Re: Eric Rescorla's Discuss on draft-ietf-httpbis-expect-ct-07: (with DISCUSS and COMMENT)
Eric Rescorla <ekr@rtfm.com> Wed, 21 November 2018 22:20 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 21 Nov 2018 14:16:51 -0800
Message-ID: <CABcZeBMhoB7MjE0Tpww66e8CD0nqMdswyjzSng19sdtQ6QjOfw@mail.gmail.com>
To: Emily Stark <estark@google.com>
Cc: IESG <iesg@ietf.org>, httpbis-chairs@ietf.org, Mark Nottingham <mnot@mnot.net>, draft-ietf-httpbis-expect-ct@ietf.org, HTTP Working Group <ietf-http-wg@w3.org>
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Subject: Re: Eric Rescorla's Discuss on draft-ietf-httpbis-expect-ct-07: (with DISCUSS and COMMENT)
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No problem. Just wanted to make sure I wasn't the hold-up. -Ekr On Wed, Nov 21, 2018 at 2:04 PM Emily Stark <estark@google.com> wrote: > Sorry for the delay. I'm on maternity leave but hope to have these > addressed in the next couple weeks. > > On Wed, Nov 21, 2018 at 1:52 PM Eric Rescorla <ekr@rtfm.com> wrote: > >> Following up, I don't see any response to these comments. >> >> -Ekr >> >> >> On Thu, Sep 13, 2018 at 7:22 AM Eric Rescorla <ekr@rtfm.com> wrote: >> >>> I have one other non-blocking comment: Why is this document >>> Experimental? People are already deploying CT without this. It seems like >>> PS would make more sense or Informational. >>> >>> Alexey, I leave it to you. >>> -Ekr >>> >>> >>> On Wed, Sep 12, 2018 at 4:12 PM, Eric Rescorla <ekr@rtfm.com> wrote: >>> >>>> Eric Rescorla has entered the following ballot position for >>>> draft-ietf-httpbis-expect-ct-07: Discuss >>>> >>>> When responding, please keep the subject line intact and reply to all >>>> email addresses included in the To and CC lines. (Feel free to cut this >>>> introductory paragraph, however.) >>>> >>>> >>>> Please refer to >>>> https://www.ietf.org/iesg/statement/discuss-criteria.html >>>> for more information about IESG DISCUSS and COMMENT positions. >>>> >>>> >>>> The document, along with other ballot positions, can be found here: >>>> https://datatracker.ietf.org/doc/draft-ietf-httpbis-expect-ct/ >>>> >>>> >>>> >>>> ---------------------------------------------------------------------- >>>> DISCUSS: >>>> ---------------------------------------------------------------------- >>>> >>>> Rich version of this review at: >>>> https://mozphab-ietf.devsvcdev.mozaws.net/D4579 >>>> >>>> >>>> This generally seems like a sound mechanism, but I believe there are >>>> some points here that are sufficiently unclear they might create >>>> interop problems,s o I am balloting DISCUSS. >>>> >>>> Most importantly, this document just says you support CT, but that >>>> creates a potential interop problem if say 6962-tris had a different >>>> way of delivering CT information or a different syntax. I'm not saying >>>> you need a version here, but you need to indicate that it's not >>>> forward-looking. >>>> >>>> Also, see below. >>>> >>>> DETAIL >>>> S 2.4. >>>> > beginning an HTTP conversation over the TLS channel. >>>> > >>>> > If a connection to a Known Expect-CT Host violates the UA's CT >>>> policy >>>> > (i.e., the connection is not CT-qualified), and if the Known >>>> Expect- >>>> > CT Host's Expect-CT metadata indicates an "enforce" >>>> configuration, >>>> > the UA MUST treat the CT compliance failure as an error. >>>> >>>> Is this supposed to be a hard failure, as with HSTS. If not, how does >>>> it interact with HSTS's hard failure reqs. >>>> >>>> >>>> S 3.1. >>>> > (This may differ from the value of the >>>> "served-certificate-chain" >>>> > key.) The value is provided as an array of strings, which >>>> MUST >>>> > appear in the order matching the chain that the UA validated; >>>> each >>>> > string in the array is the Privacy-Enhanced Mail (PEM) >>>> > representation of each X.509 certificate as described in >>>> > [RFC7468]. >>>> >>>> What happens if you try to construct multiple paths? >>>> >>>> >>>> S 3.1. >>>> > does not have or does not trust the public key of the log >>>> from >>>> > which the SCT was issued), "valid" (indicating that the UA >>>> > successfully validated the SCT as described in Section 5.2 >>>> of >>>> > [RFC6962] or Section 8.2.3 of >>>> [I-D.ietf-trans-rfc6962-bis]), or >>>> > "invalid" (indicating that the SCT validation failed >>>> because >>>> > of, e.g., a bad signature). >>>> >>>> Is "invalid" anything other than the specific cases listed above? >>>> >>>> >>>> ---------------------------------------------------------------------- >>>> COMMENT: >>>> ---------------------------------------------------------------------- >>>> >>>> >>>> > allows web host operators to instruct user agents to expect valid >>>> > Signed Certificate Timestamps (SCTs) to be served on connections >>>> to >>>> > these hosts. Expect-CT allows web host operators to discover >>>> > misconfigurations in their Certificate Transparency deployments >>>> and >>>> > ensure that misissued certificates accepted by UAs are >>>> discoverable >>>> > in