On 7/30/17 1:23 PM, Bill Cole wrote:
On 29 Jul 2017, at 23:30, deoren wrote:
On 7/29/17 4:31 PM, Bill Cole wrote:
[...]
Using 'OK' in check_sender_access for white;listing isn't wrong, it's
just imperfect and can be risky. It is trivial to forge the SMTP
sender address, so absent additional measures applied AFTER
smtpd_recipient_restrictions (such as replicating the
reject_rbl_client rules in smtpd_relay_restrictions) your 'OK'
whitelisting makes you an open relay for anyone forging the exempted
address or domain.
So if I return 'OK' within smtpd_recipient_restrictions, will these
rules within smtpd_relay_restrictions be sufficient to prevent
granting them relay access? I was under the impression that it was?
smtpd_relay_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination,
Yes. As always, Dr. Venema knows more than anyone about Postfix and his
recommendation was much more concise and complete than mine:
reject_unauth_destination before any access map used as a whitelist
prevents the whitelisting from opening a relay hole.
[...]
So far so good, aside from various points of ignorance like the one
you helped clear up for me. I still have much to learn.
True for us all, aside from those who actually write the code.
Thanks again for your help. Your explanation really helped me understand
the details. Sometimes hearing the same thing said a different way
finally makes everything you've heard/read "click".
