// 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 Envelope element.
package whisperv6
import (
"crypto/ecdsa"
"encoding/binary"
"fmt"
gmath "math"
"math/big"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"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
TTL uint32
Topic TopicType
Data []byte
Nonce uint64
pow float64 // Message-specific PoW as described in the Whisper specification.
// the following variables should not be accessed directly, use the corresponding function instead: Hash(), Bloom()
hash common.Hash // Cached hash of the envelope to avoid rehashing every time.
bloom []byte
}
// size returns the size of envelope as it is sent (i.e. public fields only)
func (e *Envelope) size() int {
return EnvelopeHeaderLength + len(e.Data)
}
// rlpWithoutNonce returns the RLP encoded envelope contents, except the nonce.
func (e *Envelope) rlpWithoutNonce() []byte {
res, _ := rlp.EncodeToBytes([]interface{}{e.Expiry, e.TTL, e.Topic, e.Data})
return res
}
// NewEnvelope wraps a Whisper message with expiration and destination data
// included into an envelope for network forwarding.
func NewEnvelope(ttl uint32, topic TopicType, msg *sentMessage) *Envelope {
env := Envelope{
Expiry: uint32(time.Now().Add(time.Second * time.Duration(ttl)).Unix()),
TTL: ttl,
Topic: topic,
Data: msg.Raw,
Nonce: 0,
}
return &env
}
// Seal closes the envelope by spending the requested amount of time as a proof
// of work on hashing the data.
func (e *Envelope) Seal(options *MessageParams) error {
if options.PoW == 0 {
// PoW is not required
return nil
}
var target, bestBit int
if options.PoW < 0 {
// target is not set - the function should run for a period
// of time specified in WorkTime param. Since we can predict
// the execution time, we can also adjust Expiry.
e.Expiry += options.WorkTime
} else {
target = e.powToFirstBit(options.PoW)
}
buf := make([]byte, 64)
h := crypto.Keccak256(e.rlpWithoutNonce())
copy(buf[:32], h)
finish := time.Now().Add(time.Duration(options.WorkTime) * time.Second).UnixNano()
for nonce := uint64(0); time.Now().UnixNano() < finish; {
for i := 0; i < 1024; i++ {
binary.BigEndian.PutUint64(buf[56:], nonce)
d := new(big.Int).SetBytes(crypto.Keccak256(buf))
firstBit := math.FirstBitSet(d)
if firstBit > bestBit {
e.Nonce, bestBit = nonce, firstBit
if target > 0 && bestBit >= target {
return nil
}
}
nonce++
}
}
if target > 0 && bestBit < target {
return fmt.Errorf("failed to reach the PoW target, specified pow time (%d seconds) was insufficient", options.WorkTime)
}
return nil
}
// PoW computes (if necessary) and returns the proof of work target
// of the envelope.
func (e *Envelope) PoW() float64 {
if e.pow == 0 {
e.calculatePoW(0)
}
return e.pow
}
func (e *Envelope) calculatePoW(diff uint32) {
buf := make([]byte, 64)
h := crypto.Keccak256(e.rlpWithoutNonce())
copy(buf[:32], h)
binary.BigEndian.PutUint64(buf[56:], e.Nonce)
d := new(big.Int).SetBytes(crypto.Keccak256(buf))
firstBit := math.FirstBitSet(d)
x := gmath.Pow(2, float64(firstBit))
x /= float64(e.size())
x /= float64(e.TTL + diff)
e.pow = x
}
func (e *Envelope) powToFirstBit(pow float64) int {
x := pow
x *= float64(e.size())
x *= float64(e.TTL)
bits := gmath.Log2(x)
bits = gmath.Ceil(bits)
res := int(bits)
if res < 1 {
res = 1
}
return res
}
// Hash returns the SHA3 hash of the envelope, calculating it if not yet done.
func (e *Envelope) Hash() common.Hash {
if (e.hash == common.Hash{}) {
encoded, _ := rlp.EncodeToBytes(e)
e.hash = crypto.Keccak256Hash(encoded)
}
return e.hash
}
// DecodeRLP decodes an Envelope from an RLP data stream.
func (e *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 (does not implement DecodeRLP function).
// Only public members will be encoded.
type rlpenv Envelope
if err := rlp.DecodeBytes(raw, (*rlpenv)(e)); err != nil {
return err
}
e.hash = crypto.Keccak256Hash(raw)
return nil
}
// OpenAsymmetric tries to decrypt an envelope, potentially encrypted with a particular key.
func (e *Envelope) OpenAsymmetric(key *ecdsa.PrivateKey) (*ReceivedMessage, error) {
message := &ReceivedMessage{Raw: e.Data}
err := message.decryptAsymmetric(key)
switch err {
case nil:
return message, nil
case ecies.ErrInvalidPublicKey: // addressed to somebody else
return nil, err
default:
return nil, fmt.Errorf("unable to open envelope, decrypt failed: %v", err)
}
}
// OpenSymmetric tries to decrypt an envelope, potentially encrypted with a particular key.
func (e *Envelope) OpenSymmetric(key []byte) (msg *ReceivedMessage, err error) {
msg = &ReceivedMessage{Raw: e.Data}
err = msg.decryptSymmetric(key)
if err != nil {
msg = nil
}
return msg, err
}
// Open tries to decrypt an envelope, and populates the message fields in case of success.
func (e *Envelope) Open(watcher *Filter) (msg *ReceivedMessage) {
// The API interface forbids filters doing both symmetric and asymmetric encryption.
if watcher.expectsAsymmetricEncryption() && watcher.expectsSymmetricEncryption() {
return nil
}
if watcher.expectsAsymmetricEncryption() {
msg, _ = e.OpenAsymmetric(watcher.KeyAsym)
if msg != nil {
msg.Dst = &watcher.KeyAsym.PublicKey
}
} else if watcher.expectsSymmetricEncryption() {
msg, _ = e.OpenSymmetric(watcher.KeySym)
if msg != nil {
msg.SymKeyHash = crypto.Keccak256Hash(watcher.KeySym)
}
}
if msg != nil {
ok := msg.ValidateAndParse()
if !ok {
return nil
}
msg.Topic = e.Topic
msg.PoW = e.PoW()
msg.TTL = e.TTL
msg.Sent = e.Expiry - e.TTL
msg.EnvelopeHash = e.Hash()
}
return msg
}
// Bloom maps 4-bytes Topic into 64-byte bloom filter with 3 bits set (at most).
func (e *Envelope) Bloom() []byte {
if e.bloom == nil {
e.bloom = TopicToBloom(e.Topic)
}
return e.bloom
}
// TopicToBloom converts the topic (4 bytes) to the bloom filter (64 bytes)
func TopicToBloom(topic TopicType) []byte {
b := make([]byte, bloomFilterSize)
var index [3]int
for j := 0; j < 3; j++ {
index[j] = int(topic[j])
if (topic[3] & (1 << uint(j))) != 0 {
index[j] += 256
}
}
for j := 0; j < 3; j++ {
byteIndex := index[j] / 8
bitIndex := index[j] % 8
b[byteIndex] = (1 << uint(bitIndex))
}
return b
}
