/dev/random vs. /dev/urandom and the krb5 test suite

Tom Yu tlyu at MIT.EDU
Thu Jun 18 14:35:52 EDT 2009

Sam Hartman <hartmans at MIT.EDU> writes:

> So, during normal operation I would not expect Kerberos to use
> /dev/random much.
> I'd expect it to get used at
> * kadmind startup
> * kdb5_util usage
> * possibly (but probably not) krb5kdc

By inspection, only these files contain calls to
krb5_c_random_os_entropy with the "strong" argument set to 1:


> The idea is that long-term cryptographic keys such as TGT keys and
> service keys should use /dev/random to initialize the PRNG.  I would
> not expect the KDC or clients to use /dev/random during normal
> operation nor would I expect startup of KDC and kadmind to use
> non-constant data from /dev/random.
> So, if you do create a krb5.conf option, I think having big warning
> flags would be entirely appropriate.  I don't think you should ever
> need that option in a production environment.

I agree.

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