#!/usr/bin/env python3
#
# 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.

# 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

import sys
import os

sys.path.insert(0, "bin/python")
os.environ["PYTHONUNBUFFERED"] = "1"

from math import gcd
from functools import reduce
from struct import pack, unpack
from binascii import crc32, b2a_hex
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import hmac
from cryptography.hazmat.primitives.ciphers import algorithms as ciphers
from cryptography.hazmat.primitives.ciphers import modes
from cryptography.hazmat.primitives.ciphers.base import Cipher
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
from samba.tests import TestCase
from samba.credentials import Credentials
from samba import generate_random_bytes as get_random_bytes
from samba.common import get_string, get_bytes


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_DES3 = 12
    SHA1 = 14
    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 + bytes(padlen)


def _xorbytes(b1, b2):
    # xor two strings together and return the resulting string.
    assert len(b1) == len(b2)
    return bytes([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 SIMPLE_HASH(string, algo_cls):
    hash_ctx = hashes.Hash(algo_cls(), default_backend())
    hash_ctx.update(string)
    return hash_ctx.finalize()


def HMAC_HASH(key, string, algo_cls):
    hmac_ctx = hmac.HMAC(key, algo_cls(), default_backend())
    hmac_ctx.update(string)
    return hmac_ctx.finalize()


def _nfold(str, nbytes):
    # Convert str to a string of length nbytes using the RFC 3961 nfold
    # operation.

    # Rotate the bytes in str to the right by nbits bits.
    def rotate_right(str, nbits):
        nbytes, remain = (nbits // 8) % len(str), nbits % 8
        return bytes([
            (str[i - nbytes] >> remain)
            | (str[i - nbytes - 1] << (8 - remain) & 0xff)
            for i in range(len(str))])

    # 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 bytes([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(str)
    lcm = nbytes * slen // gcd(nbytes, slen)
    bigstr = b''.join((rotate_right(str, 13 * i) for i in range(lcm // slen)))
    slices = (bigstr[p:p + nbytes] for p in range(0, lcm, nbytes))
    return 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):
        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_HASH(ki.contents, basic_plaintext, cls.hashalgo)
        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))
        if len(ciphertext) < cls.blocksize + cls.macsize:
            raise ValueError('ciphertext too short')
        basic_ctext, mac = ciphertext[:-cls.macsize], ciphertext[-cls.macsize:]
        if len(basic_ctext) % cls.padsize != 0:
            raise ValueError('ciphertext does not meet padding requirement')
        basic_plaintext = cls.basic_decrypt(ke, basic_ctext)
        hmac = HMAC_HASH(ki.contents, basic_plaintext, cls.hashalgo)
        expmac = hmac[:cls.macsize]
        if not _mac_equal(mac, expmac):
            raise InvalidChecksum('ciphertext integrity failure')
        # Discard the confounder.
        return 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 = SIMPLE_HASH(string, cls.hashalgo)
        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 _DES3CBC(_SimplifiedEnctype):
    enctype = Enctype.DES3
    keysize = 24
    seedsize = 21
    blocksize = 8
    padsize = 8
    macsize = 20
    hashalgo = hashes.SHA1

    @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 = bytes(parity(b & ~1) for b in seed)
            lastbyte = parity(sum((seed[i] & 1) << i + 1 for i in range(7)))
            keybytes = firstbytes + bytes([lastbyte])
            if _is_weak_des_key(keybytes):
                keybytes = firstbytes + bytes([lastbyte ^ 0xF0])
            return keybytes

        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):
        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
        algo = ciphers.TripleDES(key.contents)
        cbc = modes.CBC(bytes(8))
        encryptor = Cipher(algo, cbc, default_backend()).encryptor()
        ciphertext = encryptor.update(plaintext)
        return ciphertext

    @classmethod
    def basic_decrypt(cls, key, ciphertext):
        assert len(ciphertext) % 8 == 0
        algo = ciphers.TripleDES(key.contents)
        cbc = modes.CBC(bytes(8))
        decryptor = Cipher(algo, cbc, default_backend()).decryptor()
        plaintext = decryptor.update(ciphertext)
        return plaintext


class _AESEnctype(_SimplifiedEnctype):
    # Base class for aes128-cts and aes256-cts.
    blocksize = 16
    padsize = 1
    macsize = 12
    hashalgo = hashes.SHA1

