The Tor Browser: toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js@925c144e1f1f (annotated)

toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js@925c144e1f1f (annotated)

toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;
 const Cu = Components.utils;
 // COMPLETE_LENGTH and PARTIAL_LENGTH copied from nsUrlClassifierDBService.h,
 // they correspond to the length, in bytes, of a hash prefix and the total
 // hash.
 const COMPLETE_LENGTH = 32;
 const PARTIAL_LENGTH = 4;
 // These backoff related constants are taken from v2 of the Google Safe Browsing
 // API.
 // BACKOFF_ERRORS: the number of errors incurred until we start to back off.
 // BACKOFF_INTERVAL: the initial time, in seconds, to wait once we start backing
 //                   off.
 // BACKOFF_MAX: as the backoff time doubles after each failure, this is a
 //              ceiling on the time to wait, in seconds.
 // BACKOFF_TIME: length of the interval of time, in seconds, during which errors
 //               are taken into account.
 const BACKOFF_ERRORS = 2;
 const BACKOFF_INTERVAL = 30 * 60;
 const BACKOFF_MAX = 8 * 60 * 60;
 const BACKOFF_TIME = 5 * 60;
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 function HashCompleter() {
   // This is a HashCompleterRequest and is used by multiple calls to |complete|
   // in succession to avoid unnecessarily creating requests. Once it has been
   // started, this is set to null again.
   this._currentRequest = null;
   // Whether we have been informed of a shutdown by the xpcom-shutdown event.
   this._shuttingDown = false;
   // All of these backoff properties are different per completer as the DB
   // service keeps one completer per table.
   //
   // _backoff tells us whether we are "backing off" from making requests.
   // It is set in |noteServerResponse| and set after a number of failures.
   this._backoff = false;
   // _backoffTime tells us how long we should wait (in seconds) before making
   // another request.
   this._backoffTime = 0;
   // _nextRequestTime is the earliest time at which we are allowed to make
   // another request by the backoff policy. It is measured in milliseconds.
   this._nextRequestTime = 0;
   // A list of the times at which a failed request was made, recorded in
   // |noteServerResponse|. Sorted by oldest to newest and its length is clamped
   // by BACKOFF_ERRORS.
   this._errorTimes = [];
   Services.obs.addObserver(this, "xpcom-shutdown", true);
 }
 HashCompleter.prototype = {
   classID: Components.ID("{9111de73-9322-4bfc-8b65-2b727f3e6ec8}"),
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIUrlClassifierHashCompleter,
                                          Ci.nsIRunnable,
                                          Ci.nsIObserver,
                                          Ci.nsISupportsWeakReference,
                                          Ci.nsISupports]),
   // This is mainly how the HashCompleter interacts with other components.
   // Even though it only takes one partial hash and callback, subsequent
   // calls are made into the same HTTP request by using a thread dispatch.
   complete: function HC_complete(aPartialHash, aCallback) {
     if (!this._currentRequest) {
       this._currentRequest = new HashCompleterRequest(this);
       // It's possible for getHashUrl to not be set, usually at start-up.
       if (this._getHashUrl) {
         Services.tm.currentThread.dispatch(this, Ci.nsIThread.DISPATCH_NORMAL);
       }
     }
     this._currentRequest.add(aPartialHash, aCallback);
   },
   // This is called when either the getHashUrl has been set or after a few calls
   // to |complete|. It starts off the HTTP request by making a |begin| call
   // to the HashCompleterRequest.
   run: function HC_run() {
     if (this._shuttingDown) {
       this._currentRequest = null;
       throw Cr.NS_ERROR_NOT_INITIALIZED;
     }
     if (!this._currentRequest) {
       return;
     }
     if (!this._getHashUrl) {
       throw Cr.NS_ERROR_NOT_INITIALIZED;
     }
     let url = this._getHashUrl;
     let uri = Services.io.newURI(url, null, null);
     this._currentRequest.setURI(uri);
     // If |begin| fails, we should get rid of our request.
     try {
       this._currentRequest.begin();
     }
     finally {
       this._currentRequest = null;
     }
   },
   get gethashUrl() {
     return this._getHashUrl;
   },
   // Because we hold off on making a request until we have a valid getHashUrl,
   // we kick off the process here.
   set gethashUrl(aNewUrl) {
     this._getHashUrl = aNewUrl;
     if (this._currentRequest) {
       Services.tm.currentThread.dispatch(this, Ci.nsIThread.DISPATCH_NORMAL);
     }
   },
   // This handles all the logic about setting a back off time based on
   // server responses. It should only be called once in the life time of a
   // request.
   // The logic behind backoffs is documented in the Google Safe Browsing API,
   // the general idea is that a completer should go into backoff mode after
   // BACKOFF_ERRORS errors in the last BACKOFF_TIME seconds. From there,
   // we do not make a request for BACKOFF_INTERVAL seconds and for every failed
   // request after that we double how long to wait, to a maximum of BACKOFF_MAX.
