feat: Use random filename suffixes for blobstorage (#4309)

Recently there was an accident with a chatbot that replaced its avatar set from the command line
with an unrelated avatar of a contact. Both the `selfavatar` setting and the contact avatar `i`
param pointed to `$BLOBDIR/avatar.png` at the time it was detected. How this happened is unclear,
but it is possible that `avatar.png` was removed, unmounted or otherwise not detected by the core,
and the core stored avatar received from the contact as `avatar.png`, while `selfavatar` config
still pointed to `$BLOBDIR/avatar.png`.

Such bugs are unavoidable even if the core itself has no bugs as we cannot rely on blobdir not
reside on the faulty network filesystem, being incorrectly backed up and restored etc., so we should
assume that files may be randomly removed. Then there may be dangling `$BLOBDIR/...` references in
the database which may accidentally point to unrelated files, could even be an `avatar.png` file
sent to the bot in private.

To prevent such bugs, we add random filename suffixes for the blobdir objects. Thanks to the added
Param::Filename these random suffixes aren't sent over the network.

python/src/deltachat/message.py

@@ -107,8 +107,8 @@ def set_html(self, html_text):
         lib.dc_msg_set_html(self._dc_msg, as_dc_charpointer(html_text))
 
     @props.with_doc
-    def filename(self):
-        """filename if there was an attachment, otherwise empty string."""
+    def file_path(self):
+        """file path if there was an attachment, otherwise empty string."""
         return from_dc_charpointer(lib.dc_msg_get_file(self._dc_msg))
 
     def set_file(self, path, mime_type=None):
@@ -119,9 +119,8 @@ def set_file(self, path, mime_type=None):
         lib.dc_msg_set_file(self._dc_msg, as_dc_charpointer(path), mtype)
 
     @props.with_doc
-    def basename(self) -> str:
-        """basename of the attachment if it exists, otherwise empty string."""
-        # FIXME, it does not return basename
+    def filename(self) -> str:
+        """filename of the attachment if any, otherwise empty string."""
         return from_dc_charpointer(lib.dc_msg_get_filename(self._dc_msg))
 
     @props.with_doc

python/tests/test_1_online.py

@@ -180,16 +180,16 @@ def send_and_receive_message():
 
     msg = send_and_receive_message()
     assert msg.text == "withfile"
-    assert open(msg.filename).read() == "some data"
-    msg.filename.index(basename)
-    assert msg.filename.endswith(ext)
+    assert open(msg.file_path).read() == "some data"
+    msg.file_path.index(basename)
+    assert msg.file_path.endswith(ext)
 
     msg2 = send_and_receive_message()
     assert msg2.text == "withfile"
-    assert open(msg2.filename).read() == "some data"
-    msg2.filename.index(basename)
-    assert msg2.filename.endswith(ext)
-    assert msg.filename != msg2.filename
+    assert open(msg2.file_path).read() == "some data"
+    msg2.file_path.index(basename)
+    assert msg2.file_path.endswith(ext)
+    assert msg.file_path != msg2.file_path
 
 
 def test_send_file_html_attachment(tmp_path, acfactory, lp):
@@ -213,9 +213,9 @@ def test_send_file_html_attachment(tmp_path, acfactory, lp):
     assert ev.data2 > dc.const.DC_CHAT_ID_LAST_SPECIAL
     msg = ac2.get_message_by_id(ev.data2)
 
-    assert open(msg.filename).read() == content
-    msg.filename.index(basename)
-    assert msg.filename.endswith(ext)
+    assert open(msg.file_path).read() == content
+    msg.file_path.index(basename)
+    assert msg.file_path.endswith(ext)
 
 
 def test_html_message(acfactory, lp):
@@ -309,7 +309,7 @@ def test_webxdc_message(acfactory, data, lp):
     msg1.set_file(data.get_path("webxdc/minimal.xdc"))
     msg1 = chat.send_msg(msg1)
     assert msg1.is_webxdc()
-    assert msg1.filename
+    assert msg1.file_path
 
