csrf.py 文件源码

def _get_token(self, request):
        if settings.CSRF_USE_SESSIONS:
            try:
                return request.session.get(CSRF_SESSION_KEY)
            except AttributeError:
                raise ImproperlyConfigured(
                    'CSRF_USE_SESSIONS is enabled, but request.session is not '
                    'set. SessionMiddleware must appear before CsrfViewMiddleware '
                    'in MIDDLEWARE%s.' % ('_CLASSES' if settings.MIDDLEWARE is None else '')
                )
        else:
            try:
                cookie_token = request.COOKIES[settings.CSRF_COOKIE_NAME]
            except KeyError:
                return None

            csrf_token = _sanitize_token(cookie_token)
            if csrf_token != cookie_token:
                # Cookie token needed to be replaced;
                # the cookie needs to be reset.
                request.csrf_cookie_needs_reset = True
            return csrf_token