   // Note that even in the case of a successful response we still keep a history
   // of past errors.
   noteServerResponse: function HC_noteServerResponse(aSuccess) {
     if (aSuccess) {
       this._backoff = false;
       this._nextRequestTime = 0;
       this._backoffTime = 0;
       return;
     }
     let now = Date.now();
     // We only alter the size of |_errorTimes| here, so we can guarantee that
     // its length is at most BACKOFF_ERRORS.
     this._errorTimes.push(now);
     if (this._errorTimes.length > BACKOFF_ERRORS) {
       this._errorTimes.shift();
     }
     if (this._backoff) {
       this._backoffTime *= 2;
     } else if (this._errorTimes.length == BACKOFF_ERRORS &&
                ((now - this._errorTimes[0]) / 1000) <= BACKOFF_TIME) {
       this._backoff = true;
       this._backoffTime = BACKOFF_INTERVAL;
     }
     if (this._backoff) {
       this._backoffTime = Math.min(this._backoffTime, BACKOFF_MAX);
       this._nextRequestTime = now + (this._backoffTime * 1000);
     }
   },
   // This is not included on the interface but is used to communicate to the
   // HashCompleterRequest. It returns a time in milliseconds.
   get nextRequestTime() {
     return this._nextRequestTime;
   },
   observe: function HC_observe(aSubject, aTopic, aData) {
     if (aTopic == "xpcom-shutdown") {
       this._shuttingDown = true;
     }
   },
 };
 function HashCompleterRequest(aCompleter) {
   // HashCompleter object that created this HashCompleterRequest.
   this._completer = aCompleter;
   // The internal set of hashes and callbacks that this request corresponds to.
   this._requests = [];
   // URI to query for hash completions. Largely comes from the
   // browser.safebrowsing.gethashURL pref.
   this._uri = null;
   // nsIChannel that the hash completion query is transmitted over.
   this._channel = null;
   // Response body of hash completion. Created in onDataAvailable.
   this._response = "";
   // Whether we have been informed of a shutdown by the xpcom-shutdown event.
   this._shuttingDown = false;
 }
 HashCompleterRequest.prototype = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIRequestObserver,
                                          Ci.nsIStreamListener,
                                          Ci.nsIObserver,
                                          Ci.nsISupports]),
   // This is called by the HashCompleter to add a hash and callback to the
   // HashCompleterRequest. It must be called before calling |begin|.
   add: function HCR_add(aPartialHash, aCallback) {
     this._requests.push({
       partialHash: aPartialHash,
       callback: aCallback,
       responses: [],
     });
   },
   // This initiates the HTTP request. It can fail due to backoff timings and
   // will notify all callbacks as necessary.
   begin: function HCR_begin() {
     if (Date.now() < this._completer.nextRequestTime) {
       this.notifyFailure(Cr.NS_ERROR_ABORT);
       return;
     }
     Services.obs.addObserver(this, "xpcom-shutdown", false);
     try {
       this.openChannel();
     }
     catch (err) {
       this.notifyFailure(err);
       throw err;
     }
   },
   setURI: function HCR_setURI(aURI) {
     this._uri = aURI;
   },
   // Creates an nsIChannel for the request and fills the body.
   openChannel: function HCR_openChannel() {
     let loadFlags = Ci.nsIChannel.INHIBIT_CACHING |
                     Ci.nsIChannel.LOAD_BYPASS_CACHE;
     let channel = Services.io.newChannelFromURI(this._uri);
     channel.loadFlags = loadFlags;
     this._channel = channel;
     let body = this.buildRequest();
     this.addRequestBody(body);
     channel.asyncOpen(this, null);
   },
   // Returns a string for the request body based on the contents of
   // this._requests.
   buildRequest: function HCR_buildRequest() {
     // Sometimes duplicate entries are sent to HashCompleter but we do not need
     // to propagate these to the server. (bug 633644)
     let prefixes = [];
     for (let i = 0; i < this._requests.length; i++) {
       let request = this._requests[i];
       if (prefixes.indexOf(request.partialHash) == -1) {
         prefixes.push(request.partialHash);
       }
     }
     // Randomize the order to obscure the original request from noise
     // unbiased Fisher-Yates shuffle
     let i = prefixes.length;
     while (i--) {
       let j = Math.floor(Math.random() * (i + 1));
       let temp = prefixes[i];
       prefixes[i] = prefixes[j];
       prefixes[j] = temp;
     }
     let body;
     body = PARTIAL_LENGTH + ":" + (PARTIAL_LENGTH * prefixes.length) +
            "\n" + prefixes.join("");
     return body;
   },
   // Sets the request body of this._channel.
   addRequestBody: function HCR_addRequestBody(aBody) {
     let inputStream = Cc["@mozilla.org/io/string-input-stream;1"].
                       createInstance(Ci.nsIStringInputStream);
     inputStream.setData(aBody, aBody.length);
     let uploadChannel = this._channel.QueryInterface(Ci.nsIUploadChannel);
     uploadChannel.setUploadStream(inputStream, "text/plain", -1);
     let httpChannel = this._channel.QueryInterface(Ci.nsIHttpChannel);
     httpChannel.requestMethod = "POST";
   },
   // Parses the response body and eventually adds items to the |responses| array
   // for elements of |this._requests|.
