On Wed, Nov 17, 2010 at 05:24:12PM +0000, George Forman wrote:
>
> The scenario is as follows (see log snipet below for sequence details):
> The client MTA attempts to send a message. On the DOT command, Postfix
> returns: '451 4.3.0 Error: queue file write error'
This happens when a milter malfunctions. Check your logs, they contain
lots of relevant details.
> The client MTA sends a RSET command. Postfix responds with '503 5.7.0
> Error: access denied'
Postfix is intended to disconnect with a:
421 4.3.0 Mail system error
The code in question:
if (smtpd_milters != 0 && (state->err & CLEANUP_STAT_WRITE) != 0)
state->access_denied = mystrdup("421 4.3.0 Mail system error");
does not have the intended effect.
> The client MTA ignores the RSET response (based on RFC2821).
It should not ignore a 5XX return code from RSET. It should disconnect.
> The client MTA sends MAIL FROM command. Postfix responds with '503 5.7.0
> Error: access denied'
The client is wrong to keep re-using a session after a 5XX error on RSET.
> My analysis has shown the Postfix's milter interface fails when waiting
> for a response.
More likely, the milter, not the interface, but this is what I
expected before getting this far in your post.
> I am still actively investigating specifically the vstream event that
> triggers CLEANUP_STAT_WRITE to be returned.
Most likely a milter failed. Look in the logs!
> My QUICK FIX was to modify the 503 to a 521 error code in smtpd.c
> (smtpd_proto function).
> I am looking for suggestions on a longer term solution.
> I have made a change in smtpd_proto function:
>
> New code:
> /* XXX We use the real client for connect access control. */
> if (state->access_denied &&
> (! (cmdp->action == quit_cmd || cmdp->action == rset_cmd))) {
> smtpd_chat_reply(state, "%s", state->access_denied);
> state->error_count++;
> continue;
> }
No, RFC 2821/5321 notwithstanding, Postfix must reject RSET, to give
clients a chance to disconnect before before real mail is rejected.
So DO NOT exempt "rset_cmd". Otherwise, the change makes sense. Postfix
gives the intended response after "." (Queue file write error) and
the next command if any (say RSET) triggers a "421" disconnect.
--
Viktor.
