TUHS

tuhs@tuhs.org

48 participants
6504 discussions

by Warner Losh

Greetings, I was wondering if there were any early versions of MERT available? Reading different sources, it appears that MERT was a real time kernel that used EMT traps to implement unix system calls (from around V4 or V5 given the timelines) on top of a real time executive (though some sources seem to imply it was a derivative of V4, most disagree). I see this in our archives https://wiki.tuhs.org/doku.php?id=misc:snippets:mert1 which is quite handy for discover its (and other early) unix lineages for a talk I'm doing in about a month. Now that we have sources, I go back and double check the recollections of things like this to see if version numbers were right, etc. But I can't do that with MERT at all. I can find the Bell Systems Technical Journal for Unix that has a brief article on it, but no sources to double check. So I thought I'd ask here if we have any MERT artifacts I can look at that have escaped my casual browsing of the archive. So far I've just found an email from Kevin Bowling on the topic from last month with no replies. And a similar thread from 2002, plus pleading from time to time (I can't tell if Warren or Noel wants it more :). I guess the same could be said for CB-UNIX and UNIX/TS, though I see a USDL/CB_Unix directory in the archive I could look at :). Warner

5 years, 9 months

Re: [TUHS] Set-uid shell scripts

by Dave Horsfall

On Tue, 6 Aug 2019, Lyndon Nerenberg wrote: >> Just to extend this thread a bit more, when did the set[ug]id bit start >> getting turned off if the file was overwritten? > > I'm pretty sure that's been the case since the dawn of time. Hmmm... I have this vague memory of V5 (which I only used for a couple of months before we got V6) not clearing that bit, but after all these years my memory is starting to fail me :-( > It was certainly the case in every System V (release 0 and beyond) I > worked with, along with many BSDs derivatives (SunOS 3+, Ultrix, etc). > (And Xenix, which had it's own insanity that I now think selinux is > trying to inflict on me.) I've always thought that Xenix was insane to start with... Then again, my first experience with it was on a 286... Now, when porting Unify, should I use large memory model here or small memory model? Crazy. > This has been documented in chown(2) for as long as I can remember, so > that's a good place to start if you want to dig back through the various > source trees. I don't have access to the sources right now, but I'll take your word for it; it was just a passing thought. -- Dave

5 years, 9 months

Running Research Unix v3 on simh

by Benito Buchheim

Hello everyone, My name is Benito Buchheim and I am a computer science student at Hasso-Plattner-Institute in Germany. During our Operating Systems Course we came across The Unix Heritage Society, more specifically Research Unix Version 3, and took a look into the source code of this version. The idea arose to try to get this running somehow as a sort of voluntary task. So I started digging my way through the available material and quickly found the "modified_nsys" version by Warren Toomey, which conveniently contained a very detailed readme file on how to compile and run this version on a Unix v5 emulator. Thus, I started cloning the simh Github Repository and built the pdp11 emulator. After downloading the v5root disk image and figuring out how to use simh to run it, I had a working Unix v5, but struggled a bit to copy more than one file onto it using the emulated devices. In the end, I used a very Hacky way and wrote a short python script which just runs the emulator and "copy pastes" the folder structure into the image. I now thought to be ready to start working my way through Toomey's readme. Unfortunately already the first command failed quite miserably. I changed my working directory and ran the first shell script to compile the kernel, but cc spat out loads of error messages which are not very detailed. As this is a very early version of c code I am kinda stuck at this point and running a bit out of ideas on what may have gone wrong. As there is this mailing list we thought to have a chat with the experts. Maybe there is somebody who could help or give a hint on how to get this running on the pdp11 emulator. I attached my shell script output and the v5 image containing the v3 source code in the /sys/nsys directory. It can be downloaded here: https://www.mission-eins.de/runningv3.zip Thanks a lot and best wishes from a small suburb near Berlin, Benito Buchheim

5 years, 9 months

Re: [TUHS] Who's behind the UNIX filesystem permission

by jnc＠mercury.lcs.mit.edu

> 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

5 years, 9 months

An Excellent Unix YouTube Video

by Warren Toomey

https://www.youtube.com/watch?v=g3jOJfrOknA National Inventors Hall of Fame - NIHF Published on Feb 18, 2019 Bell Labs colleagues Ken Thompson and Dennis Ritchie developed UNIX, a multi-tasking, multi-user operating system alternative to the batch processing systems then dominating the computer industry. Not sure why I hadn't seen this before :) Cheers, Warren

5 years, 9 months

Re: [TUHS] Set-uid shell scripts

by jnc＠mercury.lcs.mit.edu

> From: Dave Horsfall > Well, it's in the Subject: line :-) That was my _assumption_, but you know the old line about assumptions. Noel

5 years, 9 months

Re: [TUHS] Set-uid shell scripts

by jnc＠mercury.lcs.mit.edu

> From: Alec Muffett >>> ln -s /bin/scriptname ./-i >>> "-i" # assuming that "." is already in your path 'scriptname' (above) would have to be a shell script which was SETUID root? That was part of what I was missing, along with the below. > The cited filename is passed as argv[1] I wonder why it passed the link name, instead of the actual filename of the target (script)? Perhaps to allow one script to have multiple functions, depending on the name it was called with? But that could have been done with hard links? (Adding a hard link must require write access, because the link count in the inode has to be updated? So it would be equally secure as not having an SUID program with write access.) Part of the problem is having the kernel involved in starting shell scripts; convenient in some ways, but V6 etc worked fine without that 'feature'. Noel

5 years, 9 months

Re: [TUHS] Set-uid shell scripts

by Norman Wilson

Noel Chiappa: I wonder why it passed the link name, instead of the actual filename of the target (script)? Perhaps to allow one script to have multiple functions, depending on the name it was called with? ==== In fact the latter is still used here and there in standard system distributions. But from a security viewpoint it doesn't matter. For ln -s /bin/scriptname ./-i substitute execl("/bin/scriptname", "-i", (char *)0); If you can execute a program, you can fake its arguments, including argv[0]. There is no defence. Norman Wilson Toronto ON

5 years, 9 months

Re: [TUHS] Set-uid shell scripts

by jnc＠mercury.lcs.mit.edu

> From: Alec Muffett > until someone realised that you could do: > ln -s /bin/scriptname ./-i > "-i" # assuming that "." is already in your path > ...and get a root shell. I'm clearly not very awake this morning, because I don't understand how this works. Can you break it down a little? Thanks! Noel

5 years, 9 months

Set-uid shell scripts

by Dave Horsfall

Is it just me, or did someone actually implement set-uid scripts? I've proposed some silly things over the decades (my favourite is stty() working on things other than terminals, and guess what, we got ioctl() etc) but I have a vague recollection of this... The trouble is, I've worked with dozens of Unix-based vendors over the years (some good, some not so much) and so I've lost track of all the stupidity that I've seen. ObAnecdote: Just about every Unix vendor went belly-up shortly after I left them (under various circumstances), because the waste-of-space middle managers simply did not appreciate the importance of having a Unix guru on board if you're in the game of selling Unix boxen. I'd happily name them, but I think the principals are still alive :-) -- Dave

5 years, 9 months

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TUHS