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TWiki Access Control

Restricting read and write access to topics and webs, by Users and groups

TWikiAccessControl allows you restrict access to single topics and entire webs, by individual user and by user Groups, in three areas: view; edit & attach; and rename/move/delete. Access control, combined with TWikiUserAuthentication, lets you easily create and manage an extremely flexible, fine-grained privilege system.

An Important Control Consideration

Open, freeform editing is the essence of WikiCulture - what makes TWiki different and often more effective than other collaboration tools. For that reason, it is strongly recommended that decisions to restrict read or write access to a web or a topic are made with care - the more restrictions, the less Wiki in the mix. Experience shows that unrestricted write access works very well because:

As a collaboration guideline:

Users and Groups

Access control is based on the familiar concept of Users and Groups. Users are defined by their WikiNames. They can then be organized in unlimited combinations by inclusion in one or more user Groups. For convenience, Groups can also be included in other Groups.

Managing Users

A user can create an account in TWikiRegistration. The following actions are performed:

Users can be authenticated using Basic Authentication (htaccess) or SSL (secure server). In either case, TWikiUserAuthentication is required in order to track user identities, and use User and Group access control.

The default visitor name is TWikiGuest. This is the non-authenticated user.

Managing Groups

Groups are defined by group topics created in the Main web, like the TWikiAdminGroup. To create a new group:

  1. Edit TWikiGroups by entering a new topic with a name that ends in Group. Example:
    • SomeGroup
  2. Set Preferences for two Variables in the new group topic:
    • Set GROUP = < list of Users and/or Groups >
    • Set ALLOWTOPICCHANGE = < list of Users and/or Groups >
    • The GROUP variable is a comma-separated list of Users and/or other Groups. Example:
      • Set GROUP = Main.SomeUser, Main.OtherUser, Main.SomeGroup
    • ALLOWTOPICCHANGE defines who is allowed to change the group topic; it is a comma delimited list of Users and Groups. You typically want to restrict that to the members of the group itself, so it should contain the name of the topic. (This prevents Users not in the Group from editing the topic to give themselves or others access. For example, for the TWikiAdminGroup topic write:
    • Set ALLOWTOPICCHANGE = Main.TWikiAdminGroup

Restricting Write Access

You can define who is allowed to make changes to a web or a topic.

Deny Editing by Topic

Denying editing of a topic also restricts file attachment; both privileges are assigned together.

Deny Editing by Web

Restricting web-level editing blocks creating new topics, changing topics or attaching files.

The same rules apply as for restricting topics, with these additions:

Restricting Rename Access

You can define who is allowed to rename, move or delete a topic, or rename a web.

Deny Renaming by Topic

To allow a user to rename, move or delete a topic, they also need write (editing) permission. They also need write access to change references in referring topics.

Deny Renaming by Web

You can define restrictions of who is allowed to rename a DENX web.

The same rules apply as for topics, with these additions:

Restricting Read Access

You can define who is allowed to see a web.

Deny Viewing by Topic

ALERT! Technically it is possible to restrict read access to an individual topic based on DENYTOPICVIEW / ALLOWTOPICVIEW preferences variables, provided that the view script is authenticated. However this setup is not recommended since all content is searchable within a web - a search will turn up view restricted topics.

Deny Viewing by Web

You can define restrictions of who is allowed to view a DENX web. You can restrict access to certain webs to selected Users and Groups, by:

Obfuscate Webs

The idea is to keep a web hidden by not publishing its URL and by preventing the all webs search option from accessing obfuscated webs. Do so by enabling the NOSEARCHALL variable in WebPreferences:

This setup can be useful to hide a new web until content its ready for deployment.

ALERT! Obfuscating webs is insecure, as anyone who knows the URL can access the web.

Authenticate all Webs and Restrict Selected Webs

Use the following setup to authenticate users for topic viewing in all webs and to restrict access to selected webs:

  1. Restrict view access to selected Users and Groups. Set one or both of these variables in its WebPreferences topic:
    • Set DENYWEBVIEW = < list of Users and Groups >
    • Set ALLOWWEBVIEW = < list of Users and Groups >
    • Note: DENYWEBVIEW is evaluated before ALLOWWEBVIEW. Access is denied if the authenticated person is in the DENYWEBVIEW list, or not in the ALLOWWEBVIEW list. Access is granted in case DENYWEBVIEW and ALLOWWEBVIEW is not defined.
  2. Hide the web from an "all webs" search. Enable this restriction with the NOSEARCHALL variable in its WebPreferences topic:
    • Set NOSEARCHALL = on
  3. Add view to the list of authenticated scripts in the .htaccess file.

HELP This method only works if the view script is authenticated, which means that all Users have to login, even for read-only access. (An open guest account, like TWikiGuest, can get around this, allowing anyone to login to a common account with, for example, view-only access for public webs.) TWikiInstallationGuide has more on Basic Authentication, using the .htaccess file.

Authenticate and Restricting Selected Webs Only

Use the following setup to provide unrestricted viewing access to open webs, with authentication only on selected webs:

  1. Restrict view access to selected Users and Groups. Set one or both of these variables in its WebPreferences topic:
    • Set DENYWEBVIEW = < list of Users and Groups >
    • Set ALLOWWEBVIEW = < list of Users and Groups >
    • Note: DENYWEBVIEW is evaluated before ALLOWWEBVIEW. Access is denied if the authenticated person is in the DENYWEBVIEW list, or not in the ALLOWWEBVIEW list. Access is granted in case DENYWEBVIEW and ALLOWWEBVIEW is not defined.
  2. Hide the web from an "all webs" search. Enable this restriction with the NOSEARCHALL variable in its WebPreferences topic:
    • Set NOSEARCHALL = on
  3. Enable the $doRememberRemoteUser flag in lib/TWiki.cfg as described in TWikiUserAuthentication. DENX will now remember the IP address of an authenticated user.
  4. Copy the view script to viewauth (or better, create a symbolic link)
  5. Add viewauth to the list of authenticated scripts in the .htaccess file. The view script should not be listed in the .htaccess file.

When a user accesses a web where you enabled view restriction, DENX will redirect from the view script to the viewauth script once (this happens only if the user has never edited a topic). Doing so will ask for authentication. The viewauth script shows the requested topic if the user could log on and if the user is authorized to see that web.

ALERT! Authenticating webs is not very secure, as there is a way to circumvent the read access restriction. It can be useful in certain situations - for example, to simplify site organization and clutter, by hiding low traffic webs - but is not recommended for securing sensitive content.

Hiding Control Settings

TIP To hide access control settings from normal browser viewing, place them in comment markers.

<!--
   * Set DENYTOPICCHANGE = Main.SomeGroup
-->

The SuperAdminGroup

By mistyping a user or group name in the ALLOWTOPICCHANGE setting, it's possible to lock a topic so that no-one can edit it from a browser. To avoid this, you can create Web-based superusers:

$superAdminGroup = "TWikiAdminGroup";

-- PeterThoeny - 04 May 2002
-- MikeMannix - 12 May 2002