2 GoVPN -- simple secure free software virtual private network daemon
3 Copyright (C) 2014-2017 Sergey Matveev <stargrave@stargrave.org>
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
28 "github.com/Sirupsen/logrus"
29 "github.com/agl/ed25519"
30 "github.com/agl/ed25519/extra25519"
31 "github.com/pkg/errors"
32 "golang.org/x/crypto/blake2b"
33 "golang.org/x/crypto/curve25519"
37 // RSize is size in bytes of channel binding random value
39 // SSize is size in bytes of shared secret half
42 wrapIDTag = "idTag id:%q timeSync:%d"
45 // Handshake is state of a handshake/negotiation between client and server
46 type Handshake struct {
51 dsaPubH *[ed25519.PublicKeySize]byte
54 dhPriv *[32]byte // own private DH key
55 rServer *[RSize]byte // random string for authentication
57 sServer *[SSize]byte // secret string for main key calculation
61 // LogFields return a logrus compatible logging context
62 func (h *Handshake) LogFields() logrus.Fields {
65 prefix + "remote": h.addr,
66 prefix + "last_ping": h.LastPing.String(),
67 prefix + "id": h.Conf.ID.String(),
71 func keyFromSecrets(server, client []byte) *[SSize]byte {
73 for i := 0; i < SSize; i++ {
74 k[i] = server[i] ^ client[i]
79 // Zero handshake's memory state
80 func (h *Handshake) Zero() {
82 SliceZero(h.rNonce[:])
85 SliceZero(h.dhPriv[:])
91 SliceZero(h.dsaPubH[:])
94 SliceZero(h.rServer[:])
97 SliceZero(h.rClient[:])
100 SliceZero(h.sServer[:])
102 if h.sClient != nil {
103 SliceZero(h.sClient[:])
107 func (h *Handshake) rNonceNext(count uint64) *[16]byte {
108 nonce := new([16]byte)
109 nonceCurrent, _ := binary.Uvarint(h.rNonce[8:])
110 binary.PutUvarint(nonce[8:], nonceCurrent+count)
114 func dhKeypairGen() (*[32]byte, *[32]byte, error) {
115 priv := new([32]byte)
117 repr := new([32]byte)
120 if _, err := io.ReadFull(Rand, priv[:]); err != nil {
121 return nil, nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
123 reprFound = extra25519.ScalarBaseMult(pub, repr, priv)
125 return priv, repr, nil
128 func dhKeyGen(priv, pub *[32]byte) *[32]byte {
130 curve25519.ScalarMult(key, priv, pub)
131 hashed := blake2b.Sum256(key[:])
135 // NewHandshake creates new handshake state.
136 func NewHandshake(addr string, conn io.Writer, conf *PeerConf) *Handshake {
140 LastPing: time.Now(),
143 state.dsaPubH = new([ed25519.PublicKeySize]byte)
144 copy(state.dsaPubH[:], state.Conf.Verifier.Pub[:])
145 hashed := blake2b.Sum256(state.dsaPubH[:])
146 state.dsaPubH = &hashed
150 // Generate ID tag from client identification and data.
151 func idTag(id *PeerID, timeSync int, data []byte) ([]byte, error) {
152 enc := make([]byte, 8)
154 AddTimeSync(timeSync, enc)
155 mac, err := blake2b.New256(id[:])
157 return nil, errors.Wrap(err, wrapBlake2bNew256)
159 if _, err = mac.Write(enc); err != nil {
160 return nil, errors.Wrap(err, "mac.Write")
163 return sum[len(sum)-8:], nil
166 // HandshakeStarts start handshake's procedure from the client.
167 // It is the entry point for starting the handshake procedure.
168 // First handshake packet will be sent immediately.
169 func HandshakeStart(addr string, conn io.Writer, conf *PeerConf) (*Handshake, error) {
170 state := NewHandshake(addr, conn, conf)
175 if state.dhPriv, dhPubRepr, err = dhKeypairGen(); err != nil {
176 return nil, errors.Wrap(err, "dhKeypairGen")
179 state.rNonce = new([16]byte)
180 if _, err := io.ReadFull(Rand, state.rNonce[8:]); err != nil {
181 return nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
185 enc = make([]byte, conf.MTU-8-RSize)
187 enc = make([]byte, 32)
189 copy(enc, dhPubRepr[:])
191 enc, err = EnclessEncode(state.dsaPubH, state.rNonce, enc)
193 return nil, errors.Wrap(err, wrapEnclessDecode)
196 chacha20.XORKeyStream(enc, enc, state.rNonce, state.dsaPubH)
198 tag, err := idTag(state.Conf.ID, state.Conf.TimeSync, state.rNonce[8:])
200 return nil, errors.Wrapf(err, wrapIDTag, state.Conf.ID.String(), state.Conf.TimeSync)
202 data := append(state.rNonce[8:], enc...)
203 data = append(data, tag...)
