munki/code/client/munkilib/gurl.py

#!/usr/bin/python
# encoding: utf-8
#
# Copyright 2009-2016 Greg Neagle.
#
# Licensed under the Apache License, Version 2.0 (the 'License');
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an 'AS IS' BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
gurl.py

Created by Greg Neagle on 2013-11-21.
Modified in Feb 2016 to add support for NSURLSession.

curl replacement using NSURLConnection and friends
"""

import os
import xattr
from urlparse import urlparse

# builtin super doesn't work with Cocoa classes in recent PyObjC releases.
from objc import super

# PyLint cannot properly find names inside Cocoa libraries, so issues bogus
# No name 'Foo' in module 'Bar' warnings. Disable them.
# pylint: disable=E0611


from Foundation import (NSBundle, NSRunLoop, NSDate,
                        NSObject, NSURL, NSURLConnection,
                        NSMutableURLRequest,
                        NSURLRequestReloadIgnoringLocalCacheData,
                        NSURLResponseUnknownLength,
                        NSLog,
                        NSURLCredential, NSURLCredentialPersistenceNone,
                        NSPropertyListSerialization,
                        NSPropertyListMutableContainersAndLeaves,
                        NSPropertyListXMLFormat_v1_0)

try:
    from Foundation import NSURLSession, NSURLSessionConfiguration
    from CFNetwork import (kCFNetworkProxiesHTTPSEnable,
                           kCFNetworkProxiesHTTPEnable)
    NSURLSESSION_AVAILABLE = True
except ImportError:
    NSURLSESSION_AVAILABLE = False

# Disable PyLint complaining about 'invalid' names
# pylint: disable=C0103

if NSURLSESSION_AVAILABLE:
    # NSURLSessionAuthChallengeDisposition enum constants
    NSURLSessionAuthChallengeUseCredential = 0
    NSURLSessionAuthChallengePerformDefaultHandling = 1
    NSURLSessionAuthChallengeCancelAuthenticationChallenge = 2
    NSURLSessionAuthChallengeRejectProtectionSpace = 3

    # NSURLSessionResponseDisposition enum constants
    NSURLSessionResponseCancel = 0
    NSURLSessionResponseAllow = 1
    NSURLSessionResponseBecomeDownload = 2

    # TLS/SSLProtocol enum constants
    kSSLProtocolUnknown = 0
    kSSLProtocol3 = 2
    kTLSProtocol1 = 4
    kTLSProtocol11 = 7
    kTLSProtocol12 = 8
    kDTLSProtocol1 = 9

    # define a helper function for block callbacks
    import ctypes
    import objc
    _objc_so = ctypes.cdll.LoadLibrary(
        os.path.join(objc.__path__[0], '_objc.so'))
    PyObjCMethodSignature_WithMetaData = (
        _objc_so.PyObjCMethodSignature_WithMetaData)
    PyObjCMethodSignature_WithMetaData.restype = ctypes.py_object

    def objc_method_signature(signature_str):
        '''Return a PyObjCMethodSignature given a call signature in string
        format'''
        return PyObjCMethodSignature_WithMetaData(
            ctypes.create_string_buffer(signature_str), None, False)

# pylint: enable=E0611

# disturbing hack warning!
# this works around an issue with App Transport Security on 10.11
bundle = NSBundle.mainBundle()
info = bundle.localizedInfoDictionary() or bundle.infoDictionary()
info['NSAppTransportSecurity'] = {'NSAllowsArbitraryLoads': True}


def NSLogWrapper(message):
    '''A wrapper function for NSLog to prevent format string errors'''
    NSLog('%@', message)


