Horton

Thread

  1. rolcanlogin vs. the flat password file

    Tom Lane <tgl@sss.pgh.pa.us> — 2007-10-14T19:34:11Z

    There's a gripe over here
http://archives.postgresql.org/pgsql-general/2007-10/msg00640.php
to the effect that PG should not give a message like "password
authentication failure" when the user is attempting to log in as a
NOLOGIN role.  This surprised me because there is a specific message
for that, and it worked when I tried it:

regression=# create user foo nologin;
CREATE ROLE
regression=# \c - foo
FATAL:  role "foo" is not permitted to log in
Previous connection kept
regression=# 

On investigation though, it turns out that it depends on which auth
mode you're using: some of the auth modes look up the user in the
flat password file, and some don't.  Now flatfiles.c makes a point of
not entering roles into the flat password file if they are not
rolcanlogin, which means that for password auth you are guaranteed to
fail long before you can get to the explicit check in
InitializeSessionUserId.

We could certainly change flatfiles.c to disregard rolcanlogin, which'd
actually make the code simpler.  However, that in itself wouldn't change
the behavior, unless you were to assign a password to the NOLOGIN role
which seems a fairly strange thing to do.  I think what the OP wishes
is that "not permitted to log in" would be checked before checking
password validity, and to do that we'd have to add rolcanlogin
to the flat password file and put the check somewhere upstream of the
authentication process.

I am not entirely convinced whether we should do anything about this:
the general theory on authentication failures is that you don't say much
about exactly why it failed, so as to not give a brute-force attacker
any info about whether he gave a valid userid or not.  So there's an
argument to be made that the current behavior is what we want.  But
I'm pretty sure that it wasn't intentionally designed to act this way.

Comments?

			regards, tom lane

  2. Re: rolcanlogin vs. the flat password file

    Michael Glaesemann <grzm@seespotcode.net> — 2007-10-14T20:09:58Z

    On Oct 14, 2007, at 14:34 , Tom Lane wrote:

> I am not entirely convinced whether we should do anything about this:
> the general theory on authentication failures is that you don't say  
> much
> about exactly why it failed, so as to not give a brute-force attacker
> any info about whether he gave a valid userid or not.  So there's an
> argument to be made that the current behavior is what we want.  But
> I'm pretty sure that it wasn't intentionally designed to act this way.

Would there be a difference in how this is logged and how it's  
reported to the user? I can see where an admin (having access to  
logs) would want to have additional information such as whether a  
role login has failed due to not having login privileges or whether  
the failure was due to an incorrect role/password pair. I lean  
towards less information back to the user as to the nature of the  
failure. If the general consensus is to leave the current behavior, a  
comment should probably be included to note that the behavior is  
intentional.

Michael Glaesemann
grzm seespotcode net

  3. Re: rolcanlogin vs. the flat password file

    Stephen Frost <sfrost@snowman.net> — 2007-10-14T20:51:12Z

    * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> We could certainly change flatfiles.c to disregard rolcanlogin, which'd
> actually make the code simpler.  However, that in itself wouldn't change
> the behavior, unless you were to assign a password to the NOLOGIN role
> which seems a fairly strange thing to do.  I think what the OP wishes
> is that "not permitted to log in" would be checked before checking
> password validity, and to do that we'd have to add rolcanlogin
> to the flat password file and put the check somewhere upstream of the
> authentication process.

I wonder if the OP was unhappy because he created a role w/ a pw and
then couldn't figure out why the user couldn't log in?  I've run into
that in the past and it takes some leg-work to figure out what's going
on.  A warning on a 'create role' or 'alter role' command which sets a
password when 'rolcanlogin' is false might be an alternative way to
'fix' this.

In general, I would say that it's correct to say 'invalid
authentication'/'bad pw' until the user is authenticated and then say
'not permitted to log in' if they're not authorized (don't have
rolcanlogin), which is I think what we do.  That combined with the
warning above would, I think, cover most of problem cases.

