Add login notify module

Signed-off-by: magic_rb <magic_rb@redalder.org>

nixos/modules/notify-login.nix

@@ -0,0 +1,121 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}: let
+  cfg = config.services.notify-login;
+  inherit
+    (lib)
+    mkEnableOption
+    getExe
+    getExe'
+    mkIf
+    mkMerge
+    mkOption
+    types
+    error
+    optionalString
+    ;
+  source = {
+    name,
+    pamService,
+    sessionName,
+  }: {
+    options = {
+      enable = mkEnableOption "Enable login notifications.";
+      method = mkOption {
+        type = with types; enum ["matrix"];
+        description = ''
+          What notification method to use.
+        '';
+      };
+      settings = let
+        methodSettings = {
+          "matrix" = {
+            secretsFile = mkOption {
+              type = with types; str;
+              description = ''
+                Path to the secrets file.
+              '';
+            };
+            stateDirectory = mkOption {
+              type = with types; str;
+              description = ''
+                Path to the state directory.
+              '';
+            };
+            markdown = mkOption {
+              type = with types; bool;
+              description = ''
+                Whether to parse input as markdown;
+              '';
+            };
+          };
+        };
+      in
+        methodSettings.${cfg.${name}.method} or (error "Invalid method");
+    };
+    config = mkIf cfg.${name}.enable {
+      security.pam.services.${pamService}.rules.session.pam_exec = let
+        methods = {
+          "matrix" = pkgs.writeShellScript "matrix-${name}-notify" ''
+            {
+            if [ "$PAM_TYPE" = "open_session" ] ; then
+            ${getExe' pkgs.coreutils "cat"} <<EOF
+            **Opened** ${sessionName} session for user **$PAM_USER** from host **$PAM_RHOST**
+            EOF
+            elif [ "$PAM_TYPE" = "close_session" ] ; then
+            ${getExe' pkgs.coreutils "cat"} <<EOF
+            **Closed** ${sessionName} session for user **$PAM_USER** from host **$PAM_RHOST**
+            EOF
+            else
+            ${getExe' pkgs.coreutils "cat"} <<EOF
+            \`\`\`
+            Unknown PAM_TYPE: "$PAM_TYPE"
+            PAM_RHOST: "$PAM_RHOST"
+            PAM_RUSER: "$PAM_RUSER"
+            PAM_SERVICE: "$PAM_SERVICE"
+            PAM_TTY: "$PAM_TTY"
+            PAM_USER: "$PAM_USER"
+            EOF
+            \`\`\`
+            fi
+            } | ${getExe pkgs.matrix-commander-rs} \
+              -c ${cfg.${name}.settings.secretsFile} \
+              -s ${cfg.${name}.settings.stateDirectory} \
+              ${optionalString cfg.${name}.settings.markdown "--markdown"} \
+              -m - &
+            disown %1
+          '';
+        };
+        sudoLogin = methods.${cfg.${name}.method} or (error "Invalid method");
+      in {
+        modulePath = "pam_exec.so";
+        args = [(toString sudoLogin)];
+        control = "optional";
+        order = config.security.pam.services.${pamService}.rules.session.limits.order + 10;
+      };
+    };
+  };
+  sshSource = source {
+    name = "ssh";
+    pamService = "sshd";
+    sessionName = "SSH";
+  };
+  sudoSource = source {
+    name = "sudo";
+    pamService = "sudo";
+    sessionName = "sudo";
+  };
+in {
+  options.services.notify-login = {
+    ssh = sshSource.options;
+    sudo = sudoSource.options;
+  };
+
+  config = mkMerge [
+    sshSource.config
+    sudoSource.config
+  ];
+}

nixos/systems/blowhole/default.nix

@@ -48,6 +48,7 @@ in
             ./sol.nix
             ../../common/remote_access.nix
             ./microvms.nix
+            ../../modules/notify-login.nix
             inputs.serokell-nix.nixosModules.acme-sh
 
             inputs.notnft.nixosModules.default
@@ -61,6 +62,16 @@ in
             config'.flake.nixosModules.grafana
           ];
 
+          services.notify-login.ssh = {
+            enable = true;
+            method = "matrix";
+            settings = {
+              secretsFile = "/var/secrets/matrix-notify-login-ssh.json";
+              stateDirectory = "/var/lib/matrix-commander/notify-login-ssh";
+              markdown = true;
+            };
+          };
+
           _module.args.nixinate = {
             host = "blowhole.hosts.in.redalder.org";
             sshUser = "main";