AttributeError: is_authenticated

[Dirk Stöcker]

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 609, in dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 301, in dispatch
    raise e
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 210, in dispatch
    chosen_handler = self._get_valid_default_handler(req)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 337, in _get_valid_default_handler
    name = req.session.get('default_handler')
  File "/usr/local/lib/python3.10/dist-packages/trac/web/api.py", line 661, in __getattr__
    value = self.callbacks[name](self)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 364, in _get_session
    return Session(self.env, req)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/session.py", line 266, in __init__
    if not req.is_authenticated:
  File "/usr/local/lib/python3.10/dist-packages/trac/web/api.py", line 664, in __getattr__
    raise AttributeError(name)
AttributeError: is_authenticated

We got multiple reports since Trac 1.6 which report an error which is only temporary and wasn't reproducible for us.

Original reports and duplicates here: ​https://josm.openstreetmap.de/ticket/23394

Log shows 116 entries since May 2024.

I don't understand the @lazy stuff in python and found no good description, so I can't debug it myself.

[Jun Omae]

Thanks for the reporting. I'll investigate it.

[Jun Omae]

Unable to reproduce it to me.

Hmm, I'm considering that AttributeError was raised from req.authname in req.is_authenticated. So that, it is probably caused by LoginModule.authenticate (in Trac or ​th:AccountManagerPlugin).

trac/web/api.py

@@ -685 +685 @@
     def __getattr__(self, name):
         """Performs lazy attribute lookup by delegating to the functions in the
         callbacks dictionary."""
-        if name in self.callbacks:
-            value = self.callbacks[name](self)
-            setattr(self, name, value)
-            return value
+        try:
+            if name in self.callbacks:
+                value = self.callbacks[name](self)
+                setattr(self, name, value)
+                return value
+        except AttributeError as e:
+            raise ValueError('AttributeError caught while resolving %s '
+                             'attribute' % name)
         raise AttributeError(name)
 
     def __repr__(self):

[Dirk Stöcker]

Why do you believe it is the if? Line 664 is raise AttributeError(name) which also matches the error. So that would be the line after your change.

My interpretation is that Request.__getattr__("is_authenticated") is called instead of Request.is_authenticated(). But as said, I don't fully understand the programm flow yet, but at east I found the @lazy code which it seems mainly caches the call result.

[Jun Omae]

Demonstration:

>>> from trac.web.api import Request
>>> environ = {'SERVER_PORT': '80', 'SERVER_NAME': 'localhost', 'wsgi.url_scheme': 'http'}
>>> start_response = lambda: ()
>>> req = Request(environ, start_response)
>>> def autenticate(req):
...   raise AttributeError('from autenticate')
...
>>> req.callbacks['authname'] = autenticate
>>> req.authname
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 689, in __getattr__
    value = self.callbacks[name](self)
  File "<stdin>", line 2, in autenticate
AttributeError: from autenticate
>>> req.is_authenticated
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 692, in __getattr__
    raise AttributeError(name)
AttributeError: is_authenticated

1. Read req.is_authenticated attribute
2. Read req.authname in the is_authenticated method
3. The callback for authname raises AttributeError
4. is_authenticated method raises the AttributeError
5. Python interpreter tries to resolve is_authenticated from __getattr__ because AttributeError is raised from is_authenticated
6. AttributeError(name) is raised because is_authenticated is not in the callbacks
7. We received the AttributeError from __getattr__

---

Applying the patch in comment:3 and the following patch:

trac/util/__init__.py

@@ -1298 +1298 @@
         functools.update_wrapper(self, fn)
 
     def __get__(self, instance, owner):
-        if instance is None:
-            return self
-        if self.fn.__name__ in instance.__dict__:
-            return instance.__dict__[self.fn.__name__]
-        result = self.fn(instance)
-        instance.__dict__[self.fn.__name__] = result
-        return result
+        try:
+            if instance is None:
+                return self
+            if self.fn.__name__ in instance.__dict__:
+                return instance.__dict__[self.fn.__name__]
+            result = self.fn(instance)
+            instance.__dict__[self.fn.__name__] = result
+            return result
+        except AttributeError:
+            raise ValueError('AttributeError caught while resolving %s '
+                             'attribute' % self.fn.__name__)
 
     def __set__(self, instance, value):
         instance.__dict__[self.fn.__name__] = value

