Re: [IPsec] draft-pauly-ipsecme-split-dns

[Nico Williams <[e-mail]>]

On Tue, Jun 19, 2018 at 10:13:47AM -0700, Eric Rescorla wrote:
> I don't think that going point-by-point is getting us very far, so I'm
> going to try to restate what i think the situation is, from the top.
> 
> 1. In the current design, many clients (those whose enterprises have any
> significant number of domains) are just going to have to accept whatever
> domains the VPN server claims should be treated as internal, and to accept
> the trust anchors the VPN server claims

The I-D should say that clients MUST allow local configuration of what
domains to accept trust anchors for, and SHOULD allow local policy to
list . as a domain for which to accept trust anchors.

This local configuration should be per-SG.

> 2. Because the current design also allows those trust anchors to sign TLSA
> records, any TLS client which accepts those TLSA records is subject to MITM
> by the VPN server

And SSHFP.  And anything else that might be security-relevent (all of
DNS, really).

This definitely merits a Security Considerations note even if this
property were actually the point of this protocol.

> 3. Even if enterprise doesn't intend to run a MITM proxy, this means that
> any compromise of the VPN server automatically makes it an MITM proxy for
> the Internet as a whole, because the person who compromises it can simply
> reconfigure it to advertise any domain of its choice as internal, as well
> as the corresponding keys and TLSA records.

Sure, but it's not like clients will be choosing to connect to any VPN
servers.  Generally the client must already have a trust anchor for the
SG to begin with.  Painting this as a security threat to the entire
Internet is going a bit too far.

> What, if any, of the above do you disagree with?

(3).

Nico
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