refactor validating handles in ATProto and elsewhere

for https://github.com/snarfed/bridgy-fed/issues/982

activitypub.py

@@ -158,7 +158,7 @@ class ActivityPub(User, Protocol):
         return False
 
     @classmethod
-    def owns_handle(cls, handle):
+    def owns_handle(cls, handle, allow_internal=False):
         """Returns True if handle is a WebFinger ``@-@`` handle, False otherwise.
 
         Example: ``@user@instance.com``. The leading ``@`` is optional.
@@ -171,7 +171,8 @@ class ActivityPub(User, Protocol):
             return False
 
         user, domain = parts
-        return user and domain and not cls.is_blocklisted(domain)
+        return user and domain and not cls.is_blocklisted(
+            domain, allow_internal=allow_internal)
 
     @classmethod
     def handle_to_id(cls, handle):

atproto.py

@@ -128,8 +128,9 @@ class ATProto(User, Protocol):
                 or id.startswith('https://bsky.app/'))
 
     @classmethod
-    def owns_handle(cls, handle):
-        if not re.match(DOMAIN_RE, handle):
+    def owns_handle(cls, handle, allow_internal=False):
+        # TODO: implement allow_internal
+        if not did.HANDLE_RE.fullmatch(handle):
             return False
 
     @classmethod
@@ -248,6 +249,10 @@ class ATProto(User, Protocol):
 
         Args:
           user (models.User)
+
+        Raises:
+          ValueError: if the user's handle is invalid, eg begins or ends with an
+            underscore or dash
         """
         assert not isinstance(user, ATProto)
 

ids.py

@@ -6,7 +6,6 @@ import logging
 import re
 from urllib.parse import urljoin, urlparse
 
-from arroba import did
 from flask import request
 from google.cloud.ndb.query import FilterNode, Query
 from granary.bluesky import BSKY_APP_URL_RE, web_url_to_at_uri
@@ -162,50 +161,57 @@ def translate_handle(*, handle, from_, to, enhanced):
 
     Returns:
       str: the corresponding handle in ``to``
+
+    Raises:
+      ValueError: if the user's handle is invalid, eg begins or ends with an
+        underscore or dash
     """
     assert handle and from_ and to, (handle, from_, to)
-    assert from_.owns_handle(handle) is not False or from_.LABEL == 'ui'
-
-    if from_.LABEL == 'atproto':
-        assert did.HANDLE_RE.fullmatch(handle)
+    if not from_.LABEL == 'ui':
+        if from_.owns_handle(handle, allow_internal=True) is False:
+            raise ValueError(f'input handle {handle} is not valid for {from_.LABEL}')
 
     if from_ == to:
         return handle
 
+    output = None
     match from_.LABEL, to.LABEL:
         case _, 'activitypub':
             domain = f'{from_.ABBREV}{SUPERDOMAIN}'
             if enhanced or handle == PRIMARY_DOMAIN or handle in PROTOCOL_DOMAINS:
                 domain = handle
-            return f'@{handle}@{domain}'
+            output = f'@{handle}@{domain}'
 
         case _, 'atproto':
+            output = handle.lstrip('@').replace('@', '.')
             for from_char in ATPROTO_DASH_CHARS:
-                handle = handle.replace(from_char, '-')
+                output = output.replace(from_char, '-')
 
-            handle = handle.lstrip('@').replace('@', '.')
             if enhanced or handle == PRIMARY_DOMAIN or handle in PROTOCOL_DOMAINS:
                 pass
             else:
-                handle = f'{handle}.{from_.ABBREV}{SUPERDOMAIN}'
-
-            assert did.HANDLE_RE.fullmatch(handle)
-            return handle
+                output = f'{output}.{from_.ABBREV}{SUPERDOMAIN}'
 
         case 'activitypub', 'web':
             user, instance = handle.lstrip('@').split('@')
             # TODO: get this from the actor object's url field?
-            return (f'https://{user}' if user == instance
+            output = (f'https://{user}' if user == instance
                     else f'https://{instance}/@{user}')
 
         case _, 'web':
-            return handle
+            output = handle
 
         # only for unit tests
         case _, 'fake' | 'other' | 'eefake':
-            return f'{to.LABEL}:handle:{handle}'
+            output = f'{to.LABEL}:handle:{handle}'
 
-    assert False, (handle, from_.LABEL, to.LABEL)
+    assert output, (handle, from_.LABEL, to.LABEL)
+    # don't check Web handles because they're sometimes URLs, eg
+    # @user@instance => https://instance/@user
+    if to.LABEL != 'web' and to.owns_handle(output, allow_internal=True) is False:
+        raise ValueError(f'translated handle {output} is not valid for {to.LABEL}')
+
+    return output
 
 
 def translate_object_id(*, id, from_, to):

protocol.py

@@ -172,7 +172,7 @@ class Protocol:
         return False
 
     @classmethod
-    def owns_handle(cls, handle):
+    def owns_handle(cls, handle, allow_internal=False):
         """Returns whether this protocol owns the handle, or None if it's unclear.
 
