Re: [Acme] AD review of draft-ietf-acme-authority-token-05

Roman Danyliw <rdd@cert.org> Thu, 15 April 2021 20:00 UTC

Return-Path: <rdd@cert.org>
X-Original-To: acme@ietfa.amsl.com
Delivered-To: acme@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 4274B3A2CC6 for <acme@ietfa.amsl.com>; Thu, 15 Apr 2021 13:00:57 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.099
X-Spam-Level:
X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cert.org
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OnCaX8s9pxh8 for <acme@ietfa.amsl.com>; Thu, 15 Apr 2021 13:00:52 -0700 (PDT)
Received: from taper.sei.cmu.edu (taper.sei.cmu.edu [147.72.252.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 361F93A2CC4 for <acme@ietf.org>; Thu, 15 Apr 2021 13:00:52 -0700 (PDT)
Received: from korb.sei.cmu.edu (korb.sei.cmu.edu [10.64.21.30]) by taper.sei.cmu.edu (8.14.7/8.14.7) with ESMTP id 13FK0kXM002154; Thu, 15 Apr 2021 16:00:47 -0400
DKIM-Filter: OpenDKIM Filter v2.11.0 taper.sei.cmu.edu 13FK0kXM002154
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cert.org; s=yc2bmwvrj62m; t=1618516847; bh=gra+1Mz6ZscI3nJSkaVkmL0NbWjlbidVwY7e8s7S7bM=; h=From:To:CC:Subject:Date:References:In-Reply-To:From; b=lpYWmglLgUn1rKIo3f27xHI02St4nreY2h1xzisltlYYvsfLdc4fqgZQEb9cRf/YR E2wi56kqg+ORX7ho5THafwJv5PWILakp6Jq9cYeUN72zU6g6GuONnj2pEV2eUmGhH5 NXzLaxw7pD90kGlTmT7R4QJeBT4nFYXt8B6RxloY=
Received: from MURIEL.ad.sei.cmu.edu (muriel.ad.sei.cmu.edu [147.72.252.47]) by korb.sei.cmu.edu (8.14.7/8.14.7) with ESMTP id 13FK0iEr005980; Thu, 15 Apr 2021 16:00:44 -0400
Received: from MORRIS.ad.sei.cmu.edu (147.72.252.46) by MURIEL.ad.sei.cmu.edu (147.72.252.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Thu, 15 Apr 2021 16:00:44 -0400
Received: from MORRIS.ad.sei.cmu.edu ([fe80::555b:9498:552e:d1bb]) by MORRIS.ad.sei.cmu.edu ([fe80::555b:9498:552e:d1bb%21]) with mapi id 15.01.2106.013; Thu, 15 Apr 2021 16:00:44 -0400
From: Roman Danyliw <rdd@cert.org>
To: "Salz, Rich" <rsalz@akamai.com>, Chris Wendt <chris-ietf@chriswendt.net>, Mary Barnes <mary.ietf.barnes@gmail.com>, "Peterson, Jon" <jon.peterson@team.neustar>, "davidhancock.ietf@gmail.com" <davidhancock.ietf@gmail.com>
CC: "acme@ietf.org" <acme@ietf.org>
Thread-Topic: [Acme] AD review of draft-ietf-acme-authority-token-05
Thread-Index: AQHW6ejlOEYeQcveQkikId7N6kJ3Waq2j80A
Date: Thu, 15 Apr 2021 20:00:43 +0000
Message-ID: <5bcc3911ebce4a78a26a98df1575210d@cert.org>
References: <9FF54993-6265-49F5-9663-63A99DB7762B@akamai.com>
In-Reply-To: <9FF54993-6265-49F5-9663-63A99DB7762B@akamai.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.64.203.41]
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
MIME-Version: 1.0
Archived-At: <https://mailarchive.ietf.org/arch/msg/acme/YgKHOq-UjJeutKcDJyc2KMKioLc>
Subject: Re: [Acme] AD review of draft-ietf-acme-authority-token-05
X-BeenThere: acme@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Automated Certificate Management Environment <acme.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/acme>, <mailto:acme-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/acme/>
List-Post: <mailto:acme@ietf.org>
List-Help: <mailto:acme-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/acme>, <mailto:acme-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 15 Apr 2021 20:00:57 -0000

Hi!

