plone.session 3.0

Session based authentication for Zope

Overview

plone.session implements secure session management for Zope sites.

In its default configuration plone.session uses an HMAC SHA-256 secure cryptographic hash to authenticate sessions. The hash is generated using the userid and a secret stored in the PAS plugin. Otherwise, the cookie format is identical to that of Apache’s mod_auth_tkt. For single sign on with the original mod_auth_tkt or another compatible implementation, set the mod_auth_tkt property to true. This invokes an MD5 based double hashing scheme. You will need to use the same secret across all servers.

This has several advantages over other session management systems:

• passwords are not sent 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.

• The cookie is only valid for the period specified by the timeout property.

There are some downsides to this approach:

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

• a user must have cookies enabled.

A session cookie is used to track sessions; that means that as long as a user keeps his browser open (and does not explicitly log out) the session remains open until the timout limit is reached. This can be changed by setting the timeout property of the plugin to the number of seconds the cookie should remain valid after the moment of login.

tktauth.py implements the core mod_auth_tkt functionality. It is self-contained and may be of useful to other frameworks.

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.

Configuration options

To enable logins between sites or other mod_auth_tkt systems, set the shared secret through the Zope Management Interface. You can manage the plone.keyring secrets through the same page.

The following properties may be set through the Properties tab:

Cookie validity timeout (in seconds)

After this, the session is invalid and the user must login again. Set to 0 for the cookie to remain valid indefinitely. Note that when the user folder has caching enabled, cookie validity may not be checked on every request.

Use mod_auth_tkt compatabile hashing algorithm

Compatibility with other implemenations, but at the cost of using a weaker hashing algorithm.

Cookie name

Which cookie to use. This must also be set on the credentials_cookie_auth plugin.

Cookie lifetime (in days)

This makes the cookie persistent across opening and closing the browser.

Cookie domain (blank for default)

A cookie may be shared across www1.example.com and www2.example.com by setting the cookie domain to .example.com.

Cookie path

What path the cookie is set valid (defaults to /.)

Single Sign On with IIS

For intranet setups with users on a Windows domain, it’s possible to configure IIS with Integrated Windows Authentication to act as an external login provider, even for sites running on Linux/Unix servers.

Requirements

• You need a Microsoft Windows Server running IIS. Preferably Windows Server 2003 or a later version.

• The server must be a member of the Windows domain you want to authenticate users for. It does not need to be an Active Directory server itself.

• You site should use LDAPMultiPlugins to use the same Active Directory as a user source. (Use plone.app.ldap to set this up with Plone.)

Python

• The Windows server needs to have Python 2.6 <http://www.python.org/download/> and the Python Win 32 extensions installed. (Currently Python 2.6.5 and pywin32-214.)

• Until pywin32-215 is released, apply this fix to the file:

  C:\Python26\Lib\site-packages\win32comext\axscript\client\framework.py

  and remove the framework.pyc and framework.pyo files.

• Place a copy of tktauth.py (from plone/session of this package) into:

  C:\Python26\Lib\site-packages\

• Follow these instructions on how to configure Python for IIS. In bullet point 2.d. use:

  Executable: "C:\Python26\python.exe -u %s %s"

  instead. This will ensure files are opened in universal newline mode. You can choose to only configure these settings for the specific web site and not the entire IIS. Adjust settings accordingly and create the web site first as detailed in the next chapter.

IIS

• Find and open the IIS management console.

• Create a new Web Site, by going into the Web Sites folder and using the right-click menu. You should get a wizard asking you for various questions:

  Description: SSO login service
  
  TCP port: 80
  
  Path: c:\Inetpub\sso
  
  Allow anonymous access to this Web site: <not checked>
  
  Permissions: Read, Run scripts, Execute

• If you are running IIS 6, you need to go to the Web Service Extensions folder and change Active Server Pages to be Allowed. Otherwise you will get rather unhelpful 404 Not Found errors for the asp scripts.

IIS script

• Copy the login.asp and test.asp scripts (from the iis-login folder of this package) into root path of the web site (for example C:Inetpubsso).

• You need to modify the SECRET constant found in the login.asp to the same shared secret set on plone.session’s Manage secrets tab.

• Modify the SITE_URL constant in login.asp ot the address our your Plone site.

• Access http://LOGONSERVER/test.asp to confirm access permissions are correctly configured.

Configuring browsers to allow automatic logon

Browsers must be configured to “trust” the logon server for user authentication data to be sent automatically.

By default, Internet Explorer sends logon information to servers within the “Intranet Zone”, so long as the site is accessed using it’s intranet name (http://LOGONSERVER/login.asp). If the site is accessed using a fully qualified domain name or IP address, it must be explicitly added to the list of trusted sites.

