Changes between Version 2 and Version 3 of TracFineGrainedPermissions


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Timestamp:
Feb 16, 2019, 9:02:35 AM (6 years ago)
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trac
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  • TracFineGrainedPermissions

    v2 v3  
    1 = Fine grained permissions =
    2 
    3 Before Trac 0.11, it was only possible to define fine-grained permissions checks on the repository browser sub-system.
    4 
    5 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.
    6 
    7 Note that for Trac 0.12, `authz_policy` has been integrated as an optional module (in `tracopt.perm.authz_policy.*`), so it's installed by default and can simply be activated via the //Plugins// panel in the Trac administration module.
    8 
    9 
    10 == Permission Policies ==
    11 
    12 A great diversity of permission policies can be implemented, and Trac comes with a few examples.
    13 
    14 Which policies are currently active is determined by a configuration setting in TracIni:
    15 e.g.
    16 {{{
    17 [trac]
    18 permission_policies = AuthzSourcePolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
    19 }}}
    20 This lists the [#AuthzSourcePolicy] described below as the first policy, followed by the !DefaultPermissionPolicy which checks for the traditional coarse grained style permissions described in TracPermissions, and the !LegacyAttachmentPolicy which knows how to use the coarse grained permissions for checking the permissions available on attachments.
    21 
    22 Among the possible optional choices, there is [#AuthzPolicy], a very generic permission policy, based on an Authz-style system. See
    23 [trac:source:branches/0.12-stable/tracopt/perm/authz_policy.py authz_policy.py] for details.
    24 
    25 Another popular permission policy [#AuthzSourcePolicy], re-implements the pre-0.12 support for checking fine-grained permissions limited to Subversion repositories in terms of the new system.
    26 
    27 See also [trac:source:branches/0.12-stable/sample-plugins/permissions sample-plugins/permissions] for more examples.
    28 
    29 
    30 === !AuthzPolicy ===
    31 
    32  - Install [http://www.voidspace.org.uk/python/configobj.html ConfigObj] (required).
    33  - Copy authz_policy.py into your plugins directory.
    34  - Put a [http://swapoff.org/files/authzpolicy.conf authzpolicy.conf] file somewhere, preferably on a secured location on the server, not readable for others than the webuser. If the  file contains non-ASCII characters, the UTF-8 encoding should be used.
    35  - Update your `trac.ini`:
    36    1. modify the [TracIni#trac-section permission_policies] entry in the `[trac]` section
    37 {{{
    38 [trac]
    39 ...
    40 permission_policies = AuthzPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
    41 }}}
    42    2. add a new `[authz_policy]` section
    43 {{{
     1= Fine grained permissions
     2[[PageOutline(2-5, Contents, floated)]]
     3[[TracGuideToc]]
     4
     5There 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.
     6
     7That mechanism is `authz_policy`, which is an optional module in `tracopt.perm.authz_policy.*`, so it is installed by default. It can be activated via the //Plugins// panel in the Trac administration module.
     8
     9== Permission Policies
     10
     11A great diversity of permission policies can be implemented and Trac comes with a few examples.
     12
     13The active policies are determined by a [TracIni#trac-permission_policies-option configuration setting]:
     14
     15{{{#!ini
     16[trac]
     17permission_policies = ReadonlyWikiPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
     18}}}
     19
     20* [#ReadonlyWikiPolicy] controls readonly access to wiki pages.
     21* !DefaultPermissionPolicy checks for the traditional coarse-grained permissions described in TracPermissions.
     22* !LegacyAttachmentPolicy uses the coarse-grained permissions to check permissions on attachments.
     23
     24Among the optional choices, there is [#AuthzPolicy], a very generic permission policy, based on an Authz-style system. See
     25[trac:source:branches/1.2-stable/tracopt/perm/authz_policy.py authz_policy.py] for details.
     26
     27Another permission policy [#AuthzSourcePolicy], uses the [http://svnbook.red-bean.com/nightly/en/svn.serverconfig.pathbasedauthz.html path-based authorization] defined by Subversion to enforce permissions on the version control system.
     28
     29See also [trac:source:branches/1.2-stable/sample-plugins/permissions sample-plugins/permissions] for more examples.
     30
     31=== !AuthzPolicy
     32==== Configuration
     33* Put a [http://swapoff.org/files/authzpolicy.conf conf] file 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.
