Fixes #36833 - Add SecureBoot support for arbitrary operating systems…

… to "Grub2 UEFI" PXE loaders

This feature consists of four patches, one each for foreman,
smart-proxy, foreman-installer, and puppet-foreman_proxy.

This patch adds support for individual Network Bootstrap Programs (NBP)
in order to enable network based installations of SecureBoot enabled
hosts for arbitrary operating systems.

SecureBoot expects to follow a chain of trust from the initial boot of
the host to the loading of Linux kernel modules. The very first shim
that is loaded determines which distribution is allowed to be booted or
kexec'ed until next reboot.

Currently the "Grub2 UEFI SecureBoot" PXE loaders use NBPs provided by
the vendor of the Foreman/Smart Proxy host system. All hosts receive and
execute the same binary. On SecureBoot enabled hosts, this limits
installations to operating systems by the vendor of the Foreman/
Smart Proxy host system.

Providing shim and GRUB2 by the vendor of the operating system to be
installed allows Foreman to install any operating system on SecureBoot
enabled hosts over network.

To achieve this, the host's DHCP filename option is set to a shim/GRUB2
binary in a host specific directory based on their MAC address.
Corresponding shim and GRUB2 binaries are copied into that directory
along with the generated GRUB2 configuration files.
When provisioning a host, the Smart Proxy checks in a dedicated
directory inside the TFTP root - the so called "bootloader universe" -
if NBPs are present matching the operating system, operating system
version, and architecture of the host to be installed. If this is the
case, these NBPs are copied from the bootloader universe directory to
the host specific directory. If not, as a fallback the default NBPs
provided by the vendor of the Foreman/Smart Proxy host system are
copied from the `:tftproot:/grub2` directory to the host specific
directory.

Up to now, shim and GRUB2 binaries have to be retrieved and set up in
the bootloader universe directory manually according to the
documentation. An automatic way to provide OS dependent NBPs will be
added in future.

In case there are no NBPs present in the bootloader universe matching
the operating system, operating system version, and architecture of
the host to be installed, the behaviour of the "Grub2 UEFI" PXE
loaders does not change to the behavior prior to this feature.

Implementation notes:
---------------------
* To be future proof (e.g. to be able to provide NBPs in the bootloader
  universe for other PXE loaders without running into any filename
  conflicts) and for better structure, the PXE kind is prepended as a
  first directory level inside the bootloader universe.
* The operating system version inside the bootloader universe consists
  of the major and minor version (if applicable) of the operating system
  separated by a dot (`.`). If no NBPs are configured for a specific
  operating system version the fallback directory `default` is used.
* To simplify things on Foreman side in future, symlinks are used for
  the shim (boot-sb.efi) and GRUB2 (boot.efi) binaries.
* Inside the TFTP root directory a new directory `host-config` is
  created for storing all the host specific directories.
* Inside the TFTP root directory a new directory `bootloader-universe`
  is created for storing all the OS specific boot files.
* For storage efficiency the shim and GRUB2 binaries from the
  bootloader universe or the `:tftproot:/grub2` directory are
  symlinked to the host specific directory.

Full example:
-------------
[root@vm ~]# hammer host info --id 241 | grep -E "(MAC address|Operating System)"
MAC address: 00:50:56:b4:75:5e
Operating System: AlmaLinux 8.9

[root@vm ~]# tree /var/lib/tftpboot/bootloader-universe/
/var/lib/tftpboot/bootloader-universe/
└── pxegrub2
    └── almalinux
        ├── 8.9
        │   └── x86_64
        │       ├── boot.efi -> grubx64.efi
        │       ├── boot-sb.efi -> shimx64.efi
        │       ├── grubx64.efi
        │       └── shimx64.efi
        └── default
            └── x86_64
                ├── boot.efi -> grubx64.efi
                ├── boot-sb.efi -> shimx64.efi
                ├── grubx64.efi
                └── shimx64.efi