	Thanks,

		Stephen

  4. Re: rolcanlogin vs. the flat password file

    Tom Lane <tgl@sss.pgh.pa.us> — 2007-10-14T20:56:25Z

    Michael Glaesemann <grzm@seespotcode.net> writes:
> Would there be a difference in how this is logged and how it's  
> reported to the user?

Not without making all the same infrastructure changes that would be
needed to tell the user something different than now.  As things stand,
the password auth code can't tell the difference between a nonexistent
role and a nologin role; neither one has an entry in the flat file.
If we dropped the filtering in flatfiles.c, then a nologin role would
have an entry, but most likely without a password, so you'd still just
see "password auth failed".

			regards, tom lane

  5. Re: rolcanlogin vs. the flat password file

    Tom Lane <tgl@sss.pgh.pa.us> — 2007-10-14T21:02:43Z

    Stephen Frost <sfrost@snowman.net> writes:
> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>> ... I think what the OP wishes
>> is that "not permitted to log in" would be checked before checking
>> password validity, and to do that we'd have to add rolcanlogin
>> to the flat password file and put the check somewhere upstream of the
>> authentication process.

> I wonder if the OP was unhappy because he created a role w/ a pw and
> then couldn't figure out why the user couldn't log in?

Hm, maybe.  In that case just not filtering the entry out of the flat
file would be good enough.  In hindsight I'm not sure why we indulged
in that bit of complication anyway --- it seems unlikely that an
installation would have so many nologin roles, compared to regular ones,
that the increase in size of the flat file would be objectionable.

> In general, I would say that it's correct to say 'invalid
> authentication'/'bad pw' until the user is authenticated and then say
> 'not permitted to log in' if they're not authorized (don't have
> rolcanlogin), which is I think what we do.

That *would* be the behavior if we removed the filtering.

			regards, tom lane

  6. Re: rolcanlogin vs. the flat password file

    Tom Lane <tgl@sss.pgh.pa.us> — 2007-10-14T21:20:10Z

    I wrote:
> Stephen Frost <sfrost@snowman.net> writes:
>> I wonder if the OP was unhappy because he created a role w/ a pw and
>> then couldn't figure out why the user couldn't log in?

> Hm, maybe.  In that case just not filtering the entry out of the flat
> file would be good enough.

I've confirmed the confusing behavior in CVS HEAD.  With password auth
selected in pg_hba.conf:

postgres=# create user foo nologin;
CREATE ROLE
postgres=# \c - foo    
Password for user "foo": 
FATAL:  password authentication failed for user "foo"
Previous connection kept
postgres=# alter user foo password 'foo';
ALTER ROLE
postgres=# \c - foo
Password for user "foo": << correct password entered here
FATAL:  password authentication failed for user "foo"
Previous connection kept

With the attached patch to not drop nologin roles from the flat password
file, it acts more sanely:

postgres=# create user foo nologin;
CREATE ROLE
postgres=# \c - foo
Password for user "foo": 
FATAL:  password authentication failed for user "foo"
Previous connection kept
postgres=# alter user foo password 'foo';
ALTER ROLE
postgres=# \c - foo
Password for user "foo": << correct password entered here
FATAL:  role "foo" is not permitted to log in
Previous connection kept

Should we just do this, or is it worth working harder?

			regards, tom lane


*** src/backend/utils/init/flatfiles.c.orig	Wed Aug  1 18:45:08 2007
--- src/backend/utils/init/flatfiles.c	Sun Oct 14 17:14:27 2007
***************
*** 298,304 ****
   *
   * The format for the flat auth file is
   *		"rolename" "password" "validuntil" "memberof" "memberof" ...
-  * Only roles that are marked rolcanlogin are entered into the auth file.
   * Each role's line lists all the roles (groups) of which it is directly
   * or indirectly a member, except for itself.
   *
--- 298,303 ----
***************
*** 312,318 ****
  typedef struct
  {
  	Oid			roleid;
- 	bool		rolcanlogin;
  	char	   *rolname;
  	char	   *rolpassword;
  	char	   *rolvaliduntil;
--- 311,316 ----
***************
*** 407,414 ****
  						tempname)));
  
