-
Notifications
You must be signed in to change notification settings - Fork 17
/
header.go
518 lines (433 loc) · 16.3 KB
/
header.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
package ss2022
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"math/rand"
"time"
"github.com/database64128/shadowsocks-go/socks5"
"github.com/database64128/shadowsocks-go/zerocopy"
)
const (
HeaderTypeClientStream = 0
HeaderTypeServerStream = 1
HeaderTypeClientPacket = 0
HeaderTypeServerPacket = 1
MinPaddingLength = 0
MaxPaddingLength = 900
IdentityHeaderLength = 16
// type + unix epoch timestamp + u16be length
TCPRequestFixedLengthHeaderLength = 1 + 8 + 2
// SOCKS address + padding length + padding
TCPRequestVariableLengthHeaderNoPayloadMaxLength = socks5.MaxAddrLen + 2 + MaxPaddingLength
// type + unix epoch timestamp + request salt + u16be length
TCPResponseHeaderMaxLength = 1 + 8 + 32 + 2
// session ID + packet ID
UDPSeparateHeaderLength = 8 + 8
// type + unix epoch timestamp + padding length
UDPClientMessageHeaderFixedLength = 1 + 8 + 2
// type + unix epoch timestamp + client session id + padding length
UDPServerMessageHeaderFixedLength = 1 + 8 + 8 + 2
// type + unix epoch timestamp + padding length + padding + SOCKS address
UDPClientMessageHeaderMaxLength = UDPClientMessageHeaderFixedLength + MaxPaddingLength + socks5.MaxAddrLen
// type + unix epoch timestamp + client session id + padding length + padding + SOCKS address
UDPServerMessageHeaderMaxLength = UDPServerMessageHeaderFixedLength + MaxPaddingLength + socks5.MaxAddrLen
// MaxEpochDiff is the maximum allowed time difference between a received timestamp and system time.
MaxEpochDiff = 30
// MaxTimeDiff is the maximum allowed time difference between a received timestamp and system time.
MaxTimeDiff = MaxEpochDiff * time.Second
// ReplayWindowDuration defines the amount of time during which a salt check is necessary.
ReplayWindowDuration = MaxTimeDiff * 2
)
var (
ErrIncompleteHeaderInFirstChunk = errors.New("header in first chunk is missing or incomplete")
ErrPaddingExceedChunkBorder = errors.New("padding in first chunk is shorter than advertised")
ErrBadTimestamp = errors.New("time diff is over 30 seconds")
ErrTypeMismatch = errors.New("header type mismatch")
ErrPaddingLengthOutOfRange = errors.New("padding length is less than 0 or greater than 900")
ErrClientSaltMismatch = errors.New("client salt in response header does not match request")
ErrClientSessionIDMismatch = errors.New("client session ID in server message header does not match current session")
ErrTooManyServerSessions = errors.New("server session changed more than once during the last minute")
ErrPacketIncompleteHeader = errors.New("packet contains incomplete header")
ErrPacketMissingPayload = errors.New("packet has no payload")
ErrReplay = errors.New("detected replay")
ErrIdentityHeaderUserPSKNotFound = errors.New("decrypted identity header does not match any known uPSK")
)
type HeaderError[T any] struct {
Err error
Expected T
Got T
}
func (e *HeaderError[T]) Unwrap() error {
return e.Err
}
func (e *HeaderError[T]) Error() string {
return fmt.Sprintf("%s: expected %v, got %v", e.Err.Error(), e.Expected, e.Got)
}
// ValidateUnixEpochTimestamp validates the Unix Epoch timestamp in the buffer
// and returns an error if the timestamp exceeds the allowed time difference from system time.
//
// This function does not check buffer length. Make sure it's exactly 8 bytes long.
func ValidateUnixEpochTimestamp(b []byte) error {
tsEpoch := int64(binary.BigEndian.Uint64(b))
nowEpoch := time.Now().Unix()
diff := tsEpoch - nowEpoch
if diff < -MaxEpochDiff || diff > MaxEpochDiff {
return &HeaderError[int64]{ErrBadTimestamp, nowEpoch, tsEpoch}
}
return nil
}
// ParseTCPRequestFixedLengthHeader parses a TCP request fixed-length header and returns the length
// of the variable-length header, or an error if header validation fails.
//
// The buffer must be exactly 11 bytes long. No buffer length checks are performed.
