nixos-config/modules/mailserver/postfix.nix

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# SPDX-FileCopyrightText: 2021-2024 Simon Bruder <simon@sbruder.de>
#
# SPDX-License-Identifier: AGPL-3.0-or-later
{ config, lib, pkgs, ... }:
let
cfg = config.sbruder.mailserver;
listToString = lib.concatStringsSep ",";
# List of attribute sets with single key-value pair
plainAliases = (lib.flatten
(map
({ address, aliases, ... }:
map
(alias: { "${alias}" = address; })
(aliases ++ lib.singleton address))
cfg.users));
# Attribute set with every alias mapped to a list of receivers
mergedAliases = (lib.attrsets.foldAttrs
(val: col: lib.singleton val ++ col)
[ ]
plainAliases);
# Contents of the aliases file
aliasesString = (lib.concatStringsSep
"\n"
(lib.mapAttrsToList
(alias: addresses: "${alias} ${listToString addresses}")
mergedAliases));
valiases = pkgs.writeText "valiases" aliasesString;
submissionHeaderCleanupRules = pkgs.writeText "submission_header_cleanup_rules"
(lib.concatMapStringsSep
"\n"
(regex: "${regex} IGNORE")
cfg.cleanHeaders);
in
lib.mkIf cfg.enable {
services.postfix = {
enable = true;
enableSubmission = true; # plain/STARTTLS (latter is forced in submissionOptions)
enableSubmissions = true; # submission with implicit TLS (TCP/465)
hostname = cfg.fqdn;
networksStyle = "host";
sslCert = "${cfg.certDir}/fullchain.pem";
sslKey = "${cfg.certDir}/key.pem";
recipientDelimiter = "+";
mapFiles = {
inherit valiases;
};
config = {
# General
smtpd_banner = "${cfg.fqdn} ESMTP NO UCE";
disable_vrfy_command = true; # disable check if mailbox exists
enable_long_queue_ids = true; # better for debugging
strict_rfc821_envelopes = true; # only accept properly formatted envelope
message_size_limit = "50331648"; # 48MiB
virtual_mailbox_domains = listToString cfg.domains;
virtual_mailbox_maps = "hash:/var/lib/postfix/conf/valiases";
virtual_alias_maps = "hash:/var/lib/postfix/conf/valiases";
virtual_transport = "lmtp:unix:/run/dovecot2/dovecot-lmtp";
smtpd_recipient_restrictions = listToString [
"reject_non_fqdn_recipient"
"reject_rbl_client ix.dnsbl.manitu.net"
"reject_unknown_recipient_domain"
"reject_unverified_recipient"
];
smtpd_client_restrictions = listToString [
"reject_rbl_client ix.dnsbl.manitu.net"
"reject_unknown_client_hostname"
];
smtpd_sender_restrictions = listToString [
"reject_non_fqdn_sender"
"reject_unknown_sender_domain"
];
# generated 2021-02-04, Mozilla Guideline v5.6, Postfix 3.5.6, OpenSSL 1.1.1i, intermediate configuration
# https://ssl-config.mozilla.org/#server=postfix&version=3.5.6&config=intermediate&openssl=1.1.1i&guideline=5.6
smtpd_tls_security_level = "may";
smtpd_tls_auth_only = "yes";
smtpd_tls_mandatory_protocols = "!SSLv2, !SSLv3, !TLSv1, !TLSv1.1";
smtpd_tls_protocols = "!SSLv2, !SSLv3, !TLSv1, !TLSv1.1";
smtpd_tls_mandatory_ciphers = "medium";
smtpd_tls_loglevel = "1";
smtpd_tls_received_header = "yes"; # add TLS connection details to Received header
tls_medium_cipherlist = listToString [
"ECDHE-ECDSA-AES128-GCM-SHA256"
"ECDHE-RSA-AES128-GCM-SHA256"
"ECDHE-ECDSA-AES256-GCM-SHA384"
"ECDHE-RSA-AES256-GCM-SHA384"
"ECDHE-ECDSA-CHACHA20-POLY1305"
"ECDHE-RSA-CHACHA20-POLY1305"
"DHE-RSA-AES128-GCM-SHA256"
"DHE-RSA-AES256-GCM-SHA384"
];
tls_preempt_cipherlist = "no";
};
# plain/STARTTLS (forced with smtpd_tls_security_level)
submissionOptions = {
smtpd_tls_security_level = "encrypt";
smtpd_sasl_auth_enable = "yes";
smtpd_sasl_type = "dovecot";
smtpd_sasl_path = "/run/dovecot2/auth";
smtpd_sender_login_maps = "hash:/etc/postfix/valiases";
smtpd_recipient_restrictions = listToString [ ];
smtpd_client_restrictions = listToString [
"permit_sasl_authenticated"
"reject"
];
smtpd_sender_restrictions = listToString [
"reject_sender_login_mismatch"
];
cleanup_service_name = "submission-header-cleanup";
};
# implicit TLS
submissionsOptions = config.services.postfix.submissionOptions;
masterConfig = {
2023-08-18 15:15:07 +02:00
# Postscreen
smtpd = {
type = "pass";
args = [ "-o" "smtpd_discard_ehlo_keywords=silent-discard,dsn" ];
2023-08-18 15:15:07 +02:00
};
smtp_inet = {
# Partially overrides upstream
name = "smtp";
type = "inet";
private = false;
command = lib.mkForce "postscreen";
maxproc = 1;
};
tlsproxy = {
maxproc = 0;
};
dnsblog = {
maxproc = 0;
};
# Heder cleanup
submission-header-cleanup = {
private = false;
maxproc = 0;
command = "cleanup";
args = [ "-o" "header_checks=pcre:${submissionHeaderCleanupRules}" ];
};
};
};
networking.firewall.allowedTCPPorts = [
25 # SMTP
587 # SMTP submission
465 # SMTP submission (implicit TLS)
];
systemd.services.postfix = {
wants = [ "acme-finished-${cfg.fqdn}.target" ];
requires = [ "dovecot2.service" ];
after = [ "acme-finished-${cfg.fqdn}.target" "dovecot2.service" ];
};
security.acme.certs."${cfg.fqdn}".postRun = ''
if systemctl is-active postfix; then
systemctl --no-block reload postfix
fi
'';
}