Tom Lane writes: > Andres Freund <and...@2ndquadrant.com> writes:
> > One would be to use open(O_NOFOLLOW)? > > That would only stop symlink attacks, not hardlink variants; > and it'd probably stop some legitimate use-cases too. The creation of the hardlink is denied by the OS based on the attacker not having sufficient permissions to the target file. In principle the mentioned loophole is limited to a symlink, which is not restricted at create time. Thinking a bit more about the scenario of the malicious writer, I think the secure way to proceed for the superuser would be to set up two directories, one with write permissions to the producer of data, the other without. The superuser would have to move the file from the writable dir to the non-writable dir, before creating the foreign table. The file itself should remain writable by the uploader if it's live data. The data-producer has to be aware that updates happen at a different path than uploads. The problem is that it's really not intuitive. I can imagine unaware admins implementing the insecure process without a second thought. By contrast, if symlinks were followed only optionally, it would be safer as a default choice and the installations that need symlinks could still use something like: CREATE FOREIGN TABLE (...) SERVER name OPTIONS (symlink_allowed 'on', filename '/path/to/file', ...) The mere existence of the option is a hint that there are consequences to consider. Best regards, -- Daniel Vérité PostgreSQL-powered mail user agent and storage: http://www.manitou-mail.org -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
