whisper: topics replaced by bloom filters

cmd/wnode/main.go

@@ -22,6 +22,7 @@ package main
 import (
 	"bufio"
 	"crypto/ecdsa"
+	crand "crypto/rand"
 	"crypto/sha512"
 	"encoding/binary"
 	"encoding/hex"
@@ -48,6 +49,7 @@ import (
 )
 
 const quitCommand = "~Q"
+const entropySize = 32
 
 // singletons
 var (
@@ -55,6 +57,7 @@ var (
 	shh        *whisper.Whisper
 	done       chan struct{}
 	mailServer mailserver.WMailServer
+	entropy    [entropySize]byte
 
 	input = bufio.NewReader(os.Stdin)
 )
@@ -274,6 +277,11 @@ func initialize() {
 			TrustedNodes:   peers,
 		},
 	}
+
+	_, err = crand.Read(entropy[:])
+	if err != nil {
+		utils.Fatalf("crypto/rand failed: %s", err)
+	}
 }
 
 func startServer() {
@@ -614,10 +622,10 @@ func writeMessageToFile(dir string, msg *whisper.ReceivedMessage) {
 }
 
 func requestExpiredMessagesLoop() {
-	var key, peerID []byte
+	var key, peerID, bloom []byte
 	var timeLow, timeUpp uint32
 	var t string
-	var xt, empty whisper.TopicType
+	var xt whisper.TopicType
 
 	keyID, err := shh.AddSymKeyFromPassword(msPassword)
 	if err != nil {
@@ -640,18 +648,19 @@ func requestExpiredMessagesLoop() {
 				utils.Fatalf("Failed to parse the topic: %s", err)
 			}
 			xt = whisper.BytesToTopic(x)
+			bloom = whisper.TopicToBloom(xt)
+			obfuscateBloom(bloom)
+		} else {
+			bloom = whisper.MakeFullNodeBloom()
 		}
 		if timeUpp == 0 {
 			timeUpp = 0xFFFFFFFF
 		}
 
-		data := make([]byte, 8+whisper.TopicLength)
+		data := make([]byte, 8, 8+whisper.BloomFilterSize)
 		binary.BigEndian.PutUint32(data, timeLow)
 		binary.BigEndian.PutUint32(data[4:], timeUpp)
-		copy(data[8:], xt[:])
-		if xt == empty {
-			data = data[:8]
-		}
+		data = append(data, bloom...)
 
 		var params whisper.MessageParams
 		params.PoW = *argServerPoW
@@ -685,3 +694,20 @@ func extractIDFromEnode(s string) []byte {
 	}
 	return n.ID[:]
 }
+
+// obfuscateBloom adds 16 random bits to the the bloom
+// filter, in order to obfuscate the containing topics.
+// it does so deterministically within every session.
+// despite additional bits, it will match on average
+// 32000 times less messages than full node's bloom filter.
+func obfuscateBloom(bloom []byte) {
+	const half = entropySize / 2
+	for i := 0; i < half; i++ {
+		x := int(entropy[i])
+		if entropy[half+i] < 128 {
+			x += 256
+		}
+
+		bloom[x/8] = 1 << uint(x%8) // set the bit number X
+	}
+}

whisper/mailserver/mailserver.go

@@ -107,17 +107,16 @@ func (s *WMailServer) DeliverMail(peer *whisper.Peer, request *whisper.Envelope)
 		return
 	}
 
-	ok, lower, upper, topic := s.validateRequest(peer.ID(), request)
+	ok, lower, upper, bloom := s.validateRequest(peer.ID(), request)
 	if ok {
-		s.processRequest(peer, lower, upper, topic)
+		s.processRequest(peer, lower, upper, bloom)
 	}
 }
 
-func (s *WMailServer) processRequest(peer *whisper.Peer, lower, upper uint32, topic whisper.TopicType) []*whisper.Envelope {
+func (s *WMailServer) processRequest(peer *whisper.Peer, lower, upper uint32, bloom []byte) []*whisper.Envelope {
 	ret := make([]*whisper.Envelope, 0)
 	var err error
 	var zero common.Hash
-	var empty whisper.TopicType
 	kl := NewDbKey(lower, zero)
 	ku := NewDbKey(upper, zero)
 	i := s.db.NewIterator(&util.Range{Start: kl.raw, Limit: ku.raw}, nil)
@@ -130,7 +129,7 @@ func (s *WMailServer) processRequest(peer *whisper.Peer, lower, upper uint32, to
 			log.Error(fmt.Sprintf("RLP decoding failed: %s", err))
 		}
 