  	/*
! 	 * Read pg_authid and fill temporary data structures.  Note we must read
! 	 * all roles, even those without rolcanlogin.
  	 */
  	totalblocks = RelationGetNumberOfBlocks(rel_authid);
  	totalblocks = totalblocks ? totalblocks : 1;
--- 405,411 ----
  						tempname)));
  
  	/*
! 	 * Read pg_authid and fill temporary data structures.
  	 */
  	totalblocks = RelationGetNumberOfBlocks(rel_authid);
  	totalblocks = totalblocks ? totalblocks : 1;
***************
*** 433,439 ****
  		}
  
  		auth_info[curr_role].roleid = HeapTupleGetOid(tuple);
- 		auth_info[curr_role].rolcanlogin = aform->rolcanlogin;
  		auth_info[curr_role].rolname = pstrdup(NameStr(aform->rolname));
  		auth_info[curr_role].member_of = NIL;
  
--- 430,435 ----
***************
*** 565,574 ****
  			List	   *roles_names_list = NIL;
  			ListCell   *mem;
  
- 			/* We can skip this for non-login roles */
- 			if (!auth_info[curr_role].rolcanlogin)
- 				continue;
- 
  			/*
  			 * This search algorithm is the same as in is_member_of_role; we
  			 * are just working with a different input data structure.
--- 561,566 ----
***************
*** 642,650 ****
  	for (curr_role = 0; curr_role < total_roles; curr_role++)
  	{
  		auth_entry *arole = &auth_info[curr_role];
- 
- 		if (arole->rolcanlogin)
- 		{
  			ListCell   *mem;
  
  			fputs_quote(arole->rolname, fp);
--- 634,639 ----
***************
*** 660,666 ****
  			}
  
  			fputs("\n", fp);
- 		}
  	}
  
  	if (FreeFile(fp))
--- 649,654 ----

  7. Re: rolcanlogin vs. the flat password file

    Andrew Dunstan <andrew@dunslane.net> — 2007-10-14T21:56:10Z

    
Tom Lane wrote:
>
> Should we just do this, or is it worth working harder?
>
> 			
>   

Not worth more, IMNSHO.

cheers

andrew

  8. Re: rolcanlogin vs. the flat password file

    Stephen Frost <sfrost@snowman.net> — 2007-10-14T22:16:04Z

    * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> > Stephen Frost <sfrost@snowman.net> writes:
> >> I wonder if the OP was unhappy because he created a role w/ a pw and
> >> then couldn't figure out why the user couldn't log in?
> 
> > Hm, maybe.  In that case just not filtering the entry out of the flat
> > file would be good enough.
> 
> I've confirmed the confusing behavior in CVS HEAD.  With password auth
> selected in pg_hba.conf:
[...]
> Should we just do this, or is it worth working harder?

I certainly like this.  Honestly, I'd also like the warning when doing a
'create role'/'alter role' that sets/changes the pw on an account that
doesn't have 'rolcanlogin'.  Much better to have me notice that I goof'd
the command and fix it before telling the user 'go ahead and log in'
than to have the user complain that it's not working. :)

Just my 2c.

	Thanks,

		Stephen

  9. Re: rolcanlogin vs. the flat password file

    Michael Paesold <mpaesold@gmx.at> — 2007-10-15T06:18:33Z

    Tom Lane wrote:
> With the attached patch to not drop nologin roles from the flat password
> file, it acts more sanely:
> 
> postgres=# create user foo nologin;
> CREATE ROLE
> postgres=# \c - foo
> Password for user "foo": 
> FATAL:  password authentication failed for user "foo"
> Previous connection kept
> postgres=# alter user foo password 'foo';
> ALTER ROLE
> postgres=# \c - foo
> Password for user "foo": << correct password entered here
> FATAL:  role "foo" is not permitted to log in
> Previous connection kept
> 
> Should we just do this, or is it worth working harder?

IMHO this is exactly what we want. It does only offer more information when 
you already got authentication right and therefore doesn't open an 
information leak.

