Re: [HACKERS] New Developer's FAQ item

>
>    > Is all this relevant for writing triggers that have to access tables
>    > in order to verify/modify a given tuple?  Is that even possible?  Are
>    > there any examples?
>
>        But keep in mind that the syscache and heap access goes
>        in without ACL checks!
>
> I don't quite know what you mean here.  What are ACL checks?  Sorry
> for the naive question.
>
> Cheers,
> Brook

    On  any  table,  the owner or a superuser can GRANT or REVOKE
    access to or from other users. Thus, you might  have  granted
    another user permissions to read some of your tables, but not
    other ones.  The permissions you've setup  are  held  in  the
    relacl column in pg_class.

    But  these permissions are checked only if a regular query is
    processed by the executor (or after  my  new  changes  during
    query  rewrite).   When  accessing  information  through  the
    syscache or heap access methods, the  ACL's  (access  control
    lists) aren't checked.

    If  you  write  a  function,  that  reads  tables and returns
    information from them, any user can use  these  functions  to
    see  the data they return. Even if you explicitly revoked the
    user from reading these tables. If the function uses  SPI  to
    access  the tables, the ACL checks get performed and the user
    cannot use them to look at your data.


Jan

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