-		if topic == empty || envelope.Topic == topic {
+		if whisper.BloomFilterMatch(bloom, envelope.Bloom()) {
 			if peer == nil {
 				// used for test purposes
 				ret = append(ret, &envelope)
@@ -152,22 +151,16 @@ func (s *WMailServer) processRequest(peer *whisper.Peer, lower, upper uint32, to
 	return ret
 }
 
-func (s *WMailServer) validateRequest(peerID []byte, request *whisper.Envelope) (bool, uint32, uint32, whisper.TopicType) {
-	var topic whisper.TopicType
+func (s *WMailServer) validateRequest(peerID []byte, request *whisper.Envelope) (bool, uint32, uint32, []byte) {
 	if s.pow > 0.0 && request.PoW() < s.pow {
-		return false, 0, 0, topic
+		return false, 0, 0, nil
 	}
 
 	f := whisper.Filter{KeySym: s.key}
 	decrypted := request.Open(&f)
 	if decrypted == nil {
 		log.Warn(fmt.Sprintf("Failed to decrypt p2p request"))
-		return false, 0, 0, topic
-	}
-
-	if len(decrypted.Payload) < 8 {
-		log.Warn(fmt.Sprintf("Undersized p2p request"))
-		return false, 0, 0, topic
+		return false, 0, 0, nil
 	}
 
 	src := crypto.FromECDSAPub(decrypted.Src)
@@ -179,15 +172,24 @@ func (s *WMailServer) validateRequest(peerID []byte, request *whisper.Envelope)
 	// if !bytes.Equal(peerID, src) {
 	if src == nil {
 		log.Warn(fmt.Sprintf("Wrong signature of p2p request"))
-		return false, 0, 0, topic
+		return false, 0, 0, nil
 	}
 
-	lower := binary.BigEndian.Uint32(decrypted.Payload[:4])
-	upper := binary.BigEndian.Uint32(decrypted.Payload[4:8])
-
-	if len(decrypted.Payload) >= 8+whisper.TopicLength {
-		topic = whisper.BytesToTopic(decrypted.Payload[8:])
+	var bloom []byte
+	payloadSize := len(decrypted.Payload)
+	if payloadSize < 8 {
+		log.Warn(fmt.Sprintf("Undersized p2p request"))
+		return false, 0, 0, nil
+	} else if payloadSize == 8 {
+		bloom = whisper.MakeFullNodeBloom()
+	} else if payloadSize < 8+whisper.BloomFilterSize {
+		log.Warn(fmt.Sprintf("Undersized bloom filter in p2p request"))
+		return false, 0, 0, nil
+	} else {
+		bloom = decrypted.Payload[8 : 8+whisper.BloomFilterSize]
 	}
 
-	return true, lower, upper, topic
+	lower := binary.BigEndian.Uint32(decrypted.Payload[:4])
+	upper := binary.BigEndian.Uint32(decrypted.Payload[4:8])
+	return true, lower, upper, bloom
 }

whisper/mailserver/server_test.go

@@ -17,6 +17,7 @@
 package mailserver
 
 import (
+	"bytes"
 	"crypto/ecdsa"
 	"encoding/binary"
 	"io/ioutil"
@@ -61,7 +62,7 @@ func generateEnvelope(t *testing.T) *whisper.Envelope {
 	h := crypto.Keccak256Hash([]byte("test sample data"))
 	params := &whisper.MessageParams{
 		KeySym:   h[:],
-		Topic:    whisper.TopicType{},
+		Topic:    whisper.TopicType{0x1F, 0x7E, 0xA1, 0x7F},
 		Payload:  []byte("test payload"),
 		PoW:      powRequirement,
 		WorkTime: 2,
@@ -121,6 +122,7 @@ func deliverTest(t *testing.T, server *WMailServer, env *whisper.Envelope) {
 		upp:   birth + 1,
 		key:   testPeerID,
 	}
+
 	singleRequest(t, server, env, p, true)
 
 	p.low, p.upp = birth+1, 0xffffffff
@@ -131,14 +133,14 @@ func deliverTest(t *testing.T, server *WMailServer, env *whisper.Envelope) {
 
