From 22325ce016eeb59be10ce964e106549ac95c1896 Mon Sep 17 00:00:00 2001
From: Will Fancher <elvishjerricco@gmail.com>
Date: Sat, 21 Oct 2023 13:24:16 -0400
Subject: [PATCH] systemd-stage-1: Support for user shells

---
 nixos/modules/config/users-groups.nix    | 17 ++++++++++++++---
 nixos/modules/system/boot/initrd-ssh.nix | 11 ++++++-----
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/nixos/modules/config/users-groups.nix b/nixos/modules/config/users-groups.nix
index 97268a8d83efa86..b4251214876ef77 100644
--- a/nixos/modules/config/users-groups.nix
+++ b/nixos/modules/config/users-groups.nix
@@ -606,6 +606,14 @@ in {
           defaultText = literalExpression "config.users.users.\${name}.group";
           default = cfg.users.${name}.group;
         };
+        options.shell = mkOption {
+          type = types.passwdEntry types.path;
+          description = ''
+            The path to the user's shell in initrd.
+          '';
+          default = "${pkgs.shadow}/bin/nologin";
+          defaultText = literalExpression "\${pkgs.shadow}/bin/nologin";
+        };
       }));
     };
 
@@ -750,17 +758,20 @@ in {
     boot.initrd.systemd = lib.mkIf config.boot.initrd.systemd.enable {
       contents = {
         "/etc/passwd".text = ''
-          ${lib.concatStringsSep "\n" (lib.mapAttrsToList (n: { uid, group }: let
+          ${lib.concatStringsSep "\n" (lib.mapAttrsToList (n: { uid, group, shell }: let
             g = config.boot.initrd.systemd.groups.${group};
-          in "${n}:x:${toString uid}:${toString g.gid}::/var/empty:") config.boot.initrd.systemd.users)}
+          in "${n}:x:${toString uid}:${toString g.gid}::/var/empty:${shell}") config.boot.initrd.systemd.users)}
         '';
         "/etc/group".text = ''
           ${lib.concatStringsSep "\n" (lib.mapAttrsToList (n: { gid }: "${n}:x:${toString gid}:") config.boot.initrd.systemd.groups)}
         '';
+        "/etc/shells".text = lib.concatStringsSep "\n" (lib.unique (lib.mapAttrsToList (_: u: u.shell) config.boot.initrd.systemd.users)) + "\n";
       };
 
+      storePaths = [ "${pkgs.shadow}/bin/nologin" ];
+
       users = {
-        root = {};
+        root = { shell = lib.mkDefault "/bin/bash"; };
         nobody = {};
       };
 
diff --git a/nixos/modules/system/boot/initrd-ssh.nix b/nixos/modules/system/boot/initrd-ssh.nix
index 60c5ff62ffff0a1..3df14030ab68731 100644
--- a/nixos/modules/system/boot/initrd-ssh.nix
+++ b/nixos/modules/system/boot/initrd-ssh.nix
@@ -164,13 +164,12 @@ in
           for instructions.
         '';
       }
-
-      {
-        assertion = config.boot.initrd.systemd.enable -> cfg.shell == null;
-        message = "systemd stage 1 does not support boot.initrd.network.ssh.shell";
-      }
     ];
 
+    warnings = lib.optional (config.boot.initrd.systemd.enable -> cfg.shell != null) ''
+      Please set 'boot.initrd.systemd.users.root.shell' instead of 'boot.initrd.network.ssh.shell'
+    '';
+
     boot.initrd.extraUtilsCommands = mkIf (!config.boot.initrd.systemd.enable) ''
       copy_bin_and_libs ${package}/bin/sshd
       cp -pv ${pkgs.glibc.out}/lib/libnss_files.so.* $out/lib
@@ -235,6 +234,8 @@ in
       users.sshd = { uid = 1; group = "sshd"; };
       groups.sshd = { gid = 1; };
 
+      users.root.shell = mkIf (config.boot.initrd.network.ssh.shell != null) config.boot.initrd.network.ssh.shell;
+
       contents."/etc/ssh/authorized_keys.d/root".text =
         concatStringsSep "\n" config.boot.initrd.network.ssh.authorizedKeys;
       contents."/etc/ssh/sshd_config".text = sshdConfig;