def startTLS(self, contextFactory, client, bytes=None):
"""
Add a layer of TLS, with SSL parameters defined by the given
contextFactory.
If *client* is True, this side of the connection will be an
SSL client. Otherwise it will be an SSL server.
If extra bytes which may be (or almost certainly are) part of
the SSL handshake were received by the protocol running on top
of OnionProtocol, they must be passed here as the **bytes**
parameter.
"""
# The newest TLS session is spliced in between the previous
# and the application protocol at the tail end of the list.
tlsProtocol = TLSMemoryBIOProtocol(None, self._tailProtocol, False)
tlsProtocol.factory = TLSMemoryBIOFactory(contextFactory, client, None)
if self._currentProtocol is self._tailProtocol:
# This is the first and thus outermost TLS session. The
# transport is the immutable sentinel that no startTLS or
# stopTLS call will move within the linked list stack.
# The wrappedProtocol will remain this outermost session
# until it's terminated.
self.wrappedProtocol = tlsProtocol
nextTransport = PopOnDisconnectTransport(original=self.transport,
pop=self._pop)
# Store the proxied transport as the list's head sentinel
# to enable an easy identity check in _pop.
self._headTransport = nextTransport
else:
# This a later TLS session within the stack. The previous
# TLS session becomes its transport.
nextTransport = PopOnDisconnectTransport(
original=self._currentProtocol, pop=self._pop)
# Splice the new TLS session into the linked list stack.
# wrappedProtocol serves as the link, so the protocol at the
# current position takes our new TLS session as its
# wrappedProtocol.
self._currentProtocol.wrappedProtocol = tlsProtocol
# Move down one position in the linked list.
self._currentProtocol = tlsProtocol
# Expose the new, innermost TLS session as the transport to
# the application protocol.
self.transport = self._currentProtocol
# Connect the new TLS session to the previous transport. The
# transport attribute also serves as the previous link.
tlsProtocol.makeConnection(nextTransport)
# Left over bytes are part of the latest handshake. Pass them
# on to the innermost TLS session.
if bytes is not None:
tlsProtocol.dataReceived(bytes)
