Re: IE https certificate attack
From: Oscar Batyrbaev (batyr@ix.netcom.com)Date: 12/24/01
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From: "Oscar Batyrbaev" <batyr@ix.netcom.com> To: <security@e-matters.de>, <bugtraq@securityfocus.com>, "SecurityFocus Incidents" <INCIDENTS@SECURITYFOCUS.COM>, <vuln-dev@securityfocus.com> Date: Sun, 23 Dec 2001 19:31:04 -0800
Hi,
A related question would be:
How non-interactive ssl clients in EAI and web services software handle
these cases and MIM attacks of this sort? Examples are: WebMethods, MS BTS,
etc. ssl clients (there is no user intervention involved).
TIA,
----- Original Message -----
From: <security@e-matters.de>
To: <bugtraq@securityfocus.com>
Sent: Saturday, December 22, 2001 6:37 AM
Subject: IE https certificate attack
> e-matters GmbH
> www.e-matters.de
>
> -= Security Advisory =-
>
>
>
> Advisory: Interner Explorer HTTPS certificate attack
> Release Date: 2001/12/22
> Author: Stefan Esser [s.esser@e-matters.de]
>
> Application: Microsoft Internet Explorer 5.0/5.5/6.0
> Severity: Vulnerability in IE's SSL Certificate handling allows
> undetected SSL Man-In-The-Middle attacks
> Risk: Very High
> Vendor Status: Notified
> Reference: http://security.e-matters.de/advisories/012001.html
>
>
>
> Overview:
>
> A flaw in Microsoft Internet Explorer allows an attacker to perform
> a SSL Man-In-The-Middle attack without the majority of users
recognising
> it. In fact the only way to detect the attack is to manually compare
the
> server name with the name stored in the certificate.
>
> For a basic introduction into SSL MIM attacks I recommend reading:
>
> Phrack #57 - Hang on, Snoopy (by stealth)
> http://www.phrack.org/show.php?p=57&a=13
>
>
> Details:
>
> There is a flaw in the way IE checks HTTPS objects that are embedded
into
> normal HTTP pages. According to my tests IE does only check if the
certi-
> ficate of the HTTPS server is properly signed by a trusted CA but
totally
> ignores if the cert was issued onto the correct name or has already ex-
> pired. This is in fact not dangerous because the user considers HTTPS
> objects embedded in a HTTP page not secure. The problem is that IE
flags
> the certificate as trusted and caches this certification trust until
your
> browser session ends. That means once you visited a normal http page
that
> included an image from the MIMed SSL Server, IE will not warn you about
> an illegal site certificate as long the certificate was signed by f.e.
> Verisign.
>
> A possible scenario would be:
>
> Hacker runs a MIM attacking tool for HTTP/HTTPS in the subnet of your
> site. The HTTP part of the tool auto appends
>
> <img src="https://www.yoursite.com/nonexistent.gif" width=1 height=1>
>
> to any html page that is returned to your customer's browser and the
> HTTPS part presents his browser a valid but stolen certificate for
> www.shop.com. IE will only check if the cert was signed by a trusted CA
> when trying to display the image and won't compare the name inside the
> cert or check the expiration date. If your customer now tries to login
> to your site via HTTPS IE will consider the cert trustworthy without
> checking it again. Your customer will only be able to determine that he
> was just tricked by manually checking the servername in the cert. But
> you can be sure that only paranoid people would check. The majority of
> people don't even know how they can do so. Imagine the hacker stole the
> cert from "yoursite.de"... How many users of "yoursite.com" would not
> trust a cert that was issued on "yoursite.de". The average user does
> not know anything about SSL than it's making his payment "secure".
>
>
> Proof of Concept:
>
> A proof of concept webpage was put up at http://suspekt.org. Clicking
> onto the "To the secure page..." link will send your browser to
> https://suspekt.org without IE warning you that the certificate was not
> issued onto that server.
>
> This is not a MIM but it has the same effect: IE will tell you a page
is
> secure although the certificate is illegal and its possible for a third
> party (anyone who owns the given certificate) to decrypt your traffic
in
> realtime.
>
>
> Vendor Response:
>
> 26 November 2001 - Microsoft was informed about this vulnerability
> 27 November 2001 - Proof of concept page got visited by lots of MS
IPs
> 01 December 2001 - Microsoft informed us with a standard reply that
> they have received the advisory
> 12 December 2001 - Microsoft was informed that were going to release
> the advisory within the next 3 days
> 13 December 2001 - Microsoft asked us to wait because the issue is
> complex due to the fact a lot of cryptography
> is involved
> 21 December 2001 - Microsoft sent an update: no patches yet,
> still a complex issue
>
>
> Conclusion:
>
> Until today Microsoft did not release a patch, they had nearly a month
> time to fix the bug. Instead they call it a very complex issue. Because
> I don't know the source code of the Internet Explorer I cannot check
the
> validity of these claims, but from my point of view fixing this missing
> check is just a matter of copy and pasting a few lines. Unfortunately
it
> is christmas time and especially during the last month millions of cus-
> tomers where buying christmas presents on the internet all around the
> world. That means millions of customers were shopping with insuffient
> protection of their private data. Because there are no patches out yet,
> I strongly recommend that you use Mozilla, Opera or another non MS
brow-
> ser to do your internet banking or shopping these days. If you think
> (for whatever strange reason) that you need the Internet Explorer,
> ensure that the certificate is the correct by comparing the servername
> in the certificate with the one in your browser...
>
>
> GPG-Key:
>
> http://security.e-matters.de/gpg_key.asc
>
> pub 1024D/D19C5835 2001-11-26 e-matters GmbH - Securityteam
> Key fingerprint = DD27 8C4B CEDE 41A9 5766 39BA AF65 B19C D19C 5835
>
>
> Copyright 2001 Stefan Esser. All rights reserved.
>
>
>
>
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