Two secure-delete paths overwrote a sensitive file and then unlinked it,
but neither reliably forced the overwrite to stable storage. The
plaintext key export used a buffered stream with only a flush, and the
PIN vault removal opened a second descriptor to fsync only on non-
Windows. On a crash, or on Windows, the zeroing write could stay in the
OS cache and the original bytes could survive on disk.
Both now go through one shared best-effort secure-delete helper:
- It overwrites the file in place in chunks, never truncating first, so
the original blocks are the ones rewritten.
- It flushes the data to the device before unlinking (full fsync on
macOS, write-through on Windows), then removes the file.
- It is safe on a missing file and reports whether the file is gone.
This is still best-effort: SSD wear-levelling and copy-on-write or
journaling filesystems may retain copies.
Tests exercise the overwrite-and-remove helper.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
DanSandClaude Opus 4.8
2a535c844d