Firefox configuration information may be found in this article.

Configuring your Plone site

Ensure that you have setup authentication to Active Directory and that you can login with the your current Windows user name.

Set the following configuration options through the Zope interface:

• In /Plone/acl_users/session. On the Manage secrets

• In /Plone/acl_users/credentials_cookie_auth. On the Properties tab set Login Form to http://LOGONSERVER/login.asp

• In /Plone/portal_actions/user/login. On the Properties tab set URL (Expression) to python:portal.acl_users.credentials_cookie_auth.getProperty(‘login_path’).

Note for developers testing this under Windows XP

• IIS may be installed as an additional component using the Windows XP installation CD.

• The IIS management console can be located at:

  Start -> Control Panel -> Adminstrative Tools -> Internet Information Services

• The pywin32 installer setup IIS sufficiently for me not to need to follow the instructions on how to configure Python for IIS.

• I could not find how to setup a separate site, so placed the asp scripts directly in C:Inetpubwwwroot - the “Default Web Site”

• From the IIS management console, select “Default Web Site”. You should see login.asp and test.asp in the right hand pane. With each file, right-click Properties. On the File Security tab click Edit… on Anonymous access and authentication control. Uncheck Anonymous access and check Basic authentication (to be used as a fallback) and Integrated Windows authentication.

• Access http://localhost/test.asp to confirm IIS authentication works as expected.

• Set the secret in login.asp and Manage secrets of plone.session.

• Set SITE_URL in login.asp to http://localhost:8080/Plone (or whatever the address of your site is.)

• Add a Plone user with the same name as your Windows login name (e.g. Administrator), this avoids setting up Active Directory.

• Follow the section above to configure your Plone site, but set Login Form to http://localhost/login.asp.

Changelog

3.0 - 2010-07-18

• Update package metadata. [hannosch]

3.0b5 - 2010-06-13

• Make sure to load the right meta ZCML. [hannosch]

• Avoid deprecation warnings under Zope 2.13. [hannosch]

• Removed dependency on GPL licensed Products.PloneTestCase. [hannosch]

3.0b4 - 2010-05-23

• Make the secure option of cookies configurable. This allows to restrict cookies to HTTPS connections alone. This closes http://dev.plone.org/plone/ticket/7897. [pfurman, hannosch]

• Use the standard libraries doctest module, instead of the deprecated one from zope.testing. [hannosch]

• Marked the session cookie as HTTPOnly. [hannosch]

• PEP8 cleanup. [hannosch]

• Relicense as BSD following PF Board decision. http://lists.plone.org/pipermail/membership/2010-April/001123.html [elro]

3.0b3 - 2010-04-09

• Example IIS login form and documentation. This builds on work by Hanno and I at Jarn for Centrepoint. [elro]

• Support authentication by an external form, perhaps one running on an IIS server with Integrated Windows Authentication. [elro]

3.0b2 - 2010-03-09

• Prefix setupSession with underscore, the method should be unavailable TTW. [elro]

• Catch a ComponentLookupError in authenticateCredentials. [elro]

3.0b1 - 2010-03-05

• Add back the hash management UI with added functionality to set shared secret. [elro]

• Add properties for cookie domain and ticket validity timeout. [elro]

• Use mod_auth_tkt format cookies to give us a session validity timeout. By default we use a more secure HMAC SHA-256 hashing scheme. An MD5 based scheme compatible with other mod_auth_tkt implementations is optional. [elro]

• Remove the source component indirection. [elro]

3.0a2 - 2009-11-13

• Remove hash management UI which had been accidentally re-merged. [davisagli]

3.0a1 - 2009-04-04

• Avoid deprecation warning for the sha module in Python 2.6. [hannosch]

• Declare test dependencies in an extra. [hannosch]

• Specify package dependencies. [hannosch]

• Fixed the remaining tests to work with the new keyring backend. [hannosch]

• Fixed a component lookup call in the HashSession source. [davisagli, hannosch]

• Update default (hash) session source to use plone.keyring to manage the secrets. [wichert]

2.1 - 2009-02-04

• Protect the setupSession call with the ManageUsers permission. Fixes possible privilege escalation. [maurits]

• Make the cookie lifetime configurable. Patch by Rok Garbas. Fixes http://dev.plone.org/plone/ticket/7248 [wichert, garbas]

2.0 - 2008-07-08

• Fix CSRF protection for managing server secrets via the Plone session plugin for PAS. Fixes http://dev.plone.org/plone/ticket/8176 [witsch]

1.2 - 2007-02-15

• Use the binascii base64 methods to encode/decode the session cookie. This prevents newlines being inserted in long cookies. [wichert]

1.1 - 2007-09-11

• 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]

1.0 - 2007-08-15

• First stable release [wichert]