NormalizingFilter performs incorrect validation of PATH_INFO variable

[Venkat Sundaram]

class NormalizingFilter(wsgi.Middleware):
    """Middleware filter to handle URL normalization."""

    def process_request(self, request):
        """Normalizes URLs."""
        # Removes a trailing slash from the given path, if any.
        if (len(request.environ['PATH_INFO']) > 1 and
                request.environ['PATH_INFO'][-1] == '/'):
            request.environ['PATH_INFO'] = request.environ['PATH_INFO'][:-1]
        # Rewrites path to root if no path is given.
        elif not request.environ['PATH_INFO']:
            request.environ['PATH_INFO'] = '/'

The if condition performs a length check without checking if PATH_INFO is None. Instead, the check is done in the elif clause.
Shouldn't this validation instead be like below ?

    def process_request(self, request):
        """Normalizes URLs."""
        # Rewrites path to root if no path is given.
        if not request.environ['PATH_INFO']:
            request.environ['PATH_INFO'] = '/'
        # Removes a trailing slash from the given path, if any.
        elif (len(request.environ['PATH_INFO']) > 1 and
                request.environ['PATH_INFO'][-1] == '/'):
            request.environ['PATH_INFO'] = request.environ['PATH_INFO'][:-1]

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/67634

[Lance Bragstad (lbragstad)]

Do you happen to have a stack trace from running into this error?

[Venkat Sundaram (tsv)]

Thanks for looking into this.
No. I came across this while reading the code. Also, my proposed "fix" had a bug which I modified as follows:

if not request.environ['PATH_INFO']:

changed to

if not request.environ.get('PATH_INFO'):

[Adam Young (ayoung)]

Please clarify the bug: show what is in error. It sounds suspect thus far.

[Dolph Mathews (dolph)]

Need a way to reproduce this as an actual issue.

[Morgan Fainberg (mdrnstm)]

I'm marking this as Invalid as it would have expired out a long time ago had it not been assigned to someone (based on being incomplete)