nixos/services/networking/g3proxy: init

This adds a simple hardened systemd-based module for g3proxy, a generic
purpose forward proxy.

Change-Id: I8c6e5d2cc8a9faa2aea8c5df3af56756ffed542d
Signed-off-by: Raito Bezarius <masterancpp@gmail.com>
Co-authored-by: Elias Coppens <elias.coppens@ens.fr>

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -133,6 +133,8 @@
 
 - [PowerStation](https://github.com/ShadowBlip/PowerStation/), an open source TDP control and performance daemon with DBus interface for Linux. Available as [services.powerstation](#opt-services.powerstation.enable).
 
+- [`g3proxy`](https://github.com/bytedance/g3), an open source enterprise forward proxy from ByteDance, similar to Squid or tinyproxy. Available as [services.g3proxy](#opt-services.g3proxy.enable).
+
 - [echoip](https://github.com/mpolden/echoip), a simple service for looking up your IP address. Available as [services.echoip](#opt-services.echoip.enable).
 
 - [Buffyboard](https://gitlab.postmarketos.org/postmarketOS/buffybox/-/tree/master/buffyboard), a framebuffer on-screen keyboard. Available as [services.buffyboard](option.html#opt-services.buffyboard).

nixos/modules/module-list.nix

@@ -1266,6 +1266,7 @@
   ./services/networking/spacecookie.nix
   ./services/networking/spiped.nix
   ./services/networking/squid.nix
+  ./services/networking/g3proxy.nix
   ./services/networking/ssh/sshd.nix
   ./services/networking/sslh.nix
   ./services/networking/strongswan-swanctl/module.nix

nixos/modules/services/networking/g3proxy.nix

@@ -0,0 +1,92 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.services.g3proxy;
+
+  inherit (lib)
+    mkPackageOption
+    mkEnableOption
+    mkOption
+    mkIf
+    literalExpression
+    ;
+
+  settingsFormat = pkgs.formats.yaml { };
+in
+{
+  options.services.g3proxy = {
+    enable = mkEnableOption "g3proxy, a generic purpose forward proxy";
+
+    package = mkPackageOption pkgs "g3proxy" { };
+
+    settings = mkOption {
+      type = settingsFormat.type;
+      default = { };
+      example = literalExpression ''
+        {
+          server = [{
+            name = "test";
+            escaper = "default";
+            type = "socks_proxy";
+            listen = {
+              address = "[::]:10086";
+            };
+          }];
+        }
+      '';
+      description = ''
+        Settings of g3proxy.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.g3proxy = {
+      description = "g3proxy server";
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        ExecStart =
+          let
+            g3proxy-yaml = settingsFormat.generate "g3proxy.yaml" cfg.settings;
+          in
+          "${lib.getExe cfg.package} --config-file ${g3proxy-yaml}";
+
+        WorkingDirectory = "/var/lib/g3proxy";
+        StateDirectory = "g3proxy";
+        RuntimeDirectory = "g3proxy";
+        DynamicUser = true;
+
+        RuntimeDirectoryMode = "0755";
+        PrivateTmp = true;
+        DevicePolicy = "closed";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        PrivateUsers = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectControlGroups = true;
+        ProtectSystem = "strict";
+        ProcSubset = "pid";
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RemoveIPC = true;
+        SystemCallArchitectures = "native";
+        UMask = "0077";
+        RestrictAddressFamilies = [
+          "AF_UNIX"
+          "AF_INET"
+          "AF_INET6"
+        ];
+        RestrictSUIDSGID = true;
+      };
+    };
+  };
+}