    @classmethod
    def string_to_key(cls, string, salt, params):
        (iterations,) = unpack('>L', params or b'\x00\x00\x10\x00')
        pwbytes = get_bytes(string)
        kdf = PBKDF2HMAC(algorithm=hashes.SHA1(),
                         length=cls.seedsize,
                         salt=salt,
                         iterations=iterations,
                         backend=default_backend())
        seed = kdf.derive(pwbytes)
        tkey = cls.random_to_key(seed)
        return cls.derive(tkey, b'kerberos')

    @classmethod
    def basic_encrypt(cls, key, plaintext):
        assert len(plaintext) >= 16

        algo = ciphers.AES(key.contents)
        cbc = modes.CBC(bytes(16))
        aes_ctx = Cipher(algo, cbc, default_backend())

        def aes_encrypt(plaintext):
            encryptor = aes_ctx.encryptor()
            ciphertext = encryptor.update(plaintext)
            return ciphertext

        ctext = aes_encrypt(_zeropad(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

        algo = ciphers.AES(key.contents)
        cbc = modes.CBC(bytes(16))
        aes_ctx = Cipher(algo, cbc, default_backend())

        def aes_decrypt(ciphertext):
            decryptor = aes_ctx.decryptor()
            plaintext = decryptor.update(ciphertext)
            return plaintext

        if len(ciphertext) == 16:
            return aes_decrypt(ciphertext)
        # Split the ciphertext into blocks.  The last block may be partial.
        cblocks = [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 = bytes(16)
        plaintext = b''
        for b in cblocks[:-2]:
            plaintext += _xorbytes(aes_decrypt(b), prev_cblock)
            prev_cblock = b
        # 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.
        b = aes_decrypt(cblocks[-2])
        lastplaintext = _xorbytes(b[:lastlen], cblocks[-1])
        omitted = b[lastlen:]
        # Decrypt the final cipher block plus the omitted bytes to get
        # the second-to-last plaintext block.
        plaintext += _xorbytes(aes_decrypt(cblocks[-1] + 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):
        utf8string = get_string(string)
        tmp = Credentials()
        tmp.set_anonymous()
        tmp.set_password(utf8string)
        nthash = tmp.get_nt_hash()
        return Key(cls.enctype, nthash)

    @classmethod
    def encrypt(cls, key, keyusage, plaintext, confounder):
        if confounder is None:
            confounder = get_random_bytes(8)
        ki = HMAC_HASH(key.contents, cls.usage_str(keyusage), hashes.MD5)
        cksum = HMAC_HASH(ki, confounder + plaintext, hashes.MD5)
        ke = HMAC_HASH(ki, cksum, hashes.MD5)

        encryptor = Cipher(
            ciphers.ARC4(ke), None, default_backend()).encryptor()
        ctext = encryptor.update(confounder + plaintext)

        return cksum + ctext

    @classmethod
    def decrypt(cls, key, keyusage, ciphertext):
        if len(ciphertext) < 24:
            raise ValueError('ciphertext too short')
        cksum, basic_ctext = ciphertext[:16], ciphertext[16:]
        ki = HMAC_HASH(key.contents, cls.usage_str(keyusage), hashes.MD5)
        ke = HMAC_HASH(ki, cksum, hashes.MD5)

        decryptor = Cipher(
            ciphers.ARC4(ke), None, default_backend()).decryptor()
        basic_plaintext = decryptor.update(basic_ctext)

        exp_cksum = HMAC_HASH(ki, basic_plaintext, hashes.MD5)
        ok = _mac_equal(cksum, exp_cksum)
        if not ok and keyusage == 9:
            # Try again with usage 8, due to RFC 4757 errata.
            ki = HMAC_HASH(key.contents, pack('<i', 8), hashes.MD5)
            exp_cksum = HMAC_HASH(ki, basic_plaintext, hashes.MD5)
            ok = _mac_equal(cksum, exp_cksum)
        if not ok:
            raise InvalidChecksum('ciphertext integrity failure')
        # Discard the confounder.
        return basic_plaintext[8:]

