path: root/whisper/envelope.go

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"
)

const (
    DefaultPow = 50 * time.Millisecond
)

type Envelope struct {
    Expiry uint32 // Whisper protocol specifies int32, really should be int64
    TTL    uint32 // ^^^^^^
    Topics [][]byte
    Data   []byte
    Nonce  uint32

    hash common.Hash
}

func (self *Envelope) Hash() common.Hash {
    if (self.hash == common.Hash{}) {
        enc, _ := rlp.EncodeToBytes(self)
        self.hash = crypto.Sha3Hash(enc)
    }
    return self.hash
}

func NewEnvelope(ttl time.Duration, topics [][]byte, data *Message) *Envelope {
    exp := time.Now().Add(ttl)
    return &Envelope{
        Expiry: uint32(exp.Unix()),
        TTL:    uint32(ttl.Seconds()),
        Topics: topics,
        Data:   data.bytes(),
        Nonce:  0,
    }
}

func (self *Envelope) Seal(pow time.Duration) {
    self.proveWork(pow)
}

func (self *Envelope) Open(key *ecdsa.PrivateKey) (msg *Message, err error) {
    data := self.Data

    message := Message{
        Flags: data[0],
    }
    data = data[1:]

    if message.Flags&128 == 128 {
        if len(data) < 65 {
            return nil, fmt.Errorf("unable to open envelope. First bit set but len(data) < 65")
        }
        message.Signature, data = data[:65], data[65:]
    }
    message.Payload = data

    if key != nil {
        message.Payload, err = crypto.Decrypt(key, message.Payload)
        switch err {
        case nil: // OK
        case ecies.ErrInvalidPublicKey: // Payload isn't encrypted
            return &message, err
        default:
            return nil, fmt.Errorf("unable to open envelope. Decrypt failed: %v", err)
        }
    }
    return &message, nil
}

func (self *Envelope) proveWork(dura time.Duration) {
    var bestBit int
    d := make([]byte, 64)
    enc, _ := rlp.EncodeToBytes(self.withoutNonce())
    copy(d[:32], enc)

    then := time.Now().Add(dura).UnixNano()
    for n := uint32(0); time.Now().UnixNano() < then; {
        for i := 0; i < 1024; i++ {
            binary.BigEndian.PutUint32(d[60:], n)

            fbs := common.FirstBitSet(common.BigD(crypto.Sha3(d)))
            if fbs > bestBit {
                bestBit = fbs
                self.Nonce = n
            }

            n++
        }
    }
}

func (self *Envelope) valid() bool {
    d := make([]byte, 64)
    enc, _ := rlp.EncodeToBytes(self.withoutNonce())
    copy(d[:32], enc)
    binary.BigEndian.PutUint32(d[60:], self.Nonce)
    return common.FirstBitSet(common.BigD(crypto.Sha3(d))) > 0
}

func (self *Envelope) withoutNonce() interface{} {
    return []interface{}{self.Expiry, self.TTL, self.Topics, self.Data}
}

// rlpenv is an Envelope but is not an rlp.Decoder.
// It is used for decoding because we need to
type rlpenv Envelope

func (self *Envelope) DecodeRLP(s *rlp.Stream) error {
    raw, err := s.Raw()
    if err != nil {
        return err
    }
    if err := rlp.DecodeBytes(raw, (*rlpenv)(self)); err != nil {
        return err
    }
    self.hash = crypto.Sha3Hash(raw)
    return nil
}