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# nixos-mailserver: a simple mail server
# Copyright (C) 2016-2018 Robin Raymond
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>
{ config, pkgs, lib, ... }:
with (import ./common.nix { inherit config lib; });
let
inherit (lib.strings) concatStringsSep;
cfg = config.mailserver;
# valiases_postfix :: [ String ]
valiases_postfix = lib.flatten (lib.mapAttrsToList
(name: value:
let to = name;
in map (from: "${from} ${to}") (value.aliases ++ lib.singleton name))
cfg.loginAccounts);
# catchAllPostfix :: [ String ]
catchAllPostfix = lib.flatten (lib.mapAttrsToList
(name: value:
let to = name;
in map (from: "@${from} ${to}") value.catchAll)
cfg.loginAccounts);
# extra_valiases_postfix :: [ String ]
extra_valiases_postfix =
(map
(from:
let to = cfg.extraVirtualAliases.${from};
aliasList = (l: let aliasStr = builtins.foldl' (x: y: x + y + ", ") "" l;
in builtins.substring 0 (builtins.stringLength aliasStr - 2) aliasStr);
in if (builtins.isList to) then "${from} " + (aliasList to)
else "${from} ${to}")
(builtins.attrNames cfg.extraVirtualAliases));
# all_valiases_postfix :: [ String ]
all_valiases_postfix = valiases_postfix ++ extra_valiases_postfix;
# valiases_file :: Path
valiases_file = builtins.toFile "valias"
(lib.concatStringsSep "\n" (all_valiases_postfix ++
catchAllPostfix));
reject_senders_postfix = (map
(sender:
"${sender} REJECT")
(cfg.rejectSender));
reject_senders_file = builtins.toFile "reject_senders" (lib.concatStringsSep "\n" (reject_senders_postfix)) ;
reject_recipients_postfix = (map
(recipient:
"${recipient} REJECT")
(cfg.rejectRecipients));
# rejectRecipients :: [ Path ]
reject_recipients_file = builtins.toFile "reject_recipients" (lib.concatStringsSep "\n" (reject_recipients_postfix)) ;
# vhosts_file :: Path
vhosts_file = builtins.toFile "vhosts" (concatStringsSep "\n" cfg.domains);
# vaccounts_file :: Path
# see
# https://blog.grimneko.de/2011/12/24/a-bunch-of-tips-for-improving-your-postfix-setup/
# for details on how this file looks. By using the same file as valiases,
# every alias is owned (uniquely) by its user.
# The user's own address is already in all_valiases_postfix.
vaccounts_file = builtins.toFile "vaccounts" (lib.concatStringsSep "\n" all_valiases_postfix);
submissionHeaderCleanupRules = pkgs.writeText "submission_header_cleanup_rules" (''
# Removes sensitive headers from mails handed in via the submission port.
# See https://thomas-leister.de/mailserver-debian-stretch/
# Uses "pcre" style regex.
/^Received:/ IGNORE
/^X-Originating-IP:/ IGNORE
/^X-Mailer:/ IGNORE
/^User-Agent:/ IGNORE
/^X-Enigmail:/ IGNORE
'' + lib.optionalString cfg.rewriteMessageId ''
