# Huge thanks to Cairnarvon
# https://gist.github.com/Cairnarvon/5075687

# Initial permutation
IP = (
	58, 50, 42, 34, 26, 18, 10, 2,
	60, 52, 44, 36, 28, 20, 12, 4,
	62, 54, 46, 38, 30, 22, 14, 6,
	64, 56, 48, 40, 32, 24, 16, 8,
	57, 49, 41, 33, 25, 17,  9, 1,
	59, 51, 43, 35, 27, 19, 11, 3,
	61, 53, 45, 37, 29, 21, 13, 5,
	63, 55, 47, 39, 31, 23, 15, 7,
)

# Final permutation, FP = IP^(-1)
FP = (
	40, 8, 48, 16, 56, 24, 64, 32,
	39, 7, 47, 15, 55, 23, 63, 31,
	38, 6, 46, 14, 54, 22, 62, 30,
	37, 5, 45, 13, 53, 21, 61, 29,
	36, 4, 44, 12, 52, 20, 60, 28,
	35, 3, 43, 11, 51, 19, 59, 27,
	34, 2, 42, 10, 50, 18, 58, 26,
	33, 1, 41,  9, 49, 17, 57, 25,
)

# Permuted-choice 1 from the key bits to yield C and D.
# Note that bits 8,16... are left out: They are intended for a parity check.
PC1_C = (
	57, 49, 41, 33, 25, 17,  9,
	1, 58, 50, 42, 34, 26, 18,
	10,  2, 59, 51, 43, 35, 27,
	19, 11,  3, 60, 52, 44, 36,
)
PC1_D = (
	63, 55, 47, 39, 31, 23, 15,
	 7, 62, 54, 46, 38, 30, 22,
	14,  6, 61, 53, 45, 37, 29,
	21, 13,  5, 28, 20, 12,  4,
)

# Permuted-choice 2, to pick out the bits from the CD array that generate the
# key schedule.
PC2_C = (
	14, 17, 11, 24,  1,  5,
	 3, 28, 15,  6, 21, 10,
	23, 19, 12,  4, 26,  8,
	16,  7, 27, 20, 13,  2,
)
PC2_D = (
	41, 52, 31, 37, 47, 55,
	30, 40, 51, 45, 33, 48,
	44, 49, 39, 56, 34, 53,
	46, 42, 50, 36, 29, 32,
)

# The C and D arrays are used to calculate the key schedule.
C = [0] * 28
D = [0] * 28

# The key schedule. Generated from the key.
KS = [[0] * 48 for _ in range(16)]

# The E bit-selection table.
E = [0] * 48
e2 = (
	32,  1,  2,  3,  4,  5,
	 4,  5,  6,  7,  8,  9,
	 8,  9, 10, 11, 12, 13,
	12, 13, 14, 15, 16, 17,
	16, 17, 18, 19, 20, 21,
	20, 21, 22, 23, 24, 25,
	24, 25, 26, 27, 28, 29,
	28, 29, 30, 31, 32,  1,
)

# S-boxes.
S = (
	(
		14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
		 0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
		 4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
		15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
	),
	(
		15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
		 3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
		 0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
		13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
	),
	(
		10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
		13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
		13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
		 1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
	),
	(
		 7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
		13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
		10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
		 3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
	),
	(
		 2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
		14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
		 4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
		11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
	),
	(
		12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
		10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
		 9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
		 4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
	),
	(
		 4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
		13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
		 1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
		 6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
	),
	(
		13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
		 1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
		 7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
		 2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
	)
)

# P is a permutation on the selected combination of the current L and key.
P = (
	16,  7, 20, 21,
	29, 12, 28, 17,
	 1, 15, 23, 26,
	 5, 18, 31, 10,
	 2,  8, 24, 14,
	32, 27,  3,  9,
	19, 13, 30,  6,
	22, 11,  4, 25,
)

# The combination of the key and the input, before selection.
preS = [0] * 48


def __setkey(key):
	"""
	Set up the key schedule from the encryption key.
	"""
	global C, D, KS, E

	shifts = (1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1)