Certificate Transparency logs. >>>> >>>> I don't believe that it does this. Consider a client which simply did >>>> not support CT, then it would (a) accept a misissued certificate that >>>> (b) was not discoverable >>>> >>>> >>>> S 2.1.1. >>>> > >>>> > Figure 2: Syntax of the report-uri directive value >>>> > >>>> > "absolute-URI" is defined in Section 4.3 of [RFC3986]. >>>> > >>>> > Hosts may set "report-uri"s that use HTTP or HTTPS. If the >>>> scheme in >>>> >>>> Why are you allowing HTTP? >>>> >>>> >>>> S 2.3.2. >>>> > the "enforce", "max-age", or "report-uri" header field value >>>> > directives convey information different from that already >>>> > maintained by the UA. If the "max-age" directive has a value >>>> of >>>> > 0, the UA MUST remove its cached Expect-CT information if the >>>> host >>>> > was previously noted as a Known Expect-CT Host, and MUST NOT >>>> note >>>> > this host as a Known Expect-CT Host if it is not already >>>> noted. >>>> >>>> As noted above, I think you need to clear the cache when you upgrade >>>> to a potentially incompatible CT version, or otherwise reconfigure the >>>> client. >>>> >>>> >>>> S 2.3.2.1. >>>> > this host as a Known Expect-CT Host if it is not already >>>> noted. >>>> > >>>> > 2.3.2.1. Noting Expect-CT >>>> > >>>> > Upon receipt of the Expect-CT response header field over an >>>> error- >>>> > free TLS connection (including the validation adding in Section >>>> 2.4), >>>> >>>> s/adding/added/? >>>> >>>> >>>> S 2.3.2.1. >>>> > host's domain name and its associated Expect-CT directives in >>>> non- >>>> > volatile storage. >>>> > >>>> > To note a host as a Known Expect-CT Host, the UA MUST set its >>>> Expect- >>>> > CT metadata given in the most recently received valid Expect-CT >>>> > header field, as specified in Section 2.3.2.2. >>>> >>>> This seems ungrammatical. Set it where? >>>> >>>> >>>> S 2.3.2.2. >>>> > >>>> > 2.3.2.2. Storage Model >>>> > >>>> > If the substring matching the host production from the >>>> Request-URI >>>> > (of the message to which the host responded) does not congruently >>>> > match an existing Known Expect-CT Host's domain name, per the >>>> >>>> I would say "exactly match" rather than "congruently match" unless >>>> this ia term of art somewhere. >>>> >>>> >>>> S 2.3.2.2. >>>> > understands them, the UA MAY note them as well. >>>> > >>>> > UAs MAY set an upper limit on the value of max-age, so that UAs >>>> that >>>> > have noted erroneous Expect-CT hosts (whether by accident or due >>>> to >>>> > attack) have some chance of recovering over time. If the server >>>> sets >>>> > a max-age greater than the UA's upper limit, the UA MAY behave >>>> as if >>>> >>>> This MAY seems out of place, given that you already said MAY. >>>> >>>> >>>> S 2.4. >>>> > >>>> > When a UA connects to a Known Expect-CT Host using a TLS >>>> connection, >>>> > if the TLS connection has no errors, then the UA will apply an >>>> > additional correctness check: compliance with a CT Policy. A UA >>>> > should evaluate compliance with its CT Policy whenever >>>> connecting to >>>> > a Known Expect-CT Host, as soon as possible. However, the check >>>> can >>>> >>>> What does "as soon as possible" mean? >>>> >>>> >>>> S 2.4. >>>> > terminates the connection due to an Expect-CT failure, this could >>>> > cause the UA to skip subsequent correctness checks. When the CT >>>> > compliance check is skipped or bypassed, Expect-CT reports >>>> > (Section 3) will not be sent. >>>> > >>>> > When CT compliance is evaluted for a Known Expect-CT Host, the UA >>>> >>>> Nit: evaluated >>>> >>>> >>>> S 2.4.1. >>>> > "report-uri" (Section 3). >>>> > >>>> > 2.4.1. Skipping CT compliance checks >>>> > >>>> > It is acceptable for a UA to skip CT compliance checks for some >>>> hosts >>>> > according to local policy. For example, a UA may disable CT >>>> >>>> Should this be MAY? >>>> >>>> >>>> S 3.1. >>>> > >>>> > o "scts": the value represents the SCTs (if any) that the UA >>>> > received for the Expect-CT host and their validation statuses. >>>> > The value is provided as an array of JSON objects. The SCTs >>>> may >>>> > appear in any order. Each JSON object in the array has the >>>> > following keys: >>>> >>>> So these just apply to the EE cert? What about CT for the non-EE >>>> certs? >>>> >>>> >>>> >>>> >>>> S 3.1. >>>> > of, e.g., a bad signature). >>>> > >>>> > * The "source" key, with a string value that indicates from >>>> where >>>> > the UA obtained the SCT, as defined in Section 3 of >>>> [RFC6962] >>>> > and Section 6 of [I-D.ietf-trans-rfc6962-bis]. The UA >>>> MUST set >>>> > the value to one of "tls-extension", "ocsp", or "embedded". >>>> >>>> What do these mean? They seem obvious, but you don't say. >>>> >>>> >>>> >>>
- Re: Eric Rescorla's Discuss on draft-ietf-httpbis… Eric Rescorla
- Re: Eric Rescorla's Discuss on draft-ietf-httpbis… Emily Stark
- Re: Eric Rescorla's Discuss on draft-ietf-httpbis… Eric Rescorla
- Re: Eric Rescorla's Discuss on draft-ietf-httpbis… Emily Stark