lass: init otp-ssh

lass/1systems/mors/config.nix

@@ -24,6 +24,7 @@ with import <stockholm/lib>;
     <stockholm/lass/2configs/ircd.nix>
     <stockholm/lass/2configs/logf.nix>
     <stockholm/lass/2configs/syncthing.nix>
+    <stockholm/lass/2configs/otp-ssh.nix>
     {
       #risk of rain port
       krebs.iptables.tables.filter.INPUT.rules = [

lass/2configs/otp-ssh.nix

@@ -0,0 +1,18 @@
+{ pkgs, ... }:
+# Enables second factor for ssh password login
+
+## Usage:
+#  gen-oath-safe <username> totp
+## scan the qrcode with google authenticator (or FreeOTP)
+## copy last line into secrets/<host>/users.oath (chmod 700)
+{
+  security.pam.oath = {
+    # enabling it will make it a requisite of `all` services
+    # enable = true;
+    digits = 6;
+    # TODO assert existing
+    usersFile = (toString <secrets>) + "/users.oath";
+  };
+  # I want TFA only active for sshd with password-auth
+  security.pam.services.sshd.oathAuth = true;
+}