# TWiki Access Control _Restricting read and write access to topics and webs, by Users and groups_ TWiki Access Control allows you restrict access to single topics and entire webs, by individual user and by user Groups. Access control, combined with [[TWikiUserAuthentication]], lets you easily create and manage an extremely flexible, fine-grained privilege system. **_%T% Tip:_** TWiki:TWiki.TWikiAccessControlSupplement on TWiki.org has additional documentation on access control.
**%USERSWEB%**
web. To create a new group, visit %USERSWEB%.TWikiGroups and enter the name of the new group ending in **Group**
into the "new group" form field. This will create a new group topic with two important settings:
- **Set GROUP = < list of Users and/or Groups >**
- **Set ALLOWTOPICCHANGE = < list of Users and/or Groups >**
The GROUP setting is a comma-separated list of users and/or other groups. Example:
- **Set GROUP = %USERSWEB%.SomeUser, %USERSWEB%.OtherUser, %USERSWEB%.SomeGroup**
The ALLOWTOPICCHANGE setting 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 KasabianGroup topic write:
- **Set ALLOWTOPICCHANGE = %USERSWEB%.KasabianGroup**
**_%X% Note:_** TWiki has strict formatting rules. Make sure you have three spaces, an asterisk, and an extra space in front of any access control rule.
### The Super Admin Group
A number of TWiki functions (for example, renaming webs) are only available to administrators. Administrators are simply users who belong to the **SuperAdminGroup**. This is a standard user group, the name of which is defined by \{SuperAdminGroup\} setting in [configure](http://www.dementia.org/twiki/configure). The default name of this group is the `TWikiAdminGroup`. The system administrator may have chosen a different name for this group if your local TWiki uses an alternate group mapping manager but for simplicity we will use the default name TWikiAdminGroup in the rest of this topic.
You can create new administrators simply by adding them to the %USERSWEB%.TWikiAdminGroup topic. For example,
- **Set GROUP = %USERSWEB%.ElizabethWindsor, %USERSWEB%.TonyBlair**
A member of the Super Admin Group has unrestricted access throughout the TWiki, so only trusted staff should be added to this group.
## Restricting Access
You can define who is allowed to read or write to a web or a topic. Note that some plugins may not respect access permissions.
- Restricting VIEW blocks viewing and searching of content. When you restric VIEW to a topic or web, this also restricts [[INCLUDE|Main/VarINCLUDE]] and [[Formatted SEARCH|Main/FormattedSearch]] from showing the content of the topics.
- Restricting CHANGE blocks creating new topics, changing topics or attaching files.
- Restricting RENAME prevents renaming of topics within a web.
Note that there is an important distinction between CHANGE access and RENAME access. A user can CHANGE a topic, but thanks to version control their changes cannot be lost (the history of the topic before the change is recorded). However if a topic or web is renamed, that history may be lost. Typically a site will only give RENAME access to administrators and content owners.
### Controlling access to a Web
You can define restrictions on who is allowed to view a %WIKITOOLNAME% web. You can restrict access to certain webs to selected Users and Groups, by:
- **authenticating all webs and restricting selected webs:** Topic access in all webs is authenticated, and selected webs have restricted access.
- **authenticating and restricting selected webs only:** Provide unrestricted viewing access to open webs, with authentication and restriction only on selected webs.
- You can define these settings in the [[WebPreferences]] topic, preferable towards the end of the topic:
- **Set DENYWEBVIEW = < comma-delimited list of Users and Groups >**
- **Set ALLOWWEBVIEW = < comma-delimited list of Users and Groups >**
- **Set DENYWEBCHANGE = < comma-delimited list of Users and Groups >**
- **Set ALLOWWEBCHANGE = < comma-delimited list of Users and Groups >**
- **Set DENYWEBRENAME = < comma-delimited list of Users and Groups >**
- **Set ALLOWWEBRENAME = < comma-delimited list of Users and Groups >**
If your site allows hierarchical webs, then access to sub-webs is determined from the access controls of the parent web, plus the access controls in the sub-web. So, if the parent web has **ALLOWWEBVIEW**
set, this will also apply to the subweb. Also note that you will need to ensure that the parent web's **FINALPREFERENCES**
does not include the access control settings listed above. Otherwise you will not be able override the parent web's access control settings in sub-webs.
Creation and renaming of sub-webs is controlled by the WEBCHANGE setting on the parent web (or ROOTCHANGE for [[root webs|Main/WebHome#RootWebs]]). Renaming is additionally restricted by the setting of WEBRENAME in the web itself.
**_Note:_** If you restrict access to the %USERSWEB%, make sure to add the `TWikiRegistrationAgent` so that users can register. Example:
- - **Set ALLOWWEBCHANGE = TWikiAdminGroup, TWikiRegistrationAgent**
**_Note:_** For Web level access rights Setting any of these settings to an empty value has the same effect as not setting them at all. Please note that the documentation of TWiki 4.0 and earlier versions of TWiki 4.1 did not reflect the actual implementation, e.g. an empty ALLOWWEBVIEW does _not_ prevent anyone from viewing the web, and an an empty DENYWEBVIEW does _not_ allow all to view the web.
