# Copyright (C) 2013 by the Massachusetts Institute of Technology.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
# INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
# STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
# OF THE POSSIBILITY OF SUCH DAMAGE.
from binascii import unhexlify
from functools import reduce
from os import urandom
# XXX current status:
# * Done and tested
# - AES encryption, checksum, string2key, prf
# - cf2 (needed for FAST)
# * Still to do:
# - DES enctypes and cksumtypes
# - RC4 exported enctype (if we need it for anything)
# - Unkeyed checksums
# - Special RC4, raw DES/DES3 operations for GSSAPI
# * Difficult or low priority:
# - Camellia not supported by PyCrypto
# - Cipher state only needed for kcmd suite
# - Nonstandard enctypes and cksumtypes like des-hmac-sha1
from struct import pack, unpack
from Cryptodome.Cipher import AES, DES3, ARC4, DES
from Cryptodome.Hash import HMAC, MD4, MD5, SHA
from Cryptodome.Protocol.KDF import PBKDF2
from Cryptodome.Util.number import GCD as gcd
from six import b, PY3, indexbytes
def get_random_bytes(lenBytes):
# We don't really need super strong randomness here to use PyCrypto.Random
return urandom(lenBytes)
class Enctype(object):
DES_CRC = 1
DES_MD4 = 2
DES_MD5 = 3
DES3 = 16
AES128 = 17
AES256 = 18
RC4 = 23
class Cksumtype(object):
CRC32 = 1
MD4 = 2
MD4_DES = 3
MD5 = 7
MD5_DES = 8
SHA1 = 9
SHA1_DES3 = 12
SHA1_AES128 = 15
SHA1_AES256 = 16
HMAC_MD5 = -138
class InvalidChecksum(ValueError):
pass
def _zeropad(s, padsize):
# Return s padded with 0 bytes to a multiple of padsize.
padlen = (padsize - (len(s) % padsize)) % padsize
return s + b'\0'*padlen
def _xorbytes(b1, b2):
# xor two strings together and return the resulting string.
assert len(b1) == len(b2)
return bytearray((x ^ y) for x, y in zip(b1, b2))
def _mac_equal(mac1, mac2):
# Constant-time comparison function. (We can't use HMAC.verify
# since we use truncated macs.)
assert len(mac1) == len(mac2)
res = 0
for x, y in zip(mac1, mac2):
res |= x ^ y
return res == 0
def _nfold(ba, nbytes):
# Convert bytearray to a string of length nbytes using the RFC 3961 nfold
# operation.
# Rotate the bytes in ba to the right by nbits bits.
def rotate_right(ba, nbits):
ba = bytearray(ba)
nbytes, remain = (nbits//8) % len(ba), nbits % 8
return bytearray((ba[i-nbytes] >> remain) | ((ba[i-nbytes-1] << (8-remain)) & 0xff) for i in range(len(ba)))
# Add equal-length strings together with end-around carry.
def add_ones_complement(str1, str2):
n = len(str1)
v = [a + b for a, b in zip(str1, str2)]
# Propagate carry bits to the left until there aren't any left.
while any(x & ~0xff for x in v):
v = [(v[i-n+1]>>8) + (v[i]&0xff) for i in range(n)]
return bytearray(x for x in v)
