Develop Reference

Can someone please explain to me why we need Firebase security rules when I can literally write rules in my client code?

I don't know if my question is inside the proximity of what I should be asking on stack overflow but if so...
Why do we need to write security rules in 'Firebase "Rules"' when I can literally just go into my client code and say:
db.collection("users").get().then(res=> {
res.docs.map(user => {
if (user.data().uid !== auth.currentUser.uid) {
// do something I'm about to put in this code snippet
}
})
})
Like, can someone just get in my client-side code and write whatever they want and that's why we need to write code in the security rules within the Firebase console?
It also confuses me why we need Firebase functions when we can simply do the logic on the client-side although I can understand some stuff needs to be done server-side.
But just for the scope of this question, can someone explain to me clearly why we can't just write our security inside of our code to make things work?
Hopefully I was thorough with the info. Thanks.

Firebase also has a REST API which allows anyone to make requests to your Firebase services directly without any of your code in play.
So even if reverse engineering and modifying the code was impossible, there's the REST API.
You must not trust client applications (especially web apps) and always validate the incoming data and ensure only authorized users can modify it.
How would they get the information needed to make API calls to my database though? And wouldn't they need a key?
If you check the Firebase config, it contains an API key which is used to identify your Firebase project only and there's no risk involved in that being visible.
Now that anyone on the internet knows address of your database, they can use it with REST API if you don't have any security rules setup.
Do note that after running the db.collection("users").get() query, all the documents have been fetched already (and data should be visible in network tab) from Firestore and then you are just looping over all the documents to find one that matches the current user's UID.
This query without security rules is insecure (unless listing users is a feature of your application):
db.collection("users").get().then(res => {
const user res.docs.find(user => user.data().uid === auth.currentUser.uid)
})
Instead you should use queries or access user specific documents and have security rules as shown below to ensure a user can read/write their own data only:
db.collection("users").doc(auth.currentUser.uid).get().then(res => {
console.log("user:", res.data())
})
// Security rules
match /users/{userId} {
allow read, write: if request.auth.uid === userId;
}

Communicating with a web widget-Meteor, React, Node

I'm building a chat dashboard and widget with which a customer should be able to put the widget into their page. Some similar examples would be Intercom or Drift.
Currently, the "main" application is written in Meteor.js (it's front end is in React). I've written a <Widget /> component and thrown it inside a /widget directory. Inside this directory, I also have an index.jsx file, which simply contains the following:
import React from 'react';
import ......
ReactDOM.render(
<Widget/>,
document.getElementById('widget-target')
);
I then setup a webpack configuration with an entry point at index.jsx and when webpack is run spits out a bundle.js in a public directory.
This can then be included on another page by simply including a script and div:
<script src="http://localhost:3000/bundle.js" type="text/javascript"></script>
<div id="widget-target"></div>
A few questions:
What is wrong with this implementation? Are their any security issues to be aware of? Both the examples linked earlier seem make use of an iframe in one form or another.
What is the best way to communicate with my main meteor application? A REST API? Emit events with Socket.io? The widget is a chat widget, so I need to send messages back and forth.
How can I implement some sort of unique identifier/user auth for the user and the widget? Currently, the widget is precompiled.