	# First, generate C and D by permuting the key. The lower order bit of each
	# 8-bit char is not used, so C and D are only 28 bits apiece.
	for i in range(28):
		C[i] = key[PC1_C[i] - 1]
		D[i] = key[PC1_D[i] - 1]

	for i in range(16):
		# rotate
		for k in range(shifts[i]):
			temp = C[0]

			for j in range(27):
				C[j] = C[j + 1]

			C[27] = temp
			temp = D[0]
			for j in range(27):
				D[j] = D[j + 1]

			D[27] = temp

		# get Ki. Note C and D are concatenated
		for j in range(24):
			KS[i][j] = C[PC2_C[j] - 1]
			KS[i][j + 24] = D[PC2_D[j] - 28 - 1]

	# load E with the initial E bit selections
	for i in range(48):
		E[i] = e2[i]

def __encrypt(block):
	global preS

	left, right = [], []	# block in two halves
	f = [0] * 32

	# First, permute the bits in the input
	for j in range(32):
		left.append(block[IP[j] - 1])

	for j in range(32, 64):
		right.append(block[IP[j] - 1])

	# Perform an encryption operation 16 times.
	for i in range(16):
		# Save the right array, which will be the new left.
		old = right[:]

		# Expand right to 48 bits using the E selector and exclusive-or with
		# the current key bits.
		for j in range(48):
			preS[j] = right[E[j] - 1] ^ KS[i][j]

		# The pre-select bits are now considered in 8 groups of 6 bits each.
		# The 8 selection functions map these 6-bit quantities into 4-bit
		# quantities and the results are permuted to make an f(R, K).
		# The indexing into the selection functions is peculiar; it could be
		# simplified by rewriting the tables.
		for j in range(8):
			temp = 6 * j
			k = S[j][(preS[temp + 0] << 5) +
					 (preS[temp + 1] << 3) +
					 (preS[temp + 2] << 2) +
					 (preS[temp + 3] << 1) +
					 (preS[temp + 4] << 0) +
					 (preS[temp + 5] << 4)]

			temp = 4 * j
			f[temp + 0] = (k >> 3) & 1
			f[temp + 1] = (k >> 2) & 1
			f[temp + 2] = (k >> 1) & 1
			f[temp + 3] = (k >> 0) & 1

		# The new right is left ^ f(R, K).
		# The f here has to be permuted first, though.
		for j in range(32):
			right[j] = left[j] ^ f[P[j] - 1]

		# Finally the new left (the original right) is copied back.
		left = old

	# The output left and right are reversed.
	left, right = right, left

	# The final output gets the inverse permutation of the very original
	for j in range(64):
		i = FP[j]
		if i < 33:
			block[j] = left[i - 1]
		else:
			block[j] = right[i - 33]

	return block

def crypt(pw, salt):
	iobuf = []

	# break pw into 64 bits
	block = []
	for c in pw:
		c = ord(c)
		for j in range(7):
			block.append((c >> (6 - j)) & 1)
		block.append(0)
	block += [0] * (64 - len(block))

	# set key based on pw
	__setkey(block)

	for i in range(2):
		# store salt at beginning of results
		iobuf.append(salt[i])
		c = ord(salt[i])

		if c > ord('Z'):
			c -= 6

		if c > ord('9'):
			c -= 7

		c -= ord('.')

		# use salt to effect the E-bit selection
		for j in range(6):
			if (c >> j) & 1:
				E[6 * i + j], E[6 * i + j + 24] = E[6 * i + j + 24], E[6 * i + j]

	# call DES encryption 25 times using pw as key and initial data = 0
	block = [0] * 66
	for i in range(25):
		block = __encrypt(block)

	# format encrypted block for standard crypt(3) output
	for i in range(11):
		c = 0
		for j in range(6):
			c <<= 1
			c |= block[6 * i + j]

		c += ord('.')
		if c > ord('9'):
			c += 7

		if c > ord('Z'):
			c += 6

		iobuf.append(chr(c))

	return ''.join(iobuf)