from __future__ import absolute_import import six class Masker(object): """ Data sent from the server must be masked to prevent malicious clients from sending data over the wire in predictable patterns. Servers do not have to mask data they send to the client. https://tools.ietf.org/html/rfc6455#section-5.3 """ def __init__(self, key): self.key = key self.offset = 0 def mask(self, offset, data): result = bytearray(data) for i in range(len(data)): if six.PY2: result[i] ^= ord(self.key[offset % 4]) else: result[i] ^= self.key[offset % 4] offset += 1 result = bytes(result) return result def __call__(self, data): ret = self.mask(self.offset, data) self.offset += len(ret) return ret