1 What is wrong with this implementation? Are their any security issues to be aware of? Both the examples linked earlier seem make use of an iframe in one form or another.
As #JeremyK mentioned, you're safer within an iFrame. That being said, there's a middle route that many third parties (Facebook, GA, ...) are using, including Intercom:
ask users to integrate your bundled code within their webpage. It's then up to you to ensure you're not introducing a security vulnerability on their site. This code will do two things:
take care of setting up an iframe, where the main part of your service is going to happen. You can position it, style it etc. This ensure that all the logic happening in the iframe is safe and you're not exposed.
expose some API between your customer webpage and your iframe, using window messaging.
the main code (the iframe code) is then loaded by this first script asynchronously, and not included in it.
For instance Intercom ask customers to include some script on their page: https://developers.intercom.com/docs/single-page-app#section-step-1-include-intercom-js-library that's pretty small (https://js.intercomcdn.com/shim.d97a38b5.js). This loads extra code that sets the iFrame and expose their API that will make it easy to interact with the iFrame, like closing it, setting user properties etc.
2 What is the best way to communicate with my main meteor application? A REST API? Emit events with Socket.io? The widget is a chat widget, so I need to send messages back and forth.
You've three options:
Build your widget as an entire Meteor app. This will increase the size of the code that needs to be loaded. In exchange for the extra code, you can communicate with your backend through the Meteor API, like Meteor.call, get the reactivity of all data (for instance if you send a response to a user through your main Meteor application, the response would pop up on the client with no work to do as long as they are on the same database (no need to be on the same server)), and the optimistic UI. In short you've all what Meteor offers here, and it's probably going to be easier to integrate with your existing backend that I assume is Meteor.
Don't include Meteor. Since you're building a chat app, you'll probably need socket.io over a traditional REST API. For sure you can do a mix of both
Use Meteor DDP. (it's kind of like socket.io, but for Meteor. Meteor app use that for all requests to the server) This will include less things that the full Meteor and probably be easier to integrate to your Meteor backend than a REST API / socket.io, and will be some extra work over the full Meteor.
3 How can I implement some sort of unique identifier/user auth for the user and the widget?
This part should probably do some work on the customer website (vs in your iframe) so that you can set cookies on his page, and send that data to your iframe that's gonna talk to your server and identify the user. Wether you use artwells:accounts-guest (that's based on meteor:accounts-base) is going to depend on wether you decide to include Meteor in your iframe.
If you don't have Meteor in your iframe, you can do something like:
handle user creation yourself, by simply doing on your server
.
const token = createToken();
Users.insert({ tokens: [token] });
// send the token back to your iframe
// and set is as a cookie on your customer website
then for each call to your server, on your iframe:
.
let token;
const makeRequest = async (request) => {
token = token || getCookieFromCustomerWebsite();
// pass the token to your HTTP / socket.io / ... request.
// in the header of whatever
return await callServer(token, request);
};
in the server have a middleware that sets the user. Mine looks like:
.
const loginAs = (userId, cb) => {
DDP._CurrentInvocation.withValue(new DDPCommon.MethodInvocation({
isSimulation: false,
userId,
}), cb);
};
// my middleware that run on all API requests for a non Meteor client
export const identifyUserIfPossible = (req, res, next) => {
const token = req.headers.authorization;
if (!token) {
return next();
}
const user = Users.findOne({ tokens: token });
if (!user) {
return next();
}
loginAs(user._id, () => {
next();
// Now Meteor.userId() === user._id from all calls made on that request
// So you can do Meteor.call('someMethod') as you'd do on a full Meteor stack
});
};

Asking your customers to embed your code like this doesn't follow the principles of Security by Design.
From their point of view, you are asking them to embed your prebundled code into their website, exposing their site up to any hidden security risks (inadvertent or deliberately malicious) that exist in your code which would have unrestricted access to their website's DOM, localstorage, etc.
This is why using an iframe is the prefered method to embed third party content in a website, as that content is sandboxed from the rest of it's host site.
Further, following the security principle of 'Least Privilege' they (with your guidance/examples) can set the sandbox attribute on the iframe, and explicitly lockdown via a whitelist the privileges the widget will have.
Loading your widget in an iframe will also give you more flexibility in how it communicates with your servers. This could now be a normal meteor client, using meteor's ddp to communicate with your servers. Your other suggestions are also possible.
User auth/identification depends on the details of your system. This could range from using Meteor Accounts which would give you either password or social auth solutions. Or you could try an anonymous accounts solution such as artwells:accounts-guest.
html5rocks article on sandboxed-iframes

Torii provider name from adapter?

