{
  pkgs,
  inputs',
  lib,
  config,
  ...
}: let
  inherit
    (lib)
    singleton
    mkForce
    ;
  certs = config.services.acme-sh.certs;
in {
  users.users.wwwrun = {
    group = "wwwrun";
    isSystemUser = true;
    uid = config.ids.uids.wwwrun;
  };

  users.groups.wwwrun = {
    gid = config.ids.gids.wwwrun;
  };

  systemd.services.apache-proxy = let
    apacheConfiguration = inputs'.nixng.nglib.generators.toApache [
      {
        LoadModule = [
          ["mpm_event_module" "modules/mod_mpm_event.so"]
          ["log_config_module" "modules/mod_log_config.so"]
          ["unixd_module" "modules/mod_unixd.so"]
          ["authz_core_module" "modules/mod_authz_core.so"]
          ["authn_core_module" "modules/mod_authn_core.so"]
          ["dir_module" "modules/mod_dir.so"]
          ["mime_module" "modules/mod_mime.so"]
          ["proxy_module" "modules/mod_proxy.so"]
          ["proxy_http_module" "modules/mod_proxy_http.so"]
          ["access_compat_module" "modules/mod_access_compat.so"]
          ["proxy_connect_module" "modules/mod_proxy_connect.so"]
          ["authn_file_module" "modules/mod_authn_file.so"]
          ["authz_user_module" "modules/mod_authz_user.so"]
          ["authz_host_module" "modules/mod_authz_host.so"]
          ["auth_basic_module" "modules/mod_auth_basic.so"]
          ["ssl_module" "modules/mod_ssl.so"]
        ];
      }
      {
        Listen = "0.0.0.0:8883";

        ServerRoot = "/var/empty";
        ServerName = "altra";
        PidFile = "/run/apache/apache.pid";

        DocumentRoot = "/var/empty";
      }

      {
        ErrorLog = "/var/log/apache/error.log";
        TransferLog = "/var/log/apache/access.log";
      }
      {
        MaxConnectionsPerChild = 1024;
        MaxMemFree = 8192;

        ThreadsPerChild = 64;
        MaxRequestWorkers = 2048;
        ServerLimit = 32;
        AsyncRequestWorkerFactor = 8;
      }
      {
        AddType = singleton [
          "image/svg+xml"
          "svg"
          "svgz"
        ];
        AddEncoding = [
          "gzip"
          "svgz"
        ];

        TypesConfig = "${pkgs.apacheHttpd}/conf/mime.types";
      }

      {
        Directory."/" = {
          Require = ["all" "denied"];
          Options = "SymlinksIfOwnerMatch";
        };

        VirtualHost."*:8883" = [
          {
            ProxyRequests = "on";
            AddDefaultCharset = "off";
            AllowCONNECT = ["443" "8448" "8433" "8478" "3236" "8080"];
          }
          {
            ServerName = "synapse-proxy.in.redalder.org";
            SSLEngine = "on";
            SSLCertificateFile = certs.apache-proxy.certPath;
            SSLCertificateKeyFile = certs.apache-proxy.keyPath;
            SSLCipherSuite = "HIGH:!aNULL:!MD5";
          }
          {
            Proxy."*" = {
              Require = ["all" "denied"];
            };
          }
          {
            ProxyMatch."^([a-zA-Z\-_0-9]+\.)+[a-zA-Z\-_0-9]*:(443|8448|8443|8478|3236|8080).*$" = {
              AuthType = "Basic";
              AuthName = "\"Password Required\"";
              AuthUserFile = "/var/secrets/htpasswd";

              RequireAll."" = {
                Require = [
                  ["user synapse"]
                  ["method CONNECT"]
                ];
                RequireAny."" = {
                  Require = [
                    ["ip 10.64.0.2"]
                  ];
                };
              };
            };
          }
          {
            ProxyMatch."^http:\/\/([a-zA-Z\-_0-9]+\.)+[a-zA-Z\-_0-9]*(|:(80|8080))$" = {
              AuthType = "Basic";
              AuthName = "\"Password Required\"";
              AuthUserFile = "/var/secrets/htpasswd";

              RequireAll."" = {
                Require = [
                  ["user synapse"]
                  ["not method CONNECT"]
                ];
                RequireAny."" = {
                  Require = [
                    ["ip 10.64.0.2"]
                  ];
                };
              };
            };
          }
        ];
      }
    ];
  in {
    serviceConfig = {
      Type = "forking";
      Restart = "always";
      RestartSec = "10s";
      # User and group
      User = "wwwrun";
      Group = "wwwrun";
      # Runtime directory and mode
      RuntimeDirectory = "apache";
      RuntimeDirectoryMode = "0750";
      # Cache directory and mode
      CacheDirectory = "apache";
      CacheDirectoryMode = "0750";
      # Logs directory and mode
      LogsDirectory = "apache";
      LogsDirectoryMode = "0750";
      # Proc filesystem
      ProcSubset = "pid";
      ProtectProc = "invisible";
      # New file permissions
      UMask = "0027"; # 0640 / 0750
      # Capabilities
      AmbientCapabilities = ["CAP_NET_BIND_SERVICE" "CAP_SYS_RESOURCE"];
      CapabilityBoundingSet = ["CAP_NET_BIND_SERVICE" "CAP_SYS_RESOURCE"];
      # Security
      NoNewPrivileges = true;
      # Sandboxing (sorted by occurrence in https://www.freedesktop.org/software/systemd/man/systemd.exec.html)
      ProtectSystem = "strict";
      ProtectHome = true;
      PrivateTmp = true;
      PrivateDevices = true;
      ProtectHostname = true;
      ProtectClock = true;
      ProtectKernelTunables = true;
      ProtectKernelModules = true;
      ProtectKernelLogs = true;
      ProtectControlGroups = true;
      RestrictAddressFamilies = ["AF_UNIX" "AF_INET" "AF_INET6"];
      RestrictNamespaces = true;
      LockPersonality = true;
      MemoryDenyWriteExecute = true;
      RestrictRealtime = true;
      RestrictSUIDSGID = true;
      RemoveIPC = true;
      PrivateMounts = true;
      # System Call Filtering
      SystemCallArchitectures = "native";
      SystemCallFilter = ["~@cpu-emulation @debug @keyring @mount @obsolete @privileged @setuid ~@ipc"];
    };
    wantedBy = ["multi-user.target"];
    script = ''
      ls /proc/self/fd /dev
      ${pkgs.apacheHttpd}/bin/httpd -f ${pkgs.writeText "apache.conf" apacheConfiguration}
    '';
  };

  services.acme-sh.certs.apache-proxy = {
    production = true;
    user = "wwwrun";
    domains."synapse-proxy.in.redalder.org" = "dns_hetzner";
    mainDomain = "synapse-proxy.in.redalder.org";
    postRun = "systemctl try-reload-or-restart --no-block apache-proxy.service";
  };

  systemd.services."acme-sh-apache-proxy" = {
    serviceConfig.EnvironmentFile = mkForce "/var/secrets/hetzner.env";
  };
}