    @classmethod
    def prf(cls, key, string):
        return HMAC_HASH(key.contents, string, hashes.SHA1)


class _ChecksumProfile(object):
    # Base class for checksum profiles.  Usable checksum classes must
    # define:
    #   * checksum
    #   * verify (if verification is not just checksum-and-compare)
    #   * checksum_len
    @classmethod
    def verify(cls, key, keyusage, text, cksum):
        expected = cls.checksum(key, keyusage, text)
        if not _mac_equal(cksum, 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_HASH(kc.contents, text, cls.enc.hashalgo)
        return hmac[:cls.macsize]

    @classmethod
    def verify(cls, key, keyusage, text, cksum):
        if key.enctype != cls.enc.enctype:
            raise ValueError('Wrong key type for checksum')
        super(_SimplifiedChecksum, cls).verify(key, keyusage, text, cksum)

    @classmethod
    def checksum_len(cls):
        return cls.macsize


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_HASH(key.contents, b'signaturekey\0', hashes.MD5)
        md5hash = SIMPLE_HASH(_RC4.usage_str(keyusage) + text, hashes.MD5)
        return HMAC_HASH(ksign, md5hash, hashes.MD5)

    @classmethod
    def verify(cls, key, keyusage, text, cksum):
        if key.enctype != Enctype.RC4:
            raise ValueError('Wrong key type for checksum')
        super(_HMACMD5, cls).verify(key, keyusage, text, cksum)

    @classmethod
    def checksum_len(cls):
        return hashes.MD5.digest_size


class _MD5(_ChecksumProfile):
    @classmethod
    def checksum(cls, key, keyusage, text):
        # This is unkeyed!
        return SIMPLE_HASH(text, hashes.MD5)

    @classmethod
    def checksum_len(cls):
        return hashes.MD5.digest_size


class _SHA1(_ChecksumProfile):
    @classmethod
    def checksum(cls, key, keyusage, text):
        # This is unkeyed!
        return SIMPLE_HASH(text, hashes.SHA1)

    @classmethod
    def checksum_len(cls):
        return hashes.SHA1.digest_size


class _CRC32(_ChecksumProfile):
    @classmethod
    def checksum(cls, key, keyusage, text):
        # This is unkeyed!
        cksum = (~crc32(text, 0xffffffff)) & 0xffffffff
        return pack('<I', cksum)

    @classmethod
    def checksum_len(cls):
        return 4


_enctype_table = {
    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,
    Cksumtype.MD5: _MD5,
    Cksumtype.SHA1: _SHA1,
    Cksumtype.CRC32: _CRC32,
}


def _get_enctype_profile(enctype):
    if enctype not in _enctype_table:
        raise ValueError('Invalid enctype %d' % enctype)
    return _enctype_table[enctype]


def _get_checksum_profile(cksumtype):
    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)
        if len(contents) != e.keysize:
            raise ValueError('Wrong key length')
        self.enctype = enctype
        self.contents = contents

    def __str__(self):
        return "enctype=%d contents=%s" % (self.enctype,
                b2a_hex(self.contents).decode('ascii'))

def seedsize(enctype):
    e = _get_enctype_profile(enctype)
    return e.seedsize


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, plaintext, 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 checksum_len(cksumtype):
    c = _get_checksum_profile(cksumtype)
    return c.checksum_len()


def prfplus(key, pepper, ln):
    # Produce ln bytes of output using the RFC 6113 PRF+ function.
    out = b''
    count = 1
    while len(out) < ln:
        out += prf(key, bytes([count]) + pepper)
        count += 1
    return out[:ln]


def cf2(key1, key2, pepper1, pepper2, enctype=None):
    # Combine two keys and two pepper strings to produce a result key
    # of type enctype, using the RFC 6113 KRB-FX-CF2 function.
    if enctype is None:
        enctype = key1.enctype
    e = _get_enctype_profile(enctype)
    return e.random_to_key(_xorbytes(prfplus(key1, pepper1, e.seedsize),
                                     prfplus(key2, pepper2, e.seedsize)))


def h(hexstr):
    return bytes.fromhex(hexstr)


class KcrytoTest(TestCase):
    """kcrypto Test case."""