### Controlling access to a Topic
- You can define these settings in any topic, preferable towards the end of the topic:
- **Set DENYTOPICVIEW = < comma-delimited list of Users and Groups >**
- **Set ALLOWTOPICVIEW = < comma-delimited list of Users and Groups >**
- **Set DENYTOPICCHANGE = < comma-delimited list of Users and Groups >**
- **Set ALLOWTOPICCHANGE = < comma-delimited list of Users and Groups >**
- **Set DENYTOPICRENAME = < comma-delimited list of Users and Groups >**
- **Set ALLOWTOPICRENAME = < comma-delimited list of Users and Groups >**
Remember when opening up access to specific topics within a restricted web that other topics in the web - for example, the [[WebLeftBar]] - may also be accessed when viewing the topics. The message you get when you are denied access should tell you what topic you were not permitted to access.
**Be careful** with empty values for any of these.
- **Set ALLOWTOPICVIEW = **
**Set DENYTOPICVIEW = **
**Set DENYROOTCHANGE = < comma-delimited list of Users and Groups >**
- **Set ALLOWROOTCHANGE = < comma-delimited list of Users and Groups >**
Note that you do **not** require `ROOTCHANGE` access to rename an existing top-level web. You just need `WEBCHANGE` in the web itself.
### How TWiki evaluates ALLOW/DENY settings
When deciding whether to grant access, TWiki evaluates the following rules in order (read from the top of the list; if the logic arrives at **PERMITTED** or **DENIED** that applies immediately and no more rules are applied). You need to read the rules bearing in mind that VIEW, CHANGE and RENAME access may be granted/denied separately.
1. If the user is an [[administrator|Main/WebHome#SuperAdminGroup]]
- access is **PERMITTED**.
2. If DENYTOPIC is set to a list of wikinames
- people in the list will be **DENIED**.
3. If DENYTOPIC is set to _empty_ ( i.e. `Set DENYTOPIC =` )
- access is **PERMITTED** _i.e_ no-one is denied access to this topic.%BR% %X% **_Attention:_** Use this with caution. This is **_deprecated_** and will likely change in the next release.
4. If ALLOWTOPIC is set
1. people in the list are **PERMITTED**
2. everyone else is **DENIED**
5. If DENYWEB is set to a list of wikinames
- people in the list are **DENIED** access
6. If ALLOWWEB is set to a list of wikinames
- people in the list will be **PERMITTED**
- everyone else will be **DENIED**
7. If you got this far, access is **PERMITTED**
## Access control and INCLUDE
ALLOWTOPICVIEW and ALLOWTOPICCHANGE only applies to the topic in which the settings are defined. If a topic A includes another topic B, topic A does not inherit the access rights of the included topic B.
Examples: Topic A includes topic B
- If the included topic B has ALLOWTOPICCHANGE set to block editing for a user, it does not prevent editing the including topic A.
- If the included topic B has ALLOWTOPICVIEW set to block view for a user, the user can still view topic A but he cannot see the included topic B. He will see a message _No permission to view B_
## Access Control quick recipes
### Obfuscating Webs
Another way of hiding webs is to keep them hidden by not publishing the URL and by preventing the **all webs**
search option from accessing obfuscated webs. Do so by enabling the **NOSEARCHALL**
variable in [[WebPreferences]]:
- **Set NOSEARCHALL = on**
This setup can be useful to hide a new web until content its ready for deployment, or to hide view access restricted webs.
**_%X% Note:_** Obfuscating a web without view access control is **very** insecure, as anyone who knows the URL can access the web.
### Restrict Access to Whole TWiki Site
For a firewalled TWiki, e.g. an intranet wiki or extranet wiki, you want to allow only invited people to access your TWiki. In this case, enable [[user authentication with ApacheLogin|Main/TWikiUserAuthentication#ApacheLogin]] and lock down access to the whole `twiki/bin` and `twiki/pub` directories to all but valid users. In the Apache `.htaccess` file or the appropriate `.conf` file, replace the `**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 if `DENYWEBVIEW` and `ALLOWWEBVIEW` are not defined.
3. If you still want public users to be able to register automatically follow TWiki:TWiki.RegisterOnViewRestrictedSite.
### Authenticate and Restrict Selected Webs Only
Use the following setup to provide unrestricted viewing access to open webs, with authentication only on selected webs. Requires [[TWikiUserAuthentication]] to be enabled.
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 if `DENYWEBVIEW` and `ALLOWWEBVIEW` are not defined.
### Hide Control Settings
**_%T% Tip:_** To hide access control settings from normal browser viewing, you can put them into the _topic preference settings_ by clicking the link `Edit topic preference settings` under `More topic actions` menu. Preferences set in this manner are not visible in the topic text, but take effect nevertheless. Access control settings added as topic preference settings are stored in the topic meta data and they override settings defined in the topic text.
Alternatively, place them in HTML comment markers, but this exposes the access setting during ordinary editing.
> **<!--**
>
> ** \* Set DENYTOPICCHANGE = %USERSWEB%.SomeGroup**
>
> **-->**
**_Related Topics:_** [[AdminDocumentationCategory]], [[TWikiUserAuthentication]], TWiki:TWiki.TWikiAccessControlSupplement
-- **_Contributors:_** TWiki:Main.PeterThoeny, TWiki:Main.MikeMannix, TWiki:Main.CrawfordCurrie