banger/internal/imagecat/catalog.go
Thales Maciel 3d9ae624b1
imagecat: catalog + fetch for banger image bundles
New package mirroring `kernelcat`: catalog + SHA256-verified HTTP
fetch of `.tar.zst` bundles that contain rootfs.ext4 + manifest.json.
Mounted empty (version:1, entries:[]) so nothing is pullable via the
bundle path yet; wiring into `banger image pull` lands in a later
phase.

- catalog.go: Catalog/CatEntry, LoadEmbedded, ParseCatalog, Lookup,
  ValidateName.
- fetch.go: Fetch(ctx, client, destDir, entry) downloads the bundle,
  verifies sha256, extracts exactly rootfs.ext4 and manifest.json
  into destDir, returns the parsed manifest. Rejects unexpected tar
  entries, unsafe paths, non-regular files, and cleans up partial
  writes on failure.
- Thirteen unit tests (happy path + every failure mode).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-17 15:11:52 -03:00

88 lines
2.8 KiB
Go

// Package imagecat is the published catalog of banger image bundles
// (rootfs.ext4 + manifest.json, packaged as a .tar.zst). It ships
// embedded in the banger binary. Downloading a bundle is the fast
// path for pulling a curated banger image — the rootfs is already
// flattened, ownership-fixed, and has banger's guest agents injected
// at build time.
//
// This package is the metadata + fetch layer. Writing to the banger
// image store is done by higher layers (the daemon's PullImage
// orchestrator), so imagecat has no local-storage concept of its own.
package imagecat
import (
_ "embed"
"encoding/json"
"fmt"
"os"
"regexp"
"strings"
)
//go:embed catalog.json
var embeddedCatalog []byte
// Catalog is the list of pullable image bundles compiled into this
// banger binary.
type Catalog struct {
Version int `json:"version"`
Entries []CatEntry `json:"entries"`
}
// CatEntry describes one downloadable bundle. TarballURL points at a
// .tar.zst containing rootfs.ext4 and manifest.json.
type CatEntry struct {
Name string `json:"name"`
Distro string `json:"distro,omitempty"`
Arch string `json:"arch,omitempty"`
KernelRef string `json:"kernel_ref,omitempty"` // kernelcat entry name to pair with
TarballURL string `json:"tarball_url"`
TarballSHA256 string `json:"tarball_sha256"`
SizeBytes int64 `json:"size_bytes,omitempty"`
Description string `json:"description,omitempty"`
}
// LoadEmbedded returns the catalog compiled into this banger binary.
func LoadEmbedded() (Catalog, error) {
return ParseCatalog(embeddedCatalog)
}
// ParseCatalog decodes a catalog.json payload. An empty payload is
// valid and yields a zero Catalog.
func ParseCatalog(data []byte) (Catalog, error) {
var cat Catalog
if len(data) == 0 {
return cat, nil
}
if err := json.Unmarshal(data, &cat); err != nil {
return Catalog{}, fmt.Errorf("parse catalog: %w", err)
}
return cat, nil
}
// Lookup returns the entry matching name, or os.ErrNotExist.
func (c Catalog) Lookup(name string) (CatEntry, error) {
for _, e := range c.Entries {
if e.Name == name {
return e, nil
}
}
return CatEntry{}, os.ErrNotExist
}
// namePattern accepts short filesystem-safe identifiers. Same rule as
// kernelcat so `--kernel-ref` and bundle-name refs share syntax.
var namePattern = regexp.MustCompile(`^[a-zA-Z0-9][a-zA-Z0-9._-]{0,63}$`)
// ValidateName returns an error unless name is a non-empty identifier
// of alphanumerics, dots, hyphens, and underscores, starting with an
// alphanumeric and at most 64 characters long.
func ValidateName(name string) error {
if strings.TrimSpace(name) == "" {
return fmt.Errorf("image name is required")
}
if !namePattern.MatchString(name) {
return fmt.Errorf("invalid image name %q: use alphanumerics, dots, hyphens, underscores (<=64 chars, starts with alphanumeric)", name)
}
return nil
}