204 if _, err = state.conn.Write(data); err != nil {
205 return nil, errors.Wrap(err, "state.conn.Write")
210 // Server processes handshake message on the server side.
211 // This function is intended to be called on server's side.
212 // If this is the final handshake message, then new Peer object
213 // will be created and used as a transport.
214 func (h *Handshake) Server(data []byte) (*Peer, error) {
215 // R + ENC(H(DSAPub), R, El(CDHPub)) + IDtag
216 if h.rNonce == nil && ((!h.Conf.Encless && len(data) >= 48) ||
217 (h.Conf.Encless && len(data) == EnclessEnlargeSize+h.Conf.MTU)) {
218 h.rNonce = new([16]byte)
219 copy(h.rNonce[8:], data[:RSize])
221 // Decrypt remote public key
222 cDHRepr := new([32]byte)
224 out, err := EnclessDecode(
227 data[RSize:len(data)-8],
230 return nil, errors.Wrap(err, wrapEnclessDecode)
232 copy(cDHRepr[:], out)
234 chacha20.XORKeyStream(cDHRepr[:], data[RSize:RSize+32], h.rNonce, h.dsaPubH)
237 // Generate DH keypair
238 var dhPubRepr *[32]byte
240 if h.dhPriv, dhPubRepr, err = dhKeypairGen(); err != nil {
241 return nil, errors.Wrap(err, "dhKeypairGen")
244 // Compute shared key
246 extra25519.RepresentativeToPublicKey(cDH, cDHRepr)
247 h.key = dhKeyGen(h.dhPriv, cDH)
251 encPub = make([]byte, h.Conf.MTU)
252 copy(encPub, dhPubRepr[:])
253 encPub, err = EnclessEncode(h.dsaPubH, h.rNonceNext(1), encPub)
255 return nil, errors.Wrap(err, wrapEnclessEncode)
258 encPub = make([]byte, 32)
259 chacha20.XORKeyStream(encPub, dhPubRepr[:], h.rNonceNext(1), h.dsaPubH)
262 // Generate R* and encrypt them
263 h.rServer = new([RSize]byte)
264 if _, err = io.ReadFull(Rand, h.rServer[:]); err != nil {
265 return nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
267 h.sServer = new([SSize]byte)
268 if _, err = io.ReadFull(Rand, h.sServer[:]); err != nil {
269 return nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
272 if h.Conf.Noise && !h.Conf.Encless {
273 encRs = make([]byte, h.Conf.MTU-len(encPub)-8)
274 } else if h.Conf.Encless {
275 encRs = make([]byte, h.Conf.MTU-8)
277 encRs = make([]byte, RSize+SSize)
279 copy(encRs, append(h.rServer[:], h.sServer[:]...))
281 encRs, err = EnclessEncode(h.key, h.rNonce, encRs)
283 return nil, errors.Wrap(err, wrapEnclessEncode)
286 chacha20.XORKeyStream(encRs, encRs, h.rNonce, h.key)
289 tag, err := idTag(h.Conf.ID, h.Conf.TimeSync, encPub)
291 return nil, errors.Wrapf(err, wrapIDTag, h.Conf.ID.String(), h.Conf.TimeSync)
294 // Send that to client
295 _, err = h.conn.Write(append(encPub, append(
299 return nil, errors.Wrap(err, "conn.Write")
301 h.LastPing = time.Now()
303 // ENC(K, R+1, RS + RC + SC + Sign(DSAPriv, K)) + IDtag
304 if h.rClient == nil && ((!h.Conf.Encless && len(data) >= 120) ||
305 (h.Conf.Encless && len(data) == EnclessEnlargeSize+h.Conf.MTU)) {
309 dec, err = EnclessDecode(
315 return nil, errors.Wrap(err, wrapEnclessDecode)
317 dec = dec[:RSize+RSize+SSize+ed25519.SignatureSize]
319 dec = make([]byte, RSize+RSize+SSize+ed25519.SignatureSize)
320 chacha20.XORKeyStream(
322 data[:RSize+RSize+SSize+ed25519.SignatureSize],
327 if subtle.ConstantTimeCompare(dec[:RSize], h.rServer[:]) != 1 {
328 return nil, errors.New("Invalid server's random number")
330 sign := new([ed25519.SignatureSize]byte)
331 copy(sign[:], dec[RSize+RSize+SSize:])
332 if !ed25519.Verify(h.Conf.Verifier.Pub, h.key[:], sign) {
333 return nil, errors.New("Invalid signature")
336 // Send final answer to client
339 enc = make([]byte, h.Conf.MTU-8)
341 enc = make([]byte, RSize)
343 copy(enc, dec[RSize:RSize+RSize])
345 enc, err = EnclessEncode(h.key, h.rNonceNext(2), enc)
347 return nil, errors.Wrap(err, wrapEnclessEncode)
350 chacha20.XORKeyStream(enc, enc, h.rNonceNext(2), h.key)
352 tag, err := idTag(h.Conf.ID, h.Conf.TimeSync, enc)
354 return nil, errors.Wrapf(err, wrapIDTag, h.Conf.ID.String(), h.Conf.TimeSync)
356 if _, err = h.conn.Write(append(enc, tag...)); err != nil {
357 return nil, errors.Wrap(err, "conn.Write")
361 peer, err := newPeer(
366 keyFromSecrets(h.sServer[:], dec[RSize+RSize:RSize+RSize+SSize]))
368 return nil, errors.Wrap(err, "newPeer")
370 h.LastPing = time.Now()
376 // Client processes handshake message on the client side.
