Sometimes get "incorrect padding error"- new bug in django 3.1?

[Diptesh Choudhuri]

Environment:




Request Method: GET
Request URL: http://127.0.0.1:8000/admin/


Django Version: 3.1
Python Version: 3.8.3
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'rest_framework',
 'rest_framework.authtoken',
 'accounts.apps.AccountsConfig',
 'posts.apps.PostsConfig']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']






Traceback (most recent call last):
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 215, in _get_session
    return self._session_cache


During handling of the above exception ('SessionStore' object has no attribute '_session_cache'), another exception occurred:
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 118, in decode
    return signing.loads(session_data, salt=self.key_salt, serializer=self.serializer)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/core/signing.py", line 135, in loads
    base64d = TimestampSigner(key, salt=salt).unsign(s, max_age=max_age).encode()
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/core/signing.py", line 201, in unsign
    result = super().unsign(value)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/core/signing.py", line 184, in unsign
    raise BadSignature('Signature "%s" does not match' % sig)


During handling of the above exception (Signature "JKiu07_FryzGGxaZmuA9hc0WmtZKBMOOeOj3Fp3j8ho" does not match), another exception occurred:
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/core/handlers/base.py", line 179, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/admin/sites.py", line 251, in wrapper
    return self.admin_view(view, cacheable)(*args, **kwargs)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/views/decorators/cache.py", line 44, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/admin/sites.py", line 222, in inner
    if not self.has_permission(request):
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/admin/sites.py", line 196, in has_permission
    return request.user.is_active and request.user.is_staff
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/utils/functional.py", line 240, in inner
    self._setup()
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/utils/functional.py", line 376, in _setup
    self._wrapped = self._setupfunc()
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/auth/middleware.py", line 23, in <lambda>
    request.user = SimpleLazyObject(lambda: get_user(request))
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/auth/middleware.py", line 11, in get_user
    request._cached_user = auth.get_user(request)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/auth/__init__.py", line 174, in get_user
    user_id = _get_user_session_key(request)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/auth/__init__.py", line 58, in _get_user_session_key
    return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 65, in __getitem__
    return self._session[key]
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 220, in _get_session
    self._session_cache = self.load()
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/db.py", line 44, in load
    return self.decode(s.session_data) if s else {}
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 122, in decode
    return self._legacy_decode(session_data)
  File "/home/ignisda/.cache/pypoetry/virtualenvs/backend-3DENPaHW-py3.8/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 126, in _legacy_decode
    encoded_data = base64.b64decode(session_data.encode('ascii'))
  File "/usr/lib/python3.8/base64.py", line 87, in b64decode
    return binascii.a2b_base64(s)


Exception Type: Error at /admin/
Exception Value: Incorrect padding

This happened first when I was developing on my Android device using Termux app. I switched my browser to Google-Chrome and the issue was resolved.

Then today I was developing on my PC, using qutebrowser and this error popped up again. Switching to Google-Chrome fixed the issue.

I don't think this is an issue with the browsers themselves, because I have completed entire django projects in both these devices, and never had to switch to Chrome.

The only differences happen to be- This is my first time using djangorestframework, first time using django 3.1

Is this a bug that has leaked into django 3.1 inadvertently?

[Matthew Hegarty]

Hey Diptesh - did you get anywhere with understanding this?  Did y ou get any response from the Django devs?

Just happened to me on my Staging site.  Recently upgraded from 3.0 to 3.1

I can login with Firefox, but Chrome crashes with the following error:

```python

Internal Server Error: /home/

Traceback (most recent call last):

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 215, in _get_session

return self._session_cache

AttributeError: 'SessionStore' object has no attribute '_session_cache'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 118, in decode

return signing.loads(session_data, salt=self.key_salt, serializer=self.serializer)

File "/usr/local/lib/python3.8/site-packages/django/core/signing.py", line 135, in loads

base64d = TimestampSigner(key, salt=salt).unsign(s, max_age=max_age).encode()

File "/usr/local/lib/python3.8/site-packages/django/core/signing.py", line 201, in unsign

result = super().unsign(value)

File "/usr/local/lib/python3.8/site-packages/django/core/signing.py", line 184, in unsign

raise BadSignature('Signature "%s" does not match' % sig)

django.core.signing.BadSignature: Signature "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" does not match

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/usr/local/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner

response = get_response(request)

File "/usr/local/lib/python3.8/site-packages/django/core/handlers/base.py", line 179, in _get_response

response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/local/lib/python3.8/site-packages/django/views/generic/base.py", line 73, in view

return self.dispatch(request, *args, **kwargs)

File "/usr/local/lib/python3.8/site-packages/django/contrib/auth/mixins.py", line 50, in dispatch

if not request.user.is_authenticated:

File "/usr/local/lib/python3.8/site-packages/django/utils/functional.py", line 240, in inner

self._setup()

File "/usr/local/lib/python3.8/site-packages/django/utils/functional.py", line 376, in _setup

self._wrapped = self._setupfunc()

File "/usr/local/lib/python3.8/site-packages/django_otp/middleware.py", line 38, in _verify_user

user.otp_device = None

File "/usr/local/lib/python3.8/site-packages/django/utils/functional.py", line 270, in __setattr__

self._setup()

File "/usr/local/lib/python3.8/site-packages/django/utils/functional.py", line 376, in _setup

self._wrapped = self._setupfunc()

File "/usr/local/lib/python3.8/site-packages/django/contrib/auth/middleware.py", line 23, in <lambda>

request.user = SimpleLazyObject(lambda: get_user(request))

File "/usr/local/lib/python3.8/site-packages/django/contrib/auth/middleware.py", line 11, in get_user

request._cached_user = auth.get_user(request)

File "/usr/local/lib/python3.8/site-packages/django/contrib/auth/__init__.py", line 174, in get_user

user_id = _get_user_session_key(request)

File "/usr/local/lib/python3.8/site-packages/django/contrib/auth/__init__.py", line 58, in _get_user_session_key

return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 65, in __getitem__

return self._session[key]

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 220, in _get_session

self._session_cache = self.load()

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/db.py", line 44, in load

return self.decode(s.session_data) if s else {}

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 122, in decode

return self._legacy_decode(session_data)

File "/usr/local/lib/python3.8/site-packages/django/contrib/sessions/backends/base.py", line 126, in _legacy_decode

encoded_data = base64.b64decode(session_data.encode('ascii'))

File "/usr/local/lib/python3.8/base64.py", line 87, in b64decode

return binascii.a2b_base64(s)

binascii.Error: Incorrect padding

```

[Matthew Hegarty]

Raised a ticket

The only workaround is to truncate the django_session table.  (clearsessions did not work) 

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