* Robert Haas (robertmh...@gmail.com) wrote: > On Wed, Oct 29, 2014 at 10:52 AM, Andres Freund <and...@2ndquadrant.com> > wrote: > >> The larger point though is that this is just one of innumerable attack > >> routes for anyone with the ability to make the server do filesystem reads > >> or writes of his choosing. If you think that's something you can safely > >> give to people you don't trust enough to make them superusers, you are > >> wrong, and I don't particularly want to spend the next ten years trying > >> to wrap band-aids around your misjudgment. > > > > ... but that doesn't necessarily address this point. > > I think the question is "just how innumerable are those attack > routes"? So, we can prevent a symlink from being used via O_NOFOLLOW. > But what about hard links?
You can't hard link to files you don't own.
sfrost@tamriel:/home/sfrost> ln /home/archive/xx.tar.gz
ln: failed to create hard link ?./xx.tar.gz? => ?/home/archive/xx.tar.gz?:
Operation not permitted
> In general, the hazard is that an untrusted user can induce the user
> to read or write a file that the user in question could not have read
> or written himself. It's not clear to me whether it's reasonably
> possible to build a system that is robust against such attacks, or
> not.
There are certainly use-cases where the user executing the COPY doesn't
have any direct access to the filesystem at all but only through PG.
Taken to a bit of an extreme, you could say we already provide that
today. ;)
Thanks!
Stephen
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