[root@vm ~]# hammer host update --id 241 --build true

[root@vm ~]# tree /var/lib/tftpboot/host-config
/var/lib/tftpboot/host-config
└── 00-50-56-a3-41-a8
    └── grub2
        ├── boot.efi -> ../../../bootloader-universe/grubx64.efi
        ├── boot-sb.efi -> ../../../bootloader-universe/shimx64.efi
        ├── grub.cfg
        ├── grub.cfg-00:50:56:a3:41:a8
        ├── grub.cfg-01-00-50-56-a3-41-a8
        ├── grubx64.efi -> ../../../bootloader-universe/grubx64.efi
        ├── os_info
        └── shimx64.efi -> ../../../bootloader-universe/shimx64.efi

[root@vm ~]# grep -B2 00-50-56-b4-75-5e /var/lib/dhcpd/dhcpd.leases
hardware ethernet 00:50:56:b4:75:5e;
fixed-address 192.168.145.84;
supersede server.filename = "host-config/00-50-56-b4-75-5e/grub2/boot-sb.efi";

[root@vm ~]# pesign -S -i /var/lib/tftpboot/host-config/00-50-56-b4-75-5e/grub2/boot-sb.efi | grep "Microsoft Windows UEFI Driver Publisher"
The signer's common name is Microsoft Windows UEFI Driver Publisher

modules/tftp/server.rb

@@ -63,6 +63,19 @@ def delete_file(file)
         logger.debug "TFTP: Skipping a request to delete a file which doesn't exists"
       end
     end
+
+    def delete_host_dir(mac)
+      host_dir = File.join(path, 'host-config', dashed_mac(mac).downcase)
+      logger.debug "TFTP: Removing directory '#{host_dir}'."
+      FileUtils.rm_rf host_dir
+    end
+
+    def setup_bootloader(mac:, os:, release:, arch:, bootfilename_efi:)
+    end
+
+    def dashed_mac(mac)
+      mac.tr(':', '-')
+    end
   end
 
   class Syslinux < Server
@@ -75,7 +88,7 @@ def pxe_default
     end
 
     def pxeconfig_file(mac)
-      ["#{pxeconfig_dir}/01-" + mac.tr(':', "-").downcase]
+      ["#{pxeconfig_dir}/01-" + dashed_mac(mac).downcase]
     end
   end
   class Pxelinux < Syslinux; end
@@ -90,21 +103,114 @@ def pxe_default
     end
 
     def pxeconfig_file(mac)
-      ["#{pxeconfig_dir}/menu.lst.01" + mac.delete(':').upcase, "#{pxeconfig_dir}/01-" + mac.tr(':', '-').upcase]
+      ["#{pxeconfig_dir}/menu.lst.01" + mac.delete(':').upcase, "#{pxeconfig_dir}/01-" + dashed_mac(mac).upcase]
     end
   end
 
