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Fine grained permissions
Contents
Table of Contents
There is a general mechanism in place that allows custom permission policies to grant or deny any action on any Trac resource, or even specific versions of a resource.
That mechanism is AuthzPolicy
, an optional component in tracopt.perm.authz_policy.*
which is not activated by default. It can be activated via the Plugins panel in the Trac administration module.
See TracPermissions for a more general introduction to Trac permissions and permission policies.
Permission Policies
A great diversity of permission policies can be implemented and Trac comes with a few examples.
The active policies are determined by a configuration setting:
[trac] permission_policies = DefaultWikiPolicy, DefaultTicketPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
- DefaultWikiPolicy controls readonly access to wiki pages.
- DefaultTicketPolicy provides elevated privileges in the ticket system for authenticated users.
- DefaultPermissionPolicy checks for the traditional coarse-grained permissions described in TracPermissions.
- LegacyAttachmentPolicy uses the coarse-grained permissions to check permissions on attachments.
Among the optional choices, there is #AuthzPolicy, a very generic permission policy, based on an Authz-style system. See authz_policy.py for details.
Another permission policy #AuthzSourcePolicy, uses the path-based authorization defined by Subversion to enforce permissions on the version control system.
See also sample-plugins/permissions for more examples.
AuthzPolicy
Configuration
- Put an empty conf file (
authzpolicy.conf
) in a secure location on the server, not readable by users other than the webuser. If the file contains non-ASCII characters, the UTF-8 encoding should be used. - Update your
trac.ini
:- modify the permission_policies option in the
[trac]
section:[trac] permission_policies = AuthzPolicy, DefaultWikiPolicy, DefaultTicketPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
- add a new
[authz_policy]
section and point theauthz_file
option to the conf file:[authz_policy] authz_file = /some/trac/env/conf/authzpolicy.conf
- enable the plugin through WebAdmin or by editing the
[components]
section:[components] tracopt.perm.authz_policy.* = enabled
- modify the permission_policies option in the
Usage Notes
Note the order in which permission policies are specified: policies are implemented in the sequence provided and therefore may override earlier policy specifications.
A policy will return either True
, False
or None
for a given permission check. True
is returned if the policy explicitly grants the permission. False
is returned if the policy explicitly denies the permission. None
is returned if the policy is unable to either grant or deny the permission.
Note: Only if the return value is None
will the next permission policy be consulted. If none of the policies explicitly grants the permission, the final result will be False
, i.e. permission denied.
The authzpolicy.conf
file is a .ini
style configuration file:
[wiki:PrivatePage@*] john = WIKI_VIEW, !WIKI_MODIFY jack = WIKI_VIEW * =
- Each section of the config is a glob pattern used to match against a Trac resource descriptor. These descriptors are in the form:
<realm>:<id>@<version>[/<realm>:<id>@<version> ...]
Resources are ordered left to right, from parent to child. If any component is inapplicable, *
is substituted. If the version pattern is not specified explicitly, all versions (@*
) is added implicitly. Example: Match the WikiStart page:
[wiki:*] [wiki:WikiStart*] [wiki:WikiStart@*] [wiki:WikiStart]
Example: Match the attachment wiki:WikiStart@117/attachment:FOO.JPG@*
on WikiStart:
[wiki:*] [wiki:WikiStart*] [wiki:WikiStart@*] [wiki:WikiStart@*/attachment:*] [wiki:WikiStart@117/attachment:FOO.JPG]
- Sections are checked against the current Trac resource descriptor IN ORDER of appearance in the configuration file. ORDER IS CRITICAL.
- Once a section matches, the current username is matched against the keys (usernames) of the section, IN ORDER.
- If a key (username) is prefixed with a
@
, it is treated as a group. - If a value (permission) is prefixed with a
!
, the permission is denied rather than granted.
- If a key (username) is prefixed with a
The username will match any of 'anonymous', 'authenticated', <username> or '*', using normal Trac permission rules.
Note: Other groups which are created by user (e.g. by 'adding subjects to groups' on web interface page Admin / Permissions) cannot be used. See #5648 for details about this missing feature.
