path: root/whisper/whisper.go

// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// go-ethereum 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/>.

package whisper

import (
    "crypto/ecdsa"
    "sync"
    "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/event/filter"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/p2p"
    "gopkg.in/fatih/set.v0"
)

const (
    statusCode   = 0x00
    messagesCode = 0x01

    protocolVersion uint64 = 0x02
    protocolName           = "shh"

    signatureFlag   = byte(1 << 7)
    signatureLength = 65

    expirationCycle   = 800 * time.Millisecond
    transmissionCycle = 300 * time.Millisecond
)

const (
    DefaultTTL = 50 * time.Second
    DefaultPoW = 50 * time.Millisecond
)

type MessageEvent struct {
    To      *ecdsa.PrivateKey
    From    *ecdsa.PublicKey
    Message *Message
}

// Whisper represents a dark communication interface through the Ethereum
// network, using its very own P2P communication layer.
type Whisper struct {
    protocol p2p.Protocol
    filters  *filter.Filters

    keys map[string]*ecdsa.PrivateKey

    messages    map[common.Hash]*Envelope // Pool of messages currently tracked by this node
    expirations map[uint32]*set.SetNonTS  // Message expiration pool (TODO: something lighter)
    poolMu      sync.RWMutex              // Mutex to sync the message and expiration pools

    peers  map[*peer]struct{} // Set of currently active peers
    peerMu sync.RWMutex       // Mutex to sync the active peer set

    quit chan struct{}
}

// New creates a Whisper client ready to communicate through the Ethereum P2P
// network.
func New() *Whisper {
    whisper := &Whisper{
        filters:     filter.New(),
        keys:        make(map[string]*ecdsa.PrivateKey),
        messages:    make(map[common.Hash]*Envelope),
        expirations: make(map[uint32]*set.SetNonTS),
        peers:       make(map[*peer]struct{}),
        quit:        make(chan struct{}),
    }
    whisper.filters.Start()

    // p2p whisper sub protocol handler
    whisper.protocol = p2p.Protocol{
        Name:    protocolName,
        Version: uint(protocolVersion),
        Length:  2,
        Run:     whisper.handlePeer,
    }

    return whisper
}

// Protocol returns the whisper sub-protocol handler for this particular client.
func (self *Whisper) Protocol() p2p.Protocol {
    return self.protocol
}

// Version returns the whisper sub-protocols version number.
func (self *Whisper) Version() uint {
    return self.protocol.Version
}

// NewIdentity generates a new cryptographic identity for the client, and injects
// it into the known identities for message decryption.
func (self *Whisper) NewIdentity() *ecdsa.PrivateKey {
    key, err := crypto.GenerateKey()
    if err != nil {
        panic(err)
    }
    self.keys[string(crypto.FromECDSAPub(&key.PublicKey))] = key

    return key
}

// HasIdentity checks if the the whisper node is configured with the private key
// of the specified public pair.
func (self *Whisper) HasIdentity(key *ecdsa.PublicKey) bool {
    return self.keys[string(crypto.FromECDSAPub(key))] != nil
}

// GetIdentity retrieves the private key of the specified public identity.
func (self *Whisper) GetIdentity(key *ecdsa.PublicKey) *ecdsa.PrivateKey {
    return self.keys[string(crypto.FromECDSAPub(key))]
}

// Watch installs a new message handler to run in case a matching packet arrives
// from the whisper network.
func (self *Whisper) Watch(options Filter) int {
    filter := filterer{
        to:      string(crypto.FromECDSAPub(options.To)),
        from:    string(crypto.FromECDSAPub(options.From)),
        matcher: newTopicMatcher(options.Topics...),
        fn: func(data interface{}) {
            options.Fn(data.(*Message))
        },
    }
    return self.filters.Install(filter)
}

// Unwatch removes an installed message handler.
func (self *Whisper) Unwatch(id int) {
    self.filters.Uninstall(id)
}

// Send injects a message into the whisper send queue, to be distributed in the
// network in the coming cycles.
func (self *Whisper) Send(envelope *Envelope) error {
    return self.add(envelope)
}

func (self *Whisper) Start() {
    glog.V(logger.Info).Infoln("Whisper started")
    go self.update()
}

func (self *Whisper) Stop() {
    close(self.quit)
    glog.V(logger.Info).Infoln("Whisper stopped")
}

// Messages retrieves all the currently pooled messages matching a filter id.
func (self *Whisper) Messages(id int) []*Message {
    messages := make([]*Message, 0)
    if filter := self.filters.Get(id); filter != nil {
        for _, envelope := range self.messages {
            if message := self.open(envelope); message != nil {
                if self.filters.Match(filter, createFilter(message, envelope.Topics)) {
                    messages = append(messages, message)
                }
            }
        }
    }
    return messages
}

