[Python-Dev] More on server-side SSL support

[Bill Janssen]

> I view TLS as a wrapper around / layer on top of TCP, and so I think the
> API should look like, as well.

I think Martin raises a valid point here, which should at least be
discussed more thoroughly.  Should there be an "SSL socket", which is
just like a regular socket?  Does that really provide any additional
functionality to anyone?  Most apps and classes that use TCP sockets
wrap the socket with socket._fileobject() to get "read" and "write",
anyway -- can't they just wrap it with socket.ssl instead?

Perhaps in the sprint, I should just concentrate on widening the
"socket.ssl" interface a bit, and improving the functionality of the
SSLObject a bit.

Suggested improvements:

  *  Allow server-side operation.

  *  Allow specification of particular SSL protocol version.

  *  Allow certificate validation.  This is a bit tricky; typically
     certs are validated against some database of root certificates, so you
     need a whole infrastructure to maintain that database.  Currently, we
     don't have one, so no certs can be validated.  We could add a switch
     to allow auto-validation of self-signed certs pretty easily.  I could
     add a parameter to the SSLObject constructor which would be a filepath
     for a file full of root certs (see SSL_CTX_load_verify_locations(3ssl)).

  *  Add a method to retrieve the other side's certificate info.  What's
     a good format for the "notBefore" and "notAfter" dates?  The simplest
     thing to use is the string formatting OpenSSL provides, which is
     always like "Sep 29 16:38:04 2006 GMT", which can easily be parsed
     by the time.strptime() function if the user wants something else.
     On the other hand, figuring out how to use strptime() is always a
     pain, so providing a convenience function wouldn't be a terrible idea.

  *  Add a shutdown() method to stop using SSL on the underlying socket
     without closing the socket.

  *  Make SSLObject conform to the Raw I/O API in PEP 3116.  This one is
     interesting; what should close() do?  Close the underlying socket?  Or
     just do an SSL shutdown?

Bill