server-config/containers/server-n0/mail.nix

{
  name,
  pkgs,
  lib,
  hostInfo,
  dsl,
  ...
}:
let
  inherit (dsl) mkContainer mkService;
  inherit (hostInfo.paths) data secrets;

  domain = "mail.floweytf.com";
  accountName = "flowey";
  stateDir = "/var/lib/stalwart";
  acmeDir = "/etc/mail-acme";

  taggingScript = ''
    require ["envelope", "variables", "imap4flags", "fileinto"];

    if envelope :localpart :matches "to" "*" {
      addflag "''${1}";
    }

    fileinto "INBOX";
  '';

  cli = lib.getExe' pkgs.stalwart-cli "stalwart-cli";
  jq = lib.getExe pkgs.jq;
  curl = lib.getExe pkgs.curl;
  grep = lib.getExe' pkgs.gnugrep "grep";
  paste = lib.getExe' pkgs.coreutils "paste";

  # use sqlite b/c rocksdb segfaults
  configJsonTemplate = pkgs.writeText "stalwart-config.json" (
    builtins.toJSON {
      "@type" = "Sqlite";
      path = "${stateDir}/data.sqlite3";
    }
  );

  staticPlan = pkgs.writeText "mail-static-plan.json" (
    builtins.concatStringsSep "\n" (
      map builtins.toJSON [
        {
          "@type" = "upsert";
          object = "Domain";
          matchOn = [ "name" ];
          value."domain-mail" = {
            name = domain;
            catchAllAddress = "${accountName}@${domain}";
            isEnabled = true;
          };
        }
        {
          "@type" = "upsert";
          object = "SieveSystemScript";
          matchOn = [ "name" ];
          value."sieve-tag" = {
            name = "tag-by-recipient";
            isActive = true;
            contents = taggingScript;
          };
        }
      ]
    )
    + "\n"
  );

  stalwartAuthEnv = ''
    export STALWART_URL="http://127.0.0.1:8080"
    export STALWART_USER="admin"
    export STALWART_PASSWORD="$(cat "$CREDENTIALS_DIRECTORY/admin_password")"
  '';

  readyGate = pkgs.writeShellScript "mail-ready-gate" ''
    set -uo pipefail
    until ${curl} -sS -o /dev/null "http://127.0.0.1:8080/api/account"; do
      if ! systemctl -q is-active stalwart.service; then
        echo "mail: stalwart is not running" >&2
        exit 1
      fi
      sleep 1
    done
  '';

  bootstrapScript = pkgs.writeShellScript "mail-bootstrap" ''
    set -uo pipefail
    ${stalwartAuthEnv}

    out="$(${cli} update Bootstrap singleton \
      --field defaultDomain=${domain} \
      --field serverHostname=${domain} \
      --field generateDkimKeys=true \
      --field requestTlsCertificate=false \
      --field 'directory={"@type":"Internal"}' 2>&1)"
    status=$?

    if [ "$status" -eq 0 ]; then
      echo "mail-bootstrap: first-time setup complete, restarting stalwart into normal mode" >&2
      systemctl restart stalwart.service
      exit 0
    fi

    if ${grep} -qi 'bootstrap mode' <<<"$out"; then
      exit 0
    fi

    echo "mail-bootstrap: $out" >&2
    exit 1
  '';

  certCredCert = "/run/credentials/stalwart.service/mail_tls_cert";
  certCredKey = "/run/credentials/stalwart.service/mail_tls_key";

  retryOnFailure = {
    Restart = "on-failure";
    RestartSec = 5;
  };

  retryLimit = {
    StartLimitBurst = 5;
    StartLimitIntervalSec = 120;
  };

  provisionScript = pkgs.writeShellScript "mail-provision" ''
    set -euo pipefail
    ${stalwartAuthEnv}
    export account_pass="$(cat "$CREDENTIALS_DIRECTORY/account_password")"

    account_entry="$(${jq} -nc --arg name "${accountName}" \
      '{"@type":"upsert","object":"Account","matchOn":["name"],"value":{("account-"+$name):{"@type":"User","name":$name,"domainId":"#domain-mail","credentials":{"0":{"@type":"Password","secret":env.account_pass}}}}}')"

