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SANS ISC: InfoSec Handlers Diary Blog - Internet Storm Center Diary 2013-09-17 InfoSec Handlers Diary Blog


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Firefox 24.0 and Thunderbird 24.0 just released, both fixing security flaws.
Apple releases security advisory to update to OS X Server v2.2.2, more here: http://support.apple.com/kb/HT1222

Microsoft Releases Out-of-Band Advisory for all Versions of Internet Explorer

Published: 2013-09-17
Last Updated: 2013-09-17 18:28:56 UTC
by John Bambenek (Version: 1)
5 comment(s)

Microsoft just released an advisory on an Internet Explorer vulnerability that would allow for remote execution.  The report references public availability of details of his vulnerability.  The long story short, a targetted attack that gets a user to view a malicious webpage (or malicious content on an otherwise safe webpage) could lead to memory corruption that could execute arbitrary code with the permissions of the logged in user.  Two suggested actions are provided by Microsoft, apply the FixIt provided by Microsoft or deploy EMET 3.0/4.0 which provides generalized protection of memory (and probably not a bad idea to deploy anyway).  Note, the FixIt ONLY applies to 32-bit versions of Internet Explorer.

This post will be updated with more details as the situation warrants.

--
John Bambenek
bambenek \at\ gmail /dot/ com
Bambenek Consulting

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A Random Diary

Published: 2013-09-17
Last Updated: 2013-09-17 13:59:24 UTC
by Johannes Ullrich (Version: 1)
10 comment(s)

The current discussion about breaking encryption algorithm has one common thread: random number generators. No matter the encryption algorithm, if your encryption keys are not random, the algorithm can be brute forced much easier then theoretically predicted based on the strength of the algorithm. All encryption algorithms depend on good random keys and generating good random numbers has long been a problem.

In Unix systems for example, you will have two random devices: /dev/random and /dev/urandom. "random" usually produces random numbers based on some source of entropy. In Linux, parameters like mouse movements, disk activity and interrupts are used. Older versions of the random number generator used network activity, but since the attacker may be able to affect network activity, this parameter is no longer used. The Linux random number generator was found to be not particularly well implemented, in particular on disk less systems and systems with little user activity, like for example routers [1] .

Recently, some implementations of Linux like OpenWRT where found vulnerable if they are used on MIPS based hardware. The random number generator on these systems uses the number of CPU cycles since reboot as a seed. However, the respective function always returns 0, not the actual number of cycles on MIPS. [2]

Are there better ways to collect random numbers? One of the challenges is to increase the amount of entropy (random events) collected. There are some good attempts to use microphones, cameras and other hard ware devices to improve the pool of entropy. Sadly, there are no simple "standardized" solutions to implement these techniques.

Here are a couple pointers to projects that may help you implement better random number generators:

Using the camera in Windows : http://wcrnd.sourceforge.net
using the sound card in Windows: http://sourceforge.net/projects/trng
Linux camera based random number generator: http://sourceforge.net/projects/lavarnd/
Linux sound card random source: http://code.google.com/p/snd-egd/

testing random number generators: http://www.leidinger.net/FreeBSD/dox/dev_rndtest/html/df/d2a/rndtest_8c_source.html (look for "rndtest" in your Linux distro)

Got any other tips to create good random numbers (cheaply)?

[1] http://www.pinkas.net/PAPERS/gpr06.pdf
[2] https://lists.openwrt.org/pipermail/openwrt-devel/2013-September/021318.html

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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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