path: root/modules/private/mail/relay.nix

{ lib, pkgs, config, nodes, name, ... }:
{
  config = lib.mkIf config.myServices.mailBackup.enable {
    security.acme2.certs."mail" = config.myServices.certificates.certConfig // {
      postRun = ''
        systemctl restart postfix.service
        '';
      domain = config.hostEnv.fqdn;
      extraDomains = let
        zonesWithMx = builtins.filter (zone:
          lib.attrsets.hasAttr "withEmail" zone && lib.lists.length zone.withEmail > 0
        ) config.myEnv.dns.masterZones;
        mxs = map (zone: "${config.myEnv.servers."${name}".mx.subdomain}.${zone.name}") zonesWithMx;
      in builtins.listToAttrs (map (mx: lib.attrsets.nameValuePair mx null) mxs);
    };
    secrets.keys = [
      {
        dest = "postfix/mysql_alias_maps";
        user = config.services.postfix.user;
        group = config.services.postfix.group;
        permissions = "0440";
        text = ''
          # We need to specify that option to trigger ssl connection
          tls_ciphers = TLSv1.2
          user = ${config.myEnv.mail.postfix.mysql.user}
          password = ${config.myEnv.mail.postfix.mysql.password}
          hosts = ${config.myEnv.mail.postfix.mysql.remoteHost}
          dbname = ${config.myEnv.mail.postfix.mysql.database}
          query = SELECT DISTINCT 1
            FROM forwardings_merge
            WHERE
              ((regex = 1 AND '%s' REGEXP CONCAT('^',source,'$') ) OR (regex = 0 AND source = '%s'))
              AND active = 1
              AND '%s' NOT IN
              (
                SELECT source
                FROM forwardings_blacklisted
                WHERE source = '%s'
              ) UNION
              SELECT 'devnull@immae.eu'
              FROM forwardings_blacklisted
              WHERE source = '%s'
          '';
      }
      {
        dest = "postfix/mysql_mailbox_maps";
        user = config.services.postfix.user;
        group = config.services.postfix.group;
        permissions = "0440";
        text = ''
          # We need to specify that option to trigger ssl connection
          tls_ciphers = TLSv1.2
          user = ${config.myEnv.mail.postfix.mysql.user}
          password = ${config.myEnv.mail.postfix.mysql.password}
          hosts = ${config.myEnv.mail.postfix.mysql.remoteHost}
          dbname = ${config.myEnv.mail.postfix.mysql.database}
          query = SELECT DISTINCT 1
            FROM mailboxes
            WHERE active = 1
            AND (
              (domain = '%d' AND user = '%u' AND regex = 0)
              OR (
                regex = 1
                AND '%d' REGEXP CONCAT('^',domain,'$')
                AND '%u' REGEXP CONCAT('^',user,'$')
              )
            )
            LIMIT 1
        '';
      }
      {
        dest = "postfix/ldap_ejabberd_users_immae_fr";
        user = config.services.postfix.user;
        group = config.services.postfix.group;
        permissions = "0440";
        text = ''
          server_host = ldaps://${config.myEnv.jabber.ldap.host}:636
          search_base = ${config.myEnv.jabber.ldap.base}
          query_filter = ${config.myEnv.jabber.postfix_user_filter}
          domain = immae.fr
          bind_dn = ${config.myEnv.jabber.ldap.dn}
          bind_pw = ${config.myEnv.jabber.ldap.password}
          result_attribute = immaeXmppUid
          result_format = ejabberd@localhost
          version = 3
          '';
      }
    ];

    networking.firewall.allowedTCPPorts = [ 25 ];

    nixpkgs.overlays = [ (self: super: {
      postfix = super.postfix.override { withMySQL = true; };
    }) ];
    users.users."${config.services.postfix.user}".extraGroups = [ "keys" ];
    services.filesWatcher.postfix = {
      restart = true;
      paths = [
        config.secrets.fullPaths."postfix/mysql_alias_maps"
        config.secrets.fullPaths."postfix/mysql_mailbox_maps"
        config.secrets.fullPaths."postfix/ldap_ejabberd_users_immae_fr"
      ];
    };
    services.postfix = {
      mapFiles = let
        recipient_maps = let
          name = n: i: "relay_${n}_${toString i}";
          pair = n: i: m: lib.attrsets.nameValuePair (name n i) (
            if m.type == "hash"
            then pkgs.writeText (name n i) m.content
            else null
          );
          pairs = n: v: lib.imap1 (i: m: pair n i m) v.recipient_maps;
        in lib.attrsets.filterAttrs (k: v: v != null) (
          lib.attrsets.listToAttrs (lib.flatten (
            lib.attrsets.mapAttrsToList pairs config.myEnv.mail.postfix.backup_domains
          ))
        );
        relay_restrictions = lib.attrsets.filterAttrs (k: v: v != null) (
          lib.attrsets.mapAttrs' (n: v:
            lib.attrsets.nameValuePair "recipient_access_${n}" (
              if lib.attrsets.hasAttr "relay_restrictions" v
              then pkgs.writeText "recipient_access_${n}" v.relay_restrictions
              else null
            )
          ) config.myEnv.mail.postfix.backup_domains
        );
        virtual_map = {
          virtual = pkgs.writeText "postfix-virtual" (
            builtins.concatStringsSep "\n" (
              lib.attrsets.mapAttrsToList (
                n: v: lib.optionalString v.external ''
                  script_${n}@mail.immae.eu 1
                ''
              ) config.myEnv.mail.scripts
            )
          );
        };
        sasl_access = {
          host_dummy_mailboxes = pkgs.writeText "host-virtual-mailbox"
            (builtins.concatStringsSep "\n" (lib.attrsets.mapAttrsToList (n: v: "${n}@immae.eu  1") nodes));
        };
      in
        recipient_maps // relay_restrictions // virtual_map // sasl_access;
      config = {
        ### postfix module overrides
        readme_directory = "${pkgs.postfix}/share/postfix/doc";
        smtp_tls_CAfile = lib.mkForce "";
        smtp_tls_cert_file = lib.mkForce "";
        smtp_tls_key_file = lib.mkForce "";