 	p.low = birth - 1
 	p.upp = birth + 1
-	p.topic[0]++
+	p.topic[0] = 0xFF
 	singleRequest(t, server, env, p, false)
 }
 
 func singleRequest(t *testing.T, server *WMailServer, env *whisper.Envelope, p *ServerTestParams, expect bool) {
 	request := createRequest(t, p)
 	src := crypto.FromECDSAPub(&p.key.PublicKey)
-	ok, lower, upper, topic := server.validateRequest(src, request)
+	ok, lower, upper, bloom := server.validateRequest(src, request)
 	if !ok {
 		t.Fatalf("request validation failed, seed: %d.", seed)
 	}
@@ -148,12 +150,13 @@ func singleRequest(t *testing.T, server *WMailServer, env *whisper.Envelope, p *
 	if upper != p.upp {
 		t.Fatalf("request validation failed (upper bound), seed: %d.", seed)
 	}
-	if topic != p.topic {
+	expectedBloom := whisper.TopicToBloom(p.topic)
+	if !bytes.Equal(bloom, expectedBloom) {
 		t.Fatalf("request validation failed (topic), seed: %d.", seed)
 	}
 
 	var exist bool
-	mail := server.processRequest(nil, p.low, p.upp, p.topic)
+	mail := server.processRequest(nil, p.low, p.upp, bloom)
 	for _, msg := range mail {
 		if msg.Hash() == env.Hash() {
 			exist = true
@@ -166,7 +169,7 @@ func singleRequest(t *testing.T, server *WMailServer, env *whisper.Envelope, p *
 	}
 
 	src[0]++
-	ok, lower, upper, topic = server.validateRequest(src, request)
+	ok, lower, upper, bloom = server.validateRequest(src, request)
 	if !ok {
 		// request should be valid regardless of signature
 		t.Fatalf("request validation false negative, seed: %d (lower: %d, upper: %d).", seed, lower, upper)
@@ -174,10 +177,11 @@ func singleRequest(t *testing.T, server *WMailServer, env *whisper.Envelope, p *
 }
 
 func createRequest(t *testing.T, p *ServerTestParams) *whisper.Envelope {
-	data := make([]byte, 8+whisper.TopicLength)
+	bloom := whisper.TopicToBloom(p.topic)
+	data := make([]byte, 8)
 	binary.BigEndian.PutUint32(data, p.low)
 	binary.BigEndian.PutUint32(data[4:], p.upp)
-	copy(data[8:], p.topic[:])
+	data = append(data, bloom...)
 
 	key, err := shh.GetSymKey(keyID)
 	if err != nil {

whisper/whisperv6/doc.go

@@ -60,7 +60,7 @@ const (
 	aesKeyLength    = 32 // in bytes
 	aesNonceLength  = 12 // in bytes; for more info please see cipher.gcmStandardNonceSize & aesgcm.NonceSize()
 	keyIDSize       = 32 // in bytes
-	bloomFilterSize = 64 // in bytes
+	BloomFilterSize = 64 // in bytes
 	flagsLength     = 1
 
 	EnvelopeHeaderLength = 20

whisper/whisperv6/envelope.go

@@ -249,7 +249,7 @@ func (e *Envelope) Bloom() []byte {
 
 // TopicToBloom converts the topic (4 bytes) to the bloom filter (64 bytes)
 func TopicToBloom(topic TopicType) []byte {
-	b := make([]byte, bloomFilterSize)
+	b := make([]byte, BloomFilterSize)
 	var index [3]int
 	for j := 0; j < 3; j++ {
 		index[j] = int(topic[j])

whisper/whisperv6/peer.go

@@ -56,7 +56,7 @@ func newPeer(host *Whisper, remote *p2p.Peer, rw p2p.MsgReadWriter) *Peer {
 		powRequirement: 0.0,
 		known:          set.New(),
 		quit:           make(chan struct{}),
-		bloomFilter:    makeFullNodeBloom(),
+		bloomFilter:    MakeFullNodeBloom(),
 		fullNode:       true,
 	}
 }
@@ -120,7 +120,7 @@ func (peer *Peer) handshake() error {
 		err = s.Decode(&bloom)
 		if err == nil {
 			sz := len(bloom)
-			if sz != bloomFilterSize && sz != 0 {
+			if sz != BloomFilterSize && sz != 0 {
 				return fmt.Errorf("peer [%x] sent bad status message: wrong bloom filter size %d", peer.ID(), sz)
 			}
 			peer.setBloomFilter(bloom)
@@ -229,7 +229,7 @@ func (peer *Peer) notifyAboutBloomFilterChange(bloom []byte) error {
 func (peer *Peer) bloomMatch(env *Envelope) bool {
 	peer.bloomMu.Lock()
 	defer peer.bloomMu.Unlock()
-	return peer.fullNode || bloomFilterMatch(peer.bloomFilter, env.Bloom())
+	return peer.fullNode || BloomFilterMatch(peer.bloomFilter, env.Bloom())
 }
 