    def test_aes128_crypr(self):
        # AES128 encrypt and decrypt
        kb = h('9062430C8CDA3388922E6D6A509F5B7A')
        conf = h('94B491F481485B9A0678CD3C4EA386AD')
        keyusage = 2
        plain = b'9 bytesss'
        ctxt = h('68FB9679601F45C78857B2BF820FD6E53ECA8D42FD4B1D7024A09205ABB7'
                 'CD2EC26C355D2F')
        k = Key(Enctype.AES128, kb)
        self.assertEqual(encrypt(k, keyusage, plain, conf), ctxt)
        self.assertEqual(decrypt(k, keyusage, ctxt), plain)

    def test_aes256_crypt(self):
        # AES256 encrypt and decrypt
        kb = h('F1C795E9248A09338D82C3F8D5B567040B0110736845041347235B14042313'
               '98')
        conf = h('E45CA518B42E266AD98E165E706FFB60')
        keyusage = 4
        plain = b'30 bytes bytes bytes bytes byt'
        ctxt = h('D1137A4D634CFECE924DBC3BF6790648BD5CFF7DE0E7B99460211D0DAEF3'
                 'D79A295C688858F3B34B9CBD6EEBAE81DAF6B734D4D498B6714F1C1D')
        k = Key(Enctype.AES256, kb)
        self.assertEqual(encrypt(k, keyusage, plain, conf), ctxt)
        self.assertEqual(decrypt(k, keyusage, ctxt), plain)

    def test_aes128_checksum(self):
        # AES128 checksum
        kb = h('9062430C8CDA3388922E6D6A509F5B7A')
        keyusage = 3
        plain = b'eight nine ten eleven twelve thirteen'
        cksum = h('01A4B088D45628F6946614E3')
        k = Key(Enctype.AES128, kb)
        verify_checksum(Cksumtype.SHA1_AES128, k, keyusage, plain, cksum)

    def test_aes256_checksum(self):
        # AES256 checksum
        kb = h('B1AE4CD8462AFF1677053CC9279AAC30B796FB81CE21474DD3DDBC'
               'FEA4EC76D7')
        keyusage = 4
        plain = b'fourteen'
        cksum = h('E08739E3279E2903EC8E3836')
        k = Key(Enctype.AES256, kb)
        verify_checksum(Cksumtype.SHA1_AES256, k, keyusage, plain, cksum)

    def test_aes128_string_to_key(self):
        # AES128 string-to-key
        string = b'password'
        salt = b'ATHENA.MIT.EDUraeburn'
        params = h('00000002')
        kb = h('C651BF29E2300AC27FA469D693BDDA13')
        k = string_to_key(Enctype.AES128, string, salt, params)
        self.assertEqual(k.contents, kb)

    def test_aes256_string_to_key(self):
        # AES256 string-to-key
        string = b'X' * 64
        salt = b'pass phrase equals block size'
        params = h('000004B0')
        kb = h('89ADEE3608DB8BC71F1BFBFE459486B05618B70CBAE22092534E56'
               'C553BA4B34')
        k = string_to_key(Enctype.AES256, string, salt, params)
        self.assertEqual(k.contents, kb)

    def test_aes128_prf(self):
        # AES128 prf
        kb = h('77B39A37A868920F2A51F9DD150C5717')
        k = string_to_key(Enctype.AES128, b'key1', b'key1')
        self.assertEqual(prf(k, b'\x01\x61'), kb)

    def test_aes256_prf(self):
        # AES256 prf
        kb = h('0D674DD0F9A6806525A4D92E828BD15A')
        k = string_to_key(Enctype.AES256, b'key2', b'key2')
        self.assertEqual(prf(k, b'\x02\x62'), kb)

    def test_aes128_cf2(self):
        # AES128 cf2
        kb = h('97DF97E4B798B29EB31ED7280287A92A')
        k1 = string_to_key(Enctype.AES128, b'key1', b'key1')
        k2 = string_to_key(Enctype.AES128, b'key2', b'key2')
        k = cf2(k1, k2, b'a', b'b')
        self.assertEqual(k.contents, kb)

    def test_aes256_cf2(self):
        # AES256 cf2
        kb = h('4D6CA4E629785C1F01BAF55E2E548566B9617AE3A96868C337CB93B5'
               'E72B1C7B')
        k1 = string_to_key(Enctype.AES256, b'key1', b'key1')
        k2 = string_to_key(Enctype.AES256, b'key2', b'key2')
        k = cf2(k1, k2, b'a', b'b')
        self.assertEqual(k.contents, kb)

