On Fri, Jan 16, 2015 at 12:52:46AM +0000, Jeremy Harris wrote:
> Most of the attributes look ok for us to support. I'm dubious
> about the LOGIN one though; this feels like a protocol level
> violation.
In Postfix this allows proxying of SASL logins. A proxy might
handle SASL auth in front of the MTA. The MTA receives the SASL
login name as determined by the proxy and applies access control
decisions accordingly.
> Is that Postfix page the sole definition of the ESMTP option?
I think so, that's why it is perhaps time for an IETF draft, the
feature seems to have caught on far beyond Postfix. Not sure
whether the I-D should be informational or standards-track. XCLIENT
is a local matter between various load-balancer systems and the
MTA behind them, and is not generally a concern across indepedently
operated systems. So informational might be less work, and still
get the job done.
> I note it doesn't specify the format of an IP address
> (there is an example of an IPv4 one).
Quoting XCLIENT_README:
The ADDR attribute specifies an SMTP client numerical IPv4
network address, an IPv6 address prefixed with IPV6:, or
[UNAVAILABLE] when the address information is unavailable.
Address information is not enclosed with [].
Thus one of the three forms:
192.0.2.1
IPv6:2001:db8::1
[UNAVAILABLE]
> Swaks supports it, and mentions another (undocumented!)
> attribute: REVERSE_NAME ...
> ( http://www.jetmore.org/john/code/vmail/latest/doc/ref.txt )
It does looks like XCLIENT_README omits that attribute which was
added more recently. The full list is:
#define XCLIENT_NAME "NAME" /* client name */
#define XCLIENT_REVERSE_NAME "REVERSE_NAME" /* reverse client name */
#define XCLIENT_ADDR "ADDR" /* client address */
#define XCLIENT_PORT "PORT" /* client port */
#define XCLIENT_PROTO "PROTO" /* client protocol */
#define XCLIENT_HELO "HELO" /* client helo */
#define XCLIENT_LOGIN "LOGIN" /* SASL login name */
The REVERSE_NAME is the unverified result of of a PTR lookup.
While NAME is the FCrDNS. These are of course not always available
to the proxy.
--
Viktor.
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