No vulnerability known in SSH-1.2.26

[Robert Hettinga <rah@shipwright.com>]

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Date: Mon, 2 Nov 1998 10:33:29 +0200 (EET)
From: Tatu Ylonen <ylo@ssh.fi>
To: ssh@clinet.fi, ssh-bugs@clinet.fi, bugtraq@netspace.org,
        info@rootshell.com, coderpunks@toad.com
CC: "David A. Curry" <davy@ers.ibm.com>, cert@cert.org, auscert@auscert.org.au
Subject: No vulnerability known in SSH-1.2.26
Organization: SSH Communications Security, Finland
Sender: owner-coderpunks@toad.com
Precedence: bulk

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As the original author of SSH I want to comment on the rumored
vulnerabilities.

I have personally looked into the claimed vulnerabilities, including
the ones reported by IBM, and do not have any reason to assume that
there would be any vulnerability in ssh-1.2.26.  NO SUCH VULNERABILITY
IS KNOWN.

I repeat, I KNOW OF NO VULNERABILITY IN SSH-1.2.26.

The IBM-ERS report on ssh vulnerability turned out to be false alert.
They could not reproduce it after they recompiled their ssh and linux
kernel.

I have personally checked all places where ssh displays debugging
messages, log messages, or otherwise uses functions like sprintf.  I
was unable to find any vulnerabilities.

I have talked to people at both CERT and the IBM emergency response
service and none of them seems to have any knowledge of any
vulnerability in SSH.

In summary, to my best knowledge, ssh-1.2.26 can be safely used.

Please communicate this information to the relevant people.

Brief history of events:

  - On October 28, the rootshell.com home page was defaced by
    hackers.  After the host was brought up to date, their front page
    contained information that listed the services that had been
    active, and mentioned that entry may have been made with ssh.
    (Note that this does not by itself indicate anything; password or
    other authentication may have been obtained at the other end)

  - On October 29, a message about the rootshell case is posted to
    bugtraq and possibly other mailing lists.  Many people took this
    as indication of a vulnerability in ssh.

  - We looked at the rootshell case, and found no cause for alarm, but
    decided to be watching.

  - On October 30, IBM sent an draft advisory reporting a buffer overflow
    vulnerability that could be used to gain root access to any host
    running ssh from anywhere on the Internet.  The draft advisory was
    sent to at least CERT, FIRST, ssh-bugs, and a few other places.

  - On october 30, several major computer manufacturers and their
    offices around the world were advising their customers to follow
    the situation, and possibly disable ssh for now.  Some CERTs
    around the world issued preliminary alerts to their most important
    sites.

  - I learn of the IBM advisory on October 31 at 2 AM.  By 6 AM I've
    talked to both CERT and IBM Emergency Response Team, checked the
    code claimed to be at fault (finding no problem), and no-one seems
    to have any concrete information, and we conclude there is no
    cause for immediate alarm.

  - By November 1, the IBM researchers who found the vulnerability in
    the IBM draft advisory have been reached.  One of them says he
    never saw an exploit, and the other first said he had an exploit
    and he was going to send it over shortly, and the next day he said
    that he could no longer reproduce the problem after recompiling
    ssh.  He does not appear to have an exploit after all.

  - I've personally gone through all places where ssh1 passes
    information to sprintf, log_msg, or any other functions using
    sprintf.  I found no security problems.  I found one place where
    an argument to a format string was missing, but it is probably not
    exploitable, and one place where one byte less was allocated for a
    string than was used (only appears on Solaris).  Neither of these
    have security consequences or are cause for alarm.

  - On November 1, the IBM announcement for which IBM has already issued
    a cancellation is widely distributed by rootshell through their
    announcement list.

  - Now at Morning November 2, I'm convinced (>99% sure) that both
    the rootshell issue and the IBM draft advisory were false alerts.

We are also trying to track down the linux compilation problem that
may have caused the false alert behind the IBM advisory.  We will
issue an announcement as soon as possible if real vulnerability is
found.

For more information, please keep tracking
http://www.ssh.fi/sshprotocols2.

Best regards,

    Tatu Ylonen <ylo@ssh.fi>

- --
SSH Communications Security           http://www.ssh.fi/
SSH IPSEC Toolkit                     http://www.ipsec.com/
Free Unix SSH                         http://www.ssh.fi/sshprotocols2/

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-----------------
Robert A. Hettinga <mailto: rah@philodox.com>
Philodox Financial Technology Evangelism <http://www.philodox.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'