path: root/whisper/whisperv6/whisper.go

// 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/>.

package whisperv6

import (
    "bytes"
    "crypto/ecdsa"
    "crypto/sha256"
    "fmt"
    "math"
    "runtime"
    "sync"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/rlp"
    "github.com/ethereum/go-ethereum/rpc"
    "github.com/syndtr/goleveldb/leveldb/errors"
    "golang.org/x/crypto/pbkdf2"
    "golang.org/x/sync/syncmap"
)

// Statistics holds several message-related counter for analytics
// purposes.
type Statistics struct {
    messagesCleared      int
    memoryCleared        int
    memoryUsed           int
    cycles               int
    totalMessagesCleared int
}

const (
    maxMsgSizeIdx           = iota // Maximal message length allowed by the whisper node
    overflowIdx                    // Indicator of message queue overflow
    minPowIdx                      // Minimal PoW required by the whisper node
    minPowToleranceIdx             // Minimal PoW tolerated by the whisper node for a limited time
    bloomFilterIdx                 // Bloom filter for topics of interest for this node
    bloomFilterToleranceIdx        // Bloom filter tolerated by the whisper node for a limited time
)

// Whisper represents a dark communication interface through the Ethereum
// network, using its very own P2P communication layer.
type Whisper struct {
    protocol p2p.Protocol // Protocol description and parameters
    filters  *Filters     // Message filters installed with Subscribe function

    privateKeys map[string]*ecdsa.PrivateKey // Private key storage
    symKeys     map[string][]byte            // Symmetric key storage
    keyMu       sync.RWMutex                 // Mutex associated with key storages

    poolMu      sync.RWMutex              // Mutex to sync the message and expiration pools
    envelopes   map[common.Hash]*Envelope // Pool of envelopes currently tracked by this node
    expirations map[uint32]mapset.Set     // Message expiration pool

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

    messageQueue chan *Envelope // Message queue for normal whisper messages
    p2pMsgQueue  chan *Envelope // Message queue for peer-to-peer messages (not to be forwarded any further)
    quit         chan struct{}  // Channel used for graceful exit

    settings syncmap.Map // holds configuration settings that can be dynamically changed

    syncAllowance int // maximum time in seconds allowed to process the whisper-related messages

    lightClient bool // indicates is this node is pure light client (does not forward any messages)

    statsMu sync.Mutex // guard stats
    stats   Statistics // Statistics of whisper node

    mailServer MailServer // MailServer interface
}

// New creates a Whisper client ready to communicate through the Ethereum P2P network.
func New(cfg *Config) *Whisper {
    if cfg == nil {
        cfg = &DefaultConfig
    }

    whisper := &Whisper{
        privateKeys:   make(map[string]*ecdsa.PrivateKey),
        symKeys:       make(map[string][]byte),
        envelopes:     make(map[common.Hash]*Envelope),
        expirations:   make(map[uint32]mapset.Set),
        peers:         make(map[*Peer]struct{}),
        messageQueue:  make(chan *Envelope, messageQueueLimit),
        p2pMsgQueue:   make(chan *Envelope, messageQueueLimit),
        quit:          make(chan struct{}),
        syncAllowance: DefaultSyncAllowance,
    }

    whisper.filters = NewFilters(whisper)

    whisper.settings.Store(minPowIdx, cfg.MinimumAcceptedPOW)
    whisper.settings.Store(maxMsgSizeIdx, cfg.MaxMessageSize)
    whisper.settings.Store(overflowIdx, false)

    // p2p whisper sub protocol handler
    whisper.protocol = p2p.Protocol{
        Name:    ProtocolName,
        Version: uint(ProtocolVersion),
        Length:  NumberOfMessageCodes,
        Run:     whisper.HandlePeer,
        NodeInfo: func() interface{} {
            return map[string]interface{}{
                "version":        ProtocolVersionStr,
                "maxMessageSize": whisper.MaxMessageSize(),
                "minimumPoW":     whisper.MinPow(),
            }
        },
    }

    return whisper
}

// MinPow returns the PoW value required by this node.
func (whisper *Whisper) MinPow() float64 {
    val, exist := whisper.settings.Load(minPowIdx)
    if !exist || val == nil {
        return DefaultMinimumPoW
    }
    v, ok := val.(float64)
    if !ok {
        log.Error("Error loading minPowIdx, using default")
        return DefaultMinimumPoW
    }
    return v
}

