Re: [PATCH] Largeobject access controls

2009/9/3 KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>:
> KaiGai Kohei wrote:
>> Alvaro Herrera wrote:
>>> Tom Lane wrote:
>>>> KaiGai Kohei <kaigai(at)kaigai(dot)gr(dot)jp> writes:
>>>>> BTW, currently, the default ACL of largeobject allows anything for owner
>>>>> and nothing for world. Do you have any comment for the default behavior?
>>>> Mph.  I think the backlash will be too great.  You have to leave the
>>>> default behavior the same as it is now, ie, world access.
>>> BTW as a default it is pretty bad.  Should we have a GUC var to set the
>>> default LO permissions?
>>
>> It seems to me a reasonable idea in direction.
>> However, it might be better to add a GUC variable to turn on/off LO
>> permission feature, not only default permissions.
>> It allows us to control whether the privilege mechanism should perform
>> in backward compatible, or not.
>
> Now we have two options:
>
> 1. A GUC variable to set the default largeobject permissions.
>
>  SET largeobject_default_acl = [ ro | rw | none ]
>    - ro   : read-only
>    - rw   : read-writable
>    - none : nothing
>
>  It can control the default acl which is applied when NULL is set on
>  the pg_largeobject_meta.lomacl. However, lo_unlink() checks ownership
>  on the largeobject, so it is not enough compatible with v8.4.x or prior.
>
> 2. A GUC veriable to turn on/off largeobject permissions.
>
>  SET largeobject_compat_dac = [ on | off ]
>
>  When the variable is turned on, largeobject dac permission check is
>  not applied as the v8.4.x or prior version did. So, the variable is
>  named "compat" which means compatible behavior.
>  It also does not check ownership on lo_unlink().
>
> My preference is the second approach.
>
> What's your opinion?

I prefer the first. There's little harm in letting users set the
default permissions for themselves, but a GUC that controls
system-wide behavior will have to be something only superusers can
money with, and that seems like it will reduce usability.

Why couldn't lo_unlink() just check write privilege?

...Robert