296 lines
11 KiB
Plaintext
296 lines
11 KiB
Plaintext
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#!/bin/python3
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# Copyright (C) 2017 Red Hat
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# Authors:
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# - Patrick Uiterwijk <puiterwijk@redhat.com>
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# - Kashyap Chamarthy <kchamart@redhat.com>
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#
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# Licensed under MIT License, for full text see LICENSE
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#
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# Purpose: Launch a QEMU guest and enroll ithe UEFI keys into an OVMF
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# variables ("VARS") file. Then boot a Linux kernel with QEMU.
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# Finally, perform a check to verify if Secure Boot
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# is enabled.
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from __future__ import print_function
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import argparse
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import os
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import logging
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import tempfile
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import shutil
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import string
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import subprocess
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def strip_special(line):
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return ''.join([c for c in str(line) if c in string.printable])
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def generate_qemu_cmd(args, readonly, *extra_args):
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if args.disable_smm:
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machinetype = 'pc'
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else:
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machinetype = 'q35,smm=on'
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machinetype += ',accel=%s' % ('kvm' if args.enable_kvm else 'tcg')
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if args.oem_string is None:
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oemstrings = []
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else:
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oemstring_values = [
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",value=" + s.replace(",", ",,") for s in args.oem_string ]
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oemstrings = [
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'-smbios',
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"type=11" + ''.join(oemstring_values) ]
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return [
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args.qemu_binary,
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'-machine', machinetype,
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'-display', 'none',
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'-no-user-config',
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'-nodefaults',
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'-m', '768',
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'-smp', '2,sockets=2,cores=1,threads=1',
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'-chardev', 'pty,id=charserial1',
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'-device', 'isa-serial,chardev=charserial1,id=serial1',
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'-global', 'driver=cfi.pflash01,property=secure,value=%s' % (
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'off' if args.disable_smm else 'on'),
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'-drive',
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'file=%s,if=pflash,format=raw,unit=0,readonly=on' % (
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args.ovmf_binary),
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'-drive',
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'file=%s,if=pflash,format=raw,unit=1,readonly=%s' % (
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args.out_temp, 'on' if readonly else 'off'),
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'-serial', 'stdio'] + oemstrings + list(extra_args)
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def download(url, target, suffix, no_download):
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istemp = False
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if target and os.path.exists(target):
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return target, istemp
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if not target:
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temped = tempfile.mkstemp(prefix='qosb.', suffix='.%s' % suffix)
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os.close(temped[0])
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target = temped[1]
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istemp = True
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if no_download:
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raise Exception('%s did not exist, but downloading was disabled' %
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target)
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import requests
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logging.debug('Downloading %s to %s', url, target)
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r = requests.get(url, stream=True)
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with open(target, 'wb') as f:
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for chunk in r.iter_content(chunk_size=1024):
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if chunk:
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f.write(chunk)
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return target, istemp
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def enroll_keys(args):
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shutil.copy(args.ovmf_template_vars, args.out_temp)
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logging.info('Starting enrollment')
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cmd = generate_qemu_cmd(
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args,
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False,
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'-drive',
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'file=%s,format=raw,if=none,media=cdrom,id=drive-cd1,'
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'readonly=on' % args.uefi_shell_iso,
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'-device',
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'ide-cd,drive=drive-cd1,id=cd1,'
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'bootindex=1')
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p = subprocess.Popen(cmd,
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=subprocess.STDOUT)
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logging.info('Performing enrollment')
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# Wait until the UEFI shell starts (first line is printed)
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read = p.stdout.readline()
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if b'char device redirected' in read:
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read = p.stdout.readline()
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# Skip passed QEMU warnings, like the following one we see in Ubuntu:
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# qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]
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while b'qemu-system-x86_64: warning:' in read:
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read = p.stdout.readline()
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if args.print_output:
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print(strip_special(read), end='')
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print()
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# Send the escape char to enter the UEFI shell early
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p.stdin.write(b'\x1b')
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p.stdin.flush()
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# And then run the following three commands from the UEFI shell:
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# change into the first file system device; install the default
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# keys and certificates, and reboot
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p.stdin.write(b'fs0:\r\n')
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p.stdin.write(b'EnrollDefaultKeys.efi\r\n')
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p.stdin.write(b'reset -s\r\n')
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p.stdin.flush()
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while True:
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read = p.stdout.readline()
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if args.print_output:
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print('OUT: %s' % strip_special(read), end='')
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print()
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if b'info: success' in read:
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break
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p.wait()
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if args.print_output:
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print(strip_special(p.stdout.read()), end='')
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logging.info('Finished enrollment')
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def test_keys(args):
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logging.info('Grabbing test kernel')
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kernel, kerneltemp = download(args.kernel_url, args.kernel_path,
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'kernel', args.no_download)
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logging.info('Starting verification')
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try:
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cmd = generate_qemu_cmd(
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args,
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True,
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'-append', 'console=tty0 console=ttyS0,115200n8',
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'-kernel', kernel)
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p = subprocess.Popen(cmd,
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=subprocess.STDOUT)
