- From: Emily Stark <estark@google.com>
- Date: Tue, 4 Dec 2018 11:23:51 -0800
- To: Eric Rescorla <ekr@rtfm.com>
- Cc: iesg@ietf.org, httpbis-chairs@ietf.org, Mark Nottingham <mnot@mnot.net>, draft-ietf-httpbis-expect-ct@ietf.org, httpbis <ietf-http-wg@w3.org>
- Message-ID: <CAPP_2Sb6Bzgy9B96SacGhcuCs36TzMtWNW+nuttrN9TCZw8QXg@mail.gmail.com>
Hi again, Thanks for your patience. I've addressed these comments in https://github.com/httpwg/http-extensions/commit/58a16cdcc535bde6bd7532b021d9473e6eb5b112. I added a note in the introduction and in 2.3.2 that this version of Expect-CT is only compatible with RFC 6962 and 6962-bis and not any future versions of CT. Also see a couple replies inline. Emily On Wed, Nov 21, 2018 at 2:17 PM Eric Rescorla <ekr@rtfm.com> wrote: > 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? >>>>> >>>>> This had been brought up in a previous review and is now limited to HTTPS. > >>>>> 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? >>>>> >>>> AFAIK 6962 and 6962-bis only define ways to deliver SCTs for the EE cert, so that's all that Expect-CT is concerned with. Theoretically I suppose future versions of CT and Expect-CT could handle intermediate certs as well. > >>>>> >>>>> >>>>> >>>>> 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. >>>>> >>>>> >>>>> >>>>
Received on Tuesday, 4 December 2018 19:24:26 UTC