Forbid certain users to do certain actions by configuration

You may have an unruly registered users (e.g. a crawler program) who don't follow the rules while you don't have control over such users. And the web application container in which TWiki is installed may be managed by somebody else and you don't have tight and quick control.

To cope with such situations, certain users can be forbidden certain scripts by setting {ForbidUserAction}. A good example is worth more than a lengthy explanation, so here it is:

$TWiki::cfg{ForbidUserAction} = '
    AggresiveCrawler: edit, oops, search;
    ReadOnlyUser:     !view, viewfile;
    TotallyForbidden: !nothing;
';

• AggresiveCrawler is forbidden edit, oops, and search scripts.
• ReadOnlyUser is permitted view and viewfile but forbidden the others.
  • If a script list is preceded by !, only the listed scripts are permitted for the user. ! at the beginning of the list negates the list.
• TotallyForbidden is forbidden all actions.
  Here's the logic. There is no script named nothing, which means all scripts don't match "nothing", hence all scripts are forbidden.

• Spaces, tabs, new lines are ignored
• It consists of semicolon separated list of per-user specifications
• A specification consists of a user name, colon, and a comma separated list of scripts
• A user name needs to be in the canonical form. In most cases the canonical user name is the same as the wiki name. But if you are using non-standard user mapping, the canonical user name of a user is different from the wiki name.

• Set ALLOWWEBCHANGE = USER:buzz, LDAPGROUP:foo-bar

• • Edits can easily be rolled back to a previous revision if needed.

• Avoid creating view-only topics (if you can read it, you should be able to contribute to it).

• Each request topic has a form field "Requestor", which has the wiki name of the requestor

Avoiding vulnerability

By default, user level preferences are read before web level preferences. This means a user can set a preferences variable at the user level and finalise it. To prevent this sort of attack, you need to harden your web or site by disabling user preferences by e.g. having the following line on lib/LocalSite.cfg

$TWiki::cfg{DemoteUserPreferences}= 1;

   * Set DENYUSERPREFEENCES = all

   * Set OVERRIDABLEPREDEFINEDVARIABLES =

Configuring access control for topics of a certain name in all webs

You may need to restrict access to topics of a certain name in all webs. For example, there might be an add-on refering to a certain topic of all webs. And the add-on does things only administrators are supposed to do. In that case, change to the topic needs to be restricted only to administrators and must not be overridable.

Let's say there is AutomationAddOn which refers to WebAutomation of all webs. And WebAutomation needs to be modifable only by administrators. That can be achieved by the following configuration.

$TWiki::cfg{Access}{Topic}{WebAutomation} = {
    DENYCHANGE => 'Main.AllUsersGroup',
};

In addition to ALLOWCHANGE, you can sepcify DENYCHANGE, ALLOWVIEW, DENYVIEW, ALLOWRENAME, and DENYRENAME as follows.

$TWiki::cfg{Access}{Topic}{SpecialTopic} = {
    DENYVIEW  => 'JoeSchmoe',
    ALLOWVIEW => 'FooGroup',
};

$TWiki::cfg{Access}{Topic}{TOPICNAME} has precedence over DENYTOPIC* and ALLOWTOPIC*. For example, if the configuration for WebAutomation is there as above, there is no way to allow non-adminsitrators to change the WebAutomation topic of any web.

As a way to configure access control, this may look crude. The reason why configured this way is that this can be part of plugin/add-on/contrib's configuration. For example, Config.spec of AutomationAddOn would have the following lines, with which proper access control to WebAutomation topics is implemented without the administrator knowing it.

$TWiki::cfg{Access}{Topic}{WebAutomation} = {
    DENYCHANGE => 'Main.AllUsersGroup',
};

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

Web	Sitemap	VIEW		CHANGE		RENAME
	Listed	DENY	ALLOW	DENY	ALLOW	DENY	ALLOW
Main	on
TWiki	on				TWikiAdminGroup		TWikiAdminGroup
AFNOG	on
Embedded_Systems	on
IoT_Course_English	on
IoT_Course_French	on
Sandbox	on

Please Note:

• A blank in the the above table may mean either the corresponding control is absent or commented out or that it has been set to a null value. The two conditions have dramatically different and possibly opposed semantics.
• TWikiGuest is the guest account - used by unauthenticated users.
• The TWiki web must not deny view to TWikiGuest; otherwise, people will not be able to register.

