builders: provision ssh hostkeys on boot

hosts/wob-vpn-gw/netboot.nix

@@ -1,26 +1,30 @@
-{ lib, pkgs, nodes, config, modulesPath, ... }:
+{ config, lib, pkgs, nodes, modulesPath, ... }:
 
 # The way the connection is established is specific to the wob01 site and the Intel S2600KPR blades.
 # Proper netboot is not possible, because while the blades and the APU board (which is the netboot
 # server here) are in the same L2 network, the uplink connection of each blade is an LACP LAG,
 # meaning that the switch on the other side will only enable the port if it sees valid LACP packets.
-# IPXE sends out these LACP packets while it is probing the ports, however the NICs of the blades
-# do not have a flash which IPXE could be written to.
 # We work around this by presenting a virtual floppy drive using the "IUSB" protocol of the BMC.
-# This virtual floppy drive contains an per-blade customized IPXE script which will initialize the
+# This virtual floppy drive contains an per-blade customized initramfs which will initialize the
-# network connection including IP configuration and chainload the actual script off the netboot
+# network connection including IP configuration and load the actual image off hydra.
-# server.
 
 let
   netboot-server-ip = "2a01:584:11::2";
+  netbootNodes = lib.filterAttrs (_: node: node.config.bagel.baremetal.builders.enable && node.config.bagel.baremetal.builders.netboot) nodes;
 in {
-  networking.firewall.allowedTCPPorts = [ 80 ];
+
+  assertions = [
+    {
+      assertion = !(lib.elem 443 config.networking.firewall.allowedTCPPorts);
+      message = ''
+        Port 443 is in networking.firewalls.allowedTCPPorts, but should be only manually
+        allowed for specific IPs and source ports in ${builtins.toJSON __curPos}
+      '';
+    }
+  ];
 
   systemd.services = lib.mapAttrs' (nodename: node: let
-    ip = "2a01:584:11::1:${toString node.config.bagel.baremetal.builders.num}";
     bmcIp = "192.168.1.${toString (node.config.bagel.baremetal.builders.num * 4 + 2)}";
-    gw = "2a01:584:11::1";
-    dns = "2a01:580:6000::ff01";
     notipxe = node.config.system.build.notipxe.config.system.build.usbImage;
   in lib.nameValuePair "iusb-spoof-${nodename}" {
     wantedBy = [ "multi-user.target" ];
@@ -31,5 +35,29 @@ in {
       AUTH_TOKEN=$(${pkgs.iusb-spoof}/bin/make-token ${bmcIp})
       exec ${pkgs.iusb-spoof}/bin/iusb-spoof -r ${bmcIp} 5123 $AUTH_TOKEN ${notipxe}
     '';
-  }) (lib.filterAttrs (_: node: node.config.bagel.baremetal.builders.enable && node.config.bagel.baremetal.builders.netboot) nodes);
+  }) netbootNodes;
+
+  # Since the builders are stateless, they can not store their ssh hostkeys
+  networking.firewall.allowedTCPPorts = [ 80 ]; # for ACME
+  networking.firewall.extraInputRules = ''
+    ip6 saddr 2a01:584:11::/64 tcp sport < 1024 tcp dport 443 accept;
+  '';
+  security.acme.acceptTerms = true;
+  security.acme.defaults.email = "infra@forkos.org";
+  services.nginx = {
+    enable = true;
+    virtualHosts."vpn-gw.wob01.infra.forkos.org" = {
+      enableACME = true;
+      forceSSL = true;
+      locations = lib.mapAttrs' (nodename: node: let
+        ip = "2a01:584:11::1:${toString node.config.bagel.baremetal.builders.num}";
+      in lib.nameValuePair "/${nodename}/" {
+        root = "/var/www";
+        extraConfig = ''
+          allow ${ip};
+          deny all;
+        '';
+      }) netbootNodes;
+    };
+  };
 }

services/baremetal-builder/netboot.nix

@@ -4,6 +4,25 @@ let
 in
 {
   config = lib.mkIf (cfg.enable && cfg.netboot) {
+
+    system.activationScripts.agenixInstall.deps = ["provisionSshHostKey"];
+    system.activationScripts.provisionSshHostKey = {
+      text = ''
+        echo provisioning ssh hostkey
+        if [ ! -f /etc/ssh/ssh_host_ed25519_key ]
+        then
+          mkdir -p /etc/ssh
+          (
+            umask 0077
+            curl --local-port 25-1024 https://vpn-gw.wob01.infra.forkos.org/${config.networking.hostName}/ssh_host_ed25519_key > /etc/ssh/ssh_host_ed25519_key
+          )
+        fi
+      '';
+      deps = [
+        "specialfs"
+      ];
+    };
+
     system.build = {
 
       # Build a kernel and initramfs which will download the IPXE script from hydra using