def _validate_came_from(self, came_from,

            _re=re.compile(r"/(?!/)[-!#$%&'()*+,./:;=?@_~0-9A-Za-z]*$")):

        """Return True if came_from is valid and can and should be used.

        Determines if a URI reference is valid and relative to the origin;

        or in RFC 3986 terms, whether it matches this production:

          origin-relative-ref = path-absolute [ "?" query ] [ "#" fragment ]

        with the exception that '%' escapes are not validated and '#' is

        allowed inside the fragment part.

        """

        return _re.match(came_from) is not None

    def index(self):

        c.came_from = safe_str(request.GET.get('came_from', ''))

        if c.came_from:

            if not self._validate_came_from(c.came_from):

                log.error('Invalid came_from (not server-relative): %r', c.came_from)

                raise HTTPBadRequest()

        else:

            c.came_from = url('home')

        # redirect if already logged in

            raise HTTPFound(location=c.came_from)

        if request.POST:

            # import Login Form validator class

            login_form = LoginForm()()

            try:

                c.form_result = login_form.to_python(dict(request.POST))

                # form checks for username/password, now we're authenticated

                username = c.form_result['username']

                user = User.get_by_username_or_email(username, case_insensitive=True)

            except formencode.Invalid as errors:

                defaults = errors.value

                # remove password from filling in form again

                defaults.pop('password', None)

                return htmlfill.render(

                    render('/login.html'),

                    defaults=errors.value,

                    errors=errors.error_dict or {},

                    prefix_error=False,

                    encoding="UTF-8",

                    force_defaults=False)

            except UserCreationError as e:

                # container auth or other auth functions that create users on

                # the fly can throw this exception signaling that there's issue

    """Client must be logged in as a valid User, or we'll redirect to the login

    page.

    If the "default" user is enabled and allow_default_user is true, that is

    considered valid too.

    Also checks that IP address is allowed, and if using API key instead

    of regular cookie authentication, checks that API key access is allowed

    (based on `api_access` parameter and the API view whitelist).

    """

    def __init__(self, api_access=False, allow_default_user=False):

        self.api_access = api_access

        self.allow_default_user = allow_default_user

    def __call__(self, func):

        return decorator(self.__wrapper, func)

    def __wrapper(self, func, *fargs, **fkwargs):

        controller = fargs[0]

        user = request.authuser

        loc = "%s:%s" % (controller.__class__.__name__, func.__name__)

        log.debug('Checking access for user %s @ %s', user, loc)

        # Check if we used an API key to authenticate.

        api_key = user.authenticating_api_key

        if api_key is not None:

            # Check that controller is enabled for API key usage.

            if not self.api_access and not allowed_api_access(loc, api_key=api_key):

                # controller does not allow API access

                log.warning('API access to %s is not allowed', loc)

                raise HTTPForbidden()

            log.info('user %s authenticated with API key ****%s @ %s',

                     user, api_key[-4:], loc)

            return func(*fargs, **fkwargs)

        # CSRF protection: Whenever a request has ambient authority (whether

        # through a session cookie or its origin IP address), it must include

        # the correct token, unless the HTTP method is GET or HEAD (and thus

        # guaranteed to be side effect free. In practice, the only situation

        # where we allow side effects without ambient authority is when the

        # authority comes from an API key; and that is handled above.

        if request.method not in ['GET', 'HEAD']:

            token = request.POST.get(secure_form.token_key)

            if not token or token != secure_form.authentication_token():

                log.error('CSRF check failed')

                raise HTTPForbidden()

        # this assumption.

        if request.method not in ['POST', 'PUT'] and request.POST:

            log.error('%r request with payload parameters; WebOb should have stopped this', request.method)

            raise webob.exc.HTTPBadRequest()

    def __call__(self, environ, context):

        try:

            request.ip_addr = _get_ip_addr(environ)

            # make sure that we update permissions each time we call controller

            self._basic_security_checks()

            # set globals for auth user

            bearer_token = None

            try:

                # Request.authorization may raise ValueError on invalid input

                type, params = request.authorization

            except (ValueError, TypeError):

                pass

            else:

                if type.lower() == 'bearer':

                    bearer_token = params

                request.GET.get('api_key'),

                bearer_token,

                session.get('authuser'),

            )

            log.info('IP: %s User: %s accessed %s',

                request.ip_addr, request.authuser,

                safe_unicode(_get_access_path(environ)),

            )

            return super(BaseController, self).__call__(environ, context)

        except webob.exc.HTTPException as e:

            return e

class BaseRepoController(BaseController):

    """

    Base class for controllers responsible for loading all needed data for

    repository loaded items are

    c.db_repo_scm_instance: instance of scm repository

    c.db_repo: instance of db

    c.repository_followers: number of followers

    c.repository_forks: number of forks

    c.repository_following: weather the current user is following the current repo

    """

    def _before(self, *args, **kwargs):

        super(BaseRepoController, self)._before(*args, **kwargs)

        if c.repo_name:  # extracted from routes