I have a Torii adapter that is posting my e.g. Facebook and Twitter authorization tokens back to my API to establish sessions. In the open() method of my adapter, I'd like to know the name of the provider to write some logic around how to handle the different types of providers. For example:
// app/torii-adapters/application.js
export default Ember.Object.extend({
open(authorization) {
if (this.provider.name === 'facebook-connect') {
var provider = 'facebook';
// Facebook specific logic
var data = { ... };
}
else if (this.provider.name === 'twitter-oauth2') {
var provider = 'twitter';
// Twitter specific logic
var data = { ... };
}
else {
throw new Error(`Unable to handle unknown provider: ${this.provider.name}`);
}
return POST(`/api/auth/${provider}`, data);
}
}
But, of course, this.provider.name is not correct. Is there a way to get the name of the provider used from inside an adapter method? Thanks in advance.
UPDATE: I think there are a couple ways to do it. The first way would be to set the provider name in localStorage (or sessionStorage) before calling open(), and then use that value in the above logic. For example:
localStorage.setItem('providerName', 'facebook-connect');
this.get('session').open('facebook-connect');
// later ...
const providerName = localStorage.getItem('providerName');
if (providerName === 'facebook-connect') {
// ...
}
Another way is to create separate adapters for the different providers. There is code in Torii to look for e.g. app-name/torii-adapters/facebook-connect.js before falling back on app-name/torii-adapters/application.js. I'll put my provider-specific logic in separate files and that will do the trick. However, I have common logic for storing, fetching, and closing the session, so I'm not sure where to put that now.
UPDATE 2: Torii has trouble finding the different adapters under torii-adapters (e.g. facebook-connect.js, twitter-oauth2.js). I was attempting to create a parent class for all my adapters that would contain the common functionality. Back to the drawing board...
UPDATE 3: As #Brou points out, and as I learned talking to the Torii team, fetching and closing the session can be done—regardless of the provider—in a common application adapter (app-name/torii-adapters/application.js) file. If you need provider-specific session-opening logic, you can have multiple additional adapters (e.g. app-name/torii-adapters/facebook-oauth2.js) that may subclass the application adapter (or not).
Regarding the session lifecycle in Torii: https://github.com/Vestorly/torii/issues/219
Regarding the multiple adapters pattern: https://github.com/Vestorly/torii/issues/221
Regarding the new authenticatedRoute() DSL and auto-sesssion-fetching in Torii 0.6.0: https://github.com/Vestorly/torii/issues/222
UPDATE 4: I've written up my findings and solution on my personal web site. It encapsulates some of the ideas from my original post, from #brou, and other sources. Please let me know in the comments if you have any questions. Thank you.

I'm not an expert, but I've studied simple-auth and torii twice in the last weeks. First, I realized that I needed to level up on too many things at the same time, and ended up delaying my login feature. Today, I'm back on this work for a week.
My question is: What is your specific logic about?
I am also implementing provider-agnostic processing AND later common processing.
This is the process I start implementing:
User authentication.
Basically, calling torii default providers to get that OAuth2 token.
User info retrieval.
Getting canonical information from FB/GG/LI APIs, in order to create as few sessions as possible for a single user across different providers. This is thus API-agnotic.
➜ I'd then do: custom sub-providers calling this._super(), then doing this retrieval.
User session fetching or session updates via my API.
Using the previous canonical user info. This should then be the same for any provider.
➜ I'd then do: a single (application.js) torii adapter.
User session persistence against page refresh.
Theoretically, using simple-auth's session implementation is enough.
Maybe the only difference between our works is that I don't need any authorizer for the moment as my back-end is not yet secured (I still run local).
We can keep in touch about our respective progress: this is my week task, so don't hesitate!
I'm working with ember 1.13.
Hope it helped,
Enjoy coding! 8-)

