def unserialize(cls, string, secret_key):
"""Load the secure cookie from a serialized string.
:param string: the cookie value to unserialize.
:param secret_key: the secret key used to serialize the cookie.
:return: a new :class:`SecureCookie`.
"""
if isinstance(string, text_type):
string = string.encode('utf-8', 'replace')
if isinstance(secret_key, text_type):
secret_key = secret_key.encode('utf-8', 'replace')
try:
base64_hash, data = string.split(b'?', 1)
except (ValueError, IndexError):
items = ()
else:
items = {}
mac = hmac(secret_key, None, cls.hash_method)
for item in data.split(b'&'):
mac.update(b'|' + item)
if b'=' not in item:
items = None
break
key, value = item.split(b'=', 1)
# try to make the key a string
key = url_unquote_plus(key.decode('ascii'))
try:
key = to_native(key)
except UnicodeError:
pass
items[key] = value
# no parsing error and the mac looks okay, we can now
# sercurely unpickle our cookie.
try:
client_hash = base64.b64decode(base64_hash)
except TypeError:
items = client_hash = None
if items is not None and safe_str_cmp(client_hash, mac.digest()):
try:
for key, value in iteritems(items):
items[key] = cls.unquote(value)
except UnquoteError:
items = ()
else:
if '_expires' in items:
if time() > items['_expires']:
items = ()
else:
del items['_expires']
else:
items = ()
return cls(items, secret_key, False)
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