path: root/whisper/envelope.go

package whisper

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

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

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 Hash
}

func NewEnvelopeFromReader(reader io.Reader) (*Envelope, error) {
    var envelope Envelope

    buf := new(bytes.Buffer)
    buf.ReadFrom(reader)

    h := H(crypto.Sha3(buf.Bytes()))
    if err := rlp.Decode(buf, &envelope); err != nil {
        return nil, err
    }

    envelope.hash = h

    return &envelope, nil
}

func (self *Envelope) Hash() Hash {
    if self.hash == EmptyHash {
        self.hash = H(crypto.Sha3(ethutil.Encode(self)))
    }

    return self.hash
}

func NewEnvelope(ttl time.Duration, topics [][]byte, data *Message) *Envelope {
    exp := time.Now().Add(ttl)

    return &Envelope{uint32(exp.Unix()), uint32(ttl.Seconds()), topics, data.Bytes(), 0, Hash{}}
}

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

func (self *Envelope) Open(prv *ecdsa.PrivateKey) (msg *Message, err error) {
    data := self.Data
    var message Message
    dataStart := 1
    if data[0] > 0 {
        if len(data) < 66 {
            return nil, fmt.Errorf("unable to open envelope. First bit set but len(data) < 66")
        }
        dataStart = 66
        message.Flags = data[0]
        message.Signature = data[1:66]
    }

    payload := data[dataStart:]
    if prv != nil {
        message.Payload, err = crypto.Decrypt(prv, payload)
        switch err {
        case nil: // OK
        case ecies.ErrInvalidPublicKey: // Payload isn't encrypted
            message.Payload = payload
            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)
    copy(d[:32], ethutil.Encode(self.withoutNonce()))

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

            n++
        }
    }
}

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

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

func (self *Envelope) RlpData() interface{} {
    return []interface{}{self.Expiry, self.Ttl, ethutil.ByteSliceToInterface(self.Topics), self.Data, self.Nonce}
}