From: InfoSec News (isnc4i.org)
Date: Tue Apr 01 2003 - 03:47:24 CST

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| Linux Security: Tips, Tricks, and Hackery |
| Published by Onsight, Inc. |
| |
| 01-April-2003 |
| http://www.hackinglinuxexposed.com/articles/20030401.html |
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Vulnerabilities in the Media -- who to trust?
By Brian Hatch

Summary: There are a variety of people and entities that publish
information about security problems. Who should you trust?

It seems that there are more sources of information about Security
problems every day. The hardest part about trying to keep up with it
all is to figure out who to trust. Let's take a recent example.

Back in mid February, 2003, scientists at a Swiss university were
able to exploit a weakness in an SSL implementation to allow them to
discover the password being repeatedly sent in many SSL-wrapped IMAP
sessions.

The Facts

  * This only affected the OpenSSL implementation of SSL
  * The vulnerability relied on a timing attack - the SSL server
    would not perform all it's number crunching if it found that the
    data had been tampered with. By tampering with the inbound data
    in a careful manner, they were able to determine how 'valid' it
    was by measuring the time it took for the server to complain.[1]
  * Any malicious hacker, in order to perform this kind of attack,
    would need to be able to rewrite packets as they were
    transmitted, man-in-the-middle fashion. One could not sit
    passively and listen to perform this attack.
  * The data to be decoded needs to be in a predictable location, and
    sent frequently enough[2] times that they can discover the
    plaintext.
  * Each time they try to attack an SSL session, the client and
    server will notice the error. You'd not successfully get your
    email while you were being attacked, and you'd probably stop
    trying after a while, or ask the administrator to check things
    out. by their

The Hype

Shortly after the announcement, every website with a readership of
three or more seemed to be saying that SSL had been broken -- the end
of the Internet was near -- all your passwords are belong to us. In
the huge noise some amazingly erroneous statements were made:

  * "Hackers can read all your data now"
   
    No, they can only try to manipulate your transmissions to decode
    a particular section of it. This sensitive info needs to be in a
    predictable place each time.
   
  * "The attack only affects webmail"
   
    No idea where they came up with this one - the attack was tried
    out on IMAP over SSL. Webmail is usually straight HTTPS, and the
    password may only be sent once, and cookies used thereafter.
    Additionally, the sensitive data could move around for subsequent
    connections making it impossible to be sure what to attempt to
    decrypt.
   
  * "SSL has been broken!"
   
    No, just one particular SSL implementation - OpenSSL - had the
    vulnerability, and it was fixed shortly thereafter.
   
  * "The flaw is in SSL, not a particular implementation!"
   
    No, didn't you just listen to me?
   
  * "Old SSL sessions you've used can now be decrypted! Change your
    passwords!"
   
    No, the attacker needed to attack you at the time you were using
    SSL. But you should change your password anyway -- "Linus" was
    too easy to guess.
   
  * "You'd never know you'd been hacked!"
   
    No, any manipulation by the attacker destroys the SSL connection,
    so you'd get obvious errors and know something was amiss.
   
  * "It only affects (Outlook/Hotmail/Yahoo)"
   
    The tests were done against Outlook, true, but any client
    software that sends a password frequently in a predictable
    location would have been vulnerable. Hotmail and Yahoo don't.
   
  * "It only affects IMAP"
   
    No, it could affect anything where a password or something else
    'secret' is in a predictable place, for example if you're using
    HTTP Basic authentication. The location will vary a lot more -
    it's not nearly as defined as an IMAP connection which always
    begins with login/password right up front.
   
The voices of authority All sorts of places reported and
sensationalized the problem. It was a mad rush to have the first
story.

Then came the experts.

The security geeks and cryptographers came out and tried to shed some
light on the actual cause and likely attack scenarios. They explained
what was actually broken, how it was being fixed, and how the "end of
the Internet" was going to need to wait for another day. Some sites
updated their articles to reflect this 'new' data. Others left the
articles untouched, while others removed them but posted no
retractions.

The analysis

With all the hubbub, rumours, and apocalyptic warnings, who are you
to believe when news about a new vulnerability comes to light? Here's
a very quick list:

  * The folks to avoid:
      + Open Source Vendors
        These guys clearly have something to hide, and should not be
        trusted. The guys who develop OpenSSL keep everything about
        their product under lock and key - in order to see the actual
        source code, you need to use esoteric commands like gunzip or
        tar. Some Open Source developers even use the GPL license,
        which is equivalent to a virus according to a reputable and
        impartial software development firm based in Redmond, WA. I
        don't think you should trust Open Source vendors - far to
        shifty, those folks are. You can never really know what
        they're up to.
       