For example, if the authz_file
contains:
[wiki:WikiStart@*] * = WIKI_VIEW [wiki:PrivatePage@*] john = WIKI_VIEW * = !WIKI_VIEW
and the default permissions are set like this:
john WIKI_VIEW jack WIKI_VIEW # anonymous has no WIKI_VIEW
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
Groups:
[groups] admins = john, jack devs = alice, bob [wiki:Dev@*] @admins = TRAC_ADMIN @devs = WIKI_VIEW * = [*] @admins = TRAC_ADMIN * =
Then:
- everything is blocked (whitelist approach), but
- admins get all TRAC_ADMIN everywhere and
- devs can view wiki pages.
Some repository examples (Browse Source specific):
# A single repository: [repository:test_repo@*] john = BROWSER_VIEW, FILE_VIEW # John has BROWSER_VIEW and FILE_VIEW for the entire test_repo # The default repository (requires Trac 1.0.2 or later): [repository:@*] john = BROWSER_VIEW, FILE_VIEW # John has BROWSER_VIEW and FILE_VIEW for the entire default repository # All repositories: [repository:*@*] jack = BROWSER_VIEW, FILE_VIEW # Jack has BROWSER_VIEW and FILE_VIEW for all repositories
Very granular repository access:
# John has BROWSER_VIEW and FILE_VIEW access to trunk/src/some/location/ only [repository:test_repo@*/source:trunk/src/some/location/*@*] john = BROWSER_VIEW, FILE_VIEW # John has BROWSER_VIEW and FILE_VIEW access to only revision 1 of all files at trunk/src/some/location only [repository:test_repo@*/source:trunk/src/some/location/*@1] john = BROWSER_VIEW, FILE_VIEW # John has BROWSER_VIEW and FILE_VIEW access to all revisions of 'somefile' at trunk/src/some/location only [repository:test_repo@*/source:trunk/src/some/location/somefile@*] john = BROWSER_VIEW, FILE_VIEW # John has BROWSER_VIEW and FILE_VIEW access to only revision 1 of 'somefile' at trunk/src/some/location only [repository:test_repo@*/source:trunk/src/some/location/somefile@1] john = BROWSER_VIEW, FILE_VIEW
Note: In order for Timeline to work/visible for John, we must add CHANGESET_VIEW to the above permission list.
Missing Features
Although possible with the DefaultPermissionPolicy handling (see Admin panel), fine-grained permissions still miss those grouping features (see #9573, #5648). Patches are partially available, see authz_policy.2.patch, part of #6680.
You cannot do the following:
[groups] team1 = a, b, c team2 = d, e, f team3 = g, h, i departmentA = team1, team2
Permission groups are not supported either, so you cannot do the following:
[groups] permission_level_1 = WIKI_VIEW, TICKET_VIEW permission_level_2 = permission_level_1, WIKI_MODIFY, TICKET_MODIFY [*] @team1 = permission_level_1 @team2 = permission_level_2 @team3 = permission_level_2, TICKET_CREATE
AuthzSourcePolicy (mod_authz_svn
-like permission policy)
AuthzSourcePolicy
can be used for restricting access to the repository. Granular 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 Path-Based Authorization section in the Server Configuration chapter of the svn book.
Example:
[/] * = r [/branches/calc/bug-142] harry = rw sally = r [/branches/calc/bug-142/secret] harry =
- / = 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)
Trac Configuration
To activate granular permissions you must specify the authz_file
option in the [svn]
section of trac.ini. If this option is set to null or not specified, the permissions will not be used.
[svn] authz_file = /path/to/svnaccessfile
If you want to support the use of the [
modulename:/
some/
path]
syntax within the authz_file
, add:
authz_module_name = modulename
where modulename refers to the same repository indicated by the <name>.dir
entry in the [repositories]
section. As an example, if the somemodule.dir
entry in the [repositories]
section is /srv/active/svn/somemodule
, that would yield the following:
[svn] authz_file = /path/to/svnaccessfile authz_module_name = somemodule ... [repositories] somemodule.dir = /srv/active/svn/somemodule
where the svn access file, /path/to/svnaccessfile
, contains entries such as [somemodule:/some/path]
.
