waku/common/filter.go
// Copyright 2019 The Waku Library Authors.
//
// The Waku 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 Waku library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty off
// 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 Waku library. If not, see <http://www.gnu.org/licenses/>.
//
// This software uses the go-ethereum library, which is licensed
// under the GNU Lesser General Public Library, version 3 or any later.
package common
import (
"crypto/ecdsa"
"fmt"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
)
// Filter represents a Waku message filter
type Filter struct {
Src *ecdsa.PublicKey // Sender of the message
KeyAsym *ecdsa.PrivateKey // Private Key of recipient
KeySym []byte // Key associated with the Topic
Topics [][]byte // Topics to filter messages with
PoW float64 // Proof of work as described in the Waku spec
AllowP2P bool // Indicates whether this filter is interested in direct peer-to-peer messages
SymKeyHash common.Hash // The Keccak256Hash of the symmetric key, needed for optimization
id string // unique identifier
Messages MessageStore
}
// Filters represents a collection of filters
type Filters struct {
watchers map[string]*Filter
topicMatcher map[TopicType]map[*Filter]struct{} // map a topic to the filters that are interested in being notified when a message matches that topic
allTopicsMatcher map[*Filter]struct{} // list all the filters that will be notified of a new message, no matter what its topic is
mutex sync.RWMutex
}
// NewFilters returns a newly created filter collection
func NewFilters() *Filters {
return &Filters{
watchers: make(map[string]*Filter),
topicMatcher: make(map[TopicType]map[*Filter]struct{}),
allTopicsMatcher: make(map[*Filter]struct{}),
}
}
// Install will add a new filter to the filter collection
func (fs *Filters) Install(watcher *Filter) (string, error) {
if watcher.KeySym != nil && watcher.KeyAsym != nil {
return "", fmt.Errorf("filters must choose between symmetric and asymmetric keys")
}
id, err := GenerateRandomID()
if err != nil {
return "", err
}
fs.mutex.Lock()
defer fs.mutex.Unlock()
if fs.watchers[id] != nil {
return "", fmt.Errorf("failed to generate unique ID")
}
if watcher.expectsSymmetricEncryption() {
watcher.SymKeyHash = crypto.Keccak256Hash(watcher.KeySym)
}
watcher.id = id
fs.watchers[id] = watcher
fs.addTopicMatcher(watcher)
return id, err
}
// Uninstall will remove a filter whose id has been specified from
// the filter collection
func (fs *Filters) Uninstall(id string) bool {
fs.mutex.Lock()
defer fs.mutex.Unlock()
if fs.watchers[id] != nil {
fs.removeFromTopicMatchers(fs.watchers[id])
delete(fs.watchers, id)
return true
}
return false
}
func (fs *Filters) AllTopics() []TopicType {
var topics []TopicType
fs.mutex.Lock()
defer fs.mutex.Unlock()
for t := range fs.topicMatcher {
topics = append(topics, t)
}
return topics
}
// addTopicMatcher adds a filter to the topic matchers.
// If the filter's Topics array is empty, it will be tried on every topic.
// Otherwise, it will be tried on the topics specified.
