forked from 742481030/rclone
/
cipher.go
1054 lines (951 loc) · 27.8 KB
/
cipher.go
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
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
package crypt
import (
"bytes"
"context"
"crypto/aes"
gocipher "crypto/cipher"
"crypto/rand"
"encoding/base32"
"fmt"
"io"
"strconv"
"strings"
"sync"
"unicode/utf8"
"github.com/pkg/errors"
"github.com/rclone/rclone/backend/crypt/pkcs7"
"github.com/rclone/rclone/fs"
"github.com/rclone/rclone/fs/accounting"
"github.com/rfjakob/eme"
"golang.org/x/crypto/nacl/secretbox"
"golang.org/x/crypto/scrypt"
)
// Constants
const (
nameCipherBlockSize = aes.BlockSize
fileMagic = "RCLONE\x00\x00"
fileMagicSize = len(fileMagic)
fileNonceSize = 24
fileHeaderSize = fileMagicSize + fileNonceSize
blockHeaderSize = secretbox.Overhead
blockDataSize = 64 * 1024
blockSize = blockHeaderSize + blockDataSize
encryptedSuffix = ".bin" // when file name encryption is off we add this suffix to make sure the cloud provider doesn't process the file
)
// Errors returned by cipher
var (
ErrorBadDecryptUTF8 = errors.New("bad decryption - utf-8 invalid")
ErrorBadDecryptControlChar = errors.New("bad decryption - contains control chars")
ErrorNotAMultipleOfBlocksize = errors.New("not a multiple of blocksize")
ErrorTooShortAfterDecode = errors.New("too short after base32 decode")
ErrorTooLongAfterDecode = errors.New("too long after base32 decode")
ErrorEncryptedFileTooShort = errors.New("file is too short to be encrypted")
ErrorEncryptedFileBadHeader = errors.New("file has truncated block header")
ErrorEncryptedBadMagic = errors.New("not an encrypted file - bad magic string")
ErrorEncryptedBadBlock = errors.New("failed to authenticate decrypted block - bad password?")
ErrorBadBase32Encoding = errors.New("bad base32 filename encoding")
ErrorFileClosed = errors.New("file already closed")
ErrorNotAnEncryptedFile = errors.New("not an encrypted file - no \"" + encryptedSuffix + "\" suffix")
ErrorBadSeek = errors.New("Seek beyond end of file")
defaultSalt = []byte{0xA8, 0x0D, 0xF4, 0x3A, 0x8F, 0xBD, 0x03, 0x08, 0xA7, 0xCA, 0xB8, 0x3E, 0x58, 0x1F, 0x86, 0xB1}
obfuscQuoteRune = '!'
)
// Global variables
var (
fileMagicBytes = []byte(fileMagic)
)
// ReadSeekCloser is the interface of the read handles
type ReadSeekCloser interface {
io.Reader
io.Seeker
io.Closer
fs.RangeSeeker
}
// OpenRangeSeek opens the file handle at the offset with the limit given
type OpenRangeSeek func(ctx context.Context, offset, limit int64) (io.ReadCloser, error)
// NameEncryptionMode is the type of file name encryption in use
type NameEncryptionMode int
// NameEncryptionMode levels
const (
NameEncryptionOff NameEncryptionMode = iota
NameEncryptionStandard
NameEncryptionObfuscated
)
// NewNameEncryptionMode turns a string into a NameEncryptionMode
func NewNameEncryptionMode(s string) (mode NameEncryptionMode, err error) {
s = strings.ToLower(s)
switch s {
case "off":
mode = NameEncryptionOff
case "standard":
mode = NameEncryptionStandard
case "obfuscate":
mode = NameEncryptionObfuscated
default:
err = errors.Errorf("Unknown file name encryption mode %q", s)
}
return mode, err
}
// String turns mode into a human readable string
func (mode NameEncryptionMode) String() (out string) {
switch mode {
case NameEncryptionOff:
out = "off"
case NameEncryptionStandard:
out = "standard"
case NameEncryptionObfuscated:
out = "obfuscate"
default:
out = fmt.Sprintf("Unknown mode #%d", mode)
}
return out
}
// Cipher defines an encoding and decoding cipher for the crypt backend
type Cipher struct {
dataKey [32]byte // Key for secretbox
nameKey [32]byte // 16,24 or 32 bytes
nameTweak [nameCipherBlockSize]byte // used to tweak the name crypto
block gocipher.Block
mode NameEncryptionMode
buffers sync.Pool // encrypt/decrypt buffers
cryptoRand io.Reader // read crypto random numbers from here
dirNameEncrypt bool
}
// newCipher initialises the cipher. If salt is "" then it uses a built in salt val
func newCipher(mode NameEncryptionMode, password, salt string, dirNameEncrypt bool) (*Cipher, error) {
c := &Cipher{
mode: mode,
cryptoRand: rand.Reader,
dirNameEncrypt: dirNameEncrypt,
}
c.buffers.New = func() interface{} {
return make([]byte, blockSize)
}
err := c.Key(password, salt)
if err != nil {
return nil, err
}
return c, nil
}
// Key creates all the internal keys from the password passed in using
// scrypt.
