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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 shutil
- import struct
- import pytest
- import u_boot_utils as util
- import vboot_forge
- import vboot_evil
- # Only run the full suite on a few combinations, since it doesn't add any more
- # test coverage.
- TESTDATA = [
- ['sha1', '', None, False, True],
- ['sha1', '', '-E -p 0x10000', False, False],
- ['sha1', '-pss', None, False, False],
- ['sha1', '-pss', '-E -p 0x10000', False, False],
- ['sha256', '', None, False, False],
- ['sha256', '', '-E -p 0x10000', False, False],
- ['sha256', '-pss', None, False, False],
- ['sha256', '-pss', '-E -p 0x10000', False, False],
- ['sha256', '-pss', None, True, False],
- ['sha256', '-pss', '-E -p 0x10000', True, 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,full_test",
- TESTDATA)
- def test_vboot(u_boot_console, sha_algo, padding, sign_options, required,
- full_test):
- """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, fit=None):
- """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
- fit: FIT filename to load and verify
- """
- if not fit:
- fit = '%stest.fit' % tmpdir
- cons.restart_uboot()
- with cons.log.section('Verified boot %s %s' % (sha_algo, test_type)):
- output = cons.run_command_list(
- ['host load hostfs - 100 %s' % fit,
- '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 sign_fit_norequire(sha_algo, options):
- """Sign the FIT
- Signs the FIT and writes the signature into it. It also writes the
- public key into the dtb. It does not mark key as 'required' in 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, 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])
- if full_test:
- # 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.
- ffit = '%stest.forged.fit' % tmpdir
- shutil.copyfile(fit, ffit)
- with open(ffit, 'rb') as fd:
- root, strblock = vboot_forge.read_fdt(fd)
- root, strblock = vboot_forge.manipulate(root, strblock)
- with open(ffit, 'w+b') as fd:
- vboot_forge.write_fdt(root, strblock, fd)
- util.run_and_log_expect_exception(
- cons, [fit_check_sign, '-f', ffit, '-k', dtb],
- 1, 'Failed to verify required signature')
- run_bootm(sha_algo, 'forged config', 'Bad Data Hash', False, ffit)
- # Try adding an evil root node. This should be detected.
- efit = '%stest.evilf.fit' % tmpdir
- shutil.copyfile(fit, efit)
- vboot_evil.add_evil_node(fit, efit, evil_kernel, 'fakeroot')
- util.run_and_log_expect_exception(
- cons, [fit_check_sign, '-f', efit, '-k', dtb],
- 1, 'Failed to verify required signature')
- run_bootm(sha_algo, 'evil fakeroot', 'Bad Data Hash', False, efit)
- # Try adding an @ to the kernel node name. This should be detected.
- efit = '%stest.evilk.fit' % tmpdir
- shutil.copyfile(fit, efit)
- vboot_evil.add_evil_node(fit, efit, evil_kernel, 'kernel@')
- util.run_and_log_expect_exception(
- cons, [fit_check_sign, '-f', efit, '-k', dtb],
- 1, 'Node name contains @')
- run_bootm(sha_algo, 'evil kernel@', 'Bad Data Hash', False, efit)
- # 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_norequire(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_norequire() 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)
- # Build the FIT with dev key (keys required) and sign it. This puts the
- # signature into sandbox-u-boot.dtb, marked 'required'.
- make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
- sign_fit(sha_algo, sign_options)
- # Set the required-mode policy to "any".
- # So now sandbox-u-boot.dtb two signatures, for the prod and dev keys.
- # Both the dev and prod key are 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 be accepted by
- # U-Boot because the dev key is required and policy is "any" required key.
- util.run_and_log(cons, 'fdtput -t s %s /signature required-mode any' %
- (dtb))
- run_bootm(sha_algo, 'multi required key', 'dev+', True)
- # Set the required-mode policy to "all".
- # So now sandbox-u-boot.dtb two signatures, for the prod and dev keys.
- # Both the dev and prod key are 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 and policy is "all" required key
- util.run_and_log(cons, 'fdtput -t s %s /signature required-mode all' %
- (dtb))
- run_bootm(sha_algo, 'multi 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, 'wb') as fd:
- fd.write(500 * b'\0')
- # Create a second kernel image with ones
- evil_kernel = '%stest-kernel1.bin' % tmpdir
- with open(evil_kernel, 'wb') as fd:
- fd.write(500 * b'\x01')
- 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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