-----Original Message-----
From: tls-bounces(_at_)ietf(_dot_)org
[mailto:tls-bounces(_at_)ietf(_dot_)org] On
Behalf Of Michael D'Errico
Sent: Tuesday, September 29, 2009 4:48 PM
To: martin(_dot_)rex(_at_)sap(_dot_)com
Cc: simon(_at_)josefsson(_dot_)org; ietf(_at_)ietf(_dot_)org;
tls(_at_)ietf(_dot_)org
Subject: Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis
(Transport Layer
I do not see why you consider this a vulnerability in the
_server_!
Because a malicious client could theoretically establish a secure
connection using one server domain and then ask for pages from a
different domain. If the server does not check for this, it could
potentially leak sensitive information.
You're barking up the wrong tree. If the client did not
use TLS, the
server wouldn't even know that.
You must be talking about a particular server implementation
that has this shortcomings. There is nothing inherent in TLS
that prevents a server from knowing when it is used. Your
library and/ or use of that library is the problem.
It is inappropriate to assume that virtual hosting provides
seperation
of content and draw a conclusion that, when accesses via
HTTPS, will
provide a secure seperation of content instead.
I'm not assuming anything; I have written a TLS library and
an HTTP server that provides the separation of content that
you deny is possible.
If the lack of such a server-side check is a problem for
your server,
then your server problably has a severe design flaw in its session
management.
I never said my server suffered from this problem....
And I'm curious: why do you call matching the commonName weak?
Because in the vast majority of situatins it is the last step in a
long row of flawed assumptions.
OK, so you are complaining about the entirety of e-commerce
on the web. Do you have any proposed solutions to these problems?
Mike
Security is only as strong as its weakest link. The authentication
process based on a DNSName involves a number of very weak
authentications.
DNS domain names are not very genuine, and it is very non-obvious
which domain names are used by the business or peer someone
is looking
for and which are used by others (different businesses with
the same
name, cybersquatters or attackers). Most HTTPS-URLs opened by Web
Browsers are served through plaintext HTTP pages.
Then most Browser PKIs come with a hundred or more trusted CAs
preconfigured, and browsers trust them equally. Whether or
how secure
the authentication is that the CA performs before issuing a
certificate is another flawed assumption that weakens the
rfc-2818 server endpoint authentication.
A final flaw that is still present in most browsers is the lack of
memory. Not memorizing the certificate that a server
presented on the
last contact perpetuates the weakness of the original
authentication.
Personally, I think that deriving a server endpoint
identifier from a
network address is the most flawed assumption of all.
That is like asserting that if someone opens on a random
door on which
you knock, and shows you an ID card with the correct street
address --
then he must be a GOOD guy.
-Martin
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