200(0) Ancient UNIX Licenses

200(0) Ancient UNIX Licenses

[norman]

Here's Brian Kernighan's note on troff and Y2K:

in n1.c, numtab[YR] is set to localtime()->tm_year, which is the
number of years since 1900.  in 2000, this will contain 100.
the troff manual says that \n(yr contains "the last two digits of
the current year", but nowhere in the code is this set, and the
year can be set to anything.  so it's really "the current year
minus 1900".  the manual and the code are 
inconsistent, which is always a problem. 

in any case, in most installations troff and nroff are legacy
systems for which there is no source code, so changing them is
not feasible.  furthermore, any change to troff is likely to
require changes in macro packages anyway, and may cause silent
errors by conflicting with current behavior or colliding with
previously unused names.

fortunately, it seems straightforward to fix the macro packages
that are the most likely sources of problem; individual macro
packages will have to be fixed by individuals.  grepping for
"yr" will find most trouble spots.

typical macros packages use \n(yr in two ways.  one is

	ds ]W (printed \n(mo/\n(dy/\n(yr)

which assumes that the year is 2 digits and to be printed as 2
digits.  presumably the first day of 2000 is to be printed as
1/1/00, so the fix here is to set register yr to 2 digits

	.nr yr \n(yr%100

either once at the beginning (under the assumption that the year
isn't changed by the macro package) or each time \n(yr is going
to be used (providing locality at the price of more changes).

the other common usage is

	.ds ]W \*(]m \n(dy, 19\n(yr

the easiest way to fix this is to add, at the beginning again,

	.nr yr 1900+\n(yr

and change all subsequent uses from 19\n(yr to \n(yr.

any macro package that uses both of these constructions will need
a bit more care to unify things; the easiest fix is likely to be
two registers, one with the full year and one with the last two
digits.

	.nr YR 1900+\n(yr	\" 4-digit year
	.nr yr \n(yr%100	\" last two digits

this will break code that happened to use this register name.

some macro packages (e.g., -mm) try to be clever about dates,
and include explicit tests to determine whether a user-provided
date has 2 or 4 digits, and then adjust by 1900; this is another
case that has to be fiddled by hand.

any approach that changes register yr at the beginning fails if
the year is set explicitly later on, as it might be by some of
the date macros in -ms and -mm.  this still seems like the best
fix, however.


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From: norman@nose.cita.utoronto.ca
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Subject: Re: 200(0) Ancient UNIX Ulcers
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Michael Sokolov grumbled:

  > Warren's note reminds me of a few other Y2K bugs I've spotted that affect
  > ancient UNIX:
    ^^^^^^^

  Would you please avoid that term? It is offensive to those for whom Kernighan/
  Ritchie/Thompson/Berkeley UNIX is the primary and sole computing platform.
  Thank you.

If the shoe doesn't fit, feel free not to wear it.  I certainly didn't have
`Kernighan/Ritchie/Thompson/Berkeley UNIX' in mind; I rarely do, as I am
much more interested in ancient systems.

Chuckling all the way to the rest home,

Norman Wilson

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From: Greg Lehey <grog@lemis.com>
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Subject: Re: 200(0) Ancient UNIX Licenses
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On Tuesday,  4 January 2000 at  7:08:51 -0500, norman at nose.cita.utoronto.ca wrote:
> Warren's note reminds me of a few other Y2K bugs I've spotted that affect
> ancient UNIX:
> - date: no way to set the date past 1999 unless in the present year,
> because two-digit input.

I didn't have any problem with 2.11BSD.  I just supplied 00 for the
year.  Which release were you using?

Greg
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Greg wrote:
>On Tuesday,  4 January 2000 at  7:08:51 -0500, norman at nose.cita.utoronto.ca wrote:
>> Warren's note reminds me of a few other Y2K bugs I've spotted that affect
>> ancient UNIX:
>> - date: no way to set the date past 1999 unless in the present year,
>> because two-digit input.
>I didn't have any problem with 2.11BSD.  I just supplied 00 for the
>year.  Which release were you using?

That's because I did the fix for 2.11BSD back when I was Y2K-ing all
my PDP-11 sources a few years ago, and Steven incorporated it into the
distribution.  The fix was quick and dirty, but works fine because
Unix effectively has an expiration date of 2038 when the signed 32-bit time
word goes negative, so it's easy enough to window the centuries.

This brings up a question: should fixes (and I mean fundamental fixes
like Y2K ones) be incorporated back into the boot images in the archive, or
should they be left in their "pristine" state?  (Yes, i know, some of
those boot images aren't quite so pristine.)

As long as we're on the topic, which versions of Unix had the C
compiler recognize when it was recompiling the kernel and put a back
door in for the developers?  And of course the C compiler recognized
when it was recompiling itself and made sure that the this recognition
code was also inserted.  As I understand it, the distributed sources
never had this security hole in them, only the binaries, but of course
the binaries self-perpetuated the security hole even if you recompiled them.

-- 
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> This brings up a question: should fixes (and I mean fundamental fixes
> like Y2K ones) be incorporated back into the boot images in the archive, or
> should they be left in their "pristine" state?  (Yes, i know, some of
> those boot images aren't quite so pristine.)

Ideally, both.  Perhaps boot images with these fixes should be available,
yes, but so should the originals.


> As long as we're on the topic, which versions of Unix had the C
> compiler recognize when it was recompiling the kernel and put a back
> door in for the developers?

Good question!  I don't know, but it was actually the login command...