Re: [EXT]: Re: BUG #18604: Regression in PostgreSQL 16.4: pg_dump Prevents Essential System Table Modifications

On Fri, 2024-09-06 at 20:46 +0000, Basha wrote:
> Please find below the details as what system catalog modifications were done and why.
> 
> We provide our customers with access to their respective representative databases
> (Rep DB) within a multi-tenant PostgreSQL architecture. Each customer is assigned
> their own dedicated database, and for each database, a corresponding role is created
> with the necessary permissions.
> 
> For example, for customers such as:
> Abc
> Def
> Xyz
> 
> the below user-roles:
> 
> Abc_usr for the Abc database
> Def_usr for the Def database
> Xyz_usr for the Xyz database
> 
> These roles are configured to have 'connect' privileges solely to their respective
> databases, ensuring isolation. For instance, only Abc_usr can connect to the Abc
> database, and this applies similarly to other users and databases.
> 
> To enhance security and prevent customers from viewing other database names in the
> system, we made modifications to the PostgreSQL system tables and created custom
> views that restrict the visibility of databases for each user.
> 
> Below are the changes
> 
> Step1 :
> Set the config allow_system_table_mods = on
> 
> Step 2:
> ALTER TABLE pg_catalog.pg_database RENAME TO pg_database_catalog;
> 
> Step3:
> 
> CREATE OR REPLACE VIEW pg_catalog.pg_database
>  AS
>  SELECT oid,
>     datname,
>     datdba,
>     encoding,
>     datlocprovider,
>     datistemplate,
>     datallowconn,
>     datconnlimit,
>     datfrozenxid,
>     datminmxid,
>     dattablespace,
>     datcollate,
>     datctype,
>     daticulocale,
>     daticurules,
>     datcollversion,
>     datacl,
>     1262::oid AS tableoid
>    FROM pg_database_catalog
>   WHERE 1 = 1 AND has_database_privilege(oid, 'connect'::text);

Such modifications are not supported.
I don't see why we should cater for that.

Yours,
Laurenz Albe