[Twisted-Python] Detect SSL transport and get remote peer certificate in tcp.Server

[exarkun at twistedmatrix.com]

On 10:39 am, adi at roiban.ro wrote:
>Hi,
>
>I work at an experimental FTPS implementation for twisted.protocol.ftp
>
>I use the following code for checking that the transport has TLS
>started and to get the client certificate for certificate based
>authentication:
>
>    @property
>    def is_ftps_command_active(self):
>        '''Return `True` if current command connection is using SSL.'''
>        return isinstance(self.transport.socket, SSL.Connection)

Instead, check `ISSLTransport.providedBy(self.transport)`. 
`ISSLTransport` comes from `twisted.internet.interfaces`.
>    def getPeerCertificate(self):
>        '''Return the peer certificate if remote peer is on a SSL 
>connection
>        and has sent us a certificate.
>        Return `None` otherwise.
>        '''
>        if not hasattr(self.transport, 'socket'):
>            return None
>        if not self.is_ftps_command_active:
>            return None
>        return self.transport.socket.get_peer_certificate()

Heh. :)  Instead, use `transport.getPeerCertificate()`. 
`getPeerCertificate` is a method specified by `ISSLTransport`.

Jean-Paul