Let Oid enforce positive decimal integers (#5053)

Failing that would lead to an OpenSSL error when calling OBJ_txt2obj at
serialization.

Adds basic tests for oids.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/cryptography/hazmat/_oid.py b/src/cryptography/hazmat/_oid.py
index 4b08722f..f98912f9 100644
--- a/src/cryptography/hazmat/_oid.py
+++ b/src/cryptography/hazmat/_oid.py
@@ -19,11 +19,16 @@ class ObjectIdentifier(object):
         # range 0..39.  All nodes must be integers.
         for node in nodes:
             try:
-                intnodes.append(int(node, 0))
+                node_value = int(node, 10)
             except ValueError:
                 raise ValueError(
                     "Malformed OID: %s (non-integer nodes)" % (
                         self._dotted_string))
+            if node_value < 0:
+                raise ValueError(
+                    "Malformed OID: %s (negative-integer nodes)" % (
+                        self._dotted_string))
+            intnodes.append(node_value)
 
         if len(nodes) < 2:
             raise ValueError(