        message_size_limit = "1073741824"; # Don't put 0 here, it's not equivalent to "unlimited"
        mailbox_size_limit = "1073741825"; # Workaround, local delivered mails should all go through scripts
        alias_database = "\$alias_maps";

        ### Relay domains
        relay_domains = let
          backups = lib.flatten (lib.attrsets.mapAttrsToList (n: v: v.domains or []) config.myEnv.mail.postfix.backup_domains);
          virtual_domains = config.myEnv.mail.postfix.additional_mailbox_domains
            ++ lib.remove "localhost.immae.eu" (lib.remove null (lib.flatten (map
                (zone: map
                  (e: if e.receive
                  then "${e.domain}${lib.optionalString (e.domain != "") "."}${zone.name}"
                  else null
                  )
                  (zone.withEmail or [])
                )
                config.myEnv.dns.masterZones
              )));
        in
          backups ++ virtual_domains;
        relay_recipient_maps = let
          backup_recipients = lib.flatten (lib.attrsets.mapAttrsToList (n: v:
            lib.imap1 (i: m: "${m.type}:/etc/postfix/relay_${n}_${toString i}") v.recipient_maps
          ) config.myEnv.mail.postfix.backup_domains);
          virtual_alias_maps = [
            "hash:/etc/postfix/virtual"
            "mysql:${config.secrets.fullPaths."postfix/mysql_alias_maps"}"
            "ldap:${config.secrets.fullPaths."postfix/ldap_ejabberd_users_immae_fr"}"
          ];
          virtual_mailbox_maps = [
            "hash:/etc/postfix/host_dummy_mailboxes"
            "mysql:${config.secrets.fullPaths."postfix/mysql_mailbox_maps"}"
          ];
        in
          backup_recipients ++ virtual_alias_maps ++ virtual_mailbox_maps;
        smtpd_relay_restrictions = [
          "defer_unauth_destination"
        ] ++ lib.flatten (lib.attrsets.mapAttrsToList (n: v:
          if lib.attrsets.hasAttr "relay_restrictions" v
          then [ "check_recipient_access hash:/etc/postfix/recipient_access_${n}" ]
          else []
        ) config.myEnv.mail.postfix.backup_domains);

        ### Additional smtpd configuration
        smtpd_tls_received_header = "yes";
        smtpd_tls_loglevel = "1";

        ### Email sending configuration
        smtp_tls_security_level = "may";
        smtp_tls_loglevel = "1";

        ### Force ip bind for smtp
        smtp_bind_address  = config.myEnv.servers."${name}".ips.main.ip4;
        smtp_bind_address6 = builtins.head config.myEnv.servers."${name}".ips.main.ip6;

        smtpd_milters = [
          "unix:${config.myServices.mail.milters.sockets.opendkim}"
          "unix:${config.myServices.mail.milters.sockets.openarc}"
          "unix:${config.myServices.mail.milters.sockets.opendmarc}"
        ];
      };
      enable = true;
      enableSmtp = true;
      enableSubmission = false;
      # FIXME: Mail adressed to localhost.immae.eu will still have mx-1 as
      # prioritized MX, which provokes "mail for localhost.immae.eu loops
      # back to myself" errors. This transport entry forces to push
      # e-mails to its right destination.
      transport = ''
        localhost.immae.eu   smtp:[immae.eu]:25
        '';
      destination = ["localhost"];
      # This needs to reverse DNS
      hostname = config.hostEnv.fqdn;
      setSendmail = false;
      sslCert = "/var/lib/acme/mail/fullchain.pem";
      sslKey = "/var/lib/acme/mail/key.pem";
      recipientDelimiter = "+";
    };
  };
}