Re: Security leak with trigger functions?

"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