diff options
Diffstat (limited to 'test/tpm_test/trng_test.py')
| -rw-r--r-- | test/tpm_test/trng_test.py | 118 |
1 files changed, 96 insertions, 22 deletions
diff --git a/test/tpm_test/trng_test.py b/test/tpm_test/trng_test.py index c4d9395e80..60faa32e99 100644 --- a/test/tpm_test/trng_test.py +++ b/test/tpm_test/trng_test.py @@ -3,21 +3,27 @@ # 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 +from math import gcd +import struct import subcmd import utils -TRNG_TEST_FMT = '>H' +TRNG_TEST_FMT = '>HB' 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 +TRNG_SAMPLE_COUNT = 1000000 # NIST require at least 1000000 of 8-bit samples -def get_random_command(size): +# Command structure, shared out of band with the test running on the target: +# field | size | note +# =================================================================== +# text_len | 2 | number of bytes to read, big endian +# type | 1 | 0 = TRNG, other values reserved for extensions +def get_random_command(size, trng_op): """Encode get_random command""" - return struct.pack(TRNG_TEST_FMT, size) + return struct.pack(TRNG_TEST_FMT, size, trng_op) def get_random_command_rsp(size): """Create expected response to get_random""" @@ -25,29 +31,97 @@ def get_random_command_rsp(size): struct.calcsize(TRNG_TEST_RSP_FMT) + size, 0, TRNG_TEST_CC) +def to_bitstring(s, n=1): + """Split bytes into individual samples -def trng_test(tpm): - """Download entropy samples from TRNG - - Command structure, shared out of band with the test running on the target: + convert input packed byte array to n-bits in a byte representation + used by NIST tests. It's designed to recover sequence of samples + as it comes from TRNG, including the fact that rand_bytes() reverse + byte order in every 32-bit chunk. + """ + out = b'' + val_left = 0 + bits_left = 0 + while s: + val = (struct.unpack('>I', s[0:4].rjust(4, b'\0'))[0] << bits_left) +\ + val_left + bits_left += 8 * len(s[0:4]) + s = s[4:] + while bits_left >= n: + out += struct.pack('B', val & ((1 << n) - 1)) + val >>= n + bits_left -= n + val_left = val + return out - field | size | note - =================================================================== - text_len | 2 | size of the text to process, big endian +def trng_test(tpm, trng_output, trng_mode, tsb=1): + """Download entropy samples from TRNG Args: tpm: a tpm object used to communicate with the device + trng_output: file name + trng_mode: source of randomness [0 - TRNG] + tsb: number of bits in each TRNG sample, should be in sync with + TRNG configuration. Default is 1 bit per sample. Raises: subcmd.TpmTestError: on unexpected target responses """ - with open('/tmp/trng_output', 'wb') as out_file: - for block in range(0, TRNG_SAMPLE_COUNT): + + if trng_mode not in [0]: + raise subcmd.TpmTestError('Unknown random source: %d' % trng_mode) + + # minimal recommended by NIST is 1000 samples per block + # TRNG_SAMPLE_BITS is internal setting for TRNG which is important for + # entropy analysis. TRNG internally gets a 16 bit sample (measurement of + # time to collapse ring oscillator). Then some slice of these bits + # [0:TRNG_SAMPLE_BITS] is added (packed) to TRNG FIFO which has internal + # size of 2048 bits. Reading from TRNG always return 32 bits from FIFO. + # To extract actual samples from packed 32-bit reading, need to reverse + # and split read 32-bit into individual samples, each size TRNG_SAMPLE_BITS + # bits. As it's only possible to read 32 bits at once and TRNG_SAMPLE_BITS + # can be anything from 1 to 16, including non-power of 2, need to ensure + # readings to result in non-fractional number of samples. At the same time + # NIST requires minimum 1000 samples at once, and we also want to reduce + # number of read requests which are adding overhead. + # this variable should be divisible by 4 to match 32bit reads from TRNG + + if not 8 >= tsb > 0: + raise subcmd.TpmTestError('NIST only supports 1 to 8 bits per sample') + + # compute number of bytes, which is multiple of 4 containing whole number + # of samples, each size tsb bits. This a reduction of + # tsb * 32 // gcd(tsb, 32) // 8 + lcm = (tsb * 4) // gcd(tsb, 4) + + # combine reads of small batches if possible, 2032 is max size of TPM + # command response, adjusted to header size + bytes_per_read = (2032 // lcm) * lcm + + samples_per_read = 8 * bytes_per_read // tsb + + if samples_per_read < 1000: + raise subcmd.TpmTestError("Can't meet NIST requirement of min 1000 " + 'samples in batch - %d bytes only contain' + ' %d samples' % (bytes_per_read, + samples_per_read)) + print('TRNG bits per sample = ', tsb, 'Read size (bytes) =', + bytes_per_read, 'Samples per read =', samples_per_read) + + remaining_samples = TRNG_SAMPLE_COUNT + with open(trng_output, 'wb') as out_file: + while remaining_samples: 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')) + get_random_command(bytes_per_read, + trng_mode))) + if response[:12] != get_random_command_rsp(bytes_per_read): + raise subcmd.TpmTestError("Unexpected response to '%s': %s" % + ('trng', utils.hex_dump(response))) + bits = to_bitstring(response[12:], tsb) + bits = bits[:remaining_samples] + out_file.write(bits) + remaining_samples -= len(bits) + print('%s %d%%\r' % (utils.cursor_back(), + ((TRNG_SAMPLE_COUNT - remaining_samples)*100)\ + // TRNG_SAMPLE_COUNT), end='') + print('%sSUCCESS: %s' % (utils.cursor_back(), trng_output)) |