Alexandru Gagniuc | 9b6fc0c | 2021-02-19 12:45:15 -0600 | [diff] [blame] | 1 | # SPDX-License-Identifier: GPL-2.0+ |
| 2 | # |
| 3 | # Copyright (c) 2020,2021 Alexandru Gagniuc <mr.nuke.me@gmail.com> |
| 4 | |
| 5 | """ |
| 6 | Test ECDSA signing of FIT images |
| 7 | |
| 8 | This test uses mkimage to sign an existing FIT image with an ECDSA key. The |
| 9 | signature is then extracted, and verified against pyCryptodome. |
| 10 | This test doesn't run the sandbox. It only checks the host tool 'mkimage' |
| 11 | """ |
| 12 | |
| 13 | import pytest |
| 14 | import u_boot_utils as util |
| 15 | from Cryptodome.Hash import SHA256 |
| 16 | from Cryptodome.PublicKey import ECC |
| 17 | from Cryptodome.Signature import DSS |
| 18 | |
| 19 | class SignableFitImage(object): |
| 20 | """ Helper to manipulate a FIT image on disk """ |
| 21 | def __init__(self, cons, file_name): |
| 22 | self.fit = file_name |
| 23 | self.cons = cons |
| 24 | self.signable_nodes = set() |
| 25 | |
| 26 | def __fdt_list(self, path): |
| 27 | return util.run_and_log(self.cons, f'fdtget -l {self.fit} {path}') |
| 28 | |
| 29 | def __fdt_set(self, node, **prop_value): |
| 30 | for prop, value in prop_value.items(): |
| 31 | util.run_and_log(self.cons, f'fdtput -ts {self.fit} {node} {prop} {value}') |
| 32 | |
| 33 | def __fdt_get_binary(self, node, prop): |
| 34 | numbers = util.run_and_log(self.cons, f'fdtget -tbi {self.fit} {node} {prop}') |
| 35 | |
| 36 | bignum = bytearray() |
| 37 | for little_num in numbers.split(): |
| 38 | bignum.append(int(little_num)) |
| 39 | |
| 40 | return bignum |
| 41 | |
| 42 | def find_signable_image_nodes(self): |
| 43 | for node in self.__fdt_list('/images').split(): |
| 44 | image = f'/images/{node}' |
| 45 | if 'signature' in self.__fdt_list(image): |
| 46 | self.signable_nodes.add(image) |
| 47 | |
| 48 | return self.signable_nodes |
| 49 | |
| 50 | def change_signature_algo_to_ecdsa(self): |
| 51 | for image in self.signable_nodes: |
| 52 | self.__fdt_set(f'{image}/signature', algo='sha256,ecdsa256') |
| 53 | |
| 54 | def sign(self, mkimage, key_file): |
Alexandru Gagniuc | bc8aa28 | 2021-02-19 12:45:20 -0600 | [diff] [blame] | 55 | util.run_and_log(self.cons, [mkimage, '-F', self.fit, f'-G{key_file}']) |
Alexandru Gagniuc | 9b6fc0c | 2021-02-19 12:45:15 -0600 | [diff] [blame] | 56 | |
| 57 | def check_signatures(self, key): |
| 58 | for image in self.signable_nodes: |
| 59 | raw_sig = self.__fdt_get_binary(f'{image}/signature', 'value') |
| 60 | raw_bin = self.__fdt_get_binary(image, 'data') |
| 61 | |
| 62 | sha = SHA256.new(raw_bin) |
| 63 | verifier = DSS.new(key, 'fips-186-3') |
| 64 | verifier.verify(sha, bytes(raw_sig)) |
| 65 | |
| 66 | |
| 67 | @pytest.mark.buildconfigspec('fit_signature') |
| 68 | @pytest.mark.requiredtool('dtc') |
| 69 | @pytest.mark.requiredtool('fdtget') |
| 70 | @pytest.mark.requiredtool('fdtput') |
| 71 | def test_fit_ecdsa(u_boot_console): |
| 72 | """ Test that signatures generated by mkimage are legible. """ |
| 73 | def generate_ecdsa_key(): |
| 74 | return ECC.generate(curve='prime256v1') |
| 75 | |
| 76 | def assemble_fit_image(dest_fit, its, destdir): |
| 77 | dtc_args = f'-I dts -O dtb -i {destdir}' |
| 78 | util.run_and_log(cons, [mkimage, '-D', dtc_args, '-f', its, dest_fit]) |
| 79 | |
| 80 | def dtc(dts): |
| 81 | dtb = dts.replace('.dts', '.dtb') |
| 82 | util.run_and_log(cons, f'dtc {datadir}/{dts} -O dtb -o {tempdir}/{dtb}') |
| 83 | |
| 84 | cons = u_boot_console |
| 85 | mkimage = cons.config.build_dir + '/tools/mkimage' |
| 86 | datadir = cons.config.source_dir + '/test/py/tests/vboot/' |
| 87 | tempdir = cons.config.result_dir |
| 88 | key_file = f'{tempdir}/ecdsa-test-key.pem' |
| 89 | fit_file = f'{tempdir}/test.fit' |
| 90 | dtc('sandbox-kernel.dts') |
| 91 | |
| 92 | key = generate_ecdsa_key() |
| 93 | |
| 94 | # Create a fake kernel image -- zeroes will do just fine |
| 95 | with open(f'{tempdir}/test-kernel.bin', 'w') as fd: |
| 96 | fd.write(500 * chr(0)) |
| 97 | |
| 98 | # invocations of mkimage expect to read the key from disk |
| 99 | with open(key_file, 'w') as f: |
| 100 | f.write(key.export_key(format='PEM')) |
| 101 | |
| 102 | assemble_fit_image(fit_file, f'{datadir}/sign-images-sha256.its', tempdir) |
| 103 | |
| 104 | fit = SignableFitImage(cons, fit_file) |
| 105 | nodes = fit.find_signable_image_nodes() |
| 106 | if len(nodes) == 0: |
| 107 | raise ValueError('FIT image has no "/image" nodes with "signature"') |
| 108 | |
| 109 | fit.change_signature_algo_to_ecdsa() |
| 110 | fit.sign(mkimage, key_file) |
| 111 | fit.check_signatures(key) |