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* Re: [TUHS] Who's behind the UNIX filesystem permission
@ 2019-08-02 14:35 Noel Chiappa
  2019-08-02 15:01 ` Clem Cole
  2019-08-02 15:17 ` Arthur Krewat
  0 siblings, 2 replies; 16+ messages in thread
From: Noel Chiappa @ 2019-08-02 14:35 UTC (permalink / raw)
  To: tuhs; +Cc: jnc

    > From: Arthur Krewat

    > there's the setuid bit on directories - otherwise known as the sticky
    > bit.

Minor nit; in V6 at least (not sure about later), the 'sticky' bit was a
separate bit from SUID and SGID. (When set on a pure/split object file, it
told the OS to retain the text image on the swap device even when no active
process was using it. Hence the name...)

	Noel


^ permalink raw reply	[flat|nested] 16+ messages in thread
* Re: [TUHS] Who's behind the UNIX filesystem permission
@ 2019-08-01 23:43 Noel Chiappa
  2019-08-02  1:03 ` David Arnold
  2019-08-07  2:35 ` Dave Horsfall
  0 siblings, 2 replies; 16+ messages in thread
From: Noel Chiappa @ 2019-08-01 23:43 UTC (permalink / raw)
  To: tuhs; +Cc: jnc

    > From: Dave Horsfall

    > it actually *unlinked* directories

Maybe the application was written by a LISP programmer? :-)

(Not really, of course; it was probably just someone who didn't know much
about Unix. They had a list of system calls, and 'unlink' probably said ' only
works on directories when the caller is root', so...)

Speaking of LISP and GC, it's impressive how GC is not really a big issue any
more. At one point people were even building special CPUs that had hardware
support for GC; now it seems to be a 'solved problem' on ordinary CPUs.

	Noel

^ permalink raw reply	[flat|nested] 16+ messages in thread
* Re: [TUHS] Who's behind the UNIX filesystem permission
@ 2019-08-01 12:35 Doug McIlroy
  2019-08-01 16:22 ` John P. Linderman
                   ` (2 more replies)
  0 siblings, 3 replies; 16+ messages in thread
From: Doug McIlroy @ 2019-08-01 12:35 UTC (permalink / raw)
  To: tuhs

Read and write permission were common ideas--even part of
the Atlas paging hardware that was described before 1960.
The original concept of time-sharing was to give a virtual
computer to each user. When it became clear that sharing
was an equally important aspect, owner/other permissions
arose. I believe that was the case with Multics.

Owner/other permissions were in PDP-11 Unix from the start.
Group permissions arose from the ferment of daily talk in
the Unix lab. How might the usual protections be extended
to collaborative projects? Ken and Dennis deserve credit
for the final implementation. Yet clean as the idea of groups
was, it has been used only sporadically (in my experience).

Execute permission (much overloaded in Unix) also dates
back to the dawn of paging. One Unix innovation, due to
Dennis, was the suid bit--the only patented feature in
the Research system. It was instantly adopted for 
maintaining the Moo (a game now sold under the name
"Master Mind") league standings table.

One trouble with full-blown ACLs as required by NSA's
Orange Book, is obscurity. It is hard (possibly NP-
complete) to analyze the actual security of an ACL
configuration.

A common failing of Unix administration was a proliferation
of suid-root programs, e.g. mail(1). I recall one system
that had a hundred such programs. Sudo provided a way
station between suid and ACLs.

Doug

^ permalink raw reply	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2019-08-07  2:36 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-02 14:35 [TUHS] Who's behind the UNIX filesystem permission Noel Chiappa
2019-08-02 15:01 ` Clem Cole
2019-08-02 15:17 ` Arthur Krewat
2019-08-02 21:23   ` Dave Horsfall
2019-08-03 12:51     ` Nemo
  -- strict thread matches above, loose matches on Subject: below --
2019-08-01 23:43 Noel Chiappa
2019-08-02  1:03 ` David Arnold
2019-08-02  4:36   ` Rob Pike
2019-08-07  2:35 ` Dave Horsfall
2019-08-01 12:35 Doug McIlroy
2019-08-01 16:22 ` John P. Linderman
2019-08-01 16:35   ` Arthur Krewat
2019-08-01 17:01 ` Nemo Nusquam
2019-08-01 18:26   ` Arthur Krewat
2019-08-01 20:14     ` Lyndon Nerenberg
2019-08-01 21:23 ` Dave Horsfall

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