Add nixOS module

flake.nix

@@ -70,5 +70,7 @@
             export PATH=${pkgs.rustup}/bin:$PATH
           '';
         };
-      });
+      }) // {
+        nixosModules.default = import ./nix/module.nix self;
+      };
 }

nix/module.nix

@@ -0,0 +1,155 @@
+self:
+{ config, pkgs, inputs, lib, ... }:
+with lib;
+let
+  cfg = config.services.ohttp-relay;
+  socketPath = "/run/ohttp-relay/unix.sock";
+  ohttpHTTPSPath = "/run/nginx/ohttp-https.sock";
+  defaultUserGroup = "ohttprelay";
+in
+{
+  options = {
+    services.ohttp-relay = {
+      package = mkOption {
+        type = types.package;
+        default = self.packages.${pkgs.system}.default;
+      };
+      relayHostname = mkOption { type = types.str; };
+      gatewayOrigin = mkOption { type = types.str; };
+      user = mkOption {
+        type = types.str;
+        default = defaultUserGroup;
+        description = mdDoc "User account under which to run. Not created if not default.";
+      };
+
+      group = mkOption {
+        type = types.str;
+        default = cfg.user;
+        description = mdDoc "Group under which to run. Not created if not default.";
+      };
+    };
+  };
+
+  config = {
+    networking.firewall.allowedTCPPorts = [ 80 443 ];
+
+    security.acme = {
+      certs."${cfg.relayHostname}" = {
+        group = "${config.services.nginx.group}";
+        # NOTE: random port so that nix assertion doesn't complain:
+        # https://github.com/NixOS/nixpkgs/blob/2819fffa7fa42156680f0d282c60d81e8fb185b7/nixos/modules/security/acme/default.nix#L950
+        listenHTTP = "127.0.0.1:1360";
+        extraLegoFlags = [
+          "--tls"
+          "--tls.port" "127.0.0.1:30443"
+        ];
+      };
+    };
+
+    services.nginx = {
+      enable = true;
+      virtualHosts = {};
+      streamConfig = ''
+        map $ssl_preread_alpn_protocols $is_acme {
+          ~\bacme-tls/1\b 1;
+          default 0;
+        }
+
+        map $is_acme $backend {
+          1 acme;
+          default ohttp-https;
+        }
+
+        upstream ohttp-https {
+          server unix:${ohttpHTTPSPath};
+        }
+
+        upstream ohttp-relay {
+          server unix:${socketPath};
+        }
+
+        upstream acme {
+          server 127.0.0.1:30443;
+        }
+
+        server {
+          listen 443;
+
+          ssl_preread on;
+
+          proxy_pass $backend;
+        }
+
+        server {
+          listen 80;
+
+          proxy_pass ohttp-relay;
+        }
+
+        server {
+          listen unix:${ohttpHTTPSPath} ssl;
+
+          ssl_certificate ${config.security.acme.certs."${cfg.relayHostname}".directory}/fullchain.pem;
+          ssl_certificate_key ${config.security.acme.certs."${cfg.relayHostname}".directory}/key.pem;
+
+          # START: Modern configuration
+          # Ref: https://ssl-config.mozilla.org/#server=nginx&version=1.17.7&config=modern&openssl=1.1.1k&guideline=5.7
+          ssl_session_timeout 1d;
+          ssl_session_cache shared:MozSSL:10m;  # about 40000 sessions
+          ssl_session_tickets off;
+
+          ssl_protocols TLSv1.3;
+          ssl_prefer_server_ciphers off;
+          # END: Modern configuration
+
+          proxy_pass ohttp-relay;
+        }
+      '';
+    };
+
+    systemd.services.ohttp-relay = {
+      enable = true;
+      description = "OHTTP Relay";
+      wantedBy = [ "multi-user.target" ];
+
+      after = [ "network-online.target" ];
+
+      environment = {
+        GATEWAY_ORIGIN = cfg.gatewayOrigin;
+        UNIX_SOCKET = socketPath;
+      };
+
+      serviceConfig = {
+        # Give group permissions so people in the group can hit the unix socket
+        UMask = "0002";
+
+        Type = "simple";
+
+        User = cfg.user;
+        Group = cfg.group;
+
+        RuntimeDirectory = "ohttp-relay";
+
+        ExecStart = "${cfg.package}/bin/ohttp-relay";
+        PrivateTmp = true;
+      };
+    };
+
+    users = {
+      groups = optionalAttrs (cfg.group == "${defaultUserGroup}") {
+        "${defaultUserGroup}" = {};
+      };
+      users = {
+        "${config.services.nginx.user}" = {
+          extraGroups = [ config.users.groups.ohttprelay.name ];
+        };
+      } // (optionalAttrs (cfg.user == "${defaultUserGroup}") {
+        "${defaultUserGroup}" = {
+          description = "OHTTP Relay user";
+          isSystemUser = true;
+          group = cfg.group;
+        };
+      });
+    };
+  };
+}