//
// If salt is "" we use a fixed salt just to make attackers lives
// slighty harder than using no salt.
//
// Note that empty passsword makes all 0x00 keys which is used in the
// tests.
func (c *Cipher) Key(password, salt string) (err error) {
const keySize = len(c.dataKey) + len(c.nameKey) + len(c.nameTweak)
var saltBytes = defaultSalt
if salt != "" {
saltBytes = []byte(salt)
}
var key []byte
if password == "" {
key = make([]byte, keySize)
} else {
key, err = scrypt.Key([]byte(password), saltBytes, 16384, 8, 1, keySize)
if err != nil {
return err
}
}
copy(c.dataKey[:], key)
copy(c.nameKey[:], key[len(c.dataKey):])
copy(c.nameTweak[:], key[len(c.dataKey)+len(c.nameKey):])
// Key the name cipher
c.block, err = aes.NewCipher(c.nameKey[:])
return err
}
// getBlock gets a block from the pool of size blockSize
func (c *Cipher) getBlock() []byte {
return c.buffers.Get().([]byte)
}
// putBlock returns a block to the pool of size blockSize
func (c *Cipher) putBlock(buf []byte) {
if len(buf) != blockSize {
panic("bad blocksize returned to pool")
}
c.buffers.Put(buf)
}
// encodeFileName encodes a filename using a modified version of
// standard base32 as described in RFC4648
//
// The standard encoding is modified in two ways
// * it becomes lower case (no-one likes upper case filenames!)
// * we strip the padding character `=`
func encodeFileName(in []byte) string {
encoded := base32.HexEncoding.EncodeToString(in)
encoded = strings.TrimRight(encoded, "=")
return strings.ToLower(encoded)
}
// decodeFileName decodes a filename as encoded by encodeFileName
func decodeFileName(in string) ([]byte, error) {
if strings.HasSuffix(in, "=") {
return nil, ErrorBadBase32Encoding
}
// First figure out how many padding characters to add
roundUpToMultipleOf8 := (len(in) + 7) &^ 7
equals := roundUpToMultipleOf8 - len(in)
in = strings.ToUpper(in) + "========"[:equals]
return base32.HexEncoding.DecodeString(in)
}
// encryptSegment encrypts a path segment
//
// This uses EME with AES
//
// EME (ECB-Mix-ECB) is a wide-block encryption mode presented in the
// 2003 paper "A Parallelizable Enciphering Mode" by Halevi and
// Rogaway.
//
// This makes for deterministic encryption which is what we want - the
// same filename must encrypt to the same thing.
//
// This means that
// * filenames with the same name will encrypt the same
// * filenames which start the same won't have a common prefix
func (c *Cipher) encryptSegment(plaintext string) string {
if plaintext == "" {
return ""
}
paddedPlaintext := pkcs7.Pad(nameCipherBlockSize, []byte(plaintext))
ciphertext := eme.Transform(c.block, c.nameTweak[:], paddedPlaintext, eme.DirectionEncrypt)
return encodeFileName(ciphertext)
}
// decryptSegment decrypts a path segment
func (c *Cipher) decryptSegment(ciphertext string) (string, error) {
if ciphertext == "" {
return "", nil
}
rawCiphertext, err := decodeFileName(ciphertext)
if err != nil {
return "", err
}
if len(rawCiphertext)%nameCipherBlockSize != 0 {
return "", ErrorNotAMultipleOfBlocksize
}
if len(rawCiphertext) == 0 {
// not possible if decodeFilename() working correctly
return "", ErrorTooShortAfterDecode
}
if len(rawCiphertext) > 2048 {
return "", ErrorTooLongAfterDecode
}
paddedPlaintext := eme.Transform(c.block, c.nameTweak[:], rawCiphertext, eme.DirectionDecrypt)
plaintext, err := pkcs7.Unpad(nameCipherBlockSize, paddedPlaintext)
if err != nil {
return "", err
}
return string(plaintext), err
}
// Simple obfuscation routines
func (c *Cipher) obfuscateSegment(plaintext string) string {
if plaintext == "" {
return ""
}
// If the string isn't valid UTF8 then don't rotate; just
// prepend a !.
