pop3client.py 文件源码

def _login(self, caps, username, password):
        if self.serverChallenge is not None:
            return self._apop(username, password, self.serverChallenge)

        tryTLS = 'STLS' in caps

        #If our transport supports switching to TLS, we might want to try to switch to TLS.
        tlsableTransport = interfaces.ITLSTransport(self.transport, None) is not None

        # If our transport is not already using TLS, we might want to try to switch to TLS.
        nontlsTransport = interfaces.ISSLTransport(self.transport, None) is None

        if not self.startedTLS and tryTLS and tlsableTransport and nontlsTransport:
            d = self.startTLS()

            d.addCallback(self._loginTLS, username, password)
            return d

        elif self.startedTLS or not nontlsTransport or self.allowInsecureLogin:
            return self._plaintext(username, password)
        else:
            return defer.fail(InsecureAuthenticationDisallowed())