ssl_error_codes = {
    -9800: u'SSL protocol error',
    -9801: u'Cipher Suite negotiation failure',
    -9802: u'Fatal alert',
    -9803: u'I/O would block (not fatal)',
    -9804: u'Attempt to restore an unknown session',
    -9805: u'Connection closed gracefully',
    -9806: u'Connection closed via error',
    -9807: u'Invalid certificate chain',
    -9808: u'Bad certificate format',
    -9809: u'Underlying cryptographic error',
    -9810: u'Internal error',
    -9811: u'Module attach failure',
    -9812: u'Valid cert chain, untrusted root',
    -9813: u'Cert chain not verified by root',
    -9814: u'Chain had an expired cert',
    -9815: u'Chain had a cert not yet valid',
    -9816: u'Server closed session with no notification',
    -9817: u'Insufficient buffer provided',
    -9818: u'Bad SSLCipherSuite',
    -9819: u'Unexpected message received',
    -9820: u'Bad MAC',
    -9821: u'Decryption failed',
    -9822: u'Record overflow',
    -9823: u'Decompression failure',
    -9824: u'Handshake failure',
    -9825: u'Misc. bad certificate',
    -9826: u'Bad unsupported cert format',
    -9827: u'Certificate revoked',
    -9828: u'Certificate expired',
    -9829: u'Unknown certificate',
    -9830: u'Illegal parameter',
    -9831: u'Unknown Cert Authority',
    -9832: u'Access denied',
    -9833: u'Decoding error',
    -9834: u'Decryption error',
    -9835: u'Export restriction',
    -9836: u'Bad protocol version',
    -9837: u'Insufficient security',
    -9838: u'Internal error',
    -9839: u'User canceled',
    -9840: u'No renegotiation allowed',
    -9841: u'Peer cert is valid, or was ignored if verification disabled',
    -9842: u'Server has requested a client cert',
    -9843: u'Peer host name mismatch',
    -9844: u'Peer dropped connection before responding',
    -9845: u'Decryption failure',
    -9846: u'Bad MAC',
    -9847: u'Record overflow',
    -9848: u'Configuration error',
    -9849: u'Unexpected (skipped) record in DTLS'}


class Gurl(NSObject):
    '''A class for getting content from a URL
       using NSURLConnection/NSURLSession and friends'''

    # since we inherit from NSObject, PyLint issues a few bogus warnings
    # pylint: disable=W0232,E1002

    # Don't want to define the attributes twice that are initialized in
    # initWithOptions_(), so:
    # pylint: disable=E1101,W0201

    GURL_XATTR = 'com.googlecode.munki.downloadData'

    def initWithOptions_(self, options):
        '''Set up our Gurl object'''
        self = super(Gurl, self).init()
        if not self:
            return

        self.follow_redirects = options.get('follow_redirects', False)
        self.ignore_system_proxy = options.get('ignore_system_proxy', False)
        self.destination_path = options.get('file')
        self.can_resume = options.get('can_resume', False)
        self.url = options.get('url')
        self.additional_headers = options.get('additional_headers', {})
        self.username = options.get('username')
        self.password = options.get('password')
        self.download_only_if_changed = options.get(
            'download_only_if_changed', False)
        self.cache_data = options.get('cache_data')
        self.connection_timeout = options.get('connection_timeout', 60)
        if NSURLSESSION_AVAILABLE:
            self.minimum_tls_protocol = options.get(
                'minimum_tls_protocol', kTLSProtocol1)

        self.log = options.get('logging_function', NSLogWrapper)

        self.resume = False
        self.response = None
        self.headers = None
        self.status = None
        self.error = None
        self.SSLerror = None
        self.done = False
        self.redirection = []
        self.destination = None
        self.bytesReceived = 0
        self.expectedLength = -1
        self.percentComplete = 0
        self.connection = None
        self.session = None
        self.task = None
        return self

    def start(self):
        '''Start the connection'''
        if not self.destination_path:
            self.log('No output file specified.')
            self.done = True
            return
        url = NSURL.URLWithString_(self.url)
        request = (
            NSMutableURLRequest.requestWithURL_cachePolicy_timeoutInterval_(
                url, NSURLRequestReloadIgnoringLocalCacheData,
                self.connection_timeout))
        if self.additional_headers:
            for header, value in self.additional_headers.items():
                request.setValue_forHTTPHeaderField_(value, header)
        # does the file already exist? See if we can resume a partial download
        if os.path.isfile(self.destination_path):
            stored_data = self.get_stored_headers()
            if (self.can_resume and 'expected-length' in stored_data and
                    ('last-modified' in stored_data or 'etag' in stored_data)):
                # we have a partial file and we're allowed to resume
                self.resume = True
                local_filesize = os.path.getsize(self.destination_path)
                byte_range = 'bytes=%s-' % local_filesize
                request.setValue_forHTTPHeaderField_(byte_range, 'Range')
        if self.download_only_if_changed and not self.resume:
            stored_data = self.cache_data or self.get_stored_headers()
            if 'last-modified' in stored_data:
                request.setValue_forHTTPHeaderField_(
                    stored_data['last-modified'], 'if-modified-since')
            if 'etag' in stored_data:
                request.setValue_forHTTPHeaderField_(
                    stored_data['etag'], 'if-none-match')
        if NSURLSESSION_AVAILABLE:
            configuration = \
                NSURLSessionConfiguration.defaultSessionConfiguration()

