mxgrub: Configure Linux to trust CPU manufacturer for CRNG purposes #113
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pmenzel
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On fast booting systems, *amaru* with an NVMe SSD, several messages like
below can be seen.
$ dmesg | grep random
[ 0.293967] random: get_random_bytes called from start_kernel+0x310/0x4d3 with crng_init=0
[ 5.203127] random: fast init done
[ 5.789242] random: systemd-random-: uninitialized urandom read (512 bytes read)
[ 6.648002] random: dbus-daemon: uninitialized urandom read (12 bytes read)
[ 6.649848] random: mxnetctl: uninitialized urandom read (4 bytes read)
[ 7.978264] random: crng init done
[ 7.978265] random: 7 urandom warning(s) missed due to ratelimiting
The Linux kernel is built without `RANDOM_TRUST_CPU`.
> config RANDOM_TRUST_CPU
> bool "Trust the CPU manufacturer to initialize Linux's CRNG"
> depends on X86 || S390 || PPC
> default n
> help
> Assume that CPU manufacturer (e.g., Intel or AMD for RDSEED or
> RDRAND, IBM for the S390 and Power PC architectures) is trustworthy
> for the purposes of initializing Linux's CRNG. Since this is not
> something that can be independently audited, this amounts to trusting
> that CPU manufacturer (perhaps with the insistence or mandate
> of a Nation State's intelligence or law enforcement agencies)
> has not installed a hidden back door to compromise the CPU's
> random number generation facilities. This can also be configured
> at boot with "random.trust_cpu=on/off".
This is a good default, and as we do not want to rebuild the installed Linux
kernels, choose the option to configure this at boot time by adding
random.trust_cpu=on
to the Linux command line. Should there be indications, that the CPU
manufacturers cannot be trusted, we have to think about different means,
by for example plugging in a [ChaosKey][1] into every system. ;-)
[1]: https://altusmetrum.org/ChaosKey/
Fixes: mariux64/bee-files#1556
pmenzel
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