Blame ovmf-vars-generator

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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()