Closes the v0.1.0 cosign requirement. Every banger update download
now goes through ECDSA-P256 verification before any binary is
trusted: SHA256SUMS.sig is fetched, base64-decoded, and verified
against the embedded BangerReleasePublicKey.
* BangerReleasePublicKey: PEM-encoded ECDSA public key embedded
at compile time. The current value is a sentinel PLACEHOLDER —
the maintainer must replace it with the output of
`cosign generate-key-pair`'s cosign.pub before cutting v0.1.0,
and re-cut. Until they do, every `banger update` refuses with
ErrSignatureRequired ("the maintainer must replace it and
re-cut a release before update can proceed"). Loud refusal
beats silent acceptance.
* VerifyBlobSignature: parses the embedded public key, base64-
decodes the signature, computes SHA256(body), runs ecdsa
.VerifyASN1. cosign sign-blob produces the format
VerifyASN1 verifies natively (ASN.1-DER encoded ECDSA over
a SHA256 digest), so no third-party crypto deps needed.
* FetchAndVerifySignature: pulls the signature URL from the
release manifest entry, fetches it (1 KiB cap), and verifies
against sumsBody. Refuses outright when sha256sums_sig_url is
empty — v0.1.0 contract requires every release to be signed,
and an unsigned release is a manifest publishing bug we'd
rather catch loudly than silently accept.
* Wired into banger update: sumsBody captured from
DownloadRelease, immediately fed into FetchAndVerifySignature.
A failed verification removes the staged tarball before
returning so it can't be reused.
* BangerReleasePublicKey is var (not const) only to support tests
that swap in a generated keypair; production sets it at compile
time and never mutates it.
Tests: placeholder-key path returns ErrSignatureRequired; happy
path with a fresh in-test ECDSA keypair verifies a real
sign-then-verify; tampered body, wrong key, and three malformed
signature shapes (not-base64, empty, garbage-DER) all reject.
Maintainer-cut workflow documented in BangerReleasePublicKey's
comment: cosign generate-key-pair → paste cosign.pub into the
constant → at release time, cosign sign-blob --key cosign.key
SHA256SUMS > SHA256SUMS.sig and publish.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The pure-logic core of `banger update`. No CLI yet; this commit
ships the steps the next commit's command will orchestrate.
* download.go — DownloadRelease fetches SHA256SUMS, parses it,
looks up the tarball's basename, then streams the tarball
through download.FetchVerified so the hash is checked on the
fly. Returns the SHA256SUMS bytes alongside so a future
cosign-verification step can validate them against an embedded
public key before trusting the hashes inside.
Also: fetchBounded for small bounded GETs (manifest, sums file,
future signature), DefaultStagingDir, EnsureStagingDir,
PrepareCleanStaging.
* stage.go — StageTarball reads gzip+tar, validates the entry
set is exactly {banger, bangerd, banger-vsock-agent} (no
extras, no missing, no path traversal, no non-regular files),
extracts at mode 0755 regardless of what the tarball claims.
StagedRelease records the resulting paths.
* swap.go — InstallTargets pins the canonical install paths
(/usr/local/bin/banger, /usr/local/bin/bangerd,
/usr/local/lib/banger/banger-vsock-agent). Swap orders the
three replacements vsock → bangerd → banger so the most
impactful binary (the CLI) goes last; each step uses
system.AtomicReplace and accumulates a SwapResult so partial
failures can be rolled back cleanly. Rollback unwinds in
reverse, joining errors so a half-rolled-back state surfaces
enough info for an operator to fix manually. CleanupBackups
removes the .previous trail after `banger doctor` confirms
the new install is healthy.
* installmeta.UpdateBuildInfo — small helper that refreshes
Version/Commit/BuiltAt on /etc/banger/install.toml without
re-running the full system install. Preserves OwnerUser/UID/
GID/Home and the original InstalledAt timestamp.
Tests: stage rejects extra entries / missing entries / path
traversal / non-regular files; happy-path stages all three at 0755
with correct contents. Swap+Rollback covers the all-three-succeed
path (then verifies .previous backups exist + rollback restores
old contents) AND the partial-failure path (third swap blocked by
a non-dir parent → SwappedTargets = 2 → rollback unwinds those
two cleanly). DownloadRelease covers happy path, tarball-not-in-
SHA256SUMS, and propagated sha256 mismatch.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
First slice of the `banger update` package. No CLI yet — this just
defines the wire shape and parsers the rest of the flow will plug
into.
* internal/updater/manifest.go — Manifest / Release types,
ManifestSchemaVersion = 1, the hardcoded URL
https://releases.thaloco.com/banger/manifest.json (var instead
of const so tests can point at httptest), and FetchManifest /
ParseManifest / Manifest.LookupRelease / Manifest.Latest.
The manifest only references URLs (tarball, SHA256SUMS, optional
signature); actual binary hashes come from SHA256SUMS itself,
so manifest tampering can't substitute a hash for a known-good
tarball.
SchemaVersion gates forward-compat: a CLI that doesn't know its
server's schema_version refuses to update rather than guessing.
* internal/updater/sha256sums.go — ParseSHA256Sums tolerates both
GNU `<digest> <file>` (with optional `*` binary prefix) and
BSD `SHA256 (file) = <digest>` formats. Comments and blank
lines are skipped; malformed lines that LOOK like entries are
rejected (silent skipping is the wrong failure mode for a
security-relevant input). Digests are lowercased so the caller
can `==`-compare without worrying about case.
Caps: 1 MiB on the manifest body, 16 KiB on SHA256SUMS, 256 MiB on
release tarballs. Generous-but-bounded; bumping requires a code
change so a server-side mistake can't fill the disk.
Tests: ParseManifest happy path, schema-version-too-new rejection,
five malformed-input cases. ParseSHA256Sums covers GNU + BSD +
star-prefix + comments-and-blanks, six malformed-input rejections,
case-insensitive digest normalisation. FetchManifest end-to-end via
httptest.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
