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#!/usr/bin/python
# Copyright 2015 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.
"""Module for initializing and driving a SPI TPM."""
from __future__ import print_function
import os
import struct
import sys
import traceback
# Suppressing pylint warning about an import not at the top of the file. The
# path needs to be set *before* the last import.
# pylint: disable=C6204
root_dir = os.path.dirname(os.path.abspath(sys.argv[0]))
sys.path.append(os.path.join(root_dir, '..', '..', 'build', 'tpm_test'))
import crypto_test
import ecc_test
import ftdi_spi_tpm
import hash_test
import rsa_test
import subcmd
# Extension command for dcypto testing
EXT_CMD = 0xbaccd00a
class TpmError(Exception):
pass
class TPM(object):
"""TPM accessor class.
Object of this class allows to send valid and extended TPM commands (using
the command() method. The wrap_command/unwrap_response methods provide a
means of encapsulating extended commands in proper TPM data packets, as well
as extracting extended command responses.
Attributes:
_handle: a ftdi_spi_tpm object, a USB/FTDI/SPI driver which allows
communicate with a TPM connected over USB dongle.
"""
HEADER_FMT = '>H2IH'
STARTUP_CMD = '80 01 00 00 00 0c 00 00 01 44 00 00'
STARTUP_RSP = ('80 01 00 00 00 0a 00 00 00 00',
'80 01 00 00 00 0a 00 00 01 00')
def __init__(self, freq=800*1000, debug_mode=False):
self._debug_enabled = debug_mode
self._handle = ftdi_spi_tpm
if not self._handle.FtdiSpiInit(freq, debug_mode):
raise TpmError()
response = self.command(''.join('%c' % int('0x%s' % x, 16)
for x in self.STARTUP_CMD.split()))
if ' '.join('%2.2x' % ord(x) for x in response) not in self.STARTUP_RSP:
raise TpmError('init failed')
def validate(self, data_blob, response_mode=False):
"""Check if a data blob complies with TPM command/response header format."""
(tag, size, cmd_code, _) = struct.unpack_from(
self.HEADER_FMT, data_blob + ' ')
prefix = 'Misformatted blob: '
if tag not in (0x8001, 0x8002):
raise TpmError(prefix + 'bad tag value 0x%4.4x' % tag)
if size != len(data_blob):
raise TpmError(prefix + 'size mismatch: header %d, actual %d' %
(size, len(data_blob)))
if size > 4096:
raise TpmError(prefix + 'invalid size %d' % size)
if response_mode:
return
if cmd_code >= 0x11f and cmd_code <= 0x18f:
return # This is a valid command
if cmd_code == EXT_CMD:
return # This is an extension command
raise TpmError(prefix + 'invalid command code 0x%x' % cmd_code)
def command(self, cmd_data):
# Verify command header
self.validate(cmd_data)
response = self._handle.FtdiSendCommandAndWait(cmd_data)
self.validate(response, response_mode=True)
return response
def wrap_ext_command(self, subcmd_code, cmd_body):
return struct.pack(self.HEADER_FMT, 0x8001,
len(cmd_body) + struct.calcsize(self.HEADER_FMT),
EXT_CMD, subcmd_code) + cmd_body
def unwrap_ext_response(self, expected_subcmd, response):
"""Verify basic validity and strip off TPM extended command header.
Get the response generated by the device, as it came off the wire, verify
that header fields match expectations, then strip off the extension
command header and return the payload to the caller.
Args:
expected_subcmd: an int, up to 16 bits in size, the extension command
this response is supposed to be for.
response: a binary string, the actual response received over the wire.
Returns:
the binary string of the response payload, if validation succeeded.
Raises:
TpmError: in case there are any validation problems, the error message
describes the problem.
"""
header_size = struct.calcsize(self.HEADER_FMT)
tag, size, cmd, subcmd = struct.unpack(self.HEADER_FMT,
response[:header_size])
if tag != 0x8001:
raise TpmError('Wrong response tag: %4.4x' % tag)
if cmd != EXT_CMD:
raise TpmError('Unexpected response command field: %8.8x' % cmd)
if subcmd != expected_subcmd:
raise TpmError('Unexpected response subcommand field: %2.2x' %
subcmd)
if size != len(response):
raise TpmError('Size mismatch: header %d, actual %d' % (
size, len(response)))
return response[header_size:]
def debug_enabled(self):
return self._debug_enabled
if __name__ == '__main__':
try:
debug_needed = len(sys.argv) == 2 and sys.argv[1] == '-d'
t = TPM(debug_mode=debug_needed)
crypto_test.crypto_tests(t, os.path.join(root_dir, 'crypto_test.xml'))
ecc_test.ecc_test(t)
hash_test.hash_test(t)
rsa_test.rsa_test(t)
except (TpmError, crypto_test.CryptoError, hash_test.HashError,
rsa_test.RSAError) as e:
print()
print('Error:', e)
if debug_needed:
traceback.print_exc()
sys.exit(1)
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