Add the WSGI filter to /etc/swift/proxy.conf.
[filter:basicauth]
use = egg:swift_basicauth#swift_basicauth
#auth_host=localhost
#auth_port=5000
#auth_protocol=http
#token_cache_time=300.0
Then add the filter to the proxy's main pipeline, just before authtoken like so:
[pipeline:main]
pipeline = catch_errors cache basicauth authtoken keystone proxy-server