I just visited http://www.postgresql.org/download/linux/debian/ and my
impression is that the way the signing key is published is not secured
against wrong origin or manipulation by a man in the middle (MitM) attacker.
Meaning, that if a MitM attacker can compromise downloads, he or she is
also able to compromise the documentation site including the source of
the signing key, e.g. by publishing the attacker's signing key to the
user. Debian's apt-get will not complain if everything fits together.
Therefore, I suggest that the whole page should be TLS secured
(HTTPS-only), not because of encryption but to ensure origin and
integrity of the signing key.
It is not sufficient to have the signing key itself TLS-secured, because
the documented hyperlink
https://www.postgresql.org/media/keys/ACCC4CF8.asc
could easily be manipulated by the MitM as well.
I also suggest to go through the documentation to find similar occurences.
Last, but not least, people might also tend to copy-paste some bash
commands which offers additional possibilities for MitM to let users
install malicious software with root permissions. In the long-run, I
suggest to go for a HTTPS-only strategy with PostgreSQL's documentation
(all of it).
Related, but securing the download:
http://www.postgresql.org/message-id/flat/1455875336.9107.60.camel@gunduz.org#1455875336.9107.60.camel@gunduz.org
Note that the apt repository (including the downloadable packages) does
not have to be TLS-secured as long as the package signing mechanism
works well. Still, the additional security might not be harmful for most
users.
Best regards
Thomas Mayer
--
https://www.2bis10.de