[Info-vax] CLI editing, was: Re: VMS - Virtual Terminals - A security risk way back yonder OR was that an Old Wives Tale ?

[Johnny Billquist]

On 2016-02-13 23:28, David Froble wrote:
> Johnny Billquist wrote:

>> In a way I find this morbidly interesting. The terminal driver in RSX
>> is probably the largest and most insane can of worms there is. I would
>> have hoped that it was cleaned in up VMS, and made more sane. But by
>> your description, it sounds almost identical to the RSX code...
>>
>>     Johnny
>>
>
> To be a bit fair, there have been numerous methods for connecting
> terminals to VAX systems.  I omit mentioning Alpha and IA64 because by
> the time they came out most terminal access was LAT or TelNet or other
> network connections.
>
> RS232
> Current loop
> LAT
> TCP/IP
>
> and perhaps more.
>
> So yeah, it's understandable that terminal driver has been set up to
> handle lots of different connection methods.

If the VMS driver is anything near the RSX driver in complexity, then 
the backend part that drives the different types of interfaces is a 
rather small part of the code. In all honesty, that part only moves bits 
between places. That's the easy part. And it actually makes a difference 
if it is a DZ11, DH11, DHU11, DJ11, DL11, and so on. RS-232 or current 
loop is irrelevant. It looks the same from the computer. But every 
controller needs its own code.

But the big chunk of the terminal driver is all the different 
functionality it supports. Read, with and without echo, with special 
terminators, writes, breakthrough writes, terminal independent cursor 
positioning, read with timeout, read with default input, read with 
prompt, special terminal management mode, handling various terminal 
attributes, flow control, typeahead buffering with deferred echoing, 
turning off and on output, flushing of input and output, inserting fill 
characters, handling tabs, keep track of cursor positioning, full 
duplex, escape handling... The list just goes on and on...

> I'm going to guess that any serial lines still in use would not be for
> terminals, but other devices.  But what do I know?
>
> With VMS in a server mode, the existing stuff works for me.

Physical serial lines are probably much fewer nowadays, but any network 
session would pass through the same functionality as well...

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol