Read --key-file input in a loop until EOF or until the 33-byte rejection
threshold is reached. A single read call is enough for ordinary regular files
in practice, but FIFOs and process substitution can legally return fewer than
32 bytes before EOF. Treating that first short read as final made the new
key-file path fail spuriously for exactly the shell-friendly usage it was meant
to support.
Keep the existing exact-length policy: 32 bytes is accepted, shorter files are
rejected, and 33 or more bytes are rejected with the trailing-newline hint.
The intermediate buffer remains zeroizing.
Test Plan:
- cargo test split_fifo_key_file_read_roundtrips
- cargo fmt --check
- cargo clippy --all-targets -- -D warnings
- cargo test
- git diff --check
Refs: review finding for --key-file short reads
ddidderr
725d33939e