            # optional: ignore system http/https proxies (10.9+ only)
            if self.ignore_system_proxy is True:
                configuration.setConnectionProxyDictionary_(
                    {kCFNetworkProxiesHTTPEnable: False,
                     kCFNetworkProxiesHTTPSEnable: False})

            # set minumum supported TLS protocol (defaults to TLS1)
            configuration.setTLSMinimumSupportedProtocol_(
                self.minimum_tls_protocol)

            self.session = \
                NSURLSession.sessionWithConfiguration_delegate_delegateQueue_(
                    configuration, self, None)
            self.task = self.session.dataTaskWithRequest_(request)
            self.task.resume()
        else:
            self.connection = NSURLConnection.alloc().initWithRequest_delegate_(
                request, self)

    def cancel(self):
        '''Cancel the connection'''
        if self.connection:
            if NSURLSESSION_AVAILABLE:
                self.session.invalidateAndCancel()
            else:
                self.connection.cancel()
            self.done = True

    def isDone(self):
        '''Check if the connection request is complete. As a side effect,
        allow the delegates to work by letting the run loop run for a bit'''
        if self.done:
            return self.done
        # let the delegates do their thing
        NSRunLoop.currentRunLoop().runUntilDate_(
            NSDate.dateWithTimeIntervalSinceNow_(.1))
        return self.done

    def get_stored_headers(self):
        '''Returns any stored headers for self.destination_path'''
        # try to read stored headers
        try:
            stored_plist_str = xattr.getxattr(
                self.destination_path, self.GURL_XATTR)
        except (KeyError, IOError):
            return {}
        data = buffer(stored_plist_str)
        dataObject, plistFormat, error = (
            NSPropertyListSerialization.
            propertyListFromData_mutabilityOption_format_errorDescription_(
                data, NSPropertyListMutableContainersAndLeaves, None, None))
        if error:
            return {}
        else:
            return dataObject

    def store_headers(self, headers):
        '''Store dictionary data as an xattr for self.destination_path'''
        plistData, error = (
            NSPropertyListSerialization.
            dataFromPropertyList_format_errorDescription_(
                headers, NSPropertyListXMLFormat_v1_0, None))
        if error:
            string = ''
        else:
            string = str(plistData)
        try:
            xattr.setxattr(self.destination_path, self.GURL_XATTR, string)
        except IOError, err:
            self.log('Could not store metadata to %s: %s'
                     % (self.destination_path, err))

    def normalize_header_dict(self, a_dict):
        '''Since HTTP header names are not case-sensitive, we normalize a
        dictionary of HTTP headers by converting all the key names to
        lower case'''

        # yes, we don't use 'self'!
        # pylint: disable=R0201

        new_dict = {}
        for key, value in a_dict.items():
            new_dict[key.lower()] = value
        return new_dict

    def recordError_(self, error):
        '''Record any error info from completed connection/session'''
        self.error = error
        # If this was an SSL error, try to extract the SSL error code.
        if 'NSUnderlyingError' in error.userInfo():
            ssl_code = error.userInfo()['NSUnderlyingError'].userInfo().get(
                '_kCFNetworkCFStreamSSLErrorOriginalValue', None)
            if ssl_code:
                self.SSLerror = (ssl_code, ssl_error_codes.get(
                    ssl_code, 'Unknown SSL error'))

    def removeExpectedSizeFromStoredHeaders(self):
        '''If a successful transfer, clear the expected size so we
        don\'t attempt to resume the download next time'''
        if str(self.status).startswith('2'):
            # remove the expected-size from the stored headers
            headers = self.get_stored_headers()
            if 'expected-length' in headers:
                del headers['expected-length']
                self.store_headers(headers)

