Re: [HACKERS] SCRAM salt length

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/
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