ssh: port to modules system

hosts/common/ssh.nix

@@ -1,10 +1,22 @@
 { config, lib, ... }:
 {
+  # persist the host key
   environment.etc."ssh/host_keys".source = "/nix/persist/etc/ssh/host_keys";
 
+  # let openssh find our host keys
   services.openssh.hostKeys = [
     { type = "rsa"; bits = 4096; path = "/etc/ssh/host_keys/ssh_host_rsa_key"; }
     { type = "ed25519"; path = "/etc/ssh/host_keys/ssh_host_ed25519_key"; }
   ];
 
+  sane.ssh.pubkeys = {
+    "colin@lappy" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDpmFdNSVPRol5hkbbCivRhyeENzb9HVyf9KutGLP2Zu";
+    "root@lappy" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILSJnqmVl9/SYQ0btvGb0REwwWY8wkdkGXQZfn/1geEc";
+    "root@desko" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFw9NoRaYrM6LbDd3aFBc4yyBlxGQn8HjeHd/dZ3CfHk";
+    "colin@desko" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPU5GlsSfbaarMvDA20bxpSZGWviEzXGD8gtrIowc1pX";
+    "root@servo" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOfdSmFkrVT6DhpgvFeQKm3Fh9VKZ9DbLYOPOJWYQ0E8";
+    "colin@servo" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPS1qFzKurAdB9blkWomq8gI1g0T3sTs9LsmFOj5VtqX";
+    "root@moby" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIO1N/IT3nQYUD+dBlU1sTEEVMxfOyMkrrDeyHcYgnJvw";
+    "colin@moby" = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICrR+gePnl0nV/vy7I5BzrGeyVL+9eOuXHU1yNE3uCwU";
+  };
 }

hosts/common/users.nix

@@ -52,7 +52,11 @@ in
       passwordFile = lib.mkIf (config.sops.secrets ? "colin-passwd") config.sops.secrets.colin-passwd.path;
 
       shell = pkgs.zsh;
-      openssh.authorizedKeys.keys = builtins.attrValues (import ../../modules/pubkeys.nix).users;
+      openssh.authorizedKeys.keys =
+      let
+        user-keys = filter (k: k.user == "colin") (attrValues config.sane.ssh.pubkeys);
+      in
+        map (k: k.asUserKey) user-keys;
 
       # mount encrypted stuff at login
       # some other nix pam users:

modules/default.nix

@@ -12,6 +12,7 @@
     ./persist
     ./services
     ./sops.nix
+    ./ssh.nix
   ];
 
   _module.args =  {

modules/home-manager/ssh.nix

@@ -1,19 +1,22 @@
 { config, lib, pkgs, sane-lib, ... }:
 
+with lib;
 let
   host = config.networking.hostName;
-  user_pubkey = (import ../pubkeys.nix).users."${host}";
+  user-pubkey = config.sane.ssh.pubkeys."colin@${host}".asUserKey;
-  known_hosts_text = builtins.concatStringsSep
+  host-keys = filter (k: k.user == "root") (attrValues config.sane.ssh.pubkeys);
+  known-hosts-text = concatStringsSep
     "\n"
-    (builtins.attrValues (import ../pubkeys.nix).hosts);
+    (map (k: k.asHostKey) host-keys)
+  ;
 in lib.mkIf config.sane.home-manager.enable {
   # ssh key is stored in private storage
   sane.persist.home.private = [ ".ssh/id_ed25519" ];
-  sane.fs."/home/colin/.ssh/id_ed25519.pub" = sane-lib.fs.wantedText user_pubkey;
+  sane.fs."/home/colin/.ssh/id_ed25519.pub" = sane-lib.fs.wantedText user-pubkey;
 