Allowing public access to specific topics in a restricted web

• Set ALLOWTOPICVIEW = Main.AllUsersGroup

• Set ALLOWTOPICVIEW = Main.AllAuthUsersGroup

• Set ALLOWTOPICOPERATION = Main.AllUsersGroup

Empty values in access control variables

Setting an empty value to an access control variable is the same as not setting at all:

• Set ALLOWTOPICVIEW =

Since TWiki 4.0 and prior to TWiki 6.0 setting DENYTOPICVIEW, DENYTOPICCHANGE, or DENYTOPICRENAME to an empty value meant "do not deny anyone regardless of the corresponding ALLOWTOPICX", which is no longer the case. Back then, setting an empty value to DENYTOPICX was the only way to open up a topic to everybody in a restricted web. Now that we have AllUsersGroup and AllAuthUsersGroup, there is no need for that behaviour, which caused a lot of confusion and debate.

1. If DENYTOPIC is set to empty ( i.e. Set DENYTOPIC = )
   • the access control setting is ignored.
     Attention: The spec changed in TWiki-6.0; access was permitted in earlier TWiki releases.

Allowing web creation by user mapping manager

There are cases where DENYROOTCHANGE, ALLOWROOTCHANGE, DENYWEBCHANGE, and ALLOWWEBCHANGE, and DENYWEBCHANGE are not capable enough to implement web creation permission you want. To cope with such cases, when a new web is created, the canCreateWeb($cUID, $web) method of the user mapping manager is called if the method exists. If it returns true, TWiki goes ahead and create the web without checking access control variables. Please read AllowWebCreateByUserMappingManager for more details.

User masquerading

There are cases where it's handy to access TWiki on behalf of somebody else retaining a trace of your real identity rather than completely becoming a different user. We call it user masquerading. TWiki provides a framework to implement that. Please read UserMasquerading for more information.

This is an advanced feature and not many TWiki sites are using, but there is a part in the following section mentioning it, it's mentioned here.

Dynamic access control

This feature is regarded experimental. There are pitfalls and vulnerability. Before using this feature, please read this entire section through carefully.

You may want to restrict access dynamically -- based on topic name, a form field value, or some combination of factors. To cope with such situations, the dynamic access control mechanism is provided. If you set DYNAMIC_ACCESS_CONTROL 'on' at WebPreferences of the web, TWiki variables in access control variables mentioned above are expanded.

Example 1 - restriction based on topic name

Let's assume you need to restrict changes only to the CroniesGroup members excep with topics whose name ends with Public, which need be changed by anybody. That is achieve by the following settings on WebPrefences.

   * Set DYNAMIC_ACCESS_CONTROL = on
   * Set ALLOWWEBCHANGE = %IF{"'%CALCULATE{$SUBSTRING(%TOPIC%, -6, 6)}%' = 'Public'" then="%WIKINAME%" else="CroniesGroup"}%

Example 2 - restriction based on form field

Let's assume:

• a web storing requests on topics whose name starts with ReqEnt
• Each request topic has a form field "Requstor", which has the wiki name of the requestor
• Users can view only requests they created
• The members of the SupportGroup mail group can view all requests

   * Set DYNAMIC_ACCESS_CONTROL = on
   * Set ALLOWWEBVIEW = %IF{"'%CALCULATE{$SUBSTRING(%TOPIC%, 1, 6)}%' = 'ReqEnt' and '%FORMFIELD{Requestor}%' != '%WIKINAME%'" then="SupportGroup" else="%WIKINAME%"}%

Specifically the following access control variables are subject to TWiki variable expansion in their values.

• DENYTOPIC* (e.g. DENYTOPICVIEW, DENYTOPICCHANGE)
• ALLOWTOIPC*
• DENYWEB*
• ALLOWWEB*

Dynamic access control in accessing a different web's topic

Let's assume WebA has the following lines on WebPreferences.

