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#!/usr/bin/env python
# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
# A script to pack EC binary into SPI flash image for MEC1322
# Based on MEC1322_ROM_Doc_Rev0.5.pdf.
import argparse
import hashlib
import os
import struct
import subprocess
import tempfile
LOAD_ADDR = 0x100000
HEADER_SIZE = 0x140
SPI_CLOCK_LIST = [48, 24, 12, 8]
SPI_READ_CMD_LIST = [0x3, 0xb, 0x3b]
CRC_TABLE = [0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15,
0x38, 0x3f, 0x36, 0x31, 0x24, 0x23, 0x2a, 0x2d]
def Crc8(crc, data):
"""Update CRC8 value."""
data_bytes = map(lambda b: ord(b) if isinstance(b, str) else b, data)
for v in data_bytes:
crc = ((crc << 4) & 0xff) ^ (CRC_TABLE[(crc >> 4) ^ (v >> 4)]);
crc = ((crc << 4) & 0xff) ^ (CRC_TABLE[(crc >> 4) ^ (v & 0xf)]);
return crc ^ 0x55
def GetEntryPoint(payload_file):
"""Read entry point from payload EC image."""
with open(payload_file, 'rb') as f:
f.seek(4)
s = f.read(4)
return struct.unpack('<I', s)[0]
def GetPayload(payload_file):
"""Read payload and pad it to 64-byte aligned."""
with open(payload_file, 'rb') as f:
payload = bytearray(f.read())
rem_len = len(payload) % 64
if rem_len:
payload += '\0' * (64 - rem_len)
return payload
def GetPublicKey(pem_file):
"""Extract public exponent and modulus from PEM file."""
s = subprocess.check_output(['openssl', 'rsa', '-in', pem_file,
'-text', '-noout'])
modulus_raw = []
in_modulus = False
for line in s.split('\n'):
if line.startswith('modulus'):
in_modulus = True
elif not line.startswith(' '):
in_modulus = False
elif in_modulus:
modulus_raw.extend(line.strip().strip(':').split(':'))
if line.startswith('publicExponent'):
exp = int(line.split(' ')[1], 10)
modulus_raw.reverse()
modulus = bytearray(''.join(map(lambda x: chr(int(x, 16)),
modulus_raw[0:256])))
return struct.pack('<Q', exp), modulus
def GetSpiClockParameter(args):
assert args.spi_clock in SPI_CLOCK_LIST, \
"Unsupported SPI clock speed %d MHz" % args.spi_clock
return SPI_CLOCK_LIST.index(args.spi_clock)
def GetSpiReadCmdParameter(args):
assert args.spi_read_cmd in SPI_READ_CMD_LIST, \
"Unsupported SPI read command 0x%x" % args.spi_read_cmd
return SPI_READ_CMD_LIST.index(args.spi_read_cmd)
def PadZeroTo(data, size):
data.extend('\0' * (size - len(data)))
def BuildHeader(args, payload_len):
# Identifier and header version
header = bytearray(['C', 'S', 'M', 'S', '\0'])
PadZeroTo(header, 0x6)
header.append(GetSpiClockParameter(args))
header.append(GetSpiReadCmdParameter(args))
header.extend(struct.pack('<I', LOAD_ADDR))
header.extend(struct.pack('<I', GetEntryPoint(args.input)))
header.append((payload_len >> 6) & 0xff)
header.append((payload_len >> 14) & 0xff)
PadZeroTo(header, 0x14)
header.extend(struct.pack('<I', args.payload_offset))
exp, modulus = GetPublicKey(args.payload_key)
PadZeroTo(header, 0x20)
header.extend(exp)
PadZeroTo(header, 0x30)
header.extend(modulus)
PadZeroTo(header, HEADER_SIZE)
return header
def SignByteArray(data, pem_file):
hash_file = tempfile.mkstemp()[1]
sign_file = tempfile.mkstemp()[1]
with open(hash_file, 'wb') as f:
hasher = hashlib.sha256()
hasher.update(data)
f.write(hasher.digest())
subprocess.check_call(['openssl', 'rsautl', '-sign', '-inkey', pem_file,
'-keyform', 'PEM', '-in', hash_file,
'-out', sign_file])
with open(sign_file, 'rb') as f:
signed = list(f.read())
signed.reverse()
return bytearray(''.join(signed))
def BuildTag(args):
tag = bytearray([(args.header_loc >> 8) & 0xff,
(args.header_loc >> 16) & 0xff,
(args.header_loc >> 24) & 0xff])
if args.chip_select != 0:
tag[2] |= 0x80
tag.append(Crc8(0, tag))
return tag
def main():
parser = argparse.ArgumentParser()
parser.add_argument("-i", "--input",
help="EC binary to pack, usually ec.bin or ec.RO.flat.",
metavar="EC_BIN", default="ec.bin")
parser.add_argument("-o", "--output",
help="Output flash binary file",
metavar="EC_SPI_FLASH", default="ec.packed.bin")
parser.add_argument("--header_key",
help="PEM key file for signing header",
default="rsakey_sign_header.pem")
parser.add_argument("--payload_key",
help="PEM key file for signing payload",
default="rsakey_sign_payload.pem")
parser.add_argument("-s", "--spi_size", type=int,
help="Size of the SPI flash in KB",
default=4096)
parser.add_argument("-l", "--header_loc", type=int,
help="Location of header in SPI flash",
default=0)
parser.add_argument("-p", "--payload_offset", type=int,
help="The offset of payload from the header",
default=0x240)
parser.add_argument("-c", "--chip_select", type=int,
help="Chip select signal to use, either 0 or 1.",
default=0)
parser.add_argument("--spi_clock", type=int,
help="SPI clock speed. 8, 12, 24, or 48 MHz.",
default=24)
parser.add_argument("--spi_read_cmd", type=int,
help="SPI read command. 0x3, 0xB, or 0x3B.",
default=0xb)
args = parser.parse_args()
spi_size = args.spi_size * 1024
spi_list = []
payload = GetPayload(args.input)
payload_len = len(payload)
payload_signature = SignByteArray(payload, args.payload_key)
header = BuildHeader(args, payload_len)
header_signature = SignByteArray(header, args.header_key)
tag = BuildTag(args)
spi_list.append((args.header_loc, header))
spi_list.append((args.header_loc + HEADER_SIZE, header_signature))
spi_list.append((args.header_loc + args.payload_offset, payload))
spi_list.append((args.header_loc + args.payload_offset + payload_len,
payload_signature))
spi_list.append((spi_size - 256, tag))
spi_list = sorted(spi_list)
with open(args.output, 'wb') as f:
addr = 0
for s in spi_list:
assert addr <= s[0]
if addr < s[0]:
f.write('\xff' * (s[0] - addr))
addr = s[0]
f.write(s[1])
addr += len(s[1])
if addr < spi_size:
f.write('\xff' * (spi_size - addr))
if __name__ == '__main__':
main()
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