source: TI05-delivery/trunk/lib/python/delivery/server.py @ 1141

"""
Interface to the BBftp server.

@author Stephen Pascoe
"""

import bbftpd

def start(authHandler, args):
    """Start the bbftp server.

    The server performs a fork() during initialisation, the child process remains in
    the server's main loop and the parent returns from this function.  The server process
    calls authHandler.authorise() on each connection to do authentication/authorisation.

    @note: because the server process forks, authHandler will not see any changes to the python
        interpreter following the call to start().

    @param authHandler: an instance of AuthHandler.
    @param args: a list of command line arguments.
    @return: the PID of the server process.
    """
    
    return bbftpd.run(authHandler, args)


class AuthHandler(object):
    """Abstract base class for implementing authentication.

    Subclasses should implement the authorise() method to authenticate clients connecting to
    the server.  An AuthHandler object is passed to start() when initialising the server.
    """
    
    def send(self, buffer):
        """Send a message to the client.

        @param buffer a string containing the message to send.
        """
    
        return bbftpd.send(buffer)

    def recv(self):
        """Receive a message from the client.

        @return a string containing the message received.
        """

        return bbftpd.recv()

    def authorise(self):
        """Authenticate a connection.

        This function should be overridden in subclasses to implement authentication using
        the method calls self.send() and send.recv().

        @note because the server process forks on each connection, calls to authorise() will
            see the state of the python interpreter as it was when start() was called.

        @return an AuthzHandler instance if authentication succeeds, else None.
        """

        raise NotImplementedError


class AuthzHandler(object):
    """Abstract base class for implementing authorisation.

    @ivar username the client's username
    """

    def authzControl(self, msgcode, transferoption, path):
        """Authorise a control command.

        @param msgcode: the command type.
        @param transferoption: extra options specified in the command.
        @param path: the file or directory to which the command applies.
        @return: 0 on success or -1 on failure.
        """

        raise NotImplementedError

    def authzRetr(self, path):
        """Authorise a retrieve request.

        @param path: the file being retrieved.
        @return: 0 on success or -1 on failure.
        """

        raise NotImplementedError

    def authzStore(self, path):
        """Authorise a store request.

        @param path: the destination file.
        @return: 0 on success or -1 on failure.
        """

        raise NotImplementedError
    
    def _raiseNoUsername(self):
        raise ValueError, "No username has been set"
    username = property(_raiseNoUsername)

#--------------------------------------------------------------------------------------------------------------

class BasicClientAuthHandler(AuthHandler):
    """
    When testing with the basic bbftp client some messages will be NULL terminated.  This class
    makes communicating with such clients slightly easier.
    """

    def recvCStr(self):
        """Receive a message from the client which may contain \\0 characters indicating message end.

        The message is truncated to the first \\0 character.

        @return a string containing the message received.
        """

        msg = self.recv()
        # Trim to first '\0'
        x = msg.find('\0')
        if x:
            msg = msg[:x]

        return msg



class LiberalAuthzHandler(AuthzHandler):
    """Allow everything.
    """

    username = None

    def __init__(self, username):
        self.username = username

    def authzControl(self, m, t, p):
        return 0;

    def authzRetr(self, p):
        return 0;

    def authzStore(self, p):
        return 0;