func (fs *Filters) addTopicMatcher(watcher *Filter) {
if len(watcher.Topics) == 0 {
fs.allTopicsMatcher[watcher] = struct{}{}
} else {
for _, t := range watcher.Topics {
topic := BytesToTopic(t)
if fs.topicMatcher[topic] == nil {
fs.topicMatcher[topic] = make(map[*Filter]struct{})
}
fs.topicMatcher[topic][watcher] = struct{}{}
}
}
}
// removeFromTopicMatchers removes a filter from the topic matchers
func (fs *Filters) removeFromTopicMatchers(watcher *Filter) {
delete(fs.allTopicsMatcher, watcher)
for _, topic := range watcher.Topics {
delete(fs.topicMatcher[BytesToTopic(topic)], watcher)
}
}
// GetWatchersByTopic returns a slice containing the filters that
// match a specific topic
func (fs *Filters) GetWatchersByTopic(topic TopicType) []*Filter {
res := make([]*Filter, 0, len(fs.allTopicsMatcher))
for watcher := range fs.allTopicsMatcher {
res = append(res, watcher)
}
for watcher := range fs.topicMatcher[topic] {
res = append(res, watcher)
}
return res
}
// Get returns a filter from the collection with a specific ID
func (fs *Filters) Get(id string) *Filter {
fs.mutex.RLock()
defer fs.mutex.RUnlock()
return fs.watchers[id]
}
func (fs *Filters) All() []*Filter {
fs.mutex.RLock()
defer fs.mutex.RUnlock()
var filters []*Filter
for _, f := range fs.watchers {
filters = append(filters, f)
}
return filters
}
// NotifyWatchers notifies any filter that has declared interest
// for the envelope's topic.
func (fs *Filters) NotifyWatchers(env *Envelope, p2pMessage bool) bool {
var msg *ReceivedMessage
fs.mutex.RLock()
defer fs.mutex.RUnlock()
var matched bool
candidates := fs.GetWatchersByTopic(env.Topic)
for _, watcher := range candidates {
if p2pMessage && !watcher.AllowP2P {
log.Trace(fmt.Sprintf("msg [%x], filter [%s]: p2p messages are not allowed", env.Hash(), watcher.id))
continue
}
var match bool
if msg != nil {
match = watcher.MatchMessage(msg)
} else {
match = watcher.MatchEnvelope(env)
if match {
msg = env.Open(watcher)
if msg == nil {
log.Trace("processing message: failed to open", "message", env.Hash().Hex(), "filter", watcher.id)
}
} else {
log.Trace("processing message: does not match", "message", env.Hash().Hex(), "filter", watcher.id)
}
}
if match && msg != nil {
msg.P2P = p2pMessage
log.Trace("processing message: decrypted", "hash", env.Hash().Hex())
if watcher.Src == nil || IsPubKeyEqual(msg.Src, watcher.Src) {
watcher.Trigger(msg)
}
matched = true
}
}
return matched
}
func (f *Filter) expectsAsymmetricEncryption() bool {
return f.KeyAsym != nil
}
func (f *Filter) expectsSymmetricEncryption() bool {
return f.KeySym != nil
}
// Trigger adds a yet-unknown message to the filter's list of
// received messages.
func (f *Filter) Trigger(msg *ReceivedMessage) {
err := f.Messages.Add(msg)
if err != nil {
log.Error("failed to add msg into the filters store", "hash", msg.EnvelopeHash, "error", err)
}
}
// Retrieve will return the list of all received messages associated
// to a filter.
func (f *Filter) Retrieve() []*ReceivedMessage {
msgs, err := f.Messages.Pop()
if err != nil {
log.Error("failed to retrieve messages from filter store", "error", err)
return nil
}
return msgs
}
// MatchMessage checks if the filter matches an already decrypted
// message (i.e. a Message that has already been handled by
// MatchEnvelope when checked by a previous filter).
// Topics are not checked here, since this is done by topic matchers.
func (f *Filter) MatchMessage(msg *ReceivedMessage) bool {
if f.PoW > 0 && msg.PoW < f.PoW {
return false
}
if f.expectsAsymmetricEncryption() && msg.isAsymmetricEncryption() {
return IsPubKeyEqual(&f.KeyAsym.PublicKey, msg.Dst)
} else if f.expectsSymmetricEncryption() && msg.isSymmetricEncryption() {
return f.SymKeyHash == msg.SymKeyHash
}
return false
}
// MatchEnvelope checks if it's worth decrypting the message. If
// it returns `true`, client code is expected to attempt decrypting
// the message and subsequently call MatchMessage.
// Topics are not checked here, since this is done by topic matchers.
func (f *Filter) MatchEnvelope(envelope *Envelope) bool {
return f.PoW <= 0 || envelope.pow >= f.PoW
}