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    SubjectRe: IRQF_SAMPLE_RANDOM question...
    Matt Mackall wrote:
    > On Tue, 2009-04-07 at 00:09 +0200, Sven-Haegar Koch wrote:
    >> On Mon, 6 Apr 2009, Matt Mackall wrote:
    >>
    >>> On Mon, 2009-04-06 at 14:30 -0400, Robin Getz wrote:
    >>>> We have lots of embedded headless systems (no keyboard/mouse, no soundcard, no
    >>>> video) systems with *no* sources of entropy - and people using SSL.
    >>> I'd rather add a random_sample_network call somewhere reasonably central
    >>> in the network stack. Then we can use the knowledge that the sample is
    >>> network-connected in the random core to decide how to measure its
    >>> entropy. The trouble with IRQF_SAMPLE_RANDOM is that many of its users
    >>> are technically bogus as entropy sources in the current model.
    >>>
    >>> I'm eventually going to move the RNG away from the strict theoretical
    >>> entropy accounting model to a more pragmatic one which will be much
    >>> happier with iffy entropy sources, but that's a ways off.
    >> Btw, perhaps not the perfect question in this thread:
    >> But what should we use to keep servers running without a hardware rng
    >> available and without any external input besides the network?
    >> After having ssh and openvpn die because of no random and having
    >> the machines like dead and unreachable for me I use "ln -sf
    >> /dev/urandom /dev/random", but that does not feel so good.
    >
    > It's fine so long as you're not wearing a tinfoil hat. In fact, as
    > the /dev/random maintainer, I'd recommend it.
    >
    > Ted and I have recently been talking about revisiting the design
    > of /dev/random to avoid these sorts of issues.


    Two points...

    - while I would welcome a more pragmatic entropy accounting model,

    - it seems misplaced to _solely_ address network entropy problems
    (timer-based regularity, external visibility and access) within the
    devrandom machinery.

    IRQF_SAMPLE_RANDOM in network drivers IMO just gives users a false sense
    of security about their entropy.

    And more fundamentally, IRQF_SAMPLE_RANDOM should never be used on a
    non-random source.

    Jeff





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