   handleResponse: function HCR_handleResponse() {
     if (this._response == "") {
       return;
     }
     let start = 0;
     let length = this._response.length;
     while (start != length)
       start = this.handleTable(start);
   },
   // This parses a table entry in the response body and calls |handleItem|
   // for complete hash in the table entry.
   handleTable: function HCR_handleTable(aStart) {
     let body = this._response.substring(aStart);
     // deal with new line indexes as there could be
     // new line characters in the data parts.
     let newlineIndex = body.indexOf("\n");
     if (newlineIndex == -1) {
       throw errorWithStack();
     }
     let header = body.substring(0, newlineIndex);
     let entries = header.split(":");
     if (entries.length != 3) {
       throw errorWithStack();
     }
     let list = entries[0];
     let addChunk = parseInt(entries[1]);
     let dataLength = parseInt(entries[2]);
     if (dataLength % COMPLETE_LENGTH != 0 ||
         dataLength == 0 ||
         dataLength > body.length - (newlineIndex + 1)) {
       throw errorWithStack();
     }
     let data = body.substr(newlineIndex + 1, dataLength);
     for (let i = 0; i < (dataLength / COMPLETE_LENGTH); i++) {
       this.handleItem(data.substr(i * COMPLETE_LENGTH, COMPLETE_LENGTH), list,
                       addChunk);
     }
     return aStart + newlineIndex + 1 + dataLength;
   },
   // This adds a complete hash to any entry in |this._requests| that matches
   // the hash.
   handleItem: function HCR_handleItem(aData, aTableName, aChunkId) {
     for (let i = 0; i < this._requests.length; i++) {
       let request = this._requests[i];
       if (aData.substring(0,4) == request.partialHash) {
         request.responses.push({
           completeHash: aData,
           tableName: aTableName,
           chunkId: aChunkId,
         });
       }
     }
   },
   // notifySuccess and notifyFailure are used to alert the callbacks with
   // results. notifySuccess makes |completion| and |completionFinished| calls
   // while notifyFailure only makes a |completionFinished| call with the error
   // code.
   notifySuccess: function HCR_notifySuccess() {
     for (let i = 0; i < this._requests.length; i++) {
       let request = this._requests[i];
       for (let j = 0; j < request.responses.length; j++) {
         let response = request.responses[j];
         request.callback.completion(response.completeHash, response.tableName,
                                     response.chunkId);
       }
       request.callback.completionFinished(Cr.NS_OK);
     }
   },
   notifyFailure: function HCR_notifyFailure(aStatus) {
     for (let i = 0; i < this._requests; i++) {
       let request = this._requests[i];
       request.callback.completionFinished(aStatus);
     }
   },
   onDataAvailable: function HCR_onDataAvailable(aRequest, aContext,
                                                 aInputStream, aOffset, aCount) {
     let sis = Cc["@mozilla.org/scriptableinputstream;1"].
               createInstance(Ci.nsIScriptableInputStream);
     sis.init(aInputStream);
     this._response += sis.readBytes(aCount);
   },
   onStartRequest: function HCR_onStartRequest(aRequest, aContext) {
     // At this point no data is available for us and we have no reason to
     // terminate the connection, so we do nothing until |onStopRequest|.
   },
   onStopRequest: function HCR_onStopRequest(aRequest, aContext, aStatusCode) {
     Services.obs.removeObserver(this, "xpcom-shutdown");
     if (this._shuttingDown) {
       throw Cr.NS_ERROR_ABORT;
     }
     if (Components.isSuccessCode(aStatusCode)) {
       let channel = aRequest.QueryInterface(Ci.nsIHttpChannel);
       let success = channel.requestSucceeded;
       if (!success) {
         aStatusCode = Cr.NS_ERROR_ABORT;
       }
     }
     let success = Components.isSuccessCode(aStatusCode);
     this._completer.noteServerResponse(success);
     if (success) {
       try {
         this.handleResponse();
       }
       catch (err) {
         dump(err.stack);
         aStatusCode = err.value;
         success = false;
       }
     }
     if (success) {
       this.notifySuccess();
     } else {
       this.notifyFailure(aStatusCode);
     }
   },
   observe: function HCR_observe(aSubject, aTopic, aData) {
     if (aTopic != "xpcom-shutdown") {
       return;
     }
     this._shuttingDown = true;
     if (this._channel) {
       this._channel.cancel(Cr.NS_ERROR_ABORT);
     }
   },
 };
 // Converts a URL safe base64 string to a normal base64 string. Will not change
 // normal base64 strings. This is modelled after the same function in
 // nsUrlClassifierUtils.h.
 function unUrlsafeBase64(aStr) {
   return !aStr ? "" : aStr.replace(/-/g, "+")
                           .replace(/_/g, "/");
 }
 function errorWithStack() {
   let err = new Error();
   err.value = Cr.NS_ERROR_FAILURE;
   return err;
 }
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([HashCompleter]);