	c, err := expensiveBlowfishSetup(password, uint32(cost), salt)
	if err != nil {
		return nil, err
	}

	for i := 0; i < 24; i += 8 {
		for j := 0; j < 64; j++ {
			c.Encrypt(cipherData[i:i+8], cipherData[i:i+8])
		}
	}

	// Bug compatibility with C bcrypt implementations. We only encode 23 of
	// the 24 bytes encrypted.
	hsh := base64Encode(cipherData[:maxCryptedHashSize])
	return hsh, nil
}

func expensiveBlowfishSetup(key []byte, cost uint32, salt []byte) (*blowfish.Cipher, error) {
	csalt, err := base64Decode(salt)
	if err != nil {
		return nil, err
	}

	// Bug compatibility with C bcrypt implementations. They use the trailing
	// NULL in the key string during expansion.
	// We copy the key to prevent changing the underlying array.
	ckey := append(key[:len(key):len(key)], 0)

	c, err := blowfish.NewSaltedCipher(ckey, csalt)
	if err != nil {
		return nil, err
	}

	var i, rounds uint64
	rounds = 1 << cost
	for i = 0; i < rounds; i++ {
		blowfish.ExpandKey(ckey, c)
		blowfish.ExpandKey(csalt, c)
	}

	return c, nil
}

func (p *hashed) Hash() []byte {
	arr := make([]byte, 60)
	arr[0] = '$'
	arr[1] = p.major
	n := 2
	if p.minor != 0 {
		arr[2] = p.minor
		n = 3
	}
	arr[n] = '$'
	n++
	copy(arr[n:], []byte(fmt.Sprintf("%02d", p.cost)))
	n += 2
	arr[n] = '$'
	n++
	copy(arr[n:], p.salt)
	n += encodedSaltSize
	copy(arr[n:], p.hash)
	n += encodedHashSize
	return arr[:n]
}

func (p *hashed) decodeVersion(sbytes []byte) (int, error) {
	if sbytes[0] != '$' {
		return -1, InvalidHashPrefixError(sbytes[0])
	}
	if sbytes[1] > majorVersion {
		return -1, HashVersionTooNewError(sbytes[1])
	}
	p.major = sbytes[1]
	n := 3
	if sbytes[2] != '$' {
		p.minor = sbytes[2]
		n++
	}
	return n, nil
}

// sbytes should begin where decodeVersion left off.
func (p *hashed) decodeCost(sbytes []byte) (int, error) {
	cost, err := strconv.Atoi(string(sbytes[0:2]))
	if err != nil {
		return -1, err
	}
	err = checkCost(cost)
	if err != nil {
		return -1, err
	}
	p.cost = cost
	return 3, nil
}

func (p *hashed) String() string {
	return fmt.Sprintf("&{hash: %#v, salt: %#v, cost: %d, major: %c, minor: %c}", string(p.hash), p.salt, p.cost, p.major, p.minor)
}

func checkCost(cost int) error {
	if cost < MinCost || cost > MaxCost {
		return InvalidCostError(cost)
	}
	return nil
}