snapshot of https://github.com/centrifugal/centrifugo.git (master, 2026-09-16; blobs > 131072B omitted)

internal/client/track_signature.go

@@ -0,0 +1,117 @@
+package client
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"hash"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+const gracePeriodSeconds = 5
+
+func parseSignatureTimestamps(sig string) (iat int64, expiry int64) {
+	first := strings.IndexByte(sig, ':')
+	if first < 0 {
+		return 0, 0
+	}
+	rest := sig[first+1:]
+	second := strings.IndexByte(rest, ':')
+	if second < 0 {
+		return 0, 0
+	}
+	iatVal, err := strconv.ParseInt(sig[:first], 10, 64)
+	if err != nil {
+		return 0, 0
+	}
+	expiryVal, err := strconv.ParseInt(rest[:second], 10, 64)
+	if err != nil {
+		return 0, 0
+	}
+	return iatVal, expiryVal
+}
+
+// trackSignatureVerifier reuses HMAC hashers and buffers for signature verification.
+// Thread-safe via sync.Pool.
+type trackSignatureVerifier struct {
+	macPool sync.Pool
+	bufPool sync.Pool
+}
+
+type verifyBufs struct {
+	payload     []byte
+	hexBuf      []byte
+	expectedHex []byte
+}
+
+func newTrackSignatureVerifier(secret string) *trackSignatureVerifier {
+	return &trackSignatureVerifier{
+		macPool: sync.Pool{
+			New: func() any {
+				return hmac.New(sha256.New, []byte(secret))
+			},
+		},
+		bufPool: sync.Pool{
+			New: func() any {
+				return &verifyBufs{
+					payload:     make([]byte, 0, 256),
+					hexBuf:      make([]byte, hex.EncodedLen(sha256.Size)),
+					expectedHex: make([]byte, hex.EncodedLen(sha256.Size)),
+				}
+			},
+		},
+	}
+}
+
+func verifyTrackSignature(secret string, channel string, sig string, keys []string, userID string) bool {
+	return newTrackSignatureVerifier(secret).verify(channel, sig, keys, userID)
+}
+
+func (v *trackSignatureVerifier) verify(channel string, sig string, keys []string, userID string) bool {
+	first := strings.IndexByte(sig, ':')
+	if first < 0 {
+		return false
+	}
+	rest := sig[first+1:]
+	second := strings.IndexByte(rest, ':')
+	if second < 0 {
+		return false
+	}
+	iatStr := sig[:first]
+	expiryStr := rest[:second]
+	hmacHex := rest[second+1:]
+
+	keysHash := sha256.Sum256([]byte(strings.Join(keys, "\x00")))
+
+	mac := v.macPool.Get().(hash.Hash)
+	bufs := v.bufPool.Get().(*verifyBufs)
+
+	// Payload fields are NUL-separated rather than ':'-separated so colons
+	// inside userID or channel (e.g. "news:tech", "alice:org") can't shift
+	// between fields and yield a colliding HMAC for a different (userID,
+	// channel) tuple. The outer signature string itself stays ':'-separated
+	// because its fields (iat / exp / hmac_hex) are colon-free by construction.
+	mac.Reset()
+	bufs.payload = bufs.payload[:0]
+	bufs.payload = append(bufs.payload, iatStr...)
+	bufs.payload = append(bufs.payload, 0)
+	bufs.payload = append(bufs.payload, expiryStr...)
+	bufs.payload = append(bufs.payload, 0)
+	bufs.payload = append(bufs.payload, userID...)
+	bufs.payload = append(bufs.payload, 0)
+	bufs.payload = append(bufs.payload, channel...)
+	bufs.payload = append(bufs.payload, 0)
+	hex.Encode(bufs.hexBuf, keysHash[:])
+	bufs.payload = append(bufs.payload, bufs.hexBuf...)
+	mac.Write(bufs.payload)
+	hex.Encode(bufs.expectedHex, mac.Sum(nil))
+
+	result := hmac.Equal([]byte(hmacHex), bufs.expectedHex)
+
+	v.macPool.Put(mac)
+	v.bufPool.Put(bufs)
+
+	return result
+}