# Concatenate copies of str to produce the least common multiple
# of len(str) and nbytes, rotating each copy of str to the right
# by 13 bits times its list position. Decompose the concatenation
# into slices of length nbytes, and add them together as
# big-endian ones' complement integers.
slen = len(ba)
lcm = nbytes * slen // gcd(nbytes, slen)
bigstr = bytearray()
for i in range(lcm//slen):
bigstr += rotate_right(ba, 13 * i)
slices = (bigstr[p:p+nbytes] for p in range(0, lcm, nbytes))
return bytes(reduce(add_ones_complement, slices))
def _is_weak_des_key(keybytes):
return keybytes in (b'\x01\x01\x01\x01\x01\x01\x01\x01',
b'\xFE\xFE\xFE\xFE\xFE\xFE\xFE\xFE',
b'\x1F\x1F\x1F\x1F\x0E\x0E\x0E\x0E',
b'\xE0\xE0\xE0\xE0\xF1\xF1\xF1\xF1',
b'\x01\xFE\x01\xFE\x01\xFE\x01\xFE',
b'\xFE\x01\xFE\x01\xFE\x01\xFE\x01',
b'\x1F\xE0\x1F\xE0\x0E\xF1\x0E\xF1',
b'\xE0\x1F\xE0\x1F\xF1\x0E\xF1\x0E',
b'\x01\xE0\x01\xE0\x01\xF1\x01\xF1',
b'\xE0\x01\xE0\x01\xF1\x01\xF1\x01',
b'\x1F\xFE\x1F\xFE\x0E\xFE\x0E\xFE',
b'\xFE\x1F\xFE\x1F\xFE\x0E\xFE\x0E',
b'\x01\x1F\x01\x1F\x01\x0E\x01\x0E',
b'\x1F\x01\x1F\x01\x0E\x01\x0E\x01',
b'\xE0\xFE\xE0\xFE\xF1\xFE\xF1\xFE',
b'\xFE\xE0\xFE\xE0\xFE\xF1\xFE\xF1')
class _EnctypeProfile(object):
# Base class for enctype profiles. Usable enctype classes must define:
# * enctype: enctype number
# * keysize: protocol size of key in bytes
# * seedsize: random_to_key input size in bytes
# * random_to_key (if the keyspace is not dense)
# * string_to_key
# * encrypt
# * decrypt
# * prf
@classmethod
def random_to_key(cls, seed):
172 ↛ 173line 172 didn't jump to line 173, because the condition on line 172 was never true if len(seed) != cls.seedsize:
raise ValueError('Wrong seed length')
return Key(cls.enctype, seed)
class _SimplifiedEnctype(_EnctypeProfile):
# Base class for enctypes using the RFC 3961 simplified profile.
# Defines the encrypt, decrypt, and prf methods. Subclasses must
# define:
# * blocksize: Underlying cipher block size in bytes
# * padsize: Underlying cipher padding multiple (1 or blocksize)
# * macsize: Size of integrity MAC in bytes
# * hashmod: PyCrypto hash module for underlying hash function
# * basic_encrypt, basic_decrypt: Underlying CBC/CTS cipher
@classmethod
def derive(cls, key, constant):
# RFC 3961 only says to n-fold the constant only if it is
# shorter than the cipher block size. But all Unix
# implementations n-fold constants if their length is larger
# than the block size as well, and n-folding when the length
# is equal to the block size is a no-op.
plaintext = _nfold(constant, cls.blocksize)
rndseed = b''
while len(rndseed) < cls.seedsize:
ciphertext = cls.basic_encrypt(key, plaintext)
rndseed += ciphertext
plaintext = ciphertext
return cls.random_to_key(rndseed[0:cls.seedsize])
@classmethod
def encrypt(cls, key, keyusage, plaintext, confounder):
ki = cls.derive(key, pack('>IB', keyusage, 0x55))
ke = cls.derive(key, pack('>IB', keyusage, 0xAA))
if confounder is None:
confounder = get_random_bytes(cls.blocksize)
basic_plaintext = confounder + _zeropad(plaintext, cls.padsize)
hmac = HMAC.new(ki.contents, basic_plaintext, cls.hashmod).digest()
return cls.basic_encrypt(ke, basic_plaintext) + hmac[:cls.macsize]
@classmethod
def decrypt(cls, key, keyusage, ciphertext):
ki = cls.derive(key, pack('>IB', keyusage, 0x55))
ke = cls.derive(key, pack('>IB', keyusage, 0xAA))
216 ↛ 217line 216 didn't jump to line 217, because the condition on line 216 was never true if len(ciphertext) < cls.blocksize + cls.macsize:
raise ValueError('ciphertext too short')
basic_ctext, mac = bytearray(ciphertext[:-cls.macsize]), bytearray(ciphertext[-cls.macsize:])
219 ↛ 220line 219 didn't jump to line 220, because the condition on line 219 was never true if len(basic_ctext) % cls.padsize != 0:
raise ValueError('ciphertext does not meet padding requirement')
basic_plaintext = cls.basic_decrypt(ke, bytes(basic_ctext))
hmac = bytearray(HMAC.new(ki.contents, basic_plaintext, cls.hashmod).digest())
expmac = hmac[:cls.macsize]
224 ↛ 225line 224 didn't jump to line 225, because the condition on line 224 was never true if not _mac_equal(mac, expmac):
raise InvalidChecksum('ciphertext integrity failure')
