Access Control

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

Access Control allows you restrict access to single topics and entire webs, by individual user and by user Groups. Access control, combined with UserAuthentication, lets you easily create and manage an extremely flexible, fine-grained privilege system.

An important consideration

Open, freeform editing is the essence of WikiCulture - what makes Foswiki different and often more effective than other collaboration tools. For that reason, it is strongly recommended that the decision to restrict read or write access to a web or a topic is made with great care - the more restrictions, the less Wiki in the mix. Experience shows that unrestricted write access works very well because:
  • 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 focused.
  • In Foswiki, content is transparently preserved under revision control:
    • Edits can be undone by the administrator (per default a member of AdminGroup; see #ManagingGroups).
    • Users are encouraged to edit and refactor (condense a long topic), since there's a safety net.
As a collaboration guideline, 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).

Permissions settings of the webs on this Foswiki site

The topic SitePermissions gives you an overview of the access control settings for all your webs.

Authentication vs. Access Control

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

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

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. Groups can also be included in other Groups.

Managing Users

In standard Foswiki a user can create an account in UserRegistration. The following actions are performed:
  • WikiName, encrypted password and email address are recorded using the password manager 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 WikiUsers topic.

The default visitor name is WikiGuest. This is the non-authenticated user. By default the non-authenticated user is not permitted to edit topics. If you require anonymous editing, see UserAuthentication#IndividualScripts.

ALERT! Your local Foswiki may have an alternate user mapping manager installed which doesn't support user registration. Check with your Wiki administrator if you are in doubt.

Managing Groups

The following describes the standard Foswiki support for groups. Your local Foswiki may have an alternate group mapping manager installed. Check with your Wiki administrator if you are in doubt.

Groups are defined by group topics located in the Main web. To create a new group, visit WikiGroups. You will find a "Create a new group" link at the top which reveals a form to create a new group. Enter the name of the new group ending in Group into the "Group Name" form field and the initial members in the "Members" field. This creates a new group topic.

By default any member of a group has access rights to both adding and removing users from the group through the nice user interface. If you need to limit this access further, change the ALLOWTOPICCHANGE setting through "More Topic Action" -> "Edit topic preference settings".

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 = Main.KasabianGroup

ALERT! Foswiki has strict formatting rules. Make sure you have three spaces, an asterisk, and an extra space in front of any access control rule. See below for more information about ALLOWTOPICCHANGE.

Background: A group topic is an empty topic with 3 hidden preference settings.

  • GROUP: Comma separated list of users and/or groups
  • ALLOWTOPICCHANGE: Comma separated list of users and groups that are allowed to add and remove users from the group
  • VIEW_TEMPLATE: Always set to the value GroupView. This alters the way the topic is presented to include a nice user interface for adding and removing users.

Foswiki 1.1 introduced the smart user interface for adding and removing members of a group. Group topics from prior versions of Foswiki will still work. These have the GROUP setting visible in the topic text itself and you edit it by editing the topic. Foswiki 1.1 WikiGroups will show these old group topics with an "Upgrade Group Topic button". The administrator can upgrade an old group topic to the nice new user interface with one easy click.

The Super Admin Group

A number of Foswiki 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. The default name of this group is the AdminGroup. The system administrator may have chosen a different name for this group if your local Foswiki uses an alternate group mapping manager, but for simplicity we will use the default name AdminGroup in the rest of this topic.

You can create new administrators simply by adding them to the AdminGroup topic. For example,
  • Set GROUP = Main.ElizabethWindsor, Main.TonyBlair
A member of the Super Admin Group has unrestricted access throughout the wiki, so only trusted staff should be added to this group.

Restricting Access

Access to webs and topics is controlled by setting the values of certain preferences. These names of these preferences have the general form:

permission context mode

Where permission is ALLOW or DENY, _context is TOPIC, WEB, or ROOT, and mode is VIEW, CHANGE, or RENAME. For example, the preference ALLOWWEBCHANGE lists who is allowed to change topics in the current web.

  • 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.
  • Restricting CHANGE blocks creating new topics, changing topics or attaching files.
  • Restricting RENAME prevents renaming of topics within a web.

ALERT! 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.

ALERT! Note that ALLOWWEBxxx and DENYWEBxxx preferences can only be set in WebPreferences topics. You cannot define a site level access. Each web must be protected on their own. Subwebs inherit access settings from the parent web. See next section.

ALERT! Note that ALLOWTOPICxxx and DENYTOPICxxx preferences apply only to the topic itself.

