1 files changed, 129 insertions, 0 deletions
diff --git a/nixos/modules/programs/shadow.nix b/nixos/modules/programs/shadow.nix
new file mode 100644
index 00000000000..963cd8853db
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+++ b/nixos/modules/programs/shadow.nix
@@ -0,0 +1,129 @@
+# Configuration for the pwdutils suite of tools: passwd, useradd, etc.
+
+{ config, lib, utils, pkgs, ... }:
+
+with lib;
+
+let
+
+  /*
+  There are three different sources for user/group id ranges, each of which gets
+  used by different programs:
+  - The login.defs file, used by the useradd, groupadd and newusers commands
+  - The update-users-groups.pl file, used by NixOS in the activation phase to
+    decide on which ids to use for declaratively defined users without a static
+    id
+  - Systemd compile time options -Dsystem-uid-max= and -Dsystem-gid-max=, used
+    by systemd for features like ConditionUser=@system and systemd-sysusers
+  */
+  loginDefs =
+    ''
+      DEFAULT_HOME yes
+
+      SYS_UID_MIN  400
+      SYS_UID_MAX  999
+      UID_MIN      1000
+      UID_MAX      29999
+
+      SYS_GID_MIN  400
+      SYS_GID_MAX  999
+      GID_MIN      1000
+      GID_MAX      29999
+
+      TTYGROUP     tty
+      TTYPERM      0620
+
+      # Ensure privacy for newly created home directories.
+      UMASK        077
+
+      # Uncomment this and install chfn SUID to allow non-root
+      # users to change their account GECOS information.
+      # This should be made configurable.
+      #CHFN_RESTRICT frwh
+
+    '';
+
+  mkSetuidRoot = source:
+    { setuid = true;
+      owner = "root";
+      group = "root";
+      inherit source;
+    };
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    users.defaultUserShell = lib.mkOption {
+      description = ''
+        This option defines the default shell assigned to user
+        accounts. This can be either a full system path or a shell package.
+
+        This must not be a store path, since the path is
+        used outside the store (in particular in /etc/passwd).
+      '';
+      example = literalExpression "pkgs.zsh";
+      type = types.either types.path types.shellPackage;
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = {
+
+    environment.systemPackages =
+      lib.optional config.users.mutableUsers pkgs.shadow ++
+      lib.optional (types.shellPackage.check config.users.defaultUserShell)
+        config.users.defaultUserShell;
+
+    environment.etc =
+      { # /etc/login.defs: global configuration for pwdutils.  You
+        # cannot login without it!
+        "login.defs".source = pkgs.writeText "login.defs" loginDefs;
+
+        # /etc/default/useradd: configuration for useradd.
+        "default/useradd".source = pkgs.writeText "useradd"
+          ''
+            GROUP=100
+            HOME=/home
+            SHELL=${utils.toShellPath config.users.defaultUserShell}
+          '';
+      };
+
+    security.pam.services =
+      { chsh = { rootOK = true; };
+        chfn = { rootOK = true; };
+        su = { rootOK = true; forwardXAuth = true; logFailures = true; };
+        passwd = {};
+        # Note: useradd, groupadd etc. aren't setuid root, so it
+        # doesn't really matter what the PAM config says as long as it
+        # lets root in.
+        useradd = { rootOK = true; };
+        usermod = { rootOK = true; };
+        userdel = { rootOK = true; };
+        groupadd = { rootOK = true; };
+        groupmod = { rootOK = true; };
+        groupmems = { rootOK = true; };
+        groupdel = { rootOK = true; };
+        login = { startSession = true; allowNullPassword = true; showMotd = true; updateWtmp = true; };
+        chpasswd = { rootOK = true; };
+      };
+
+    security.wrappers = {
+      su        = mkSetuidRoot "${pkgs.shadow.su}/bin/su";
+      sg        = mkSetuidRoot "${pkgs.shadow.out}/bin/sg";
+      newgrp    = mkSetuidRoot "${pkgs.shadow.out}/bin/newgrp";
+      newuidmap = mkSetuidRoot "${pkgs.shadow.out}/bin/newuidmap";
+      newgidmap = mkSetuidRoot "${pkgs.shadow.out}/bin/newgidmap";
+    } // lib.optionalAttrs config.users.mutableUsers {
+      chsh   = mkSetuidRoot "${pkgs.shadow.out}/bin/chsh";
+      passwd = mkSetuidRoot "${pkgs.shadow.out}/bin/passwd";
+    };
+  };
+}