Re: user-defined default public acl

<sorry, I resend this as I have not received it from the list, and it does
not appear in the archives...>

Dear Tom,

> > defaults in "src/backend/utils/adt/acl.c".
>
> I'm unconvinced that this is a good idea.

Hmmm.

> In the first place I am unsure what sorts of surprising behaviors might
> result from nontraditional defaults for these ACL settings.

Sure, this should be thought of.

> (I find the precedent of "umask 077" unconvincing because a Unix
> filesystem only deals with two kinds of objects, files and directories,
> with not-so-different protection behaviors. I don't know that that
> scales up to SQL.)

I wouldn't want default rights for different objects to be mixed.
Also, it is about "public" rights, that is "other" wrt unix umask.
"public" means anybody, and my opinion is that anybody should not
be given anything implicitly.

> > Also, I'm afraid that empty acl arrays (from what is seen from acl fields
> > when dumping pg_database or other tables) have a meaning at the time,
> > which is "default"... this may interact with new user-defined defaults.
>
> Yup, it would, and that strikes me as another fertile place for problems.
> You will have to make some basic changes in the way that default ACLs
> are handled, or else such a feature would introduce security holes.

Sure.

> I'm not sure how much user-facing behavior would have to change, but
> I doubt it could be a completely transparent change.

Should be investigated.

> Another area to think about is the implications for pg_dump, and
> especially the implications for reloading existing dump scripts.
> If the postgresql.conf settings for default ACLs are nonstandard,
> wouldn't that result in reloaded objects acquiring different ACLs
> than they had before? Is that a good idea?

Well, I thought that pg_dump/restore would restore anything, including
ACL. However, if some assumptions are made about default ACL this
may be an issue.

> Before buying into all this, it would be nice to see a better rationale
> than "this surprised me and it's easy to fix". The latter at least is
> wrong.

For the former, I mean that I'm used to create something that has "no
rights" to other people by default. Then I give the rights I want, and if
I don't give anything, then nothing is given by default. That's my
idea of security by default.

The current status with postgresql is that some rights are given by
default, so I have to fix everything by hand with revoke (I'm pretty
sure I'll forget something) and then grant what I want. I'll never
grant anything to "public", but rather to some groups.

As I can't and don't want to make all people share my point of view, I
would need some parametrizable default setting, so that I can at least
share my point of view with myself;-)

Also maybe the default may be different and still hardwired for system
stuffs.

A still better fix for me would be that default public rights are the
most restrictive, as some comments suggest it could be the case:

case ACL_OBJECT_FUNCTION:
/* Grant EXECUTE by default, for now */
^^^^^^^
world_default = ACL_EXECUTE;
...
case ACL_OBJECT_LANGUAGE:
/* Grant USAGE by default, for now */
world_default = ACL_USAGE;

The patch would be quick;-)

Have a nice day,

--
Fabien COELHO _ http://www.cri.ensmp.fr/~coelho _ Fabien(dot)Coelho(at)ensmp(dot)fr
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