# Replaces the user submitted hostname with the server's FQDN to hide the
# user's host or network.
/^Message-ID:\s+<(.*?)@.*?>/ REPLACE Message-ID: <$1@${cfg.fqdn}>
'');
inetSocket = addr: port: "inet:[${toString port}@${addr}]";
unixSocket = sock: "unix:${sock}";
smtpdMilters =
(lib.optional cfg.dkimSigning "unix:/run/opendkim/opendkim.sock")
++ [ "unix:/run/rspamd/rspamd-milter.sock" ];
policyd-spf = pkgs.writeText "policyd-spf.conf" (
cfg.policydSPFExtraConfig
+ (lib.optionalString cfg.debug ''
debugLevel = 4
''));
mappedFile = name: "hash:/var/lib/postfix/conf/${name}";
in
{
config = with cfg; lib.mkIf enable {
services.postfix = {
enable = true;
hostname = "${fqdn}";
networksStyle = "host";
mapFiles."valias" = valiases_file;
mapFiles."vaccounts" = vaccounts_file;
mapFiles."reject_senders" = reject_senders_file;
mapFiles."reject_recipients" = reject_recipients_file;
sslCert = certificatePath;
sslKey = keyPath;
enableSubmission = true;
virtual =
(lib.concatStringsSep "\n" (all_valiases_postfix ++ catchAllPostfix));
extraConfig =
''
# Extra Config
mydestination =
smtpd_banner = ${fqdn} ESMTP NO UCE
disable_vrfy_command = yes
message_size_limit = ${builtins.toString cfg.messageSizeLimit}
# virtual mail system
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
virtual_mailbox_base = ${mailDirectory}
virtual_mailbox_domains = ${vhosts_file}
virtual_mailbox_maps = ${mappedFile "valias"}
virtual_transport = lmtp:unix:/run/dovecot2/dovecot-lmtp
# sasl with dovecot
smtpd_sasl_type = dovecot
smtpd_sasl_path = /run/dovecot2/auth
smtpd_sasl_auth_enable = yes
smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
policy-spf_time_limit = 3600s
# reject selected senders
smtpd_sender_restrictions = check_sender_access ${mappedFile "reject_senders"}
# quota and spf checking
smtpd_recipient_restrictions =
check_recipient_access ${mappedFile "reject_recipients"},
check_policy_service inet:localhost:12340,
check_policy_service unix:private/policy-spf
# TLS settings, inspired by https://github.com/jeaye/nix-files
# Submission by mail clients is handled in submissionOptions
smtpd_tls_security_level = may
# strong might suffice and is computationally less expensive
smtpd_tls_eecdh_grade = ultra
# Disable predecessors to TLS
smtpd_tls_protocols = !SSLv2, !SSLv3
# Allowing AUTH on a non encrypted connection poses a security risk
smtpd_tls_auth_only = yes
# Log only a summary message on TLS handshake completion
smtpd_tls_loglevel = 1
# Disable weak ciphers as reported by https://ssl-tools.net
# https://serverfault.com/questions/744168/how-to-disable-rc4-on-postfix
smtpd_tls_exclude_ciphers = RC4, aNULL
smtp_tls_exclude_ciphers = RC4, aNULL
# Configure a non blocking source of randomness
tls_random_source = dev:/dev/urandom
smtpd_milters = ${lib.concatStringsSep "," smtpdMilters}
${lib.optionalString cfg.dkimSigning "non_smtpd_milters = unix:/run/opendkim/opendkim.sock"}
milter_protocol = 6
milter_mail_macros = i {mail_addr} {client_addr} {client_name} {auth_type} {auth_authen} {auth_author} {mail_addr} {mail_host} {mail_mailer}
'';
submissionOptions =
{
smtpd_tls_security_level = "encrypt";
smtpd_sasl_auth_enable = "yes";
smtpd_sasl_type = "dovecot";
smtpd_sasl_path = "/run/dovecot2/auth";
smtpd_sasl_security_options = "noanonymous";
smtpd_sasl_local_domain = "$myhostname";
smtpd_client_restrictions = "permit_sasl_authenticated,reject";
smtpd_sender_login_maps = "hash:/etc/postfix/vaccounts";
smtpd_sender_restrictions = "reject_sender_login_mismatch";
smtpd_recipient_restrictions = "reject_non_fqdn_recipient,reject_unknown_recipient_domain,permit_sasl_authenticated,reject";
cleanup_service_name = "submission-header-cleanup";
};
masterConfig = {
"policy-spf" = {
type = "unix";
privileged = true;
chroot = false;
command = "spawn";
args = [ "user=nobody" "argv=${pkgs.pypolicyd-spf}/bin/policyd-spf" "${policyd-spf}"];
};
"submission-header-cleanup" = {
type = "unix";
private = false;
chroot = false;
maxproc = 0;
command = "cleanup";
args = ["-o" "header_checks=pcre:${submissionHeaderCleanupRules}"];
};
};
};
};
}
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