On Sun, 2008-03-23 at 10:50 -0700, Ned Freed wrote:
Also a good point. I have added:
The remote-host environment item defined in this specification is usually
determined by performing a PTR DNS lookup on the client IP address. This
information may come from an untrusted source. For example, the test:
if environment :matches "remote-host" "*.mydomain.com" { ... }
is not a good way to test whether the message came from 'outside' becaus
anyone who can create a PTR record can create one that refers to whatever
domain they choose.
[...]
I think a simpler way to handle this is to say that the name will
be blank if it cannot be resolved into a host name. How about:
"remote-host"
=> Host name of remote SMTP/LMTP/Submission client, if
applicable and available. The empty string will be returned
if for some reason this information cannot be obtained for
the current client.
sorry, I don't understand what this means. is the existence of a PTR
record sufficient?
Who knows? The mechanism used to obtian the remote-host isn't (and should not
be) specified. As such, a PTR could be sufficient. Or it may not be - some
systems do a backwards-forwards check. And there can even be cases when a PTR
record isn't needed - DNS names aren't the only game in town, you know.
it seems so, given the above added caveat. if so --
how is a script able to detect a forgery?
It can't. That's the point.
Ned