# Discard the confounder.
return bytes(basic_plaintext[cls.blocksize:])
@classmethod
def prf(cls, key, string):
# Hash the input. RFC 3961 says to truncate to the padding
# size, but implementations truncate to the block size.
hashval = cls.hashmod.new(string).digest()
truncated = hashval[:-(len(hashval) % cls.blocksize)]
# Encrypt the hash with a derived key.
kp = cls.derive(key, b'prf')
return cls.basic_encrypt(kp, truncated)
class _DESCBC(_SimplifiedEnctype):
enctype = Enctype.DES_MD5
keysize = 8
seedsize = 8
blocksize = 8
padsize = 8
macsize = 16
hashmod = MD5
@classmethod
def encrypt(cls, key, keyusage, plaintext, confounder):
if confounder is None:
confounder = get_random_bytes(cls.blocksize)
basic_plaintext = confounder + b'\x00'*cls.macsize + _zeropad(plaintext, cls.padsize)
checksum = cls.hashmod.new(basic_plaintext).digest()
basic_plaintext = basic_plaintext[:len(confounder)] + checksum + basic_plaintext[len(confounder)+len(checksum):]
return cls.basic_encrypt(key, basic_plaintext)
@classmethod
def decrypt(cls, key, keyusage, ciphertext):
if len(ciphertext) < cls.blocksize + cls.macsize:
raise ValueError('ciphertext too short')
complex_plaintext = cls.basic_decrypt(key, ciphertext)
cofounder = complex_plaintext[:cls.padsize]
mac = complex_plaintext[cls.padsize:cls.padsize+cls.macsize]
message = complex_plaintext[cls.padsize+cls.macsize:]
expmac = cls.hashmod.new(cofounder+b'\x00'*cls.macsize+message).digest()
if not _mac_equal(mac, expmac):
raise InvalidChecksum('ciphertext integrity failure')
return bytes(message)
@classmethod
def mit_des_string_to_key(cls,string,salt):
def fixparity(deskey):
temp = b''
for i in range(len(deskey)):
t = (bin(indexbytes(deskey,i))[2:]).rjust(8,'0')
if t[:7].count('1') %2 == 0:
temp+= b(chr(int(t[:7]+'1',2)))
else:
temp+= b(chr(int(t[:7]+'0',2)))
return temp
def addparity(l1):
temp = list()
for byte in l1:
if (bin(byte).count('1') % 2) == 0:
byte = (byte << 1)|0b00000001
else:
byte = (byte << 1)&0b11111110
temp.append(byte)
return temp
def XOR(l1,l2):
temp = list()
for b1,b2 in zip(l1,l2):
temp.append((b1^b2)&0b01111111)
return temp
odd = True
s = string + salt
tempstring = [0,0,0,0,0,0,0,0]
s = s + b'\x00'*( 8- (len(s)%8)) #pad(s); /* with nulls to 8 byte boundary */
for block in [s[i:i+8] for i in range(0, len(s), 8)]:
temp56 = list()
#removeMSBits
for byte in block:
312 ↛ 315line 312 didn't jump to line 315, because the condition on line 312 was never false if PY3:
temp56.append(byte&0b01111111)
else:
temp56.append(ord(byte)&0b01111111)
#reverse
if odd is False:
bintemp = b''
for byte in temp56:
bintemp += b(bin(byte)[2:].rjust(7,'0'))
bintemp = bintemp[::-1]
temp56 = list()
for bits7 in [bintemp[i:i+7] for i in range(0, len(bintemp), 7)]:
temp56.append(int(bits7,2))
odd = not odd
tempstring = XOR(tempstring,temp56)
tempkey = ''.join(chr(byte) for byte in addparity(tempstring))
333 ↛ 334line 333 didn't jump to line 334, because the condition on line 333 was never true if _is_weak_des_key(tempkey):
