From 8595ae99f9dad524fbf0816ff6528343e7dc4190 Mon Sep 17 00:00:00 2001
From: op <op@openbsd.org>
Date: Wed, 8 Apr 2026 12:04:56 +0000
Subject: [PATCH] EHLO must reset the transaction
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RFC5321 §4.1.4 states that an EHLO command MAY be issued by a client
later in the session and, if it's acceptable, it MUST clear all buffers
and reset the state exactly as if a RSET command was issued.

discussed with / okay martijn@
---
 usr.sbin/smtpd/smtp_session.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/usr.sbin/smtpd/smtp_session.c b/usr.sbin/smtpd/smtp_session.c
index 00bac7ede04..8fa48d6c635 100644
--- a/usr.sbin/smtpd/smtp_session.c
+++ b/usr.sbin/smtpd/smtp_session.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: smtp_session.c,v 1.447 2026/03/26 18:43:40 op Exp $	*/
+/*	$OpenBSD: smtp_session.c,v 1.448 2026/04/08 12:04:56 op Exp $	*/
 
 /*
  * Copyright (c) 2008 Gilles Chehade <gilles@poolp.org>
@@ -1422,13 +1422,6 @@ smtp_check_ehlo(struct smtp_session *s, const char *args)
 		return 0;
 	}
 
-	if (s->helo[0]) {
-		smtp_reply(s, "503 %s %s: Already identified",
-		    esc_code(ESC_STATUS_PERMFAIL, ESC_INVALID_COMMAND),
-		    esc_description(ESC_INVALID_COMMAND));
-		return 0;
-	}
-
 	if (args == NULL) {
 		smtp_reply(s, "501 %s %s: EHLO requires domain name",
 		    esc_code(ESC_STATUS_PERMFAIL, ESC_INVALID_COMMAND),
@@ -1770,6 +1763,13 @@ smtp_proceed_ehlo(struct smtp_session *s, const char *args)
 	s->flags |= SF_EHLO;
 	s->flags |= SF_8BITMIME;
 
+	/* EHLO should behave like a RSET */
+	if (s->tx) {
+		if (s->tx->msgid)
+			smtp_tx_rollback(s->tx);
+		smtp_tx_free(s->tx);
+	}
+
 	smtp_report_link_identify(s, "EHLO", s->helo);
 
 	smtp_enter_state(s, STATE_HELO);