use ssh keys instead of password

lib/default.nix

@@ -4,8 +4,10 @@ lib.extend (self: super:
   let
     inherit (lib) attrValues foldr;
     inherit (modules) mapModules;
+    inherit (helpers) getSSH;
 
     modules = import ./modules.nix { inherit lib; };
+    helpers = import ./helpers.nix { inherit lib; };
   in {
     _ = foldr (a: b: a // b) {} (attrValues (mapModules ./. (file: import file {
       inherit pkgs inputs;

lib/helpers.nix

@@ -0,0 +1,18 @@
+{ lib, ... }:
+
+with lib;
+rec {
+  indexFrom = origin: name: item: list: foldr
+  (h: t:
+    if h.${origin} == name && hasAttr item h
+    then h.${item}
+    else t)
+  (error ''
+    No item at the origin point ${origin} with element ${name} found.
+    Please make sure that the item with that origin exists, and,
+    failing that, that it also has the requested item defined.
+  '')
+  list;
+
+  getSSH = name: keys: indexFrom "hostname" name "ssh" keys;
+}