Saturday, 16 July 2011

Another issue with the .NET Random class

OK, maybe it is just me, but I was not aware that the random class was not Thread Safe (I was aware that it is recommended that you don't create a new Random object on every use).

I just documented my findings/experience at the O2 Blog http://o2platform.wordpress.com/2011/07/16/humm-net-random-class-is-not-thread-safe/ and, I have to say that I have the feeling that there are a number of security vulnerabilities out there created by this behaviour (think of an multi-thread environment which receives a lot of traffic and uses the Random class for session/key/token/id generation).

And since it requires a certain number of requests/threads to trigger the problem, it might not be easy to detect, debug and/or replicate (note that Random doesn't fail safely... i.e. once the race condition is triggered, it will just return 0).

Here are a couple projects that (look like they) use the Random class: http://www.google.com/codesearch#search/&q=%22new%20Random%22%20lang:%5Ec%23$&type=cs
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