Draft: examine exit status of keyscripts

This adds functions which read from standard input, encode/decode that to/from the “Base64 Encoding” (see RFC 4648) and print the result to standard output.

For the encoding/decoding, either base64 (which is part of the essential package coreutils) or uuencode/uudecode may be used.

In the “normal” userspace the former is always available and thus preferred. It should therefore be impossible that an incompatible switch is made from encoding with base64 respectively uuencode to decoding with uudecode respectively base64.

In the early userspace (that is: “within” the initramfs during booting) uuencode/uudecode may be used instead of base64, if the latter is not available. Since programs are not added or removed in the early userspace it should be impossible that an incompatible switch is made from encoding with base64 respectively uuencode to decoding with uudecode respectively base64.

Right now, the cryptsetup package forcibly includes busybox in initramfs images, so this dependency is already always fulfilled.

Signed-off-by: Christoph Anton Mitterer mail@christoph.anton.mitterer.name