Set a sane umask to create a proper snap

snapcraft/main.py

@@ -62,6 +62,7 @@
 """
 
 import logging
+import os
 import pkg_resources
 import sys
 import textwrap
@@ -102,6 +103,13 @@ def _get_version():
         return 'devel'
 
 
+def _get_umask():
+    shell_umask = os.umask(0)
+    os.umask(shell_umask)
+
+    return shell_umask
+
+
 def main():
     args = docopt(__doc__, version=_get_version(), options_first=True)
 
@@ -126,6 +134,11 @@ def main():
 
         sys.exit(textwrap.fill(str(e)))
 
+    umask = _get_umask()
+    if umask != 0o0022 and umask != 0o0002:
+        logger.warning('Umask is set to {:04o}. Some files may not be '
+                       'accessible from your resulting snap'.format(umask))
+
 
 if __name__ == '__main__':  # pragma: no cover
     main()                  # pragma: no cover

snapcraft/tests/test_main.py

@@ -20,6 +20,8 @@
 import pkg_resources
 import sys
 
+import fixtures
+
 import snapcraft.main
 import snapcraft.common
 
@@ -158,3 +160,25 @@ def test_devel_version(self, mock_stdout, mock_resources):
             snapcraft.main.main()
 
         self.assertEqual(mock_stdout.getvalue(), 'devel\n')
+
+    @mock.patch('os.umask')
+    @mock.patch('snapcraft.main.docopt')
+    def test_warn_umask(self, mock_docopt, mock_umask):
+        fake_logger = fixtures.FakeLogger(level=logging.WARNING)
+        self.useFixture(fake_logger)
+
+        mock_docopt.return_value = {
+            'COMMAND': 'help',
+            '--debug': False,
+            '--no-parallel-build': False,
+            'ARGS': [],
+        }
+
+        mock_umask.return_value = 0o007
+
+        with mock.patch('snapcraft.commands.help.main'):
+            snapcraft.main.main()
+
+        self.assertEqual('Umask is set to 0007. Some files may not be '
+                         'accessible from your resulting snap\n',
+                         fake_logger.output)