The Web Won’t Be Safe, Let Alone Secure, Unless We Break It

By Jeremiah GrossmanThere are several security issues affecting all major Web browsers that
have remained unaddressed for years (probably because the bad guys
haven’t leveraged them aggressively enough, but the potential is
there). The problem is that the only known ways to fix these issues
(adequately) is to “break the Web” — i.e. negatively impact the
usability of a significant and unacceptable percentage of websites.
Doing so is a non-starter for any browser vendor looking to grow market
share. The choice is clear for most vendors: Be less secure and adopted, rather than secure and obscure. This is what the choice comes down to. This is a topic deserving of further exploration.

There are several security issues affecting all major Web browsers that
have remained unaddressed for years (probably because the bad guys
haven’t leveraged them aggressively enough, but the potential is
there). The problem is that the only known ways to fix these issues
(adequately) is to “break the Web” — i.e. negatively impact the
usability of a significant and unacceptable percentage of websites.
Doing so is a non-starter for any browser vendor looking to grow market
share. The choice is clear for most vendors: Be less secure and adopted, rather than secure and obscure. This is what the choice comes down to. This is a topic deserving of further exploration.

Web security can be divided into two parts,
Website security and Web Browser security. Both are equally important.
A website must be able to protect itself from a hostile browser and a
browser must be able to protect itself from a hostile website. If
either side of these assumptions fails, then there is a problem (the
Web is not secure). Attacks targeting browsers, which will be the focus
of this post, can be broadly categorized into three distinct vectors:

  1. Attacks designed to escape the confines of the browser walls and
    execute within the desktop operating system below. This is primarily
    achieved by exploiting memory and file-handling implementation flaws.
  2. Behavioral attacks that trick users into doing something, such as
    downloading and installing malware, thereby harming their machine or
    encouraging them to reveal sensitive information.
  3. Attacks
    taking advantage of design flaws in the way the Web works. These
    attacks normally remain within the browser walls and use the victim’s
    browser as a launch platform for surreptitiously pilfering information
    from their session or the surrounding network.

After years of massive volumes of CVEs
(repository for published vulnerabilities), the browser vendor
incumbents (Microsoft, Mozilla, Opera, Google, Apple) have made great
strides in addressing vector #1. Some have more work to do than others.
This is a good thing, as exploiting unpatched browsers is the primary
method for malware propagation such as the so-called
drive-by-downloads, legitimate websites hosting malware that infects
their visitors. Fortunately “fixing” #1 doesn’t require “breaking the
Web,” only updating shoddy code and distributing updates.

Solving
#2 is more psychological than technical in nature. The challenge is
that people trust computer screens, believe what they see on the Web,
and will install anything in order to watch the latest celebrity sex
tape or open a personalized e-greeting sent by their “friend.”
Attackers prey on this inherent trust, general good nature, and basic
human instinct. In response, browsers have provided EV-SSL,
Anti-Phishing Toolbars, SSL warning dialogs, password managers, etc.
These efforts make important security decisions more visible, harder to
get wrong, or remove the decision altogether. Again “fixing” these
issues doesn’t require “breaking the Web,” but creating a more
intuitive user-interface design.

Addressing #3, with roots dating back to the earliest days of the Web, is another matter entirely. Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), Clickjacking, CSS History Stealing, Intranet Hacking,
etc. are all good examples. While these weren’t pressing issue before,
they are trending in a dangerous direction. We’ve seen outbreaks of Twitter worms, XSS Defacements of government websites, Facebook Clickjacking attacks, sites that disclose which porn sites people visit, several Intranet Hacking proof-of-concept tools, and so on.

Many,
including myself, have asked the major browser vendors to do something
about the CSS History Hacking, a privacy violation where a malicious
website can tell if you’ve been to a certain URL, by disabling access
to key DOM APIs. They said doing so would break certain websites and
upset Web developers.

To
solve Intranet Hacking, the suggestion was made to deny websites with a
non-RFC 1918 IP address the ability to passively instruct a browser to
connect to RFC 1918 IP addresses. The response was that it would break
certain essential features like corporate Web proxy set-ups and add-ons
like Google Desktop.

Fixing Clickjacking would require changing
IFRAMES implementation so that they would not be transparent or allowed
at all. Doing so would undoubtedly cause major Web breakage, such as no
banner advertising or Facebook-style application platforms. So instead
we get opt-in X-FRAME-OPTIONS, which basically no one uses at the moment.

Maybe
browser tab/session separation is in order. When logged-in to a website
in one tab, other tabs wouldn’t have session access thereby limiting
the damage XSS, CSRF, and Clickjacking could inflict. But, this
solution would probably annoy users and Web developers who really want
persistent authentication. Oh, and we really need Web tracking cookies
too. Gah!

So here we are, waiting for the other shoe to drop,
and bad enough things to happen. Then we’ll get the juice required to
fix these problems, by default. The bigger problem is when that time
eventually comes we might actually be forced to break the Web to secure
it. In the meantime, the community has been lobbying hard for opt-in
tools that the proactive crowd can use to protect themselves ahead of
time. Fortunately, we are starting to see new technologies like XSSFilter, Content Security Policy, Strict Transport Security, and Origin headers come into view. Maybe this is the future and a look into the security proving ground for the changes we’ll need to make later.

* Jeremiah Grossman is the founder and Chief Technology Officer of WhiteHat Security.

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