aboutsummaryrefslogtreecommitdiffstats
path: root/whisper/whisperv5/message.go
blob: 680d1f8a22f93fe32c876cc95d3f3dea35f1d256 (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
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
// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// Contains the Whisper protocol Message element. For formal details please see
// the specs at https://github.com/ethereum/wiki/wiki/Whisper-PoC-1-Protocol-Spec#messages.
// todo: fix the spec link, and move it to doc.go

package whisperv5

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/ecdsa"
    crand "crypto/rand"
    "crypto/sha256"
    "errors"
    "fmt"
    mrand "math/rand"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "golang.org/x/crypto/pbkdf2"
)

// Options specifies the exact way a message should be wrapped into an Envelope.
type MessageParams struct {
    TTL      uint32
    Src      *ecdsa.PrivateKey
    Dst      *ecdsa.PublicKey
    KeySym   []byte
    Topic    TopicType
    WorkTime uint32
    PoW      float64
    Payload  []byte
    Padding  []byte
}

// SentMessage represents an end-user data packet to transmit through the
// Whisper protocol. These are wrapped into Envelopes that need not be
// understood by intermediate nodes, just forwarded.
type SentMessage struct {
    Raw []byte
}

// ReceivedMessage represents a data packet to be received through the
// Whisper protocol.
type ReceivedMessage struct {
    Raw []byte

    Payload   []byte
    Padding   []byte
    Signature []byte

    PoW   float64          // Proof of work as described in the Whisper spec
    Sent  uint32           // Time when the message was posted into the network
    TTL   uint32           // Maximum time to live allowed for the message
    Src   *ecdsa.PublicKey // Message recipient (identity used to decode the message)
    Dst   *ecdsa.PublicKey // Message recipient (identity used to decode the message)
    Topic TopicType

    SymKeyHash      common.Hash // The Keccak256Hash of the key, associated with the Topic
    EnvelopeHash    common.Hash // Message envelope hash to act as a unique id
    EnvelopeVersion uint64
}

func isMessageSigned(flags byte) bool {
    return (flags & signatureFlag) != 0
}

func (msg *ReceivedMessage) isSymmetricEncryption() bool {
    return msg.SymKeyHash != common.Hash{}
}

func (msg *ReceivedMessage) isAsymmetricEncryption() bool {
    return msg.Dst != nil
}

func DeriveOneTimeKey(key []byte, salt []byte, version uint64) ([]byte, error) {
    if version == 0 {
        derivedKey := pbkdf2.Key(key, salt, 8, aesKeyLength, sha256.New)
        return derivedKey, nil
    } else {
        return nil, unknownVersionError(version)
    }
}

// NewMessage creates and initializes a non-signed, non-encrypted Whisper message.
func NewSentMessage(params *MessageParams) *SentMessage {
    msg := SentMessage{}
    msg.Raw = make([]byte, 1, len(params.Payload)+len(params.Payload)+signatureLength+padSizeLimitUpper)
    msg.Raw[0] = 0 // set all the flags to zero
    msg.appendPadding(params)
    msg.Raw = append(msg.Raw, params.Payload...)
    return &msg
}

// appendPadding appends the pseudorandom padding bytes and sets the padding flag.
// The last byte contains the size of padding (thus, its size must not exceed 256).
func (msg *SentMessage) appendPadding(params *MessageParams) {
    total := len(params.Payload) + 1
    if params.Src != nil {
        total += signatureLength
    }
    padChunk := padSizeLimitUpper
    if total <= padSizeLimitLower {
        padChunk = padSizeLimitLower
    }
    odd := total % padChunk
    if odd > 0 {
        padSize := padChunk - odd
        if padSize > 255 {
            // this algorithm is only valid if padSizeLimitUpper <= 256.
            // if padSizeLimitUpper will ever change, please fix the algorithm
            // (for more information see ReceivedMessage.extractPadding() function).
            panic("please fix the padding algorithm before releasing new version")
        }
        buf := make([]byte, padSize)
        randomize(buf[1:]) // change to: err = mrand.Read(buf[1:])
        buf[0] = byte(padSize)
        if params.Padding != nil {
            copy(buf[1:], params.Padding)
        }
        msg.Raw = append(msg.Raw, buf...)
        msg.Raw[0] |= byte(0x1) // number of bytes indicating the padding size
    }
}