    def URLSession_task_didCompleteWithError_(self, session, task, error):
        '''NSURLSessionTaskDelegate method.'''
        # we don't actually use the session or task arguments, so
        # pylint: disable=W0613
        if self.destination and self.destination_path:
            self.destination.close()
            self.removeExpectedSizeFromStoredHeaders()
        if error:
            self.recordError_(error)
        self.done = True

    def connection_didFailWithError_(self, connection, error):
        '''NSURLConnectionDelegate method
        Sent when a connection fails to load its request successfully.'''
        # we don't actually use the connection argument, so
        # pylint: disable=W0613
        self.recordError_(error)
        self.done = True
        if self.destination and self.destination_path:
            self.destination.close()

    def connectionDidFinishLoading_(self, connection):
        '''NSURLConnectionDataDelegate method
        Sent when a connection has finished loading successfully.'''

        # we don't actually use the connection argument, so
        # pylint: disable=W0613

        self.done = True
        if self.destination and self.destination_path:
            self.destination.close()
            self.removeExpectedSizeFromStoredHeaders()

    def handleResponse_withCompletionHandler_(
            self, response, completionHandler):
        '''Handle the response to the connection'''
        self.response = response
        self.bytesReceived = 0
        self.percentComplete = -1
        self.expectedLength = response.expectedContentLength()

        download_data = {}
        if response.className() == u'NSHTTPURLResponse':
            # Headers and status code only available for HTTP/S transfers
            self.status = response.statusCode()
            self.headers = dict(response.allHeaderFields())
            normalized_headers = self.normalize_header_dict(self.headers)
            if 'last-modified' in normalized_headers:
                download_data['last-modified'] = normalized_headers[
                    'last-modified']
            if 'etag' in normalized_headers:
                download_data['etag'] = normalized_headers['etag']
            download_data['expected-length'] = self.expectedLength

        # self.destination is defined in initWithOptions_
        # pylint: disable=E0203

        if not self.destination and self.destination_path:
            if self.status == 206 and self.resume:
                # 206 is Partial Content response
                stored_data = self.get_stored_headers()
                if (not stored_data or
                        stored_data.get('etag') != download_data.get('etag') or
                        stored_data.get('last-modified') != download_data.get(
                            'last-modified')):
                    # file on server is different than the one
                    # we have a partial for
                    self.log(
                        'Can\'t resume download; file on server has changed.')
                    if completionHandler:
                        # tell the session task to cancel
                        completionHandler(NSURLSessionResponseCancel)
                    else:
                        # cancel the connection
                        self.connection.cancel()
                    self.log('Removing %s' % self.destination_path)
                    os.unlink(self.destination_path)
                    # restart and attempt to download the entire file
                    self.log(
                        'Restarting download of %s' % self.destination_path)
                    os.unlink(self.destination_path)
                    self.start()
                    return
                # try to resume
                self.log('Resuming download for %s' % self.destination_path)
                # add existing file size to bytesReceived so far
                local_filesize = os.path.getsize(self.destination_path)
                self.bytesReceived = local_filesize
                self.expectedLength += local_filesize
                # open file for append
                self.destination = open(self.destination_path, 'a')

            elif str(self.status).startswith('2'):
                # not resuming, just open the file for writing
                self.destination = open(self.destination_path, 'w')
                # store some headers with the file for use if we need to resume
                # the downloadand for future checking if the file on the server
                # has changed
                self.store_headers(download_data)
        if completionHandler:
            # tell the session task to continue
            completionHandler(NSURLSessionResponseAllow)

    def URLSession_dataTask_didReceiveResponse_completionHandler_(
            self, session, task, response, completionHandler):
        '''NSURLSessionDataDelegate method'''
        # we don't actually use the session or task arguments, so
        # pylint: disable=W0613
        completionHandler.__block_signature__ = objc_method_signature('v@i')
        self.handleResponse_withCompletionHandler_(response, completionHandler)

    def connection_didReceiveResponse_(self, connection, response):
        '''NSURLConnectionDataDelegate delegate method
        Sent when the connection has received sufficient data to construct the
        URL response for its request.'''
        # we don't actually use the connection argument, so
        # pylint: disable=W0613
        self.handleResponse_withCompletionHandler_(response, None)

