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u-boot/test/py/tests/test_vboot.py
Philippe Reynes eb7690e81f test/py: vboot: add a test to check fit signature on fit with padding 
The pytest vboot does all his tests on fit without padding.
We add the same tests on fit with padding.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
2020-05-01 11:34:01 -04:00

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# SPDX-License-Identifier: GPL-2.0+
# Copyright (c) 2016, Google Inc.
#
# U-Boot Verified Boot Test
"""
This tests verified boot in the following ways:
For image verification:
- Create FIT (unsigned) with mkimage
- Check that verification shows that no keys are verified
- Sign image
- Check that verification shows that a key is now verified
For configuration verification:
- Corrupt signature and check for failure
- Create FIT (with unsigned configuration) with mkimage
- Check that image verification works
- Sign the FIT and mark the key as 'required' for verification
- Check that image verification works
- Corrupt the signature
- Check that image verification no-longer works
Tests run with both SHA1 and SHA256 hashing.
"""
import struct
import pytest
import u_boot_utils as util
import vboot_forge
TESTDATA = [
['sha1', '', None, False],
['sha1', '', '-E -p 0x10000', False],
['sha1', '-pss', None, False],
['sha1', '-pss', '-E -p 0x10000', False],
['sha256', '', None, False],
['sha256', '', '-E -p 0x10000', False],
['sha256', '-pss', None, False],
['sha256', '-pss', '-E -p 0x10000', False],
['sha256', '-pss', None, True],
['sha256', '-pss', '-E -p 0x10000', True],
]
@pytest.mark.boardspec('sandbox')
@pytest.mark.buildconfigspec('fit_signature')
@pytest.mark.requiredtool('dtc')
@pytest.mark.requiredtool('fdtget')
@pytest.mark.requiredtool('fdtput')
@pytest.mark.requiredtool('openssl')
@pytest.mark.parametrize("sha_algo,padding,sign_options,required", TESTDATA)
def test_vboot(u_boot_console, sha_algo, padding, sign_options, required):
"""Test verified boot signing with mkimage and verification with 'bootm'.
This works using sandbox only as it needs to update the device tree used
by U-Boot to hold public keys from the signing process.
The SHA1 and SHA256 tests are combined into a single test since the
key-generation process is quite slow and we want to avoid doing it twice.
"""
def dtc(dts):
"""Run the device tree compiler to compile a .dts file
The output file will be the same as the input file but with a .dtb
extension.
Args:
dts: Device tree file to compile.
"""
dtb = dts.replace('.dts', '.dtb')
util.run_and_log(cons, 'dtc %s %s%s -O dtb '
'-o %s%s' % (dtc_args, datadir, dts, tmpdir, dtb))
def run_bootm(sha_algo, test_type, expect_string, boots):
"""Run a 'bootm' command U-Boot.
This always starts a fresh U-Boot instance since the device tree may
contain a new public key.
Args:
test_type: A string identifying the test type.
expect_string: A string which is expected in the output.
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to
use.
boots: A boolean that is True if Linux should boot and False if
we are expected to not boot
"""
cons.restart_uboot()
with cons.log.section('Verified boot %s %s' % (sha_algo, test_type)):
output = cons.run_command_list(
['host load hostfs - 100 %stest.fit' % tmpdir,
'fdt addr 100',
'bootm 100'])
assert expect_string in ''.join(output)
if boots:
assert 'sandbox: continuing, as we cannot run' in ''.join(output)
else:
assert('sandbox: continuing, as we cannot run'
not in ''.join(output))
def make_fit(its):
"""Make a new FIT from the .its source file.
This runs 'mkimage -f' to create a new FIT.
Args:
its: Filename containing .its source.
"""
util.run_and_log(cons, [mkimage, '-D', dtc_args, '-f',
'%s%s' % (datadir, its), fit])
def sign_fit(sha_algo, options):
"""Sign the FIT
Signs the FIT and writes the signature into it. It also writes the
public key into the dtb.
