Unix v4 (1973) – Live Terminal

(unixv4.dev)

130 points | by pjmlp 8 hours ago

14 comments

  • mmastrac 5 hours ago
    If whoever wrote this wants to add an authentic (and somewhat period correct) terminal front-end, I wrote a VT420 hardware emulator that works in the browser and we can wire them together!

    https://mmastrac.github.io/blaze/

    (the API is undocumented but stupidly simple: an async js_read() function and a sync js_write() function)

    • dboreham 4 hours ago
      You'll want VT-52 for this era.
      • fl7305 1 hour ago
        More like the VT-05. The VT-52 came a few years later. But yeah, the VT-420 is way later.

        Fun fact: The VT-52 didn't have a loudspeaker for the bell sound. Instead, it had a electromechanical relay which was set up to self-oscillate.

        "Typing a character produced a noise by activating a relay. The relay was also used as a buzzer to sound the bell character, producing a sound that "has been compared to the sound of a '52 Chevy stripping its gears."

  • Deeg9rie9usi 7 hours ago
    Reading the source unearths interesting things: https://sigma-star.at/blog/2025/12/unix-v4-buffer-overflow/
    • mmooss 4 hours ago
      > the knowledge that a buffer overflow could be exploited for arbitrary code execution had not yet come of age.

      Meaning, people hadn't figured that out, or it wasn't a commonplace technique? They must have seen buffer overflows crash running software; it doesn't take much imagination to think about the next steps.

      • em500 3 hours ago
        This is Unix V4 from 1973. The total number of installations world wide was around 20, all inside Bell Labs. There was no networking support at all, so security was mostly physical, i.e., office building security (though you could dial in with a modem). Multi-user support was a bunch of serial-line terminals. Pretty much everyone knew everyone else who was on the system.
      • leoc 1 hour ago
        I'm not an expert, but a quick look at https://en.wikipedia.org/wiki/Buffer_overflow#History suggests that some people, at least, had figured it out by 1972 https://apps.dtic.mil/sti/citations/AD0772806 :

        > By supplying addresses outside of the space allocated to the users program, it is often possible to get the monitor to obtain unauthorized data for that user, or at the very least, generate a set of conditions in the monitor that causes a system crash.

        > In one contemporary operating system, one of the functions provided is to move limited amounts of information between system and user space. The code performing this function does not check the source and destination addresses properly, permitting portions of the monitor to be overlaid by the user. This can be used to inject code into the monitor that will permit the user to seize control of the machine.

        (Volume 1 is at https://apps.dtic.mil/sti/citations/AD0758206 .) However general awareness of the security implications seems to have been very limited before the Morris worm, and then even for several years after that. Even in late 1996 an article which in its own words "attempt[ed] to explain what buffer overflows are, and how their exploits work" could still be published in Phrack magazine, and in fact even be quite a milestone https://en.wikipedia.org/wiki/Buffer_overflow#History .

      • dboreham 3 hours ago
        Most computers did not exist in an adversarial environment at the time.

        Perhaps the most "adversarial" context would be: undergraduate timeshare use. So the mainframes of the day, which would be the typical platform for undergrad programming (if timeshare was even offered to undergrads in 1973) might be expected to be somewhat hardened to attacks of various kinds since undergrads trying to hack their grade higher, get more CPU time, etc, was a known thing.

        But Unix machines, and minicomputers in general, were not used for undergrad purposes. They were only available to be used by PhD candidates and other higher order beings. Those dudes had the root password anyway, so no need to harden the machine against their potential attacks. There was no networking to speak of, so no malicious traffic to worry about. The first worm didn't appear until the late 1980s.

        So if you had talked to a Unix sysadmin in 1973 (all...1 of them) they probably would understand the general concept of someone running a program that crapped onto kernel memory with the result they could have root privileges, but there would have been no plausible adversary around with any reason to mount that attack. Plus every cycle and every byte counted, so there would have been many more fish to fry before worrying about buffer overflow problems.

        • II2II 3 hours ago
          > since undergrads trying to hack their grade higher

          Would student records even be stored on an unix system at the time? I am under the impression that Unix was very much a research operating system in the 1970's (either the subject of or a tool for). Administrative functions were more likely to be conducted with an IBM mainframe. (At least that is how it was when I arrived at university a couple of decades later, which I always took to be a legacy thing.)

      • doublerabbit 3 hours ago
        My Educated guess, both.

        Malicious attempts at exploiting would require physical access.

