I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
Please resolve these comments along with any other Last Call comments
you may receive.
Document: draft-ietf-dane-ops-12.txt
Reviewer: Elwyn Davies
Review Date: 2015/06/19
IETF LC End Date: 2015/06/24
IESG Telechat date: (if known) -
Summary: Almost ready. There are a couple of minor issues, and I think
the authors need to reassess whether all the cases where RFC 2119
keywoDANE and rds are actually protocol requirements as opposed to
operation best practice recommendations. Caveat: I am not a DNSSEC
expert and I can't really be sure about the interactions of DNSSEC and
DANE.
Major issues:
None
Minor issues:
s3: I am not a security expert, but I suspect you may get some pushback
on not making TLS 1.2 mandatory.
Also I wonder whether SSL 2.0 and SSL 3.0 should be explicitly ruled
out? The SECDIR review may say something here.
s3:
TLS clients and servers using DANE SHOULD support the
"Server Name Indication" (SNI) extension of TLS.
Under what circumstances would it be reasonable for a DANE/TLSA server
not to support SNI? Maybe I could see that a single domain server
could do without it. I think this needs to be spelt out - earlier text
seems to indicate that SNI support was pretty much mandatory.... Ah!
Later I see that s5.1 gives a case where SNI is not mandatory - a
forward pointer would help.
s4.1: I am not clear that this section adds any value to the discussion
in s4. Why should the protocol designer be less inclined to use PKIX-xx
rather than DANE-xx when the protocol supports an OS mode as opposed to
just fully authenticated or fully authenticated plus cleartext modes?
Is there some positive advantage to the DANE-xx authentication failing
when it comes to deciding whether to proceed with OS? Otherwise it
seems to me that this section just says that you can use DANE with an OS
protocol and the s4 recommendation applies. It is possible that I do
not understand what is being said here.
Nits/editorial comments:
=====================
General: The use of 'we' in RFCs is generally deprecated. There are
about 20 examples in the draft that need remedying including:
s1, last para: s/In Section 12, we summarize/Section 12 summarizes/
s1.1, definition of Customer Domain:
OLD:
We will refer to
the domain name used to locate the service (prior to any
redirection) as the "Customer Domain".
NEW:
The domain name used to locate the service (prior to any
redirection) will be referred to as the "Customer Domain".
END
s1.1, definition of TLSA parameters: s/in fourth/in the fourth/, s/we
need/it is necessary/,
s/we will call the first three fields/the first three fields will be
called/
s2, para 5:
OLD:
We may think of TLSA Certificate Usage values 0 through 3 as a
combination of two one-bit flags.
NEW:
The TLSA Certificate Usage values 0 through 3 can be interpreted as a
combination of two one-bit flags.
END
s5.1, para 1: s/We also extend [RFC6698]/[RFC6698] is also extended/
s6, next to last para: s/we describe an approach/an approach is described/
s8, para 1:
OLD:
We describe a TLSA
record update algorithm that ensures this requirement is met.
NEW:
This document describes a TLSA
record update algorithm that ensures this requirement is met.
END
s9, para 1:
OLD:
We specify such a protocol below.
NEW:
Such a protocol is specified below.
END
s12: Several instances of "we"...
- Bullets 1 - 3: s/we update [RFC6698]/[RFC6698] is updated/
- Bullet 4: s/we explain/explains/
- Bullet 4: s/With usage PKIX-TA(0) we note that/Note that with the
usage of PKIX-TA(0)/, s/processes/process/
- Bullets 5 and 8: s/In Section x, we recommend/Section x recommends/
- Bullets 6 and 7: s/In Section x we specify/Section x specifies/
----------------
General: I am dubious about the usage of RFC 2119 keywords for
constraints that are recommendations for operational usage rather than
protocol on the wire constraints. In each case, I think the question
you have to consider is "If the client
or server violates the constraint could the box at the other end of the
wire tell that the constraint had been violated?" If the far end can't
tell then RFC 2119 language is probably inappropriate. AFAICS in at
least some of the instances this needs to be rechecked - I can't be sure
in several of the cases. Examples include:
s4, next to last and last paras: I think the "MAY" in the last para
should be "may" - if not probably the "recommends" in the previous para
should be RECOMMENDS.
s4.1: Again this is an operational suggestion, so s/SHOULD NOT/should
not/ as the implementation can't really tell it is wrongly used.
s5.1, para 6: s/SHOULD/should/ - operational practice rather than
protocol specification again.
s5.1, paras 7 and 8: Probably s/SHOULD NOT/should not/ - I think (but
am not certain in these cases) that these are again operational practice
rather than something that is checked in the protocol.
s5.2, paras 1 and 4: Again the usage of RFC 2118 keywords needs to be
checked.
----------------------------
Other editorial nits:
s1: Probably worth repeating that TLSA is not an acronym.
s1: Perhaps worth repeating the expansion of DANE here.
s1, para 1: Need to expand DNSSEC on first use.
s1: Need to expand TLS on first use (currently it happens later).
s1.1, definition of SNI: suggest s/(i.e., "secure virtual
hosting")./(i.e., provide "secure virtual hosting")./
s2, next to last para: ASN.1 DER needs a reference - to X.690 (as in
RFC 6698).
s4.2: I would be inclined to emphasize that RFC 6962 is experimental so
that this is not an issue that would arise in current operational
practice - and maybe that a standards track version of CT would be
better integrated. Maybe update para 1:
OLD:
Certificate Transparency (CT) [RFC6962
<https://tools.ietf.org/html/rfc6962>] defines an approach to
mitigate the risk of rogue or compromised public CAs issuing
unauthorized certificates. This section clarifies the interaction of
CT and DANE.
NEW:
Certificate Transparency (CT) [RFC6962] defines an experimental approach
that could be used to mitigate the risk of rogue or compromised public
CAs issuing unauthorized certificates. This section clarifies the
interaction of the experimental CT and DANE. This interaction may need
to be revisited in the event that a standards track version of CT is
developed in future.
END
s4.3: There appears to be a conflict between the title and second
sentences vs. the third sentence:
When transitioning between PKIX-TA/PKIX-EE and
DANE-TA/DANE-EE, clients begin to enable support for the new
certificate usage values.
and
If the new preferred certificate usages
are PKIX-TA/EE this requires installing and managing the appropriate
set of CA trust anchors.
I don't see why 'new' appears in the third sentence if the scenario is
transitioning away from PKIX-TA/PKIX-EE.
Am I confused?
s5, title: s/Certificate-Usage/Certificate Usage/ for consistency with
the rest of the section.
s5.1, para 4: The term "server's primary certificate" does not appear to
be defined. I think I can probably guess (something associated with the
physical host rather than any virtual hosts?) but defining it explicitly
would be good.
s8.3, para 1: s/each combinations/each combination/
s9, para 3: Expand acronym "MTA".
s9, last para: If it is decided that this is a protocol requirement:
s/SHOULD not/SHOULD NOT/
s11, para 2: Expand acronym "gTLD".
s17.2: I think RFC7250 is probably normative.
s17.2: I can't decide whether I would like RFC6781 to be normative. It
would of course be a downref. This is always going to be a problem
since the draft is combining operational considerations and protocol
updates. The one explicit reference indicates you have to know
something about how to run DNSSEC to run DANE - in practice I think you
have to know a great deal about how to run DNSSEC if you are going to
run DANE so I would be inclined to make this normative (and maybe refer
to it in the introduction as well).
_______________________________________________
Gen-art mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/gen-art
