Hi, Alexey,
Gen-ART reviewers ADORE editors who respond quickly, because there's a
chance the Gen-ART reviewer can remember what the review was trying to say!
Thanks for quick feedback.
I'm fine with most of the resolutions you proposed, so I'm dropping
everything that I agree with (except that a couple of your resolutions are
so much better than my proposed text that I wanted to say that explicitly
:-).
I have a couple of notes below. This review was done as input to Last Call,
so please handle as you would handle any other Last Call comments (talk to
your document shepherd).
Thanks,
Spencer
From: "Alexey Melnikov" <[EMAIL PROTECTED]>
Spencer Dawkins wrote:
Document: draft-ietf-lemonade-rfc2192bis-08
Reviewer: Spencer Dawkins
Review Date: 2007-08-02
IETF LC End Date: 2007-06-28 (yes, this review is late).
IESG Telechat date: 2007-08-23
Abstract
This document obsoletes RFC 2192. It also updates RFC 4467.
Together with update to RFC 4467 they will obsolete RFC 4467.
Spencer: Pronoun problem here - what is "they"? I'm reading this as (1)
this document obsoletes RFC 2192, (2) this document also updates RFC
4467, but (3) there is ALSO another update to 4467 (let's call it
4467bis), and (4) 2192bis and 4467bis, taken together, will obsolete
4467.
Correct. I've changed "they" to "it".
If that's not what the text actually means, I can't understand this
paragraph well enough to suggest text.
I guess what I'm trying to undestand is (a) will this document and the
apparent 4467bis be advanced together?
No, 4467bis is not written yet ;-)
so that on one fine day, 2192bis and 4467bis are published as RFCs, and
4467 is marked as obsoleted, or (b) are you expecting that 4467 will be
marked as updated by 2192bis OR by 4467bis until both are published as
RFCs, and then 4467 will be marked as obsoleted
Yes, obsoleted by both.
(by both? by either? mumble)?
I am thinking that it might be better to remove the sentence "Together
with update to RFC 4467 they will obsolete RFC 4467", as it is trying to
put a requirement on a future document (4467bis).
Agree with this resolution (since the lemonade/imap community might change
plans before the future document is written, or may simply not write the
second document, the RFC Editor will be a lot happier with your proposed
resolution, I bet).
1. Conventions used in this document
Note that the syntax shown in sections 2-6 is informal. The
authoritative formal syntax for IMAP URLs is defined in section 11.
If there are any differences between syntax shown in sections 2-6
and section 11, then the syntax shown in section 11 must be treated
as authoritative.
Spencer: Please help me here. This text says that SYNTAX in sections 2-6
is informal (which I'm probably misinterpreting as "informative", but
these sections also contain 2119 language, which in a Proposed Standard
would be normative.
You might be reading too much into my text ;-)
This paragraph is trying to say:
1). Sections 2-6 might not be using ABNF
2). In case there are any differences (or errors) between syntax in
sections 2-6 and section 11, then section 11 contains the correct syntax.
How about changing:
Note that the syntax shown in sections 2-6 is informal. The
authoritative formal syntax for IMAP URLs is defined in section 11.
to:
Note that the syntax shown in sections 2-6 is informal, the
authoritative formal syntax for IMAP URLs is defined in section 11.
?
Can we do this? (and should we do this?) Is it worth saying "2119
requirements in sections 2-6 are, of course, normative" in this section?
I guess this can be added, but I thought it was obvious.
Obvious is relative, of course... :-) Based on our exchange, I'm suggesting
"Note that the ABNF syntax shown in section 11 is normative. Examples in
sections 2-6 may use a less formal syntax that does not match the normative
ABNF shown in section 11, if the result helps the reader to understand the
point being made in an example. Non-syntax requirements included in sections
2-6 are, of course, normative."
2. Introduction
The IMAP URL follows the common Internet scheme syntax as defined
in [URI-GEN]. If :<port> is omitted, the port defaults to 143.
