From 7727cc8b9e981c2969b0ac1519f964cfb8b90126 Mon Sep 17 00:00:00 2001
From: "Rob Swindell (on Debian Linux)" <rob@synchro.net>
Date: Thu, 2 Mar 2023 01:04:56 -0800
Subject: [PATCH] Fix false FORGED mail header 'FROM' field detection/rejection
Pretty much any From field that contains an '@' in the username portion
was subject to comparison to the full email address, but clearly some of
these rejected emails were not forge attempts:
'Chris @ StubHub' vs 'events@mail.stubhub.com'
'Eric S. Raymond (@esr)' vs 'gitlab@mg.gitlab.com'
Fixed by requiring that the sender name is actually a well-formed Internet
email address using smb_netaddr_type(), which was also recently improved to
be more accurate.
Unrelated change: include reverse-path (email address for bounces) in
ILLEGALLY-LONG body and header line log messages (usually SPAM from what
I can tell).
---
src/sbbs3/mailsrvr.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/src/sbbs3/mailsrvr.c b/src/sbbs3/mailsrvr.c
index 89520f4a29..bac9ec9f45 100644
--- a/src/sbbs3/mailsrvr.c
+++ b/src/sbbs3/mailsrvr.c
@@ -3643,7 +3643,7 @@ static void smtp_thread(void* arg)
continue;
}
if(relay_user.number == 0
- && strchr(sender, '@') != NULL
+ && smb_netaddr_type(sender) == NET_INTERNET
&& compare_addrs(sender, sender_addr) != 0) {
lprintf(LOG_WARNING,"%04d %s %s !FORGED mail header 'FROM' field ('%s' vs '%s', %lu total)"
,socket, client.protocol, client_id, sender, sender_addr, ++stats.msgs_refused);
@@ -4073,8 +4073,8 @@ static void smtp_thread(void* arg)
p=buf;
if(*p=='.') p++; /* Transparency (RFC821 4.5.2) */
if(strlen(p) > RFC822_MAX_LINE_LEN) {
- lprintf(LOG_WARNING, "%04d %s %s sent an ILLEGALLY-LONG body line (%d chars > %d): '%s'"
- ,socket, client.protocol, client_id, (int)strlen(p), RFC822_MAX_LINE_LEN, p);
+ lprintf(LOG_WARNING, "%04d %s %s !%s sent an ILLEGALLY-LONG body line (%d chars > %d): '%s'"
+ ,socket, client.protocol, client_id, reverse_path, (int)strlen(p), RFC822_MAX_LINE_LEN, p);
sockprintf(socket, client.protocol, session, "500 Line too long (body)");
break;
}
@@ -4090,8 +4090,8 @@ static void smtp_thread(void* arg)
}
/* RFC822 Header parsing */
if(strlen(buf) > RFC822_MAX_LINE_LEN) {
- lprintf(LOG_WARNING, "%04d %s %s sent an ILLEGALLY-LONG header line (%d chars > %d): '%s'"
- ,socket, client.protocol, client_id, (int)strlen(buf), RFC822_MAX_LINE_LEN, buf);
+ lprintf(LOG_WARNING, "%04d %s %s !%s sent an ILLEGALLY-LONG header line (%d chars > %d): '%s'"
+ ,socket, client.protocol, client_id, reverse_path, (int)strlen(buf), RFC822_MAX_LINE_LEN, buf);
sockprintf(socket, client.protocol, session, "500 Line too long (header)");
break;
}
--
GitLab