How a fully scalable SPA with a solid backend is built

the past few weeks I've been hard at work with Angular, Node, TDD, Heroku, Amazon S3 etc. Trying to get a better picture of how a fully scalable SPA with a solid backend is built, working with grunt, bower, haven't dipped my toes in TDD using Jasmine yet, though I understand how the tests are being made through Karma, this is supposedly my next step.
One thing is sure: IT IS A LOT OF INFORMATION
On to the Questions/Rationale on working with all these technologies.
First things first, I played with
Angular App https://github.com/angular-app/angular-app
NG Boilerplate https://github.com/joshdmiller/ng-boilerplate
and read many dozens of posts etc.
I found NG Boilerplate to be most logical structured (as far as my understanding of these things go).
As a demo project (which evolved from something really small) I want to make a Single Page CRUD Application using:
NodeJS as backend
Express as a web app framework
NG Boilerplate as the Client
The app deployed to Heroku
MongoDB for DB
Amazon S3 for dynamic storage
Now I want to use Angular-Apps's (https://github.com/angular-app/angular-app) server as a backend to my NGBoilerplate kickstarter
I want to know how:
from what I see the client connects directly to MongoDB?
how does the angular client communicate back and forth to express ?
I read an interesting article http://www.espeo.pl/2012/02/26/authentication-in-angularjs-application related to how the authentication works.
Long Story Short, without me asking a ton of questions, could someone please describe in detail the workflow of such an app? Getting the session, login, access to editing the content, tying express routes to angular routes (e.g. X route can be accessed by the admin only) etc. ##
there'a big blur in my head :).

