[Twisted-Python] TCP startTLS() negotiation
kgeorge at tcpsoft.com
Sat Aug 15 12:49:19 EDT 2009
I've noticed some behavior when negotiating TLS using startTLS(). I'm
starting TLS on both sides of the connection at the same time to validate
peer certificates using a custom callback. If I call startTLS() without
any subsequent writes to the socket the negotiation never completes.
However, if I write data immediately post startTLS() the negotiation (and
the callback to the OpenSSL verify callback) is successful. But I don't
want to do this because I want to wait until verification to proceed with
communicating on the channel. So I traced through tcp.py and noticed that
in Connection.startTLS() reads and writes are stopped while the
negotiation is taking place. However, only reading is reenabled
afterwards. I suppose this is why doing a write unblocks the connection.
When I do something like this in my code I don't have to make a write:
The context factory makes its own SSL.Context very similar to _sslverify,
but with a callback I can hook for verification.
So the question is, why is reading reenabled but not writing? When I
apply the patch below it works.
This is on Python 2.6.2, Twisted 8.2.0, pyOpenSSL-0.9-py2.6, win32.
--- twisted/internet/tcp.py (revision 27226)
+++ twisted/internet/tcp.py (working copy)
@@ -401,6 +401,7 @@
self.socket = SSL.Connection(ctx.getContext(), self.socket)
self.fileno = self.socket.fileno
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