 func (peer *Peer) setBloomFilter(bloom []byte) {
@@ -238,13 +238,13 @@ func (peer *Peer) setBloomFilter(bloom []byte) {
 	peer.bloomFilter = bloom
 	peer.fullNode = isFullNode(bloom)
 	if peer.fullNode && peer.bloomFilter == nil {
-		peer.bloomFilter = makeFullNodeBloom()
+		peer.bloomFilter = MakeFullNodeBloom()
 	}
 }
 
-func makeFullNodeBloom() []byte {
-	bloom := make([]byte, bloomFilterSize)
-	for i := 0; i < bloomFilterSize; i++ {
+func MakeFullNodeBloom() []byte {
+	bloom := make([]byte, BloomFilterSize)
+	for i := 0; i < BloomFilterSize; i++ {
 		bloom[i] = 0xFF
 	}
 	return bloom

whisper/whisperv6/peer_test.go

@@ -152,7 +152,7 @@ func resetParams(t *testing.T) {
 }
 
 func initBloom(t *testing.T) {
-	masterBloomFilter = make([]byte, bloomFilterSize)
+	masterBloomFilter = make([]byte, BloomFilterSize)
 	_, err := mrand.Read(masterBloomFilter)
 	if err != nil {
 		t.Fatalf("rand failed: %s.", err)
@@ -164,7 +164,7 @@ func initBloom(t *testing.T) {
 		masterBloomFilter[i] = 0xFF
 	}
 
-	if !bloomFilterMatch(masterBloomFilter, msgBloom) {
+	if !BloomFilterMatch(masterBloomFilter, msgBloom) {
 		t.Fatalf("bloom mismatch on initBloom.")
 	}
 }
@@ -178,7 +178,7 @@ func initialize(t *testing.T) {
 
 	for i := 0; i < NumNodes; i++ {
 		var node TestNode
-		b := make([]byte, bloomFilterSize)
+		b := make([]byte, BloomFilterSize)
 		copy(b, masterBloomFilter)
 		node.shh = New(&DefaultConfig)
 		node.shh.SetMinimumPoW(masterPow)

whisper/whisperv6/whisper.go

@@ -232,11 +232,11 @@ func (whisper *Whisper) SetMaxMessageSize(size uint32) error {
 
 // SetBloomFilter sets the new bloom filter
 func (whisper *Whisper) SetBloomFilter(bloom []byte) error {
-	if len(bloom) != bloomFilterSize {
+	if len(bloom) != BloomFilterSize {
 		return fmt.Errorf("invalid bloom filter size: %d", len(bloom))
 	}
 
-	b := make([]byte, bloomFilterSize)
+	b := make([]byte, BloomFilterSize)
 	copy(b, bloom)
 
 	whisper.settings.Store(bloomFilterIdx, b)
@@ -558,14 +558,14 @@ func (whisper *Whisper) Subscribe(f *Filter) (string, error) {
 // updateBloomFilter recalculates the new value of bloom filter,
 // and informs the peers if necessary.
 func (whisper *Whisper) updateBloomFilter(f *Filter) {
-	aggregate := make([]byte, bloomFilterSize)
+	aggregate := make([]byte, BloomFilterSize)
 	for _, t := range f.Topics {
 		top := BytesToTopic(t)
 		b := TopicToBloom(top)
 		aggregate = addBloom(aggregate, b)
 	}
 