//
// Request fixed-length header:
// +------+---------------+--------+
// | type | timestamp | length |
// +------+---------------+--------+
// | 1B | 8B unix epoch | u16be |
// +------+---------------+--------+
func ParseTCPRequestFixedLengthHeader(b []byte) (n int, err error) {
// Type
if b[0] != HeaderTypeClientStream {
err = &HeaderError[byte]{ErrTypeMismatch, HeaderTypeClientStream, b[0]}
return
}
// Timestamp
err = ValidateUnixEpochTimestamp(b[1:])
if err != nil {
return
}
// Length
n = int(binary.BigEndian.Uint16(b[1+8:]))
return
}
// WriteTCPRequestFixedLengthHeader writes a TCP request fixed-length header into the buffer.
//
// The buffer must be at least 11 bytes long. No buffer length checks are performed.
func WriteTCPRequestFixedLengthHeader(b []byte, length uint16) {
// Type
b[0] = HeaderTypeClientStream
// Timestamp
binary.BigEndian.PutUint64(b[1:], uint64(time.Now().Unix()))
// Length
binary.BigEndian.PutUint16(b[1+8:], length)
}
// ParseTCPRequestVariableLengthHeader parses a TCP request variable-length header and returns
// the target address, the initial payload if available, or an error if header validation fails.
//
// This function does buffer length checks and returns ErrIncompleteHeaderInFirstChunk if the buffer is too short.
//
// Request variable-length header:
// +------+----------+-------+----------------+----------+-----------------+
// | ATYP | address | port | padding length | padding | initial payload |
// +------+----------+-------+----------------+----------+-----------------+
// | 1B | variable | u16be | u16be | variable | variable |
// +------+----------+-------+----------------+----------+-----------------+
func ParseTCPRequestVariableLengthHeader(b []byte) (targetAddr socks5.Addr, payload []byte, err error) {
// SOCKS address
targetAddr, err = socks5.SplitAddr(b)
if err != nil {
return
}
n := len(targetAddr)
// Make sure the remaining length > 2 (padding length + either padding or payload)
if len(b)-n <= 2 {
err = ErrIncompleteHeaderInFirstChunk
return
}
// Padding length
paddingLen := int(binary.BigEndian.Uint16(b[n:]))
if paddingLen < MinPaddingLength || paddingLen > MaxPaddingLength {
err = &HeaderError[int]{ErrPaddingLengthOutOfRange, MaxPaddingLength, paddingLen}
return
}
n += 2
// Padding
n += paddingLen
if n > len(b) {
err = &HeaderError[int]{ErrPaddingExceedChunkBorder, len(b), n}
return
}
// Initial payload
payload = b[n:]
return
}
// WriteTCPRequestVariableLengthHeader writes a TCP request variable-length header into the buffer
// and returns the number of bytes written.
//
// This function does not check buffer length.
// The buffer must be at least len(targetAddr) + 2 + MaxPaddingLength bytes long if there's no payload,
// or len(targetAddr) + 2 + len(payload) bytes long.
func WriteTCPRequestVariableLengthHeader(b []byte, targetAddr socks5.Addr, payload []byte) (n int) {
// SOCKS address
n = copy(b, targetAddr)
// Padding length
var paddingLen int
if len(payload) == 0 {
paddingLen = rand.Intn(MaxPaddingLength) + 1
}
binary.BigEndian.PutUint16(b[n:], uint16(paddingLen))
n += 2
// Padding
n += paddingLen
// Initial payload
n += copy(b[n:], payload)
return
}
// ParseTCPResponseHeader parses a TCP response fixed-length header and returns the length
// of the next payload chunk, or an error if header validation fails.
//
// The buffer must be exactly 1 + 8 + salt length + 2 bytes long. No buffer length checks are performed.
//
// Response fixed-length header:
// +------+---------------+----------------+--------+
// | type | timestamp | request salt | length |
// +------+---------------+----------------+--------+
// | 1B | 8B unix epoch | 16/32B | u16be |
// +------+---------------+----------------+--------+
func ParseTCPResponseHeader(b []byte, requestSalt []byte) (n int, err error) {
// Type
if b[0] != HeaderTypeServerStream {
err = &HeaderError[byte]{ErrTypeMismatch, HeaderTypeServerStream, b[0]}
return
}
// Timestamp
err = ValidateUnixEpochTimestamp(b[1 : 1+8])
if err != nil {
return
}
// Request salt
rSalt := b[1+8 : 1+8+len(requestSalt)]
if !bytes.Equal(requestSalt, rSalt) {
err = &HeaderError[[]byte]{ErrClientSaltMismatch, requestSalt, rSalt}
return
}
// Length
n = int(binary.BigEndian.Uint16(b[1+8+len(requestSalt):]))
return
}
// WriteTCPResponseHeader writes a TCP response fixed-length header into the buffer
// and returns the number of bytes written.
