Re: Modern SHA2- based password hashes for pgcrypto

On Fri, 07 Feb 2025 at 10:31, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> On 2025-Feb-07, Japin Li wrote:
>
>> Since there is no standard, how do we handle this? I prefer to use
>> the strict mode like passlib.
>
> I definitely like that passlib have documented their thought process
> thoroughly.
>
> I think using their strict mode is good on principle, but if we're going
> to do that, then the salt string should not be used verbatim, but
> instead base64-decoded first to get the actual salt bytes, like they do.
> Does this break compabitibility with other systems? Are
> passlib-generated password hashes incompatible with, say, "openssl
> passwd" which you (Bernd) mentioned at the beginning of the thread?
> Maybe if the password hashes are no longer compatible, then we should
> ditch the idea of restricting salts to base64 chars and accept the whole
> range of bytes, like Drepper.

Thinking about compatibility, the Drepper's behavior is a good choice.

Or we can accept the whole range of bytes except the $ character since it is
a separator. Of course, it is also not compatible with other systems.

>
> But in any case ISTM we should reject, as they suggest, the use of less
> than 4 bytes of salt (and should perhaps settle for a default of 16, as
> passlib suggests). I suppose this is why passlib returns NULL with
> empty salt. What we should do in that case IMO is ereport(ERROR).

+1

--
Regrads,
Japin Li