TWiki allows to define some restrictions of who is allowed to make changes and attach files to topics.

IMPORTANT NOTE: Think twice before restricting write access to a web or a topic, because an open system where everybody can contribute is the essence of the WikiCulture. Experience shows that unrestricted write access works very well because:

• There is enough peer pressure to post only conform content.
• Content does not get lost because topics are under revision control.
• A topic revision can be undone by a member of the TWikiAdminGroup in case needed.

Users and Groups

Access control is based on users and groups.

Users are defined by the user topics in the Main web, i.e. TWikiGuest

• Users can be authenticated using basic authentication or SSL. Installation Notes has more.

Groups are defined by group topics in the Main web, i.e. TWikiAdminGroup

• A group topic name must end in ...Group
• The group topic should define these two variables:
  • Set GROUP = < list of users and groups >
  • Set ALLOWTOPICCHANGE = < list of users and groups >
• GROUP defines the members of the group; it is a comma delimited list of users and other groups. Example:
      * Set GROUP = Main.SomeUser, Main.OtherUser, Main.SomeOtherGroup
• 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, i.e.
      * Set ALLOWTOPICCHANGE = Main.TWikiAdminGroup
  for the TWikiAdminGroup topic. (This is to prevent users not in the group from editing the topic and gaining unauthorized membership to the group.)

Access Control for Individual Topics

You can define some restrictions of who is allowed to make changes and attach files to a topic.

Define one or both of these variables in a topic, preferably at the end of the topic:

• Set DENYTOPICCHANGE = < list of users and groups >
• Set ALLOWTOPICCHANGE = < list of users and groups >

DENYTOPICCHANGE defines users or groups that are not allowed to make changes to the topic. It is a comma delimited list of users and groups. Example:
    * Set DENYTOPICCHANGE = Main.SomeBadBoy, Main.SomeBadGirl, Main.SomeHackerGroup

ALLOWTOPICCHANGE defines users or groups that are allowed to make changes to the topic. It is a comma delimited list of users and groups. Example:
    * Set ALLOWTOPICCHANGE = Main.SomeGoodGuy, Main.SomeGoodGirl, Main.TWikiAdminGroup

DENYTOPICCHANGE is evaluated before ALLOWTOPICCHANGE. Access is denied if the authenticated person is in the DENYTOPICCHANGE list, or not in the ALLOWTOPICCHANGE list. Access is granted in case DENYTOPICCHANGE and ALLOWTOPICCHANGE is not defined.

Access Control per TWiki Web

You can define some restrictions of who is allowed to make changes and attach files to topics or create new topics in a TWiki web.

Define one or both of these variable in the WebPreferences topic:

• Set DENYWEBCHANGE = < list of users and groups >
• Set ALLOWWEBCHANGE = < list of users and groups >

The same rules apply like the one for Access Control for Individual Topics; with these additions:

• DENYTOPICCHANGE (in topic) overrides DENYWEBCHANGE (in WebPreferences)
• ALLOWTOPICCHANGE (in topic) overrides ALLOWWEBCHANGE (in WebPreferences)

Related topics: TWikiPreferences, WebPreferences (in every web), TWikiAdminGroup, TWikiGroups

-- PeterThoeny - 28 Oct 2000