aboutsummaryrefslogtreecommitdiffstats
path: root/whisper/envelope.go
blob: c1d84df78b026dda74eb9670c5055898eec092d2 (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
// Contains the Whisper protocol Envelope element. For formal details please see
// the specs at https://github.com/ethereum/wiki/wiki/Whisper-PoC-1-Protocol-Spec#envelopes.

package whisper

import (
    "crypto/ecdsa"
    "encoding/binary"
    "fmt"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/crypto/ecies"
    "github.com/ethereum/go-ethereum/rlp"
)

// Envelope represents a clear-text data packet to transmit through the Whisper
// network. Its contents may or may not be encrypted and signed.
type Envelope struct {
    Expiry uint32 // Whisper protocol specifies int32, really should be int64
    TTL    uint32 // ^^^^^^
    Topics []Topic
    Data   []byte
    Nonce  uint32

    hash common.Hash // Cached hash of the envelope to avoid rehashing every time
}

// NewEnvelope wraps a Whisper message with expiration and destination data
// included into an envelope for network forwarding.
func NewEnvelope(ttl time.Duration, topics []Topic, msg *Message) *Envelope {
    return &Envelope{
        Expiry: uint32(time.Now().Add(ttl).Unix()),
        TTL:    uint32(ttl.Seconds()),
        Topics: topics,
        Data:   msg.bytes(),
        Nonce:  0,
    }
}

// Seal closes the envelope by spending the requested amount of time as a proof
// of work on hashing the data.
func (self *Envelope) Seal(pow time.Duration) {
    d := make([]byte, 64)
    copy(d[:32], self.rlpWithoutNonce())

    finish, bestBit := time.Now().Add(pow).UnixNano(), 0
    for nonce := uint32(0); time.Now().UnixNano() < finish; {
        for i := 0; i < 1024; i++ {
            binary.BigEndian.PutUint32(d[60:], nonce)

            firstBit := common.FirstBitSet(common.BigD(crypto.Sha3(d)))
            if firstBit > bestBit {
                self.Nonce, bestBit = nonce, firstBit
            }
            nonce++
        }
    }
}

// rlpWithoutNonce returns the RLP encoded envelope contents, except the nonce.
func (self *Envelope) rlpWithoutNonce() []byte {
    enc, _ := rlp.EncodeToBytes([]interface{}{self.Expiry, self.TTL, self.Topics, self.Data})
    return enc
}

// Open extracts the message contained within a potentially encrypted envelope.
func (self *Envelope) Open(key *ecdsa.PrivateKey) (msg *Message, err error) {
    // Split open the payload into a message construct
    data := self.Data

    message := &Message{
        Flags: data[0],
        Sent:  int64(self.Expiry - self.TTL),
        Hash:  self.Hash(),
    }
    data = data[1:]

    if message.Flags&signatureFlag == signatureFlag {
        if len(data) < signatureLength {
            return nil, fmt.Errorf("unable to open envelope. First bit set but len(data) < len(signature)")
        }
        message.Signature, data = data[:signatureLength], data[signatureLength:]
    }
    message.Payload = data

    // Decrypt the message, if requested
    if key == nil {
        return message, nil
    }
    err = message.decrypt(key)
    switch err {
    case nil:
        return message, nil

    case ecies.ErrInvalidPublicKey: // Payload isn't encrypted
        return message, err

    default:
        return nil, fmt.Errorf("unable to open envelope, decrypt failed: %v", err)
    }
}

// Hash returns the SHA3 hash of the envelope, calculating it if not yet done.
func (self *Envelope) Hash() common.Hash {
    if (self.hash == common.Hash{}) {
        enc, _ := rlp.EncodeToBytes(self)
        self.hash = crypto.Sha3Hash(enc)
    }
    return self.hash
}

// DecodeRLP decodes an Envelope from an RLP data stream.
func (self *Envelope) DecodeRLP(s *rlp.Stream) error {
    raw, err := s.Raw()
    if err != nil {
        return err
    }
    // The decoding of Envelope uses the struct fields but also needs
    // to compute the hash of the whole RLP-encoded envelope. This
    // type has the same structure as Envelope but is not an
    // rlp.Decoder so we can reuse the Envelope struct definition.
    type rlpenv Envelope
    if err := rlp.DecodeBytes(raw, (*rlpenv)(self)); err != nil {
        return err
    }
    self.hash = crypto.Sha3Hash(raw)
    return nil
}