    def test_des3_crypt(self):
        # DES3 encrypt and decrypt
        kb = h('0DD52094E0F41CECCB5BE510A764B35176E3981332F1E598')
        conf = h('94690A17B2DA3C9B')
        keyusage = 3
        plain = b'13 bytes byte'
        ctxt = h('839A17081ECBAFBCDC91B88C6955DD3C4514023CF177B77BF0D0177A16F7'
                 '05E849CB7781D76A316B193F8D30')
        k = Key(Enctype.DES3, kb)
        self.assertEqual(encrypt(k, keyusage, plain, conf), ctxt)
        self.assertEqual(decrypt(k, keyusage, ctxt), _zeropad(plain, 8))

    def test_des3_string_to_key(self):
        # DES3 string-to-key
        string = b'password'
        salt = b'ATHENA.MIT.EDUraeburn'
        kb = h('850BB51358548CD05E86768C313E3BFEF7511937DCF72C3E')
        k = string_to_key(Enctype.DES3, string, salt)
        self.assertEqual(k.contents, kb)

    def test_des3_checksum(self):
        # DES3 checksum
        kb = h('7A25DF8992296DCEDA0E135BC4046E2375B3C14C98FBC162')
        keyusage = 2
        plain = b'six seven'
        cksum = h('0EEFC9C3E049AABC1BA5C401677D9AB699082BB4')
        k = Key(Enctype.DES3, kb)
        verify_checksum(Cksumtype.SHA1_DES3, k, keyusage, plain, cksum)

    def test_des3_cf2(self):
        # DES3 cf2
        kb = h('E58F9EB643862C13AD38E529313462A7F73E62834FE54A01')
        k1 = string_to_key(Enctype.DES3, b'key1', b'key1')
        k2 = string_to_key(Enctype.DES3, b'key2', b'key2')
        k = cf2(k1, k2, b'a', b'b')
        self.assertEqual(k.contents, kb)

    def test_rc4_crypt(self):
        # RC4 encrypt and decrypt
        kb = h('68F263DB3FCE15D031C9EAB02D67107A')
        conf = h('37245E73A45FBF72')
        keyusage = 4
        plain = b'30 bytes bytes bytes bytes byt'
        ctxt = h('95F9047C3AD75891C2E9B04B16566DC8B6EB9CE4231AFB2542EF87A7B5A0'
                 'F260A99F0460508DE0CECC632D07C354124E46C5D2234EB8')
        k = Key(Enctype.RC4, kb)
        self.assertEqual(encrypt(k, keyusage, plain, conf), ctxt)
        self.assertEqual(decrypt(k, keyusage, ctxt), plain)

    def test_rc4_string_to_key(self):
        # RC4 string-to-key
        string = b'foo'
        kb = h('AC8E657F83DF82BEEA5D43BDAF7800CC')
        k = string_to_key(Enctype.RC4, string, None)
        self.assertEqual(k.contents, kb)

    def test_rc4_checksum(self):
        # RC4 checksum
        kb = h('F7D3A155AF5E238A0B7A871A96BA2AB2')
        keyusage = 6
        plain = b'seventeen eighteen nineteen twenty'
        cksum = h('EB38CC97E2230F59DA4117DC5859D7EC')
        k = Key(Enctype.RC4, kb)
        verify_checksum(Cksumtype.HMAC_MD5, k, keyusage, plain, cksum)

    def test_rc4_cf2(self):
        # RC4 cf2
        kb = h('24D7F6B6BAE4E5C00D2082C5EBAB3672')
        k1 = string_to_key(Enctype.RC4, b'key1', b'key1')
        k2 = string_to_key(Enctype.RC4, b'key2', b'key2')
        k = cf2(k1, k2, b'a', b'b')
        self.assertEqual(k.contents, kb)

    def _test_md5_unkeyed_checksum(self, etype, usage):
        # MD5 unkeyed checksum
        pw = b'pwd'
        salt = b'bytes'
        key = string_to_key(etype, pw, salt)
        plain = b'seventeen eighteen nineteen twenty'
        cksum = h('9d9588cdef3a8cefc9d2c208d978f60c')
        verify_checksum(Cksumtype.MD5, key, usage, plain, cksum)

    def test_md5_unkeyed_checksum_des3_usage_40(self):
        return self._test_md5_unkeyed_checksum(Enctype.DES3, 40)

    def test_md5_unkeyed_checksum_des3_usage_50(self):
        return self._test_md5_unkeyed_checksum(Enctype.DES3, 50)

