git » chasquid » commit 45bc70e

smtpsrv: Fix "Received" header format when including the IP address

author Alberto Bertogli
2025-10-02 09:45:26 UTC
committer Alberto Bertogli
2025-10-02 09:45:26 UTC
parent eeb2deb7f608372ce20920a0dfd843162b2d191e
smtpsrv: Fix "Received" header format when including the IP address

When constructing the "Received" header, in some cases we want to
include the remote IP address in addition to the EHLO domain.

The way we did that is not fully compliant with RFC 5321 (section 4.4),
and this has the potential to confuse some tools that parse the header.

This patch fixes this problem by adjusting the order of the two pieces
of data, which makes it comply with the RFC.

Before:

  Received: from [1.2.3.4] (ehlo.domain.example.com)

After:

  Received: from ehlo.domain.example.com ([1.2.3.4])

Thanks to nolanl@github for reporting this problem in
https://github.com/albertito/chasquid/issues/76.
internal/smtpsrv/conn.go +4 -5 
diff --git a/internal/smtpsrv/conn.go b/internal/smtpsrv/conn.go
index af90d82..8a67e42 100644
--- a/internal/smtpsrv/conn.go
+++ b/internal/smtpsrv/conn.go
@@ -747,11 +747,10 @@ func (c *Conn) addReceivedHeader() {
 		// explicitly hide their network address.
 		received += fmt.Sprintf("from %s\n", c.ehloDomain)
 	} else {
-		// For non-authenticated users we show the real address as canonical,
-		// and then the given EHLO domain for convenience and
-		// troubleshooting.
-		received += fmt.Sprintf("from [%s] (%s)\n",
-			addrLiteral(c.remoteAddr), c.ehloDomain)
+		// For non-authenticated users we also include the network address,
+		// for convenience and troubleshooting.
+		received += fmt.Sprintf("from %s ([%s])\n",
+			c.ehloDomain, addrLiteral(c.remoteAddr))
 	}
 
 	received += fmt.Sprintf("by %s (chasquid) ", c.hostname)