tempkey[7] = chr(ord(tempkey[7]) ^ 0xF0)
cipher = DES.new(b(tempkey), DES.MODE_CBC, b(tempkey))
chekcsumkey = cipher.encrypt(s)[-8:]
chekcsumkey = fixparity(chekcsumkey)
339 ↛ 340line 339 didn't jump to line 340, because the condition on line 339 was never true if _is_weak_des_key(chekcsumkey):
chekcsumkey[7] = chr(ord(chekcsumkey[7]) ^ 0xF0)
return Key(cls.enctype, chekcsumkey)
@classmethod
def basic_encrypt(cls, key, plaintext):
assert len(plaintext) % 8 == 0
des = DES.new(key.contents, DES.MODE_CBC, b'\0' * 8)
return des.encrypt(bytes(plaintext))
@classmethod
def basic_decrypt(cls, key, ciphertext):
assert len(ciphertext) % 8 == 0
des = DES.new(key.contents, DES.MODE_CBC, b'\0' * 8)
return des.decrypt(bytes(ciphertext))
@classmethod
def string_to_key(cls, string, salt, params):
358 ↛ 359line 358 didn't jump to line 359, because the condition on line 358 was never true if params is not None and params != b'':
raise ValueError('Invalid DES string-to-key parameters')
key = cls.mit_des_string_to_key(string, salt)
return key
class _DES3CBC(_SimplifiedEnctype):
enctype = Enctype.DES3
keysize = 24
seedsize = 21
blocksize = 8
padsize = 8
macsize = 20
hashmod = SHA
@classmethod
def random_to_key(cls, seed):
# XXX Maybe reframe as _DESEnctype.random_to_key and use that
# way from DES3 random-to-key when DES is implemented, since
# MIT does this instead of the RFC 3961 random-to-key.
def expand(seed):
def parity(b):
# Return b with the low-order bit set to yield odd parity.
b &= ~1
return b if bin(b & ~1).count('1') % 2 else b | 1
assert len(seed) == 7
firstbytes = [parity(b & ~1) for b in seed]
lastbyte = parity(sum((seed[i]&1) << i+1 for i in range(7)))
keybytes= bytearray(firstbytes + [lastbyte])
388 ↛ 389line 388 didn't jump to line 389, because the condition on line 388 was never true if _is_weak_des_key(keybytes):
keybytes[7] = keybytes[7] ^ 0xF0
return bytes(keybytes)
seed = bytearray(seed)
393 ↛ 394line 393 didn't jump to line 394, because the condition on line 393 was never true if len(seed) != 21:
raise ValueError('Wrong seed length')
k1, k2, k3 = expand(seed[:7]), expand(seed[7:14]), expand(seed[14:])
return Key(cls.enctype, k1 + k2 + k3)
@classmethod
def string_to_key(cls, string, salt, params):
400 ↛ 401line 400 didn't jump to line 401, because the condition on line 400 was never true if params is not None and params != b'':
raise ValueError('Invalid DES3 string-to-key parameters')
k = cls.random_to_key(_nfold(string + salt, 21))
return cls.derive(k, b'kerberos')
@classmethod
def basic_encrypt(cls, key, plaintext):
assert len(plaintext) % 8 == 0
des3 = DES3.new(key.contents, AES.MODE_CBC, b'\0' * 8)
return des3.encrypt(bytes(plaintext))
@classmethod
def basic_decrypt(cls, key, ciphertext):
assert len(ciphertext) % 8 == 0
des3 = DES3.new(key.contents, AES.MODE_CBC, b'\0' * 8)
return des3.decrypt(bytes(ciphertext))
class _AESEnctype(_SimplifiedEnctype):
