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75c89069f0
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>
65 lines
2.3 KiB
Python
Executable File
65 lines
2.3 KiB
Python
Executable File
#!/usr/bin/env python3
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# SPDX-License-Identifier: GPL-2.0-only
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#
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# Public key to dtsi converter.
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#
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# Copyright (c) Siemens AG, 2022
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#
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from argparse import ArgumentParser, FileType
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from os.path import basename, splitext
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from Cryptodome.PublicKey import RSA
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from Cryptodome.Util.number import inverse
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def int_to_bytestr(n, length=None):
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if not length:
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length = (n.bit_length() + 7) // 8
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byte_array = n.to_bytes(length, 'big')
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return ' '.join(['{:02x}'.format(byte) for byte in byte_array])
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ap = ArgumentParser(description='Public key to dtsi converter')
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ap.add_argument('--hash', '-H', default='sha256',
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help='hash to be used with key (default: sha256)')
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ap.add_argument('--required-conf', '-c', action='store_true',
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help='mark key required for configuration')
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ap.add_argument('--required-image', '-i', action='store_true',
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help='mark key required for image')
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ap.add_argument('--spl', '-s', action='store_true',
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help='mark key for usage in SPL')
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ap.add_argument('key_file', metavar='KEY_FILE', type=FileType('r'),
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help='key file (formats: X.509, PKCS#1, OpenSSH)')
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ap.add_argument('dtsi_file', metavar='DTSI_FILE', type=FileType('w'),
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help='dtsi output file')
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args = ap.parse_args()
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key_name, _ = splitext(basename(args.key_file.name))
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key_data = args.key_file.read()
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key = RSA.importKey(key_data)
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r_squared = (2**key.size_in_bits())**2 % key.n
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n0_inverse = 2**32 - inverse(key.n, 2**32)
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out = args.dtsi_file
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out.write('/ {\n')
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out.write('\tsignature {\n')
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out.write('\t\tkey-{} {{\n'.format(key_name))
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out.write('\t\t\tkey-name-hint = "{}";\n'.format(key_name))
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out.write('\t\t\talgo = "{},rsa{}";\n'.format(args.hash, key.size_in_bits()))
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out.write('\t\t\trsa,num-bits = <{}>;\n'.format(key.size_in_bits()))
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out.write('\t\t\trsa,modulus = [{}];\n'.format(int_to_bytestr(key.n)))
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out.write('\t\t\trsa,exponent = [{}];\n'.format(int_to_bytestr(key.e, 8)))
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out.write('\t\t\trsa,r-squared = [{}];\n'.format(int_to_bytestr(r_squared)))
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out.write('\t\t\trsa,n0-inverse = <0x{:x}>;\n'.format(n0_inverse))
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if args.required_conf:
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out.write('\t\t\trequired = "conf";\n')
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elif args.required_image:
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out.write('\t\t\trequired = "image";\n')
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if args.spl:
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out.write('\t\t\tu-boot,dm-spl;\n')
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out.write('\t\t};\n')
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out.write('\t};\n')
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out.write('};\n')
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