Messages in this thread | | | Date | Sat, 17 Aug 2002 23:57:24 -0500 | From | Oliver Xymoron <> | Subject | Re: [PATCH] (0/4) Entropy accounting fixes |
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On Sat, Aug 17, 2002 at 11:51:52PM -0400, Robert Love wrote: > On Sat, 2002-08-17 at 23:05, Linus Torvalds wrote: > > > This is particularly true on things like embedded routers, where the > > machine usually doesn't actually _run_ much user-level software, but is > > just shuffling packets back and forth. Your logic seems to make it not add > > any entropy from those packets, which can be _deadly_ if then the router > > is also used for occasionally generating some random numbers for other > > things. > > Agreed. Further, embedded routers - since they are headless/diskless - > have problems even with the _current_ /dev/random code. They simply do > not generate enough entropy to fulfill sshd requests [1].
This analysis actually stemmed from my work to port OpenSSH to a headless (non-UNIX, non-POSIX, non-protected-memory, diskless) network appliance. SSH only needs real entropy for the keys generated by ssh-keygen. It's complete overkill for session keys.
And guess what? Stock Portable OpenSSH (v3.4p1) uses /dev/urandom (configure.ac):
# Check for user-specified random device, otherwise check /dev/urandom AC_ARG_WITH(random, [ --with-random=FILE read entropy from FILE (default=/dev/urandom)],
> Saying "use /dev/urandom" in this case means we may as well not have a > /dev/random. There is a difference between incorrect accounting (which > it seems you have identified) and just too strict gathering behavior. > > Robert Love > > [1] this is why I wrote my netdev-random patches. some machines just > have to take the entropy from the network card... there is nothing > else.
This patch is perfectly compatible with your netdev-random patches, in fact I encourage it's resubmission after this one gets in. /dev/urandom users will get all the benefits of network sampling without /dev/random suffering at all.
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