# 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 os 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-basic', 'sha1', '', None, False, True], ['sha1-pad', 'sha1', '', '-E -p 0x10000', False, False], ['sha1-pss', 'sha1', '-pss', None, False, False], ['sha1-pss-pad', 'sha1', '-pss', '-E -p 0x10000', False, False], ['sha256-basic', 'sha256', '', None, False, False], ['sha256-pad', 'sha256', '', '-E -p 0x10000', False, False], ['sha256-pss', 'sha256', '-pss', None, False, False], ['sha256-pss-pad', 'sha256', '-pss', '-E -p 0x10000', False, False], ['sha256-pss-required', 'sha256', '-pss', None, True, False], ['sha256-pss-pad-required', '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("name,sha_algo,padding,sign_options,required,full_test", TESTDATA) def test_vboot(u_boot_console, name, 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 FIT kernel image format', 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@') msg = 'Signature checking prevents use of unit addresses (@) in nodes' util.run_and_log_expect_exception( cons, [fit_check_sign, '-f', efit, '-k', dtb], 1, msg) run_bootm(sha_algo, 'evil kernel@', msg, 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 = os.path.join(cons.config.result_dir, name) + '/' if not os.path.exists(tmpdir): os.mkdir(tmpdir) 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()