Apr 3, 2014

Uploadcare on Social Networks and Cloud Servers Security

Uploadcare allows users to easily upload files from a growing number of social networks and cloud services. Which raises the obvious question — is it safe? And can others read or even modify user files that are not uploaded to Uploadcare but stored in cloud services? To answer all of these questions, we’d like to explain how Uploadcare works with third-party services.

Uploadcare Neither Requests nor Stores User Passwords

All interaction with services is done over the OAuth or OAuth2 protocols. The way they operate is roughly the same:

  1. The user presses the “Connect to Service” button in the Uploadcare widget. A new tab or window of the selected social network or cloud service is opened.
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  2. The service asks the user to enter his or her username and password on it’s website.
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  3. The service requests permission to provide Uploadcare access to it’s data.
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  4. The service provides Uploadcare with a key, so called “access token”.
  5. Uploadcare uses the access token to access user data.

Step 2 may be skipped if the user is already logged into the service. Step 3 may be skipped if the user has previously allowed access to their data. Steps 2 and 3 can be presented on a single page. This all depends on the service.

The service does not provide Uploadcare with user credentials. Users can revoke access from Uploadcare at any time (this is done on the service side, usually in account settings).

The Site Owner Cannot Interfere With Service Interaction

The authorization and file selection is implemented in the widget, but actually occurs within iframe. Iframe is an HTML element that allows one to open documents from a different domain from within a current document. Thus an external site on which the widget is installed cannot receive any events or data from a document containing a list of user files. The only event that occurs in the widget itself is the user’s selection of a particular file.

Even if the owner of the site on which the Uploadcare widget is installed is ill intentioned, he or she cannot actually get a list of user files or any other form of access to them. The only files he or she has access to is those that have been explicitly chosen by the user. The same rule applies if the site owner uses his own application for the service.

Uploadcare Does Not Have Access to User Data

Sounds weird, but it’s true. We understand that there always remains a remote possibility of server hacking. If someone gained access to an application server that stores access tokens of a large number of users (reference to one of our competitors goes here:), he would then have access to all the files stored in the cloud services of those users. Which is why we do not store access tokens in any way, shape or form. Instead the access token is passed along to the server with each request. The only one who can access his files is the user himself.

The Access Token Cannot Be Intercepted and Decoded

Our service works via the SSL protocol. This means that all traffic between user’s browser and our servers is encrypted, so the attacker will have a very difficult time obtaining the access token from queries. But still, the access token is the key that provides full access to user files, and thus should not fall into the wrong hands even when data is successfully intercepted. Due to this we further encrypt the access token passed in the request so it cannot be used anywhere but on our own server.

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