Use TargetFile.verify_length_and_hashes in ngclient

Replace Updater._check_file_lenght and Updater._check_hashes_obj
with TargetFile.verify_length_and_hashes.

Signed-off-by: Teodora Sechkova <tsechkova@vmware.com>

tuf/ngclient/updater.py

@@ -202,17 +202,21 @@ def download_target(
  else:
  target_base_url = _ensure_trailing_slash(target_base_url)
 
- full_url = parse.urljoin(target_base_url, targetinfo["filepath"])
+ target_filepath = targetinfo["filepath"]
+ target_fileinfo = targetinfo["fileinfo"]
+ full_url = parse.urljoin(target_base_url, target_filepath)
 
  with download.download_file(
- full_url, targetinfo["fileinfo"].length, self._fetcher
+ full_url, target_fileinfo.length, self._fetcher
  ) as target_file:
- _check_file_length(target_file, targetinfo["fileinfo"].length)
- _check_hashes_obj(target_file, targetinfo["fileinfo"].hashes)
+ try:
+ target_fileinfo.verify_length_and_hashes(target_file)
+ except exceptions.LengthOrHashMismatchError as e:
+ raise exceptions.RepositoryError(
+ f"{target_filepath} length or hashes do not match"
+ ) from e
 
- filepath = os.path.join(
- destination_directory, targetinfo["filepath"]
- )
+ filepath = os.path.join(destination_directory, target_filepath)
  sslib_util.persist_temp_file(target_file, filepath)
 
  def _download_metadata(
@@ -518,47 +522,6 @@ def _visit_child_role(child_role: Dict, target_filepath: str) -> str:
  return None
 
 
-def _check_file_length(file_object, trusted_file_length):
- """
- Given a file_object, checks whether its length matches
- trusted_file_length.
-
- Raises:
- DownloadLengthMismatchError: File length does not match
- expected length.
- """
- file_object.seek(0, 2)
- observed_length = file_object.tell()
- file_object.seek(0)
-
- if observed_length != trusted_file_length:
- raise exceptions.DownloadLengthMismatchError(
- trusted_file_length, observed_length
- )
-
-
-def _check_hashes_obj(file_object, trusted_hashes):
- """
- Given a file_object, checks whether its hash matches
- trusted_hashes.
-
- Raises:
- BadHashError: Hashes do not match
- """
- for algorithm, trusted_hash in trusted_hashes.items():
- digest_object = sslib_hash.digest_fileobject(file_object, algorithm)
-
- computed_hash = digest_object.hexdigest()
-
- # Raise an exception if any of the hashes are incorrect.
- if trusted_hash != computed_hash:
- raise exceptions.BadHashError(trusted_hash, computed_hash)
-
- logger.info(
- "The file's " + algorithm + " hash is" " correct: " + trusted_hash
- )
-
-
 def _get_filepath_hash(target_filepath, hash_function="sha256"):
  """
  Calculate the hash of the filepath to determine which bin to find the