Subject: RE: Why not TLS was Re: [Syslog] Secure substrate - need your input

From: "Moehrke, John \(GE Healthcare\)" <[email-masked]>
Date: Wed, 26 Oct 2005 11:07:53 -0500

There is a miss understanding of the information I have seen given by
many people on this list regarding TLS.  I think this miss understanding
is also being applied to SSH.

Most people get the facts right on server-side-authentication. SSL for
years supported Server side authentication. This allows a common-user to
know that they are indeed connecting to the right service. Thus they
know that this is indeed their bank that they are providing their
credentials to. There is a wealth of standards and tools that accomplish
this.

The facts get much more confused when people start to add requirements
to authenticate the client side. The first confusion comes when people
don't really ask 'who do they want to authenticate?' Most common
authentication schemes want to authenticate the user. The advantage to
these services is that they then can apply preferences, user behavior
tracking, access controls based on user/role, etc. The problem with this
mode of client authentication is that the service knows nothing about
the machine that the user is using at this time. For most portals this
is a benefit as it allows the user to use any kiosk, thus user
frustration is low. The problem is that that kiosk could be highly
compromised... Enough said. 

Thus there is a need to authenticate the client-machine. Given the above
concern, this is becoming more and more common. 

So, SYSLOG needs to ask do they want to authenticate the user, machine,
or both?

TLS does support mutual node authentication. The healthcare world has
been using mutual-node-authenticated-TLS for over three years. We use it
often to ensure that a X-Ray device is actually talking to the Picture
Archiving Service. Both systems need to know that they are talking to
the right 'other' system. This transaction doesn't need to have user
authentication as the process is fully automated. Indeed we don't always
turn on TLS encryption. But we do always do mutual-authentication. Yes
this means that there is a X.509 certificate managed for both nodes. But
this certificate management is not nearly as complex as
person-certificates (another discussion we can have on
miss-understandings due to the wrong questions being asked).

The problem is that many people quickly associate TLS/SSL with it's
earlier SSL, which leads to HTTPS, which leads them to look at browsers.
The end result is that you find at most one browser that supports
mutual-authenticated-TLS. Note that the browsers will claim to
authenticate the 'client', but this is HTTP-authentication. This
HTTP-authentication is a different layer than the TLS authentication.

I don't think that the SYSLOG community is likely to be using browsers.
They will likely be using tools like JAVA, and the good news is these
tools do support mutual-node-authentication (See: JAVA SSLSocket).

John

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---

From: "Tom Petch" <[email-masked]>
Date: Wed, 26 Oct 2005 19:21:42 +0200

<inline>
Tom Petch

----- Original Message -----
From: "Moehrke, John (GE Healthcare)" <[email-masked]>
To: <[email-masked]>
Sent: Wednesday, October 26, 2005 6:07 PM
Subject: RE: Why not TLS was Re: [Syslog] Secure substrate - need your input

<snip>

Tom - yes, agree strongly but I don't know the answer.

Tom- this one puzzles me.  SSH has got server and client authorisation defined
in the I-Ds, soon to be RFCs.  Reading the TLS I-Ds I see no sign of client
authorisation and since that is a must for SNMP, then the note I quoted earlier,
to the isms list, saying that SASL would needed alongside TLS made perfect sense
(as I would expect since it came from the Security AD:-).  So where does mutual
authentication come from?  What RFC or I-D defines it?  Is it a proprietary
extension? Is it two simplex transmissions with only server authentication?
Sometimes it does matter to know what goes on under the covers.  (Of course, if
client authentication is not needed then this is academic).

<snip>
John