if !utf8.ValidString(plaintext) {
return "!." + plaintext
}
// Calculate a simple rotation based on the filename and
// the nameKey
var dir int
for _, runeValue := range plaintext {
dir += int(runeValue)
}
dir = dir % 256
// We'll use this number to store in the result filename...
var result bytes.Buffer
_, _ = result.WriteString(strconv.Itoa(dir) + ".")
// but we'll augment it with the nameKey for real calculation
for i := 0; i < len(c.nameKey); i++ {
dir += int(c.nameKey[i])
}
// Now for each character, depending on the range it is in
// we will actually rotate a different amount
for _, runeValue := range plaintext {
switch {
case runeValue == obfuscQuoteRune:
// Quote the Quote character
_, _ = result.WriteRune(obfuscQuoteRune)
_, _ = result.WriteRune(obfuscQuoteRune)
case runeValue >= '0' && runeValue <= '9':
// Number
thisdir := (dir % 9) + 1
newRune := '0' + (int(runeValue)-'0'+thisdir)%10
_, _ = result.WriteRune(rune(newRune))
case (runeValue >= 'A' && runeValue <= 'Z') ||
(runeValue >= 'a' && runeValue <= 'z'):
// ASCII letter. Try to avoid trivial A->a mappings
thisdir := dir%25 + 1
// Calculate the offset of this character in A-Za-z
pos := int(runeValue - 'A')
if pos >= 26 {
pos -= 6 // It's lower case
}
// Rotate the character to the new location
pos = (pos + thisdir) % 52
if pos >= 26 {
pos += 6 // and handle lower case offset again
}
_, _ = result.WriteRune(rune('A' + pos))
case runeValue >= 0xA0 && runeValue <= 0xFF:
// Latin 1 supplement
thisdir := (dir % 95) + 1
newRune := 0xA0 + (int(runeValue)-0xA0+thisdir)%96
_, _ = result.WriteRune(rune(newRune))
case runeValue >= 0x100:
// Some random Unicode range; we have no good rules here
thisdir := (dir % 127) + 1
base := int(runeValue - runeValue%256)
newRune := rune(base + (int(runeValue)-base+thisdir)%256)
// If the new character isn't a valid UTF8 char
// then don't rotate it. Quote it instead
if !utf8.ValidRune(newRune) {
_, _ = result.WriteRune(obfuscQuoteRune)
_, _ = result.WriteRune(runeValue)
} else {
_, _ = result.WriteRune(newRune)
}
default:
// Leave character untouched
_, _ = result.WriteRune(runeValue)
}
}
return result.String()
}
func (c *Cipher) deobfuscateSegment(ciphertext string) (string, error) {
if ciphertext == "" {
return "", nil
}
pos := strings.Index(ciphertext, ".")
if pos == -1 {
return "", ErrorNotAnEncryptedFile
} // No .