I'm checking in on status of this document.  I'd like to batch it with draft-ietf-acme-authority-token-tnauthlist when they go to the IESG.

Thanks,
Roman

> -----Original Message-----
> From: Salz, Rich <rsalz@akamai.com>
> Sent: Wednesday, January 13, 2021 3:16 PM
> To: Roman Danyliw <rdd@cert.org>rg>; Chris Wendt <chris-ietf@chriswendt.net>et>;
> Mary Barnes <mary.ietf.barnes@gmail.com>om>; Peterson, Jon
> <jon.peterson@team.neustar>ar>; davidhancock.ietf@gmail.com
> Cc: acme@ietf.org
> Subject: Re: [Acme] AD review of draft-ietf-acme-authority-token-05
> 
> Authors,
> 
> Have these been addressed?  Soon?
> 
> On 10/14/20, 1:00 PM, "Roman Danyliw" <rdd@cert.org> wrote:
> 
>     Hi!
> 
>     I performed an AD review of draft-ietf-acme-authority-token.  Thanks for
> writing this document in an extensible way (for additional token types).  Below
> is my detailed feedback.
> 
>     ** What is the intended status of this document? The document says
> Informational; the datatracker and the shepherd's report says Proposed
> Standard.  TnAuthlist is PS.  These four places need to be consistent.
> 
>     ** Are there implementations of this document?  The rough history in ACME
> seems to have been PS should have implementation experience.  Is the link to
> STIR decisive here (to make it PS)?
> 
>     ** ID-Nits reported the following issues with references being listed but not
> used:
>       == Unused Reference: 'I-D.ietf-acme-service-provider' is defined on line
>          455, but no explicit reference was found in the text
> 
>       == Unused Reference: 'I-D.ietf-acme-star' is defined on line 460, but no
>          explicit reference was found in the text
> 
>       == Unused Reference: 'RFC7340' is defined on line 477, but no explicit
>          reference was found in the text
> 
>       == Unused Reference: 'RFC8224' is defined on line 494, but no explicit
>          reference was found in the text
> 
>       == Unused Reference: 'RFC8225' is defined on line 500, but no explicit
>          reference was found in the text
> 
>     ** Additionally, on the topic of references, why are [I-D.ietf-acme-authority-
> token-tnauthlist] , [RFC7340] and [RFC8226] normative?
> 
>     -- Section 1. [I-D.ietf-acme-telephone] is an expired draft that doesn't appear
> to be actively advanced.  Given that it primarily to show an example use case, it
> should likely be an informative, not normative, reference.
> 
>     ** In the introductory materials (abstract and/or Section 1), I would have
> benefited from an upfront statement that this document is describing an
> architecture for Authority Tokens, a particular token format, a new protocol for
> retrieving the token, and integration of this token into an ACME challenge.  In
> particular the existence of the new protocol (between the TA and the client)
> was not clear.
> 
>     ** The tkauth-type="atc" type doesn't seem to describe all of the required
> information described by Section 3.1 - 3.3 and Section 9 (Security
> Considerations) as being needed for a token format.  Specifically:
> 
>     (a) Section 3.1.  Per "Definitions of a tkauth-type MUST specify how they
> manage the freshness of authority assignments", how is freshness of authority
> assignment handled in tkauth-type="atc"?
> 
>     (b)  Section 3.2 suggests that tokens need to convey scope.  This scope seems
> to be identifier specific conveyed through the tkvalue.  However, the values of
> tkvalue is out of scope of this document.
> 
>     (c) Section 3.3. suggests "To mitigate this, Authority Tokens contain a binding
> signed by an Authority".  Section 9 says "... all Authority Tokens MUST contain a
> field that identifies to the CA which ACME client requested the token from the
> authority; here that is the fingerprint specified in Section 4)."  However, Section
> 4 says, "For the purposes of the "atc" tkauth-type, the binding "fingerprint" is
> assumed to be a fingerprint of the ACME credential for the account used to
> request the certificate, but the specification of how the binding is generated is
> left to the identifier type profile for the Authority Token."  This seems to
> suggest that defining the binding computation is out scope of this document.