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logging.info('Performing verification')
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while True:
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read = p.stdout.readline()
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if args.print_output:
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print('OUT: %s' % strip_special(read), end='')
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print()
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if b'Secure boot disabled' in read:
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raise Exception('Secure Boot was disabled')
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elif b'Secure boot enabled' in read:
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logging.info('Confirmed: Secure Boot is enabled')
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break
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elif b'Kernel is locked down from EFI secure boot' in read:
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logging.info('Confirmed: Secure Boot is enabled')
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break
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p.kill()
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if args.print_output:
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print(strip_special(p.stdout.read()), end='')
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logging.info('Finished verification')
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finally:
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if kerneltemp:
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os.remove(kernel)
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def parse_args():
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parser = argparse.ArgumentParser()
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parser.add_argument('output', help='Filename for output vars file')
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parser.add_argument('--out-temp', help=argparse.SUPPRESS)
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parser.add_argument('--force', help='Overwrite existing output file',
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action='store_true')
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parser.add_argument('--print-output', help='Print the QEMU guest output',
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action='store_true')
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parser.add_argument('--verbose', '-v', help='Increase verbosity',
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action='count')
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parser.add_argument('--quiet', '-q', help='Decrease verbosity',
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action='count')
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parser.add_argument('--qemu-binary', help='QEMU binary path',
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default='/usr/bin/qemu-system-x86_64')
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parser.add_argument('--enable-kvm', help='Enable KVM acceleration',
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action='store_true')
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parser.add_argument('--ovmf-binary', help='OVMF secureboot code file',
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default='/usr/share/edk2/ovmf/OVMF_CODE.secboot.fd')
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parser.add_argument('--ovmf-template-vars', help='OVMF empty vars file',
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default='/usr/share/edk2/ovmf/OVMF_VARS.fd')
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parser.add_argument('--uefi-shell-iso', help='Path to uefi shell iso',
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default='/usr/share/edk2/ovmf/UefiShell.iso')
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parser.add_argument('--skip-enrollment',
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help='Skip enrollment, only test', action='store_true')
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parser.add_argument('--skip-testing',
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help='Skip testing generated "VARS" file',
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action='store_true')
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parser.add_argument('--kernel-path',
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help='Specify a consistent path for kernel')
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parser.add_argument('--no-download', action='store_true',
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help='Never download a kernel')
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parser.add_argument('--fedora-version',
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help='Fedora version to get kernel for checking',
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default='27')
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parser.add_argument('--kernel-url', help='Kernel URL',
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default='https://download.fedoraproject.org/pub/fedora'
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'/linux/releases/%(version)s/Everything/x86_64'
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'/os/images/pxeboot/vmlinuz')
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parser.add_argument('--disable-smm',
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help=('Don\'t restrict varstore pflash writes to '
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'guest code that executes in SMM. Use this '
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'option only if your OVMF binary doesn\'t have '
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'the edk2 SMM driver stack built into it '
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'(possibly because your QEMU binary lacks SMM '
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'emulation). Note that without restricting '
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'varstore pflash writes to guest code that '
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'executes in SMM, a malicious guest kernel, '
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'used for testing, could undermine Secure '
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'Boot.'),
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action='store_true')
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parser.add_argument('--oem-string',
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help=('Pass the argument to the guest as a string in '
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'the SMBIOS Type 11 (OEM Strings) table. '
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'Multiple occurrences of this option are '
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'collected into a single SMBIOS Type 11 table. '
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'A pure ASCII string argument is strongly '
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'suggested.'),
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action='append')
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args = parser.parse_args()
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args.kernel_url = args.kernel_url % {'version': args.fedora_version}
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validate_args(args)
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return args
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def validate_args(args):
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if (os.path.exists(args.output)
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and not args.force
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and not args.skip_enrollment):
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raise Exception('%s already exists' % args.output)
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if args.skip_enrollment and not os.path.exists(args.output):
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raise Exception('%s does not yet exist' % args.output)
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verbosity = (args.verbose or 1) - (args.quiet or 0)
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if verbosity >= 2:
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logging.basicConfig(level=logging.DEBUG)
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elif verbosity == 1:
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logging.basicConfig(level=logging.INFO)
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elif verbosity < 0:
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logging.basicConfig(level=logging.ERROR)
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else:
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logging.basicConfig(level=logging.WARN)
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if args.skip_enrollment:
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args.out_temp = args.output
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else:
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temped = tempfile.mkstemp(prefix='qosb.', suffix='.vars')
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os.close(temped[0])
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args.out_temp = temped[1]
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logging.debug('Temp output: %s', args.out_temp)
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def move_to_dest(args):
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shutil.copy(args.out_temp, args.output)
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os.remove(args.out_temp)
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def main():
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args = parse_args()
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if not args.skip_enrollment:
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enroll_keys(args)
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if not args.skip_testing:
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test_keys(args)
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if not args.skip_enrollment:
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move_to_dest(args)
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if args.skip_testing:
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logging.info('Created %s' % args.output)
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else:
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logging.info('Created and verified %s' % args.output)
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else:
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logging.info('Verified %s', args.output)
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if __name__ == '__main__':
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main()
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