Args:
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to
use.
options: Options to provide to mkimage.
"""
args = [mkimage, '-F', '-k', tmpdir, '-K', dtb, '-r', fit]
if options:
args += options.split(' ')
cons.log.action('%s: Sign images' % sha_algo)
util.run_and_log(cons, args)
def replace_fit_totalsize(size):
"""Replace FIT header's totalsize with something greater.
The totalsize must be less than or equal to FIT_SIGNATURE_MAX_SIZE.
If the size is greater, the signature verification should return false.
Args:
size: The new totalsize of the header
Returns:
prev_size: The previous totalsize read from the header
"""
total_size = 0
with open(fit, 'r+b') as handle:
handle.seek(4)
total_size = handle.read(4)
handle.seek(4)
handle.write(struct.pack(">I", size))
return struct.unpack(">I", total_size)[0]
def create_rsa_pair(name):
"""Generate a new RSA key paid and certificate
Args:
name: Name of of the key (e.g. 'dev')
"""
public_exponent = 65537
util.run_and_log(cons, 'openssl genpkey -algorithm RSA -out %s%s.key '
'-pkeyopt rsa_keygen_bits:2048 '
'-pkeyopt rsa_keygen_pubexp:%d' %
(tmpdir, name, public_exponent))
# Create a certificate containing the public key
util.run_and_log(cons, 'openssl req -batch -new -x509 -key %s%s.key '
'-out %s%s.crt' % (tmpdir, name, tmpdir, name))
def test_with_algo(sha_algo, padding, sign_options):
"""Test verified boot with the given hash algorithm.
This is the main part of the test code. The same procedure is followed
for both hashing algorithms.
Args:
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to
use.
padding: Either '' or '-pss', to select the padding to use for the
rsa signature algorithm.
sign_options: Options to mkimage when signing a fit image.
"""
# Compile our device tree files for kernel and U-Boot. These are
# regenerated here since mkimage will modify them (by adding a
# public key) below.
dtc('sandbox-kernel.dts')
dtc('sandbox-u-boot.dts')
# Build the FIT, but don't sign anything yet
cons.log.action('%s: Test FIT with signed images' % sha_algo)
make_fit('sign-images-%s%s.its' % (sha_algo, padding))
run_bootm(sha_algo, 'unsigned images', 'dev-', True)
# Sign images with our dev keys
sign_fit(sha_algo, sign_options)
run_bootm(sha_algo, 'signed images', 'dev+', True)
# Create a fresh .dtb without the public keys
dtc('sandbox-u-boot.dts')
cons.log.action('%s: Test FIT with signed configuration' % sha_algo)
make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
run_bootm(sha_algo, 'unsigned config', '%s+ OK' % sha_algo, True)
# Sign images with our dev keys
sign_fit(sha_algo, sign_options)
run_bootm(sha_algo, 'signed config', 'dev+', True)
cons.log.action('%s: Check signed config on the host' % sha_algo)
util.run_and_log(cons, [fit_check_sign, '-f', fit, '-k', dtb])
