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Posts tagged ‘Browser’

11
Oct

WebKnock.org: An fwknop SPA web-interface

Vasilis Mavroudis has launched WebKnock.org, a web-based front end to the fwknop (Single Packet Authorization) client. It does not yet seem to support the full suite of fwknop features, but the WebKnock site allows you to send basic auth packets to your fwknop server in order to open firewall ports. This can definitely come in handy if you need access to a port on your server, and don’t have the fwknop client handy on the computer, Android or iPhone (coming soon).

Note that although WebKnock uses SSL to protect the HTTP session, you are required to supply your fwknop password. If logged or intercepted, your knock details could be used to open firewall ports or even run commands on your server (depending on how you’ve configured fwknop). While WebKnock may be useful in a bind, from a purely security standpoint I don’t recommend using it regularly due to this risk. If you do use it, you should consider changing your fwknop passphrase.

I hope that WebKnock is eventually open-sourced to allow both for the code to be reviewed, and for people to host their own instance of WebKnock. It would also be nice to see more fwknop features being added, including the ability to define a username, and open multiple ports at once (eg. by entering: tcp/22 udp/53 tcp/80). The ‘Allow IP’ field should also get pre-populated with the visitor’s IP address for convenience.

Source: Cipherdyne

19
Oct

Persistent Tracking using Supercookies and Evercookies

Normal websites use cookies to keep track of their visitors, either to remember that they are logged in, track statistics, or a number of other purposes. Sites can usually only track users while they are browsing that actual site (apart from Google who tracks you more or less wherever you go), however the past few years have revealed more and more ways web users can be tracked.

The concept of supercookies and ubercookies is not entirely new, but has been refined recently to turn them into digital cockroaches – very hard to permanently get rid of. Supercookies are basically an amalgamation of different software features that can be used to create a uniquely identifying token, usually one that is hard or too convoluted to delete. Now that HTML5 is becoming more widespread, there are even more options than before.

Modern supercookies comprise a number (or all) of the following:

  • Standard HTTP Cookies
  • Local Shared Objects (Flash Cookies)
  • Silverlight Isolated Storage
  • Storing cookies in RGB values of auto-generated, force-cached PNGs using HTML5 Canvas tag to read pixels (cookies) back out
  • Storing cookies in Web History
  • Storing cookies in HTTP ETags
  • Storing cookies in Web cache
  • window.name caching
  • Internet Explorer userData storage
  • HTML5 Session Storage
  • HTML5 Local Storage
  • HTML5 Global Storage
  • HTML5 Database Storage via SQLite

Samy Kamkar recently released Evercookie, a JavaScript API for creating extremely persistent browser cookies. The list above is what is what Evercookie uses to create them. If websites were to start using these techniques, they would be able to uniquely identify you (as a user, not a person) each time you visited, even if you deleted your cookies, cleared your cache, and removed your history (or used a private browsing feature). Due to the use of shared objects, such as Flash, some cookies are persistent even across different browsers!

Ultimately, I wouldn’t panic and stop surfing the web just yet, but this goes to show how the evolution of the browser (and countless plugins that now go with it) is having an effect on privacy and security (which can’t quite keep up the pace set by innovation). Dominic White describes how to delete the Evercookie when using Safari on OSX. Others have written about how to do the same on Firefox and Chrome. One reddit user has created a pseudo lockdown-script which improves the security and privacy of Firefox by making some configuration changes (eg. disabling prefetching, geolocation, caching, etc).

This post by Christopher Soghoian provides a good argument for why privacy (and security, I would add) should be adopted in web browsers by default, instead of letting users fend for themselves. Some browsers are making an effort by adding features such as private browsing, cross-site scripting protection, and Google SafeSearch (although this impacts privacy by sending Google every URL you browse to), however all too often browser plugins and add-ons are given too many privileges.

Browser security and user awareness are becoming more important than ever as traditional programs are phased out and replaced by web applications. Unfortunately both of these are still lagging a bit behind.

22
Jul

Safari AutoFill Information Disclosure (with PoC)

Thanks to Safari’s nifty AutoFill feature, it has long been susceptible to an information disclosure vulnerability which could allow an malicious web page to extract various details stored in your personal vCard in Address Book.

This was highlighted a while back, and today re-emphasized by Jeremiah Grossman with a proof-of-concept attack.

The issue exists due to the way that Safari tries (by default) to auto-populate some of your details, including name, address, telephone number, etc, when you fill out forms. This can only happen if you have ‘AutoFill web forms’ enabled in Safari’s preferences, as shown in the screenshot below:

Uncheck these boxes to prevent this attack… but note that you’ll have to type your own info in afterwards! It’s not a high-risk vulnerability, but if you’re concerned about your privacy whilst browsing and in general, do what I do and don’t actually set an empty card as your personal card in Address Book. You can do this by creating a new card (enter some dummy info if you want), selecting it, and then choosing “Make this my card” from the Card menu.

Apple’s been notified of the issue, however as this is a ‘feature’ and not a bug, it’ll be interesting to see whether they’ll actually choose to do anything about it.

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