        This was 1970's running on a PDP hardware. These were not normally connected to the internet so the attack vector of attacking would be have literal.

        Any bugs would probably been of been fixed prior to and isn't this the first alpha of unix? So probably patched later in versions.

    • mananaysiempre 6 hours ago
      I kept expecting an exploit :) Something to poke at on a slow evening, I guess, though with the buffer in static memory it might be difficult.
      • Deeg9rie9usi 6 hours ago
        Exploiting this is close to trivial because the adjacent buffer contains the pw entry. So, you can control what the input is compared with. That way the password check can be bypassed without injecting code.
        • mananaysiempre 5 hours ago
          Good point, thanks! The crypt() of the input, not the input itself, but guessing at the (PDP-11 assembly :/ ) code for crypt() a bit, it looks like it stops after 64 characters if it can’t find a null terminator before that, so

            0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef012345678901234567890123456789012345root:p3Y0ydAx:
          
          should work as an exploit, and indeed it does. (Arbitrary 64-character password, then 36 bytes to pad to the end of the 100-byte buffer, then the part of root’s /etc/passwd entry for said password until at least the second colon.)
  • Aperocky 5 hours ago
    I wonder how hard is it to do the entire thing in browser/js. It seems hugged to death right now due to backend connections.
    • PunchyHamster 4 hours ago
      people ran linux and win 95 in browser, would be fine
  • xorvoid 3 hours ago
    I'm amused at how circular this is. Unix v4 is first OS written in C, now running on top of an unbelievable amount of C (and C++). Classic circular computer science delight.
  • publicdebates 7 hours ago

        Session Error
        Rate limit exceeded: 10 per 1 minute
    • hnthrowaway0315 7 hours ago
      I managed to get in after a few tries. But then I got a timeout. I think I'm going to wait until the HN deathhug is over :D
  • omoikane 3 hours ago
    I am glad it already has `ed`, the standard text editor.

    But it's lacking some features available in newer versions of ed, such as using 'n' to print line numbers.

  • dim13 6 hours ago
    Glad to have played with it a bit before it got Slashdotted. ;)
  • ramon156 7 hours ago
    Rate limited! a new record!
    • yunnpp 6 hours ago
      I'm going to guess we're on the same VPN.
  • enricotr 7 hours ago
    Almost slashdotted.
  • TZubiri 6 hours ago
    Getting a rate limit error, but I haven't used the program.
  • timzaman 4 hours ago
    death by hn..
  • colesantiago 8 hours ago
    Just a heads up:

    > By using this service, you acknowledge that terminal sessions may be logged for educational and debugging purposes. No personal data is collected beyond your IP address.

    Is this all open source and is the code available? So that we know where the data is truly going?

    Hard to trust it if it isn't fully OSS.

    This is a cool demo though.

    • altairprime 7 hours ago
      > Hard to trust it

      Clarification requested: How is ‘trust’ applicable to this site?

      • skulk 1 hour ago
        I don't want them to see my blunders in the chess game I lost against the 40 year old computer program.
    • mmooss 4 hours ago
      It would be an excellent phishing attack if your target is senior IT. You filter out every non-geek, of course, and certainly your responses would lean heavily toward an older crowd. They's all see 'Unix v4', be too excited to consider the risks, and being a 1973 OS assume it is innocent and safe (not thinking about the platform delivering it).

      Maybe you'd get too many retirees ...

      Now you just need

    • voidfunc 7 hours ago
      Even if it was open source how do you know its not a fork?
      • lo_zamoyski 7 hours ago
        And even more to the point: this is a website. What is he afraid of this website doing that all the other websites don't already do? Why single this one out?
        • qarl 7 hours ago
          WARNING: YOU ARE ABOUT TO OPEN A WEBPAGE.
          • derrida 6 hours ago
            Exception: -1 Page already opened. Time can only flow forward.
    • StableAlkyne 7 hours ago
      > Hard to trust it if it isn't fully OSS

      It's an emulated PDP-11, could you elaborate on the threat model here?

      I get that companies are being gross about logging everything online, but come on. It's okay to have fun.

      Who in their right mind is using this for anything other than curiosity's sake?

      • utopiah 7 hours ago
        Little bit of banking on an emulator on a random website, why not?
        • cocodill 7 hours ago
          bitcoin will not be mined on its own.
    • znpy 6 hours ago
      Yeah it’s unlikely that this site will collect any meaningful data and it’s unlikely that you lose any meaningful data by playing with a virtual unix from the 70ies.

      You aren’t getting downvoted enough.

