diff options
| -rwxr-xr-x | chip/mec1322/util/pack_ec.py | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/chip/mec1322/util/pack_ec.py b/chip/mec1322/util/pack_ec.py new file mode 100755 index 0000000000..6039b3c10b --- /dev/null +++ b/chip/mec1322/util/pack_ec.py @@ -0,0 +1,159 @@ +#!/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 + +# TODO(crosbug.com/p/24107): Add reference to document on image format. + +import hashlib +import os +import struct +import subprocess +import tempfile + +# TODO(crosbug.com/p/24188): Make these options available as command line +# arguments. +SPI_SIZE = 4 * 1024 * 1024 +HEADER_PEM_FILE = 'rsakey_sign_header.pem' +PAYLOAD_PEM_FILE = 'rsakey_sign_payload.pem' +PAYLOAD_FILE = 'ec.bin' # Set to 'ec.RO.flat' for RO-only image +HEADER_LOCATION = 0x170000 +HEADER_FLAG1 = 0x00 +HEADER_FLAG2 = 0x01 +SPI_READ_CMD = 0x01 +LOAD_ADDR = 0x100000 +SPI_CHIP_SELECT = 0 +HEADER_SIZE = 0x140 +PAYLOAD_OFFSET = 0x240 +OUTPUT_FILE = 'ec.4mb.bin' + +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 PadZeroTo(data, size): + data.extend('\0' * (size - len(data))) + +def BuildHeader(payload_len): + header = bytearray(['C', 'S', 'M', 'S', '\0']) + header.extend([HEADER_FLAG1, HEADER_FLAG2, SPI_READ_CMD]) + header.extend(struct.pack('<I', LOAD_ADDR)) + header.extend(struct.pack('<I', GetEntryPoint(PAYLOAD_FILE))) + header.append((payload_len >> 6) & 0xff) + header.append((payload_len >> 14) & 0xff) + PadZeroTo(header, 0x14) + header.extend(struct.pack('<I', PAYLOAD_OFFSET)) + + exp, modulus = GetPublicKey(PAYLOAD_PEM_FILE) + 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(header_loc): + tag = bytearray([(header_loc >> 8) & 0xff, + (header_loc >> 16) & 0xff, + (header_loc >> 24) & 0xff]) + if SPI_CHIP_SELECT != 0: + tag[2] |= 0x80 + tag.append(Crc8(0, tag)) + return tag + + +def main(): + spi_list = [] + + payload = GetPayload(PAYLOAD_FILE) + payload_len = len(payload) + payload_signature = SignByteArray(payload, PAYLOAD_PEM_FILE) + header = BuildHeader(payload_len) + header_signature = SignByteArray(header, HEADER_PEM_FILE) + tag = BuildTag(HEADER_LOCATION) + + spi_list.append((HEADER_LOCATION, header)) + spi_list.append((HEADER_LOCATION + HEADER_SIZE, header_signature)) + spi_list.append((HEADER_LOCATION + PAYLOAD_OFFSET, payload)) + spi_list.append((HEADER_LOCATION + PAYLOAD_OFFSET + payload_len, + payload_signature)) + spi_list.append((SPI_SIZE - 256, tag)) + + spi_list = sorted(spi_list) + + with open(OUTPUT_FILE, '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() |