   home-manager.users.colin = {
     programs.ssh.enable = true;
     # this optionally accepts multiple known_hosts paths, separated by space.
-    programs.ssh.userKnownHostsFile = builtins.toString (pkgs.writeText "known_hosts" known_hosts_text);
+    programs.ssh.userKnownHostsFile = toString (pkgs.writeText "known_hosts" known-hosts-text);
   };
 }

modules/pubkeys.nix

@@ -1,34 +0,0 @@
-# create ssh key by running:
-# - `ssh-keygen -t ed25519`
-let
-  withHost = host: key: "${host} ${key}";
-  withUser = user: key: "${key} ${user}";
-
-  keys = rec {
-    lappy = {
-      host = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILSJnqmVl9/SYQ0btvGb0REwwWY8wkdkGXQZfn/1geEc";
-      users.colin = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDpmFdNSVPRol5hkbbCivRhyeENzb9HVyf9KutGLP2Zu";
-    };
-    desko = {
-      host = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFw9NoRaYrM6LbDd3aFBc4yyBlxGQn8HjeHd/dZ3CfHk";
-      users.colin = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPU5GlsSfbaarMvDA20bxpSZGWviEzXGD8gtrIowc1pX";
-    };
-    servo = {
-      host = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOfdSmFkrVT6DhpgvFeQKm3Fh9VKZ9DbLYOPOJWYQ0E8";
-      users.colin = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPS1qFzKurAdB9blkWomq8gI1g0T3sTs9LsmFOj5VtqX";
-    };
-    moby = {
-      host = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIO1N/IT3nQYUD+dBlU1sTEEVMxfOyMkrrDeyHcYgnJvw";
-      users.colin = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICrR+gePnl0nV/vy7I5BzrGeyVL+9eOuXHU1yNE3uCwU";
-    };
-
-    "uninsane.org" = servo;
-    "git.uninsane.org" = servo;
-  };
-in {
-  # map hostname -> something suitable for known_keys
-  hosts = builtins.mapAttrs (host: keys: withHost host keys.host) keys;
-  # map hostname -> something suitable for authorized_keys to allow access to colin@<hostname>
-  users = builtins.mapAttrs (host: keys: withUser "colin@${host}" keys.users.colin) keys;
-}
-

modules/ssh.nix

@@ -0,0 +1,66 @@
+{ lib, ... }:
+
+with lib;
+let
+  key = types.submodule ({ name, config, ...}: {
+    options = {
+      typedPubkey = mkOption {
+        type = types.str;
+        description = ''
+          the pubkey with type attached.
+          e.g. "ssh-ed25519 <base64>"
+        '';
+      };
+      # type = mkOption {
+      #   type = types.str;
+      #   description = ''
+      #     the type of the key, e.g. "id_ed25519"
+      #   '';
+      # };
+      host = mkOption {
+        type = types.str;
+        description = ''
+          the hostname of a key
+        '';
+      };
+      user = mkOption {
+        type = types.str;
+        description = ''
+          the username of a key
+        '';
+      };
+      asUserKey = mkOption {
+        type = types.str;
+        description = ''
+          append the "user@host" value to the pubkey to make it usable for ~/.ssh/id_<x>.pub or authorized_keys
+        '';
+      };
+      asHostKey = mkOption {
+        type = types.str;
+        description = ''
+          prepend the "host" value to the pubkey to make it usable for ~/.ssh/known_hosts
+        '';
+      };
+    };
+    config = rec {
+      user = head (lib.splitString "@" name);
+      host = last (lib.splitString "@" name);
+      asUserKey = "${config.typedPubkey} ${name}";
+      asHostKey = "${host} ${config.typedPubkey}";
+    };
+  });
+  coercedToKey = types.coercedTo types.str (typedPubkey: {
+    inherit typedPubkey;
+  }) key;
+in
+{
+  options = {
+    sane.ssh.pubkeys = mkOption {
+      type = types.attrsOf coercedToKey;
+      default = [];
+      description = ''
+        mapping from "user@host" to pubkey.
+      '';
+    };
+  };
+}