This is the first post of a – potential – series of rants on ubiquitous pieces of crap (security-wise), bothering pretty much every ISO I know.
And, yes, I can already hear all the yelling “But we absolutely need Flash on our corporate desktops.”. Maybe that’s really really the case. Maybe not. I’ve fought that fight in many environments, and usually lost it. Kind-of been there, done that. I’d just like to point out that – from a security point of view – this is a risky thing.
On a personal level I still do not get why Flash is needed. I can certainly be regarded as a “typical executive user”, being online most parts of the day and performing all sorts of (what I think) “typical actions” like travel booking, online financial services etc. All this can be done with my 64-bit browser that just has no associated Flash player. Seems my mileage as for “corporate browser use” still varies from the one in many of those – “we absolutely need Flash on our corporate desktops” – organizations…
And even if your company’s marketing dept is powerful enough to ask for large scale deployment of that fancy technology (some of you certainly know the “We have our own Youtube channel” argument) I still have to understand why it’s needed on the desktops in the engineering or R+D departments. But oh well…
Still, all this ranting is a bit outside the intended scope of this post. Actually the trigger for the post was this advisory titled “Security Advisory for Flash Player, Adobe Reader and Acrobat” and released by Adobe some days ago.
Here’s a little quote from the summary:
“A critical vulnerability exists in the current versions of Flash Player […] for Windows, Macintosh, Linux and Solaris operating systems, and the authplay.dll component that ships with Adobe Reader and Acrobat v9.x for Windows, Macintosh and UNIX operating systems. This vulnerability […] could cause a crash and potentially allow an attacker to take control of the affected system. There are reports that this vulnerability is being actively exploited in the wild via limited, targeted attacks against Adobe Reader v9 on Windows.”
“A critical vulnerability exists in Adobe Flash Player 10.0.45.2 and earlier versions for Windows, Macintosh, Linux and Solaris operating systems, and the authplay.dll component that ships with Adobe Reader and Acrobat 9.x for Windows, Macintosh and UNIX operating systems. This vulnerability (CVE-2010-1297) could cause a crash and potentially allow an attacker to take control of the affected system. There are reports that this vulnerability is being actively exploited in the wild against both Adobe Flash Player, and Adobe Reader and Acrobat.”
Note the difference?
There’s practically none: same products affected, same component to blame, same workaround [deactivating authplay.dll], same “Adobe’s quality assurance element” [discovery of the stuff being exploited in the wild] responsible for public statement.
In short: SSDD.
Given I try to be a responsible citizen [and, for that matter, responsible security practitioner too ;-)] I’d like to discuss potential approaches as for the efficient mitigation of the risk of being attacked “actively in the wild” due to (not only) this vulnerability.
At ERNW, for many years we’ve been using sth we called “The small catechism of IT security” which was essentially a set of simple fundamental rules as for securing complex systems. This piece included, amongst others, these ones:
Following these lines some approaches come to mind and I’ll discuss some of those.
a) Do not run Flash at all. Yes, we had this discussion already. And, no: I do not live in a ivory tower. And I mainly consult to very large organizations.
Sure, this might be one of the fights you (as an ISO) just can’t win. But, heck, I still dare to post this on our very personal and ranty blog: Running Flash on corporate desktops is simply asking for trouble. Asking for trouble loudly. Very loudly.
It should be noted that, according to this, removing Adobe Flash (e.g. in the way described here) will not remove the instances of Flash Player that is installed with Adobe Reader 9 or other Adobe products.
There is always a lot of trade-offs in managing complex IT environments. There are business requirements – and, as we security folks know: business pretty much always wins (and this is fully ok, as security is not the most important thing in corporate life) -, there’s “cost considerations”, all sorts of politics and in the end of the day there’s our mission of getting the best possible security stance given all these considerations and trade-offs. Running vulnerable software to provide some business functions (while at the same time inducing the risk of getting owned) obviously is such a trade-off, and it’s a common one.
As for Flash one should just be aware that – in most environments – there’s only little business value of running it, but – in all environments – there’s quite some associated risk.
b) Do not run Flash embedded in PDFs (by deactivating authplay.dll as described in the advisories).
I think this is – security-wise – a very feasible approach (following that good ole security principle called “minimal machine”). Only problem might be that the stuff gets re-deployed/re-enabled next time you patch Adobe Reader. So operational processes might have to be adjusted to ensure it does not re-appear.
And, of course, this is an ugly one (deleting a dll), which might not be “aligned with your sw management and deployment processes” 😉
This document mentions that deleting another dll as well avoids the crashes when invoking a file with SWF code in it. Haven’t tested this though.
Btw: this is a preventative control. Whereas patching is a reactive one. Most probably I don’t have to tell any reader of this blog that preventative controls tend to have a better cost-impact ratio than reactive ones, do I? 😉
c) Patching. Hmm, unfortunately there is no patch as of today. And the stuff is “exploited in the wild” (Adobe, thank you! for letting us know, once more. What about just adding a checkbox somewhere in “Preferences” that allows to disable playing embedded SWF stuff at all?).
Furthermore patch cycles for Adobe products are quite long in most environments (due to the number of integration aspects and side effects).
So, dear reader who’s still sympathetic to patching (as for Adobe stuff): do not pass go, do not collect $200, but maybe re-read the last sentences of the two former points.
d) Use of an alternate PDF reader, like Foxit Reader. Looking at this I’m not sure if this is really better (security-wise) and most probably it’s not an option for most corporate environments anyway (for reasons outside the security realm).
e) Security measures/approaches from the “Least privilege” space like “running Adobe stuff on a low integrity level” (on Windows systems disposing of integrity levels, that are Win Vista or Windows 7). While this can certainly help and can be regarded as a nice preventative control, it has the big disadvantage that taking the route of “least privilege” usually has, that is added complexity and high operational cost… (which is, btw, why it practically never works out to a satisfactory degree).
f) Gateway-based controls. In a number of environments there will be quite some praying that “our malicious content protection saves us”. This may happen. or not. Taking the “detective/reactive way” (which is what most anti-malware controls do) has well-known weaknesses…
Sanitizing Flash (like Blitzableiter does) could be a much better approach. Hopefully technologies like this will gain some deployment in the near future.
And hopefully in the upcoming world of HTML5 we won’t see that high risk software piece called Flash player anymore (alas, experience tells there will be other similarly awful stuff. but that’s another story…)
have a great day,