Python's SSL module doesn't support DTLS (datagram TLS for UDP). The SSL code doesn't complain when an UDP socket is wrapped in a SSL socket. It happily sends the bytes unprotected and not encrypted over the wire:

>>> import ssl, socket
>>> sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
>>> ssock = ssl.wrap_socket(sock)
>>> ssock.sendto(b"data", ("localhost", 12345))
4

TCP sockets at least complain that the connection hasn't been established yet.

>>> sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> ssock = ssl.wrap_socket(sock)
>>> ssock.sendto(b"data", ("localhost", 12345))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/heimes/dev/python/cpython/Lib/ssl.py", line 517, in sendto
    return socket.sendto(self, data, flags_or_addr)
BrokenPipeError: [Errno 32] Broken pipe

I think either sendto() or wrap_socket() should raise some kind of error for UDP instead of silently sending unencrypted data.

Agreed, this should definitely be fixed.

Attached the patch to raise error when using sock dgram in wrap_socket.

I am still unsure whether I should put the validation in C code (private function _wrap_socket) or not.

Thanks, Antoine, for the review! Attached the patch to address Antoine's concern.

Actually, it seems the patch is flawed:

>>> sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
>>> sock.type
2
>>> sock.settimeout(0)
>>> sock.type
2050

But getsockopt() returns the expected value:

>>> sock.getsockopt(socket.SOL_SOCKET, socket.SO_TYPE)
2

New changeset a00842b783cf by Antoine Pitrou in branch '3.3':
Issue #19422: Explicitly disallow non-SOCK_STREAM sockets in the ssl module, rather than silently let them emit clear text data.
http://hg.python.org/cpython/rev/a00842b783cf

New changeset f7dc02e6987a by Antoine Pitrou in branch 'default':
Issue #19422: Explicitly disallow non-SOCK_STREAM sockets in the ssl module, rather than silently let them emit clear text data.
http://hg.python.org/cpython/rev/f7dc02e6987a

New changeset 44841d81bf14 by Antoine Pitrou in branch '2.7':
Issue #19422: Explicitly disallow non-SOCK_STREAM sockets in the ssl module, rather than silently let them emit clear text data.
http://hg.python.org/cpython/rev/44841d81bf14

Updated patch is stricter (it checks for SOCK_STREAM). Pushed!