// MinPowTolerance returns the value of minimum PoW which is tolerated for a limited
// time after PoW was changed. If sufficient time have elapsed or no change of PoW
// have ever occurred, the return value will be the same as return value of MinPow().
func (whisper *Whisper) MinPowTolerance() float64 {
    val, exist := whisper.settings.Load(minPowToleranceIdx)
    if !exist || val == nil {
        return DefaultMinimumPoW
    }
    return val.(float64)
}

// BloomFilter returns the aggregated bloom filter for all the topics of interest.
// The nodes are required to send only messages that match the advertised bloom filter.
// If a message does not match the bloom, it will tantamount to spam, and the peer will
// be disconnected.
func (whisper *Whisper) BloomFilter() []byte {
    val, exist := whisper.settings.Load(bloomFilterIdx)
    if !exist || val == nil {
        return nil
    }
    return val.([]byte)
}

// BloomFilterTolerance returns the bloom filter which is tolerated for a limited
// time after new bloom was advertised to the peers. If sufficient time have elapsed
// or no change of bloom filter have ever occurred, the return value will be the same
// as return value of BloomFilter().
func (whisper *Whisper) BloomFilterTolerance() []byte {
    val, exist := whisper.settings.Load(bloomFilterToleranceIdx)
    if !exist || val == nil {
        return nil
    }
    return val.([]byte)
}

// MaxMessageSize returns the maximum accepted message size.
func (whisper *Whisper) MaxMessageSize() uint32 {
    val, _ := whisper.settings.Load(maxMsgSizeIdx)
    return val.(uint32)
}

// Overflow returns an indication if the message queue is full.
func (whisper *Whisper) Overflow() bool {
    val, _ := whisper.settings.Load(overflowIdx)
    return val.(bool)
}

// APIs returns the RPC descriptors the Whisper implementation offers
func (whisper *Whisper) APIs() []rpc.API {
    return []rpc.API{
        {
            Namespace: ProtocolName,
            Version:   ProtocolVersionStr,
            Service:   NewPublicWhisperAPI(whisper),
            Public:    true,
        },
    }
}

// RegisterServer registers MailServer interface.
// MailServer will process all the incoming messages with p2pRequestCode.
func (whisper *Whisper) RegisterServer(server MailServer) {
    whisper.mailServer = server
}

// Protocols returns the whisper sub-protocols ran by this particular client.
func (whisper *Whisper) Protocols() []p2p.Protocol {
    return []p2p.Protocol{whisper.protocol}
}

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

// SetMaxMessageSize sets the maximal message size allowed by this node
func (whisper *Whisper) SetMaxMessageSize(size uint32) error {
    if size > MaxMessageSize {
        return fmt.Errorf("message size too large [%d>%d]", size, MaxMessageSize)
    }
    whisper.settings.Store(maxMsgSizeIdx, size)
    return nil
}

// SetBloomFilter sets the new bloom filter
func (whisper *Whisper) SetBloomFilter(bloom []byte) error {
    if len(bloom) != BloomFilterSize {
        return fmt.Errorf("invalid bloom filter size: %d", len(bloom))
    }

    b := make([]byte, BloomFilterSize)
    copy(b, bloom)

    whisper.settings.Store(bloomFilterIdx, b)
    whisper.notifyPeersAboutBloomFilterChange(b)

    go func() {
        // allow some time before all the peers have processed the notification
        time.Sleep(time.Duration(whisper.syncAllowance) * time.Second)
        whisper.settings.Store(bloomFilterToleranceIdx, b)
    }()

    return nil
}

// SetMinimumPoW sets the minimal PoW required by this node
func (whisper *Whisper) SetMinimumPoW(val float64) error {
    if val < 0.0 {
        return fmt.Errorf("invalid PoW: %f", val)
    }

    whisper.settings.Store(minPowIdx, val)
    whisper.notifyPeersAboutPowRequirementChange(val)

    go func() {
        // allow some time before all the peers have processed the notification
        time.Sleep(time.Duration(whisper.syncAllowance) * time.Second)
        whisper.settings.Store(minPowToleranceIdx, val)
    }()

    return nil
}

// SetMinimumPowTest sets the minimal PoW in test environment
func (whisper *Whisper) SetMinimumPowTest(val float64) {
    whisper.settings.Store(minPowIdx, val)
    whisper.notifyPeersAboutPowRequirementChange(val)
    whisper.settings.Store(minPowToleranceIdx, val)
}

