[22755] in bugtraq
Re: Websphere cookie/sessionid predictable
daemon@ATHENA.MIT.EDU (Arun Kumar)
Sun Sep 30 02:34:49 2001
Date: 28 Sep 2001 22:34:48 -0000
Message-ID: <20010928223448.28700.qmail@www2a.securityfocus.com>
From: Arun Kumar <akumar@austin.ibm.com>
To: bugtraq@securityfocus.com
In-Reply-To: <98A3855A9087D411952F00508B61BD400268C688@ZAJNBNT006>
Hi Everyone,
It is critically important to note that the reported issue
of session ID
generation is NOT an issue in any version of
Websphere Application
Server 4.X. It has been reported that PQ47663V302
should be applied
to Websphere Application Server V4.X. Please do
not follow these
directions. This patch is not supported on
Websphere Application
Server 4.X, hence any server with this patch is in an
unsupported
configuration. The issue is, however, a reasonably
accurate description
of a known and resolved issue in 3.X versions of
Websphere Applicaton Server.
PQ47663V302 is a resolution to this issue on any
release of Websphere
Application Server V3.02. There are versions of this
patch available
for 3.5.1, 3.5.2 and 3.5.3 as well. These fixes have
been available
since 5/1/2001. The site to obtain these from is
http://www-
4.ibm.com/software/webservers/appserv/support.html
.
After applying the aforementioned patches to 3.02 or
3.5, the session
generation algorithm is identical to that of Websphere
Application
Server V4.X. This algorithm is essentially totally
random and is based
on JCE which is widely recognized as one of the
most sophisticated
random ID generators.
Also, we do not recommend relying on the session ID
alone as a form of
securing session data. If security is enabled and the
accessed URLs
are protected, the user must be authenticated to
proceed. Websphere
session and security code have been integrated such
that each session
access compares the authenticated user with the
owner of the session.
If these do not match, the session access is rejected
with an
UnauthorizedSessionRequestException.
--Arun Kumar
IBM
WebSphere Service and Support.
>Received: (qmail 29550 invoked from network); 20
Sep 2001 16:01:28 -0000
>Received: from outgoing2.securityfocus.com
(HELO outgoing.securityfocus.com) (66.38.151.26)
> by mail.securityfocus.com with SMTP; 20 Sep
2001 16:01:28 -0000
>Received: from lists.securityfocus.com
(lists.securityfocus.com [66.38.151.19])
> by outgoing.securityfocus.com (Postfix)
with QMQP
> id 319048F2B9; Thu, 20 Sep 2001
09:55:05 -0600 (MDT)
>Mailing-List: contact bugtraq-
help@securityfocus.com; run by ezmlm
>Precedence: bulk
>List-Id: <bugtraq.list-id.securityfocus.com>
>List-Post: <mailto:bugtraq@securityfocus.com>
>List-Help: <mailto:bugtraq-
help@securityfocus.com>
>List-Unsubscribe: <mailto:bugtraq-
unsubscribe@securityfocus.com>
>List-Subscribe: <mailto:bugtraq-
subscribe@securityfocus.com>
>Delivered-To: mailing list
bugtraq@securityfocus.com
>Delivered-To: moderator for
bugtraq@securityfocus.com
>Received: (qmail 2797 invoked from network); 20
Sep 2001 11:14:28 -0000
>Message-ID:
<98A3855A9087D411952F00508B61BD400268C688
@ZAJNBNT006>
>From: "Dawes, Rogan (ZA - Johannesburg)"
<rdawes@deloitte.co.za>
>To: "'marc@suse.de'" <marc@suse.de>,
bugtraq@securityfocus.com
>Subject: RE: Websphere cookie/sessionid
predictable
>Date: Thu, 20 Sep 2001 13:13:37 +0200
>MIME-Version: 1.0
>X-Mailer: Internet Mail Service (5.5.2653.19)
>Content-Type: text/plain;
> charset="iso-8859-1"
>
>Hi,
>
>I did a similar analysis with an older version of
WebSphere (3.2) for a
>client, and have one comment to make that maybe
you didn't pick up (or may
>have been fixed in the interim):
>
>SessionID TIME
>TWGYLZIAAACVDQ3UUSZQV2I
10:27:12
>TWGY0WYAAACVFQ3UUSZQV2I
10:27:13
>TWGZNZAAAACVHQ3UUSZQV2I
10:27:14
>TWG0BUYAAACVJQ3UUSZQV2I
10:27:15
>TWG0VIAAAACVLQ3UUSZQV2I
10:27:16
>TWG1ICIAAACVNQ3UUSZQV2I
10:27:17
>TWG111YAAACVPQ3UUSZQV2I
10:27:18
> yyy
>
>What I found was that the section marked "yyy"
incremented by 2 for each
>REQUEST made, not by time. So it is trivial to make
a request every second,
>making sure that the next number is only two from
what your last number was.