In the last months I played a lot with these issues and questions and I got to the following conclusion:
For my purposes, I needed an app that relies almost entirely on Angular, without a separate backend, and the present backend should be from Angular.
Why? Because I want all of my eggs in one basket, I don’t want to configure a ton of stuff on a lot of different parts.
As a basis for my project I ended up using ng-boilerplate, as a boilerplate :), with some changes to the development process, Grunt tasks etc, this is for everybody to figure out, depending on each particular project.
Well, the main issue I’m gonna touch here is that, for a true backend, made in Angular, we need secure routes and a secure persistence method, a database.
For the app, I took advantage of the ng-boilerplate's modular and dependency aware structure, I think it’s perfect for a Angular app.
Anyhow, I’m gonna take things top to bottom (final product wise, the build env as I said above, it’s up to you, but ng-boilerplate is awesome), here we go.
On the upper layer we have the actual Angular app, made just the way we want
The server container, is a NodeJS server with express and other modules to take PARTIAL care of the routing on different browsers and devices (In my app, I made HTML5 routing that is augmented by express, .htaccess like settings whenever there’s a partial URL it should redirect to index where Angular will read the path requested and zapp you to that location)
For my case, the whole things runs on Heroku, on a Node.JS application, you can install several other things there if you want to.
Now, for the persistency, to have authentication and security, and NOT to rely on backend for that, I am using firebase (https://www.firebase.com/), there’s some great tutorials there to help you going and have true persistence in your Angular APP, with routes when you are logged in, access to custom tables/objects in DB when you are logged in etc. It’s the real deal.
If you don’t want to rely OAuth’s possible sites to log in with (Facebook, github, persona or twitter) and want custom emails and addresses you can do that directly with Firebase, to create accounts and delete them etc.
FIREBASE Angular Backend.
So, Firebase, just like they say on the site is a powerful API to store and sync data in realtime.
I don’t know exactly how to approach this, so I’m gonna start it with creating a Firebase database. Once we create it, in the backend we have several options, one of which is security.
{
"rules": {
".read": true,
".write": "auth != null"
}
}
Here, if we read the documentation on https://www.firebase.com/docs/security/security-rules.html we’ll learn that we can add rules for each ‘table' in our database, so we can have like 3 protected ’table’ objects and some that are not protected.
We can protect tables per user basis, per different rules, if logged in or not, we also have inheritance for rules etc, pleas read the documentation there, it really is a good read.
Now, for these rules to take effect we need to enable the Firebase Simple Login and select the desired login method, from Facebook, Twitter, Github, Persona, Email&Password and Anonymous.
For a real app, we need to write info to DB also as anonymous (user sessions etc) and also as logged (with either of the options above) to store and read information.
Me, I wanted to go the quick easy way and made a Facebook authentication, reading the docs there I made a quick Facebook app, and in the settings of the application on Facebook I’m putting Firebase’s backend https://www.dropbox.com/s/xcd4b8tty1nlbm5/Screenshot%202014-01-22%2013.51.26.png
This gives a interim link to login to Facebook and have access to ’tables’ that are otherwise locked if the rule is auth !=null.
NOW, onto the Angular backend.
Firebase provides a library for us to put in our app, and a SimpleLogin lib, also, for Angular, a factory service called AngularFire.
In my case, I made local firebaseService with use methods that connects to my DB:
angular.module('firebaseService', ['firebase'])
.service('firebaseService', function ($firebase, $rootScope) {
//Input data in Firebase
var URL = "https://glowing-fire-xxxx.firebaseio.com";
var tellFirebase = function(ID, JSON) {
users = $firebase(new Firebase(URL + '/' + ID));
users.details = JSON;
users.$save('details');
};
return {
addUser: function(ID, JSON) {
tellFirebase(ID, JSON);
if ($rootScope.debugStatus === true) {
console.log('Firebase Service .addUSer Called');
}
},
getUser: function(ID) {
if ($rootScope.debugStatus === true) {
console.log('Firebase Service .getUser Called');
}
}
};
})
From here we do our READ/WRITE, on the controller’s page I have this:
It’s worth noticing that I have a middleware service (storageManagement) where I switch between Firebase and MongoDB, to avoid confusion.
.controller( 'SomeCtrl', function SomeController( $scope, storageManagement, $firebase, $firebaseSimpleLogin ) {
/*===========================
* ==== FIREBASE LOGIN
* ===========================*/
var URL = "https://glowing-fire-XXXXX.firebaseio.com";
var users = new Firebase(URL);
$scope.auth = $firebaseSimpleLogin(users, function(error, user){});
if ($scope.auth.user == null) {
//$scope.auth.$login('facebook');
}
console.log($scope.auth);
//$scope.auth.$logout('facebook');
$scope.doLogin = function() {
console.log($scope.facebookemail);
console.log($scope.facebookpassword);
$scope.auth.$login('facebook');
$scope.$on("$firebaseSimpleLogin:login", function(evt, user) {
storageManagement.runFirebase();
});
/* example of logging in while asking access to permissions like email, user_list, friends_list etc.
* auth.$login('facebook', {
rememberMe: true,
scope: 'email,user_likes'
});*/
};
$scope.doLogout = function() {
$scope.auth.$logout();
};
});
I’m adding the $firebase service to my controller, and the $firebaseSimpleLogin one.
This here exposes to scope two buttons, login/logout, that popup the OAuth window from Facebook, with email/password setting you won't need to to go through this I think, for a full understanding please read the full docs at firebase.
SO, once we are logged, we can access tables described in the rules, if we choose email/password, actually even for Facebook or other methods, we can assign certain rules for certain IDENTITIES, so you could have a ADMIN table where you could save settings that get READ on page load to apply whatever you want.
Now, with routes, we can check for the $scope.auth status, if WE PUT IT IN $rootScope, and check for the status when going to a route, if the status checks, we get to that route and it gets populated with stuff from the DB, otherwise, even if someone hacks it’s way to that route it won’t see anything because there are no permissions to read that table for unauthorized/wrong email users.
This is loosely based on this article, http://www.ng-newsletter.com/posts/back-end-with-firebase.html … I had a hard time changing the mindset from what the guy wrote there, but, after ONE WHOLE day, of reading the docs (and setting up middleware, mind you) from Firebase I figured it out, and it works.
The connection to the DB is exposed like one BIG object where you can do whatever operations you want.
This isn't the most complete explanation, but it should get you well on your way to making some awesome things:D

The best example of this that I've come across is called angular-app.
It's very comprehensive and addresses all your needs. It's written by one of the authors of the fantastic book "Mastering Web Application Development with AngularJS".
https://github.com/angular-app/angular-app
From the github repo:
AngularJS CRUD application demo
Purpose
The idea is to demonstrate how to write a typical, non-trivial CRUD application using AngularJS. To showcase AngularJS in its most advantageous environment we've set out to write a simplified project management tool supporting teams using the SCRUM methodology. The sample application tries to show best practices when it comes to: folders structure, using modules, testing, communicating with a REST back-end, organizing navigation, addressing security concerns (authentication / authorization).
We've learned a lot while using and supporting AngularJS on the mailing list and would like to share our experience.
Stack
Persistence store: MongoDB hosted on MongoLab
Backend: Node.js
Awesome AngularJS on the client
CSS based on Twitter's bootstrap
Build
It is a complete project with a build system focused on AngularJS apps and tightly integrated with other tools commonly used in the AngularJS community:
powered by Grunt.js
test written using Jasmine syntax
test are executed by Karma Test Runner (integrated with the Grunt.js build)
build supporting JS, CSS and AngularJS templates minification
Twitter's bootstrap with LESS templates processing integrated into the build
Travis-CI integration

