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

[Yaron Sheffer <[e-mail]>]

In that case, the load balancer can identify the traffic using the normal
ESP SPI field, and knows exactly what kind of traffic it is and whether it
is encrypted. There is no need to change the ESP protocol for this scenario.

 

Thanks,

            Yaron

 

  _____  

From: Gary Hemminger [mailto:[e-mail]] 
Sent: Wednesday, October 22, 2008 2:00
To: Yaron Sheffer; Grewal, Ken; Yoav Nir
Cc: [e-mail]
Subject: RE: [IPsec] Identifying encrypted traffic (was: Reauthentication
extension for IKEv2)

 

The client would negotiate IKE  with the load balancer and would not
directly negotiate with the Server.

 

Gary

 

From: Yaron Sheffer [mailto:[e-mail]] 
Sent: Tuesday, October 21, 2008 3:23 PM
To: Grewal, Ken; Gary Hemminger; Yoav Nir
Cc: [e-mail]
Subject: RE: [IPsec] Identifying encrypted traffic (was: Reauthentication
extension for IKEv2)

 

Hi Ken,

 

Thanks for the clarification. But I still don't understand how your scenario
works.

 

Assume for simplicity an environment where everybody uses ESP in transport
mode, with null encryption.

 

Client C1 does an IKE negotiation with a random server (as selected by the
load balancer) S1. They negotiate some ESP traffic stream, denoted by an
SPI. This whole thing is encrypted, so the load balancer cannot learn the
SPI value.

 

Now when the first ESP packet is sent from C1 towards the load balancer,
there is not enough information for it to forward the packet to S1,
regardless of its being able to look into the cleartext packet! Only S1 has
the ESP keying material, and if LB forwards the packet elsewhere, the
receiver will not be able to verify its integrity.

 

Regards,

            Yaron

 

  _____  

From: Grewal, Ken [mailto:[e-mail]] 
Sent: Tuesday, October 21, 2008 23:56
To: Yaron Sheffer; Gary Hemminger; Yoav Nir
Cc: [e-mail]
Subject: RE: [IPsec] Identifying encrypted traffic (was: Reauthentication
extension for IKEv2)

 

Some observations below:

 

1.	I agree with Yaron in that if a load balancer needs to 'terminate'
the traffic before applying any rules to distribute the load, then it should
have the keys to do so without any modifications to the current protocol. In
this case, the session setup (via IKE) should have been negotiated with the
load balancer and it is the natural termination point of the IPsec SA. The
load balancer is essentially acting as a VPN gateway for tunnel mode or some
kind of front end proxy to the multiple servers behind it in transport mode.

2.	My understanding of a 'pure' load balancer is that it distributes
traffic streams to different resources available to it and this is typically
based on rules such as source / destination IP protocols, ports (e.g. TCP
ports) and potentially some other information. Furthermore, as some of the
upper layer protocols are stateful (e.g. TCP), it is desirable for the load
balancer to ensure that a higher layer 'session' (e.g. TCP session) is
'pegged' to a resource (server) that has been handling the same session -
this allows efficient state maintenance on a given resource / server,
instead of all resources needing access to that state. Now if the traffic is
protected using IPsec, then the load balancer needs access to upper layer
payload data in the packet in order to apply the aforementioned rules for
load balancing decisions. The charter item on traffic visibility provides
for a clean solution where the load-balancer (as well as other network
monitoring tools) is able to ascertain that the packet if not encrypted and
hence look inside the packet to analyze the protocol / ports to make load
balancing decisions. In this case, IPsec is still being terminated on the
server behind the load balancer, but the load balancer can examine the IPsec
protected packet en-route to ensure it gets to the right server. In essence,
this charter item allows the load balancer (and other network tools) to
continue to function in IPsec environments. 
3.	I agree with Gary on his observations about heuristics as being
complex in HW, undeterministic and the associated parsing rules liable to
change based on new protocols / payloads. 

 

Thanks, 

- Ken

 

  _____  

From: [e-mail] [mailto:[e-mail]] On Behalf Of
Yaron Sheffer
Sent: Tuesday, October 21, 2008 1:37 PM
To: Gary Hemminger; Yoav Nir
Cc: [e-mail]
Subject: Re: [IPsec] Identifying encrypted traffic (was: Reauthentication
extension for IKEv2)

 

OK. But if your load balancer is able to decrypt the traffic (i.e. it has
the credentials or secret keys), then it can do that with today's normal
IKE/IPsec. There is no need in this case to modify the protocol to make it
easier to detect encrypted traffic.

 

Thanks,

            Yaron

 

  _____  

From: Gary Hemminger [mailto:[e-mail]] 
Sent: Tuesday, October 21, 2008 19:02
To: Yaron Sheffer; Yoav Nir
Cc: [e-mail]
Subject: RE: Identifying encrypted traffic (was: [IPsec] Reauthentication
extension for IKEv2)

 

The use case you are thinking about is probably pure IPsec VPN, where an
encrypted stream only lives across the WAN.  But what if you are a load
balancer and the IPsec traffic is end to end?  In this case, you may have a
load balancer that needs to terminate the traffic so it can make the
decision which server to handle the request.  All load balancers today
support SSL termination.  Same thing applies to IPsec traffic.  We cannot
make the decision which server to handle the request, nor can we maintain
persistence without decrypting the traffic.  

 

Gary

 

From: Yaron Sheffer [mailto:[e-mail]] 
Sent: Tuesday, October 21, 2008 6:10 AM
To: Gary Hemminger; Yoav Nir
Cc: [e-mail]
Subject: Identifying encrypted traffic (was: [IPsec] Reauthentication
extension for IKEv2)

 

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 
*	From: Tero Kivinen <kivinen at iki.fi <mailto:[e-mail]>
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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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