Trusting CPU and bootloader as entropy sources

[raja-grewal]

Currently the recommendations are:

# Get as much entropy as possible from external sources. The Chacha mixer isn't vulnerable to injected entropy, so even
# malicious sources should not cause problems.
CONFIG_RANDOM_TRUST_BOOTLOADER=y
CONFIG_RANDOM_TRUST_CPU=y

These CONFIGs actually do the opposite as they credit both sources when intialising the CRNG.

Should the CONFIGs not instead be:

CONFIG_RANDOM_TRUST_BOOTLOADER=n
CONFIG_RANDOM_TRUST_CPU=n

This way other entropy is obtained from other sources at the cost of increasing boot time?

[raja-grewal]

Note that the kernel command line options corresponding to these CONFIGs should likely also then be included in the recommendations:

random.trust_bootloader=off
random.trust_cpu=off