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