  • charcircuit 7 hours ago
    Did they get a license from Novell for this or is this as illegal as many of the other emulator sites with copyrighted software on them? Considering the page doesn't mention it, I'm leaning towards it being copyright infringement.
    • LukeShu 7 hours ago
      In 2002, Caldera licensed Research Unix <= 7th edition and 32-bit 32V Unix under a BSD-style license.

      Gotta stick the "This product includes software developed or owned by Caldera International, Inc." notice on it though.

      • charcircuit 6 hours ago
        This copy of Unix v4 came from AT&T and not one of the freely licensed ones Caldera released. Caldera may own the rights now for this unearthed copy, but I am not aware that they have provided licenses for this new release.
        • spijdar 6 hours ago
          If your argument is that Caldera might not actually have the rights to UNIX in the first place to grant the license, that's fair.

          But the license they provided (http://www.lemis.com/grog/UNIX/ancient-source-all.pdf) explicitly names versions 1, 2, 3, 4, 5, 6, and 7 of UNIX for the 16-bit PDP-11. Yes, these versions originated at AT&T (Bell Labs) but are distinct legally from SysIII and SysV UNIX, also from AT&T, which are explicitly not covered by the Caldera license.

          • charcircuit 6 hours ago
            Thank you for finding this.

            >Redistributions of source code and documentation must retain the above copyright notice

            The archived tape doesn't have this, which contradicts the license. This makes me think the license may only be referring to a set of source code that they released with this license text already applied as opposed to what was recently archived.

            >Redistributions in binary form must reproduce the above copyright notice

            I don't see the copyright notice on that page. So at the very least that may need to be added.

            • dekhn 3 hours ago
              Why do you care about this so much?
              • charcircuit 3 hours ago
                Because I think the history of rights ownership and licensing is interesting.
                • qarl 2 hours ago
                  You might also enjoy arguing.
    • fortyseven 7 hours ago
      Personal financial stake in this, or do you regularly police the use of ancient software?
      • charcircuit 6 hours ago
        >Personal financial stake in this

        In the sense that the company I work for would be financially harmed if copyright infringement of software was freely allowed. I benefit from the ability of people being able to sell rights to use software.

        It's one thing to digitize and archive ancient software, it's another thing to allow people to freely use it without acquiring the proper license for it.

        • II2II 5 hours ago
          The people who preserve vintage software typically respect boundaries in order to avoid cases where the copyright holder would be financially harmed. It is not a perfect guarantee, but it is a reasonable one.

          Hardline stances usually cause more harm than good anyhow. I remember collecting Apple II gear in the late 1990's and early 2000's. The people saying that any form of copyright infringement was bad were either ignored or flamed since a lot of people just looked at their collection of software from the late 1970's and early 1980's and said, "we're at risk of losing this if we don't make it available, and the copyright holders won't lose anything if we do make it available." Which wasn't strictly true since there were some software developers who created software in the early 1990's who were still selling it. Unfortunately their absolutist attitude did not earn them many allies, so it became a lost cause.

        • kube-system 4 hours ago
          I’m normally one defending copyright on this forum. But dude, this software is half a century old. Nobody is buying or selling this software. Nobody’s business or livelihood is threatened by this.
          • charcircuit 3 hours ago
            >Nobody is buying or selling this software. Nobody’s business or livelihood is threatened by this.

            Because the media was no longer in the rights holder's possession. This is a dangerous line of reasoning where someone can steal a copyrighted work and then be allowed to profit off of it because the artist has no way to do so.

            Being able to see a long lost UNIX version is interesting and I could imagine it being worth paying to see it or play with it similar to how people pay money to see things at a museum.

            • kube-system 2 hours ago
              Dangerous line of reasoning??? Allowing time for an author to monetize a work is the legal rationale for copyright protection. There is no commercial value to this software.
              • charcircuit 1 hour ago
                Here is a hypothetical. You see someone on their iPad making a nice drawing. You then steal the iPad and then start making prints of that art and start selling them. To me the artist should be able to disallow such prints from being sold.

                But your line of reasoning says that since the artist is unable to make money from the print, then there is nothing wrong with someone else doing so as the artist isn't missing out on any profit since they have no way to sell prints.

        • LastTrain 5 hours ago
          I mean if you are assigning points I’d actually say the former is worse than the latter.
    • publicdebates 6 hours ago
      What do you think about GOG?
      • charcircuit 6 hours ago
        It's good to have competition against Steam.
      • yunnpp 6 hours ago
        GOG is perfectly legal.