[Info-vax] disabling a CTRL/Y ast

[VAXman- at SendSpamHere.ORG]

In article <fd6d6c6a-1c7d-432d-ac2b-1244dfa0fbb6 at googlegroups.com>, Tom Adams <tadamsmar at gmail.com> writes:
>On Thursday, January 7, 2016 at 11:21:27 AM UTC-5, VAXman- wrote:
>> In article <3a583568-e33e-446e-9805-6ea94f9ebf71 at googlegroups.com>, Tom Adams <tadamsmar at gmail.com> writes:
>> >On Wednesday, January 6, 2016 at 12:22:06 PM UTC-5, Stephen Hoffman wrote:
>> >> On 2016-01-06 16:46:32 +0000, Tom Adams said:
>> >> 
>> >> > I want to turn ctrl/y into a noop in certain regions of code and turn 
>> >> > ctrl/y into an exit in other regions of code.
>> >> 
>> >> Some background: I've posted more than a few replies here in the 
>> >> comp.os.vms newsgroup, specifically discussing the particular 
>> >> application in question and its general design, and an unfortunate 
>> >> aggregation of the UI and the more critical code paths, and your 
>> >> understandable preference to avoid restructuring the application code 
>> >> through reworking the existing design to block ^Y from arriving within 
>> >> the most critical sections of the code.
>> >> 
>> >> > I do find that it is necessary to run lib$disable_ctrl at the beginning 
>> >> > of the program and lib$enable_ctrl at the end of the program to restore 
>> >> > the previous CLI state, but I need to run asts to do the rest.
>> >> 
>> >> If you want ASTs in some parts of the code and not in others, then 
>> >> you're going to have to wrap those sections appropriately.   That's if 
>> >> you don't decide to migrate those critical code sections into another 
>> >> process context, or related steps.  Because beyond the potential for ^Y 
>> >> in these sections and the associated issues you're having with the 
>> >> image rundown processing in the absence of an EXIT command, other sorts 
>> >> of generic application failures ("bugs") or any arriving $forcex calls 
>> >> or such activities can potentially still leave the application in an 
>> >> indeterminate state.
>> >> 
>> >> 
>> >> 
>> >> -- 
>> >> Pure Personal Opinion | HoffmanLabs LLC
>> >
>> >Here's an example of what I am trying to do that seems to work OK.
>> >I guess a forced exit from a bug could leave the CTRL\Y in
>> >the disabled state at the CLI instead of the original state.
>> >
>> >Also, it's possible that someone could define TT to be some terminal
>> >other than the login terminal.  VMS leaves all the built-in process
>> >logicals that refer to the login terminal vulnerable to redefinition.
>> >It may be possible to roll your own safe (executive, no_alias) logical
>> >name via a call in syslogin.
>> >
>> >Also, I still need to cover the cases where this code runs in a context
>> >where TT is not defined.
>> 
>> 	PROGRAM MY_TERMINAL
>> 	IMPLICIT NONE
>> 
>> 	INCLUDE '($DSCDEF)'
>> 	INCLUDE '($JPIDEF)'
>> 	INCLUDE '(LIB$ROUTINES)'
>> 
>> 	INTEGER*4 STATUS
>> 
>> 	RECORD	/DSCDEF1/ TERMINAL
>> 
>> 	TERMINAL.DSC$W_MAXSTRLEN = 0
>> 	TERMINAL.DSC$B_DTYPE = DSC$K_DTYPE_T
>> 	TERMINAL.DSC$B_CLASS = DSC$K_CLASS_D
>> 	TERMINAL.DSC$A_POINTER = 0
>> 
>> 	STATUS = LIB$GETJPI(JPI$_TERMINAL,,,,TERMINAL,)
>> 	IF (STATUS.AND.1) THEN
>> 	  STATUS = LIB$PUT_OUTPUT(TERMINAL)
>> 	ENDIF
>> 
>> 	CALL SYS$EXIT(%VAL(STATUS))
>> 	END
>> 
>> -- 
>> VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG
>> 
>> I speak to machines with the voice of humanity.
>
>That's better than TT.
>
>But that is also vulnerable to a non-priv user. For instance
>if the login terminal is RTA1:  the a non-priv user can define RTA1
>thusly:
>
>DEFINE RTA1 LTA180:
>
>Where lta180: is a valid device name.  Calls like SYS$ASSIGN will dutifully
>translate RTA1: to LTA180: assign it a channel, and return a
>normal status.
>
>Admittedly, it's not very likely that a non-priv user would do that.

Unless your nonprivied user as discovered a way to write PCB[PCB$T_TERMINAL],
I doubt you'll have much to worry about. ;)

-- 
VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG

I speak to machines with the voice of humanity.