Spencer (nit): would it be appropriate to expand this to something like
"defaults to 143 (as assigned by IANA)"?
I've added "(as defined in Section 2.1 of [IMAP4])" instead, I think this
is slightly clearer.
I'd say "quite a bit clearer". Thanks for the improvement to my suggestion!
3.3. Limitations of enc-user
An obvious limitation of using the same field for both purposes is
that the URL can be resolved only by the mailbox owner. In order
to avoid this restrictions, implementations should use globally
unique mailbox names (see Section 3.1) whenever possible (*).
(*) There is currently no general way in IMAP of learning a glob-
ally unique name for a mailbox. However by looking at the NAMESPACE
[NAMESPACE] command result it is possible to determine if a mailbox
name is globally unique or not.
Spencer (nit): I'm not used to seeing "footnotes" in Internet Drafrs...
I think it is clearer this way.
Well, yeah, I agree. My point is that
ftp://ftp.rfc-editor.org/in-notes/rfc-editor/instructions2authors.txt says
(8) Footnotes
Do not use footnotes. If such notes are necessary, put them
at the end of a section, or at the end of the document.
So my suggestion is to discuss this with the RFC Editor now ("and not during
AUTH-48, which might be the first time you realize that the RFC Editor has
proposed changed text"), and figure out what is clearer AND consistent with
about 5000 previously-proposed RFCs ;-)
5. Lists of messages
they MUST be percent-encoded as described in [URI-GEN].
The "?<enc-search>" field is optional. If it is not present, the
entire content of the mailbox SHOULD be presented by the program
interpreting the URL. If it is present, it SHOULD be used as the
arguments following an IMAP4 SEARCH command with unsafe characters
such as " " (which are likely to be present in the <enc-search>)
percent-encoded as described in [URI-GEN]. Note that quoted
Spencer: If these SHOULDs are in the previous version of this document
with no explanation, that's OK, but if there are well-understood and
agreed reasons for NOT doing what the SHOULDs require, it would be nice
to point them out here.
The client may instead open the mailbox, download all messages and perform
the search itself. Thus the SHOULD.
Ah. This isn't a 2119 SHOULD. If I understand correctly, the intention is to
say
The "?<enc-search>" field is optional. If it is not present, the
program interpreting the URL will present the entire content of the
mailbox.
If the "?<enc-search>" field is present, the program interpreting the
URL should use the contents of this field as arguments following an
IMAP4 SEARCH command. These arguments are likely to contain unsafe
characters such as " ". If unsafe characters are present, they MUST be
percent-encoded as described in [URI-GEN].
Is this what the text is intended to say?
I am not sure I want to go into such level of details in the document ;-).
Besides the list of things that clients SHOULD NOT do might be a bit long.
I understand completely...
(There are quite a few SHOULDs without listed exceptions, so please
consider this a fairly general comment).
So, based on the previous point, I'm thinking the review comment should be
"please make sure that your SHOULDs really are 2119 SHOULDs:
3. SHOULD This word, or the adjective "RECOMMENDED", mean that there
may exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood and
carefully weighed before choosing a different course.
and, to be specific, a SHOULD would be a MUST in most circumstances.
6.1.1.2. Mailbox Access Key
The mailbox access key is a random string with at least 128 bits of
entropy. It is generated by software (not by the human user), and
MUST be unpredictable.
Spencer: is "MUST be unpredictable" sufficiently defined? And I'm not
sure this is a 2119 MUST - it would be a bad idea to generate keys by
adding one to the previous key,
It is a MUST on server implementations due to a security consideration.
Ah, perfect. Then the text could be something like
Servers MUST generate the mailbox access key cryptographically,
with at least 128 bits of entropy.
Is this what the text is intended to say?
6.1.2. URLAUTH extensions to IMAP URL
The "authuser" <access> identifier indicates that use of this URL
is limited to IMAP sessions which are logged in as an authorized
user (that is, have authorization identity as an authorized user)
of that IMAP server. Use of this URL is prohibited to anonymous
IMAP sessions.
