Re: [http-auth] Definition of SHA256 and SHA512/256 algorithms in RFC 7616

Chaim Geretz <chaim.geretz@idt.net> Thu, 29 December 2016 18:12 UTC

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From: Chaim Geretz <chaim.geretz@idt.net>
Date: Thu, 29 Dec 2016 13:12:20 -0500
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To: Sophie Bremer <sophie.bremer@netzkonform.de>
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Subject: Re: [http-auth] Definition of SHA256 and SHA512/256 algorithms in RFC 7616
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Sophie,

Thanks for your response

> The linked IANA registry for the hash algorithms clarifies the use as in
FIPS 180-3.

The reference to FIPS 180-3 is only for the HTTP Digest Algorithm
Values SHA-256
and SHA-512.

http://www.iana.org/assignments/http-dig-alg/http-dig-alg.txt does not
include any specification information for SHA-512-256 save for a pointer to
RFC 7616.

Chaim


On Thu, Dec 29, 2016 at 12:43 PM, Sophie Bremer <
sophie.bremer@netzkonform.de> wrote:

> Hi Chaim,
>
> thank you for pointing this out!
> It explains some problems I had myself with the implementation for proxy
> servers.
>
> > Am 28.12.2016 um 20:19 schrieb Chaim Geretz <chaim.geretz@idt.net>et>:
> >
> > Greetings,
> >
> > I think that RFC 7616 needs to define or point to a document describing
> how the various hash algorithms mentioned in Section 3.2 are to be
> implemented.
>
> The linked IANA registry for the hash algorithms clarifies the use as in
> FIPS 180-3.
> On the other hand the registry may change in the future and so the
> definition of the algorithm value too.
> If this is a possible scenario, I agree with you.
> I like to see more opinions for this proposal.
>
> > Inspecting the values used in Section 3.9.2 for userhash and response
> shows that they are generated by truncating the hex output of a sha512 hash
> to the initial 64 hex characters.
>
> You are right.
>
> > If this is the desired implementation of SHA512/256 then this should be
> mentioned in the RFC.
>
> The example is not in sync with the IANA registry and has to be updated.
>
> > If the intention is to use SHA512/256 as described in FIPS 180.4 then
> this should be mentioned, and the values changed to
> userhash="793263caabb707a56211940d90411ea4a575adeccb7e360aeb624ed06ece9b0b"
> and response="3798d4131c277846293534c3edc11bd8a5e4cdcbff78b05db9
> d95eeb1cec68a5"
>
> I will look into your provided values and clarify/correct the example.
>
> Once again, thank you for this catch!
>
> Best Regards,
> Sophie
>