"""

A helper class for using TLS Lite with stdlib clients

(httplib, xmlrpclib, imaplib, poplib).

"""



from gdata.tlslite.Checker import Checker



class ClientHelper:

    """This is a helper class used to integrate TLS Lite with various

    TLS clients (e.g. poplib, smtplib, httplib, etc.)"""



    def __init__(self,

              username=None, password=None, sharedKey=None,

              certChain=None, privateKey=None,

              cryptoID=None, protocol=None,

              x509Fingerprint=None,

              x509TrustList=None, x509CommonName=None,

              settings = None):

        """

        For client authentication, use one of these argument

        combinations:

         - username, password (SRP)

         - username, sharedKey (shared-key)

         - certChain, privateKey (certificate)



        For server authentication, you can either rely on the

        implicit mutual authentication performed by SRP or

        shared-keys, or you can do certificate-based server

        authentication with one of these argument combinations:

         - cryptoID[, protocol] (requires cryptoIDlib)

         - x509Fingerprint

         - x509TrustList[, x509CommonName] (requires cryptlib_py)



        Certificate-based server authentication is compatible with

        SRP or certificate-based client authentication.  It is

        not compatible with shared-keys.



        The constructor does not perform the TLS handshake itself, but

        simply stores these arguments for later.  The handshake is

        performed only when this class needs to connect with the

        server.  Then you should be prepared to handle TLS-specific

        exceptions.  See the client handshake functions in

        L{tlslite.TLSConnection.TLSConnection} for details on which

        exceptions might be raised.



        @type username: str

        @param username: SRP or shared-key username.  Requires the

        'password' or 'sharedKey' argument.



        @type password: str

        @param password: SRP password for mutual authentication.

        Requires the 'username' argument.



        @type sharedKey: str

        @param sharedKey: Shared key for mutual authentication.

        Requires the 'username' argument.



        @type certChain: L{tlslite.X509CertChain.X509CertChain} or

        L{cryptoIDlib.CertChain.CertChain}

        @param certChain: Certificate chain for client authentication.

        Requires the 'privateKey' argument.  Excludes the SRP or

        shared-key related arguments.



        @type privateKey: L{tlslite.utils.RSAKey.RSAKey}

        @param privateKey: Private key for client authentication.

        Requires the 'certChain' argument.  Excludes the SRP or

        shared-key related arguments.



        @type cryptoID: str

        @param cryptoID: cryptoID for server authentication.  Mutually

        exclusive with the 'x509...' arguments.



        @type protocol: str

        @param protocol: cryptoID protocol URI for server

        authentication.  Requires the 'cryptoID' argument.



        @type x509Fingerprint: str

        @param x509Fingerprint: Hex-encoded X.509 fingerprint for

        server authentication.  Mutually exclusive with the 'cryptoID'

        and 'x509TrustList' arguments.



        @type x509TrustList: list of L{tlslite.X509.X509}

        @param x509TrustList: A list of trusted root certificates.  The

        other party must present a certificate chain which extends to

        one of these root certificates.  The cryptlib_py module must be

        installed to use this parameter.  Mutually exclusive with the

        'cryptoID' and 'x509Fingerprint' arguments.



        @type x509CommonName: str

        @param x509CommonName: The end-entity certificate's 'CN' field

        must match this value.  For a web server, this is typically a

        server name such as 'www.amazon.com'.  Mutually exclusive with

        the 'cryptoID' and 'x509Fingerprint' arguments.  Requires the

        'x509TrustList' argument.



        @type settings: L{tlslite.HandshakeSettings.HandshakeSettings}

        @param settings: Various settings which can be used to control

        the ciphersuites, certificate types, and SSL/TLS versions

        offered by the client.

        """



        self.username = None

        self.password = None

        self.sharedKey = None

        self.certChain = None

        self.privateKey = None

        self.checker = None



        #SRP Authentication

        if username and password and not \

                (sharedKey or certChain or privateKey):

            self.username = username

            self.password = password



        #Shared Key Authentication

        elif username and sharedKey and not \

                (password or certChain or privateKey):

            self.username = username

            self.sharedKey = sharedKey



        #Certificate Chain Authentication

        elif certChain and privateKey and not \

                (username or password or sharedKey):

            self.certChain = certChain

            self.privateKey = privateKey



        #No Authentication

        elif not password and not username and not \

                sharedKey and not certChain and not privateKey:

            pass



        else:

            raise ValueError("Bad parameters")



        #Authenticate the server based on its cryptoID or fingerprint

        if sharedKey and (cryptoID or protocol or x509Fingerprint):

            raise ValueError("Can't use shared keys with other forms of"\

                             "authentication")



        self.checker = Checker(cryptoID, protocol, x509Fingerprint,

                               x509TrustList, x509CommonName)

        self.settings = settings



        self.tlsSession = None



    def _handshake(self, tlsConnection):

        if self.username and self.password:

            tlsConnection.handshakeClientSRP(username=self.username,

                                             password=self.password,

                                             checker=self.checker,

                                             settings=self.settings,

                                             session=self.tlsSession)

        elif self.username and self.sharedKey:

            tlsConnection.handshakeClientSharedKey(username=self.username,

                                                   sharedKey=self.sharedKey,

                                                   settings=self.settings)

        else:

            tlsConnection.handshakeClientCert(certChain=self.certChain,

                                              privateKey=self.privateKey,

                                              checker=self.checker,

                                              settings=self.settings,

                                              session=self.tlsSession)

        self.tlsSession = tlsConnection.session