Spencer (nit): this paragraph reads oddly, since it says "is limited to
authorized user" AND "is prohibited to anonymous users". I would have
expected one or the other (since the two categories are mutually
exclusive and collectively exhaustive, aren't they?)
Yes, but one can misunderstand AUTHENTICATE ANONYMOUS sessions as sessions
logged in as an authorized user. So the second sentence clarifies that
this is not the case.
Probably so, for people who know more about IMAP4 than I do. If people like
me will be reading this specification, perhaps your clarifying text should
be included in the draft? Something like
The "authuser" <access> identifier indicates that use of this URL
is limited to IMAP sessions which are logged in as an authorized
user of that IMAP server, not as AUTHORIZED ANONYMOUS. Use of this
URL is prohibited to anonymous IMAP sessions.
Just curious - is it obvious what the IMAP4 server does when an AUTHORIZED
ANONYMOUS client provides this URL? A pointer to an IMAP4 specification
would be nice, if you're hoping for consistent server behavior...
7.2. relative-path References
A relative reference that does not begin with a slash character is
termed a relative-path reference [URI-GEN]. Implementations SHOULD
NOT generate or accept relative-path IMAP references.
Spencer: it might be nice to say why this deprecated concept is
important - perhaps ", but relative-path IMAP references are still in use
in older IMAP implementations" or something similar?
Actually I am not sure that relative-path IMAP references are used much,
they were found to be quite problematic during the Lemonade interop last
year.
The text is here because URI-GEN allows for relative-path references.
Ah. I thought all the unintended consequences from protocol reuse were in
the RAI area :-) Perhaps this could be stated more clearly? Something like
A relative reference that does not begin with a slash character is
termed a relative-path reference [URI-GEN]. Although [URI-GEN] allows
relative-path IMAP references, they were found to be problematic during
2006
interoperability testing. Clients conforming to this specification
MUST NOT generate relative-path IMAP4 references. Servers conforming to
this
specification MUST NOT accept relative-path IMAP references.
If you/your document shepherd is more comfortable with SHOULD NOT for the
server behavior, that would still be an improvement, but you probably have
the obligation to say what the server SHOULD do with a relative-path IMAP
reference in that case.
10.1. Security Consideration specific to URLAUTH authorized URL
The decision to use the "anonymous" access identifier should be
made with extreme caution. An "anonymous" access identifier can be
used by anyone; and therefore use of this access identifier should
be limited to content which may be disclosed to anyone. Many IMAP
servers do not permit anonymous access; in the case of such servers
the "anonymous" access identifer is equivalent to "authuser", but
this MUST NOT be relied upon.
Spencer: OK, light-years beyond my expertise here, but are you telling me
that there's no way for a client to discover the server's "no anonymous
access" policy?
There is a way for a client to discover if the server supports anonymous
authentication (the server will refuse AUTHENTICATE ANONYMOUS if it
doesn't).
There is also a way for the client to discover if anonymous access
identifier is supported: the client can try to sign an URL with the
anonymous access identifier and see if it gets refusal from the server.
If so, it might be nice to add this as a reason *why* "this MUST NOT be
relied upon".
The point of this MUST is to make sure that implementors don't treat them
as the same, as there are security considerations associated with them (as
discussed in the quoted paragraph). I would welcome any suggestions about
how to make this clearer.
I'm out of my depth here, but it seems that you're saying
- they aren't the same, but
- some implementors treat them the same, so
- other implementers can't rely on them being treated differently, even
though they are different.
I would prefer adding text that requires conformant implementations to treat
them differently ("correctly") - the current text seems to place the burden
of dealing with nonconforming implementations on conforming implementations,
and that's a bigger burden than "conservative in what you send, liberal in
what you accept"....
Thanks,
Spencer
_______________________________________________
Gen-art mailing list
[email protected]
https://www1.ietf.org/mailman/listinfo/gen-art
