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package stream
import (
"crypto/sha256"
"fmt"
"io"
"net/http"
"net/url"
"os"
"path"
"path/filepath"
)
// Fetch an artifact, validating its checksum. If applicable,
// the artifact will not be decompressed. Does not
// validate GPG signature.
func (a *Artifact) Fetch(w io.Writer) error {
resp, err := http.Get(a.Location)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("%s returned status: %s", a.Location, resp.Status)
}
hasher := sha256.New()
reader := io.TeeReader(resp.Body, hasher)
_, err = io.Copy(w, reader)
if err != nil {
return err
}
// Validate sha256 checksum
foundChecksum := fmt.Sprintf("%x", hasher.Sum(nil))
if a.Sha256 != foundChecksum {
return fmt.Errorf("checksum mismatch for %s; expected=%s found=%s", a.Location, a.Sha256, foundChecksum)
}
return nil
}
// Name returns the "basename" of the artifact, i.e. the contents
// after the last `/`. This can be useful when downloading to a file.
func (a *Artifact) Name() (string, error) {
loc, err := url.Parse(a.Location)
if err != nil {
return "", fmt.Errorf("failed to parse artifact url: %w", err)
}
// Note this one uses `path` since even on Windows URLs have forward slashes.
return path.Base(loc.Path), nil
}
// Download fetches the specified artifact and saves it to the target
// directory. The full file path will be returned as a string.
// If the target file path exists, it will be overwritten.
// If the download fails, the temporary file will be deleted.
func (a *Artifact) Download(destdir string) (string, error) {
name, err := a.Name()
if err != nil {
return "", err
}
destfile := filepath.Join(destdir, name)
w, err := os.CreateTemp(destdir, ".coreos-artifact-")
if err != nil {
return "", err
}
finalized := false
defer func() {
if !finalized {
// Ignore an error to unlink
_ = os.Remove(w.Name())
}
}()
if err := a.Fetch(w); err != nil {
return "", err
}
if err := w.Sync(); err != nil {
return "", err
}
if err := w.Chmod(0644); err != nil {
return "", err
}
if err := w.Close(); err != nil {
return "", err
}
if err := os.Rename(w.Name(), destfile); err != nil {
return "", err
}
finalized = true
return destfile, nil
}
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