num := ciphertext[:pos]
if num == "!" {
// No rotation; probably original was not valid unicode
return ciphertext[pos+1:], nil
}
dir, err := strconv.Atoi(num)
if err != nil {
return "", ErrorNotAnEncryptedFile // Not a number
}
// add the nameKey to get the real rotate distance
for i := 0; i < len(c.nameKey); i++ {
dir += int(c.nameKey[i])
}
var result bytes.Buffer
inQuote := false
for _, runeValue := range ciphertext[pos+1:] {
switch {
case inQuote:
_, _ = result.WriteRune(runeValue)
inQuote = false
case runeValue == obfuscQuoteRune:
inQuote = true
case runeValue >= '0' && runeValue <= '9':
// Number
thisdir := (dir % 9) + 1
newRune := '0' + int(runeValue) - '0' - thisdir
if newRune < '0' {
newRune += 10
}
_, _ = result.WriteRune(rune(newRune))
case (runeValue >= 'A' && runeValue <= 'Z') ||
(runeValue >= 'a' && runeValue <= 'z'):
thisdir := dir%25 + 1
pos := int(runeValue - 'A')
if pos >= 26 {
pos -= 6
}
pos = pos - thisdir
if pos < 0 {
pos += 52
}
if pos >= 26 {
pos += 6
}
_, _ = result.WriteRune(rune('A' + pos))
case runeValue >= 0xA0 && runeValue <= 0xFF:
thisdir := (dir % 95) + 1
newRune := 0xA0 + int(runeValue) - 0xA0 - thisdir
if newRune < 0xA0 {
newRune += 96
}
_, _ = result.WriteRune(rune(newRune))
case runeValue >= 0x100:
thisdir := (dir % 127) + 1
base := int(runeValue - runeValue%256)
newRune := rune(base + (int(runeValue) - base - thisdir))
if int(newRune) < base {
newRune += 256
}
_, _ = result.WriteRune(newRune)
default:
_, _ = result.WriteRune(runeValue)
}
}
return result.String(), nil
}
// encryptFileName encrypts a file path
func (c *Cipher) encryptFileName(in string) string {
segments := strings.Split(in, "/")
for i := range segments {
// Skip directory name encryption if the user chose to
// leave them intact
if !c.dirNameEncrypt && i != (len(segments)-1) {
continue
}
if c.mode == NameEncryptionStandard {
segments[i] = c.encryptSegment(segments[i])
} else {
segments[i] = c.obfuscateSegment(segments[i])
}
}
return strings.Join(segments, "/")
}
// EncryptFileName encrypts a file path
func (c *Cipher) EncryptFileName(in string) string {
if c.mode == NameEncryptionOff {
return in + encryptedSuffix
}
return c.encryptFileName(in)
}
// EncryptDirName encrypts a directory path
func (c *Cipher) EncryptDirName(in string) string {
if c.mode == NameEncryptionOff || !c.dirNameEncrypt {
return in
}
return c.encryptFileName(in)
}
// decryptFileName decrypts a file path
func (c *Cipher) decryptFileName(in string) (string, error) {
segments := strings.Split(in, "/")
for i := range segments {
var err error
// Skip directory name decryption if the user chose to
// leave them intact
if !c.dirNameEncrypt && i != (len(segments)-1) {
continue
}
if c.mode == NameEncryptionStandard {
segments[i], err = c.decryptSegment(segments[i])
} else {
segments[i], err = c.deobfuscateSegment(segments[i])
}
if err != nil {
return "", err
}
}
return strings.Join(segments, "/"), nil
}
// DecryptFileName decrypts a file path
func (c *Cipher) DecryptFileName(in string) (string, error) {
if c.mode == NameEncryptionOff {
remainingLength := len(in) - len(encryptedSuffix)
if remainingLength > 0 && strings.HasSuffix(in, encryptedSuffix) {
return in[:remainingLength], nil
}
return "", ErrorNotAnEncryptedFile
}
return c.decryptFileName(in)
}
// DecryptDirName decrypts a directory path
func (c *Cipher) DecryptDirName(in string) (string, error) {
if c.mode == NameEncryptionOff || !c.dirNameEncrypt {
return in, nil
}
return c.decryptFileName(in)
}
// NameEncryptionMode returns the encryption mode in use for names
func (c *Cipher) NameEncryptionMode() NameEncryptionMode {
return c.mode
}
// nonce is an NACL secretbox nonce
