#!/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()