109 lines
2.2 KiB
Go
109 lines
2.2 KiB
Go
package image
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import (
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"crypto/sha256"
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"encoding/hex"
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"errors"
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"fmt"
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"io"
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"net/http"
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"os"
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"os/exec"
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"path/filepath"
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"strings"
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)
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// Download fetches url into dest if dest does not exist.
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func Download(url, dest string) error {
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if _, err := os.Stat(dest); err == nil {
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return nil
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}
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if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
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return err
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}
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if strings.HasSuffix(url, ".xz") {
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tmp := dest + ".download.xz"
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if err := downloadRaw(url, tmp); err != nil {
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return err
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}
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defer os.Remove(tmp)
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return decompressXZ(tmp, dest)
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}
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return downloadRaw(url, dest)
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}
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func downloadRaw(url, dest string) error {
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if strings.HasPrefix(url, "file://") {
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src := strings.TrimPrefix(url, "file://")
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in, err := os.Open(src)
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if err != nil {
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return err
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}
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defer in.Close()
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out, err := os.Create(dest)
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if err != nil {
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return err
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}
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defer out.Close()
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_, err = io.Copy(out, in)
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return err
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}
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resp, err := http.Get(url)
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if err != nil {
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return err
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return fmt.Errorf("download failed: %s", resp.Status)
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}
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out, err := os.Create(dest)
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if err != nil {
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return err
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}
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defer out.Close()
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_, err = io.Copy(out, resp.Body)
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return err
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}
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func decompressXZ(src, dest string) error {
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out, err := os.Create(dest)
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if err != nil {
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return err
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}
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defer out.Close()
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cmd := exec.Command("xz", "-dc", src)
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cmd.Stdout = out
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var stderr strings.Builder
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cmd.Stderr = &stderr
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if err := cmd.Run(); err != nil {
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return fmt.Errorf("xz decompress %s: %w: %s", src, err, stderr.String())
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}
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return out.Sync()
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}
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// VerifyChecksum checks sha256 in the form "sha256:<hex>".
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func VerifyChecksum(path, checksum string) error {
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if checksum == "" {
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return nil
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}
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parts := strings.SplitN(checksum, ":", 2)
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if len(parts) != 2 || parts[0] != "sha256" {
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return errors.New("unsupported checksum format; use sha256:<hex>")
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}
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expected := strings.ToLower(parts[1])
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f, err := os.Open(path)
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if err != nil {
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return err
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}
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defer f.Close()
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h := sha256.New()
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if _, err := io.Copy(h, f); err != nil {
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return err
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}
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sum := hex.EncodeToString(h.Sum(nil))
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if sum != expected {
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return fmt.Errorf("checksum mismatch: expected %s got %s", expected, sum)
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}
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return nil
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}
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