ALERT! Be warned that some plugins may not respect access permissions.

IDEA! FINALPREFERENCES affects access controls, allowing you to prevent changes to access control settings while still allowing edit access to topics.

Controlling access to a Web

You can define restrictions on who is allowed to view a Eugene Maker Space Wiki 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). Renaming is additionally restricted by the setting of WEBRENAME in the web itself.

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 >

ALERT! Caution! Settings are always taken from the latest (current) revision of a topic. If older revisions of a topic had more restrictive access controls, they will not be used when accessing the older revision.

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 =
    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 =
    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 you 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.

ALERT! If the same setting is defined multiple times the last one overrides the previous. They are not OR'ed together.

ALERT! Setting to an empty value 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 Foswiki. A method to upgrade will be provided. Please read the release notes carefully when you upgrade.

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

Controlling access to attachments

Attachments are referred to directly, and are not normally indirected via Foswiki scripts. This means that the above instructions for access control will not apply to attachments. It is possible that someone may inadvertently publicise a URL that they expected to be access-controlled.

The easiest way to apply the same access control rules for attachments as apply to topics is to use the Apache mod_rewrite module, and configure your webserver to redirect accesses to attachments to the Foswiki viewfile script. For example,

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

    RewriteEngine on
    RewriteCond %{REQUEST_URI} !^/+foswiki/+pub/+System/+.+
    RewriteRule ^/+foswiki/+pub/+([^/]+)((/+([^/]+))+)/+(.+) /foswiki/bin/viewfile/$1/$2?filename=$5 [L,PT]

That way all the controls that apply to the topic also apply to attachments to the topic. Other types of webserver have similar support.

ALERT! Images embedded in topics will load much slower since each image will be delivered by the viewfile script.

Controlling who can manage top-level webs

Top level webs are a special case, because they don't have a parent web with a WebPreferences. So there has to be a special control just for the root level.
  • You can define these settings in the SitePreferences topic, preferably towards the end of the topic:
    • 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 Foswiki evaluates ALLOW/DENY settings

When deciding whether to grant access, Foswiki 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.

ALERT! Settings are only read from the most current (latest) revision of a topic. Settings from older revisions are never used, even when viewing an older revision with the rdiff script

  1. If the user is an administrator
    • 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.
      ALERT! 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 setting the NOSEARCHALL setting in WebPreferences:
  • Set NOSEARCHALL = on

TIP Setting NOSEARCHALL to any value other than the empty string will hide a web. Setting NOSEARCHALL = off will have the same effect as setting it to on

This setup can be useful to hide a new web until content its ready for deployment, or to hide view access restricted webs.

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

Restrict Access to a whole Foswiki site

For a firewalled Foswiki, e.g. an intranet wiki or extranet wiki, you want to allow only invited people to access your Foswiki. In this case, enable user authentication with ApacheLogin and lock down access to the whole bin and 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.

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

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. Requires UserAuthentication to be enabled.

  1. The simple way is to add this to WebPreferences in all webs.
    • Set DENYWEBVIEW = WikiGuest
  2. Restrict view access to selected users and groups. Set one or both of these settings in its WebPreferences topic:
    • 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.

In rare cases it may be required to authenticate the view script. This can in some cases have a dramatic performance hit because the webserver must re-authenticate for every page view.

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

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 UserAuthentication to be enabled.

  1. Restrict view access to selected users and groups. Set one or both of these settings 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.

Show control settings

You can list the access controls affecting a topic using the %SHOWPREFERENCE{}% macro in the topic, thus:
%SHOWPREFERENCE{"DENYWEBVIEW,ALLOWWEBVIEW,DENYWEBCHANGE,ALLOWWEBCHANGE,DENYWEBRENAME,ALLOWWEBRENAME"}%
For this topic, this displays:
  • Set DENYWEBVIEW = ""
  • Set ALLOWWEBVIEW = ""
  • Set DENYWEBCHANGE = ""
  • Set ALLOWWEBCHANGE = "%USERSWEB%.AdminGroup"
    • ALLOWWEBCHANGE was defined in System.WebPreferences
  • Set DENYWEBRENAME = ""
  • Set ALLOWWEBRENAME = "%USERSWEB%.AdminGroup"
    • ALLOWWEBRENAME was defined in System.WebPreferences

Hide control settings

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 = Main.SomeGroup==
==-->==


Related Topics: AdminDocumentationCategory, UserAuthentication
Topic revision: r1 - 12 Sep 2009 - 02:10:01 - ProjectContributor
 

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