> 
>     For the binding, I'm curious on how is it computed (on what input? How are
> algorithms/keys selected) and when does this need to occur?
> 
>     Minimally, it seems that properties (b) and (c) can only be satisfied with the
> combination of this document and a particular "identifier profile".  Perhaps this
> section is spelling out requirements for both of those collectively?  If so, this
> should be explicitly stated (perhaps in the intro to Section 3, reminded in
> Sections 4 and 9).
> 
>     ** Editorially, decide on where the text will use AT and TA; Authority Token
> and Token Authority; or token and authority.  It would be clear if it was the
> fewest possible version of this key terms.
> 
>     ** Section 3.  Editorial.  The title "Challenges for an Authority Token" might
> be clearer if reworded given that ACME has "challenges" - perhaps s/Challenges
> for an Authority Token/ACME Authority Token Challenge/
> 
>     ** Section 3.  The text notes that authority tokens can be used for ACME
> challenges, but this document doesn't add a new challenge type to the "ACME
> Validation Methods" registry.  Section 6 provides an example using token-
> tnauthlist which seems to suggest a type="tkauth-01", but that isn't specified in
> draft-ietf-acme-token-tnauthlist or this document.
> 
>     I also found it jarring to jump into the discussion of tkauth-type and token
> authority without a bit more context.  I recommend replacing the last
> paragraph as follows:
> 
>     OLD
>     ACME challenges that support Authority Tokens ...
> 
>     NEW
> 
>     The ACME Authority Token Challenge, "tkauth-01", supports different token
> types.  The token type is determined by a new ACME challenge field, tkauth-
> type.  An IANA registry is used to manage the values of tkauth-type, see Section
> 8.*.  Additionally, this challenge also has a new "token-authority" field to
> designate a location where a token can be acquired.
> 
>     ** Section 3.1. Per "The IANA will maintain a registry of tkauth-types under a
> policy of Specification Required", move this text about registry policy to the
> IANA section
> 
>     ** Section 3.1.  Per "... future specifications must indicate how a token
> conveys to the CA the name(s) ...", is there a reason this isn't a normative
> MUST?
> 
>     ** Section 3.1.  Per "The protocols used to request an Authority Token MUST
> convey to the Token Authority the identifier type and value from the ACME
> challenge ...", the language of "from the ACEM challenge" suggests only a
> workflow where the token is requested after engagement with the ACME
> server.  However, Section 3.2 suggests that a client might get the token before
> engaging the ACME server.  Maybe s/from the ACME challenge/from or what
> will be used in the ACME challenge/
> 
>     ** Section 3.2.  Editorial. Somewhere earlier in the text state "Authority
> Token (AT)", as no text currently establishes this acronym.
> 
>     ** Section 3.2.  Editorial. Consistently use "Authority Token", s/to a client a
> Token/to a client an Authority Token/
> 
>     ** Section 3.2.  Per "an Authority Token could attest to all of the resources
> that the client is eligible to receive certificates for", couldn't this leaks
> information to a CA, if that single CA is not responsible for all of the scopes?
> 
>     ** Section 3.2. Editorial. Consistently use "Token Authority" instead of
> "Authority" to make it clear were aren't saying "Certificate Authority"
> 
>     ** Section 3.3.  Editorial. I found it confusing to use "binding" and both a
> noun and a verb:
>     -- "To mitigate this, Authority Tokens contain a binding signed by an
> Authority ..."
>     -- "Binding an Authority Token to a particular ACME account ..."
> 
>     ** Section 4.  Editorial.
> 
>     OLD
>     This draft registers a tkauth-type of "atc", for the Authority Token
>        Challenge.   Here the "atc" tkauth-type signifies a standard JWT token
>        [RFC7519] using a JWS-defined signature string [RFC7515]. This may
>        be used for any number of different identifier types given in ACME
>        challenges.  The "atc" element (defined below) lists the identifier
>        type used by tokens based on ATC .  The use of "atc" is restricted to
>        JWTs, if non-JWT tokens were desired for ACME challenges, a different
>        tkauth-type should be defined for them.
