Re: On-disk format of SCRAM verifiers

Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:

> On Fri, Apr 21, 2017 at 10:02 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> On 21 April 2017 at 10:20, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>>> But looking more closely, I think I misunderstood RFC 5803. It *does* in
>>> fact specify a single string format to store the verifier in. And the format
>>> looks like:
>>>
>>> SCRAM-SHA-256$<iteration count>:<salt>$<StoredKey>:<ServerKey>
>>
>> Could you explain where you are looking? I don't see that in RFC5803
>
> From 1. Overview:
>
> Syntax of the attribute can be expressed using ABNF [RFC5234]. Non-
> terminal references in the following ABNF are defined in either
> [AUTHPASS], [RFC4422], or [RFC5234].
>
> scram-mech = "SCRAM-SHA-1" / scram-mech-ext
> ; Complies with ABNF for <scheme>
> ; defined in [AUTHPASS].
>
> scram-authInfo = iter-count ":" salt
> ; Complies with ABNF for <authInfo>
> ; defined in [AUTHPASS].
>
> scram-authValue = stored-key ":" server-key
> ; Complies with ABNF for <authValue>
> ; defined in [AUTHPASS].

And scram-mech, scram-authInfo and scram-authValue are used as the
"scheme", "authInfo" and "authValue" parts as specified in [AUTHPASS]
(RFC3112):

authPasswordValue = w scheme s authInfo s authValue w
scheme = %x30-39 / %x41-5A / %x2D-2F / %x5F
; 0-9, A-Z, "-", ".", "/", or "_"
authInfo = schemeSpecificValue
authValue = schemeSpecificValue
schemeSpecificValue = *( %x21-23 / %x25-7E )
; printable ASCII less "$" and " "
s = w SEP w
w = *SP
SEP = %x24 ; "$"
SP = %x20 ; " " (space)

> Thanks,
> --
> Michael

- ilmari
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