   class Pxegrub2 < Server
-    def pxeconfig_dir
-      "#{path}/grub2"
+    def bootloader_path(os, release, arch)
+      bootloader_path = File.join(Proxy::TFTP::Plugin.settings.tftproot, 'bootloader-universe/pxegrub2', os, release, arch)
+
+      logger.debug "TFTP: Checking if bootloader universe is configured for OS '#{os}' version '#{release}' (#{arch})."
+      logger.debug "TFTP: Checking if directory '#{bootloader_path}' exists."
+      unless Dir.exist?(bootloader_path)
+        logger.debug "TFTP: Directory '#{bootloader_path}' does not exist."
+
+        bootloader_path = File.join(Proxy::TFTP::Plugin.settings.tftproot, 'bootloader-universe/pxegrub2', os, 'default', arch)
+
+        logger.debug "TFTP: Checking if bootloader universe is configured for OS '#{os}' (#{arch})."
+        logger.debug "TFTP: Checking if directory '#{bootloader_path}' exists."
+        unless Dir.exist?(bootloader_path)
+          logger.debug "TFTP: Directory '#{bootloader_path}' does not exist."
+          return
+        end
+      end
+
+      bootloader_path
+    end
+
+    def create_bootloader_universe_symlinks(bootloader_path, pxeconfig_dir_mac)
+      symlinks = []
+      Dir.glob(File.join(bootloader_path, '*.efi')).each do |source_file|
+        symlinks << { source: Pathname.new(source_file), symlink: Pathname.new(File.join(pxeconfig_dir_mac, File.basename(source_file))) }
+      end
+      create_symlinks(symlinks)
+    end
+
+    def create_default_symlinks(bootfilename_efi, pxeconfig_dir_mac)
+      pxeconfig_dir = pxeconfig_dir()
+      symlinks = [
+        { source: Pathname.new(File.join(pxeconfig_dir, "grub#{bootfilename_efi}.efi")), symlink: Pathname.new(File.join(pxeconfig_dir_mac, "boot.efi")) },
+        { source: Pathname.new(File.join(pxeconfig_dir, "grub#{bootfilename_efi}.efi")), symlink: Pathname.new(File.join(pxeconfig_dir_mac, "grub#{bootfilename_efi}.efi")) },
+        { source: Pathname.new(File.join(pxeconfig_dir, "shim#{bootfilename_efi}.efi")), symlink: Pathname.new(File.join(pxeconfig_dir_mac, "boot-sb.efi")) },
+        { source: Pathname.new(File.join(pxeconfig_dir, "shim#{bootfilename_efi}.efi")), symlink: Pathname.new(File.join(pxeconfig_dir_mac, "shim#{bootfilename_efi}.efi")) },
+      ]
+      create_symlinks(symlinks)
+    end
+
+    def create_symlinks(symlinks)
+      symlinks.each do |link|
+        relative_source_path = link[:source].relative_path_from(link[:symlink].parent)
+
+        logger.debug "TFTP: Creating relative symlink: #{link[:symlink]} -> #{relative_source_path}"
+        FileUtils.ln_s(relative_source_path.to_s, link[:symlink].to_s, force: true)
+      end
+    end
+
+    # Configures bootloader files for a host in its host-config directory
+    #
+    # @param mac [String] The MAC address of the host
+    # @param os [String] The lowercase name of the operating system of the host
+    # @param release [String] The major and minor version of the operating system of the host
+    # @param arch [String] The architecture of the operating system of the host
+    # @param bootfilename_efi [String] The architecture specific boot filename suffix
+    def setup_bootloader(mac:, os:, release:, arch:, bootfilename_efi:)
+      pxeconfig_dir_mac = pxeconfig_dir(mac)
+
+      logger.debug "TFTP: Deploying host specific bootloader files to '#{pxeconfig_dir_mac}'."
+
+      FileUtils.mkdir_p(pxeconfig_dir_mac)
+      FileUtils.rm_f(Dir.glob("#{pxeconfig_dir_mac}/*.efi"))
+
+      bootloader_path = bootloader_path(os, release, arch)
+
+      if bootloader_path
+        logger.debug "TFTP: Creating symlinks from bootloader universe."
+        create_bootloader_universe_symlinks(bootloader_path, pxeconfig_dir_mac)
+      else
+        logger.debug "TFTP: Creating symlinks from default bootloader files."
+        create_default_symlinks(bootfilename_efi, pxeconfig_dir_mac)
+      end
+
+      File.write(File.join(pxeconfig_dir_mac, 'os_info'), "#{os} #{release} #{arch}")
+    end
+
+    def del(mac)
+      super mac
+      delete_host_dir mac
+    end
+
+    def pxeconfig_dir(mac = nil)
+      if mac
+        File.join(path, 'host-config', dashed_mac(mac).downcase, 'grub2')
+      else
+        File.join(path, 'grub2')
+      end
     end
 
     def pxe_default
       ["#{pxeconfig_dir}/grub.cfg"]
     end
 
     def pxeconfig_file(mac)
-      ["#{pxeconfig_dir}/grub.cfg-01-" + mac.tr(':', '-').downcase, "#{pxeconfig_dir}/grub.cfg-#{mac.downcase}"]
+      pxeconfig_dir_mac = pxeconfig_dir(mac)
+      [
+        "#{pxeconfig_dir_mac}/grub.cfg",
+        "#{pxeconfig_dir_mac}/grub.cfg-01-#{dashed_mac(mac).downcase}",
+        "#{pxeconfig_dir_mac}/grub.cfg-#{mac.downcase}",
+        "#{pxeconfig_dir}/grub.cfg-01-" + dashed_mac(mac).downcase,
+        "#{pxeconfig_dir}/grub.cfg-#{mac.downcase}",
+      ]
     end
   end
 
