nixos/pam: Add option to set pam-u2f appid (#73591)

nixos/modules/security/pam.nix

@@ -366,7 +366,7 @@ let
           ${let p11 = config.security.pam.p11; in optionalString cfg.p11Auth
               "auth ${p11.control} ${pkgs.pam_p11}/lib/security/pam_p11.so ${pkgs.opensc}/lib/opensc-pkcs11.so"}
           ${let u2f = config.security.pam.u2f; in optionalString cfg.u2fAuth
-              "auth ${u2f.control} ${pkgs.pam_u2f}/lib/security/pam_u2f.so ${optionalString u2f.debug "debug"} ${optionalString (u2f.authFile != null) "authfile=${u2f.authFile}"} ${optionalString u2f.interactive "interactive"} ${optionalString u2f.cue "cue"}"}
+              "auth ${u2f.control} ${pkgs.pam_u2f}/lib/security/pam_u2f.so ${optionalString u2f.debug "debug"} ${optionalString (u2f.authFile != null) "authfile=${u2f.authFile}"} ${optionalString u2f.interactive "interactive"} ${optionalString u2f.cue "cue"} ${optionalString (u2f.appId != null) "appid=${u2f.appId}"}"}
           ${optionalString cfg.usbAuth
               "auth sufficient ${pkgs.pam_usb}/lib/security/pam_usb.so"}
           ${let oath = config.security.pam.oath; in optionalString cfg.oathAuth
@@ -653,6 +653,22 @@ in
           xlink:href="https://developers.yubico.com/pam-u2f/">here</link>.
         '';
       };
+      
+      appId = mkOption {
+        default = null;
+        type = with types; nullOr str;
+        description = ''
+            By default <literal>pam-u2f</literal> module sets the application
+            ID to <literal>pam://$HOSTNAME</literal>.
+
+            When using <command>pamu2fcfg</command>, you can specify your
+            application ID with the <literal>-i</literal> flag.
+
+            More information can be found <link
+            xlink:href="https://developers.yubico.com/pam-u2f/Manuals/pam_u2f.8.html">
+            here</link>
+        '';
+      };
 
       control = mkOption {
         default = "sufficient";