utils: add boot.py

Add utility module related to the process of booting a system from a
client's partition.

The main utility function to boot a clients system is boot_os_at(), from
which firmware (UEFI or BIOS) and os-family specific private functions are invoked.

This initial commit adds UEFI windows boot function.

src/utils/boot.py

@@ -0,0 +1,63 @@
+#
+# Copyright (C) 2023 Soleta Networks <info@soleta.eu>
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the
+# Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+
+import json
+import logging
+import os
+import shlex
+import subprocess
+
+from src.utils.probe import OSFamily, get_os_family
+from src.utils.disk import get_partition_device, get_efi_partition
+from src.utils.uefi import *
+from src.utils.fs import *
+
+
+def _boot_uefi_windows(disk, part, mountpoint):
+    logging.info(f'Booting windows system')
+    bootlabel = f'Part-{disk:02d}-{part:02d}'
+    esp, esp_disk, esp_part_number = get_efi_partition(disk)
+    esp_mountpoint = esp.replace('dev', 'mnt')
+    if not mount_mkdir(esp, esp_mountpoint):
+        raise RuntimeError(f'Unable to mount detected EFI System Partition at {esp} into {esp_mountpoint}')
+
+    loader_paths = [f'{esp_mountpoint}/EFI/{bootlabel}/Boot/bootmgfw.efi',
+                    f'{esp_mountpoint}/EFI/Microsoft/Boot/bootmgfw.efi']
+    try:
+        for efi_app in loader_paths:
+            if os.path.exists(efi_app):
+                loader = efi_app[len(esp_mountpoint):]
+                logging.info(f'Found bootloader at ESP partition: {loader}')
+                break
+        else:
+            raise RuntimeError(f'Unable to locate Windows EFI bootloader bootmgfw.efi')
+
+        efibootmgr_delete_bootentry(bootlabel)
+        efibootmgr_create_bootentry(esp_disk, esp_part_number, loader, bootlabel)
+        efibootmgr_bootnext(bootlabel)
+    finally:
+        umount(esp_mountpoint)
+
+
+def boot_os_at(disk, part):
+    if not is_uefi_supported():
+        raise NotImplementedError('BIOS booting is not implemented yet')
+
+    device = get_partition_device(disk, part)
+    mountpoint = device.replace('dev', 'mnt')
+    if not mount_mkdir(device, mountpoint):
+        raise RuntimeError(f'Cannot probe OS family. Unable to mount {device} at {esp_mountpoint}.')
+
+    logging.info(f'Booting system at {device}. Probing OS family...')
+    os_family = get_os_family(mountpoint)
+    if os_family == OSFamily.WINDOWS:
+        _boot_uefi_windows(disk, part, mountpoint)
+    elif os_family == OSFamily.LINUX:
+        raise NotImplementedError('WIP: Linux UEFI boot not implemented yet.')
+    else:
+        raise RuntimeError('Unknown OS family')