151 lines
5 KiB
Python
151 lines
5 KiB
Python
#!/usr/bin/env python3
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import hashlib
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import hmac
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import struct
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import os
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import random
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from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
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from cryptography.hazmat.primitives.asymmetric import rsa
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from cryptography.hazmat.backends import default_backend
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from cryptography.utils import int_to_bytes
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def number_as_bignum_words(number):
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"""
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Given a number, format result as a C array of words
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(little-endian, same as ESP32 RSA peripheral or mbedTLS)
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"""
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result = []
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while number != 0:
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result.append("0x%08x" % (number & 0xFFFFFFFF))
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number >>= 32
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return "{ " + ", ".join(result) + " }"
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def number_as_bytes(number, pad_bits=None):
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"""
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Given a number, format as a little endian array of bytes
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"""
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result = int_to_bytes(number)[::-1]
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while pad_bits is not None and len(result) < (pad_bits // 8):
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result += b'\x00'
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return result
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def bytes_as_char_array(b):
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"""
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Given a sequence of bytes, format as a char array
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"""
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return "{ " + ", ".join("0x%02x" % x for x in b) + " }"
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NUM_HMAC_KEYS = 3
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NUM_MESSAGES = 10
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NUM_CASES = 6
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hmac_keys = [os.urandom(32) for x in range(NUM_HMAC_KEYS)]
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messages = [random.randrange(0, 1 << 4096) for x in range(NUM_MESSAGES)]
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with open("digital_signature_test_cases.h", "w") as f:
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f.write("/* File generated by gen_digital_signature_tests.py */\n\n")
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# Write out HMAC keys
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f.write("#define NUM_HMAC_KEYS %d\n\n" % NUM_HMAC_KEYS)
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f.write("static const uint8_t test_hmac_keys[NUM_HMAC_KEYS][32] = {\n")
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for h in hmac_keys:
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f.write(" %s,\n" % bytes_as_char_array(h))
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f.write("};\n\n")
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# Write out messages
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f.write("#define NUM_MESSAGES %d\n\n" % NUM_MESSAGES)
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f.write("static const uint32_t test_messages[NUM_MESSAGES][4096/32] = {\n")
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for m in messages:
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f.write(" // Message %d\n" % messages.index(m))
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f.write(" %s,\n" % number_as_bignum_words(m))
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f.write(" };\n")
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f.write("\n\n\n")
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f.write("#define NUM_CASES %d\n\n" % NUM_CASES)
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f.write("static const encrypt_testcase_t test_cases[NUM_CASES] = {\n")
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for case in range(NUM_CASES):
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f.write(" { /* Case %d */\n" % case)
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iv = os.urandom(16)
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f.write(" .iv = %s,\n" % (bytes_as_char_array(iv)))
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hmac_key_idx = random.randrange(0, NUM_HMAC_KEYS)
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aes_key = hmac.HMAC(hmac_keys[hmac_key_idx], b"\xFF" * 32, hashlib.sha256).digest()
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sizes = [4096, 3072, 2048, 1024, 512]
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key_size = sizes[case % len(sizes)]
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private_key = rsa.generate_private_key(
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public_exponent=65537,
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key_size=key_size,
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backend=default_backend())
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priv_numbers = private_key.private_numbers()
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pub_numbers = private_key.public_key().public_numbers()
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Y = priv_numbers.d
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M = pub_numbers.n
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rr = 1 << (key_size * 2)
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rinv = rr % pub_numbers.n
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mprime = - rsa._modinv(M, 1 << 32)
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mprime &= 0xFFFFFFFF
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length = key_size // 32 - 1
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f.write(" .p_data = {\n")
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f.write(" .Y = %s,\n" % number_as_bignum_words(Y))
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f.write(" .M = %s,\n" % number_as_bignum_words(M))
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f.write(" .Rb = %s,\n" % number_as_bignum_words(rinv))
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f.write(" .M_prime = 0x%08x,\n" % mprime)
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f.write(" .length = %d, // %d bit\n" % (length, key_size))
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f.write(" },\n")
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# calculate MD from preceding values and IV
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# Y4096 || M4096 || Rb4096 || M_prime32 || LENGTH32 || IV128
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md_in = number_as_bytes(Y, 4096) + \
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number_as_bytes(M, 4096) + \
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number_as_bytes(rinv, 4096) + \
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struct.pack("<II", mprime, length) + \
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iv
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assert len(md_in) == 12480 / 8
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md = hashlib.sha256(md_in).digest()
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# generate expected C value from P bitstring
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#
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# Y4096 || M4096 || Rb4096 || M_prime32 || LENGTH32 || MD256 || 0x08*8
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p = number_as_bytes(Y, 4096) + \
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number_as_bytes(M, 4096) + \
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number_as_bytes(rinv, 4096) + \
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md + \
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struct.pack("<II", mprime, length) + \
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b'\x08' * 8
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assert len(p) == 12672 / 8
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cipher = Cipher(algorithms.AES(aes_key), modes.CBC(iv), backend=default_backend())
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encryptor = cipher.encryptor()
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c = encryptor.update(p) + encryptor.finalize()
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f.write(" .expected_c = %s,\n" % bytes_as_char_array(c))
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f.write(" .hmac_key_idx = %d,\n" % (hmac_key_idx))
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f.write(" // results of message array encrypted with these keys\n")
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f.write(" .expected_results = {\n")
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mask = (1 << key_size) - 1 # truncate messages if needed
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for m in messages:
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f.write(" // Message %d\n" % messages.index(m))
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f.write(" %s," % (number_as_bignum_words(pow(m & mask, Y, M))))
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f.write(" },\n")
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f.write(" },\n")
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f.write("};\n")
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