-	if !bloomFilterMatch(whisper.BloomFilter(), aggregate) {
+	if !BloomFilterMatch(whisper.BloomFilter(), aggregate) {
 		// existing bloom filter must be updated
 		aggregate = addBloom(whisper.BloomFilter(), aggregate)
 		whisper.SetBloomFilter(aggregate)
@@ -701,7 +701,7 @@ func (whisper *Whisper) runMessageLoop(p *Peer, rw p2p.MsgReadWriter) error {
 		case bloomFilterExCode:
 			var bloom []byte
 			err := packet.Decode(&bloom)
-			if err == nil && len(bloom) != bloomFilterSize {
+			if err == nil && len(bloom) != BloomFilterSize {
 				err = fmt.Errorf("wrong bloom filter size %d", len(bloom))
 			}
 
@@ -779,11 +779,11 @@ func (whisper *Whisper) add(envelope *Envelope, isP2P bool) (bool, error) {
 		}
 	}
 
-	if !bloomFilterMatch(whisper.BloomFilter(), envelope.Bloom()) {
+	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()) {
+		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)
 		}
@@ -1025,12 +1025,12 @@ func isFullNode(bloom []byte) bool {
 	return true
 }
 
-func bloomFilterMatch(filter, sample []byte) bool {
+func BloomFilterMatch(filter, sample []byte) bool {
 	if filter == nil {
 		return true
 	}
 
-	for i := 0; i < bloomFilterSize; i++ {
+	for i := 0; i < BloomFilterSize; i++ {
 		f := filter[i]
 		s := sample[i]
 		if (f | s) != f {
@@ -1042,8 +1042,8 @@ func bloomFilterMatch(filter, sample []byte) bool {
 }
 
 func addBloom(a, b []byte) []byte {
-	c := make([]byte, bloomFilterSize)
-	for i := 0; i < bloomFilterSize; i++ {
+	c := make([]byte, BloomFilterSize)
+	for i := 0; i < BloomFilterSize; i++ {
 		c[i] = a[i] | b[i]
 	}
 	return c

whisper/whisperv6/whisper_test.go

@@ -826,11 +826,11 @@ func TestSymmetricSendKeyMismatch(t *testing.T) {
 func TestBloom(t *testing.T) {
 	topic := TopicType{0, 0, 255, 6}
 	b := TopicToBloom(topic)
-	x := make([]byte, bloomFilterSize)
+	x := make([]byte, BloomFilterSize)
 	x[0] = byte(1)
 	x[32] = byte(1)
-	x[bloomFilterSize-1] = byte(128)
-	if !bloomFilterMatch(x, b) || !bloomFilterMatch(b, x) {
+	x[BloomFilterSize-1] = byte(128)
+	if !BloomFilterMatch(x, b) || !BloomFilterMatch(b, x) {
 		t.Fatalf("bloom filter does not match the mask")
 	}
 
@@ -842,11 +842,11 @@ func TestBloom(t *testing.T) {
 	if err != nil {
 		t.Fatalf("math rand error")
 	}
-	if !bloomFilterMatch(b, b) {
+	if !BloomFilterMatch(b, b) {
 		t.Fatalf("bloom filter does not match self")
 	}
 	x = addBloom(x, b)
-	if !bloomFilterMatch(x, b) {
+	if !BloomFilterMatch(x, b) {
 		t.Fatalf("bloom filter does not match combined bloom")
 	}
 	if !isFullNode(nil) {
@@ -856,16 +856,16 @@ func TestBloom(t *testing.T) {
 	if isFullNode(x) {
 		t.Fatalf("isFullNode false positive")
 	}
-	for i := 0; i < bloomFilterSize; i++ {
+	for i := 0; i < BloomFilterSize; i++ {
 		b[i] = byte(255)
 	}
 	if !isFullNode(b) {
 		t.Fatalf("isFullNode false negative")
 	}
-	if bloomFilterMatch(x, b) {
+	if BloomFilterMatch(x, b) {
 		t.Fatalf("bloomFilterMatch false positive")
 	}
-	if !bloomFilterMatch(b, x) {
+	if !BloomFilterMatch(b, x) {
 		t.Fatalf("bloomFilterMatch false negative")
 	}
 
@@ -879,7 +879,7 @@ func TestBloom(t *testing.T) {
 		t.Fatalf("failed to set bloom filter: %s", err)
 	}
 	f = w.BloomFilter()
-	if !bloomFilterMatch(f, x) || !bloomFilterMatch(x, f) {
+	if !BloomFilterMatch(f, x) || !BloomFilterMatch(x, f) {
 		t.Fatalf("retireved wrong bloom filter")
 	}
 }