   * Set DYNAMIC_ACCESS_CONTROL = on
   * Set MEMBERS = JaneSmith, JoeSchmoe
   * Set ALLOWWEBVIEW = %MEMBERS%

You may think the following lines cheat the access control on WebA but actually not.

   * Set MEMBERS = %WIKINAME%
%INCLUDE{WebA.TopicB}%

Topic level dynamic access control

On a topic, it's possible to use a variable defined on the topic for topic level access restriction. E.g.

   * Set MEMBERS = JaneSmith, JoeSchmoe
   * Set ALLOWTOPICVIEW = %MEMBERS%

Dynamic access control and user masquerading

Your user mapping handler may be providing the UserMasquerading feature. In that case, you expect dynamic access control to just work when user masquerading is in effect. Otherwise, you cannot test if your dynamic access control configuration is working as expected on your own.

Dynamic access control does work as expected even if user masquerading is in effect. For that, the following things are happening under the hood.

Let's think about Example 2 mentioned above. When you masquerading as SomebodyElse, you need to be able to see SomebodyElse's requests only. In the access control setting, a form field value is compared with %WIKINAME%. While user masquerading is in effect, your wiki name is YourNameOnBehalfOfSomebodyElse. It cannot match the form field value.

To make dynamic access control work under these circumstances, variable expansion for dynamic access control is skewed as follows. Specifically, the following variables are expanded to the value of SomeboyElse's rather than YourNameOnBehalfOfSomebodyElse's.

• WIKINAME
• USERNAME
• WIKIUSERNAME

Vulnerability

It's possible to redefine function tags such as %IF{...}% in your personal preferences. In a future release of TWiki, a way to prevent function tags from being overridden by personal preferences will be provied. But until then, you need to be well aware of this vulnerability.

Disabling dynamic access control

You may not be comfortable with dynamic access control because it may slow things down. Or you may not want to be bothered by questions raised by users about it. If so, you can disable it by setting DYNAMIC_ACCESS_CONTROL 'off' and then finalizing at the local site level. (cf. TWikiVariables#Setting_Preferences_Variables)

Customizing "access denied" message

When access is denied, a page as follows is displayed:

You may want to customize the passage annotated in the red rectangle. For example, with a web restricting access, you may want to show the link to an access request form.

You can achieve that by setting TOPIC_ACCESS_CONTACT varialbe on WebPreferences. e.g.

   * Set TOPIC_ACCESS_CONTACT = If you need to access this site, please apply [[Main.AccessForm][here]]

Custom user/group notations

You can have custom user/group notations such as USER:userid and LDAPGROUP:group-name and use them for access control. For example:

   * Set ALLOWWEBCHANGE = UID:buzz, LDAPGROUP:foo-bar

• It is recommended to use TWiki:TWiki/ApacheConfigGenerator to generate the Apache config file for your TWiki.

1. Install TWiki Behind Firewall:

The firewall takes care of giving access to TWiki to authorized people only. This is a typical setup for a company wiki. As for TWiki configuration, no special setup is needed.

2. Extranet TWiki Using Template Login:

All TWiki content (pages and attachments) need to be access controlled. The Template Login allows users to login and logout. Only logged in users can access TWiki content.

Configuration: Follow the default setup, then change these configure settings:

• Secure attachments as documented. The TWiki:TWiki.ApacheConfigGenerator is useful to get the setting right.
• Require authentication for all TWiki scripts except backuprestore, configure, login, logon and resetpasswd with the following configure setting:
  $TWiki::cfg{AuthScripts} = 'attach, changes, edit, manage, oops, preview, rdiff, rdiffauth, register, rename, rest, save, search, twiki_cgi, upload, statistics, view, viewauth, viewfile';
• When you install additional plugins make sure to add scripts they might introduce also to twiki/bin also to the {AuthScripts} configure setting.
  Attention: Some scripts of additional plugins might not be aware of TWiki's template login. Test all new scripts with a non-authenticated user!

3. Extranet TWiki Using Apache Login:

All TWiki content (pages and attachments) need to be access controlled. The Apache Login does not offer a logout; typically the browser needs to be restarted to logout. Only logged in users can access TWiki content.