func (whisper *Whisper) notifyPeersAboutPowRequirementChange(pow float64) {
    arr := whisper.getPeers()
    for _, p := range arr {
        err := p.notifyAboutPowRequirementChange(pow)
        if err != nil {
            // allow one retry
            err = p.notifyAboutPowRequirementChange(pow)
        }
        if err != nil {
            log.Warn("failed to notify peer about new pow requirement", "peer", p.ID(), "error", err)
        }
    }
}

func (whisper *Whisper) notifyPeersAboutBloomFilterChange(bloom []byte) {
    arr := whisper.getPeers()
    for _, p := range arr {
        err := p.notifyAboutBloomFilterChange(bloom)
        if err != nil {
            // allow one retry
            err = p.notifyAboutBloomFilterChange(bloom)
        }
        if err != nil {
            log.Warn("failed to notify peer about new bloom filter", "peer", p.ID(), "error", err)
        }
    }
}

func (whisper *Whisper) getPeers() []*Peer {
    arr := make([]*Peer, len(whisper.peers))
    i := 0
    whisper.peerMu.Lock()
    for p := range whisper.peers {
        arr[i] = p
        i++
    }
    whisper.peerMu.Unlock()
    return arr
}

// getPeer retrieves peer by ID
func (whisper *Whisper) getPeer(peerID []byte) (*Peer, error) {
    whisper.peerMu.Lock()
    defer whisper.peerMu.Unlock()
    for p := range whisper.peers {
        id := p.peer.ID()
        if bytes.Equal(peerID, id[:]) {
            return p, nil
        }
    }
    return nil, fmt.Errorf("Could not find peer with ID: %x", peerID)
}

// AllowP2PMessagesFromPeer marks specific peer trusted,
// which will allow it to send historic (expired) messages.
func (whisper *Whisper) AllowP2PMessagesFromPeer(peerID []byte) error {
    p, err := whisper.getPeer(peerID)
    if err != nil {
        return err
    }
    p.trusted = true
    return nil
}

// RequestHistoricMessages sends a message with p2pRequestCode to a specific peer,
// which is known to implement MailServer interface, and is supposed to process this
// request and respond with a number of peer-to-peer messages (possibly expired),
// which are not supposed to be forwarded any further.
// The whisper protocol is agnostic of the format and contents of envelope.
func (whisper *Whisper) RequestHistoricMessages(peerID []byte, envelope *Envelope) error {
    p, err := whisper.getPeer(peerID)
    if err != nil {
        return err
    }
    p.trusted = true
    return p2p.Send(p.ws, p2pRequestCode, envelope)
}

// SendP2PMessage sends a peer-to-peer message to a specific peer.
func (whisper *Whisper) SendP2PMessage(peerID []byte, envelope *Envelope) error {
    p, err := whisper.getPeer(peerID)
    if err != nil {
        return err
    }
    return whisper.SendP2PDirect(p, envelope)
}

// SendP2PDirect sends a peer-to-peer message to a specific peer.
func (whisper *Whisper) SendP2PDirect(peer *Peer, envelope *Envelope) error {
    return p2p.Send(peer.ws, p2pMessageCode, envelope)
}

// NewKeyPair generates a new cryptographic identity for the client, and injects
// it into the known identities for message decryption. Returns ID of the new key pair.
func (whisper *Whisper) NewKeyPair() (string, error) {
    key, err := crypto.GenerateKey()
    if err != nil || !validatePrivateKey(key) {
        key, err = crypto.GenerateKey() // retry once
    }
    if err != nil {
        return "", err
    }
    if !validatePrivateKey(key) {
        return "", fmt.Errorf("failed to generate valid key")
    }

    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.privateKeys[id] != nil {
        return "", fmt.Errorf("failed to generate unique ID")
    }
    whisper.privateKeys[id] = key
    return id, nil
}

// DeleteKeyPair deletes the specified key if it exists.
func (whisper *Whisper) DeleteKeyPair(key string) bool {
    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.privateKeys[key] != nil {
        delete(whisper.privateKeys, key)
        return true
    }
    return false
}