>If it was not, then someone ELSE has requested a
session, and you should
>begin brute forcing the interval between your
previous and current
>sessionids. The shorter the interval between
requests, the smaller the space
>to brute force, obviously.
>
>Perhaps someone can check if this patch also fixes
that property of the
>sessionid generation?
>
>Rogan
>
>-----Original Message-----
>From: marc@suse.de [mailto:marc@suse.de]
>Sent: 19 September 2001 07:44
>To: bugtraq@securityfocus.com
>Subject: Websphere cookie/sessionid predictable
>
>
>Hi folks,
>
>about three weeks ago, I discovered a hole in IBM's
websphere 4.0 session ID
>generation. Over a week ago, IBM made a fix for this
available, so here is
>the information about the vulnerability:
>
>(everybody who don't want to read about this
vulnerability and just want to
>know the patch info: install the eFix PQ47663V302)
>
>INTRO
>websphere can generate sessionids which are put
into cookies for users, to
>be able to supply user tracking, e.g. user
authenticates with userid and
>password, and access to data is checked by
checking if the sessionid is
>authenticated or not.
>
>
>THE BUG
>during a security assessment for a bank, I collected
several sessionids and
>they did not look that random to me ...
>
>SessionID TIME
>TWGYLZIAAACVDQ3UUSZQV2I
10:27:12
>TWGY0WYAAACVFQ3UUSZQV2I
10:27:13
>TWGZNZAAAACVHQ3UUSZQV2I
10:27:14
>TWG0BUYAAACVJQ3UUSZQV2I
10:27:15
>TWG0VIAAAACVLQ3UUSZQV2I
10:27:16
>TWG1ICIAAACVNQ3UUSZQV2I
10:27:17
>TWG111YAAACVPQ3UUSZQV2I
10:27:18
> xxxx y
>
>You can see that for seven requests, only 5
characters changed, and:
>* the characters A-Z and 0-9 are used, hence 36
combinations possible per
>char
>* the sessionid is based on two counters which are
counted up, the rest of
> the string seems to be fixed.
>* the first counter (xxxx) seems to count
milliseconds (TWGxxxx), but
> counts a bit too slow (see seconds 15 and 16,
where both 1st rows of the
> counters start with a 0). well, to cut a long story
short, it is really
> a counter which increases 65536 times per
second and is then encoded to
> the A-Z0-9 format.
>* If you collect many sessionids (I collected 1000,
it's obvious then),
> you'll see that the the least signifcant char of the
first counter are 95%
> of the time showing a Y, I, A or Q. The reason for
that is (my guess) that
> the clock of the machine only can increase 7.500-
10.000 times instead of
> 65536 because it's not a realtime clock and the
server type is not a cray
>:-)
>* The second counter (y) is increasing by two every
second.
>The counters are in fact longer than 4, but this is the
visible changes in
>the example above.
>
>Then the guess was that the fixed strings may be
based on the IP of the
>client. So I checked with different IP addresses, but
no difference in the
>fixed strings of the sessionID.
>
>
>THE RISK
>If someone knows the time of the connect to the
server (even with SSL
>encrypted) an attacker can issue requests with
changing sessionids until
>it's the correct one. If an attacker just wants to have
any user data, he
>can constantly try some guessing.
>As the first counter only has 7.500-10.000 values
per second, and the
>seconds counters just increases approx. once per
second (or perhaps per
>request), the sessionid can have 7.750 to 10.500
different values.
>If a user is normaly connected for 15 minutes after
authentication to an
>eCommerce system (and does not forget to logout,
otherwise the time is
>extended by the session timeout). As an attacker is
likely to succeed after
>50% of the keyspace, he needs 3.875 to 5.250
attempts, so 4 to 5 requests
>per second are enough.
>Two customers were using the sessionids for the
security of their eCommerce
>system ... we are not talking about some weird
feature nobody uses.
>Short: it is an easy and likely attack.
>
>
>THE FIX
>install eFix PQ47663V302 and feel better
>
>
>THANKS
>to the IBM websphere team, which fixed the bug
pretty fast for the customer.
>
>
>
>Greets,
> Marc
>--
> E@mail: marc@suse.de Function: Security
Research and Advisory
> PGP: "lynx -source
http://www.suse.de/~marc/marc.pgp | pgp -fka"
> Key fingerprint = B5 07 B6 4E 9C EF 27 EE 16 D9
70 D4 87 B5 63 6C
>Private: http://www.suse.de/~marc SuSE:
http://www.suse.de/security
>