Publish data from browser app without writing my own server

I need users to be able to post data from a single page browser application (SPA) to me, but I can't put server-side code on the host.
Is there a web service that I can use for this? I looked at Amazon SQS (simple queue service) but I can't call their REST APIs from within the browser due to cross origin policy.
I favour ease of development over robustness right now, so even just receiving an email would be fine. I'm not sure that the site is even going to catch on. If it does, then I'll develop a server-side component and move hosts.

Not only there are Web Services, but nowadays there are robust systems that provide a way to server-side some logic on your applications. They are called BaaS or Backend as a Service providers, usually to provide some backbone to your front end applications.
Although they have multiple uses, I'm going to list the most common in my opinion:
For mobile applications - Instead of having to learn an API for each device you code to, you can use an standard platform to store logic and data for your application.
For prototyping - If you want to create a slick application, but you don't want to code all the backend logic for the data -less dealing with all the operations and system administration that represents-, through a BaaS provider you only need good Front End skills to code the simplest CRUD applications you can imagine. Some BaaS even allow you to bind some Reduce algorithms to calls your perform to their API.
For web applications - When PaaS (Platform as a Service) came to town to ease the job for Backend End developers in order to avoid the hassle of System Administration and Operations, it was just logic that the same was going to happen to the Backend. There are many clones that showcase the real power of this strategy.
All of this is amazing, but I have yet to mention any of them. I'm going to list the ones that I know the most and have actually used in projects. There are probably many, but as far as I know, this one have satisfied most of my news, whether it's any of the previously ones mentioned.
Parse.com
Parse's most outstanding features target mobile devices; however, nowadays Parse contains an incredible amount of API's that allows you to use it as full feature backend service for Javascript, Android and even Windows 8 applications (Windows 8 SDK was introduced a few months ago this year).
How does a Parse code looks in Javascript?
Parse works through classes and objects (ain't that beautiful?), so you first create a specific class (can be done through Javascript, REST or even the Data Browser manager) and then you add objects to specific classes.
First, add up Parse as a script tag in javascript:
<script type="text/javascript" src="http://www.parsecdn.com/js/parse-1.1.15.min.js"></script>
Then, through a given Application ID and a Javascript Key, initialize Parse.
Parse.initialize("APPLICATION_ID", "JAVASCRIPT_KEY");
From there, it's all object manipulation
var Person = Parse.Object.extend("Person"); //Person is a class *cof* uppercase *cof*
var personObject = new Person();
personObject.save({name: "John"}, {
success: function(object) {
console.log("The object with the data "+ JSON.stringify(object) + " was saved successfully.");
},
error: function(model, error) {
console.log("There was an error! The following model and error object were provided by the Server");
console.log(model);
console.log(error);
}
});
What about authentication and security?
Parse has a User based authentication system, which pretty much allows you to store a base of users that can manipulate the data. If map the data with User information, you can ensure that only a given user can manipulate specific data. Plus, in the settings of your Parse application, you can specify that no clients are allowed to create classes, to ensure innecesary calls are performed.
Did you REALLY used in a web application?
Yes, it was my tool of choice for a medium fidelity prototype.
Firebase.com
Firebase's main feature is the ability to provide Real Time to your application without all the hassle. You don't need a MeteorJS server in order to bring Push Notifications to your software. If you know Javascript, you are half way through to bring Real Time magic to your users.
How does a Firebase looks in Javascript?
Firebase works in a REST fashion, and I think they do an amazing job structuring the Glory of REST. As a good example, look at the following Resource structure in Firebase:
https://SampleChat.firebaseIO-demo.com/users/fred/name/first
You don't need to be a rocket scientist to know that you are retrieve the first name of the user "Fred", giving there's at least one -usually there should be a UUID instead of a name, but hey, it's an example, give me a break-.
In order to start using Firebase, as with Parse, add up their CDN Javascript
<script type='text/javascript' src='https://cdn.firebase.com/v0/firebase.js'></script>
Now, create a reference object that will allow you to consume the Firebase API
var myRootRef = new Firebase('https://myprojectname.firebaseIO-demo.com/');
From there, you can create a bunch of neat applications.
var USERS_LOCATION = 'https://SampleChat.firebaseIO-demo.com/users';
var userId = "Fred"; // Username
var usersRef = new Firebase(USERS_LOCATION);
usersRef.child(userId).once('value', function(snapshot) {
var exists = (snapshot.val() !== null);
if (exists) {
console.log("Username "+userId+" is part of our database");
} else {
console.log("We have no register of the username "+userId);
}
});
What about authentication and security?
You are in luck! Firebase released their Security API about two weeks ago! I have yet to explore it, but I'm sure it fills most of the gaps that allowed random people to use your reference to their own purpose.
Did you REALLY used in a web application?
Eeehm... ok, no. I used it in a Chrome Extension! It's still in process but it's going to be a Real Time chat inside a Chrome Extension. Ain't that cool? Fine. I find it cool. Anyway, you can browse more awesome examples for Firebase in their examples page.
What's the magic of these services? If you read your Dependency Injection and Mock Object Testing, at some point you can completely replace all of those services for your own through a REST Web Service provider.
Since these services were created to be used inside any application, they are CORS ready. As stated before, I have successfully used both of them from multiple domains without any issue (I'm even trying to use Firebase in a Chrome Extension, and I'm sure I will succeed soon).
Both Parse and Firebase have Data Browser managers, which means that you can see the data you are manipulating through a simple web browser. As a final disclaimer, I have no relationship with any of those services other than the face that James Taplin (Firebase Co-founder) was amazing enough to lend me some Beta access to Firebase.

