feat(ops/modules/open_eid): add support for Web eID extension

Most likely due to bad UX in browsers for hardware-backed TLS client
cert auth, most websites have switched from client-side TLS to the "Web
eID" extension.

Once installed, the extension uses [Native Messaging] to talk to a
`web-eid-app` application, which handles the communication with the
smart card itself.

This can be tested on https://web-eid.eu/ .

The commit needs nixpkgs to be bumped past
https://github.com/NixOS/nixpkgs/pull/227354 .

[Native Messaging]: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_messaging

Change-Id: Iffe6d81ecf7cee25406fa39a983ff52cf669c373
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8490
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

ops/modules/open_eid.nix

@@ -1,25 +1,6 @@
 # NixOS module to configure the Estonian e-ID software.
 { pkgs, ... }:
 
-let
-  # Wrapper script to tell to Chrome/Chromium to use p11-kit-proxy to load
-  # security devices.
-  # Each user needs to run this themselves, it does not work on a system level
-  # due to a bug in Chromium:
-  #
-  # https://bugs.chromium.org/p/chromium/issues/detail?id=16387
-  #
-  # Firefox users can just set
-  # extraPolicies.SecurityDevices.p11-kit-proxy "${pkgs.p11-kit}/lib/p11-kit-proxy.so";
-  # when overriding the firefox derivation.
-  setup-browser-eid = pkgs.writeShellScriptBin "setup-browser-eid" ''
-    NSSDB="''${HOME}/.pki/nssdb"
-    mkdir -p ''${NSSDB}
-
-    ${pkgs.nssTools}/bin/modutil -force -dbdir sql:$NSSDB -add p11-kit-proxy \
-      -libfile ${pkgs.p11-kit}/lib/p11-kit-proxy.so
-  '';
-in
 {
   services.pcscd.enable = true;
 
@@ -29,9 +10,45 @@ in
     module: ${pkgs.opensc}/lib/opensc-pkcs11.so
   '';
 
+  # Configure Firefox (in case users set `programs.firefox.enable = true;`)
+  programs.firefox = {
+    # Allow a possibly installed "Web eID" extension to do native messaging with
+    # the "web-eid-app" native component.
+    # Users not using `programs.firefox.enable` can override their firefox
+    # derivation, by setting `extraNativeMessagingHosts = [ pkgs.web-eid-app ]`.
+    nativeMessagingHosts.euwebid = true;
+    # Configure Firefox to load smartcards via p11kit-proxy.
+    # Users not using `programs.firefox.enable` can override their firefox
+    # derivation, by setting
+    # `extraPolicies.SecurityDevices.p11-kit-proxy "${pkgs.p11-kit}/lib/p11-kit-proxy.so"`.
+    policies.SecurityDevices.p11-kit-proxy = "${pkgs.p11-kit}/lib/p11-kit-proxy.so";
+  };
+
+  # Chromium users need a symlink to their (slightly different) .json file
+  # in the native messaging hosts' manifest file location.
+  environment.etc."chromium/native-messaging-hosts/eu.webeid.json".source = "${pkgs.web-eid-app}/share/web-eid/eu.webeid.json";
+  environment.etc."opt/chrome/native-messaging-hosts/eu.webeid.json".source = "${pkgs.web-eid-app}/share/web-eid/eu.webeid.json";
+
   environment.systemPackages = with pkgs; [
     libdigidocpp.bin # provides digidoc-tool(1)
     qdigidoc
-    setup-browser-eid
+
+    # Wrapper script to tell to Chrome/Chromium to use p11-kit-proxy to load
+    # security devices, so they can be used for TLS client auth.
+    # Each user needs to run this themselves, it does not work on a system level
+    # due to a bug in Chromium:
+    #
+    # https://bugs.chromium.org/p/chromium/issues/detail?id=16387
+    #
+    # Firefox users can just set
+    # extraPolicies.SecurityDevices.p11-kit-proxy "${pkgs.p11-kit}/lib/p11-kit-proxy.so";
+    # when overriding the firefox derivation.
+    (pkgs.writeShellScriptBin "setup-browser-eid" ''
+      NSSDB="''${HOME}/.pki/nssdb"
+      mkdir -p ''${NSSDB}
+
+      ${pkgs.nssTools}/bin/modutil -force -dbdir sql:$NSSDB -add p11-kit-proxy \
+        -libfile ${pkgs.p11-kit}/lib/p11-kit-proxy.so
+    '')
   ];
 }