type nonce [fileNonceSize]byte
// pointer returns the nonce as a *[24]byte for secretbox
func (n *nonce) pointer() *[fileNonceSize]byte {
return (*[fileNonceSize]byte)(n)
}
// fromReader fills the nonce from an io.Reader - normally the OSes
// crypto random number generator
func (n *nonce) fromReader(in io.Reader) error {
read, err := io.ReadFull(in, (*n)[:])
if read != fileNonceSize {
return errors.Wrap(err, "short read of nonce")
}
return nil
}
// fromBuf fills the nonce from the buffer passed in
func (n *nonce) fromBuf(buf []byte) {
read := copy((*n)[:], buf)
if read != fileNonceSize {
panic("buffer to short to read nonce")
}
}
// carry 1 up the nonce from position i
func (n *nonce) carry(i int) {
for ; i < len(*n); i++ {
digit := (*n)[i]
newDigit := digit + 1
(*n)[i] = newDigit
if newDigit >= digit {
// exit if no carry
break
}
}
}
// increment to add 1 to the nonce
func (n *nonce) increment() {
n.carry(0)
}
// add a uint64 to the nonce
func (n *nonce) add(x uint64) {
carry := uint16(0)
for i := 0; i < 8; i++ {
digit := (*n)[i]
xDigit := byte(x)
x >>= 8
carry += uint16(digit) + uint16(xDigit)
(*n)[i] = byte(carry)
carry >>= 8
}
if carry != 0 {
n.carry(8)
}
}
// encrypter encrypts an io.Reader on the fly
type encrypter struct {
mu sync.Mutex
in io.Reader
c *Cipher
nonce nonce
buf []byte
readBuf []byte
bufIndex int
bufSize int
err error
}
// newEncrypter creates a new file handle encrypting on the fly
func (c *Cipher) newEncrypter(in io.Reader, nonce *nonce) (*encrypter, error) {
fh := &encrypter{
in: in,
c: c,
buf: c.getBlock(),
readBuf: c.getBlock(),
bufSize: fileHeaderSize,
}
// Initialise nonce
if nonce != nil {
fh.nonce = *nonce
} else {
err := fh.nonce.fromReader(c.cryptoRand)
if err != nil {
return nil, err
}
}
// Copy magic into buffer
copy(fh.buf, fileMagicBytes)
// Copy nonce into buffer
copy(fh.buf[fileMagicSize:], fh.nonce[:])
return fh, nil
}
// Read as per io.Reader
func (fh *encrypter) Read(p []byte) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.err != nil {
return 0, fh.err
}
if fh.bufIndex >= fh.bufSize {
// Read data
// FIXME should overlap the reads with a go-routine and 2 buffers?
readBuf := fh.readBuf[:blockDataSize]
n, err = io.ReadFull(fh.in, readBuf)
if n == 0 {
// err can't be nil since:
// n == len(buf) if and only if err == nil.
return fh.finish(err)
}
// possibly err != nil here, but we will process the
// data and the next call to ReadFull will return 0, err
// Write nonce to start of block
copy(fh.buf, fh.nonce[:])
// Encrypt the block using the nonce
block := fh.buf
secretbox.Seal(block[:0], readBuf[:n], fh.nonce.pointer(), &fh.c.dataKey)
fh.bufIndex = 0
fh.bufSize = blockHeaderSize + n
fh.nonce.increment()
}
n = copy(p, fh.buf[fh.bufIndex:fh.bufSize])
fh.bufIndex += n
return n, nil
}
// finish sets the final error and tidies up
func (fh *encrypter) finish(err error) (int, error) {
if fh.err != nil {
return 0, fh.err
}
fh.err = err
fh.c.putBlock(fh.buf)
fh.buf = nil
fh.c.putBlock(fh.readBuf)
fh.readBuf = nil
return 0, err
}
// Encrypt data encrypts the data stream
func (c *Cipher) encryptData(in io.Reader) (io.Reader, *encrypter, error) {
in, wrap := accounting.UnWrap(in) // unwrap the accounting off the Reader
out, err := c.newEncrypter(in, nil)
if err != nil {
return nil, nil, err
}
return wrap(out), out, nil // and wrap the accounting back on
}
// EncryptData encrypts the data stream
func (c *Cipher) EncryptData(in io.Reader) (io.Reader, error) {
out, _, err := c.encryptData(in)
return out, err
}
// decrypter decrypts an io.ReaderCloser on the fly
type decrypter struct {
mu sync.Mutex
rc io.ReadCloser
nonce nonce
initialNonce nonce
c *Cipher
