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1from operator import or_ as bit_or
2from operator import xor as bit_xor
3from itertools import imap
4import hmac
5from pack.util import codec
6
7class CookieStore(object):
8  def __init__(self, secret_key):
9    if not secret_key:
10      self.secret_key = secure_random_bytes(16)
11    elif isinstance(secret_key, str):
12      self.secret_key = get_bytes(secret_key)
13    else:
14      self.secret_key = secret_key
15  def read_session(self, data):
16    if data:
17      return unseal(self.secret_key, data)
18    else:
19      return {}
20  def write_session(self, _, data):
21    return seal(self.secret_key, data)
22  def delete_session(self, _):
23    return seal(self.secret_key, {})
24
25def seal(key, data):
26  data = encrypt(key, get_bytes(repr(data)))
27  return "%s--%s" % (codec.base64_encode(data), hmac(key, data))
28
29def unseal(key, string):
30  "Restore a sealed object from a string."
31  data, mac = string.split("--")
32  data = codec.base64_decode(data)
33  if secure_compare(mac, hmac(key, data)):
34    return read_string(decrypt(key, data))
35
36def encrypt(key, data):
37  cipher = 
38
39def decrypt(key, data):
40  cipher = 
41
42def hmac(key, data):
43  return codec.base64_encode(hmac.new(key, data, hashlib.sha256).digest())
44
45def secure_compare(a, b):
46  if a and b and len(a) == len(b):
47    return 0 == reduce(bit_or,
48      imap(bit_xor, get_bytes(a), get_bytes(b)))
49  else:
50    return False
51
52def secure_random_bytes(size):
53  seed = bytearray
54
55def get_bytes(string):
56  return [ord(x) for x in string]