    def handleRedirect_newRequest_withCompletionHandler_(
            self, response, request, completionHandler):
        '''Handle the redirect request'''
        if response is None:
            # the request has changed the NSURLRequest in order to standardize
            # its format, for example, changing a request for
            # http://www.apple.com to http://www.apple.com/. This occurs because
            # the standardized, or canonical, version of the request is used for
            # cache management. Pass the request back as-is
            # (it appears that at some point Apple also defined a redirect like
            # http://developer.apple.com to https://developer.apple.com to be
            # 'merely' a change in the canonical URL.)
            # Further -- it appears that this delegate method isn't called at
            # all in this scenario, unlike NSConnectionDelegate method
            # connection:willSendRequest:redirectResponse:
            # we'll leave this here anyway in case we're wrong about that
            if completionHandler:
                completionHandler(request)
                return
            else:
                return request
        # If we get here, it appears to be a real redirect attempt
        # Annoyingly, we apparently can't get access to the headers from the
        # site that told us to redirect. All we know is that we were told
        # to redirect and where the new location is.
        newURL = request.URL().absoluteString()
        self.redirection.append([newURL, dict(response.allHeaderFields())])
        newParsedURL = urlparse(newURL)
        # This code was largely based on the work of Andreas Fuchs
        # (https://github.com/munki/munki/pull/465)
        if self.follow_redirects is True or self.follow_redirects == 'all':
            # Allow the redirect
            self.log('Allowing redirect to: %s' % newURL)
            if completionHandler:
                completionHandler(request)
                return
            else:
                return request
        elif (self.follow_redirects == 'https'
              and newParsedURL.scheme == 'https'):
            # Once again, allow the redirect
            self.log('Allowing redirect to: %s' % newURL)
            if completionHandler:
                completionHandler(request)
                return
            else:
                return request
        else:
            # If we're down here either the preference was set to 'none',
            # the url we're forwarding on to isn't https or follow_redirects
            # was explicitly set to False
            self.log('Denying redirect to: %s' % newURL)
            if completionHandler:
                completionHandler(None)
                return
            else:
                return None

    def URLSession_task_willPerformHTTPRedirection_newRequest_completionHandler_(
            self, session, task, response, request, completionHandler):
        '''NSURLSessionTaskDelegate method'''
        # we don't actually use the session or task arguments, so
        # pylint: disable=W0613
        self.log(
            'URLSession_task_willPerformHTTPRedirection_newRequest_'
            'completionHandler_')
        completionHandler.__block_signature__ = objc_method_signature('v@@')
        self.handleRedirect_newRequest_withCompletionHandler_(
            response, request, completionHandler)

    def connection_willSendRequest_redirectResponse_(
            self, connection, request, response):
        '''NSURLConnectionDataDelegate method
        Sent when the connection determines that it must change URLs in order to
        continue loading a request.'''

        # we don't actually use the connection argument, so
        # pylint: disable=W0613
        self.log('connection_willSendRequest_redirectResponse_')
        return self.handleRedirect_newRequest_withCompletionHandler_(
            response, request, None)

    def connection_canAuthenticateAgainstProtectionSpace_(
            self, connection, protectionSpace):
        '''NSURLConnection delegate method
        Sent to determine whether the delegate is able to respond to a
        protection space’s form of authentication.
        Deprecated in 10.10'''

        # we don't actually use the connection argument, so
        # pylint: disable=W0613

        # this is not called in 10.5.x.
        self.log('connection_canAuthenticateAgainstProtectionSpace_')
        if protectionSpace:
            host = protectionSpace.host()
            realm = protectionSpace.realm()
            authenticationMethod = protectionSpace.authenticationMethod()
            self.log('Protection space found. Host: %s Realm: %s AuthMethod: %s'
                     % (host, realm, authenticationMethod))
            if self.username and self.password and authenticationMethod in [
                    'NSURLAuthenticationMethodDefault',
                    'NSURLAuthenticationMethodHTTPBasic',
                    'NSURLAuthenticationMethodHTTPDigest']:
                # we know how to handle this
                self.log('Can handle this authentication request')
                return True
        # we don't know how to handle this; let the OS try
        self.log('Allowing OS to handle authentication request')
        return False