      + Scientists
        These guys take the time to provide a well written
        description of the problem, how they exploited it, and what
        needs to be fixed. They are obviously not worth listening to.
        They use drab, boring, unintelligible "science speak" not
        because it's the most effective way of communicating without
        colouring the data with emotion, but because they did not
        have enough training in bad computer lingo. Had they spent
        their time in college learning to write exclusively using
        words and phrases like "cyberwarrior", "hack attack" and
        "Internet superhighway", do you think they'd use the language
        of mathematics and science? I think not. Somehow that drab
        language is supposed to be sensationalistic and generate lots
        of hype by average joes. I don't quite know how, but it's
        some sort of plot.
       
      + Independent Experts
        It is well known that independent security experts are merely
        individuals that didn't have enough luck to land a
        high-paying job at a big anti-virus or managed security
        company, and will lie, cheat, and do anything they can to be
        noticed in hopes that they can get one. Don't let that whole
        "independent" part confuse you - they answer to somebody, by
        not being an obvious lackey of a big security firm, you don't
        know who it is! Experts? How can they be? Only megacorps can
        have experts, it's a law or something. If you take out
        "independent" and "expert" from "independent experts" what
        are you left with anyway? Just the letter "s", and what good
        is that?
       
  * The folks to trust:
   
      + Online Media
        These guys know that you can surf to any other site just as
        easily as theirs. They know that you don't need to wait a
        week to get a paper publication, you want your information
        now. To assure technical accuracy of all their articles, they
        keep a staff of at least seventy trained professionals from
        each area that they may cover in their stories. Yep, those
        "SSL is broken" articles went through some really strict
        scrutiny by trained staff cryptologists before being
        published far and wide moments after the original scientific
        publication was announced. They also have a huge Artificial
        Intelligence program that helps check sources in the off
        hours when the editors are sleeping.
       
      + Slashdot Users
        One of the requirements before you sign up for a Slashdot
        account is that you show proof of expertise in certain areas,
        and you are only allowed to post in those areas you are
        qualified for. You must also have continuing educational
        credits to maintain your right to post.
       
      + Al Gore
        The only slashdot user who doesn't need to take the
        continuing educational credits is Al Gore. He's been
        grandfathered on slashdot, since he created the Internet. He
        has exclusive right to the slashdot handle "Anonymous
        Coward", and he posts very frequently.
       
      + George W. Bush
        Come on, if Al Gore is on this list, and more than 50% of US
        voters think Bush is smarter than Al, clearly GWB should be
        trustworthy. And what's this "electoral college" thing I kept
        hearing about in 2000?
       
      + Steve Gibson
        Sure, he didn't pipe up about this vulnerability at all, but
        he's the single voice that told us how awful raw sockets in
        Windows XP are, and how the Internet would melt shortly after
        it was released. And he independently created a new form of
        SYN cookies to save us all from the frequent denial of
        service attacks he seems to constantly be attacked with.
        Sure, all that work by Bernstein and Schenk back in 1995 to
        create SYN cookies was wasted. "SYN cookies"? Come on, that's
        not marketable. But Gibson's "GENESIS" - now that has a ring
        to it. Who cares if it doesn't work.
       
      + Columnists/Authors
        Anyone who writes a column on April Fool's day is certainly
        trustworthy - wouldn't you agree?[3]

Ok, all April Fool's kidding asside, here are some links that discuss
the OpenSSL bug that I talked about. It's been fixed for a while, and
the Linux distros have had new OpenSSL library packages available
since the end of February at the latest.

http://lasecwww.epfl.ch/memo_ssl.shtml
    The actual writeup about the attack
   
http://www.openssl.org/news/secadv_20030219.txt
    OpenSSL's advisory about the problem, announcing the fixed
    versions.
   
http://news.bbc.co.uk/1/hi/technology/2785145.stm
    The BBC's version of the story. They've edited it heavily to make
    it more accurate than the first version.
   
http://slashdot.org/article.pl?sid=03/02/20/1956229
    The Slashdot discussion about the vulnerability
   
http://www.cnn.com/....
    I can't find the CNN page any more, but it was an absolute gold
    mine for erroneous information.
   
http://zdnet.com.com/2100-1105-985460.html
    ZDNet's "experts discredit e-mail security cracks" followup
    article.

NOTES:

[1] The solution was to perform all the number crunching, even if the
data was invalid, and then send back an error, thus eliminating the
difference in timing results.

[2] They claimed to be able to decrypt an IMAP password by
interfering with the connection 160 times.

[3] Ok, so I had a little fun with the "who's trustworthy" part of
this article. But all the OpenSSL timing vulnerability stuff is
accurate, including the degree of erroneous information portrayed in
the media.

                            -------------
Brian Hatch has been developing Open Source Linux products since
1985, created the RedFishBlueFish block cipher used by default in SSL
4.0 servers, raises prize-winning alpacas in his back yard, and has
an annual bake off that raises over 500 million dollars to be donated
to needy Microsoft execs. Brian can be reached at
brianhackinglinuxexposed.com.

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