buf []byte
readBuf []byte
bufIndex int
bufSize int
err error
limit int64 // limit of bytes to read, -1 for unlimited
open OpenRangeSeek
}
// newDecrypter creates a new file handle decrypting on the fly
func (c *Cipher) newDecrypter(rc io.ReadCloser) (*decrypter, error) {
fh := &decrypter{
rc: rc,
c: c,
buf: c.getBlock(),
readBuf: c.getBlock(),
limit: -1,
}
// Read file header (magic + nonce)
readBuf := fh.readBuf[:fileHeaderSize]
_, err := io.ReadFull(fh.rc, readBuf)
if err == io.EOF || err == io.ErrUnexpectedEOF {
// This read from 0..fileHeaderSize-1 bytes
return nil, fh.finishAndClose(ErrorEncryptedFileTooShort)
} else if err != nil {
return nil, fh.finishAndClose(err)
}
// check the magic
if !bytes.Equal(readBuf[:fileMagicSize], fileMagicBytes) {
return nil, fh.finishAndClose(ErrorEncryptedBadMagic)
}
// retrieve the nonce
fh.nonce.fromBuf(readBuf[fileMagicSize:])
fh.initialNonce = fh.nonce
return fh, nil
}
// newDecrypterSeek creates a new file handle decrypting on the fly
func (c *Cipher) newDecrypterSeek(ctx context.Context, open OpenRangeSeek, offset, limit int64) (fh *decrypter, err error) {
var rc io.ReadCloser
doRangeSeek := false
setLimit := false
// Open initially with no seek
if offset == 0 && limit < 0 {
// If no offset or limit then open whole file
rc, err = open(ctx, 0, -1)
} else if offset == 0 {
// If no offset open the header + limit worth of the file
_, underlyingLimit, _, _ := calculateUnderlying(offset, limit)
rc, err = open(ctx, 0, int64(fileHeaderSize)+underlyingLimit)
setLimit = true
} else {
// Otherwise just read the header to start with
rc, err = open(ctx, 0, int64(fileHeaderSize))
doRangeSeek = true
}
if err != nil {
return nil, err
}
// Open the stream which fills in the nonce
fh, err = c.newDecrypter(rc)
if err != nil {
return nil, err
}
fh.open = open // will be called by fh.RangeSeek
if doRangeSeek {
_, err = fh.RangeSeek(ctx, offset, io.SeekStart, limit)
if err != nil {
_ = fh.Close()
return nil, err
}
}
if setLimit {
fh.limit = limit
}
return fh, nil
}
// read data into internal buffer - call with fh.mu held
func (fh *decrypter) fillBuffer() (err error) {
// FIXME should overlap the reads with a go-routine and 2 buffers?
readBuf := fh.readBuf
n, err := io.ReadFull(fh.rc, readBuf)
if n == 0 {
// err can't be nil since:
// n == len(buf) if and only if err == nil.
return err
}
// possibly err != nil here, but we will process the data and
// the next call to ReadFull will return 0, err
// Check header + 1 byte exists
if n <= blockHeaderSize {
if err != nil {
return err // return pending error as it is likely more accurate
}
return ErrorEncryptedFileBadHeader
}
// Decrypt the block using the nonce
block := fh.buf
_, ok := secretbox.Open(block[:0], readBuf[:n], fh.nonce.pointer(), &fh.c.dataKey)
if !ok {
if err != nil {
return err // return pending error as it is likely more accurate
}
return ErrorEncryptedBadBlock
}
fh.bufIndex = 0
fh.bufSize = n - blockHeaderSize
fh.nonce.increment()
return nil
}
// Read as per io.Reader
func (fh *decrypter) Read(p []byte) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.err != nil {
return 0, fh.err
}
if fh.bufIndex >= fh.bufSize {
err = fh.fillBuffer()
if err != nil {
return 0, fh.finish(err)
}
}
toCopy := fh.bufSize - fh.bufIndex
if fh.limit >= 0 && fh.limit < int64(toCopy) {
toCopy = int(fh.limit)
}
n = copy(p, fh.buf[fh.bufIndex:fh.bufIndex+toCopy])
fh.bufIndex += n
if fh.limit >= 0 {
fh.limit -= int64(n)
if fh.limit == 0 {
return n, fh.finish(io.EOF)
}
}
return n, nil
}
// calculateUnderlying converts an (offset, limit) in a crypted file
// into an (underlyingOffset, underlyingLimit) for the underlying
// file.