@@ -146,7 +252,7 @@ def pxe_default
     end
 
     def pxeconfig_file(mac)
-      ["#{pxeconfig_dir}/01-" + mac.tr(':', "-").downcase + ".ipxe"]
+      ["#{pxeconfig_dir}/01-" + dashed_mac(mac).downcase + ".ipxe"]
     end
   end
 

modules/tftp/tftp_api.rb

@@ -18,8 +18,9 @@ def instantiate(variant, mac = nil)
         Object.const_get("Proxy").const_get('TFTP').const_get(variant.capitalize).new
       end
 
-      def create(variant, mac)
+      def create(variant, mac, os: nil, release: nil, arch: nil, bootfilename_efi: nil)
         tftp = instantiate variant, mac
+        log_halt(400, "TFTP: Failed to setup host specific bootloader directory: ") { tftp.setup_bootloader(mac: mac, os: os, release: release, arch: arch, bootfilename_efi: bootfilename_efi) }
         log_halt(400, "TFTP: Failed to create pxe config file: ") { tftp.set(mac, (params[:pxeconfig] || params[:syslinux_config])) }
       end
 
@@ -48,7 +49,7 @@ def create_default(variant)
     end
 
     post "/:variant/:mac" do |variant, mac|
-      create variant, mac
+      create variant, mac, os: params[:targetos], release: params[:release], arch: params[:arch], bootfilename_efi: params[:bootfilename_efi]
     end
 
     delete "/:variant/:mac" do |variant, mac|

modules/tftp/tftp_plugin.rb

@@ -2,6 +2,8 @@ module Proxy::TFTP
   class Plugin < ::Proxy::Plugin
     plugin :tftp, ::Proxy::VERSION
 
+    capability :bootloader_universe
+
     rackup_path File.expand_path("http_config.ru", __dir__)
 
     default_settings :tftproot => '/var/lib/tftpboot',

test/tftp/integration_test.rb

@@ -14,7 +14,7 @@ def test_features
     mod = response['tftp']
     refute_nil(mod)
     assert_equal('running', mod['state'], Proxy::LogBuffer::Buffer.instance.info[:failed_modules][:tftp])
-    assert_equal([], mod['capabilities'])
+    assert_equal(["bootloader_universe"], mod['capabilities'])
 
     expected_settings = { 'tftp_servername' => 'tftp.example.com' }
     assert_equal(expected_settings, mod['settings'])

test/tftp/tftp_server_test.rb

@@ -113,7 +113,13 @@ class TftpPxegrub2ServerTest < Test::Unit::TestCase
 
   def setup_paths
     @subject = Proxy::TFTP::Pxegrub2.new
-    @pxe_config_files = ["grub2/grub.cfg-01-aa-bb-cc-dd-ee-ff", "grub2/grub.cfg-aa:bb:cc:dd:ee:ff"]
+    @pxe_config_files = [
+      "host-config/aa-bb-cc-dd-ee-ff/grub2/grub.cfg",
+      "host-config/aa-bb-cc-dd-ee-ff/grub2/grub.cfg-01-aa-bb-cc-dd-ee-ff",
+      "host-config/aa-bb-cc-dd-ee-ff/grub2/grub.cfg-aa:bb:cc:dd:ee:ff",
+      "grub2/grub.cfg-01-aa-bb-cc-dd-ee-ff",
+      "grub2/grub.cfg-aa:bb:cc:dd:ee:ff",
+    ]
     @pxe_default_files = ["grub2/grub.cfg"]
   end
 end