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# -*- coding: utf-8 -*-
# Copyright 2019 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.
"""Tests for trng."""
from __future__ import print_function
import struct
import subcmd
import utils
TRNG_TEST_FMT = '>H'
TRNG_TEST_RSP_FMT = '>H2IH'
TRNG_TEST_CC = 0x33
TRNG_SAMPLE_SIZE = 1000 # minimal recommended by NIST is 1000 bytes per sample
TRNG_SAMPLE_COUNT = 1000 # NIST require at least 1000000 of 8-bit samples
def get_random_command(size):
"""Encode get_random command"""
return struct.pack(TRNG_TEST_FMT, size)
def get_random_command_rsp(size):
"""Create expected response to get_random"""
return struct.pack(TRNG_TEST_RSP_FMT, 0x8001,
struct.calcsize(TRNG_TEST_RSP_FMT) + size,
0, TRNG_TEST_CC)
def trng_test(tpm):
"""Download entropy samples from TRNG
Command structure, shared out of band with the test running on the target:
field | size | note
===================================================================
text_len | 2 | size of the text to process, big endian
Args:
tpm: a tpm object used to communicate with the device
Raises:
subcmd.TpmTestError: on unexpected target responses
"""
with open('/tmp/trng_output', 'wb') as out_file:
for block in range(0, TRNG_SAMPLE_COUNT):
response = tpm.command(tpm.wrap_ext_command(TRNG_TEST_CC,
get_random_command(TRNG_SAMPLE_SIZE)))
if response[:12] != get_random_command_rsp(TRNG_SAMPLE_SIZE):
raise subcmd.TpmTestError("Unexpected response to \'%s\': %s" %
('trng', utils.hex_dump(response)))
out_file.write(response[12:])
print('%s %d%%\r' % (utils.cursor_back(), (block//10)), end='')
print('%sSUCCESS: %s' % (utils.cursor_back(), 'trng'))
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