# Base class for aes128-cts and aes256-cts.
blocksize = 16
padsize = 1
macsize = 12
hashmod = SHA
@classmethod
def string_to_key(cls, string, salt, params):
(iterations,) = unpack('>L', params or b'\x00\x00\x10\x00')
prf = lambda p, s: HMAC.new(p, s, SHA).digest()
seed = PBKDF2(string, salt, cls.seedsize, iterations, prf)
tkey = cls.random_to_key(seed)
return cls.derive(tkey, b'kerberos')
@classmethod
def basic_encrypt(cls, key, plaintext):
assert len(plaintext) >= 16
aes = AES.new(key.contents, AES.MODE_CBC, b'\0' * 16)
ctext = aes.encrypt(_zeropad(bytes(plaintext), 16))
if len(plaintext) > 16:
# Swap the last two ciphertext blocks and truncate the
# final block to match the plaintext length.
lastlen = len(plaintext) % 16 or 16
ctext = ctext[:-32] + ctext[-16:] + ctext[-32:-16][:lastlen]
return ctext
@classmethod
def basic_decrypt(cls, key, ciphertext):
assert len(ciphertext) >= 16
aes = AES.new(key.contents, AES.MODE_ECB)
449 ↛ 450line 449 didn't jump to line 450, because the condition on line 449 was never true if len(ciphertext) == 16:
return aes.decrypt(ciphertext)
# Split the ciphertext into blocks. The last block may be partial.
cblocks = [bytearray(ciphertext[p:p+16]) for p in range(0, len(ciphertext), 16)]
lastlen = len(cblocks[-1])
# CBC-decrypt all but the last two blocks.
prev_cblock = bytearray(16)
plaintext = b''
for bb in cblocks[:-2]:
plaintext += _xorbytes(bytearray(aes.decrypt(bytes(bb))), prev_cblock)
prev_cblock = bb
# Decrypt the second-to-last cipher block. The left side of
# the decrypted block will be the final block of plaintext
# xor'd with the final partial cipher block; the right side
# will be the omitted bytes of ciphertext from the final
# block.
bb = bytearray(aes.decrypt(bytes(cblocks[-2])))
lastplaintext =_xorbytes(bb[:lastlen], cblocks[-1])
omitted = bb[lastlen:]
# Decrypt the final cipher block plus the omitted bytes to get
# the second-to-last plaintext block.
plaintext += _xorbytes(bytearray(aes.decrypt(bytes(cblocks[-1]) + bytes(omitted))), prev_cblock)
return plaintext + lastplaintext
class _AES128CTS(_AESEnctype):
enctype = Enctype.AES128
keysize = 16
seedsize = 16
class _AES256CTS(_AESEnctype):
enctype = Enctype.AES256
keysize = 32
seedsize = 32
class _RC4(_EnctypeProfile):
enctype = Enctype.RC4
keysize = 16
seedsize = 16
@staticmethod
def usage_str(keyusage):