// handlePeer is called by the underlying P2P layer when the whisper sub-protocol
// connection is negotiated.
func (self *Whisper) handlePeer(peer *p2p.Peer, rw p2p.MsgReadWriter) error {
    // Create the new peer and start tracking it
    whisperPeer := newPeer(self, peer, rw)

    self.peerMu.Lock()
    self.peers[whisperPeer] = struct{}{}
    self.peerMu.Unlock()

    defer func() {
        self.peerMu.Lock()
        delete(self.peers, whisperPeer)
        self.peerMu.Unlock()
    }()

    // Run the peer handshake and state updates
    if err := whisperPeer.handshake(); err != nil {
        return err
    }
    whisperPeer.start()
    defer whisperPeer.stop()

    // Read and process inbound messages directly to merge into client-global state
    for {
        // Fetch the next packet and decode the contained envelopes
        packet, err := rw.ReadMsg()
        if err != nil {
            return err
        }
        var envelopes []*Envelope
        if err := packet.Decode(&envelopes); err != nil {
            glog.V(logger.Info).Infof("%v: failed to decode envelope: %v", peer, err)
            continue
        }
        // Inject all envelopes into the internal pool
        for _, envelope := range envelopes {
            if err := self.add(envelope); err != nil {
                // TODO Punish peer here. Invalid envelope.
                glog.V(logger.Debug).Infof("%v: failed to pool envelope: %v", peer, err)
            }
            whisperPeer.mark(envelope)
        }
    }
}

// add inserts a new envelope into the message pool to be distributed within the
// whisper network. It also inserts the envelope into the expiration pool at the
// appropriate time-stamp.
func (self *Whisper) add(envelope *Envelope) error {
    self.poolMu.Lock()
    defer self.poolMu.Unlock()

    // Insert the message into the tracked pool
    hash := envelope.Hash()
    if _, ok := self.messages[hash]; ok {
        glog.V(logger.Detail).Infof("whisper envelope already cached: %x\n", envelope)
        return nil
    }
    self.messages[hash] = envelope

    // Insert the message into the expiration pool for later removal
    if self.expirations[envelope.Expiry] == nil {
        self.expirations[envelope.Expiry] = set.NewNonTS()
    }
    if !self.expirations[envelope.Expiry].Has(hash) {
        self.expirations[envelope.Expiry].Add(hash)

        // Notify the local node of a message arrival
        go self.postEvent(envelope)
    }
    glog.V(logger.Detail).Infof("cached whisper envelope %x\n", envelope)

    return nil
}

// postEvent opens an envelope with the configured identities and delivers the
// message upstream from application processing.
func (self *Whisper) postEvent(envelope *Envelope) {
    if message := self.open(envelope); message != nil {
        self.filters.Notify(createFilter(message, envelope.Topics), message)
    }
}

// open tries to decrypt a whisper envelope with all the configured identities,
// returning the decrypted message and the key used to achieve it. If not keys
// are configured, open will return the payload as if non encrypted.
func (self *Whisper) open(envelope *Envelope) *Message {
    // Short circuit if no identity is set, and assume clear-text
    if len(self.keys) == 0 {
        if message, err := envelope.Open(nil); err == nil {
            return message
        }
    }
    // Iterate over the keys and try to decrypt the message
    for _, key := range self.keys {
        message, err := envelope.Open(key)
        if err == nil {
            message.To = &key.PublicKey
            return message
        } else if err == ecies.ErrInvalidPublicKey {
            return message
        }
    }
    // Failed to decrypt, don't return anything
    return nil
}

// createFilter creates a message filter to check against installed handlers.
func createFilter(message *Message, topics []Topic) filter.Filter {
    matcher := make([][]Topic, len(topics))
    for i, topic := range topics {
        matcher[i] = []Topic{topic}
    }
    return filterer{
        to:      string(crypto.FromECDSAPub(message.To)),
        from:    string(crypto.FromECDSAPub(message.Recover())),
        matcher: newTopicMatcher(matcher...),
    }
}

// update loops until the lifetime of the whisper node, updating its internal
// state by expiring stale messages from the pool.
func (self *Whisper) update() {
    // Start a ticker to check for expirations
    expire := time.NewTicker(expirationCycle)

    // Repeat updates until termination is requested
    for {
        select {
        case <-expire.C:
            self.expire()

        case <-self.quit:
            return
        }
    }
}

// expire iterates over all the expiration timestamps, removing all stale
// messages from the pools.
func (self *Whisper) expire() {
    self.poolMu.Lock()
    defer self.poolMu.Unlock()

    now := uint32(time.Now().Unix())
    for then, hashSet := range self.expirations {
        // Short circuit if a future time
        if then > now {
            continue
        }
        // Dump all expired messages and remove timestamp
        hashSet.Each(func(v interface{}) bool {
            delete(self.messages, v.(common.Hash))
            return true
        })
        self.expirations[then].Clear()
    }
}

// envelopes retrieves all the messages currently pooled by the node.
func (self *Whisper) envelopes() []*Envelope {
    self.poolMu.RLock()
    defer self.poolMu.RUnlock()

    envelopes := make([]*Envelope, 0, len(self.messages))
    for _, envelope := range self.messages {
        envelopes = append(envelopes, envelope)
    }
    return envelopes
}