Configuration: Enable user authentication with ApacheLogin and lock down access to the whole twiki/bin and twiki/pub directories to all but valid users. In the Apache config file for TWiki (twiki.conf or .htaccess), replace the <FilesMatch "(attach|edit|... section with this:

• In all three options, content can be restricted selectively with ALLOWWEBVIEW and other access control settings documented above. See also the next quick recipe.
• In the extranet setup, someone with access to the site needs to register new users. If you still want public users to be able to register automatically follow TWiki:TWiki.RegisterOnViewRestrictedSite.

• A user profile page with the WikiName of the user is created in the Main web.

• Set GROUP = SomeUser, OtherUser, SomeGroup

• Set ALLOWTOPICCHANGE = MarketingGroup

• Set GROUP = RobertCailliau, TimBernersLee

• Set ALLOWWEBVIEW = Main.MarketingGroup

• Set ALLOWTOPICVIEW = Main.MarketingExecGroup

• You can define these settings in the Main.TWikiPreferences topic, preferable towards the end of the topic:

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.

Note: Obfuscating a web without view access control is very insecure, as anyone who knows the URL can access the web.

Read-only Skin Mode

It is possible to turn the PatternSkin and TopMenuSkin into read-only mode by removing the edit and attach controls (links and buttons). This is mainly useful if you have TWiki application pages or dashboards where you do not want regular users to change content. The read-only skin mode is not a replacement for access control; you can use it in addition to access control. Details at PatternSkinCustomization#ReadOnlySkinMode.

Securing File Attachments

The preferred method to secure attachments is by editing the twiki.conf file to include:

• You can use TWiki:TWiki/ApacheConfigGenerator to generate the Apache config file for TWiki.
• You will need to restart your Apache server after this change.
• Images embedded in topics will load slower since attached images will also be delivered by the viewfile script. The TWiki web and Sandbox web are excluded for performance reasons.
• As an alternative to editing the twiki.conf file used by Apache, you can make the same change directly to the .htaccess file in the /twiki/bin directory.
• The viewfile script sets the mime type based upon file name suffix. Unknown types are served as text/plain which can result in corrupt files.

The setting to an empty has caused confusion and great debate and it has been decided that the empty setting syntax will be replaced by something which is easier to understand in a later version of TWiki. A method to upgrade will be provided. Please read the release notes carefully when you upgrade.

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

TWiki Access Control

• • Edits can be undone by the administrator (per default a member of TWikiAdminGroup; see #ManagingGroups).

• A user home page with the WikiName of the user is created in the Main web.
• The user is added to the TWikiUsers topic.

• Set GROUP = Main.SomeUser, Main.OtherUser, Main.SomeGroup

• Set ALLOWTOPICCHANGE = Main.KasabianGroup

• Set GROUP = Main.ElizabethWindsor, Main.TonyBlair

• Restricting VIEW blocks viewing and searching of content. When you restric VIEW to a topic or web, this also restricts INCLUDE and Formatted SEARCH from showing the content of the topics.

• • Set ALLOWWEBCHANGE = TWikiAdminGroup, TWikiRegistrationAgent

• You can define these settings in the Main.%TWIKIPREFSTOPIC% topic, preferable towards the end of the topic:

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 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 <FilesMatch "(attach|edit|... section with this:

<FilesMatch ".*">
       require valid-user
</FilesMatch>

If needed, you can further restrict access to selected webs with ALLOWWEBVIEW and other access control settings.

Note: With this configuration, someone with access to the site needs to register new users.

1. Set require valid-user on your view script in .htaccess or the appropriate Apache .conf file. As of 4.x, this looks like: FilesMatch "(attach|edit|manage|rename|save|view|upload|mail|logon|.*auth).*" (normally view is not in that list).

• • 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.

1. If you still want public users to be able to register automatically follow TWiki:TWiki.RegisterOnViewRestrictedSite.

• • 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.

• • Edits can be undone by the administrator (per default a member of TWikiAdminGroup; see #ManagingGroups).

Groups are defined by group topics located in the Main web. To create a new group, visit 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 ALLOWTOPICCHANGE = Main.KasabianGroup

You can create new administrators simply by adding them to the TWikiAdminGroup topic. For example,

• 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.