//
// This function does not check buffer length.
// The buffer must be at least 1 + 8 + salt length + 2 bytes long.
func WriteTCPResponseHeader(b []byte, requestSalt []byte, length uint16) (n int) {
// Type
b[0] = HeaderTypeServerStream
// Timestamp
binary.BigEndian.PutUint64(b[1:], uint64(time.Now().Unix()))
// Request salt
n = 1 + 8
n += copy(b[n:], requestSalt)
// Length
binary.BigEndian.PutUint16(b[n:], length)
n += 2
return
}
// ParseSessionIDAndPacketID parses the session ID and packet ID segment of a decrypted UDP packet.
//
// The buffer must be exactly 16 bytes long. No buffer length checks are performed.
//
// Session ID and packet ID segment:
// +------------+-----------+
// | session ID | packet ID |
// +------------+-----------+
// | 8B | u64be |
// +------------+-----------+
func ParseSessionIDAndPacketID(b []byte) (sid, pid uint64) {
sid = binary.BigEndian.Uint64(b)
pid = binary.BigEndian.Uint64(b[8:])
return
}
// WriteSessionIDAndPacketID writes the session ID and packet ID to the buffer.
//
// The buffer must be exactly 16 bytes long. No buffer length checks are performed.
func WriteSessionIDAndPacketID(b []byte, sid, pid uint64) {
binary.BigEndian.PutUint64(b, sid)
binary.BigEndian.PutUint64(b[8:], pid)
}
// ParseUDPClientMessageHeader parses a UDP client message header and returns the target address
// and payload, or an error if header validation fails or no payload is in the buffer.
//
// This function accepts buffers of arbitrary lengths.
//
// The buffer is expected to contain a decrypted client message in the following format:
// +------+---------------+----------------+----------+------+----------+-------+----------+
// | type | timestamp | padding length | padding | ATYP | address | port | payload |
// +------+---------------+----------------+----------+------+----------+-------+----------+
// | 1B | 8B unix epoch | u16be | variable | 1B | variable | u16be | variable |
// +------+---------------+----------------+----------+------+----------+-------+----------+
func ParseUDPClientMessageHeader(b []byte) (targetAddr socks5.Addr, payloadStart, payloadLen int, err error) {
// Make sure buffer has type + timestamp + padding length.
if len(b) < UDPClientMessageHeaderFixedLength {
err = ErrPacketIncompleteHeader
return
}
// Type
if b[0] != HeaderTypeClientPacket {
err = &HeaderError[byte]{ErrTypeMismatch, HeaderTypeClientPacket, b[0]}
return
}
// Timestamp
err = ValidateUnixEpochTimestamp(b[1 : 1+8])
if err != nil {
return
}
// Padding length
paddingLen := int(binary.BigEndian.Uint16(b[1+8:]))
if paddingLen < MinPaddingLength || paddingLen > MaxPaddingLength {
err = &HeaderError[int]{ErrPaddingLengthOutOfRange, MaxPaddingLength, paddingLen}
return
}
// Padding
payloadStart = UDPClientMessageHeaderFixedLength + paddingLen
if payloadStart > len(b) {
err = ErrPacketIncompleteHeader
return
}
// SOCKS address
targetAddr, err = socks5.SplitAddr(b[payloadStart:])
if err != nil {
return
}
payloadStart += len(targetAddr)
// Payload
payloadLen = len(b) - payloadStart
if payloadLen == 0 {
err = ErrPacketMissingPayload
}
return
}
// WriteUDPClientMessageHeader writes a UDP client message header into the buffer,
// starting from the end of the buffer towards the beginning, and returns the number of bytes written.
//
// This function checks buffer length and adds padding with best efforts.
// The buffer must be at least 1 + 8 + 2 + len(targetAddr) bytes long.
func WriteUDPClientMessageHeader(b []byte, targetAddr socks5.Addr, shouldPad func(socks5.Addr) bool) (n int, err error) {
// Check buffer length.
