refactor websockets into protocol

1 files changed, 111 insertions, 0 deletions

diff --git a/netlib/websockets/protocol.py b/netlib/websockets/protocol.py
new file mode 100644
index 00000000..dcab53fb
--- /dev/null
+++ b/netlib/websockets/protocol.py
@@ -0,0 +1,111 @@
+from __future__ import absolute_import
+import base64
+import hashlib
+import os
+import struct
+import io
+
+from .. import utils, odict, tcp
+
+# Colleciton of utility functions that implement small portions of the RFC6455
+# WebSockets Protocol Useful for building WebSocket clients and servers.
+#
+# Emphassis is on readabilty, simplicity and modularity, not performance or
+# completeness
+#
+# This is a work in progress and does not yet contain all the utilites need to
+# create fully complient client/servers #
+# Spec: https://tools.ietf.org/html/rfc6455
+
+# The magic sha that websocket servers must know to prove they understand
+# RFC6455
+websockets_magic = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
+VERSION = "13"
+
+HEADER_WEBSOCKET_KEY = 'sec-websocket-key'
+HEADER_WEBSOCKET_ACCEPT = 'sec-websocket-accept'
+HEADER_WEBSOCKET_VERSION = 'sec-websocket-version'
+
+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.masks = [utils.bytes_to_int(byte) for byte in key]
+        self.offset = 0
+
+    def mask(self, offset, data):
+        result = ""
+        for c in data:
+            result += chr(ord(c) ^ self.masks[offset % 4])
+            offset += 1
+        return result
+
+    def __call__(self, data):
+        ret = self.mask(self.offset, data)
+        self.offset += len(ret)
+        return ret
+
+class WebsocketsProtocol(object):
+
+    def __init__(self):
+        pass
+
+    @classmethod
+    def client_handshake_headers(self, key=None, version=VERSION):
+        """
+            Create the headers for a valid HTTP upgrade request. If Key is not
+            specified, it is generated, and can be found in sec-websocket-key in
+            the returned header set.
+
+            Returns an instance of ODictCaseless
+        """
+        if not key:
+            key = base64.b64encode(os.urandom(16)).decode('utf-8')
+        return odict.ODictCaseless([
+            ('Connection', 'Upgrade'),
+            ('Upgrade', 'websocket'),
+            (HEADER_WEBSOCKET_KEY, key),
+            (HEADER_WEBSOCKET_VERSION, version)
+        ])
+
+    @classmethod
+    def server_handshake_headers(self, key):
+        """
+          The server response is a valid HTTP 101 response.
+        """
+        return odict.ODictCaseless(
+            [
+                ('Connection', 'Upgrade'),
+                ('Upgrade', 'websocket'),
+                (HEADER_WEBSOCKET_ACCEPT, self.create_server_nonce(key))
+            ]
+        )
+
+
+    @classmethod
+    def check_client_handshake(self, headers):
+        if headers.get_first("upgrade", None) != "websocket":
+            return
+        return headers.get_first(HEADER_WEBSOCKET_KEY)
+
+
+    @classmethod
+    def check_server_handshake(self, headers):
+        if headers.get_first("upgrade", None) != "websocket":
+            return
+        return headers.get_first(HEADER_WEBSOCKET_ACCEPT)
+
+
+    @classmethod
+    def create_server_nonce(self, client_nonce):
+        return base64.b64encode(
+            hashlib.sha1(client_nonce + websockets_magic).hexdigest().decode('hex')
+        )