feat: use cryptographically secure random for new document ids (#1162)

Author: probicheaux

packages/google-cloud-firestore/google/cloud/firestore_v1/base_collection.py

@@ -60,6 +60,7 @@
 importdatetime
 
 _AUTO_ID_CHARS="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+system_random=random.SystemRandom()
 
 
 classBaseCollectionReference(Generic[QueryType]):
@@ -623,8 +624,11 @@ def _auto_id() -> str:
  str: A 20 character string composed of digits, uppercase and
  lowercase and letters.
  """
-
-return"".join(random.choice(_AUTO_ID_CHARS) for_inrange(20))
+try:
+return"".join(system_random.choice(_AUTO_ID_CHARS) for_inrange(20))
+# Very old Unix systems don't have os.urandom (/dev/urandom), in which case use random.choice
+exceptNotImplementedError:
+return"".join(random.choice(_AUTO_ID_CHARS) for_inrange(20))
 
 
 def_item_to_document_ref(collection_reference, item):

packages/google-cloud-firestore/tests/unit/v1/test_base_collection.py

@@ -437,7 +437,7 @@ def test_basecollectionreference_pipeline(mock_query):
 assertpipeline==mock_query._build_pipeline.return_value
 
 
-@mock.patch("random.choice")
+@mock.patch("random.SystemRandom.choice")
 deftest__auto_id(mock_rand_choice):
 fromgoogle.cloud.firestore_v1.base_collectionimport_AUTO_ID_CHARS, _auto_id
 
@@ -450,6 +450,21 @@ def test__auto_id(mock_rand_choice):
 assertmock_rand_choice.mock_calls==mock_calls
 
 
+@mock.patch("random.choice")
+@mock.patch("random.SystemRandom.choice")
+deftest__auto_id_fallback_to_random(mock_system_rand_choice, mock_rand_choice):
+fromgoogle.cloud.firestore_v1.base_collectionimport_AUTO_ID_CHARS, _auto_id
+
+mock_system_rand_choice.side_effect=NotImplementedError
+mock_result="0123456789abcdefghij"
+mock_rand_choice.side_effect=list(mock_result)
+result=_auto_id()
+assertresult==mock_result
+
+mock_calls= [mock.call(_AUTO_ID_CHARS)] *20
+assertmock_rand_choice.mock_calls==mock_calls
+
+
 def_make_credentials():
 importgoogle.auth.credentials