[IPsec] Identifying encrypted traffic (was: Reauthentication extension for IKEv2)

[Yaron Sheffer <[e-mail]>]

Hi Gary,

 

I'm puzzled by the scenario you are presenting. I've been considering the
work on ESP-null detection (e.g. draft-grewal-ipsec-traffic-visibility-01)
as useful for middleboxes that want to look at the IPsec-protected traffic,
but do NOT want to terminate IPsec (i.e. decapsulate the traffic). In
general, if you can terminate IPsec, that means that you have access to the
encryption keys and you can easily differentiate protected and unprotected
traffic, Can you explain the use case that you have in mind?

 

Thanks,

            Yaron

 

  _____  

From: [e-mail] [mailto:[e-mail]] On Behalf Of
Gary Hemminger
Sent: Monday, October 20, 2008 20:26
To: Yoav Nir
Cc: [e-mail]
Subject: Re: [IPsec] Reauthentication extension for IKEv2

 

I was talking about how to make the determination that the payload is
encrypted.  Evidently there are two approaches:  one based on a heuristic,
another based on a payload wrapper that flags the payload is encrypted.  We
would need some mechanism to determine the payload is encryped if we need to
terminate the IPSEC traffic and make a determination of which server to send
it to.  Sorry about the confusion.

 

Gary

 

  _____  

From: Yoav Nir [mailto:[e-mail]]
Sent: Sat 10/18/2008 2:03 PM
To: Gary Hemminger
Cc: [e-mail]
Subject: Re: [IPsec] Reauthentication extension for IKEv2

Hi Gary. 

 

I'm not sure what heuristics you are talking about. The problem of
re-authentication is simply this. The owner of the remote access gateway has
a security policy that says that connections can be open for only so long
(say, 2 hours) without authenticating the user again. This is a favorite
requirement by auditors, who believe that this is an important part of risk
management. If somebody steals your laptop (or mobile phone) or sits down at
the Internet Cafe station where you were logged on, we want to limit the
amount of time they are connected to the internal network. This requirement
makes sense if the user has to type in their password to authenticate. It
makes less sense if there are user certificates that are stored on the
computer, or if the client software has a "save password" feature.

 

Whether it makes sense or not, this is a requirement by auditors and
regulators. If the user does not re-authenticate within the specified time,
the IKE SA and all dependent child SAs are deleted.  This creates a
usability problem, because the SA is deleted without any advance warning to
the user, so the user is likely to get a relatively long time with no
connectivity. This can break TCP connections such as FTP, HTTP, and IMAP.
Outlook tends to make accounts permanently offline when this happens.

 

RFC 4778 and the improvement that Martin Willi is proposing, are aimed at
solving this usability problem by informing the client software in advance
when the re-authentication needs to be done, and allowing them to
re-authenticate early enough, so that connections are not broken. The
heuristic does not affect the security or the IPsec streams.

 

Yoav

 

On Oct 18, 2008, at 2:35 AM, Gary Hemminger wrote:






One comment on the heuristics approach.  As a hardware vendor of L4-7 ADC
boxes, I am a little concerned about having to terminate IPSEC streams based
on the heuristics approach, because this is open ended.  What I mean is that
the heuristic may be easy to define now, but there is no certainty that it
would remain this way.  My past experience suggests that eventually the
heuristic would become too complex, and a well defined mechanism for
determining which payload is encrypted would need to be employed anyway.   


While I like the idea of some "other" box having to solve this issue, which
prevents clients from having to be changed, as we are a vendor of the
"other" box, I think we should think about the long term, not the short
term.  Just my opinion, and I am certainly flexible, but the heuristics
approach worries me a bit.


 


Gary


 


[IPsec] Reauthentication extension for IKEv2

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*	Subject: [IPsec] Reauthentication extension for IKEv2 
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  _____  

Martin Willi writes:
> What do you think about such an extension? Already considered something
> similar, or does your reauthentication procedure work hassle-free? I'm
> wondering if we are the only ones facing these problems or if such an
> extension would gain broader acceptance...
 
The first question I have is why are you doing reauthentication at
all?
 
What is the benefits of the reauthentication?
 
What is the benefits of the reauthentication that can be done WITHOUT
user intervention (i.e. no user typing in password or pin code or
fingerprint or similar)?
 
I myself can only really see benefits from reauthentication when it
does require that user is really sitting there on the machine, and
gives something that the machine itself cannot give. In those cases
the user is required to type in something or do something anyways,
thus it does not really matter if the communications is interrupted
for second if user must stop his work for much longer time to type in
his passphrase or pin code.
 
The RFC 4478 simply skips this question and says "With some IPsec
peers, particularly in the remote access scenario, it is desirable to
repeat the mutual authentication periodically. The purpose of this is
to limit the time that security associations (SAs) can be used by a
third party who has gained control of the IPsec peer."
 
In most cases if third party has gained control of the IPsec peer he
will also get control of all authentication information inside the
peer, including private keys and pre shared keys. Only way to make
sure that he does not get access to those is to protect them with
passphrase, or pin code or similar that is only known by the user.
 
This is also said out in the RFC 4478: "However, in the remote access
scenario it is usually up to a human user to supply the
authentication credentials ..."
 
Because of this I do not think there is that much requirement for
reauthentication protocol that is faster than what we already have. 
-- 
kivinen at safenet-inc.com
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