• • Set DENYWEBRENAME = < comma-delimited list of Users and Groups >
  • Set ALLOWWEBRENAME = < comma-delimited list of Users and Groups >

Creation and renaming of sub-webs is controlled by the WEBCHANGE setting on the parent web (or ROOTCHANGE for root webs). Renaming is additionally restricted by the setting of WEBRENAME in the web itself.

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.

• • Set DENYTOPICRENAME = < comma-delimited list of Users and Groups >
  • Set ALLOWTOPICRENAME = < comma-delimited list of Users and Groups >

• Set ALLOWTOPICVIEW =
  This means the same as not setting it at all. (This was documented wrong in versions 4.0.X, 4.1.0 and 4.1.1)

• Set DENYTOPICVIEW =
  Since TWiki 4.0 this means do not deny anyone the right to view this topic. If DENYTOPICVIEW is set to an empty value anyone has access even if ALLOWTOPICVIEW or ALLOWWEBVIEW is defined. This allows to have very restrictive default access rights to an entire web and still allow individual topics to have more open access.

The same rules apply to ALLOWTOPICCHANGE/DENYTOPICCHANGE and APPLYTOPICRENAME/DENYTOPICRENAME. Setting ALLOWTOPICCHANGE or ALLOWTOPICRENAME to en empty value means the same as not defining it. Setting DENYTOPICCHANGE or DENYTOPICRENAME to an empty value means that anyone can edit or rename the topic.

The setting to an empty has caused confusion and great debate and it has been decided that the empty setting syntax will be replaced by something which is easier to understand in the 4.2 version of TWiki. A method to upgrade will be provided. Please read the release notes carefully when you upgrade.

See "How TWiki evaluates ALLOW/DENY settings" below for more on how ALLOW and DENY interacts.

Controlling who can manage top-level webs

1. If the user is an administrator

• • access is PERMITTED i.e no-one is denied access to this topic.
    Attention: Use this with caution. This is deprecated and will likely change in the next release.

1. If DENYWEB is set to a list of wikinames

• You can define these settings in any topic, preferable towards the end of the topic:

Controlling who can create top-level webs

• You can define these settings in the Main.%TWIKIPREFSTOPIC% topic, preferable towards the end of the topic:
  • Set DENYROOTCHANGE = < comma-delimited list of Users and Groups >
  • Set ALLOWROOTCHANGE = < comma-delimited list of Users and Groups >

Tip:

Alternatively, place them in HTML comment markers, but this exposes the access setting during ordinary editing.

An Important Control Consideration

• Peer editing - the ability for anyone to rearrange all content on a page - keeps topics focused.

Permissions settings of the webs on this TWiki site

Web	Sitemap	VIEW		CHANGE		RENAME
	Listed	DENY	ALLOW	DENY	ALLOW	DENY	ALLOW
Main	on
TWiki	on				TWikiAdminGroup		TWikiAdminGroup
AFNOG	on
Embedded_Systems	on
IoT_Course_English	on
IoT_Course_French	on
Sandbox	on

Please Note:

• A blank in the the above table may mean either the corresponding control is absent or commented out or that it has been set to a null value. The two conditions have dramatically different and possibly opposed semantics.
• TWikiGuest is the guest account - used by unauthenticated users.
• The TWiki web must not deny view to TWikiGuest; otherwise, people will not be able to register.

Note: Above table comes from SitePermissions

• WikiName and encrypted password are recorded using the password manager if authentication is enabled.

• Set GROUP = Main.SomeUser, Main.OtherUser, Main.SomeGroup

• Set ALLOWTOPICCHANGE = Main.TWikiAdminGroup

The Super Admin Group

• Set GROUP= Main.ElizabethWindsor, Main.TonyBlair

Restricting Access

• Restricting VIEW blocks viewing and searching of content.
• Restricting CHANGE blocks creating new topics, changing topics or attaching files.
• Restricting RENAME controls who is allowed to rename, move or delete a topic.
  • To rename, move or delete a topic, the user also also needs VIEW and CHANGE permission. They also need CHANGE access to change references in any referring topics (though the rename can proceed without this access), and CHANGE access to the target topic.
• Restricting MANAGE controls access to certain management functions, such as 'create web'. It must be set in the TWiki web.

