Thread View: alt.folklore.computers
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Started by mo... Keith Moore
Thu, 21 Dec 1989 06:25
Revenge of the Sigma, or Fun with Paranoid Sysadmins
Author: mo... Keith Moore
Date: Thu, 21 Dec 1989 06:25
Date: Thu, 21 Dec 1989 06:25
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Just before I started school there back in 1978, Tennessee Tech University replaced its aging Xerox Sigma 7 computer with a brand new (but already-obsolete) Burroughs 6700. (Sigh) Unlike the Xerox CP-V operating system which was full of holes, the Burroughs MCP (Master Control Program) was said to be very secure. The new machine had no assembler or debugger with which to explore, and Burroughs systems were popular in banks and other environments where security was important. So the computer center administration was happy that it could relax a bit in the war against the students. The "beast" (as we called it) had a large front panel facing the machine room window so users could watch the lights blink. The most noticable feature on the front panel was a rectangular grid of 192 lights. You could tell at a glance how heavily loaded the machine was, since the MCP's idle process would put a "B" (the Burroughs logo) in the lights whenever it was running. Imagine if you will a computer center director walking by the machine room a few months after the machine had been installed. Casually he looks through the window to see how the machine is doing, only to realize that the front panel lights now form the pattern of a SIGMA. As it turns out, all you had to do to accomplish this was to keep the right bit patterns on the top of the stack (the B6700 was a stack machine) -- this basically involved sitting in a tight loop doing a bitwise compare of two double-precision values over and over. So the system's security had not really been compromised (yet), but this was little comfort to one sysadmin who was convinced that the front panel lights were controlled by "the innermost part of the operating system"... No, I can't claim credit for this hack -- but I knew the people who worked on it and I did see the program run. One of them eventually went on to collaborate in the CMU "coke" effort after leaving TTU. Keith Moore Internet: mo...@cs.utk.edu University of Tenn. CS Dept. BITNET: moore@utkvx 107 Ayres Hall, UT Campus UT Decnet: utkcs::moore Knoxville Tennessee 37996-1301 Telephone: +1 615 974 0822
Re: Revenge of the Sigma, or Fun with Paranoid Sysadmins
Author: Paul Campbell
Date: Thu, 21 Dec 1989 17:56
Date: Thu, 21 Dec 1989 17:56
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In article <15...@utkcs2.cs.utk.edu> mo...@cs.utk.edu (Keith Moore) writes: >(but already-obsolete) Burroughs 6700. (Sigh) this was one of the great machines of its time ... (I, of course, am biased) >room window so users could watch the lights blink. The most noticable >feature on the front panel was a rectangular grid of 192 lights. >You could tell at a glance how heavily loaded the machine was, since >the MCP's idle process would put a "B" (the Burroughs logo) in the >lights whenever it was running. and therein lies another story ... because we all started out telling the operators that when they saw the 'B' the machine was lightly loaded so they would stuff more work in. The problem was that when the machine got overloaded and started to thrash its little guts out it would go into disk wait as it shuffled data in/out of core, the 'B' would come on while it waited for disk and the operators would stuff more work in - such positive feedback was bad news .... We solved it by changing the macro that put the 'B' up (MCP was shipped to sites in source form - card images (not actual cards) - you compiled it and installed it when you brought up a new version of the OS (it didn't always compile first time of the tape without syntax errors!) - anyway back to the story - we change the code that put the 'B' up to but up 3 faces, a smiley face :-) when the machine is dead empty, an open mouth :-() when the machine is lightly loaded and a frown when it was thrashing :-( (they were vertical smileys) this stopped the operators from over stuffing the machine .... maybe we were an early user of icons .... Paul -- Paul Campbell UUCP: ..!mtxinu!taniwha!paul AppleLink: CAMPBELL.P "We got a thousand points of light for the homeless man, Got a kinder, gentler, machine gun hand ..." - Neil Young 'Freedom'
Re: Revenge of the Sigma, or Fun with Paranoid Sysadmins
Author: Mark ROBERTS
Date: Sat, 23 Dec 1989 00:28
Date: Sat, 23 Dec 1989 00:28
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In article <15...@utkcs2.cs.utk.edu> mo...@cs.utk.edu (Keith Moore) writes: >Unlike the Xerox CP-V operating system which was full of holes, >the Burroughs MCP (Master Control Program) was said to be very secure. I spent many happy hours hacking on languages for Burroughs Medium Systems (B2500,B3500,B4500 and descendants) whose OS was also called MCP. But that one at least had a very interesting security hole. Its been over 15 years so its a little fuzzy, but the basic idea was that when you wrote a message to the system console the message and/or the display code was copied or run in priviledged mode. So we would put code in the message instead of text; the code was just enough to put our own program in priviledged mode when it returned from the display call. (Paul, Grace or ?, do you remember better?) Never did any real evil with this hook, in fact wrote a very nifty profiling tool that was used quite a bit. (These were quite pleasant machines - ask me about decimal core dumps some time.) Mark Roberts uunet!microsof!markro
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