Not sure about the warning when creating a role with a password but 
nologin. Could be useful.

Best Regards
Michael Paesold

  10. Re: rolcanlogin vs. the flat password file

    Magnus Hagander <magnus@hagander.net> — 2007-10-17T14:46:34Z

    On Sun, Oct 14, 2007 at 06:16:04PM -0400, Stephen Frost wrote:
> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> > > Stephen Frost <sfrost@snowman.net> writes:
> > >> I wonder if the OP was unhappy because he created a role w/ a pw and
> > >> then couldn't figure out why the user couldn't log in?
> > 
> > > Hm, maybe.  In that case just not filtering the entry out of the flat
> > > file would be good enough.
> > 
> > I've confirmed the confusing behavior in CVS HEAD.  With password auth
> > selected in pg_hba.conf:
> [...]
> > Should we just do this, or is it worth working harder?
> 
> I certainly like this.  Honestly, I'd also like the warning when doing a
> 'create role'/'alter role' that sets/changes the pw on an account that
> doesn't have 'rolcanlogin'.  Much better to have me notice that I goof'd
> the command and fix it before telling the user 'go ahead and log in'
> than to have the user complain that it's not working. :)
> 
> Just my 2c.

I think that's a good idea. Attached is a patch that implements this (I
think - haven't messed around in that area of the code before). Thoughts?

//Magnus

  11. Re: rolcanlogin vs. the flat password file

    Stephen Frost <sfrost@snowman.net> — 2007-10-17T15:01:16Z

    * Magnus Hagander (magnus@hagander.net) wrote:
> I think that's a good idea. Attached is a patch that implements this (I
> think - haven't messed around in that area of the code before). Thoughts?

Cool, thanks!

My only comment is that you should probably stick to one 'zero'
convention- either '!canlogin' or 'canlogin == 0'.  I prefer the former,
but the inconsistancy in a single patch is kind of odd.  I'm not sure if
there's an overall PG preference.

	Thanks,

		Stephen

  12. Re: rolcanlogin vs. the flat password file

    Heikki Linnakangas <heikki@enterprisedb.com> — 2007-10-17T15:15:05Z

    Magnus Hagander wrote:
> On Sun, Oct 14, 2007 at 06:16:04PM -0400, Stephen Frost wrote:
>> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>>>> Stephen Frost <sfrost@snowman.net> writes:
>>>>> I wonder if the OP was unhappy because he created a role w/ a pw and
>>>>> then couldn't figure out why the user couldn't log in?
>>>> Hm, maybe.  In that case just not filtering the entry out of the flat
>>>> file would be good enough.
>>> I've confirmed the confusing behavior in CVS HEAD.  With password auth
>>> selected in pg_hba.conf:
>> [...]
>>> Should we just do this, or is it worth working harder?
>> I certainly like this.  Honestly, I'd also like the warning when doing a
>> 'create role'/'alter role' that sets/changes the pw on an account that
>> doesn't have 'rolcanlogin'.  Much better to have me notice that I goof'd
>> the command and fix it before telling the user 'go ahead and log in'
>> than to have the user complain that it's not working. :)
>>
>> Just my 2c.
> 
> I think that's a good idea. Attached is a patch that implements this (I
> think - haven't messed around in that area of the code before). Thoughts?

Is WARNING an appropriate level for this? I think NOTICE is enough, it's
not like something bad is going to happen if you do that, it just means
that you've likely screwed up.

There's legitimate use for creating a role with NOLOGIN and a password.
Maybe you're going to give login privilege later on. It wouldn't be nice
to get WARNINGs in that case, even NOTICEs would be sligthly annoying.

Note that per-role guc variables will also have no effect on a role with
no login privilege. How about connection limit, is that inherited?

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

  13. Re: rolcanlogin vs. the flat password file

    Tom Lane <tgl@sss.pgh.pa.us> — 2007-10-17T15:27:10Z

    Heikki Linnakangas <heikki@enterprisedb.com> writes:
> There's legitimate use for creating a role with NOLOGIN and a password.

