repoze.who.plugins.memcached

This is a repoze.who IAuthenticator/IMetadataProvider plugin that can cache the results of other plugins using memcached. It's useful for reducing load on e.g. a backend LDAP auth system.

To use it, give it the name of an authenticator and/or metadata provider whose results it should wrap:

[plugin:ldap]
use = my.ldap.authenticator

[plugin:cached_ldap]
use = repoze.who.plugins.memcached
authenticator_name = ldap

[authenticators]
plugins = cached_ldap ldap;unused

(The "ldap;unused" bit ensures that the wrapped ldap plugin still gets loaded, but is not used for matching any requests. Yeah, it's yuck.)

To prevent a compromise of the cache from revealing auth credentials, this plugin calculates a HMAC hash of the items in the incoming identity and uses that as the cache key. This makes it possible to check the cache for a match to an incoming identity, while preventing the cache keys from being reversed back into a valid identity.

Items added to the identity by the wrapped plugin will be stored in the cached value and will not be encryped or obfuscated in any way.

The following configuration options are available:

• memcached_urls: A list of URLs for the underlying memcached store.
• authenticator_name: The name of an IAuthenticator plugin to wrap.
• mdprovider_name: The name of an IMetadataProvider plugin to wrap.

• key_items: A list of names from the identity dict that should be

  hashed to produce the cache key. These items should uniquely and validly identity a user. By default it will use all keys in the identity in sorted order.

• value_items: A list of names from the identity dict that should be

  stored in the cache. These would typically be items of metadata such as the user's email address. By default this will include all items that the wrapped plugin adds to the identity.

• secret: A string used when calculating the HMAC the cache keys.

  All servers accessing a shared cache should use the same secret so they produce the same set of cache keys.

• ttl: The time for which cache entries should persist, in seconds.