Controlling access to a Web

• 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 >

Be careful with empty values for any of these. In older versions of TWiki,

• Set ALLOWWEBVIEW =

• Set DENYWEBVIEW =

Controlling access to a Topic

• You can define these settings in the WebPreferences 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. In older versions of TWiki,

• Set ALLOWTOPICVIEW =

• Set DENYTOPICVIEW =

Controlling access to Attachments

  ScriptAlias /twiki/bin/ /filesystem/path/to/twiki/bin/
  Alias /twiki/pub/       /filesystem/path/to/twiki/pub/

How TWiki evaluates ALLOW/DENY settings

1. If the user is a super-user
   • 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
4. If ALLOWTOPIC is set
   1. people in the list are PERMITTED
   2. everyone else is DENIED
      • Note that this means that setting ALLOWTOPIC to empty denies access to everyone except admins (unless DENYTOPIC is also set to empty, as described above)
5. If DENYWEB is set to a list of wikiname
   • 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
     • Note that setting ALLOWWEB to empty denies access to everyone except admins
7. If you got this far, access is PERMITTED

Access Control quick recipes

Obfuscating Webs

Authenticate all Webs and Restrict Selected Webs

Authenticate and Restrict Selected Webs Only

Hide Control Settings

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

TWiki:TWiki.TWikiAccessControlSupplement

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

Authentication vs. Access Control

Authentication: Identifies who a user is based on a login procedure. See TWikiUserAuthentication.

Access control: Restrict access to content based on users and groups once a user is identified.

• WikiName and encrypted password are recorded in .htpasswd if authentication is enabled.
• A confirmation e-mail is sent to the user.
• A user home page with the WikiName of the user is created in the Main web.
• The user is added to the TWikiUsers topic.

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.

• • 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.

• • 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.

<style="background-color:#f5f5f5"> <!--
   * Set DENYTOPICCHANGE = Main.SomeGroup
-->

Restricting Read Access

Deny Viewing by Topic

Deny Viewing by Web

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

• obfuscating webs: Insecure but handy method to hide new webs until content is ready for deployment.
• 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.

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:

• Set NOSEARCHALL = on

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

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:

1. Hide the web from an "all webs" search. Enable this restriction with the NOSEARCHALL variable in its WebPreferences topic:

1. Add view to the list of authenticated scripts in the .htaccess file.

Authenticate and Restricting Selected Webs Only

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 >
2. Hide the web from an "all webs" search. Enable this restriction with the NOSEARCHALL variable in its WebPreferences topic:
   • Set NOSEARCHALL = on

1. 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, TWiki 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.

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.

• Peer influence is enough to ensure that only relevant content is posted.

• Peer editing - the ability for anyone to rearrange all content on a page - keeps topics focussed.

• In TWiki, content is transparently preserved under revision control:

• Create broad-based Groups (for more and varied input), and...
• Avoid creating view-only Users (if you can read it, you should be able to contribute to it).

• 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.

1. Edit TWikiGroups by entering a new topic with a name that ends in Group. Example:

1. 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 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, with a comma-delimited list. Example:

• 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 DENYWEBCHANGE = < list of Users and Groups >
  • Set ALLOWWEBCHANGE = < list of Users and Groups >

• • Set DENYTOPICRENAME = < list of Users and Groups >
  • Set ALLOWTOPICRENAME = < list of Users and Groups >

• DENYTOPICCRENAME defines Users or Groups that are not allowed to rename the topic. It is a comma delimited list of Users and Groups. Example:

• ALLOWTOPICRENAME defines Users or Groups that are allowed to rename the topic. It is a comma delimited list of Users and Groups. Example:

• • Set DENYWEBRENAME = < list of Users and Groups >
  • Set ALLOWWEBRENAME = < list of Users and Groups >

• Set DENYWEBVIEW = < list of Users and Groups >
• Set ALLOWWEBVIEW = < list of Users and Groups >