ssh-agent: init module (#4178)

modules/misc/news.nix

@@ -1135,6 +1135,14 @@ in
           A new modules is available: 'programs.zsh.antidote'
         '';
       }
+
+      {
+        time = "2023-06-30T14:46:22+00:00";
+        condition = config.services.ssh-agent.enable;
+        message = ''
+          A new module is available: 'services.ssh-agent'
+        '';
+      }
     ];
   };
 }

modules/modules.nix

@@ -306,6 +306,7 @@ let
     ./services/screen-locker.nix
     ./services/sctd.nix
     ./services/spotifyd.nix
+    ./services/ssh-agent.nix
     ./services/stalonetray.nix
     ./services/status-notifier-watcher.nix
     ./services/swayidle.nix

modules/services/ssh-agent.nix

@@ -0,0 +1,36 @@
+{ config, options, lib, pkgs, ... }:
+
+let
+
+  cfg = config.services.ssh-agent;
+
+in {
+  meta.maintainers = [ lib.maintainers.lheckemann ];
+
+  options = {
+    services.ssh-agent = {
+      enable = lib.mkEnableOption "OpenSSH private key agent";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    home.sessionVariablesExtra = ''
+      if [[ -z "$SSH_AUTH_SOCK" ]]; then
+        export SSH_AUTH_SOCK=$XDG_RUNTIME_DIR/ssh-agent
+      fi
+    '';
+
+    systemd.user.services.ssh-agent = {
+      Install.WantedBy = [ "default.target" ];
+
+      Unit = {
+        Description = "SSH authentication agent";
+        Documentation = "man:ssh-agent(1)";
+      };
+
+      Service = {
+        ExecStart = "${pkgs.openssh}/bin/ssh-agent -D -a %t/ssh-agent";
+      };
+    };
+  };
+}