Note: Usernames inside the Authz file must be the same as those used inside trac.
Make sure you have AuthzSourcePolicy included in the permission_policies list in trac.ini, otherwise the authz permissions file will be ignored.
[trac] permission_policies = AuthzSourcePolicy, DefaultWikiPolicy, DefaultTicketPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
Subversion Configuration
The same access file is typically applied to the corresponding Subversion repository using an Apache directive like this:
<Location /repos> DAV svn SVNParentPath /usr/local/svn # our access control policy AuthzSVNAccessFile /path/to/svnaccessfile </Location>
For information about how to restrict access to entire projects in a multiple project environment see wiki:TracMultipleProjectsSVNAccess.
DefaultWikiPolicy and DefaultTicketPolicy
Since 1.1.2, the read-only attribute of wiki pages is enabled and enforced when DefaultWikiPolicy
is in the list of active permission policies (DefaultWikiPolicy
was named ReadonlyWikiPolicy
from Trac 1.1.2 to 1.3.1). The default for new Trac installations in 1.3.2 and later is:
[trac] permission_policies = DefaultWikiPolicy, DefaultTicketPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
DefaultWikiPolicy
returns False
to deny modify, delete and rename actions on wiki pages when the page has the read-only attribute set and the user does not have WIKI_ADMIN
, regardless of WIKI_MODIFY
, WIKI_DELETE
and WIKI_RENAME
permissions. It returns None
for all other cases, which causes the next permission policy in the list to be consulted.
Since 1.3.2 DefaultTicketPolicy
implements the following behaviors:
- Authenticated user can edit their own comments.
- Authenticated user with
TICKET_APPEND
orTICKET_CHGPROP
can modify the description of a ticket they reported. - User with
MILESTONE_VIEW
can change the ticket milestone.
The wiki- and ticket-specific behaviors are implemented in permission policies so they can be easily replaced in case other behavior is desired.
When upgrading from earlier versions of Trac, DefaultWikiPolicy, DefaultTicketPolicy
will be appended to the list of permission_policies
when upgrading the environment, provided that permission_policies
has the default value (ReadonlyWikiPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
if upgrading from Trac 1.1.2 or later). If any non-default permission_polices
are active, DefaultWikiPolicy, DefaultTicketPolicy
will need to be manually added to the list. A message will be echoed to the console when upgrading the environment, indicating if any action needs to be taken.
DefaultWikiPolicy and DefaultTicketPolicy must be listed before DefaultPermissionPolicy. The latter returns True
to allow modify, delete or rename actions when the user has the respective WIKI_*
permission, without consideration for the read-only attribute. Similarly, some of the behaviors implemented in DefaultTicketPolicy
won't be considered if DefaultPermissionPolicy
is executed first.
When active, the #AuthzPolicy should therefore come before DefaultWikiPolicy, DefaultTicketPolicy
, allowing it to grant or deny the actions on individual resources, which is the usual ordering for AuthzPolicy
in the permission_policies
list.
[trac] permission_policies = AuthzPolicy, DefaultWikiPolicy, DefaultTicketPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
The placement of #AuthzSourcePolicy relative to DefaultWikiPolicy, DefaultTicketPolicy
does not matter since they don't perform checks on the same realms.
For all other permission policies, the user will need to decide the proper ordering. Generally, if the permission policy should be capable of overriding the checks performed by DefaultWikiPolicy
or DefaultTicketPolicy
, it should come before the policy it overrides. If DefaultWikiPolicy
or DefaultTicketPolicy
should override the check performed by another permission policy, as is the case for those policies relative to DefaultPermissionPolicy
, then the overriding policy should come first.
Debugging permissions
In trac.ini set:
[logging] log_file = trac.log log_level = DEBUG log_type = file
Display the trac.log to understand what checks are being performed:
tail -n 0 -f log/trac.log | egrep '\[perm\]|\[authz_policy\]'
See the sourced documentation of the plugin for more info.
See also: TracPermissions, FineGrainedPageAuthzEditorPlugin for a simple editor.