From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Michael Paquier <michael.paquier@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: David Steele <david@pgmasters.net>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David Fetter <david@fetter.org>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Magnus Hagander <magnus@hagander.net>
Cc: Julian Markwort <julian.markwort@uni-muenster.de>
Cc: Stephen Frost <sfrost@snowman.net>
Cc: PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Cc: Valery Popov <v.popov@postgrespro.ru>
Subject: Re: Password identifiers, protocol aging and SCRAM protocol
Date: Mon, 12 Dec 2016 16:39:55 +0200
Message-ID: <973937ca-cbed-ad48-c783-e29723a2a9c0@iki.fi> (raw)
In-Reply-To: <20161209111041.GA23215@paquier.xyz>
References: <CA+TgmoYydfT0ZwPaCMZannstRG207Ymf3s_aWTxkNJx9SBfm4Q@mail.gmail.com>
<CAB7nPqTAKNSBT6zzX8H0R8EwJ24Y8YsPmOqb3j38uzCoU_3+=A@mail.gmail.com>
<CAB7nPqSNMvJO50nJFoprf-wMMa281gJ-G6hfOr+krm8Zh8WLBg@mail.gmail.com>
<CAB7nPqRF=kVxqtC+Ei_t7eTrMti_0P+xUugSOd_7-rcLvREYzw@mail.gmail.com>
<e139fcbc-cfb2-3a64-93ac-afd5ba342960@iki.fi>
<CAB7nPqSqEwRgmVCS_OW3sJn6baymQ6MsO3kKMRvHLC0RZaKaYA@mail.gmail.com>
<21eecdb8-365b-8347-1ae2-5278d1fe798c@iki.fi>
<CAB7nPqT2UGWm0ukdomC+mG-co6nmKer62vuSGRxwtc+jS8uQPA@mail.gmail.com>
<CAB7nPqQtD7jOpYCsB4Ga=Cz+tgh4Ngac6NAV-WLs9zxaw0Uu7w@mail.gmail.com>
<3029e460-d47c-710e-507e-d8ba759d7cbb@iki.fi>
<20161209111041.GA23215@paquier.xyz>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-hackers>
A few couple more things that caught my eye while hacking on this:
1. We don't use SASLPrep to scrub username's and passwords. That's by
choice, for usernames, because historically in PostgreSQL usernames can
be stored in any encoding, but SASLPrep assumes UTF-8. We dodge that by
passing an empty username in the authentication exchange anyway, because
we always use the username we got from the startup packet. But for
passwords, I think we need to fix that. The spec is very clear on that:
> Note that implementations MUST either implement SASLprep or disallow
> use of non US-ASCII Unicode codepoints in "str".
2. I think we should check nonces, etc. more carefully, to not contain
invalid characters. For example, in the server, we use the
read_attr_value() function to read the client's nonce. Per the spec, the
nonce should consist of ASCII printable characters, but we will accept
anything except the comma. That's no trouble to the server, but let's be
strict.
To summarize, here's the overall TODO list so far:
* Use SASLPrep for passwords.
* Check nonces, etc. to not contain invalid characters.
* Derive mock SCRAM verifier for non-existent users deterministically
from username.
* Allow plain 'password' authentication for users with a SCRAM verifier
in rolpassword.
* Throw an error if an "authorization identity" is given. ATM, we just
ignore it, but seems better to reject the attempt than do something that
might not be what the client expects.
* Add "scram-sha-256" prefix to SCRAM verifiers stored in
pg_authid.rolpassword.
Anything else I'm missing?
I've created a wiki page, mostly to host that TODO list, while we hack
this to completion:
https://wiki.postgresql.org/wiki/SCRAM_authentication. Feel free to add
stuff that comes to mind, and remove stuff as you push patches to the
branch on github.
- Heikki
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: hlinnaka@iki.fi, michael.paquier@gmail.com, robertmhaas@gmail.com, andres@anarazel.de, peter.eisentraut@2ndquadrant.com, david@pgmasters.net, tgl@sss.pgh.pa.us, david@fetter.org, alvherre@2ndquadrant.com, magnus@hagander.net, julian.markwort@uni-muenster.de, sfrost@snowman.net, v.popov@postgrespro.ru
Subject: Re: Password identifiers, protocol aging and SCRAM protocol
In-Reply-To: <973937ca-cbed-ad48-c783-e29723a2a9c0@iki.fi>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox