add 'safeyaml' to cloudinit

In 0.7.0 we started using yaml.safe_load to load data rather than
yaml.load.  Some producers (namely, ubuntu MAAS created) have produced
cloud-config data in the past that included python unicode types.

This creates a specialized safe_loader that is basically safe_load +
support for python unicode.

2 files changed, 33 insertions, 1 deletions

diff --git a/cloudinit/safeyaml.py b/cloudinit/safeyaml.py
new file mode 100644
index 00000000..8b4da1fa
--- /dev/null
+++ b/cloudinit/safeyaml.py
@@ -0,0 +1,31 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Canonical Ltd.
+#
+#    Author: Scott Moser <scott.moser@canonical.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import yaml
+
+
+class _CustomSafeLoader(yaml.SafeLoader):
+    def construct_python_unicode(self, node):
+        return self.construct_scalar(node)
+
+_CustomSafeLoader.add_constructor(
+    u'tag:yaml.org,2002:python/unicode',
+    _CustomSafeLoader.construct_python_unicode)
+
+def load(blob):
+    return(yaml.load(blob, Loader=_CustomSafeLoader))
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 94b17dfa..46d490f7 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -50,6 +50,7 @@ import yaml
 
 from cloudinit import importer
 from cloudinit import log as logging
+from cloudinit import safeyaml
 from cloudinit import url_helper as uhelp
 
 from cloudinit.settings import (CFG_BUILTIN)
@@ -612,7 +613,7 @@ def load_yaml(blob, default=None, allowed=(dict,)):
         LOG.debug(("Attempting to load yaml from string "
                  "of length %s with allowed root types %s"),
                  len(blob), allowed)
-        converted = yaml.safe_load(blob)
+        converted = safeyaml.load(blob)
         if not isinstance(converted, allowed):
             # Yes this will just be caught, but thats ok for now...
             raise TypeError(("Yaml load allows %s root types,"