// AddKeyPair imports a asymmetric private key and returns it identifier.
func (whisper *Whisper) AddKeyPair(key *ecdsa.PrivateKey) (string, error) {
    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    whisper.privateKeys[id] = key
    whisper.keyMu.Unlock()

    return id, nil
}

// HasKeyPair checks if the the whisper node is configured with the private key
// of the specified public pair.
func (whisper *Whisper) HasKeyPair(id string) bool {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    return whisper.privateKeys[id] != nil
}

// GetPrivateKey retrieves the private key of the specified identity.
func (whisper *Whisper) GetPrivateKey(id string) (*ecdsa.PrivateKey, error) {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    key := whisper.privateKeys[id]
    if key == nil {
        return nil, fmt.Errorf("invalid id")
    }
    return key, nil
}

// GenerateSymKey generates a random symmetric key and stores it under id,
// which is then returned. Will be used in the future for session key exchange.
func (whisper *Whisper) GenerateSymKey() (string, error) {
    key, err := generateSecureRandomData(aesKeyLength)
    if err != nil {
        return "", err
    } else if !validateDataIntegrity(key, aesKeyLength) {
        return "", fmt.Errorf("error in GenerateSymKey: crypto/rand failed to generate random data")
    }

    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.symKeys[id] != nil {
        return "", fmt.Errorf("failed to generate unique ID")
    }
    whisper.symKeys[id] = key
    return id, nil
}

// AddSymKeyDirect stores the key, and returns its id.
func (whisper *Whisper) AddSymKeyDirect(key []byte) (string, error) {
    if len(key) != aesKeyLength {
        return "", fmt.Errorf("wrong key size: %d", len(key))
    }

    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.symKeys[id] != nil {
        return "", fmt.Errorf("failed to generate unique ID")
    }
    whisper.symKeys[id] = key
    return id, nil
}

// AddSymKeyFromPassword generates the key from password, stores it, and returns its id.
func (whisper *Whisper) AddSymKeyFromPassword(password string) (string, error) {
    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }
    if whisper.HasSymKey(id) {
        return "", fmt.Errorf("failed to generate unique ID")
    }

    // kdf should run no less than 0.1 seconds on an average computer,
    // because it's an once in a session experience
    derived := pbkdf2.Key([]byte(password), nil, 65356, aesKeyLength, sha256.New)
    if err != nil {
        return "", err
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    // double check is necessary, because deriveKeyMaterial() is very slow
    if whisper.symKeys[id] != nil {
        return "", fmt.Errorf("critical error: failed to generate unique ID")
    }
    whisper.symKeys[id] = derived
    return id, nil
}

// HasSymKey returns true if there is a key associated with the given id.
// Otherwise returns false.
func (whisper *Whisper) HasSymKey(id string) bool {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    return whisper.symKeys[id] != nil
}

// DeleteSymKey deletes the key associated with the name string if it exists.
func (whisper *Whisper) DeleteSymKey(id string) bool {
    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()
    if whisper.symKeys[id] != nil {
        delete(whisper.symKeys, id)
        return true
    }
    return false
}

// GetSymKey returns the symmetric key associated with the given id.
func (whisper *Whisper) GetSymKey(id string) ([]byte, error) {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    if whisper.symKeys[id] != nil {
        return whisper.symKeys[id], nil
    }
    return nil, fmt.Errorf("non-existent key ID")
}

// Subscribe installs a new message handler used for filtering, decrypting
// and subsequent storing of incoming messages.
func (whisper *Whisper) Subscribe(f *Filter) (string, error) {
    s, err := whisper.filters.Install(f)
    if err == nil {
        whisper.updateBloomFilter(f)
    }
    return s, err
}

// updateBloomFilter recalculates the new value of bloom filter,
// and informs the peers if necessary.
func (whisper *Whisper) updateBloomFilter(f *Filter) {
    aggregate := make([]byte, BloomFilterSize)
    for _, t := range f.Topics {
        top := BytesToTopic(t)
        b := TopicToBloom(top)
        aggregate = addBloom(aggregate, b)
    }

    if !BloomFilterMatch(whisper.BloomFilter(), aggregate) {
        // existing bloom filter must be updated
        aggregate = addBloom(whisper.BloomFilter(), aggregate)
        whisper.SetBloomFilter(aggregate)
    }
}

// GetFilter returns the filter by id.
func (whisper *Whisper) GetFilter(id string) *Filter {
    return whisper.filters.Get(id)
}

