Re: [Gen-art] Genart last call review of draft-ietf-httpbis-origin-frame-04

Mark Nottingham <> Sun, 26 November 2017 23:38 UTC

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From: Mark Nottingham <>
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Date: Mon, 27 Nov 2017 10:38:43 +1100
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To: Brian Carpenter <>
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Subject: Re: [Gen-art] Genart last call review of draft-ietf-httpbis-origin-frame-04
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Hi Brian,

Thanks for the review. Responses below.

> On 26 Nov 2017, at 2:44 pm, Brian Carpenter <>; wrote:
> Minor Issues:
> -------------
>> 2.1.  Syntax
> ...
>> Origin: An OPTIONAL sequence of characters ... that the
>> sender believes this connection is or could be authoritative for.
> So, that implies that all data in the ORIGIN frame might be false.
> Doesn't that deserve a bit of a health warning at the beginning of the
> Security Considerations?

The first paragraph of SC is already:

   Clients that blindly trust the ORIGIN frame's contents will be
   vulnerable to a large number of attacks.  See Section 2.4 for mitigations.

What would you suggest?

> Also, using the word "believes" of a server
> is strange. How would the server acquire uncertain knowledge in the
> first place, and what algorithm would decide what it "believes"?

This is to emphasise that ORIGIN is advisory only -- it does not constitute proof (crypto does that).

> Appendix A doesn't show any sign of a client checking whether an
> Origin-Entry is real.

As per Section 2.4, it isn't checked when the origin set is created or updated; it's checked when the value is used.

>> 2.3.  The Origin Set
> ...
>>  o  Host: the value sent in Server Name Indication (SNI, [RFC6066]
>>     Section 3), converted to lower case
> In that reference:
>>> Literal IPv4 and IPv6 addresses are not permitted in "HostName".
> Is that an intended or unintended restriction for the ORIGIN frame?
> In any case it should probably be mentioned explicitly to avoid confusion.
> (If IPv6 literals were allowed, they might be very convenient for server
> load balancing. But RFC6066 excludes that.)

Good catch. I don't think there's cause for confusion here (the text there isn't about what can go on the wire), but there is a corner case we haven't covered (when a client that supports SNI omits it because it's an IP literal). 

My inclination there is to say that the host is the SNI value or the server IP if SNI is missing; what do people think?


Mark Nottingham