Herve--
I'm not sure that the text in 7.1.2 is explicit enough to be understood--
I'd be hard-pressed to define "guess" reliably. The bit that is missing,
imho, is that the provenance of the request is from a 3rd party, which is
reason to be suspicious.
An alternate wording:
An encoder seeing many 3rd party requests which contain keys whose values
never match may decided to ensure that such keys are never indexed when
going to that site, as this effectively prevents probing of the compression
context, and, if not malicious, would likely offer no benefit from indexing
anyway.
-=R
On Mon, Jan 26, 2015 at 9:29 AM, Hervé Ruellan
<herve(_dot_)ruellan(_at_)crf(_dot_)canon(_dot_)fr>
wrote:
I tried to integrate all these comments, as well as those of Martin on
GitHub into: https://github.com/http2/http2-spec/pull/704
Hervé.
On 01/23/2015 05:51 PM, Black, David wrote:
This sort of guidance will definitely be a useful addition. A little
more wordsmithing on Stephen's proposed text follows:
The decision on whether a header field is ok to
compress or
not is highly dependent on the context. As a generic
guidance, header fields used for conveying highly valued
information, such as the Authorization or Cookie header
fields, can be considered to be on the more sensitive
side. In addition, a header field with a short value
has potentially a smaller entropy and can be more at
risk. We know that compressing low-entropy sensitive
header fields can create vulnerabilities so such
cases are most likely the ones to not compress today.
Note though that the criteria to apply here may evolve
over time as we gain knowledge of new attacks.
OLD
We know that compressing low-entropy sensitive
header fields can create vulnerabilities so such
cases are most likely the ones to not compress today.
Note though that the criteria to apply here may evolve
over time as we gain knowledge of new attacks.
NEW
We currently know that compressing low-entropy sensitive
header fields can create vulnerabilities so compression
of such fields ought to be avoided.
This guidance may evolve
over time as we gain knowledge of new attacks.
Thanks,
--David
-----Original Message-----
From: Stephen Farrell
[mailto:stephen(_dot_)farrell(_at_)cs(_dot_)tcd(_dot_)ie]
Sent: Friday, January 23, 2015 10:45 AM
To: Jari Arkko; Hervé Ruellan
Cc: Martin Thomson; Black, David; ietf(_at_)ietf(_dot_)org; General Area
Review
Team
(gen-art(_at_)ietf(_dot_)org); fenix(_at_)google(_dot_)com;
ietf-http-wg(_at_)w3(_dot_)org
Subject: Re: [Gen-art] Gen-ART and OPS-Dir review of draft-ietf-httpbis-
header-compression-10
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Hash: SHA1
On 23/01/15 15:35, Jari Arkko wrote:
I made a proposal at
https://github.com/http2/http2-spec/pull/704
Looked reasonable to me.
Me too. Quibbling, I'd suggest:
OLD:
The decision on whether a header field is sensitive or
not is highly dependent on the context. As a generic
guidance, header fields used for conveying highly valued
information, such as the Authorization or Cookie header
fields, can be considered to be on the more sensitive
side. In addition, a header field with a short value
has potentially a smaller entropy and can be more at
risk.
NEW:
The decision on whether a header field is ok to
compress or
not is highly dependent on the context. As a generic
guidance, header fields used for conveying highly valued
information, such as the Authorization or Cookie header
fields, can be considered to be on the more sensitive
side. In addition, a header field with a short value
has potentially a smaller entropy and can be more at
risk. We know that compressing low-entropy sensitive
header fields can create vulnerabilities so such
cases are most likely the ones to not compress today.
Note though that the criteria to apply here may evolve
over time as we gain knowledge of new attacks.
Cheers,
S.
jari
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