WebBrowser/SafeBrowsing/SafeBrowsingManager.py

# -*- coding: utf-8 -*-

# Copyright (c) 2017 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing the interface for Google Safe Browsing.
"""

#
# Some part of this code were ported from gglsbl.client and adapted
# to Qt.
#
# https://github.com/afilipovich/gglsbl
#

from __future__ import unicode_literals

import os
import base64

from PyQt5.QtCore import QObject

import Preferences
import Utilities

from .SafeBrowsingAPIClient import SafeBrowsingAPIClient
from .SafeBrowsingCache import SafeBrowsingCache, ThreatList, HashPrefixList


class SafeBrowsingManager(QObject):
    """
    Class implementing the interface for Google Safe Browsing.
    """
    def __init__(self):
        """
        Constructor
        """
        super(SafeBrowsingManager, self).__init__()
        
        self.__apiKey = Preferences.getWebBrowser("SafeBrowsingApiKey")
        if self.__apiKey:
##            self.__apiClient = SafeBrowsingAPIClient(self.__apiKey,
##                                                     parent=self)
            # TODO: switch these after debugging is finished
            self.__apiClient = SafeBrowsingAPIClient(self.__apiKey,
                                                     parent=self,
                                                     fairUse=False)
        else:
            self.__apiClient = None
        
        self.__enabled = (
            Preferences.getWebBrowser("SafeBrowsingEnabled") and
            bool(self.__apiKey))
        
        gsbCachePath = os.path.join(
            Utilities.getConfigDir(), "web_browser", "safe_browsing")
        self.__cache = SafeBrowsingCache(gsbCachePath, self)
        
        self.__gsbDialog = None
        self.__platforms = None     # TODO: delete if not needed
    
    def configurationChanged(self):
        """
        Public method to handle changes of the settings.
        """
        apiKey = Preferences.getWebBrowser("SafeBrowsingApiKey")
        if apiKey != self.__apiKey:
            self.__apiKey = apiKey
            if self.__apiKey:
                if self.__apiClient:
                    self.__apiClient.setApiKey(self.__apiKey)
                else:
##                    self.__apiClient = SafeBrowsingAPIClient(self.__apiKey,
##                                                             parent=self)
                    # TODO: switch these after debugging is finished
                    self.__apiClient = SafeBrowsingAPIClient(self.__apiKey,
                                                             parent=self,
                                                             fairUse=False)
        
        self.__enabled = (
            Preferences.getWebBrowser("SafeBrowsingEnabled") and
            bool(self.__apiKey))
    
    def isEnabled(self):
        """
        Public method to check, if safe browsing is enabled.
        
        @return flag indicating the enabled state
        @rtype bool
        """
        return self.__enabled
    
    def close(self):
        """
        Public method to close the safe browsing interface.
        """
        self.__cache.close()
    
    def fairUseDelayExpired(self):
        """
        Public method to check, if the fair use wait period has expired.
        
        @return flag indicating expiration
        @rtype bool
        """
        return self.__enabled and self.__apiClient.fairUseDelayExpired()
    
    def updateHashPrefixCache(self):
        """
        Public method to load or update the locally cached threat lists.
        
        @return flag indicating success and an error message
        @rtype tuple of (bool, str)
        """
        if not self.__enabled:
            return False, self.tr("Safe Browsing is disabled.")
        
        if not self.__apiClient.fairUseDelayExpired():
            return False, \
                self.tr("The fair use wait period has not expired yet.")
        
        # step 1: remove expired hashes
        self.__cache.cleanupFullHashes()
        
        # step 2: update threat lists
        threatListsForRemove = {}
        for threatList, clientState in self.__cache.getThreatLists():
            threatListsForRemove[repr(threatList)] = threatList
        threatLists = self.__apiClient.getThreatLists()
        for entry in threatLists:
            threatList = ThreatList.fromApiEntry(entry)
            if self.__platforms is None or \
                    threatList.platformType in self.__platforms:
                self.__cache.addThreatList(threatList)
                key = repr(threatList)
                if key in threatListsForRemove:
                    del threatListsForRemove[key]
        for threatList in threatListsForRemove.values():
            self.__cache.deleteHashPrefixList(threatList)
            self.__cache.deleteThreatList(threatList)
        del threatListsForRemove
        
        # step 3: update threats
        threatLists = self.__cache.getThreatLists()
        clientStates = {}
        for threatList, clientState in threatLists:
            clientStates[threatList.asTuple()] = clientState
        threatsUpdateResponses = \
            self.__apiClient.getThreatsUpdate(clientStates)
        for response in threatsUpdateResponses:
            responseThreatList = ThreatList.fromApiEntry(response)
            if response["responseType"] == "FULL_UPDATE":
                self.__cache.deleteHashPrefixList(responseThreatList)
            for removal in response.get("removals", []):
                self.__cache.removeHashPrefixIndices(
                    responseThreatList, removal["rawIndices"]["indices"])
            for addition in response.get("additions", []):
                hashPrefixList = HashPrefixList(
                    addition["rawHashes"]["prefixSize"],
                    base64.b64decode(addition["rawHashes"]["rawHashes"]))
                self.__cache.populateHashPrefixList(responseThreatList,
                                                    hashPrefixList)
            expectedChecksum = base64.b64decode(response["checksum"]["sha256"])
            if self.__verifyThreatListChecksum(responseThreatList,
                                               expectedChecksum):
                self.__cache.updateThreatListClientState(
                    responseThreatList, response["newClientState"])
            else:
                return False, \
                    self.tr("Local cache checksum does not match the server."
                            " Consider cleaning the cache. Threat update has"
                            " been aborted.")
        
        return True, ""
    
    def __verifyThreatListChecksum(self, threatList, remoteChecksum):
        """
        Private method to verify the local checksum of a threat list with the
        checksum of the safe browsing server.
        """
        localChecksum = self.__cache.hashPrefixListChecksum(threatList)
        return remoteChecksum == localChecksum
    
    def fullCacheCleanup(self):
        """
        Public method to clean up the cache completely.
        """
        self.__cache.prepareCacheDb()
    
    def showSafeBrowsingDialog(self):
        """
        Public slot to show the safe browsing management dialog.
        """
        if self.__gsbDialog is None:
            from WebBrowser.WebBrowserWindow import WebBrowserWindow
            from .SafeBrowsingDialog import SafeBrowsingDialog
            self.__gsbDialog = SafeBrowsingDialog(
                self, parent=WebBrowserWindow.mainWindow())
        
        self.__gsbDialog.show()