//
// It also returns number of bytes to discard after reading the first
// block and number of blocks this is from the start so the nonce can
// be incremented.
func calculateUnderlying(offset, limit int64) (underlyingOffset, underlyingLimit, discard, blocks int64) {
// blocks we need to seek, plus bytes we need to discard
blocks, discard = offset/blockDataSize, offset%blockDataSize
// Offset in underlying stream we need to seek
underlyingOffset = int64(fileHeaderSize) + blocks*(blockHeaderSize+blockDataSize)
// work out how many blocks we need to read
underlyingLimit = int64(-1)
if limit >= 0 {
// bytes to read beyond the first block
bytesToRead := limit - (blockDataSize - discard)
// Read the first block
blocksToRead := int64(1)
if bytesToRead > 0 {
// Blocks that need to be read plus left over blocks
extraBlocksToRead, endBytes := bytesToRead/blockDataSize, bytesToRead%blockDataSize
if endBytes != 0 {
// If left over bytes must read another block
extraBlocksToRead++
}
blocksToRead += extraBlocksToRead
}
// Must read a whole number of blocks
underlyingLimit = blocksToRead * (blockHeaderSize + blockDataSize)
}
return
}
// RangeSeek behaves like a call to Seek(offset int64, whence
// int) with the output wrapped in an io.LimitedReader
// limiting the total length to limit.
//
// RangeSeek with a limit of < 0 is equivalent to a regular Seek.
func (fh *decrypter) RangeSeek(ctx context.Context, offset int64, whence int, limit int64) (int64, error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.open == nil {
return 0, fh.finish(errors.New("can't seek - not initialised with newDecrypterSeek"))
}
if whence != io.SeekStart {
return 0, fh.finish(errors.New("can only seek from the start"))
}
// Reset error or return it if not EOF
if fh.err == io.EOF {
fh.unFinish()
} else if fh.err != nil {
return 0, fh.err
}
underlyingOffset, underlyingLimit, discard, blocks := calculateUnderlying(offset, limit)
// Move the nonce on the correct number of blocks from the start
fh.nonce = fh.initialNonce
fh.nonce.add(uint64(blocks))
// Can we seek underlying stream directly?
if do, ok := fh.rc.(fs.RangeSeeker); ok {
// Seek underlying stream directly
_, err := do.RangeSeek(ctx, underlyingOffset, 0, underlyingLimit)
if err != nil {
return 0, fh.finish(err)
}
} else {
// if not reopen with seek
_ = fh.rc.Close() // close underlying file
fh.rc = nil
// Re-open the underlying object with the offset given
rc, err := fh.open(ctx, underlyingOffset, underlyingLimit)
if err != nil {
return 0, fh.finish(errors.Wrap(err, "couldn't reopen file with offset and limit"))
}
// Set the file handle
fh.rc = rc
}
// Fill the buffer
err := fh.fillBuffer()
if err != nil {
return 0, fh.finish(err)
}
// Discard bytes from the buffer
if int(discard) > fh.bufSize {
return 0, fh.finish(ErrorBadSeek)
}
fh.bufIndex = int(discard)
// Set the limit
fh.limit = limit
return offset, nil
}
// Seek implements the io.Seeker interface
func (fh *decrypter) Seek(offset int64, whence int) (int64, error) {
return fh.RangeSeek(context.TODO(), offset, whence, -1)
}
// finish sets the final error and tidies up
func (fh *decrypter) finish(err error) error {
if fh.err != nil {
return fh.err
}
fh.err = err
fh.c.putBlock(fh.buf)
fh.buf = nil
fh.c.putBlock(fh.readBuf)
fh.readBuf = nil
return err
}
// unFinish undoes the effects of finish
func (fh *decrypter) unFinish() {
// Clear error
fh.err = nil
// reinstate the buffers
fh.buf = fh.c.getBlock()
fh.readBuf = fh.c.getBlock()
// Empty the buffer
fh.bufIndex = 0
fh.bufSize = 0
}
// Close
func (fh *decrypter) Close() error {
fh.mu.Lock()
defer fh.mu.Unlock()
// Check already closed
if fh.err == ErrorFileClosed {
return fh.err
}
// Closed before reading EOF so not finish()ed yet
if fh.err == nil {
_ = fh.finish(io.EOF)
}
// Show file now closed
fh.err = ErrorFileClosed
if fh.rc == nil {
return nil
}
return fh.rc.Close()
}
// finishAndClose does finish then Close()
//
// Used when we are returning a nil fh from new
func (fh *decrypter) finishAndClose(err error) error {
_ = fh.finish(err)
_ = fh.Close()
return err
}
// DecryptData decrypts the data stream
func (c *Cipher) DecryptData(rc io.ReadCloser) (io.ReadCloser, error) {
out, err := c.newDecrypter(rc)