cfix: Fallback to PRECIS for localpart and resourcepart

Instead of enforcing stringprep or precis, try stringprep and fallback
to precis otherwise.

3 files changed, 35 insertions, 15 deletions

diff --git a/nbxmpp/precis.py b/nbxmpp/precis.py
new file mode 100644
index 0000000..a910205
--- /dev/null
+++ b/nbxmpp/precis.py
@@ -0,0 +1,19 @@
+
+
+from precis_i18n import get_profile
+
+
+_localpart_disallowed_chars = set('"&\'/:<>@')
+
+
+def enforce_precis_username(localpart: str) -> str:
+    if _localpart_disallowed_chars & set(localpart):
+        raise ValueError('Input contains prohibited codepoint: %s' % localpart)
+
+    username = get_profile('UsernameCaseMapped')
+    return username.enforce(localpart)
+
+
+def enforce_precis_opaque(resourcepart: str) -> str:
+    opaque = get_profile('OpaqueString')
+    return opaque.enforce(resourcepart)
diff --git a/nbxmpp/protocol.py b/nbxmpp/protocol.py
index 0b86015..704530a 100644
--- a/nbxmpp/protocol.py
+++ b/nbxmpp/protocol.py
@@ -37,11 +37,12 @@ from dataclasses import asdict
 from gi.repository import GLib
 
 import idna
-from precis_i18n import get_profile
 from nbxmpp.simplexml import Node
 from nbxmpp.namespaces import Namespace
 from nbxmpp.stringprep import nodeprep
 from nbxmpp.stringprep import resourceprep
+from nbxmpp.precis import enforce_precis_username
+from nbxmpp.precis import enforce_precis_opaque
 
 
 def ascii_upper(s):
@@ -256,7 +257,6 @@ _errorcodes = {
 }
 
 
-_localpart_disallowed_chars = set('"&\'/:<>@')
 _localpart_escape_chars = ' "&\'/:<>@'
 
 
@@ -487,18 +487,17 @@ def validate_localpart(localpart: str) -> str:
     if not localpart or len(localpart.encode()) > 1023:
         raise LocalpartByteLimit
 
-    if os.environ.get('NBXMPP_USE_PRECIS') is None:
+    if os.environ.get('NBXMPP_ENFORCE_PRECIS') is None:
         try:
             return nodeprep(localpart)
         except Exception:
-            raise LocalpartNotAllowedChar
-
-    if _localpart_disallowed_chars & set(localpart):
-        raise LocalpartNotAllowedChar
+            try:
+                return enforce_precis_username(localpart)
+            except Exception:
+                raise LocalpartNotAllowedChar
 
     try:
-        username = get_profile('UsernameCaseMapped')
-        return username.enforce(localpart)
+        return enforce_precis_username(localpart)
     except Exception:
         raise LocalpartNotAllowedChar
 
@@ -508,15 +507,17 @@ def validate_resourcepart(resourcepart: str) -> str:
     if not resourcepart or len(resourcepart.encode()) > 1023:
         raise ResourcepartByteLimit
 
-    if os.environ.get('NBXMPP_USE_PRECIS') is None:
+    if os.environ.get('NBXMPP_ENFORCE_PRECIS') is None:
         try:
             return resourceprep(resourcepart)
         except Exception:
-            raise ResourcepartNotAllowedChar
+            try:
+                return enforce_precis_opaque(resourcepart)
+            except Exception:
+                raise ResourcepartNotAllowedChar
 
     try:
-        opaque = get_profile('OpaqueString')
-        return opaque.enforce(resourcepart)
+        return enforce_precis_opaque(resourcepart)
     except Exception:
         raise ResourcepartNotAllowedChar
 
diff --git a/test/unit/test_jid_parsing.py b/test/unit/test_jid_parsing.py
index 374c942..a91c667 100644
--- a/test/unit/test_jid_parsing.py
+++ b/test/unit/test_jid_parsing.py
@@ -51,7 +51,7 @@ class JIDParsing(unittest.TestCase):
                 JID.from_string(jid)
 
     def test_invalid_precis_jids(self):
-        os.environ['NBXMPP_USE_PRECIS'] = 'true'
+        os.environ['NBXMPP_ENFORCE_PRECIS'] = 'true'
         tests = [
             ('henry\U00002163@example.com', LocalpartNotAllowedChar),
             ('\U0000265A@example.com', LocalpartNotAllowedChar),
@@ -61,7 +61,7 @@ class JIDParsing(unittest.TestCase):
             with self.assertRaises(exception):
                 JID.from_string(jid)
 
-        del os.environ['NBXMPP_USE_PRECIS']
+        del os.environ['NBXMPP_ENFORCE_PRECIS']
 
     def test_ip_literals(self):
         tests = [