You actually CAN use SQS from the browser, even without CORS, as long as you only need the browser to send messages, not receive them. Warning: this is a kludge that would make my CS professors cry.
When you perform a GET request via javascript, the browser will always perform the request, however, you'll only get access to the response if it was from the same origin (protocol, host, port). This is your ticket to ride, since messages can be posted to an SQS queue with just a GET, and who really cares about the response anyways?
Assuming you're using jquery, your queue is https://sqs.us-east-1.amazonaws.com/71717171/myqueue, and allows anyone to post a message, the following will post a message with the body "HITHERE" to the queue:
$.ajax({
url: 'https://sqs.us-east-1.amazonaws.com/71717171/myqueue' +
'?Action=SendMessage' +
'&Version=2012-11-05' +
'&MessageBody=HITHERE'
})
The'll be an error in the console saying that the request failed, but the message will show up in the queue anyways.

Have you considered JSONP? That is one way of calling cross-domain scripts from javascript without running into the same origin policy. You're going to have to set up some script somewhere to send you the data, though. Javascript just isn't up to the task.

Depending in what kind of data you want to send, and what you're going to do with it, one way of solving it would be to post the data to a Google Spreadsheet using Ajax. It's a bit tricky to accomplish though.Here is another stackoverflow question about it.
If presentation isn't that important you can just have an embedded Google Spreadsheet Form.

What about mailto:youremail#goeshere.com ? ihihi
Meantime, you can turn on some free hostings like Altervista or Heroku or somenthing else like them .. so you can connect to their server , if i remember these free services allows servers p2p, so you can create a sort of personal web services and push ajax requests as well, obviously their servers are slow for free accounts, but i think it's enought if you do not have so much users traffic, else you should turn on some better VPS or Hosting or Cloud solution.

Maybe CouchDB can provide what you're after. IrisCouch provides free CouchDB instances. Lock it down so that users can't view documents and have a sensible validation function and you've got yourself an easy RESTful place to stick your data in.