TWiki User Authentication

TWiki site access control and user activity tracking options

Overview

• You are guest, TWikiGuest,

Tip:

TWiki:TWiki.TWikiUserAuthenticationSupplement

Password Management

As shipped, TWiki supports the Apache 'htpasswd' password manager. This manager supports the use of .htpasswd files on the server. These files can be unique to TWiki, or can be shared with other applications (such as an Apache webserver). A variety of password encodings are supported for flexibility when re-using existing files. See the descriptive comments in the Security Settings section of the configure interface for more details.

You can easily plug in alternate password management modules to support interfaces to other third-party authentication databases.

User Mapping

User Registration

Note:

Login Management

No Login (select none in configure)

Note:

Template Login (select =TWiki::LoginManager::TemplateLogin in configure)

Template Login asks for a username and password in a web page, and processes them using whatever Password Manager you choose. Users can log in and log out. Client Sessions are used to remember users. Users can choose to have their session remembered so they will automatically be logged in the next time they start their browser.

Enabling Template Login

1. Use the configure interface to
   1. select the TWiki::LoginManager::TemplateLogin login manager (on the Security Settings pane).
   2. select the appropriate password manager for your system, or provide your own.

1. Register yourself in the TWikiRegistration topic.
   Check that the password manager recognises the new user. If you are using .htpasswd files, check that a new line with the username and encrypted password is added to the .htpasswd file. If not, you probably got a path wrong, or the permissions may not allow the webserver user to write to that file.
2. Create a new topic to check if authentication works.
3. Edit the TWikiAdminGroup topic in the Main web to include users with system administrator status.
   This is a very important step, as users in this group can access all topics, independent of TWiki access controls.

TWikiAccessControl has more information on setting up access controls.

At this time TWikiAccessControls cannot control access to files in the pub area, unless they are only accessed through the viewfile script. If your pub directory is set up in the webserver to allow open access you may want to add .htaccess files in there to restrict access.

You can create a custom version of the TWikiRegistration form by copying the topic, and then deleting or adding input tags in your copy. The name="" parameter of the input tags must start with: "Twk0..." (if this is an optional entry), or "Twk1..." (if this is a required entry). This ensures that the fields are carried over into the user profile page correctly. Do not modify the version of TWikiRegistration shipped with TWiki, as your changes will be overwritten next time you upgrade.

The default new user template page is in TWiki.NewUserTemplate. The same variables get expanded as in the template topics. You can create a custom new user profile page by creating the Main.NewUserTemplate topic, which will then override the default.

Apache Login (select =TWiki::LoginManager::ApacheLogin in configure)

Using this method TWiki does not authenticate users internally. Instead it depends on the REMOTE_USER environment variable, which is set when you enable authentication in the webserver.

TWiki maps the REMOTE_USER that was used to log in to the webserver to a WikiName using the table in TWikiUsers. This table is updated whenever a user registers, so users can choose not to register (in which case their webserver login name is used for their signature) or register (in which case that login name is mapped to their WikiName).

The same private .htpasswd file used in TWiki Template Login can be used to authenticate Apache users, using the Apache Basic Authentication support.

Warning: Do not use the Apache htpasswd program with .htpasswd files generated by TWiki! htpasswd wipes out email addresses that TWiki plants in the info fields of this file.

Enabling Apache Login using =mod_auth

1. Use configure to select the TWiki::LoginManager::ApacheLogin login manager.
2. Use configure to set up TWiki to create the right kind of .htpasswd entries.

1. You can create a custom version of the TWikiRegistration form by copying the default topic, and then deleting or adding input tags in your copy. The name="" parameter of the input tags must start with: "Twk0..." (if this is an optional entry), or "Twk1..." (if this is a required entry). This ensures that the fields are carried over into the user profile page correctly. Do not modify the version of TWikiRegistration shipped with TWiki, as your changes will be overwritten next time you upgrade.
   The default new user template page is in TWiki.NewUserTemplate. The same variables get expanded as in the template topics. You can create a custom new user profile page by creating the Main.NewUserTemplate topic, which will then override the default.
2. Register yourself in the TWikiRegistration topic.
   Check that a new line with the username and encrypted password is added to the .htpasswd file. If not, you may have got a path wrong, or the permissions may not allow the webserver user to write to that file.
3. Create a new topic to check if authentication works.
4. Edit the TWikiAdminGroup topic in the Main web to include users with system administrator status.
   This is a very important step, as users in this group can access all topics, independent of TWiki access controls.

Logons via bin/logon

Sessions

TWiki uses the CPAN:CGI::Session and CPAN:CGI::Cookie modules to track sessions. These modules are de facto standards for session management among Perl programmers. If you can't use Cookies for any reason, CPAN:CGI::Session also supports session tracking using the client IP address.

Getting, Setting, and Clearing Session Variables

You can get, set, and clear session variables from within TWiki web pages or by using script parameters. This allows you to use the session as a personal "persistent memory space" that is not lost until the web browser is closed. Also note that if a session variable has the same name as a TWiki preference, the session variables value takes precedence over the TWiki preference. This allows for per-session preferences.