# Make sure that U-Boot checks that the config is in the list of hashed
# nodes. If it isn't, a security bypass is possible.
with open(fit, 'rb') as fd:
root, strblock = vboot_forge.read_fdt(fd)
root, strblock = vboot_forge.manipulate(root, strblock)
with open(fit, 'w+b') as fd:
vboot_forge.write_fdt(root, strblock, fd)
util.run_and_log_expect_exception(
cons, [fit_check_sign, '-f', fit, '-k', dtb],
1, 'Failed to verify required signature')
run_bootm(sha_algo, 'forged config', 'Bad Data Hash', False)
# Create a new properly signed fit and replace header bytes
make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
sign_fit(sha_algo, sign_options)
bcfg = u_boot_console.config.buildconfig
max_size = int(bcfg.get('config_fit_signature_max_size', 0x10000000), 0)
existing_size = replace_fit_totalsize(max_size + 1)
run_bootm(sha_algo, 'Signed config with bad hash', 'Bad Data Hash',
False)
cons.log.action('%s: Check overflowed FIT header totalsize' % sha_algo)
# Replace with existing header bytes
replace_fit_totalsize(existing_size)
run_bootm(sha_algo, 'signed config', 'dev+', True)
cons.log.action('%s: Check default FIT header totalsize' % sha_algo)
# Increment the first byte of the signature, which should cause failure
sig = util.run_and_log(cons, 'fdtget -t bx %s %s value' %
(fit, sig_node))
byte_list = sig.split()
byte = int(byte_list[0], 16)
byte_list[0] = '%x' % (byte + 1)
sig = ' '.join(byte_list)
util.run_and_log(cons, 'fdtput -t bx %s %s value %s' %
(fit, sig_node, sig))
run_bootm(sha_algo, 'Signed config with bad hash', 'Bad Data Hash',
False)
cons.log.action('%s: Check bad config on the host' % sha_algo)
util.run_and_log_expect_exception(
cons, [fit_check_sign, '-f', fit, '-k', dtb],
1, 'Failed to verify required signature')
def test_required_key(sha_algo, padding, sign_options):
"""Test verified boot with the given hash algorithm.
This function tests if U-Boot rejects an image when a required key isn't
used to sign a FIT.
Args:
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to use
padding: Either '' or '-pss', to select the padding to use for the
rsa signature algorithm.
sign_options: Options to mkimage when signing a fit image.
"""
# Compile our device tree files for kernel and U-Boot. These are
# regenerated here since mkimage will modify them (by adding a
# public key) below.
dtc('sandbox-kernel.dts')
dtc('sandbox-u-boot.dts')
cons.log.action('%s: Test FIT with configs images' % sha_algo)
# Build the FIT with prod key (keys required) and sign it. This puts the
# signature into sandbox-u-boot.dtb, marked 'required'
make_fit('sign-configs-%s%s-prod.its' % (sha_algo, padding))
sign_fit(sha_algo, sign_options)
# Build the FIT with dev key (keys NOT required). This adds the
# signature into sandbox-u-boot.dtb, NOT marked 'required'.
make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
sign_fit(sha_algo, sign_options)
# So now sandbox-u-boot.dtb two signatures, for the prod and dev keys.
# Only the prod key is set as 'required'. But FIT we just built has
# a dev signature only (sign_fit() overwrites the FIT).
# Try to boot the FIT with dev key. This FIT should not be accepted by
# U-Boot because the prod key is required.
run_bootm(sha_algo, 'required key', '', False)
cons = u_boot_console
tmpdir = cons.config.result_dir + '/'
datadir = cons.config.source_dir + '/test/py/tests/vboot/'
fit = '%stest.fit' % tmpdir
mkimage = cons.config.build_dir + '/tools/mkimage'
fit_check_sign = cons.config.build_dir + '/tools/fit_check_sign'
dtc_args = '-I dts -O dtb -i %s' % tmpdir
dtb = '%ssandbox-u-boot.dtb' % tmpdir
sig_node = '/configurations/conf-1/signature'
create_rsa_pair('dev')
create_rsa_pair('prod')
# Create a number kernel image with zeroes
with open('%stest-kernel.bin' % tmpdir, 'w') as fd:
fd.write(500 * chr(0))
try:
# We need to use our own device tree file. Remember to restore it
# afterwards.
old_dtb = cons.config.dtb
cons.config.dtb = dtb
if required:
test_required_key(sha_algo, padding, sign_options)
else:
test_with_algo(sha_algo, padding, sign_options)
finally:
# Go back to the original U-Boot with the correct dtb.
cons.config.dtb = old_dtb
cons.restart_uboot()
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