         To be implemented by subclasses.
@@ -192,6 +192,8 @@ class Protocol:
 
         Args:
           handle (str)
+          allow_internal (bool): whether to return False for internal domains
+            like ``fed.brid.gy``, ``bsky.brid.gy``, etc
 
         Returns:
           bool or None
@@ -409,6 +411,9 @@ class Protocol:
         Args:
           user (models.User): original source user. Shouldn't already have a
             copy user for this protocol in :attr:`copies`.
+
+        Raises:
+          ValueError: if we can't create a copy of the given user in this protocol
         """
         raise NotImplementedError()
 

tests/test_atproto.py

@@ -109,9 +109,9 @@ class ATProtoTest(TestCase):
         self.assertEqual('han.dull', user.key.get().handle)
 
     def test_owns_id(self):
-        self.assertEqual(False, ATProto.owns_id('http://foo'))
-        self.assertEqual(False, ATProto.owns_id('https://bar.baz/biff'))
-        self.assertEqual(False, ATProto.owns_id('e45fab982'))
+        self.assertFalse(ATProto.owns_id('http://foo'))
+        self.assertFalse(ATProto.owns_id('https://bar.baz/biff'))
+        self.assertFalse(ATProto.owns_id('e45fab982'))
 
         self.assertTrue(ATProto.owns_id('at://did:plc:user/bar/123'))
         self.assertTrue(ATProto.owns_id('did:plc:user'))
@@ -123,12 +123,18 @@ class ATProtoTest(TestCase):
         self.assertIsNone(ATProto.owns_handle('foo.com'))
         self.assertIsNone(ATProto.owns_handle('foo.bar.com'))
 
-        self.assertEqual(False, ATProto.owns_handle('foo'))
-        self.assertEqual(False, ATProto.owns_handle('@foo'))
-        self.assertEqual(False, ATProto.owns_handle('@foo.com'))
-        self.assertEqual(False, ATProto.owns_handle('@foo@bar.com'))
-        self.assertEqual(False, ATProto.owns_handle('foo@bar.com'))
-        self.assertEqual(False, ATProto.owns_handle('localhost'))
+        self.assertFalse(ATProto.owns_handle('foo'))
+        self.assertFalse(ATProto.owns_handle('@foo'))
+        self.assertFalse(ATProto.owns_handle('@foo.com'))
+        self.assertFalse(ATProto.owns_handle('@foo@bar.com'))
+        self.assertFalse(ATProto.owns_handle('foo@bar.com'))
+        self.assertFalse(ATProto.owns_handle('localhost'))
+
+        self.assertFalse(ATProto.owns_handle('_foo.com'))
+        self.assertFalse(ATProto.owns_handle('-foo.com'))
+        self.assertFalse(ATProto.owns_handle('foo_.com'))
+        self.assertFalse(ATProto.owns_handle('foo-.com'))
+
         # TODO: this should be False
         self.assertIsNone(ATProto.owns_handle('web.brid.gy'))
 
@@ -701,6 +707,12 @@ class ATProtoTest(TestCase):
 
         mock_create_task.assert_called()
 
+    def test_create_for_bad_handle(self):
+        # underscores gets translated to dashes, trailing/leading aren't allowed
+        for bad in 'fake:user_', '_fake:user':
+            with self.assertRaises(ValueError):
+                ATProto.create_for(Fake(id=bad))
+
     @patch('google.cloud.dns.client.ManagedZone', autospec=True)
     @patch.object(tasks_client, 'create_task', return_value=Task(name='my task'))
     @patch('requests.post',

tests/testutil.py

@@ -108,7 +108,7 @@ class Fake(User, protocol.Protocol):
                 or id in cls.fetchable)
 
     @classmethod
-    def owns_handle(cls, handle):
+    def owns_handle(cls, handle, allow_internal=False):
         return handle.startswith(f'{cls.LABEL}:handle:')
 
     @classmethod

web.py

@@ -358,10 +358,10 @@ class Web(User, Protocol):
         return False
 
     @classmethod
-    def owns_handle(cls, handle):
+    def owns_handle(cls, handle, allow_internal=False):
         if handle == PRIMARY_DOMAIN or handle in PROTOCOL_DOMAINS:
             return True
-        elif not is_valid_domain(handle, allow_internal=False):
+        elif not is_valid_domain(handle, allow_internal=allow_internal):
             return False
 
     @classmethod