Integrity + defence-in-depth for the in-app updater:
- Require and verify a SHA-256 checksum before running an installer. Each
release must attach `<installer>.sha256`; downloadAppUpdate fetches it from
the host-pinned origin (deriving the URL itself, not trusting the renderer),
hashes the stream as it writes, and refuses to run on mismatch/missing/
unparseable. Fails closed. NB: same-host hash is integrity, not protection
against a fully compromised host — only Authenticode signing covers that.
- fetchTrustedText helper GETs the checksum with the same per-hop host
re-validation as the installer download, plus a size cap and timeout.
- finish() is now the single teardown point and aborts the request on failure,
so a write error can't leave Electron pulling bytes into a dead stream;
removed three now-redundant explicit abort() calls.
- Clear the idle/stall timer once the body is fully received.
- Export isTrustedDownloadUrl/compareVersions, extract extractSha256, and add
14 unit tests (host pin incl. userinfo spoof + wrong port, checksum parsing
incl. sha512 non-slice, prerelease never outranking its release).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
debont80
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