TIP 61: Make TK_NO_SECURITY Run-Time Switchable

Author:         Jeff Hobbs <[email protected]>
Author:         Donal K. Fellows <[email protected]>
State:          Deferred
Type:           Project
Vote:           Pending
Created:        12-Sep-2001
Tcl-Version:    8.5


This TIP changes the compile time Tk define TK_NO_SECURITY to be switchable at run-time.


The TK_NO_SECURITY compile time #define is available to disable some security checking when send is used. The direct comments in the Makefile are:

 # To turn off the security checks that disallow incoming sends when
 # the X server appears to be insecure, reverse the comments on the
 # following lines:

I propose to make this switch configurable at runtime through a tk securesend option.


Users would be able to debug between Tk applications on Unix using send without having to compile a special version of Tk or manipulating the security settings of their X server to Tk's liking (which can then conflict with other work). It is common for users in internal ("safe") networks to open up access to an X server with xhost +machine.


By allowing security to be disabled, users do possibly open up their system to attack. However, secure is the default setting, and any paranoid users can rename send {} to ensure that it is not used at all.

Reference Implementation

A full patch for this feature is available at:


The proposal adds one element to the private TkDisplay structure (configuration for secure send is done per display), and creates the Tcl level command:

	tk securesend ?-displayof window? ?boolean?

It leaves the TK_NO_SECURITY flag alone. If specified, send is insecure by default, otherwise it is secure.


DKF - It should be possible to control the setting of the compile-time TK_NO_SECURITY flag from the configure script; having to edit the Makefile by hand to adjust it makes it too easy to inadvertently break something by introducing an unfortunate typo. Being able to pass a --disable-security flag would make thing much easier from a user's point of view, and will make it less likely that the Tk maintainers will have to deal with bug reports that ultimately stem from a dumb mistake made in a sensitive spot...


This document has been placed in the public domain.