RFC: adding "jitterentropy" library to base

(cem@ and secteam@ BCCed so they can weigh in on this if they like)
Hi,
	A key component for FreeBSD becoming NIST FIPS 140-3 compliant was completed when FreeBSD upgraded from OpenSSL 3.0 to 3.5. One of the other requirements for FIPS 140-3 (and post-quantum cryptography) is having sufficient random entropy in the system to generate sufficiently random numbers. NIST SP800-90B provides some guidelines on how to achieve that [1].
	One capability in the base system that provides such a guarantee is RDSEED [2], but that is CPU/hardware-specific and does not support all possible architectures today. Furthermore, there are discussions of challenges around certifying RDSEED in derivative distributions (including the commit where the support was introduced).
	The jitterentropy project provides an alternative mechanism for this in userspace that is less CPU/hardware-specific [3] [4]..
	This component already exists in ports [4], but in order to ensure that the base system version of OpenSSL can capitalize on it, it needs to be integrated into base and built alongside libcrypto.
	My proposal for how to achieve this is included below, along with some deliverables, rough implementation-specific details, and rough timelines.
	Does anyone have any thoughts on the proposed plan sketched out below?
Thank you,
-Enji

PS I CCed the ports maintainer (swills@), several folks from HPE/Juniper (since they provided the RDSEED implementation), secteam@, etc, to obtain feedback on this work.

# Objective 1: add jitterentropy-library to the base system

- Do a vendor import of the component.
- Add to the base system:
	- Given that it’s a cryptographic-related component, crypto/jitterentropy seems like the most appropriate location for the library.
	- Conditionally enable support in OpenSSL and building the library using the `MK_OPENSSL_JITTERENTROPY` build knob.
	- Add packaging metadata so the component is properly released using `pkgbase`.
	- Integrate any additional programs into the base system which provide health check capabilities described in NIST SP800-90B [1].

## Timeline

The goal is to do this start this work in the next week.

# Objective 2: add additional hardware support to the jitterentropy library.

The library supports the following FreeBSD-available architectures out of the box:
- amd64/i386
- PowerPC

## Timeline

This is not yet on the schedule. Certain CPU support (like aarch64/ARM64) is desired, however.

# Objective 3: introduce a daemon/service for increasing entropy post-boot

One such service exists already [5], but the project uses Linux-specific syscalls and facilities, only provides systemd service integration, etc.

## Timeline

This is not yet on the schedule, but is desirable.

# Objective 4: integrate libjitterentropy into the system as a kernel module/build time module.

## Timeline

This is not yet on the schedule.

# References

1. https://csrc.nist.gov/pubs/sp/800/90/b/final
2. https://cgit.freebsd.org/src/commit/?id=3a12982962ce330c37c154bb2eb8ae0539fc6f48
3. https://github.com/smuellerDD/jitterentropy-library
4. In reality it enables the CRNG mechanism using x86, etc, hardware instructions, but it also allows for hardware independent mechanisms for enabling/increasing system entropy.
5. https://github.com/smuellerDD/jitterentropy-rngd