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Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG |
Date: |
Wed, 13 Mar 2019 11:35:33 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 |
On 3/13/19 10:57 AM, Daniel P. Berrangé wrote:
> We already have an internal API for providing strong random bytes in
> QEMU qcrypto_random_bytes. It is preferentially backed by gnutls or
> gcrypt, but if those aren't built-in it falls back to a platform
> native API like /dev/random. I've got a todo item to make that use
> getrandom on Linux/BSD when available.
>
> I don't think we should be adding a new APIs for getting random
> numbers that aren't backed by the qcrypto_random_bytes.
That's all very well and good for one particular use case, when we really want
random numbers. But with -seed, we want to be able to replicate one particular
execution, with fully deterministic numbers.
But certainly I can look into making the non-deterministic execution use your
existing interface. I simply wasn't aware of it.
Do you happen to know off-hand the maximum latency of the gnutls/gcrypt
interfaces? I do want the interface to be able to return "timed-out" in
certain cases. With getrandom(2) there is a handy GRND_NONBLOCK parameter that
pretty much matches exactly what I want. With /dev/{u,}random, one would have
to use O_NONBLOCK. With BSD getentropy, I think you'd need an alarm to time
out the operation (unless EIO covers all sorts of failures like empty entropy
pool; the manual isn't clear)?
r~
- Re: [Qemu-devel] [PATCH for-4.1 1/7] util: Add qemu_getrandom and support functions, (continued)
- [Qemu-devel] [PATCH for-4.1 6/7] ui/vnc: Use qemu_getrandom for make_challenge, Richard Henderson, 2019/03/13
- [Qemu-devel] [PATCH for-4.1 7/7] target/arm: Implement ARMv8.5-RNG, Richard Henderson, 2019/03/13
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, no-reply, 2019/03/13
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, Daniel P . Berrangé, 2019/03/13
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG,
Richard Henderson <=
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, Daniel P . Berrangé, 2019/03/14
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, Richard Henderson, 2019/03/14
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, Daniel P . Berrangé, 2019/03/14
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, Richard Henderson, 2019/03/14
- Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, Daniel P . Berrangé, 2019/03/14
Re: [Qemu-devel] [PATCH for-4.1 0/7] Add qemu_getrandom and ARMv8.5-RNG, no-reply, 2019/03/13