nixos: nix.sshServe: Support ssh-ng.

nixos/modules/services/misc/nix-ssh-serve.nix

···
 { config, lib, pkgs, ... }:
 
 with lib;
-
-{
+let cfg = config.nix.sshServe;
+    command =
+      if cfg.protocol == "ssh"
+        then "nix-store --serve"
+      else "nix-daemon --stdio";
+in {
   options = {
 
     nix.sshServe = {
···
       enable = mkOption {
         type = types.bool;
         default = false;
-        description = "Whether to enable serving the Nix store as a binary cache via SSH.";
+        description = "Whether to enable serving the Nix store as a remote store via SSH.";
       };
 
       keys = mkOption {
···
         description = "A list of SSH public keys allowed to access the binary cache via SSH.";
       };
 
+      protocol = mkOption {
+        type = types.enum [ "ssh" "ssh-ng" ];
+        default = "ssh";
+        description = "The specific Nix-over-SSH protocol to use.";
+      };
+
     };
 
   };
 
-  config = mkIf config.nix.sshServe.enable {
+  config = mkIf cfg.enable {
 
     users.extraUsers.nix-ssh = {
-      description = "Nix SSH substituter user";
+      description = "Nix SSH store user";
       uid = config.ids.uids.nix-ssh;
       useDefaultShell = true;
     };
···
         PermitTTY no
         PermitTunnel no
         X11Forwarding no
-        ForceCommand ${config.nix.package.out}/bin/nix-store --serve
+        ForceCommand ${config.nix.package.out}/bin/${command}
       Match All
     '';
 
-    users.extraUsers.nix-ssh.openssh.authorizedKeys.keys = config.nix.sshServe.keys;
+    users.extraUsers.nix-ssh.openssh.authorizedKeys.keys = cfg.keys;
 
   };
 }

nixos/release.nix

···
   tests.nfs4 = callTest tests/nfs.nix { version = 4; };
   tests.nginx = callTest tests/nginx.nix { };
   tests.nghttpx = callTest tests/nghttpx.nix { };
+  tests.nix-ssh-serve = callTest tests/nix-ssh-serve.nix { };
   tests.novacomd = callTestOnTheseSystems ["x86_64-linux"] tests/novacomd.nix { };
   tests.leaps = callTest tests/leaps.nix { };
   tests.nsd = callTest tests/nsd.nix {};

nixos/tests/nix-ssh-serve.nix

···
+import ./make-test.nix ({ pkgs, lib, ... }:
+let inherit (import ./ssh-keys.nix pkgs)
+      snakeOilPrivateKey snakeOilPublicKey;
+    ssh-config = builtins.toFile "ssh.conf" ''
+      UserKnownHostsFile=/dev/null
+      StrictHostKeyChecking=no
+    '';
+in
+   { name = "nix-ssh-serve";
+     meta.maintainers = [ lib.maintainers.shlevy ];
+     nodes =
+       { server.nix.sshServe =
+           { enable = true;
+             keys = [ snakeOilPublicKey ];
+             protocol = "ssh-ng";
+           };
+         server.nix.package = pkgs.nixUnstable;
+         client.nix.package = pkgs.nixUnstable;
+       };
+     testScript = ''
+       startAll;
+
+       $client->succeed("mkdir -m 700 /root/.ssh");
+       $client->copyFileFromHost("${ssh-config}", "/root/.ssh/config");
+       $client->succeed("cat ${snakeOilPrivateKey} > /root/.ssh/id_ecdsa");
+       $client->succeed("chmod 600 /root/.ssh/id_ecdsa");
+
+       $client->succeed("nix-store --add /etc/machine-id > mach-id-path");
+
+       $server->waitForUnit("sshd");
+
+       $client->fail("diff /root/other-store\$(cat mach-id-path) /etc/machine-id");
+       # Currently due to shared store this is a noop :(
+       $client->succeed("nix copy --to ssh-ng://nix-ssh\@server \$(cat mach-id-path)");
+       $client->succeed("nix-store --realise \$(cat mach-id-path) --store /root/other-store --substituters ssh-ng://nix-ssh\@server");
+       $client->succeed("diff /root/other-store\$(cat mach-id-path) /etc/machine-id");
+     '';
+   }
+)

nixos/tests/openssh.nix

···
 import ./make-test.nix ({ pkgs, ... }:
 
-let
-  snakeOilPrivateKey = pkgs.writeText "privkey.snakeoil" ''
-    -----BEGIN EC PRIVATE KEY-----
-    MHcCAQEEIHQf/khLvYrQ8IOika5yqtWvI0oquHlpRLTZiJy5dRJmoAoGCCqGSM49
-    AwEHoUQDQgAEKF0DYGbBwbj06tA3fd/+yP44cvmwmHBWXZCKbS+RQlAKvLXMWkpN
-    r1lwMyJZoSGgBHoUahoYjTh9/sJL7XLJtA==
-    -----END EC PRIVATE KEY-----
-  '';
-
-  snakeOilPublicKey = pkgs.lib.concatStrings [
-    "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHA"
-    "yNTYAAABBBChdA2BmwcG49OrQN33f/sj+OHL5sJhwVl2Qim0vkUJQCry1zFpKTa"
-    "9ZcDMiWaEhoAR6FGoaGI04ff7CS+1yybQ= sakeoil"
-  ];
-
+let inherit (import ./ssh-keys.nix pkgs)
+      snakeOilPrivateKey snakeOilPublicKey;
 in {
   name = "openssh";
   meta = with pkgs.stdenv.lib.maintainers; {

nixos/tests/ssh-keys.nix

···
+pkgs:
+{ snakeOilPrivateKey = pkgs.writeText "privkey.snakeoil" ''
+    -----BEGIN EC PRIVATE KEY-----
+    MHcCAQEEIHQf/khLvYrQ8IOika5yqtWvI0oquHlpRLTZiJy5dRJmoAoGCCqGSM49
+    AwEHoUQDQgAEKF0DYGbBwbj06tA3fd/+yP44cvmwmHBWXZCKbS+RQlAKvLXMWkpN
+    r1lwMyJZoSGgBHoUahoYjTh9/sJL7XLJtA==
+    -----END EC PRIVATE KEY-----
+  '';
+
+  snakeOilPublicKey = pkgs.lib.concatStrings [
+    "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHA"
+    "yNTYAAABBBChdA2BmwcG49OrQN33f/sj+OHL5sJhwVl2Qim0vkUJQCry1zFpKTa"
+    "9ZcDMiWaEhoAR6FGoaGI04ff7CS+1yybQ= sakeoil"
+  ];
+}