If we think that, then we shouldn't have a message at all.

			regards, tom lane

  14. Re: rolcanlogin vs. the flat password file

    Stephen Frost <sfrost@snowman.net> — 2007-10-17T15:35:41Z

    * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> Heikki Linnakangas <heikki@enterprisedb.com> writes:
> > There's legitimate use for creating a role with NOLOGIN and a password.
> 
> If we think that, then we shouldn't have a message at all.

I'm not sure I agree with that.  I don't agree that there's really a
legitimate use for creating a role w/ NOLOGIN and a password either, for
that matter.  A 'NOTICE' level message would be fine with me.  We have
NOTICE messages for when we create an index for a PK.  I find a message
about an entirely unexpected and unworkable configuration alot more
useful than those.

	Thanks,

		Stephen

  15. Re: rolcanlogin vs. the flat password file

    Dave Page <dpage@postgresql.org> — 2007-10-17T16:09:25Z

    Stephen Frost wrote:
> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>> Heikki Linnakangas <heikki@enterprisedb.com> writes:
>>> There's legitimate use for creating a role with NOLOGIN and a password.
>> If we think that, then we shouldn't have a message at all.
> 
> I'm not sure I agree with that.  I don't agree that there's really a
> legitimate use for creating a role w/ NOLOGIN and a password either, for
> that matter. 

Preparing a new user account prior to an employee starting? In my last
post we would do that regularly - setup all the accounts etc for the new
user, but disable them all until the start date.

/D

  16. Re: rolcanlogin vs. the flat password file

    Magnus Hagander <magnus@hagander.net> — 2007-10-17T16:39:12Z

    On Wed, Oct 17, 2007 at 05:09:25PM +0100, Dave Page wrote:
> Stephen Frost wrote:
> > * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> >> Heikki Linnakangas <heikki@enterprisedb.com> writes:
> >>> There's legitimate use for creating a role with NOLOGIN and a password.
> >> If we think that, then we shouldn't have a message at all.
> > 
> > I'm not sure I agree with that.  I don't agree that there's really a
> > legitimate use for creating a role w/ NOLOGIN and a password either, for
> > that matter. 
> 
> Preparing a new user account prior to an employee starting? In my last
> post we would do that regularly - setup all the accounts etc for the new
> user, but disable them all until the start date.

Yeah, but did you actually set a password for them?

We do that all the time here, but we don't set the passwords until they
show up.

//Magnus

  17. Re: rolcanlogin vs. the flat password file

    Magnus Hagander <magnus@hagander.net> — 2007-10-17T16:41:00Z

    On Wed, Oct 17, 2007 at 11:27:10AM -0400, Tom Lane wrote:
> Heikki Linnakangas <heikki@enterprisedb.com> writes:
> > There's legitimate use for creating a role with NOLOGIN and a password.
> 
> If we think that, then we shouldn't have a message at all.

At least if we think it's more than a very narrow legitimate use, compared
to the number of ppl making the mistake.

I agree with making it a NOTICE instead of WARNING though.

//Magnus

  18. Re: rolcanlogin vs. the flat password file

    Dave Page <dpage@postgresql.org> — 2007-10-17T16:47:26Z

    Magnus Hagander wrote:
> On Wed, Oct 17, 2007 at 05:09:25PM +0100, Dave Page wrote:
>> Stephen Frost wrote:
>>> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>>>> Heikki Linnakangas <heikki@enterprisedb.com> writes:
>>>>> There's legitimate use for creating a role with NOLOGIN and a password.
>>>> If we think that, then we shouldn't have a message at all.
>>> I'm not sure I agree with that.  I don't agree that there's really a
>>> legitimate use for creating a role w/ NOLOGIN and a password either, for
>>> that matter. 
>> Preparing a new user account prior to an employee starting? In my last
>> post we would do that regularly - setup all the accounts etc for the new
>> user, but disable them all until the start date.
> 
> Yeah, but did you actually set a password for them?

Yeah, then have them change them all during day 1 IT induction training.

