[botan-devel] Tmp dir used as an entropy source

Rickard Bellgrim Rickard.Bellgrim at certezza.net
Tue Sep 3 06:23:16 EDT 2013


Hi

Our OpenDNSSEC/SoftHSM users are concered that "ls -alni /tmp" is used as an entropy source in Unix_EntropySource in Botan. Users can manipulate the contents of that directory and is thus not a good source for entropy. The global RNG in Botan will use other entropy sources first (e.g. /dev/random) and will most likely not use this low priority command when polling for entropy. However, the concensus is that it may be better to just remove it from the list of commands.

An alternative for SoftHSM would also be to declare a similar RNG as the global RNG, but without adding the Unix_EntropySource. In most cases, Botan will use the RNG provided by the application. But when it comes to the RSA blinder, it still uses the global RNG. So you can thus not completly disable the usage of Unix_EntropySource.

I would appreciate any feedback on this topic.

Thanks
// Rickard


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