To make use of these features, use the variables:

Special read-only session variables:

• %SESSION_VARIABLE{"AUTHUSER"}% - user ID, current value:
• %SESSION_VARIABLE{"SESSION_REQUEST_NUMBER"}% - number of pages accessed by current user since login, current value:

Notes:

• You cannot override access controls preferences this way.
• You can use the SetGetPlugin to set and get variables that are not user specific. This plugin can store variables persistently if needed.

Cookies and Transparent Session IDs

TWiki normally uses cookies to store session information on a client computer. Cookies are a common way to pass session information from client to server. TWiki cookies simply hold a unique session identifier that is used to look up a database of session information on the TWiki server.

For a number of reasons, it may not be possible to use cookies. In this case, TWiki has a fallback mechanism; it will automatically rewrite every internal URL it sees on pages being generated to one that also passes session information.

TWiki Username vs. Login Username

This section applies only if you are using authentication with existing login names (i.e. mapping from login names to WikiNames).

TWiki internally manages two usernames: Login Username and TWiki Username.

• Login Username: When you login to the intranet, you use your existing login username, ex: pthoeny. This name is normally passed to TWiki by the REMOTE_USER environment variable, and used internally. Login Usernames are maintained by your system administrator.

• TWiki Username: Your name in WikiNotation, ex: PeterThoeny, is recorded when you register using TWikiRegistration; doing so also generates a user profile page in the Main web.

TWiki can automatically map an Intranet (Login) Username to a TWiki Username if the {AllowLoginName} is enabled in configure. The default is to use your WikiName as a login name.

NOTE: To correctly enter a WikiName - your own or someone else's - be sure to include the Main web name in front of the Wiki username, followed by a period, and no spaces, for example Main.WikiUsername or %USERSWEB%.WikiUsername. This points WikiUsername to the Main web, where user profile pages are located, no matter which web it's entered in. Without the web prefix, the name appears as a NewTopic everywhere but in the Main web.

Changing Passwords

If your {PasswordManager} supports password changing, you can change and reset passwords using forms on regular pages.

• The ChangePassword form ( TWiki/ChangePassword )
• The ResetPassword form ( TWiki/ResetPassword )

Changing E-mail Addresses

If the active {PasswordManager} supports storage and retrieval of user e-mail addresses, you can change your e-mail using a regular page. As shipped, this is true only for the Apache 'htpasswd' password manager.

• The ChangeEmailAddress form ( TWiki/ChangeEmailAddress )

Controlling access to individual scripts

• For Template Login, update the {AuthScripts} list using configure
• For Apache Login, add/remove the script from .htaccess

How to choose an authentication method

At one extreme, the most secure method is to use TWiki via SSL (Secure Sockets Layer), with a login manager installed and Client Sessions turned off.

Using TWiki with sessions turned off is a pain, though, as with all the login managers there are occasions where TWiki will forget who you are. The best user experience is achieved with sessions turned on.

As soon as you allow the server to maintain information about a logged-in user, you open a door to potential attacks. There are a variety of ways a malicious user can pervert TWiki to obtain another users session ID, the most common of which is known as a cross-site scripting attack. Once a hacker has an SID they can pretend to be that user.

To help prevent these sorts of attacks, TWiki supports IP matching, which ensures that the IP address of the user requesting a specific session is the same as the IP address of the user who created the session. This works well as long as IP addresses are unique to each client, and as long as the IP address of the client can't be faked.

Session IDs are usually stored by TWiki in cookies, which are stored in the client browser. Cookies work well, but not all environments or users permit cookies to be stored in browsers. So TWiki also supports two other methods of determining the session ID. The first method uses the client IP address to determine the session ID. The second uses a rewriting method that rewrites local URLs in TWiki pages to include the session ID in the URL.

The first method works well as long as IP addresses are unique to each individual client, and client IP addresses can't be faked by a hacker. If IP addresses are unique and can't be faked, it is almost as secure as cookies + IP matching, so it ranks as the fourth most secure method.

If you have to turn IP matching off, and cookies can't be relied on, then you may have to rely on the second method, URL rewriting. This method exposes the session IDs very publicly, so should be regarded as "rather dodgy".

Template Login degrades to url re-writing when you use a client like dillo that does not support cookies. However, you can log out and back in as a different user.

Finally, it would be really neat if someone was to work out how to use certificates to identify users.....

See TWiki:TWiki.SecuringTWikiSite for more information.

Related Topics: AdminDocumentationCategory, TWikiAccessControl, VarAUTHREALM, VarGET, VarLOGIN, VarLOGOUT, VarSESSIONID, VarSESSIONVAR, VarSESSIONVARIABLE, VarSET, TWiki:TWiki.TWikiUserAuthenticationSupplement, TWiki:TWiki.SecuringTWikiSite

-- Contributors: TWiki:Main.PeterThoeny, TWiki:Main.MikeMannix, TWiki:Main.CrawfordCurrie, TWiki:Main.SvenDowideit