Any verification failure deleted the downloaded archive and forced a
full multi-GB re-download on the next attempt. But most failures are not
a corrupt archive: a missing or unreadable checksum sidecar, or a fetch
blip while pulling the checksum, would throw away a perfectly good file.
On top of that the checksum parser took the first token of whatever came
back, so an HTTP error page could be mistaken for a digest.
- The archive is now removed only on a genuine digest mismatch. A
missing sidecar, an unusable one, or a transient fetch error keeps the
file so the next attempt can reuse or resume it; the no-checksum case
still fails closed and keeps the archive.
- The checksum parser now accepts a token only if it is exactly the
expected length and all hex, lowercasing it; anything else (an error
page, a truncated or wrong-width digest) is rejected.
- The small-file fetch moved onto the shared capped HTTP helper, and MD5
is consulted only as a fallback when no SHA-256 is published.
Tests cover the checksum parser across good, wrong-length, non-hex, and
error-page inputs.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>