     assert msg1.send_status_update({"payload": "test1"}, "some test data")
     assert msg1.send_status_update({"payload": "test2"}, "more test data")
@@ -322,7 +322,7 @@ def test_webxdc_message(acfactory, data, lp):
     msg2 = ac2._evtracker.wait_next_incoming_message()
     assert msg2.text == "message1"
     assert msg2.is_webxdc()
-    assert msg2.filename
+    assert msg2.file_path
     ac2._evtracker.get_info_contains("Marked messages [0-9]+ in folder INBOX as seen.")
     ac2.direct_imap.select_folder("Inbox")
     assert len(list(ac2.direct_imap.conn.fetch(AND(seen=True)))) == 1
@@ -337,7 +337,7 @@ def test_webxdc_huge_update(acfactory, data, lp):
     msg1.set_file(data.get_path("webxdc/minimal.xdc"))
     msg1 = chat.send_msg(msg1)
     assert msg1.is_webxdc()
-    assert msg1.filename
+    assert msg1.file_path
 
     msg2 = ac2._evtracker.wait_next_incoming_message()
     assert msg2.is_webxdc()
@@ -359,7 +359,7 @@ def test_webxdc_download_on_demand(acfactory, data, lp):
     msg1.set_file(data.get_path("webxdc/minimal.xdc"))
     msg1 = chat.send_msg(msg1)
     assert msg1.is_webxdc()
-    assert msg1.filename
+    assert msg1.file_path
 
     msg2 = ac2._evtracker.wait_next_incoming_message()
     assert msg2.is_webxdc()
@@ -1393,7 +1393,7 @@ def test_quote_attachment(tmp_path, acfactory, lp):
     received_reply = ac1._evtracker.wait_next_incoming_message()
     assert received_reply.text == "message reply"
     assert received_reply.quoted_text == received_message.text
-    assert open(received_reply.filename).read() == "data to send"
+    assert open(received_reply.file_path).read() == "data to send"
 
 
 def test_saved_mime_on_received_message(acfactory, lp):
@@ -1486,8 +1486,8 @@ def ac_outgoing_message(self, message):
     assert ev.data2 == msg_out.id
     msg_in = ac2.get_message_by_id(msg_out.id)
     assert msg_in.is_image()
-    assert os.path.exists(msg_in.filename)
-    assert os.stat(msg_in.filename).st_size == os.stat(path).st_size
+    assert os.path.exists(msg_in.file_path)
+    assert os.stat(msg_in.file_path).st_size == os.stat(path).st_size
     m = message_queue.get()
     assert m == msg_in
 
@@ -1520,7 +1520,7 @@ def assert_account_is_proper(ac):
         assert len(messages) == 3
         assert messages[0].text == "msg1"
         assert messages[1].filemime == "image/png"
-        assert os.stat(messages[1].filename).st_size == os.stat(original_image_path).st_size
+        assert os.stat(messages[1].file_path).st_size == os.stat(original_image_path).st_size
         ac.set_config("displayname", "new displayname")
         assert ac.get_config("displayname") == "new displayname"
 
@@ -1593,7 +1593,7 @@ def test_ac_setup_message(acfactory, lp):
     with pytest.raises(ValueError):
         msg.continue_key_transfer(str(reversed(setup_code)))
     lp.sec("try a good setup code")
-    print("*************** Incoming ASM File at: ", msg.filename)
+    print("*************** Incoming ASM File at: ", msg.file_path)
     print("*************** Setup Code: ", setup_code)
     msg.continue_key_transfer(setup_code)
     assert ac1.get_info()["fingerprint"] == ac2.get_info()["fingerprint"]

python/tests/test_2_increation.py

@@ -50,8 +50,8 @@ def test_no_increation_copies_to_blobdir(self, tmp_path, acfactory, lp):
         src = tmp_path / "file.txt"
         src.write_text("hello there\n")
         msg = chat.send_file(str(src))
-        assert msg.filename.startswith(os.path.join(ac1.get_blobdir(), "file"))
-        assert msg.filename.endswith(".txt")
+        assert msg.file_path.startswith(os.path.join(ac1.get_blobdir(), "file"))
+        assert msg.file_path.endswith(".txt")
 
     def test_forward_increation(self, acfactory, data, lp):
         ac1, ac2 = acfactory.get_online_accounts(2)
@@ -99,9 +99,9 @@ def test_forward_increation(self, acfactory, data, lp):
 
         lp.sec("wait1 for original or forwarded messages to arrive")
         received_original = ac2._evtracker.wait_next_incoming_message()
-        assert cmp(received_original.filename, orig, shallow=False)
+        assert cmp(received_original.file_path, orig, shallow=False)
 
         lp.sec("wait2 for original or forwarded messages to arrive")
         received_copy = ac2._evtracker.wait_next_incoming_message()
         assert received_copy.id != received_original.id
-        assert cmp(received_copy.filename, orig, shallow=False)
+        assert cmp(received_copy.file_path, orig, shallow=False)

python/tests/test_3_offline.py

@@ -440,31 +440,34 @@ def test_message_image(self, chat1, data, lp):
         assert msg.is_image()
         assert msg
         assert msg.id > 0
-        assert os.path.exists(msg.filename)
+        assert os.path.exists(msg.file_path)
         assert msg.filemime == "image/png"
 
