Messages in this thread | | | Date | Tue, 12 Nov 2013 20:02:09 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 00/11] random: code cleanups |
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On 11/12/2013 07:32 PM, Theodore Ts'o wrote: > On Tue, Nov 12, 2013 at 05:40:09PM -0500, Greg Price wrote: >> >> Beyond these easy cleanups, I have a couple of patches queued up (just >> written yesterday, not quite finished) to make /dev/urandom block at >> boot until it has enough entropy, as the "Mining your P's and Q's" >> paper recommended and people have occasionally discussed since then. >> Those patches were definitely for after 3.13 anyway, and I'll send >> them when they're ready. I see some notifications and warnings in >> this direction in the random.git tree, which is great. > > One of the things I've been thinking about with respect to making > /dev/urandom block is being able to configure (via a module parameter > which could be specified on the boot command line) which allows us to > set a limit for how long /dev/urandom will block after which we log a > high priority message that there was an attempt to read from > /dev/urandom which couldn't be satisified, and then allowing the > /dev/urandom read to succed. > > The basic idea is that we don't want to break systems, but we do want > to gently coerce people to do the right thing. Otherwise, I'm worried > that distros, or embedded/mobile/consume electronics engineers would > just patch out the check. If we make the default be something like > "block for 5 minutes", and then log a message, we won't completely > break a user who is trying to login to a VM, but it will be obvious, > both from the delay and from the kern.crit log message, that there is > a potential problem here that a system administrator needs to worry > about. >
One thing, too, if we are talking about anything other than boot-time-only blocking: going from a nonblocking to a blocking condition means being able to accept a short read, and right now *many* users of /dev/urandom are not ready to accept a short read.
-hpa
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