| 1 | package release |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "crypto/sha256" |
| 6 | "encoding/hex" |
| 7 | "errors" |
| 8 | "fmt" |
| 9 | "io" |
| 10 | "os" |
| 11 | |
| 12 | "github.com/carlosframework/platform/internal/safefile" |
| 13 | ) |
| 14 | |
| 15 | // ErrTooLarge: the object exceeded the caller's limit. The reader is cut at |
| 16 | // limit+1 bytes, so an object EXACTLY at the limit is told from one over it. |
| 17 | var ErrTooLarge = errors.New("store: object larger than the caller's limit") |
| 18 | |
| 19 | // FetchToFile streams key into dst with a running sha256, never holding the |
| 20 | // object in memory: temp file, fsync, rename, directory fsync. Any failure |
| 21 | // removes the temp and leaves dst untouched. |
| 22 | func FetchToFile(ctx context.Context, s Store, key, dst string, limit int64, wantSHA256 string) (err error) { |
| 23 | rc, _, err := OpenObject(ctx, s, key) |
| 24 | if err != nil { |
| 25 | return err |
| 26 | } |
| 27 | defer rc.Close() |
| 28 | return safefile.Write(dst, 0o600, func(f io.Writer) error { |
| 29 | h := sha256.New() |
| 30 | n, err := io.Copy(io.MultiWriter(f, h), io.LimitReader(rc, limit+1)) |
| 31 | if err != nil { |
| 32 | return fmt.Errorf("fetch %s: %w", key, err) |
| 33 | } |
| 34 | if n > limit { |
| 35 | return fmt.Errorf("fetch %s: %w (limit %d)", key, ErrTooLarge, limit) |
| 36 | } |
| 37 | if got := hex.EncodeToString(h.Sum(nil)); got != wantSHA256 { |
| 38 | return fmt.Errorf("fetch %s: sha256 %s does not match the signed %s", key, got, wantSHA256) |
| 39 | } |
| 40 | return nil |
| 41 | }) |
| 42 | } |
| 43 | |
| 44 | // syncDir makes a rename durable: the directory entry is what fsync(file) |
| 45 | // does not cover. |
| 46 | func syncDir(dir string) error { |
| 47 | d, err := os.Open(dir) |
| 48 | if err != nil { |
| 49 | return err |
| 50 | } |
| 51 | defer d.Close() |
| 52 | return d.Sync() |
| 53 | } |
| 54 | |
amadan