On 06/14/12 13:39, Yoav Nir wrote:
Hi Yaron
Responses are inline.
Yoav
On Jun 14, 2012, at 1:40 AM, Yaron Sheffer wrote:
Hi Yoav,
thank you for the new draft. A few comments:
- Please mention the question of IKE keepalive messages ("liveness
check"). Do you expect these messages to each be on a new connection? Or
to preserve one long-lived one?
I think section 2.1 makes it clear that the TCP connections should be
short-lived. Specifically, I would not send liveness checks, which are very
short requests and responses over TCP. I would use UDP exclusively for those.
This section is a little unclear to me. Is the idea that the initiator
of the exchange(s) may send up to <IKEv2 request window> requests, wait
for the responses to arrive and then must close the connection? Or can
the initiator perform as many exchanges as it likes over one TCP
connection, so long as "knows" that it has requests it wants to send?
If this connection closing requirement is designed to interact with the
IKEv2 request window, please make it more clear.
- The draft kind of skirts the question, and I would prefer to be clear:
we are standardizing new behavior for IKEv2, not for IKEv1.
I think it's suitable for both versions. If this gets adopted by the working
group, and people object to standardizing new stuff for IKEv1, I can remove all
mention of it.
<hat type="vendor">
Our present implementation works with IKEv1, and has done so for over 10 years.
I could submit an Informational describing how Check Point's implementation
does IKEv1 over TCP. But just as new ciphers would apply to both versions, I
think this transport can also be independent of version.
</hat>
I'd rather settle on the best possible solution for IKEv2 without
worrying about making sure it works for IKEv1 as well.
- In the security considerations, we should mention that (under certain
assumptions), it is easier for an off-path attacker to reset a TCP
connection than a UDP "connection".
Yes, TCP presents some DoS opportunities not available for UDP. I'll look for
an RFC that talks about this. And if there isn't one, there d**n well should be.
I suggest adding a MUST that a lost TCP connection or truncated packet
from the peer should never constitute a failed exchange (which in many
cases, closes the SA).
- There are obvious advantages to negotiating this capability: you don't
have clients sending SYNs that will get rejected by firewalls/endpoints.
Especially in IKEv2 where the heavy stuff only happens on message #3.
SYN/SYN-ACK or SYN/RST is a kind of negotiation. Besides, sending a notification over UDP
that says "I support TCP" doesn't help much, because it cannot vouch for the
path allowing TCP port 500. I wonder if there's an actual use case for increasing the
length field of payloads, so that IKE can support larger payloads when working over TCP.
One use for this would be to send large CRLs in a CERT payload.
I agree with the concerns Yaron has raised here. I would much prefer
that this be negotiated via notifications during the SA_INIT exchange.
I see a number of benefits:
1. The TCP listening port could be explicitly exchanged (as data in the
notification), rather than always assumed 500. This would allow
operation in parallel with any legacy/proprietary use of that server
port, and in general more deployment flexibility.
2. Since INIT always happens over UDP, as responder, I can immediately
close any TCP connection that doesn't present an IKE header with an SPI
I recognize.
3. It fits better with the IKEv2 design of never assuming the peer has
capabilities beyond the base requirements without a notification/vendor
payload indicating otherwise.
- 2.3: disallowing retransmissions implies a change on both transmitter
and receiver, and I think this is unnecessary. You can change the IKE
timeouts on the sender to achieve the same behavior, even if rarely an
odd retransmission does slip through.
I guess. There is a MUST in section 2.4 for keeping retransmission detection,
so when implementing the transmitter, you can do either. It doesn't make sense
to retransmit at the application level when TCP does it for you.
Do we want to specify (maybe as a SHOULD) a fairly rapid fallback to UDP
for retransmissions? This would help avoid protocol failures when the
UDP path is functional but TCP is not. Messages ids should filter out
any duplicates that get through.
-John
Thanks,
Yaron
On 06/14/2012 12:59 AM, Yoav Nir wrote:
Hi
I've submitted this draft as a possible solution to the problem
discussed in the thread about fragmentation causing IKE to fail.
Comments are welcome.
Yoav
Begin forwarded message:
*From: *"[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
*Subject: **New Version Notification for draft-nir-ipsecme-ike-tcp-00.txt*
*Date: *June 13, 2012 7:13:55 PM GMT+03:00
*To: *Yoav Nir<[email protected]<mailto:[email protected]>>
A new version of I-D, draft-nir-ipsecme-ike-tcp-00.txt
has been successfully submitted by Yoav Nir and posted to the
IETF repository.
Filename:draft-nir-ipsecme-ike-tcp
Revision:00
Title:A TCP transport for the Internet Key Exchange
Creation date:2012-06-13
WG ID:Individual Submission
Number of pages: 7
URL: http://www.ietf.org/internet-drafts/draft-nir-ipsecme-ike-tcp-00.txt
Status: http://datatracker.ietf.org/doc/draft-nir-ipsecme-ike-tcp
Htmlized: http://tools.ietf.org/html/draft-nir-ipsecme-ike-tcp-00
Abstract:
This document describes using TCP for IKE messages. This facilitates
the transport of large messages over paths where fragments are
dropped.
The IETF Secretariat
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