    def handleChallenge_withCompletionHandler_(
            self, challenge, completionHandler):
        '''Handle an authentication challenge'''
        protectionSpace = challenge.protectionSpace()
        host = protectionSpace.host()
        realm = protectionSpace.realm()
        authenticationMethod = protectionSpace.authenticationMethod()
        self.log(
            'Authentication challenge for Host: %s Realm: %s AuthMethod: %s'
            % (host, realm, authenticationMethod))
        if challenge.previousFailureCount() > 0:
            # we have the wrong credentials. just fail
            self.log('Previous authentication attempt failed.')
            if completionHandler:
                completionHandler(
                    NSURLSessionAuthChallengeCancelAuthenticationChallenge,
                    None)
            else:
                challenge.sender().cancelAuthenticationChallenge_(challenge)
        if self.username and self.password and authenticationMethod in [
                'NSURLAuthenticationMethodDefault',
                'NSURLAuthenticationMethodHTTPBasic',
                'NSURLAuthenticationMethodHTTPDigest']:
            self.log('Will attempt to authenticate.')
            self.log('Username: %s Password: %s'
                     % (self.username, ('*' * len(self.password or ''))))
            credential = (
                NSURLCredential.credentialWithUser_password_persistence_(
                    self.username, self.password,
                    NSURLCredentialPersistenceNone))
            if completionHandler:
                completionHandler(
                    NSURLSessionAuthChallengeUseCredential, credential)
            else:
                challenge.sender().useCredential_forAuthenticationChallenge_(
                    credential, challenge)
        else:
            # fall back to system-provided default behavior
            self.log('Allowing OS to handle authentication request')
            if completionHandler:
                completionHandler(
                    NSURLSessionAuthChallengePerformDefaultHandling, None)
            else:
                if (challenge.sender().respondsToSelector_(
                        'performDefaultHandlingForAuthenticationChallenge:')):
                    self.log('Allowing OS to handle authentication request')
                    challenge.sender(
                        ).performDefaultHandlingForAuthenticationChallenge_(
                            challenge)
                else:
                    # Mac OS X 10.6 doesn't support
                    # performDefaultHandlingForAuthenticationChallenge:
                    self.log('Continuing without credential.')
                    challenge.sender(
                        ).continueWithoutCredentialForAuthenticationChallenge_(
                            challenge)

    def connection_willSendRequestForAuthenticationChallenge_(
            self, connection, challenge):
        '''NSURLConnection delegate method
        Tells the delegate that the connection will send a request for an
        authentication challenge. New in 10.7.'''
        # we don't actually use the connection argument, so
        # pylint: disable=W0613
        self.log('connection_willSendRequestForAuthenticationChallenge_')
        self.handleChallenge_withCompletionHandler_(challenge, None)

    def URLSession_task_didReceiveChallenge_completionHandler_(
            self, session, task, challenge, completionHandler):
        '''NSURLSessionTaskDelegate method'''
        # we don't actually use the session or task arguments, so
        # pylint: disable=W0613
        completionHandler.__block_signature__ = objc_method_signature('v@i@')
        self.log('URLSession_task_didReceiveChallenge_completionHandler_')
        self.handleChallenge_withCompletionHandler_(
            challenge, completionHandler)

    def connection_didReceiveAuthenticationChallenge_(
            self, connection, challenge):
        '''NSURLConnection delegate method
        Sent when a connection must authenticate a challenge in order to
        download its request. Deprecated in 10.10'''
        # we don't actually use the connection argument, so
        # pylint: disable=W0613
        self.log('connection_didReceiveAuthenticationChallenge_')
        self.handleChallenge_withCompletionHandler_(challenge, None)

    def handleReceivedData_(self, data):
        '''Handle received data'''
        if self.destination:
            self.destination.write(str(data))
        else:
            self.log(str(data).decode('UTF-8'))
        self.bytesReceived += len(data)
        if self.expectedLength != NSURLResponseUnknownLength:
            self.percentComplete = int(
                float(self.bytesReceived)/float(self.expectedLength) * 100.0)

    def URLSession_dataTask_didReceiveData_(self, session, task, data):
        '''NSURLSessionDataDelegate method'''
        # we don't actually use the session or task arguments, so
        # pylint: disable=W0613
        self.handleReceivedData_(data)

    def connection_didReceiveData_(self, connection, data):
        '''NSURLConnectionDataDelegate method
        Sent as a connection loads data incrementally'''
        # we don't actually use the connection argument, so
        # pylint: disable=W0613
        self.handleReceivedData_(data)