377 // This function is intended to be called on client's side.
378 // If this is the final handshake message, then new Peer object
379 // will be created and used as a transport. If no mutually
380 // authenticated Peer is ready, then return nil.
381 func (h *Handshake) Client(data []byte) (*Peer, error) {
382 // ENC(H(DSAPub), R+1, El(SDHPub)) + ENC(K, R, RS + SS) + IDtag
383 if h.rServer == nil && h.key == nil &&
384 ((!h.Conf.Encless && len(data) >= 80) ||
385 (h.Conf.Encless && len(data) == 2*(EnclessEnlargeSize+h.Conf.MTU))) {
386 // Decrypt remote public key
387 sDHRepr := new([32]byte)
391 tmp, err = EnclessDecode(
397 return nil, errors.Wrap(err, wrapEnclessDecode)
399 copy(sDHRepr[:], tmp[:32])
401 chacha20.XORKeyStream(sDHRepr[:], data[:32], h.rNonceNext(1), h.dsaPubH)
404 // Compute shared key
406 extra25519.RepresentativeToPublicKey(sDH, sDHRepr)
407 h.key = dhKeyGen(h.dhPriv, sDH)
410 h.rServer = new([RSize]byte)
411 h.sServer = new([SSize]byte)
413 tmp, err = EnclessDecode(h.key, h.rNonce, data[len(data)/2:len(data)-8])
415 return nil, errors.Wrap(err, wrapEnclessDecode)
417 copy(h.rServer[:], tmp[:RSize])
418 copy(h.sServer[:], tmp[RSize:RSize+SSize])
420 decRs := make([]byte, RSize+SSize)
421 chacha20.XORKeyStream(decRs, data[SSize:SSize+RSize+SSize], h.rNonce, h.key)
422 copy(h.rServer[:], decRs[:RSize])
423 copy(h.sServer[:], decRs[RSize:])
426 // Generate R* and signature and encrypt them
427 h.rClient = new([RSize]byte)
428 if _, err = io.ReadFull(Rand, h.rClient[:]); err != nil {
429 return nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
431 h.sClient = new([SSize]byte)
432 if _, err = io.ReadFull(Rand, h.sClient[:]); err != nil {
433 return nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
435 sign := ed25519.Sign(h.Conf.DSAPriv, h.key[:])
439 enc = make([]byte, h.Conf.MTU-8)
441 enc = make([]byte, RSize+RSize+SSize+ed25519.SignatureSize)
443 copy(enc, h.rServer[:])
444 copy(enc[RSize:], h.rClient[:])
445 copy(enc[RSize+RSize:], h.sClient[:])
446 copy(enc[RSize+RSize+SSize:], sign[:])
448 enc, err = EnclessEncode(h.key, h.rNonceNext(1), enc)
450 return nil, errors.Wrap(err, wrapEnclessEncode)
453 chacha20.XORKeyStream(enc, enc, h.rNonceNext(1), h.key)
456 tag, err := idTag(h.Conf.ID, h.Conf.TimeSync, enc)
458 return nil, errors.Wrapf(err, wrapIDTag, h.Conf.ID.String(), h.Conf.TimeSync)
461 // Send that to server
462 if _, err = h.conn.Write(append(enc, tag...)); err != nil {
463 return nil, errors.Wrap(err, "conn.Write")
465 h.LastPing = time.Now()
467 // ENC(K, R+2, RC) + IDtag
468 if h.key != nil && ((!h.Conf.Encless && len(data) >= 16) ||
469 (h.Conf.Encless && len(data) == EnclessEnlargeSize+h.Conf.MTU)) {
474 dec, err = EnclessDecode(h.key, h.rNonceNext(2), data[:len(data)-8])
476 return nil, errors.Wrap(err, wrapEnclessDecode)
480 dec = make([]byte, RSize)
481 chacha20.XORKeyStream(dec, data[:RSize], h.rNonceNext(2), h.key)
483 if subtle.ConstantTimeCompare(dec, h.rClient[:]) != 1 {
484 return nil, errors.New("Invalid client's random number")
488 peer, err := newPeer(
493 keyFromSecrets(h.sServer[:], h.sClient[:]),
496 return nil, errors.Wrap(err, "newPeer")
498 h.LastPing = time.Now()
502 // no peer yet, no error