addrStart := len(b) - len(targetAddr)
roomForPadding := addrStart - UDPClientMessageHeaderFixedLength
if roomForPadding < 0 {
err = zerocopy.ErrPayloadTooBig
return
}
// SOCKS address
bAddr := b[addrStart:]
n = copy(bAddr, targetAddr)
// Padding
if roomForPadding > MaxPaddingLength {
roomForPadding = MaxPaddingLength
}
var paddingLen int
if roomForPadding > 0 && shouldPad(targetAddr) {
paddingLen = rand.Intn(roomForPadding) + 1
}
n += UDPClientMessageHeaderFixedLength + paddingLen
typeOffset := addrStart - UDPClientMessageHeaderFixedLength - paddingLen
hdr := b[typeOffset:]
// Type
hdr[0] = HeaderTypeClientPacket
// Timestamp
binary.BigEndian.PutUint64(hdr[1:], uint64(time.Now().Unix()))
// Padding length
binary.BigEndian.PutUint16(hdr[1+8:], uint16(paddingLen))
return
}
// ParseUDPServerMessageHeader parses a UDP server message header and returns the target address
// and payload, or an error if header validation fails or no payload is in the buffer.
//
// This function accepts buffers of arbitrary lengths.
//
// The buffer is expected to contain a decrypted server message in the following format:
// +------+---------------+-------------------+----------------+----------+------+----------+-------+----------+
// | type | timestamp | client session ID | padding length | padding | ATYP | address | port | payload |
// +------+---------------+-------------------+----------------+----------+------+----------+-------+----------+
// | 1B | 8B unix epoch | 8B | u16be | variable | 1B | variable | u16be | variable |
// +------+---------------+-------------------+----------------+----------+------+----------+-------+----------+
func ParseUDPServerMessageHeader(b []byte, csid uint64) (targetAddr socks5.Addr, payloadStart, payloadLen int, err error) {
// Make sure buffer has type + timestamp + client session ID + padding length.
if len(b) < UDPServerMessageHeaderFixedLength {
err = ErrPacketIncompleteHeader
return
}
// Type
if b[0] != HeaderTypeServerPacket {
err = &HeaderError[byte]{ErrTypeMismatch, HeaderTypeServerPacket, b[0]}
return
}
// Timestamp
err = ValidateUnixEpochTimestamp(b[1 : 1+8])
if err != nil {
return
}
// Client session ID
pcsid := binary.BigEndian.Uint64(b[1+8:])
if pcsid != csid {
err = &HeaderError[uint64]{ErrClientSessionIDMismatch, csid, pcsid}
return
}
// Padding length
paddingLen := int(binary.BigEndian.Uint16(b[1+8+8:]))
if paddingLen < MinPaddingLength || paddingLen > MaxPaddingLength {
err = &HeaderError[int]{ErrPaddingLengthOutOfRange, MaxPaddingLength, paddingLen}
return
}
// Padding
payloadStart = UDPServerMessageHeaderFixedLength + paddingLen
if payloadStart > len(b) {
err = ErrPacketIncompleteHeader
return
}
// SOCKS address
targetAddr, err = socks5.SplitAddr(b[payloadStart:])
if err != nil {
return
}
payloadStart += len(targetAddr)
// Payload
payloadLen = len(b) - payloadStart
if payloadLen == 0 {
err = ErrPacketMissingPayload
}
return
}
// WriteUDPServerMessageHeader writes a UDP server message header into the buffer,
// starting from the end of the buffer towards the beginning, and returns the number of bytes written.
//
// This function checks buffer length and adds padding with best efforts.
// The buffer must be at least 1 + 8 + 8 + 2 + len(targetAddr) bytes long.
func WriteUDPServerMessageHeader(b []byte, csid uint64, targetAddr socks5.Addr, shouldPad func(socks5.Addr) bool) (n int, err error) {
// Check buffer length.
addrStart := len(b) - len(targetAddr)
roomForPadding := addrStart - UDPServerMessageHeaderFixedLength
if roomForPadding < 0 {
err = zerocopy.ErrPayloadTooBig
return
}
// SOCKS address
bAddr := b[addrStart:]
n = copy(bAddr, targetAddr)
// Padding
if roomForPadding > MaxPaddingLength {
roomForPadding = MaxPaddingLength
}
var paddingLen int
if roomForPadding > 0 && shouldPad(targetAddr) {
paddingLen = rand.Intn(roomForPadding) + 1
}
n += UDPServerMessageHeaderFixedLength + paddingLen
typeOffset := addrStart - UDPServerMessageHeaderFixedLength - paddingLen
hdr := b[typeOffset:]
// Type
hdr[0] = HeaderTypeServerPacket
// Timestamp
binary.BigEndian.PutUint64(hdr[1:], uint64(time.Now().Unix()))
// Client session ID
binary.BigEndian.PutUint64(hdr[1+8:], csid)
// Padding length
binary.BigEndian.PutUint16(hdr[1+8+8:], uint16(paddingLen))
return
}