owasp-amass/amass · error

error rewinding the file %s: %s

Error message

error rewinding the file %s: %s

What it means

After sniffing the first 512 bytes, getGzipReader rewinds the file with file.Seek(0, 0) so downstream readers see the whole file; this error wraps a failed Seek. Seek failure on a regular file is rare and typically means the path refers to something non-seekable (pipe, device, socket).

Source

Thrown at config/wordlist.go:128

	finfo, err := file.Stat()
	if err != nil {
		return nil, err
	}

	if finfo.Size() < 512 {
		return nil, errors.New("file cannot be checked for compression")
	}

	// We need to determine if this is a gzipped file or a plain text file, so we
	// first read the first 512 bytes to pass them down to http.DetectContentType
	// for mime detection. The file is rewinded before passing it along to the
	// next reader
	head := make([]byte, 512)
	if _, err = file.Read(head); err != nil {
		return nil, fmt.Errorf("error reading the first 512 bytes from %s: %s", absPath, err)
	}
	if _, err = file.Seek(0, 0); err != nil {
		return nil, fmt.Errorf("error rewinding the file %s: %s", absPath, err)
	}

	// Read the file as gzip if it's actually compressed
	if mt := http.DetectContentType(head); mt == "application/gzip" || mt == "application/x-gzip" {
		gzReader, err := gzip.NewReader(file)
		if err != nil {
			return nil, fmt.Errorf("error gz-reading the file %s: %v", absPath, err)
		}

		return gzReader, nil
	}

	return nil, fmt.Errorf("%s is not compressed", absPath)
}

func GetWordList(reader io.Reader) ([]string, error) {
	var words []string

View on GitHub (pinned to 79299dce87)

Solutions

1. Use a regular on-disk file for the wordlist, not a pipe or device
2. Materialize streamed input to a temp file first
3. Check filesystem support if using FUSE/network mounts

Example fix

// before
GetListFromFile("/dev/stdin")
// after
tmp, _ := os.CreateTemp("", "wl"); io.Copy(tmp, os.Stdin); tmp.Close()
GetListFromFile(tmp.Name())

info, err := os.Stat(path)
if err == nil && !info.Mode().IsRegular() { return errors.New("wordlist must be a seekable regular file") }

words, err := GetListFromFile(p)
if err != nil {
  if strings.HasPrefix(err.Error(), "error rewinding the file") {
    // copy input to a temp file and retry with the temp path
  }
  return err
}

When it happens

Trigger: file.Seek(0, 0) errors inside getGzipReader because the opened path is a FIFO, socket, or device file rather than a regular file.

Common situations: Pointing the wordlist setting at /dev/stdin, a named pipe, or a process substitution instead of a real file; network mounts with broken seek support.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• error opening the file %s: %v
• error reading the first 512 bytes from %s: %s
• the file is empty
• failed to get absolute path for wordlist file: %w
• unable to load the file in the bruteforce wordlist_file sett

AI-assisted analysis of owasp-amass/amass@79299dce87 (2026-09-06). Data as JSON: /api/errors/e704424d5f3630e6. Report an issue: GitHub.