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feat: improve security #106

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feat: improve security #106

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252235f
feat(room): enforce new counter is old counter + 1
jackssrt Sep 12, 2026
0f0dfa8
feat(room): disconnect probably cheating clients
jackssrt Sep 12, 2026
fbfd79e
fix(room): allow 0 as the first packet counter
jackssrt Sep 12, 2026
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12 changes: 9 additions & 3 deletions server/room.go
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Original file line number Diff line number Diff line change
Expand Up @@ -86,9 +86,13 @@ func joinRoomWs(conn *websocket.Conn, r *http.Request) {
}

client := &RoomClient{
conn: conn,
outbox: make(chan []byte, 256),
key: serverSecurity.NewClientKey(),
conn: conn,
outbox: make(chan []byte, 256),
key: serverSecurity.NewClientKey(),
// 2^32-1, the biggest number uint32 can hold
// will overflow to 0 when incremented to check the counter (cnt + 1)
// allowing 0 to be the first packet counter
counter: 4294967295,
}

if session, ok := clients.LoadOK(pd.Uuid); ok {
Expand Down Expand Up @@ -224,10 +228,12 @@ func (c *RoomClient) processMsgs(msg []byte) (errs []error) {
}

if !serverSecurity.VerifySignature(c.key, msg) {
c.disconnect()
return append(errs, errors.New("bad signature"))
}

if !serverSecurity.VerifyCounter(&c.counter, msg) {
c.disconnect()
return append(errs, errors.New("bad counter"))
}

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2 changes: 1 addition & 1 deletion server/security/security.go
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,7 @@ func (s *Security) VerifySignature(clientKey uint32, msg []byte) bool {
}

func (s *Security) VerifyCounter(counter *uint32, msg []byte) bool {
if cnt := binary.BigEndian.Uint32(msg[4:]); *counter < cnt {
if cnt := binary.BigEndian.Uint32(msg[4:]); *counter == cnt+1 {
*counter = cnt
return true
}
Expand Down