We had a much smaller team that I know you do, and the staff that would
do the account setup would often be busy first thing on Monday morning
when new starters might often arrive - so we would just 'flip the
switch' on the pre-configured accounts.

/D

  19. Re: rolcanlogin vs. the flat password file

    Magnus Hagander <magnus@hagander.net> — 2007-10-22T18:53:54Z

    Magnus Hagander wrote:
> On Wed, Oct 17, 2007 at 11:27:10AM -0400, Tom Lane wrote:
>> Heikki Linnakangas <heikki@enterprisedb.com> writes:
>>> There's legitimate use for creating a role with NOLOGIN and a password.
>> If we think that, then we shouldn't have a message at all.
> 
> At least if we think it's more than a very narrow legitimate use, compared
> to the number of ppl making the mistake.
> 
> I agree with making it a NOTICE instead of WARNING though.

Did we ever come to a conclusion on this or not? I've changed my patch
per the suggestions in the thread, but I've held back on committing it
to hear arguments... Go or no-go?

//Magnus

  20. Re: rolcanlogin vs. the flat password file

    Tom Lane <tgl@sss.pgh.pa.us> — 2007-10-22T21:05:21Z

    Magnus Hagander <magnus@hagander.net> writes:
> Heikki Linnakangas <heikki@enterprisedb.com> writes:
>> At least if we think it's more than a very narrow legitimate use, compared
>> to the number of ppl making the mistake.

> Did we ever come to a conclusion on this or not? I've changed my patch
> per the suggestions in the thread, but I've held back on committing it
> to hear arguments... Go or no-go?

I'm inclined to vote no-go on the message.  AFAIR we've only heard the
one complaint about this, so I'm not convinced there's a lot of people
making such a mistake.  We did make the logic change to deal with the
underlying problem of a misleading error message after you'd done it,
and I think that might be enough.

			regards, tom lane

  21. Re: rolcanlogin vs. the flat password file

    Magnus Hagander <magnus@hagander.net> — 2007-10-23T18:10:31Z

    Tom Lane wrote:
> Magnus Hagander <magnus@hagander.net> writes:
>> Heikki Linnakangas <heikki@enterprisedb.com> writes:
>>> At least if we think it's more than a very narrow legitimate use, compared
>>> to the number of ppl making the mistake.
> 
>> Did we ever come to a conclusion on this or not? I've changed my patch
>> per the suggestions in the thread, but I've held back on committing it
>> to hear arguments... Go or no-go?
> 
> I'm inclined to vote no-go on the message.  AFAIR we've only heard the
> one complaint about this, so I'm not convinced there's a lot of people
> making such a mistake.  We did make the logic change to deal with the
> underlying problem of a misleading error message after you'd done it,
> and I think that might be enough.

Ok. I'm dropping it for now. If someone wants it later, the patch is in
the archives...

//Magnus

  22. Re: rolcanlogin vs. the flat password file

    Alvaro Herrera <alvherre@commandprompt.com> — 2007-10-23T18:25:25Z

    Magnus Hagander wrote:
> Tom Lane wrote:
> > Magnus Hagander <magnus@hagander.net> writes:
> >> Heikki Linnakangas <heikki@enterprisedb.com> writes:
> >>> At least if we think it's more than a very narrow legitimate use, compared
> >>> to the number of ppl making the mistake.
> > 
> >> Did we ever come to a conclusion on this or not? I've changed my patch
> >> per the suggestions in the thread, but I've held back on committing it
> >> to hear arguments... Go or no-go?
> > 
> > I'm inclined to vote no-go on the message.  AFAIR we've only heard the
> > one complaint about this, so I'm not convinced there's a lot of people
> > making such a mistake.  We did make the logic change to deal with the
> > underlying problem of a misleading error message after you'd done it,
> > and I think that might be enough.
> 
> Ok. I'm dropping it for now. If someone wants it later, the patch is in
> the archives...

Indulge me while I say that it's pretty useless there.  The archiver
mangles it pretty badly -- I have never found a patch you could actually
use in the archives (or on Bruce's queues for that matter).  What I have
had to do was log into the majordomo page and have it send the email to
me.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.