// Unsubscribe removes an installed message handler.
func (whisper *Whisper) Unsubscribe(id string) error {
    ok := whisper.filters.Uninstall(id)
    if !ok {
        return fmt.Errorf("Unsubscribe: Invalid ID")
    }
    return nil
}

// Send injects a message into the whisper send queue, to be distributed in the
// network in the coming cycles.
func (whisper *Whisper) Send(envelope *Envelope) error {
    ok, err := whisper.add(envelope, false)
    if err == nil && !ok {
        return fmt.Errorf("failed to add envelope")
    }
    return err
}

// Start implements node.Service, starting the background data propagation thread
// of the Whisper protocol.
func (whisper *Whisper) Start(*p2p.Server) error {
    log.Info("started whisper v." + ProtocolVersionStr)
    go whisper.update()

    numCPU := runtime.NumCPU()
    for i := 0; i < numCPU; i++ {
        go whisper.processQueue()
    }

    return nil
}

// Stop implements node.Service, stopping the background data propagation thread
// of the Whisper protocol.
func (whisper *Whisper) Stop() error {
    close(whisper.quit)
    log.Info("whisper stopped")
    return nil
}

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

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

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

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

    return whisper.runMessageLoop(whisperPeer, rw)
}

// runMessageLoop reads and processes inbound messages directly to merge into client-global state.
func (whisper *Whisper) runMessageLoop(p *Peer, rw p2p.MsgReadWriter) error {
    for {
        // fetch the next packet
        packet, err := rw.ReadMsg()
        if err != nil {
            log.Info("message loop", "peer", p.peer.ID(), "err", err)
            return err
        }
        if packet.Size > whisper.MaxMessageSize() {
            log.Warn("oversized message received", "peer", p.peer.ID())
            return errors.New("oversized message received")
        }

        switch packet.Code {
        case statusCode:
            // this should not happen, but no need to panic; just ignore this message.
            log.Warn("unxepected status message received", "peer", p.peer.ID())
        case messagesCode:
            // decode the contained envelopes
            var envelopes []*Envelope
            if err := packet.Decode(&envelopes); err != nil {
                log.Warn("failed to decode envelopes, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid envelopes")
            }

            trouble := false
            for _, env := range envelopes {
                cached, err := whisper.add(env, whisper.lightClient)
                if err != nil {
                    trouble = true
                    log.Error("bad envelope received, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                }
                if cached {
                    p.mark(env)
                }
            }

            if trouble {
                return errors.New("invalid envelope")
            }
        case powRequirementCode:
            s := rlp.NewStream(packet.Payload, uint64(packet.Size))
            i, err := s.Uint()
            if err != nil {
                log.Warn("failed to decode powRequirementCode message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid powRequirementCode message")
            }
            f := math.Float64frombits(i)
            if math.IsInf(f, 0) || math.IsNaN(f) || f < 0.0 {
                log.Warn("invalid value in powRequirementCode message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid value in powRequirementCode message")
            }
            p.powRequirement = f
        case bloomFilterExCode:
            var bloom []byte
            err := packet.Decode(&bloom)
            if err == nil && len(bloom) != BloomFilterSize {
                err = fmt.Errorf("wrong bloom filter size %d", len(bloom))
            }

            if err != nil {
                log.Warn("failed to decode bloom filter exchange message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid bloom filter exchange message")
            }
            p.setBloomFilter(bloom)
        case p2pMessageCode:
            // peer-to-peer message, sent directly to peer bypassing PoW checks, etc.
            // this message is not supposed to be forwarded to other peers, and
            // therefore might not satisfy the PoW, expiry and other requirements.
            // these messages are only accepted from the trusted peer.
            if p.trusted {
                var envelope Envelope
                if err := packet.Decode(&envelope); err != nil {
                    log.Warn("failed to decode direct message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                    return errors.New("invalid direct message")
                }
                whisper.postEvent(&envelope, true)
            }
        case p2pRequestCode:
            // Must be processed if mail server is implemented. Otherwise ignore.
            if whisper.mailServer != nil {
                var request Envelope
                if err := packet.Decode(&request); err != nil {
                    log.Warn("failed to decode p2p request message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                    return errors.New("invalid p2p request")
                }
                whisper.mailServer.DeliverMail(p, &request)
            }
        default:
            // New message types might be implemented in the future versions of Whisper.
            // For forward compatibility, just ignore.
        }

        packet.Discard()
    }
}

// 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. In case of error, connection should be dropped.
// param isP2P indicates whether the message is peer-to-peer (should not be forwarded).
func (whisper *Whisper) add(envelope *Envelope, isP2P bool) (bool, error) {
    now := uint32(time.Now().Unix())
    sent := envelope.Expiry - envelope.TTL

    if sent > now {
        if sent-DefaultSyncAllowance > now {
            return false, fmt.Errorf("envelope created in the future [%x]", envelope.Hash())
        }
        // recalculate PoW, adjusted for the time difference, plus one second for latency
        envelope.calculatePoW(sent - now + 1)
    }

    if envelope.Expiry < now {
        if envelope.Expiry+DefaultSyncAllowance*2 < now {
            return false, fmt.Errorf("very old message")
        }
        log.Debug("expired envelope dropped", "hash", envelope.Hash().Hex())
        return false, nil // drop envelope without error
    }

    if uint32(envelope.size()) > whisper.MaxMessageSize() {
        return false, fmt.Errorf("huge messages are not allowed [%x]", envelope.Hash())
    }

    if envelope.PoW() < whisper.MinPow() {
        // maybe the value was recently changed, and the peers did not adjust yet.
        // in this case the previous value is retrieved by MinPowTolerance()
        // for a short period of peer synchronization.
        if envelope.PoW() < whisper.MinPowTolerance() {
            return false, fmt.Errorf("envelope with low PoW received: PoW=%f, hash=[%v]", envelope.PoW(), envelope.Hash().Hex())
        }
    }

    if !BloomFilterMatch(whisper.BloomFilter(), envelope.Bloom()) {
        // maybe the value was recently changed, and the peers did not adjust yet.
        // in this case the previous value is retrieved by BloomFilterTolerance()
        // for a short period of peer synchronization.
        if !BloomFilterMatch(whisper.BloomFilterTolerance(), envelope.Bloom()) {
            return false, fmt.Errorf("envelope does not match bloom filter, hash=[%v], bloom: \n%x \n%x \n%x",
                envelope.Hash().Hex(), whisper.BloomFilter(), envelope.Bloom(), envelope.Topic)
        }
    }

    hash := envelope.Hash()

    whisper.poolMu.Lock()
    _, alreadyCached := whisper.envelopes[hash]
    if !alreadyCached {
        whisper.envelopes[hash] = envelope
        if whisper.expirations[envelope.Expiry] == nil {
            whisper.expirations[envelope.Expiry] = mapset.NewThreadUnsafeSet()
        }
        if !whisper.expirations[envelope.Expiry].Contains(hash) {
            whisper.expirations[envelope.Expiry].Add(hash)
        }
    }
    whisper.poolMu.Unlock()

    if alreadyCached {
        log.Trace("whisper envelope already cached", "hash", envelope.Hash().Hex())
    } else {
        log.Trace("cached whisper envelope", "hash", envelope.Hash().Hex())
        whisper.statsMu.Lock()
        whisper.stats.memoryUsed += envelope.size()
        whisper.statsMu.Unlock()
        whisper.postEvent(envelope, isP2P) // notify the local node about the new message
        if whisper.mailServer != nil {
            whisper.mailServer.Archive(envelope)
        }
    }
    return true, nil
}

// postEvent queues the message for further processing.
func (whisper *Whisper) postEvent(envelope *Envelope, isP2P bool) {
    if isP2P {
        whisper.p2pMsgQueue <- envelope
    } else {
        whisper.checkOverflow()
        whisper.messageQueue <- envelope
    }
}

// checkOverflow checks if message queue overflow occurs and reports it if necessary.
func (whisper *Whisper) checkOverflow() {
    queueSize := len(whisper.messageQueue)

    if queueSize == messageQueueLimit {
        if !whisper.Overflow() {
            whisper.settings.Store(overflowIdx, true)
            log.Warn("message queue overflow")
        }
    } else if queueSize <= messageQueueLimit/2 {
        if whisper.Overflow() {
            whisper.settings.Store(overflowIdx, false)
            log.Warn("message queue overflow fixed (back to normal)")
        }
    }
}

// processQueue delivers the messages to the watchers during the lifetime of the whisper node.
func (whisper *Whisper) processQueue() {
    var e *Envelope
    for {
        select {
        case <-whisper.quit:
            return

        case e = <-whisper.messageQueue:
            whisper.filters.NotifyWatchers(e, false)

        case e = <-whisper.p2pMsgQueue:
            whisper.filters.NotifyWatchers(e, true)
        }
    }
}

