From: Japin Li <japinli@hotmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Bernd Helmle <mailings@oopsware.de>,  PostgreSQL Development
 <pgsql-hackers@postgresql.org>
Subject: Re: Modern SHA2- based password hashes for pgcrypto
In-Reply-To: <202502070931.7mcjufnk5g5l@alvherre.pgsql> (Alvaro Herrera's
	message of "Fri, 7 Feb 2025 10:31:44 +0100")
References: <202502070931.7mcjufnk5g5l@alvherre.pgsql>
Date: Sat, 08 Feb 2025 10:16:40 +0800
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On Fri, 07 Feb 2025 at 10:31, Alvaro Herrera <alvherre@alvh.no-ip.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