test md5 hash on dataset download

Author: mfeurer

openml/datasets/functions.py

@@ -1,4 +1,5 @@
 from collections import OrderedDict
+import hashlib
 import io
 import os
 import re
@@ -365,6 +366,8 @@ def _get_dataset_arff(did_cache_dir, description):
         Location of arff file.
     """
     output_file_path = os.path.join(did_cache_dir, "dataset.arff")
+    md5_checksum_fixture = description.get("oml:md5_checksum")
+    did = description.get("oml:id")
 
     # This means the file is still there; whether it is useful is up to
     # the user and not checked by the program.
@@ -377,6 +380,14 @@ def _get_dataset_arff(did_cache_dir, description):
 
     url = description['oml:url']
     arff_string = _read_url(url)
+    md5 = hashlib.md5()
+    md5.update(arff_string.encode('utf8'))
+    md5_checksum = md5.hexdigest()
+    if md5_checksum != md5_checksum_fixture:
+        raise ValueError(
+            'Checksum %s of downloaded dataset %d is unequal to the checksum '
+            '%s sent by the server.' % (md5_checksum, did, md5_checksum_fixture)
+        )
 
     with io.open(output_file_path, "w", encoding='utf8') as fh:
         fh.write(arff_string)

tests/test_datasets/test_dataset_functions.py

@@ -200,6 +200,20 @@ def test__getarff_path_dataset_arff(self):
         self.assertIsInstance(arff_path, str)
         self.assertTrue(os.path.exists(arff_path))
 
+    def test__getarff_md5_issue(self):
+        description = {
+            'oml:id': 5,
+            'oml:md5_checksum': 'abc',
+            'oml:url': 'https://www.openml.org/data/download/61',
+        }
+        self.assertRaisesRegexp(
+            ValueError,
+            'Checksum ad484452702105cbf3d30f8deaba39a9 of downloaded dataset 5 '
+            'is unequal to the checksum abc sent by the server.',
+            _get_dataset_arff,
+            self.workdir, description,
+        )
+
     def test__get_dataset_features(self):
         features = _get_dataset_features(self.workdir, 2)
         self.assertIsInstance(features, dict)