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

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

        case <-whisper.quit:
            return
        }
    }
}

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

    whisper.statsMu.Lock()
    defer whisper.statsMu.Unlock()
    whisper.stats.reset()
    now := uint32(time.Now().Unix())
    for expiry, hashSet := range whisper.expirations {
        if expiry < now {
            // Dump all expired messages and remove timestamp
            hashSet.Each(func(v interface{}) bool {
                sz := whisper.envelopes[v.(common.Hash)].size()
                delete(whisper.envelopes, v.(common.Hash))
                whisper.stats.messagesCleared++
                whisper.stats.memoryCleared += sz
                whisper.stats.memoryUsed -= sz
                return true
            })
            whisper.expirations[expiry].Clear()
            delete(whisper.expirations, expiry)
        }
    }
}

// Stats returns the whisper node statistics.
func (whisper *Whisper) Stats() Statistics {
    whisper.statsMu.Lock()
    defer whisper.statsMu.Unlock()

    return whisper.stats
}

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

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

// isEnvelopeCached checks if envelope with specific hash has already been received and cached.
func (whisper *Whisper) isEnvelopeCached(hash common.Hash) bool {
    whisper.poolMu.Lock()
    defer whisper.poolMu.Unlock()

    _, exist := whisper.envelopes[hash]
    return exist
}

// reset resets the node's statistics after each expiry cycle.
func (s *Statistics) reset() {
    s.cycles++
    s.totalMessagesCleared += s.messagesCleared

    s.memoryCleared = 0
    s.messagesCleared = 0
}

// ValidatePublicKey checks the format of the given public key.
func ValidatePublicKey(k *ecdsa.PublicKey) bool {
    return k != nil && k.X != nil && k.Y != nil && k.X.Sign() != 0 && k.Y.Sign() != 0
}

// validatePrivateKey checks the format of the given private key.
func validatePrivateKey(k *ecdsa.PrivateKey) bool {
    if k == nil || k.D == nil || k.D.Sign() == 0 {
        return false
    }
    return ValidatePublicKey(&k.PublicKey)
}

// validateDataIntegrity returns false if the data have the wrong or contains all zeros,
// which is the simplest and the most common bug.
func validateDataIntegrity(k []byte, expectedSize int) bool {
    if len(k) != expectedSize {
        return false
    }
    if expectedSize > 3 && containsOnlyZeros(k) {
        return false
    }
    return true
}

// containsOnlyZeros checks if the data contain only zeros.
func containsOnlyZeros(data []byte) bool {
    for _, b := range data {
        if b != 0 {
            return false
        }
    }
    return true
}

// bytesToUintLittleEndian converts the slice to 64-bit unsigned integer.
func bytesToUintLittleEndian(b []byte) (res uint64) {
    mul := uint64(1)
    for i := 0; i < len(b); i++ {
        res += uint64(b[i]) * mul
        mul *= 256
    }
    return res
}

// BytesToUintBigEndian converts the slice to 64-bit unsigned integer.
func BytesToUintBigEndian(b []byte) (res uint64) {
    for i := 0; i < len(b); i++ {
        res *= 256
        res += uint64(b[i])
    }
    return res
}

// GenerateRandomID generates a random string, which is then returned to be used as a key id
func GenerateRandomID() (id string, err error) {
    buf, err := generateSecureRandomData(keyIDSize)
    if err != nil {
        return "", err
    }
    if !validateDataIntegrity(buf, keyIDSize) {
        return "", fmt.Errorf("error in generateRandomID: crypto/rand failed to generate random data")
    }
    id = common.Bytes2Hex(buf)
    return id, err
}

func isFullNode(bloom []byte) bool {
    if bloom == nil {
        return true
    }
    for _, b := range bloom {
        if b != 255 {
            return false
        }
    }
    return true
}

func BloomFilterMatch(filter, sample []byte) bool {
    if filter == nil {
        return true
    }

    for i := 0; i < BloomFilterSize; i++ {
        f := filter[i]
        s := sample[i]
        if (f | s) != f {
            return false
        }
    }

    return true
}

func addBloom(a, b []byte) []byte {
    c := make([]byte, BloomFilterSize)
    for i := 0; i < BloomFilterSize; i++ {
        c[i] = a[i] | b[i]
    }
    return c
}