| From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Cc: | Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: SCRAM salt length |
| Date: | 2017-08-17 20:50:52 |
| Message-ID: | 5b787a98-03f8-eb82-26c2-f731acc98c6e@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 8/17/17 12:10, Heikki Linnakangas wrote:
> On 08/17/2017 05:23 PM, Peter Eisentraut wrote:
>> On 8/17/17 09:21, Heikki Linnakangas wrote:
>>> The RFC doesn't say anything about salt
>>> length, but the one example in it uses a 16 byte string as the salt.
>>> That's more or less equal to the current default of 12 raw bytes, after
>>> base64-encoding.
>>
>> The example is
>>
>> S: r=rOprNGfwEbeRWgbNEkqO%hvYDpWUa2RaTCAfuxFIlj)hNlF$k0,
>> s=W22ZaJ0SNY7soEsUEjb6gQ==,i=4096
>>
>> That salt is 24 characters and 16 raw bytes.
>
> Ah, I see, that's from the SCRAM-SHA-256 spec. I was looking at the
> example in the original SCRAM-SHA-1 spec:
>
> S: r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j,s=QSXCR+Q6sek8bf92,
> i=4096
Hence my original inquiry: "I suspect that this length was chosen based
on the example in RFC 5802 (SCRAM-SHA-1) section 5. But the analogous
example in RFC 7677 (SCRAM-SHA-256) section 3 uses a length of 16.
Should we use that instead?"
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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