mail/opensmtpd-filter-dkimsign: DKIM filter for OpenSMTPd

This filter adds a DKIM signature to emails sent through OpenSMTPd.
The rsa and ed25519 signing algorithms are supported, as well as the
simple and relaxed canonicalization algorithms.

The filter can sign emails for several domains, selecting them
according to the from-header, but can only use a single selector,
managing multiple selectors must be done at the OpenSMTPd level.

It depends on the libopensmtpd port.

An example of a minimal configuration for signing outgoing emails for
domain "example.com" and selector "_selector" would be:

filter "dkimsign" proc-exec "filter-dkimsign -d example.com -s _selector \
    -k /usr/local/etc/smtpd/dkim/private.key" user _smtpd group _smtpd

And then you can apply that filter to the mail that needs to be signed:

listen on lo0 filter dkimsign

WWW: https://imperialat.at/dev/filter-dkimsign/

PR:		283823

4 files changed, 60 insertions, 0 deletions

diff --git a/mail/Makefile b/mail/Makefile
index aba4803ad97c..092979a16662 100644
--- a/mail/Makefile
+++ b/mail/Makefile
@@ -290,6 +290,7 @@
     SUBDIR += opensmtpd-extras-table-redis
     SUBDIR += opensmtpd-extras-table-socketmap
     SUBDIR += opensmtpd-extras-table-sqlite
+    SUBDIR += opensmtpd-filter-dkimsign
     SUBDIR += opensmtpd-filter-rspamd
     SUBDIR += opensmtpd-filter-senderscore
     SUBDIR += opensmtpd-table-sqlite
diff --git a/mail/opensmtpd-filter-dkimsign/Makefile b/mail/opensmtpd-filter-dkimsign/Makefile
new file mode 100644
index 000000000000..802c3786498c
--- /dev/null
+++ b/mail/opensmtpd-filter-dkimsign/Makefile
@@ -0,0 +1,36 @@
+PORTNAME=	filter-dkimsign
+DISTVERSION=	0.5
+CATEGORIES=	mail
+MASTER_SITES=	https://imperialat.at/releases/
+PKGNAMEPREFIX=	opensmtpd-
+
+MAINTAINER=	mvalleton@seos.fr
+COMMENT=	Library for writing opensmtpd filters
+WWW=		https://imperialat.at/dev/filter-dkimsign/
+
+LICENSE=	ISCL
+LICENSE_FILE=	${WRKSRC}/LICENSE
+
+LIB_DEPENDS=	libevent.so:devel/libevent \
+		libopensmtpd.so:mail/libopensmtpd
+
+MAKEFILE=	Makefile.gnu
+USES=		gmake localbase ssl
+PLIST_FILES=	libexec/opensmtpd/filter-dkimsign \
+		share/man/man8/filter-dkimsign.8.gz
+
+# LDFLAGS used by gmake during build
+# MANDIR and BINDIR used by make during install
+MAKE_ARGS=	BINDIR=${LOCALBASE}/libexec/opensmtpd \
+		MANDIR=${LOCALBASE}/share/man/man \
+		MK_DEBUG_FILES=no
+
+# Makefile.gnu's install target uses Linux-specific install options so we
+# have to use the OpenBSD Makefile instead. Thus, it's easier to just do
+# it manually.
+do-install:
+	${MKDIR} ${STAGEDIR}${PREFIX}/libexec/opensmtpd
+	${INSTALL_PROGRAM} ${WRKSRC}/filter-dkimsign ${STAGEDIR}${PREFIX}/libexec/opensmtpd/
+	${INSTALL_MAN} ${WRKSRC}/filter-dkimsign.8.gz ${STAGEDIR}${PREFIX}/share/man/man8
+
+.include <bsd.port.mk>
diff --git a/mail/opensmtpd-filter-dkimsign/distinfo b/mail/opensmtpd-filter-dkimsign/distinfo
new file mode 100644
index 000000000000..f89f58056d2c
--- /dev/null
+++ b/mail/opensmtpd-filter-dkimsign/distinfo
@@ -0,0 +1,3 @@
+TIMESTAMP = 1735833837
+SHA256 (filter-dkimsign-0.5.tar.gz) = a5b4ec3af5ecb42351a0b5459bdd0f32c00ec55c23050b5f46dfaed8e321974b
+SIZE (filter-dkimsign-0.5.tar.gz) = 23709
diff --git a/mail/opensmtpd-filter-dkimsign/pkg-descr b/mail/opensmtpd-filter-dkimsign/pkg-descr
new file mode 100644
index 000000000000..2096b86e4bb6
--- /dev/null
+++ b/mail/opensmtpd-filter-dkimsign/pkg-descr
@@ -0,0 +1,20 @@
+This filter adds a DKIM signature to emails sent through OpenSMTPd.
+The rsa and ed25519 signing algorithms are supported, as well as the
+simple and relaxed canonicalization algorithms.
+
+The filter can sign emails for several domains, selecting them
+according to the from-header, but can only use a single selector,
+managing multiple selectors must be done at the OpenSMTPd level.
+
+It depends on the libopensmtpd port.
+
+
+An example of a minimal configuration for signing outgoing emails for
+domain "example.com" and selector "_selector" would be:
+
+filter "dkimsign" proc-exec "filter-dkimsign -d example.com -s _selector \
+    -k /usr/local/etc/smtpd/dkim/private.key" user _smtpd group _smtpd
+
+And then you can apply that filter to the mail that needs to be signed:
+
+listen on lo0 filter dkimsign