From: Jan Kiszka jan.kiszka@siemens.com
Allows to create a public key device tree dtsi for inclusion into U-Boot SPL and proper during first build already. This can be achieved via CONFIG_DEVICE_TREE_INCLUDES.
Signed-off-by: Jan Kiszka jan.kiszka@siemens.com --- tools/key2dtsi.py | 64 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100755 tools/key2dtsi.py
diff --git a/tools/key2dtsi.py b/tools/key2dtsi.py new file mode 100755 index 00000000000..1dbb2cc94bf --- /dev/null +++ b/tools/key2dtsi.py @@ -0,0 +1,64 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0-only +# +# Public key to dtsi converter. +# +# Copyright (c) Siemens AG, 2022 +# + +from argparse import ArgumentParser, FileType +from os.path import basename, splitext +from Cryptodome.PublicKey import RSA +from Cryptodome.Util.number import inverse + +def int_to_bytestr(n, length=None): + if not length: + length = (n.bit_length() + 7) // 8 + byte_array = n.to_bytes(length, 'big') + return ' '.join(['{:02x}'.format(byte) for byte in byte_array]) + +ap = ArgumentParser(description='Public key to dtsi converter') + +ap.add_argument('--hash', '-H', default='sha256', + help='hash to be used with key (default: sha256)') +ap.add_argument('--required-conf', '-c', action='store_true', + help='mark key required for configuration') +ap.add_argument('--required-image', '-i', action='store_true', + help='mark key required for image') +ap.add_argument('--spl', '-s', action='store_true', + help='mark key for usage in SPL') +ap.add_argument('key_file', metavar='KEY_FILE', type=FileType('r'), + help='key file (formats: X.509, PKCS#1, OpenSSH)') +ap.add_argument('dtsi_file', metavar='DTSI_FILE', type=FileType('w'), + help='dtsi output file') + +args = ap.parse_args() + +key_name, _ = splitext(basename(args.key_file.name)) + +key_data = args.key_file.read() +key = RSA.importKey(key_data) + +r_squared = (2**key.size_in_bits())**2 % key.n +n0_inverse = 2**32 - inverse(key.n, 2**32) + +out = args.dtsi_file +out.write('/ {\n') +out.write('\tsignature {\n') +out.write('\t\tkey-{} {{\n'.format(key_name)) +out.write('\t\t\tkey-name-hint = "{}";\n'.format(key_name)) +out.write('\t\t\talgo = "{},rsa{}";\n'.format(args.hash, key.size_in_bits())) +out.write('\t\t\trsa,num-bits = <{}>;\n'.format(key.size_in_bits())) +out.write('\t\t\trsa,modulus = [{}];\n'.format(int_to_bytestr(key.n))) +out.write('\t\t\trsa,exponent = [{}];\n'.format(int_to_bytestr(key.e, 8))) +out.write('\t\t\trsa,r-squared = [{}];\n'.format(int_to_bytestr(r_squared))) +out.write('\t\t\trsa,n0-inverse = <0x{:x}>;\n'.format(n0_inverse)) +if args.required_conf: + out.write('\t\t\trequired = "conf";\n') +elif args.required_image: + out.write('\t\t\trequired = "image";\n') +if args.spl: + out.write('\t\t\tu-boot,dm-spl;\n') +out.write('\t\t};\n') +out.write('\t};\n') +out.write('};\n')