On Mon, Oct 17, 2016 at 10:51 PM, Robert Haas <robertmhaas@gmail.com> wrote: > On Mon, Oct 17, 2016 at 2:18 AM, Michael Paquier > <michael.paquier@gmail.com> wrote: >> On Mon, Oct 17, 2016 at 3:33 AM, Jeff Janes <jeff.janes@gmail.com> wrote: >>> postgres_fdw has some checks to enforce that non-superusers must connect to >>> the foreign server with a password-based method. The reason for this is to >>> prevent the authentication to the foreign server from happening on the basis >>> of the OS user who is running the non-foreign server. >>> >>> But I think these super user checks should be run against the userid of the >>> USER MAPPING being used for the connection, not the userid of currently >>> logged on user. >> >> So, if the user mapping user is a superuser locally, this would allow >> any lambda user of the local server to attempt a connection to the >> remote server. It looks dangerous rather dangerous to me to authorize >> that, even if the current behavior is a bit inconsistent I agree. > > I don't know what "any lambda user" means. Did you mean to write "any > random user"?
Yes, in this context that would be "any non-superuser" or "any user without superuser rights". Actually that's a French-ism. I just translated it naturally to English to define a user that has no access to advanced features :)
Thanks for the patch, but it breaking the existing functionality as per the other
mails. Marked as "returned with feedback" in 2016-11 commitfest.
Here is an updated patch. This version allows you use the password-less connection if you either are the super-user directly (which is the existing committed behavior), or if you are using the super-user's mapping because you are querying a super-user-owned view which you have been granted access to.
It first I thought the currently committed behavior might be a security bug as a directly logged in superuser can use another user's user-defined mapping but without the password restriction when querying a view made by someone else. But consulting with the security list nearly a year ago, the conclusion was that it is never a good idea for a superuser to blindly query from other users' views, and that the current situation is no worse for postgres_fdw than it is for other features, and so nothing needs to be done about it. So that is why I've decided to allow the passwordless solution in either situation--a superuser using someone else mapping, or someone else using a super user's mapping.
I didn't update any comments because the existing ones seem to apply equally well to the new code as the old code.
The regression test passes with this version because I still allow the old behavior. I didn't add a new test to also test the new behavior, because I don't know how to do that with the existing make check framework, and a TAP test seems like overkill.