Author:         Jeff Hobbs <JeffH@ActiveState.com>
Author:         Donal K. Fellows <fellowsd@cs.man.ac.uk>
State:          Deferred
Type:           Project
Vote:           Pending
Created:        12-Sep-2001
Post-History:   
Tcl-Version:    8.5

Abstract

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

Rationale

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:
 SECURITY_FLAGS		=
 #SECURITY_FLAGS		= -DTK_NO_SECURITY

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

Benefits

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.

Drawbacks

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:

http://sf.net/tracker/?func=detail&aid=456732&group\_id=12997&atid=312997

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.

Comments

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...

Copyright

This document has been placed in the public domain.