Require privilege for VNC server and approval config changes

client/server/vnc_gate.go

@@ -0,0 +1,58 @@
+package server
+
+import (
+	"context"
+
+	"github.com/netbirdio/netbird/client/internal/ipcauth"
+	"github.com/netbirdio/netbird/client/internal/profilemanager"
+)
+
+// The VNC half of the privilege gate described in ssh_gate.go. The daemon runs
+// as root/LocalSystem and the VNC server it hosts attaches to the console
+// session, so both of these cross the user-to-root boundary:
+//
+//   - Enabling the VNC server publishes the console desktop, keyboard and
+//     mouse to whoever the account authorizes. On a multi-user host that
+//     desktop belongs to another user, and the profile the caller owns is not a
+//     privilege they hold over it.
+//   - Disabling the approval prompt removes the console user's per-connection
+//     consent, turning an authorized VNC session into a silent one.
+func requirePrivilegeForVNCChange(ctx context.Context, stored *profilemanager.Config, change privilegedConfigChange) error {
+	if enables(storedFlag(stored, func(c *profilemanager.Config) *bool { return c.DisableVNCApproval }), change.disableVNCApproval) {
+		return denyPrivileged(ctx, "disabling VNC connection approval", ipcauth.UpCommand("--disable-vnc-approval"))
+	}
+
+	if enables(storedFlag(stored, func(c *profilemanager.Config) *bool { return c.ServerVNCAllowed }), change.serverVNCAllowed) {
+		return denyPrivileged(ctx, "enabling the NetBird VNC server", ipcauth.UpCommand("--allow-server-vnc"))
+	}
+
+	return nil
+}
+
+// vncServerEnabled reports whether the profile currently runs the VNC server.
+//
+// Unlike the SSH server, VNC defaults to off: the flag was introduced with the
+// server itself, so a nil value is a config written before VNC existed and
+// means the server is not running.
+func vncServerEnabled(cfg *profilemanager.Config) bool {
+	if cfg == nil || cfg.ServerVNCAllowed == nil {
+		return false
+	}
+	return *cfg.ServerVNCAllowed
+}
+
+// enabledRemoteAccessServer names a remote-access server the profile currently
+// runs, and whether it runs any. It decides whether the management-binding and
+// deregistration guards apply, since either server hands authorization
+// decisions to the management identity the profile points at. SSH is reported
+// first when both are on: it is the more privileged of the two.
+func enabledRemoteAccessServer(cfg *profilemanager.Config) (string, bool) {
+	switch {
+	case sshServerEnabled(cfg):
+		return "SSH", true
+	case vncServerEnabled(cfg):
+		return "VNC", true
+	default:
+		return "", false
+	}
+}