> 
>     NEW
>     This draft specifies a tkauth-type of "atc" which is a standard JWT token
> [RFC7519] using a JWS-defined signature string [RFC7115].  The "atc" tkauth-
> type MAY be used for any number of different ACME identifier types in the
> ACME challenge.  A new JWT claim, "atc", is defined below and lists the
> identifier type used in this Authority Token.  The "atc" tkauth-type is restricted
> to the JWTs; if a non-JWT token format is desired for the ACME Authority
> Token Challenge, a different tkauth-type should be specified and registered in
> the "xxx" registry defined in Section 8.*
> 
>     ** Section 4.  Editorial. ATC is used but never explicitly defined as being
> "Authority Token Challenge (ATC)".
> 
>     ** Section 4.  What would be the circumstance where the x5u/iss would not
> equal the token-authority?
> 
>     ** Section 4.  Why is "The JWT payload must also contain a ...", not a
> normative MUST?
> 
>     ** Section 4.  Should the values of tktype be constrained to the IANA "ACME
> Identifier Types" registry?
> 
>     ** Section 4.  This text should explicitly say that "tkvalue" semantics are
> outside the scope of this document.
> 
>     ** Section 4. s/"atc" element/"atc" claim/
> 
>     ** Section 4.  The example in this section is missing the full
> payload/protected /signature structure to show the actual binding provided by
> the server
> 
>     ** Section 5.  This token acquisition protocol seems underspecified:
>     -- How does the client authenticate/do authorization with the HTTPS server?
> 
>     -- Is there any semantics to the resource locator to make for an
> interoperable/discoverable URI?
> 
>     -- Does the client get to request a scope?
> 
>     ** Section 5. Editorial. s/a Authority Token/an Authority Token/
> 
>     ** Section 5.1.  It might be useful to show a full server response example
> given a particular client request
> 
>     ** Section 5.1
>     After an HTTPS-level challenge to verify the identity of the client
>        and subsequently making an authorization decision , in the success
>        case the Token Authority returns a 200 OK with a body of type
>        "application/json"  containing the Authority Token.
> 
>     -- What is an "HTTPS-level challenge"?
> 
>     -- It seems like a few words are missing describing the server's behavior to
> describe what happens between client sending the JSON "atc" blob and
> returning an authority token?  Should there be text about signing? The server
> validating the scope in a some identifier specific way?
> 
>     -- How is error handling managed with the HTTP error code?  The TnAuthlist
> draft actually specifies this behavior more that this base document.
> 
>     -- Section 5.  Shouldn't a successful response from a Token Authority return a
> body of type "application/jwt" if an "authority token" is being returned per
> Section 4?
> 
>     ** Section 6.  This section seems underspecified with only the use of an
> example.  It provides no normative text on using the authority token in the
> ACME challenge.  For example, what type should be used (tkauth-01)?  What is
> the cardinality of tk-auth-type, token-authority, token?
> 
>     ** Section 8.  This text registers "atc" as an ACME identifier.  When and how
> is that used?  I thought that identifier profiles specified an identifier and that
> the atc what the challenge/verification type.
> 
>     ** Section 8.  Is there a reason that the "atc" claim from Section 4 not being
> registered in the "JSON Web Token Claims" registry?
> 
>     ** Section 8.  Per the registry of "token types", there don't seem to be
> enough details here:
>     -- Is the intent for the registry to be called (in lower case) "token types".
> Shouldn't it be something like "ACME Authority Token Challenge Types"?
> 
>     -- What columns are in that registry?  Please be explicit, if it is Label and
> Reference.
> 
>     Regards,
>     Roman
> 
>     _______________________________________________
>     Acme mailing list
>     Acme@ietf.org
>     https://urldefense.proofpoint.com/v2/url?u=https-
> 3A__www.ietf.org_mailman_listinfo_acme&d=DwICAg&c=96ZbZZcaMF4w0F4j
> pN6LZg&r=4LM0GbR0h9Fvx86FtsKI-w&m=KKMUAt5wm8Vy2_-
> YnBnWkWr_4yD6G9lTMhYZiFQ2J_s&s=K5vl0NrG5LqkL6Qzy-
> 8cyQCG1RMqIQwrvCf0jPOBA7w&e=