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h1. Fine grained permissions

Before Trac 0.11, it was only possible to define fine-grained permissions checks on the repository browser sub-system.

Since 0.11, there's a general mechanism in place that allows custom permission policy plugins to grant or deny any action on any kind of Trac resources, even at the level of specific versions of such resources.

h2. Permission Policies

h3. AuthzPolicy

An example policy based on an Authz-style system has been added. See

[trac:source:branches/0.11-stable/sample-plugins/permissions/authz_policy.py authz_policy.py] for details (current version requires >= Python 2.4). (See also [trac:source:branches/0.11-stable/sample-plugins/permissions sample-plugins/permissions] for more samples.)

 - Install "ConfigObj":http://www.voidspace.org.uk/python/configobj.html (required).

 - Copy authz_policy.py into your plugins directory.

 - Put a "authzpolicy.conf":http://swapoff.org/files/authzpolicy.conf file somewhere (preferably on a secured location on the server, not readable for others than the webuser.

 - Update your @trac.ini@:

<pre>

[trac]

...

permission_policies = [[AuthzPolicy]], [[DefaultPermissionPolicy]], [[LegacyAttachmentPolicy]]

[authz_policy]

authz_file = /some/trac/env/conf/authzpolicy.conf

[components]

...

authz_policy = enabled

</pre>

Note that the order in which permission policies are specified is quite critical, 

as policies will be examined in the sequence provided.

A policy will return either @True@, @False@ or @None@ for a given permission check.

Only if the return value is @None@ will the _next_ permission policy be consulted.

If no policy explicitly grants the permission, the final result will be @False@ 

(i.e. no permission).

For example, if the @authz_file@ contains:

<pre>

[[WikiStart@*]]

* = WIKI_VIEW

[[PrivatePage@*]]

john = WIKI_VIEW

* =

</pre>

and the default permissions are set like this:

<pre>

john           WIKI_VIEW

jack           WIKI_VIEW

# anonymous has no WIKI_VIEW

</pre>

Then: 

 - All versions of [[WikiStart]] will be viewable by everybody (including anonymous)

 - PrivatePage will be viewable only by john

 - other pages will be viewable only by john and jack

h3. mod_authz_svn-like permission policy

At the time of this writing, the old fine grained permissions system from Trac 0.10 and before used for restricting access to the repository has not yet been converted to a permission policy component, but from the user point of view, this makes little if no difference.

That kind of fine-grained permission control needs a definition file, which is the one used by Subversion's mod_authz_svn. 

More information about this file format and about its usage in Subversion is available in the "Subversion Book (Per-Directory Access Control)":http://svnbook.red-bean.com/svnbook/book.html#svn-ch-6-sect-4.4.2.

Example:

<pre>

[/]

* = r

[/branches/calc/bug-142]

harry = rw

sally = r

[/branches/calc/bug-142/secret]

harry =

</pre>

* */* = _Everyone has read access by default_

* */branches/calc/bug-142* = _harry has read/write access, sally read only_

* */branches/calc/bug-142/secret* = _harry has no access, sally has read access (inherited as a sub folder permission)_

h4. Trac Configuration

<pre>

<pre>

[trac]

authz_file = /path/to/svnaccessfile

</pre>

if you want to support the use of the @[@_modulename_@:/@_some_@/@_path_@]@ syntax within the @authz_file@, add 

<pre>

authz_module_name = modulename

</pre>

where _modulename_ refers to the same repository indicated by the @repository_dir@ entry in the @[trac]@ section.

*Note:* Usernames inside the Authz file +must+ be the same as those used inside trac. 

h4. Subversion Configuration

The same access file is typically applied to the corresponding Subversion repository using an Apache directive like this:

<pre>

<Location /repos>

  DAV svn

  SVNParentPath /usr/local/svn

  # our access control policy

  [[AuthzSVNAccessFile]] /path/to/svnaccessfile

</Location>

</pre>

For information about how to restrict access to entire projects in a multiple project environment see [trac:wiki:TracMultipleProjectsSVNAccess]

h2. Getting [[TracFineGrainedPermissions]] to work

Don't forget to restart Trac engine to apply new configuration if you are running tracd standalone server.

----

See also: [[TracPermissions]]

http://trac-hacks.org/wiki/FineGrainedPageAuthzEditorPlugin for a simple editor plugin.