Be more safe on string/bytes when writing multipart user-data to disk.

When creating the multipart mime message that is written as
user-data.txt.i, cloud-init losing data on conversion to some things
as a string.

LP: #1768600

Author: Scott Moser <smoser@ubuntu.com>
Co-Authored-By: Chad Smith <chad.smith@canonical.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/tests/unittests/test_data.py b/tests/unittests/test_data.py
index 91d35cb8..3efe7adf 100644
--- a/tests/unittests/test_data.py
+++ b/tests/unittests/test_data.py
@@ -606,8 +606,10 @@ class TestUDProcess(helpers.ResourceUsingTestCase):
 
 
 class TestConvertString(helpers.TestCase):
+
     def test_handles_binary_non_utf8_decodable(self):
-        blob = b'\x32\x99'
+        """Printable unicode (not utf8-decodable) is safely converted."""
+        blob = b'#!/bin/bash\necho \xc3\x84\n'
         msg = ud.convert_string(blob)
         self.assertEqual(blob, msg.get_payload(decode=True))
 
@@ -621,6 +623,13 @@ class TestConvertString(helpers.TestCase):
         msg = ud.convert_string(text)
         self.assertEqual(text, msg.get_payload(decode=False))
 
+    def test_handle_mime_parts(self):
+        """Mime parts are properly returned as a mime message."""
+        message = MIMEBase("text", "plain")
+        message.set_payload("Just text")
+        msg = ud.convert_string(str(message))
+        self.assertEqual("Just text", msg.get_payload(decode=False))
+
 
 class TestFetchBaseConfig(helpers.TestCase):
     def test_only_builtin_gets_builtin(self):