# Return a four-byte string for an RFC 3961 keyusage, using
# the RFC 4757 rules. Per the errata, do not map 9 to 8.
table = {3: 8, 23: 13}
msusage = table[keyusage] if keyusage in table else keyusage
return pack('<I', msusage)
@classmethod
def string_to_key(cls, string, salt, params):
utf16string = string.encode('UTF-16LE')
return Key(cls.enctype, MD4.new(utf16string).digest())
@classmethod
def encrypt(cls, key, keyusage, plaintext, confounder):
if confounder is None:
confounder = get_random_bytes(8)
ki = HMAC.new(key.contents, cls.usage_str(keyusage), MD5).digest()
cksum = HMAC.new(ki, confounder + plaintext, MD5).digest()
ke = HMAC.new(ki, cksum, MD5).digest()
return cksum + ARC4.new(ke).encrypt(bytes(confounder + plaintext))
@classmethod
def decrypt(cls, key, keyusage, ciphertext):
515 ↛ 516line 515 didn't jump to line 516, because the condition on line 515 was never true if len(ciphertext) < 24:
raise ValueError('ciphertext too short')
cksum, basic_ctext = bytearray(ciphertext[:16]), bytearray(ciphertext[16:])
ki = HMAC.new(key.contents, cls.usage_str(keyusage), MD5).digest()
ke = HMAC.new(ki, cksum, MD5).digest()
basic_plaintext = bytearray(ARC4.new(ke).decrypt(bytes(basic_ctext)))
exp_cksum = bytearray(HMAC.new(ki, basic_plaintext, MD5).digest())
ok = _mac_equal(cksum, exp_cksum)
523 ↛ 525line 523 didn't jump to line 525, because the condition on line 523 was never true if not ok and keyusage == 9:
# Try again with usage 8, due to RFC 4757 errata.
ki = HMAC.new(key.contents, pack('<I', 8), MD5).digest()
exp_cksum = HMAC.new(ki, basic_plaintext, MD5).digest()
ok = _mac_equal(cksum, exp_cksum)
528 ↛ 529line 528 didn't jump to line 529, because the condition on line 528 was never true if not ok:
raise InvalidChecksum('ciphertext integrity failure')
# Discard the confounder.
return bytes(basic_plaintext[8:])
@classmethod
def prf(cls, key, string):
return HMAC.new(key.contents, bytes(string), SHA).digest()
class _ChecksumProfile(object):
# Base class for checksum profiles. Usable checksum classes must
# define:
# * checksum
# * verify (if verification is not just checksum-and-compare)
@classmethod
def verify(cls, key, keyusage, text, cksum):
expected = cls.checksum(key, keyusage, text)
546 ↛ 547line 546 didn't jump to line 547, because the condition on line 546 was never true if not _mac_equal(bytearray(cksum), bytearray(expected)):
raise InvalidChecksum('checksum verification failure')
class _SimplifiedChecksum(_ChecksumProfile):
# Base class for checksums using the RFC 3961 simplified profile.
# Defines the checksum and verify methods. Subclasses must
# define:
# * macsize: Size of checksum in bytes
# * enc: Profile of associated enctype
@classmethod
def checksum(cls, key, keyusage, text):
kc = cls.enc.derive(key, pack('>IB', keyusage, 0x99))
hmac = HMAC.new(kc.contents, text, cls.enc.hashmod).digest()
return hmac[:cls.macsize]
@classmethod
def verify(cls, key, keyusage, text, cksum):
565 ↛ 566line 565 didn't jump to line 566, because the condition on line 565 was never true if key.enctype != cls.enc.enctype:
raise ValueError('Wrong key type for checksum')
super(_SimplifiedChecksum, cls).verify(key, keyusage, text, cksum)
class _SHA1AES128(_SimplifiedChecksum):
macsize = 12
enc = _AES128CTS
class _SHA1AES256(_SimplifiedChecksum):
macsize = 12
enc = _AES256CTS
class _SHA1DES3(_SimplifiedChecksum):
macsize = 20
enc = _DES3CBC
class _HMACMD5(_ChecksumProfile):
