fix: harden engine across casino, economy, concurrency, security, and content

1 files changed, 78 insertions, 0 deletions

diff --git a/internal/net/server.go b/internal/net/server.go
index 9d99acc..05a98d1 100644
--- a/internal/net/server.go
+++ b/internal/net/server.go
@@ -168,6 +168,14 @@ type Server struct {
 	// stopping flips when Shutdown begins so listener goroutines treat
 	// their subsequent Accept/serve errors as expected, not fatal.
 	stopping atomic.Bool
+	// conns counts live sessions across every transport. handleSession
+	// admits against maxConnections so a pre-auth connection flood cannot
+	// hold an unbounded number of reader goroutines, buffers, and outboxes.
+	conns atomic.Int64
+	// idleTimeout returns the read timeout armed before each message. It is a
+	// field so tests can drive the idle-drop path without waiting out the
+	// production windows; nil means sessionIdleTimeout.
+	idleTimeout func(*Session) time.Duration
 }
 
 type Hub struct {
@@ -187,6 +195,64 @@ const (
 	closeFlushTimeout = 2 * time.Second
 )
 
+// Connection admission and idle-read limits. The listener admits at most
+// maxConnections live sessions; each read arms an idle deadline (short before
+// authentication, generous once the session has an account) that every
+// message resets, so a silent client cannot pin a reader goroutine forever
+// while legitimate long sessions keep working.
+const (
+	maxConnections   = 1000
+	loginReadTimeout = 2 * time.Minute
+	idleReadTimeout  = 30 * time.Minute
+)
+
+// admitConnection reserves a connection slot, returning false when the server
+// is at capacity. Every admitted connection must call releaseConnection.
+func (s *Server) admitConnection() bool {
+	if s.conns.Add(1) > maxConnections {
+		s.conns.Add(-1)
+		return false
+	}
+	return true
+}
+
+func (s *Server) releaseConnection() {
+	s.conns.Add(-1)
+}
+
+// sessionIdleTimeout returns the read timeout to arm for this session.
+func (s *Server) sessionIdleTimeout(sess *Session) time.Duration {
+	if s.idleTimeout != nil {
+		return s.idleTimeout(sess)
+	}
+	return sessionIdleTimeout(sess)
+}
+
+// sessionIdleTimeout returns the read timeout for a session: the account-name
+// and password prompts get a short window (pre-auth sockets are the ones an
+// anonymous flood targets), everything else gets a generous idle timeout.
+func sessionIdleTimeout(sess *Session) time.Duration {
+	switch sess.State() {
+	case StateAccountName, StatePassword:
+		return loginReadTimeout
+	default:
+		return idleReadTimeout
+	}
+}
+
+// armReadDeadline sets an idle read deadline on the session's transport when
+// it supports one. tcpConn and wsConn (both in this package) expose their
+// underlying connection, so telnet, telnet-TLS, and websocket are all covered.
+func armReadDeadline(sess *Session, d time.Duration) {
+	deadline := time.Now().Add(d)
+	switch c := sess.Conn.(type) {
+	case *tcpConn:
+		_ = c.conn.SetReadDeadline(deadline)
+	case *wsConn:
+		_ = c.conn.SetReadDeadline(deadline)
+	}
+}
+
 // StartWriter puts the session into queued mode: writes are enqueued and a
 // dedicated goroutine drains the queue to the network with per-message write
 // deadlines. The goroutine exits after Close() — draining whatever was
@@ -705,12 +771,24 @@ func (s *Server) handleSession(sess *Session, handler func(*Session, string)) {
 		sess.Close()
 	}()
 
+	// Admit before reading anything: an over-capacity connection (including
+	// one arriving through the websocket transport, whose handler shares this
+	// path) is told so and dropped without holding a read loop.
+	if !s.admitConnection() {
+		sess.Write("Server is at full capacity. Please try again later.\r\n")
+		return
+	}
+	defer s.releaseConnection()
+
 	sess.Write("\033[2J\033[H")
 
 	sess.Write(WelcomeBanner())
 	sess.Write("What's your account name? ")
 
 	for {
+		// Re-armed every iteration so any message from the client resets the
+		// idle countdown.
+		armReadDeadline(sess, s.sessionIdleTimeout(sess))
 		line, err := sess.Conn.ReadMessage()
 		if err != nil {
 			log.Printf("session read error: %v", err)