After the patch, trying demonstration code:

>>> req.authname
Traceback (most recent call last):
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 690, in __getattr__
    value = self.callbacks[name](self)
  File "<stdin>", line 2, in autenticate
AttributeError: from autenticate

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 694, in __getattr__
    raise ValueError('AttributeError caught while resolving %s '
ValueError: AttributeError caught while resolving authname attribute
>>> req.is_authenticated
Traceback (most recent call last):
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 690, in __getattr__
    value = self.callbacks[name](self)
  File "<stdin>", line 2, in autenticate
AttributeError: from autenticate

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jun66j5/src/tracdev/git/trac/util/__init__.py", line 1306, in __get__
    result = self.fn(instance)
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 713, in is_authenticated
    return self.authname and self.authname != 'anonymous'
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 694, in __getattr__
    raise ValueError('AttributeError caught while resolving %s '
ValueError: AttributeError caught while resolving authname attribute
>>>

[Dirk Stöcker]

Applied. I'll report results.

[Dirk Stöcker]

It seems you're right and this may be caused by auth manager plugin.

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/dist-packages/trac/web/api.py", line 662, in __getattr__
    value = self.callbacks[name](self)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 180, in authenticate
    authname = authenticator.authenticate(req)
  File "/usr/local/lib/python3.10/dist-packages/acct_mgr/util.py", line 54, in wrap
    return func(self, *args, **kwds)
  File "/usr/local/lib/python3.10/dist-packages/acct_mgr/web_ui.py", line 488, in authenticate
    return super(LoginModule, self).authenticate(req)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/auth.py", line 97, in authenticate
    authname = self._get_name_for_cookie(req,
  File "/usr/local/lib/python3.10/dist-packages/acct_mgr/web_ui.py", line 596, in _get_name_for_cookie
    cookie.value = hex_entropy()
AttributeError: can't set attribute 'value'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 609, in dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 301, in dispatch
    raise e
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 214, in dispatch
    chosen_handler = self._pre_process_request(req, chosen_handler)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 456, in _pre_process_request
    chosen_handler = filter_.pre_process_request(req, chosen_handler)
  File "/usr/local/lib/python3.10/dist-packages/acct_mgr/api.py", line 469, in pre_process_request
    if not req.session.authenticated or 'ACCTMGR_USER_ADMIN' in req.perm:
  File "/usr/local/lib/python3.10/dist-packages/trac/web/api.py", line 662, in __getattr__
    value = self.callbacks[name](self)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/main.py", line 364, in _get_session
    return Session(self.env, req)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/session.py", line 266, in __init__
    if not req.is_authenticated:
  File "/usr/local/lib/python3.10/dist-packages/trac/util/__init__.py", line 1306, in __get__
    result = self.fn(instance)
  File "/usr/local/lib/python3.10/dist-packages/trac/web/api.py", line 685, in is_authenticated
    return self.authname and self.authname != 'anonymous'
  File "/usr/local/lib/python3.10/dist-packages/trac/web/api.py", line 666, in __getattr__
    raise ValueError('AttributeError caught while resolving %s '
ValueError: AttributeError caught while resolving authname attribute

[Jun Omae]

Okay. That is an issue of ​th:AccountManagerPlugin.

acct_mgr/web_ui.py

@@ -593 +593 @@
             if random.random() + self.cookie_refresh_pct / 100.0 > 1:
                 old_cookie = cookie.value
                 # Update auth cookie value
-                cookie.value = hex_entropy()
+                new_cookie = hex_entropy()
+                cookie.set('value', new_cookie, new_cookie)
                 self.log.debug("Changing session id for user %s to %s", name,
                                cookie.value)
 

Python 3.11.10 (main, Sep  7 2024, 18:35:42) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from trac.web.api import Cookie
>>> cookies = Cookie('name1=value1; name2=value2')
>>> cookies
<Cookie: name1='value1' name2='value2'>
>>> cookies['name1']
<Morsel: name1=value1>
>>> cookies['name1'].value = '?'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: property 'value' of 'Morsel' object has no setter
>>> cookies['name1'].value = 'vvv'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: property 'value' of 'Morsel' object has no setter
>>> cookies['name1'].set('value', 'vvvv', 'vvvv')
>>> cookies['name1'].value
'vvvv'
>>>