On Wed, 17 Jun 2020, Michael Richardson wrote:
Paul Wouters <p...@nohats.ca> wrote:
> Technically, your profile could say to "request transport mode, and
> refuse the connection if the other end is unwilling to use transport
> mode", but that I would argue that would constitute a protocol
> modification which is not what a profile should do.
How is this different than:
"request authentication with a RSA certificate known to this CA,
and refuse the connection if the other end is unwilling to use an appropriate
key"
The RFC states:
The USE_TRANSPORT_MODE notification MAY be included in a request
message that also includes an SA payload requesting a Child SA. It
requests that the Child SA use transport mode rather than tunnel mode
for the SA created. If the request is accepted, the response MUST
also include a notification of type USE_TRANSPORT_MODE. If the
responder declines the request, the Child SA will be established in
tunnel mode. If this is unacceptable to the initiator, the initiator
MUST delete the SA.
But note that the responder has already installed the IPsec SA in tunnel
mode. So if the initiator finds that unacceptable, it must send the
delete. During all this time, connectivity between the nodes will be
blocked. The intention here is that transport mode is optional and
should not be mandated by other protocols. Otherwise, the IKEv1
style negoation of transport OR tunnel mode would have been kept.
So I would recommend to follow the intention of RFC 7296 and not make
up your own restrictions.
Whether a certain CA is acceptable is a configuration matter. There is
no text in the RFC that states which certificates you must trust.
Paul
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