    def test_md5_unkeyed_checksum_rc4_usage_40(self):
        return self._test_md5_unkeyed_checksum(Enctype.RC4, 40)

    def test_md5_unkeyed_checksum_rc4_usage_50(self):
        return self._test_md5_unkeyed_checksum(Enctype.RC4, 50)

    def test_md5_unkeyed_checksum_aes128_usage_40(self):
        return self._test_md5_unkeyed_checksum(Enctype.AES128, 40)

    def test_md5_unkeyed_checksum_aes128_usage_50(self):
        return self._test_md5_unkeyed_checksum(Enctype.AES128, 50)

    def test_md5_unkeyed_checksum_aes256_usage_40(self):
        return self._test_md5_unkeyed_checksum(Enctype.AES256, 40)

    def test_md5_unkeyed_checksum_aes256_usage_50(self):
        return self._test_md5_unkeyed_checksum(Enctype.AES256, 50)

    def _test_sha1_unkeyed_checksum(self, etype, usage):
        # SHA1 unkeyed checksum
        pw = b'password'
        salt = b'salt'
        key = string_to_key(etype, pw, salt)
        plain = b'twenty nineteen eighteen seventeen'
        cksum = h('381c870d8875d1913555de19af5c885fd27b7da9')
        verify_checksum(Cksumtype.SHA1, key, usage, plain, cksum)

    def test_sha1_unkeyed_checksum_des3_usage_40(self):
        return self._test_sha1_unkeyed_checksum(Enctype.DES3, 40)

    def test_sha1_unkeyed_checksum_des3_usage_50(self):
        return self._test_sha1_unkeyed_checksum(Enctype.DES3, 50)

    def test_sha1_unkeyed_checksum_rc4_usage_40(self):
        return self._test_sha1_unkeyed_checksum(Enctype.RC4, 40)

    def test_sha1_unkeyed_checksum_rc4_usage_50(self):
        return self._test_sha1_unkeyed_checksum(Enctype.RC4, 50)

    def test_sha1_unkeyed_checksum_aes128_usage_40(self):
        return self._test_sha1_unkeyed_checksum(Enctype.AES128, 40)

    def test_sha1_unkeyed_checksum_aes128_usage_50(self):
        return self._test_sha1_unkeyed_checksum(Enctype.AES128, 50)

    def test_sha1_unkeyed_checksum_aes256_usage_40(self):
        return self._test_sha1_unkeyed_checksum(Enctype.AES256, 40)

    def test_sha1_unkeyed_checksum_aes256_usage_50(self):
        return self._test_sha1_unkeyed_checksum(Enctype.AES256, 50)

    def _test_crc32_unkeyed_checksum(self, etype, usage):
        # CRC32 unkeyed checksum
        pw = b'password'
        salt = b'salt'
        key = string_to_key(etype, pw, salt)
        plain = b'africa america asia australia europe'
        cksum = h('ce595a53')
        verify_checksum(Cksumtype.CRC32, key, usage, plain, cksum)

    def test_crc32_unkeyed_checksum_des3_usage_40(self):
        return self._test_crc32_unkeyed_checksum(Enctype.DES3, 40)

    def test_crc32_unkeyed_checksum_des3_usage_50(self):
        return self._test_crc32_unkeyed_checksum(Enctype.DES3, 50)

    def test_crc32_unkeyed_checksum_rc4_usage_40(self):
        return self._test_crc32_unkeyed_checksum(Enctype.RC4, 40)

    def test_crc32_unkeyed_checksum_rc4_usage_50(self):
        return self._test_crc32_unkeyed_checksum(Enctype.RC4, 50)

    def test_crc32_unkeyed_checksum_aes128_usage_40(self):
        return self._test_crc32_unkeyed_checksum(Enctype.AES128, 40)

    def test_crc32_unkeyed_checksum_aes128_usage_50(self):
        return self._test_crc32_unkeyed_checksum(Enctype.AES128, 50)

    def test_crc32_unkeyed_checksum_aes256_usage_40(self):
        return self._test_crc32_unkeyed_checksum(Enctype.AES256, 40)

    def test_crc32_unkeyed_checksum_aes256_usage_50(self):
        return self._test_crc32_unkeyed_checksum(Enctype.AES256, 50)


if __name__ == "__main__":
    import unittest
    unittest.main()
