plone.session 1.1

Session based authentication for Zope

Overview

plone.session implements secure session management for Zope sites. It can be used directly, or be used as a base for custom session management strategies.

In its default configuration plone.sessions uses a secure cryptographic hash based on HMAC SHA-1 to authenticate sessions. The hash is generated using the users login name and a secret stored in the PAS plugin. This has several advantages over other session management systems:

• passwords are not send to the server in a cookie on every request, as is done by the Cookie Auth Helper

• it does not require any ZODB write for sessions, as is needed by the Session Crumbler. This allows it to scale very well.

• it allows you to invalidate all existing authentication cookies for users by updating the secret.

Using plone.session

plone.session only takes care of handling sessions for already authenticated users. This means it can not be used stand-alone: you need to have another PAS plugin, such as the standard Cookie Auth Helper to take care of authentication.

After a user has been authenticated plone.session can take over via the PAS credentials update mechanism.

Using custom session authentication

plone.session delegates the generation and verification of sessions to an ISessionSource adapter. This adapter adapts the PAS plugin and implements four methods:

createIdentifier

Return an identifier for a userid. An identifier is a standard python string object.

verifyIdentifier

Verify if an identity corresponds to a valid session. Returns a boolean indicating if the identify is valid.

extractLoginName

Extract the login name from an identifier.

invalidateSession

Mark a session for a principal as invalid. A source may not support this, in which case it should return False.

plone.sesion ships with two example adapers: hash and userid.

The userid adapter is a trivial example which uses the userid as session identifier. This is very insecure since there is no form of verification at all. DO NOT USE THIS ADAPTER IN YOUR SITE!

The hash plugin creates a random secret string which is stored as an attribute on your plugin. It uses this secret to create a SHA1 signature for the user id with the secret as session identifier. This approach has several good qualities:

• it allows us to verify that a session identifier was created by this site

• there is no need to include passwords in the session idenfitier

• it does not need to store anything in Zope itself. This means it works as-is in ZEO setups and can scale very well.

There are a few downsides to this approach:

• if a users password is changed or disabled session identifiers will continue to work, making it hard to lock out users

Changelog

Version 1.1 - September 11, 2007

• Use the userid instead of the login name in session identifiers. This has the side-effect of working around a bug in PAS which caused us to mix up users when the login name used was an inexact match for another login name. [wichert]

Version 1.0 - August 15, 2007

• First stable release [wichert]