@classmethod
def checksum(cls, key, keyusage, text):
ksign = HMAC.new(key.contents, b'signaturekey\0', MD5).digest()
md5hash = MD5.new(_RC4.usage_str(keyusage) + text).digest()
return HMAC.new(ksign, md5hash, MD5).digest()
@classmethod
def verify(cls, key, keyusage, text, cksum):
594 ↛ 595line 594 didn't jump to line 595, because the condition on line 594 was never true if key.enctype != Enctype.RC4:
raise ValueError('Wrong key type for checksum')
super(_HMACMD5, cls).verify(key, keyusage, text, cksum)
_enctype_table = {
Enctype.DES_MD5: _DESCBC,
Enctype.DES3: _DES3CBC,
Enctype.AES128: _AES128CTS,
Enctype.AES256: _AES256CTS,
Enctype.RC4: _RC4
}
_checksum_table = {
Cksumtype.SHA1_DES3: _SHA1DES3,
Cksumtype.SHA1_AES128: _SHA1AES128,
Cksumtype.SHA1_AES256: _SHA1AES256,
Cksumtype.HMAC_MD5: _HMACMD5,
0xffffff76: _HMACMD5
}
def _get_enctype_profile(enctype):
618 ↛ 619line 618 didn't jump to line 619, because the condition on line 618 was never true if enctype not in _enctype_table:
raise ValueError('Invalid enctype %d' % enctype)
return _enctype_table[enctype]
def _get_checksum_profile(cksumtype):
624 ↛ 625line 624 didn't jump to line 625, because the condition on line 624 was never true if cksumtype not in _checksum_table:
raise ValueError('Invalid cksumtype %d' % cksumtype)
return _checksum_table[cksumtype]
class Key(object):
def __init__(self, enctype, contents):
e = _get_enctype_profile(enctype)
632 ↛ 633line 632 didn't jump to line 633, because the condition on line 632 was never true if len(contents) != e.keysize:
raise ValueError('Wrong key length')
self.enctype = enctype
self.contents = contents
def random_to_key(enctype, seed):
e = _get_enctype_profile(enctype)
if len(seed) != e.seedsize:
raise ValueError('Wrong crypto seed length')
return e.random_to_key(seed)
def string_to_key(enctype, string, salt, params=None):
e = _get_enctype_profile(enctype)
return e.string_to_key(string, salt, params)
def encrypt(key, keyusage, plaintext, confounder=None):
e = _get_enctype_profile(key.enctype)
return e.encrypt(key, keyusage, bytes(plaintext), bytes(confounder))
def decrypt(key, keyusage, ciphertext):
# Throw InvalidChecksum on checksum failure. Throw ValueError on
# invalid key enctype or malformed ciphertext.
e = _get_enctype_profile(key.enctype)
return e.decrypt(key, keyusage, ciphertext)
def prf(key, string):
e = _get_enctype_profile(key.enctype)
return e.prf(key, string)
def make_checksum(cksumtype, key, keyusage, text):
c = _get_checksum_profile(cksumtype)
return c.checksum(key, keyusage, text)
def verify_checksum(cksumtype, key, keyusage, text, cksum):
# Throw InvalidChecksum exception on checksum failure. Throw
# ValueError on invalid cksumtype, invalid key enctype, or
# malformed checksum.
c = _get_checksum_profile(cksumtype)
c.verify(key, keyusage, text, cksum)
def cf2(enctype, key1, key2, pepper1, pepper2):
# Combine two keys and two pepper strings to produce a result key
# of type enctype, using the RFC 6113 KRB-FX-CF2 function.
def prfplus(key, pepper, l):
# Produce l bytes of output using the RFC 6113 PRF+ function.
out = b''
count = 1
while len(out) < l:
out += prf(key, b(chr(count)) + pepper)
count += 1
return out[:l]
e = _get_enctype_profile(enctype)
return e.random_to_key(_xorbytes(bytearray(prfplus(key1, pepper1, e.seedsize)),
bytearray(prfplus(key2, pepper2, e.seedsize))))
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