     @pytest.mark.parametrize(
-        ("fn", "typein", "typeout"),
+        ("stem", "ext", "typein", "typeout"),
         [
-            ("r", None, "application/octet-stream"),
-            ("r.txt", None, "text/plain"),
-            ("r.txt", "text/plain", "text/plain"),
-            ("r.txt", "image/png", "image/png"),
+            ("r", "", None, "application/octet-stream"),
+            ("r", ".txt", None, "text/plain"),
+            ("r", ".txt", "text/plain", "text/plain"),
+            ("r", ".txt", "image/png", "image/png"),
         ],
     )
-    def test_message_file(self, chat1, data, lp, fn, typein, typeout):
+    def test_message_file(self, chat1, data, lp, stem, ext, typein, typeout):
         lp.sec("sending file")
+        fn = stem + ext
         fp = data.get_path(fn)
         msg = chat1.send_file(fp, typein)
         assert msg
         assert msg.id > 0
         assert msg.is_file()
-        assert os.path.exists(msg.filename)
-        assert msg.filename.endswith(msg.basename)
+        assert os.path.exists(msg.file_path)
+        assert msg.file_path.endswith(ext)
+        assert msg.filename == fn
         assert msg.filemime == typeout
         msg2 = chat1.send_file(fp, typein)
         assert msg2 != msg
-        assert msg2.filename != msg.filename
+        assert msg2.file_path != msg.file_path
+        assert msg2.filename == fn
 
     def test_create_contact(self, acfactory):
         ac1 = acfactory.get_pseudo_configured_account()
@@ -532,7 +535,7 @@ def test_import_export_on_unencrypted_acct(self, acfactory, tmp_path):
         messages = chat2.get_messages()
         assert len(messages) == 2
         assert messages[0].text == "msg1"
-        assert os.path.exists(messages[1].filename)
+        assert os.path.exists(messages[1].file_path)
 
     def test_import_export_on_encrypted_acct(self, acfactory, tmp_path):
         passphrase1 = "passphrase1"
@@ -570,7 +573,7 @@ def test_import_export_on_encrypted_acct(self, acfactory, tmp_path):
         messages = chat2.get_messages()
         assert len(messages) == 2
         assert messages[0].text == "msg1"
-        assert os.path.exists(messages[1].filename)
+        assert os.path.exists(messages[1].file_path)
 
         ac2.shutdown()
 
@@ -587,7 +590,7 @@ def test_import_export_on_encrypted_acct(self, acfactory, tmp_path):
         messages = chat2.get_messages()
         assert len(messages) == 2
         assert messages[0].text == "msg1"
-        assert os.path.exists(messages[1].filename)
+        assert os.path.exists(messages[1].file_path)
 
     def test_import_export_with_passphrase(self, acfactory, tmp_path):
         passphrase = "test_passphrase"
@@ -626,7 +629,7 @@ def test_import_export_with_passphrase(self, acfactory, tmp_path):
         messages = chat2.get_messages()
         assert len(messages) == 2
         assert messages[0].text == "msg1"
-        assert os.path.exists(messages[1].filename)
+        assert os.path.exists(messages[1].file_path)
 
     def test_import_encrypted_bak_into_encrypted_acct(self, acfactory, tmp_path):
         """
@@ -671,7 +674,7 @@ def test_import_encrypted_bak_into_encrypted_acct(self, acfactory, tmp_path):
         messages = chat2.get_messages()
         assert len(messages) == 2
         assert messages[0].text == "msg1"
-        assert os.path.exists(messages[1].filename)
+        assert os.path.exists(messages[1].file_path)
 
         ac2.shutdown()
 
@@ -688,7 +691,7 @@ def test_import_encrypted_bak_into_encrypted_acct(self, acfactory, tmp_path):
         messages = chat2.get_messages()
         assert len(messages) == 2
         assert messages[0].text == "msg1"
-        assert os.path.exists(messages[1].filename)
+        assert os.path.exists(messages[1].file_path)
 
     def test_set_get_draft(self, chat1):
         msg = Message.new_empty(chat1.account, "text")