// sign calculates and sets the cryptographic signature for the message,
// also setting the sign flag.
func (msg *SentMessage) sign(key *ecdsa.PrivateKey) error {
    if isMessageSigned(msg.Raw[0]) {
        // this should not happen, but no reason to panic
        glog.V(logger.Error).Infof("Trying to sign a message which was already signed")
        return nil
    }

    msg.Raw[0] |= signatureFlag
    hash := crypto.Keccak256(msg.Raw)
    signature, err := crypto.Sign(hash, key)
    if err != nil {
        msg.Raw[0] &= ^signatureFlag // clear the flag
        return err
    }
    msg.Raw = append(msg.Raw, signature...)
    return nil
}

// encryptAsymmetric encrypts a message with a public key.
func (msg *SentMessage) encryptAsymmetric(key *ecdsa.PublicKey) error {
    if !ValidatePublicKey(key) {
        return fmt.Errorf("Invalid public key provided for asymmetric encryption")
    }
    encrypted, err := crypto.Encrypt(key, msg.Raw)
    if err == nil {
        msg.Raw = encrypted
    }
    return err
}

// encryptSymmetric encrypts a message with a topic key, using AES-GCM-256.
// nonce size should be 12 bytes (see cipher.gcmStandardNonceSize).
func (msg *SentMessage) encryptSymmetric(key []byte) (salt []byte, nonce []byte, err error) {
    if !validateSymmetricKey(key) {
        return nil, nil, errors.New("invalid key provided for symmetric encryption")
    }

    salt = make([]byte, saltLength)
    _, err = crand.Read(salt)
    if err != nil {
        return nil, nil, err
    } else if !validateSymmetricKey(salt) {
        return nil, nil, errors.New("crypto/rand failed to generate salt")
    }

    derivedKey, err := DeriveOneTimeKey(key, salt, EnvelopeVersion)
    if err != nil {
        return nil, nil, err
    }
    if !validateSymmetricKey(derivedKey) {
        return nil, nil, errors.New("failed to derive one-time key")
    }
    block, err := aes.NewCipher(derivedKey)
    if err != nil {
        return nil, nil, err
    }
    aesgcm, err := cipher.NewGCM(block)
    if err != nil {
        return nil, nil, err
    }

    // never use more than 2^32 random nonces with a given key
    nonce = make([]byte, aesgcm.NonceSize())
    _, err = crand.Read(nonce)
    if err != nil {
        return nil, nil, err
    }
    msg.Raw = aesgcm.Seal(nil, nonce, msg.Raw, nil)
    return salt, nonce, nil
}

// Wrap bundles the message into an Envelope to transmit over the network.
//
// pow (Proof Of Work) controls how much time to spend on hashing the message,
// inherently controlling its priority through the network (smaller hash, bigger
// priority).
//
// The user can control the amount of identity, privacy and encryption through
// the options parameter as follows:
//   - options.From == nil && options.To == nil: anonymous broadcast
//   - options.From != nil && options.To == nil: signed broadcast (known sender)
//   - options.From == nil && options.To != nil: encrypted anonymous message
//   - options.From != nil && options.To != nil: encrypted signed message
func (msg *SentMessage) Wrap(options *MessageParams) (envelope *Envelope, err error) {
    if options.TTL == 0 {
        options.TTL = DefaultTTL
    }
    if options.Src != nil {
        err = msg.sign(options.Src)
        if err != nil {
            return nil, err
        }
    }
    if len(msg.Raw) > MaxMessageLength {
        glog.V(logger.Error).Infof("Message size must not exceed %d bytes", MaxMessageLength)
        return nil, errors.New("Oversized message")
    }
    var salt, nonce []byte
    if options.Dst != nil {
        err = msg.encryptAsymmetric(options.Dst)
    } else if options.KeySym != nil {
        salt, nonce, err = msg.encryptSymmetric(options.KeySym)
    } else {
        err = errors.New("Unable to encrypt the message: neither Dst nor Key")
    }

    if err != nil {
        return nil, err
    }

    envelope = NewEnvelope(options.TTL, options.Topic, salt, nonce, msg)
    envelope.Seal(options)
    return envelope, nil
}

