Re: Security leak with trigger functions?

Added to TODO:

> * Tighten trigger permission checks
>
> http://archives.postgresql.org/pgsql-hackers/2006-12/msg00564.php

and:

> * Tighten function permission checks
>
> http://archives.postgresql.org/pgsql-hackers/2006-12/msg00568.php
>

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Tom Lane wrote:
> "Florian G. Pflug" <fgp(at)phlo(dot)org> writes:
> > Is this true for on-select rules too? In that case, couldn't any
> > user run his code as postmaster by creating an appropriate on-select
> > rule and waiting until somebody/cron backups the database using pg_dump?
>
> I don't see any issue for views' on-select rules; they wouldn't get
> executed during either dump or reload.
>
> It does seem like there are some other potential hazards once you start
> thinking this way:
>
> * Datatype I/O functions: the output function will be run as superuser
> during pg_dump, and the input function during restore. I think this is
> not an attack spot today because I/O functions can only be written in
> C, but we'd have to think about the consequences before allowing I/O
> functions in trusted P/L languages. (Perhaps arrange for I/O functions
> to be run as if setuid to their owner? Could be expensive...)
>
> * Functions associated with indexes would get run during restore:
> both the datatype-related index support functions, and any functions
> used in functional indexes. This might be OK because we require
> such functions to be immutable, but I do not think the link from
> "immutable" to "can't write database" is currently air-tight.
>
> * Functions in CHECK constraints (either table or domain constraints)
> would be executed during restores. There is not an immutability
> constraint for these currently, although arguably it'd be reasonable
> to require?
>
> * Trigger functions: not executed during pg_dump, nor during a full
> restore, but they *would* be executed during a data-only restore if
> you'd not used --disable-triggers.
>
> * ON INSERT rules: likewise, executed during data-only restores,
> possibly resulting in execution of user-defined functions.
>
> During restores, we normally set the userid to be the table owner while
> loading data into a particular table, which would mostly close these
> holes except that I think a function can revert the session
> authorization to be whatever the outermost user id is. Probably we need
> to tighten up the conditions under which a SET SESSION AUTHORIZATION can
> be reverted within a function.
>
> regards, tom lane
>
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