Re: Proof of concept: standalone backend with full FE/BE protocol

Noah Misch <noah(at)leadboat(dot)com> writes:
> On Sun, Sep 02, 2012 at 11:34:42PM -0400, Tom Lane wrote:
>> Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
>>> Are there security issues with this? If a user can specify libpq
>>> connection options, he can now execute any file he wants by passing it
>>> as standalone_backend.

>> Hmm, that's a good point. Maybe we should only allow the executable
>> name to come from an environment variable? Seems kinda klugy though.

> I don't think it's libpq's job to enforce security policy this way. In any
> event, it has no reason to presume an environment variable is a safer source.

One easy thing we could do that would at least narrow the risks is to
only allow the executable's *directory* to be specified, hardwiring the
executable file name to "postgres" (or "postgres.exe" I guess).

I'm inclined to think though that environment variables *are* more
secure in this context. In the contrib/dblink example, such a
restriction would certainly help a lot. In any case, we should at
least think of a way that an app using libpq can prevent this type
of attack short of parsing the conn string for itself.

regards, tom lane