    { cat ${staticPlan}; echo "$account_entry"; } | ${cli} apply --stdin

    existing_cert_ids="$(${cli} query Certificate --json --fields id | ${jq} -r .id | ${paste} -sd, -)"
    if [ -n "$existing_cert_ids" ]; then
      ${cli} delete Certificate --ids "$existing_cert_ids"
    fi
    ${cli} create Certificate \
      --field 'certificate={"@type":"File","filePath":"${certCredCert}"}' \
      --field 'privateKey={"@type":"File","filePath":"${certCredKey}"}'

    systemctl restart stalwart.service
  '';
in
mkContainer {
  inherit name;
  includedInTests = false; # TODO: fixme, clearly mail is flakey

  net.access = [ { to = "@internet"; } ];
  svc.autoStart = true;
  miscProperties.nginx = {
    domain = "mail.floweytf.com";
  };
  net.forward.tcp = [
    25
    993
  ];
  resources.fs = {
    "${stateDir}" = {
      hostPath = "${data}/core/mail";
      isReadOnly = false;
    };
    "${acmeDir}" = {
      hostPath = "${data}/core/nginx/acme/${domain}";
      isReadOnly = true;
    };
    "/run/secrets/mail-admin-password" = {
      hostPath = "${secrets}/mail-admin-password";
      isReadOnly = true;
    };
    "/run/secrets/mail-account-password" = {
      hostPath = "${secrets}/mail-account-password";
      isReadOnly = true;
    };
  };
  users = [
    {
      name = "stalwart";
      uid = 1000;
      home = stateDir;
    }
  ];
  containerConfig = _: {
    systemd.tmpfiles.rules = [
      "Z ${stateDir} 0750 stalwart stalwart -"
      "C ${stateDir}/config.json 0640 stalwart stalwart - ${configJsonTemplate}"
    ];

    systemd.services.stalwart = mkService {
      description = "Stalwart Mail Server";
      execStart = pkgs.writeShellScript "stalwart-run" ''
        set -euo pipefail
        export STALWART_RECOVERY_ADMIN="admin:$(cat "$CREDENTIALS_DIRECTORY/admin_password")"
        exec ${lib.getExe' pkgs.stalwart_0_16 "stalwart"} -c ${stateDir}/config.json
      '';
      serviceConfig = {
        User = "stalwart";
        Group = "stalwart";
        AmbientCapabilities = [ "CAP_NET_BIND_SERVICE" ];
        ReadWritePaths = [ stateDir ];
        LoadCredential = [
          "admin_password:/run/secrets/mail-admin-password"
          "mail_tls_cert:${acmeDir}/fullchain.pem"
          "mail_tls_key:${acmeDir}/key.pem"
        ];
        Restart = "on-failure";
        RestartSec = 5;
      };
    };

    systemd.paths.mail-cert-renew = {
      wantedBy = [ "multi-user.target" ];
      pathConfig = {
        PathChanged = "${acmeDir}/key.pem";
        Unit = "mail-provision.service";
      };
    };

    systemd.services.mail-ready = mkService {
      description = "Wait for the Stalwart management API";
      execStart = readyGate;
      after = [ "stalwart.service" ];
      wants = [ "stalwart.service" ];
      wantedBy = [ ];
      serviceConfig = {
        Type = "oneshot";
        RemainAfterExit = true;
        TimeoutStartSec = 60;
      };
    };

    systemd.services.mail-bootstrap = mkService {
      description = "One-time Stalwart bootstrap (server identity + admin account)";
      execStart = bootstrapScript;
      after = [ "mail-ready.service" ];
      wants = [ "mail-ready.service" ];
      unitConfig = retryLimit;
      serviceConfig = {
        Type = "oneshot";
        LoadCredential = [ "admin_password:/run/secrets/mail-admin-password" ];
      }
      // retryOnFailure;
    };

    systemd.services.mail-provision = mkService {
      description = "Provision mail.floweytf.com domain + catch-all account in Stalwart";
      execStart = provisionScript;
      after = [
        "mail-ready.service"
        "mail-bootstrap.service"
      ];
      wants = [
        "mail-ready.service"
        "mail-bootstrap.service"
      ];
      serviceConfig = {
        Type = "oneshot";
        LoadCredential = [
          "admin_password:/run/secrets/mail-admin-password"
          "account_password:/run/secrets/mail-account-password"
        ];
      }
      // retryOnFailure;
      unitConfig = retryLimit;
    };
  };
}