fc-luks: specify rekey parameters

[osnyx]

When rekeying LUKS volumes, accidentally the default cipher and PBKDF parameters had been used. Instead, explicitly specify our tunables that we've decided on using.

PL-133174

@flyingcircusio/release-managers

Release process

• Created changelog entry using ./changelog.sh

PR release workflow (internal)

• PR has internal ticket
• internal issue ID (PL-…) part of branch name
• internal issue ID mentioned in PR description text
• ticket is on Platform agile board
• ticket state set to Pull request ready
• if ticket is more urgent than within the next few days, directly contact a member of the Platform team

Design notes

• Provide a feature toggle if the change might need to be adjusted/reverted quickly depending on context. Consider whether the default should be on or off. Example: rate limiting.
• All customer-facing features and (NixOS) options need to be discoverable from documentation. Add or update relevant documentation such that hosted and guided customers can understand it as well.

Security implications

• Security requirements defined? (WHERE)

  • disk encryption shall use the desired pinned encryption parameters
  • fixes a regression discovered via an existing monitoring check (hence decided not to extend test coverage

• Security requirements tested? (EVIDENCE)

  • automated tests still pass
  • successfully fixed wrong encryption parameters on a development hosts via rekeying