// decryptSymmetric decrypts a message with a topic key, using AES-GCM-256.
// nonce size should be 12 bytes (see cipher.gcmStandardNonceSize).
func (msg *ReceivedMessage) decryptSymmetric(key []byte, salt []byte, nonce []byte) error {
    derivedKey, err := DeriveOneTimeKey(key, salt, msg.EnvelopeVersion)
    if err != nil {
        return err
    }

    block, err := aes.NewCipher(derivedKey)
    if err != nil {
        return err
    }
    aesgcm, err := cipher.NewGCM(block)
    if err != nil {
        return err
    }
    if len(nonce) != aesgcm.NonceSize() {
        info := fmt.Sprintf("Wrong AES nonce size - want: %d, got: %d", len(nonce), aesgcm.NonceSize())
        glog.V(logger.Error).Infof(info)
        return errors.New(info)
    }
    decrypted, err := aesgcm.Open(nil, nonce, msg.Raw, nil)
    if err != nil {
        return err
    }
    msg.Raw = decrypted
    return nil
}

// decryptAsymmetric decrypts an encrypted payload with a private key.
func (msg *ReceivedMessage) decryptAsymmetric(key *ecdsa.PrivateKey) error {
    decrypted, err := crypto.Decrypt(key, msg.Raw)
    if err == nil {
        msg.Raw = decrypted
    }
    return err
}

// Validate checks the validity and extracts the fields in case of success
func (msg *ReceivedMessage) Validate() bool {
    end := len(msg.Raw)
    if end < 1 {
        return false
    }

    if isMessageSigned(msg.Raw[0]) {
        end -= signatureLength
        if end <= 1 {
            return false
        }
        msg.Signature = msg.Raw[end:]
        msg.Src = msg.SigToPubKey()
        if msg.Src == nil {
            return false
        }
    }

    padSize, ok := msg.extractPadding(end)
    if !ok {
        return false
    }

    msg.Payload = msg.Raw[1+padSize : end]
    return true
}

// extractPadding extracts the padding from raw message.
// although we don't support sending messages with padding size
// exceeding 255 bytes, such messages are perfectly valid, and
// can be successfully decrypted.
func (msg *ReceivedMessage) extractPadding(end int) (int, bool) {
    paddingSize := 0
    sz := int(msg.Raw[0] & paddingMask) // number of bytes containing the entire size of padding, could be zero
    if sz != 0 {
        paddingSize = int(bytesToIntLittleEndian(msg.Raw[1 : 1+sz]))
        if paddingSize < sz || paddingSize+1 > end {
            return 0, false
        }
        msg.Padding = msg.Raw[1+sz : 1+paddingSize]
    }
    return paddingSize, true
}

// Recover retrieves the public key of the message signer.
func (msg *ReceivedMessage) SigToPubKey() *ecdsa.PublicKey {
    defer func() { recover() }() // in case of invalid signature

    pub, err := crypto.SigToPub(msg.hash(), msg.Signature)
    if err != nil {
        glog.V(logger.Error).Infof("Could not get public key from signature: %v", err)
        return nil
    }
    return pub
}

// hash calculates the SHA3 checksum of the message flags, payload and padding.
func (msg *ReceivedMessage) hash() []byte {
    if isMessageSigned(msg.Raw[0]) {
        sz := len(msg.Raw) - signatureLength
        return crypto.Keccak256(msg.Raw[:sz])
    }
    return crypto.Keccak256(msg.Raw)
}

// rand.Rand provides a Read method in Go 1.7 and later,
// but we can't use it yet.
func randomize(b []byte) {
    cnt := 0
    val := mrand.Int63()
    for n := 0; n < len(b); n++ {
        b[n] = byte(val)
        val >>= 8
        cnt++
        if cnt >= 7 {
            cnt = 0
            val = mrand.Int63()
        }
    }
}