can't read SMFIC_* reply packet header: Success

[mattpr]

Using the HELO example from the project's readme with postfix...

postconf -e smtpd_milters=inet:localhost:9568

On the milter side I can see the "helo" getting logged, but postfix isn't happy with the ctx.continue() response....

warning: milter inet:localhost:9568: can't read SMFIC_HELO reply packet header: Success
NOQUEUE: milter-reject: EHLO from XXXXX.outbound.protection.outlook.com[XXXXXX]: 451 4.7.1 Service unavailable - try again later; proto=ESMTP helo=<NAM02-BN1-obe.outbound.protection.outlook.com>

fancier examples (looking at headers) result in same issue (postfix softfails the email with a 451)...

warning: milter inet:localhost:9568: can't read SMFIC_MAIL reply packet header: Success

I'll try to dig into it more later. Just posting here for reference.

[mattpr]

Okay. The issue is the following.

When milterjs receives an ABORT it ends the socket connection (FIN).

milterjs/index.js

Line 308 in 19f7153

ctx.socket.end();

...whereas the milter spec says this should reset the milter state to before HELO while leaving the connection open.

Resets internal state of milter program to before SMFIC_HELO, but keeps the connection open.

The milter spec also says:

The connection can be closed at any time by either side. If closed by
the MTA, the milter program should release all state information for the
previously established connection. If closed by the milter program
without first sending an accept or reject action message, the MTA will
take the default action for any message in progress (configurable to
ignore the milter program, or reject with a 4xx or 5xx error).

So the socket should not be closed by the milter end on ABORT (only SMFIC_QUIT).
That is the issue we see in my case. (optneg, macro:connect, connect, macro:helo, helo, abort, helo, milter:FIN).

Also milterjs does not handle socket.on('end', ...) so when the MTA closes the connection milterjs will end up with a crash when trying to write to the socket that was already closed.