RawBearer API

[tdammers]

Description

This provides a socket-like API for Snockets (backed by sockets / named pipes, or simulated in IOSim), reading/writing directly to/from raw memory buffers.

This will be needed to securely send KES keys over a network connection or local pipe, because we need to ensure that key data is never stored on disk, nor on the GHC heap, from where it might be swapped to disk.

For context, see also:

• https://github.com/input-output-hk/cardano-base/pull/255: KES Secure Forgetting
• https://github.com/input-output-hk/cardano-base/issues/312: KES Agent
• https://github.com/input-output-hk/cardano-base/pull/317: KES Agent prerequisites

Checklist

• Branch
  • [X] Commit sequence broadly makes sense
  • [X] Commits have useful messages
  • [X] The documentation has been properly updated
  • [X] New tests are added if needed and existing tests are updated
  • [X] Any changes affecting Consensus packages must have an entry in the appropriate changelog.d directory created using scriv. If in doubt, see the Consensus release process.
  • (n/a) If this branch changes Network and has any consequences for downstream repositories or end users, said changes must be documented in interface-CHANGELOG.md
  • [X] If serialization changes, user-facing consequences (e.g. replay from genesis) are confirmed to be intentional.
• Pull Request
  • [X] Self-reviewed the diff
  • [X] Useful pull request description at least containing the following information:
    • What does this PR change?
    • Why these changes were needed?
    • How does this affect downstream repositories and/or end-users?
    • Which ticket does this PR close (if any)? If it does, is it linked?
  • [X] Reviewer requested

[coot]

It can be merged once CI passes, we should merge it after #4571.

[coot]

There's a conflict in CHANGELOG.md; Could you squash / clean the branch a bit before merging?

[coot]

@tdammers do we still need this PR?

[coot]

@tdammers have you pushed your changes?

[tdammers]

Everything pushed now.