     34* Update your `trac.ini`:
     35  1. modify the [TracIni#trac-section permission_policies] entry in the `[trac]` section:
     36{{{#!ini
     37[trac]
     38permission_policies = AuthzPolicy, ReadonlyWikiPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
     39}}}
     40  1. add a new `[authz_policy]` section and point the `authz_file` option to the conf file:
     41{{{#!ini
    4442[authz_policy]
    4543authz_file = /some/trac/env/conf/authzpolicy.conf
    4644}}}
    47    3. enable the single file plugin
     45  1. enable the plugin through [/admin/general/plugin WebAdmin] or by editing the `[components]` section:
     46{{{#!ini
     47[components]
     48tracopt.perm.authz_policy.* = enabled
     49}}}
     50
     51==== Usage Notes
     52
     53Note the order in which permission policies are specified: policies are implemented in the sequence provided and therefore may override earlier policy specifications.
     54
     55A 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.
     56
     57NOTE: 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.
     58
     59The `authzpolicy.conf` file is a `.ini` style configuration file:
     60{{{#!ini
     61[wiki:PrivatePage@*]
     62john = WIKI_VIEW, !WIKI_MODIFY
     63jack = WIKI_VIEW
     64* =
     65}}}
     66* Each section of the config is a glob pattern used to match against a Trac resource descriptor. These descriptors are in the form:
    4867{{{
    49 [components]
    50 ...
    51 # Trac 0.12
    52 tracopt.perm.authz_policy.* = enabled
    53 # for Trac 0.11 use this
    54 #authz_policy.* = enabled
    55 }}}
    56 
    57 Note that the order in which permission policies are specified is quite critical,
    58 as policies will be examined in the sequence provided.
    59 
    60 A policy will return either `True`, `False` or `None` for a given permission check.
    61 Only if the return value is `None` will the ''next'' permission policy be consulted.
    62 If no policy explicitly grants the permission, the final result will be `False`
    63 (i.e. no permission).
     68<realm>:<id>@<version>[/<realm>:<id>@<version> ...]
     69}}}
     70
     71Resources 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:
     72{{{#!ini
     73[wiki:*]
     74[wiki:WikiStart*]
     75[wiki:WikiStart@*]
     76[wiki:WikiStart]
     77}}}
     78
     79Example: Match the attachment `wiki:WikiStart@117/attachment:FOO.JPG@*` on WikiStart:
     80{{{#!ini
     81[wiki:*]
     82[wiki:WikiStart*]
     83[wiki:WikiStart@*]
     84[wiki:WikiStart@*/attachment:*]
     85[wiki:WikiStart@117/attachment:FOO.JPG]
     86}}}
     87
     88* Sections are checked against the current Trac resource descriptor '''IN ORDER''' of appearance in the configuration file. '''ORDER IS CRITICAL'''.
     89
     90* Once a section matches, the current username is matched against the keys (usernames) of the section, '''IN ORDER'''.
     91  * If a key (username) is prefixed with a `@`, it is treated as a group.
     92  * If a value (permission) is prefixed with a `!`, the permission is denied rather than granted.
     93
     94The 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 [trac:ticket:5648 #5648] for details about this missing feature. ||
    6495
    6596For example, if the `authz_file` contains:
    66 {{{
     97{{{#!ini
    6798[wiki:WikiStart@*]
    6899* = WIKI_VIEW
    … …  
    70101[wiki:PrivatePage@*]
    71102john = WIKI_VIEW
    72 * =
     103* = !WIKI_VIEW
    73104}}}
    74105and the default permissions are set like this:
    … …  
    80111
    81112Then:
    82  - All versions of WikiStart will be viewable by everybody (including anonymous)
    83  - !PrivatePage will be viewable only by john
    84  - other pages will be viewable only by john and jack
    85 
    86 
    87 === !AuthzSourcePolicy  (mod_authz_svn-like permission policy) === #AuthzSourcePolicy
    88 
    89 At the time of this writing, the old fine grained permissions system from Trac 0.11 and before used for restricting access to the repository has  been converted to a permission policy component, but from the user point of view, this makes little if no difference.
    90 
    91 That kind of fine-grained permission control needs a definition file, which is the one used by Subversion's mod_authz_svn.
    92 More information about this file format and about its usage in Subversion is available in the  [http://svnbook.red-bean.com/en/1.5/svn.serverconfig.pathbasedauthz.html Path-Based Authorization] section in the Server Configuration chapter of the svn book.
     113  * All versions of WikiStart will be viewable by everybody, including anonymous
     114  * !PrivatePage will be viewable only by john
     115  * other pages will be viewable only by john and jack
     116
     117Groups:
     118{{{#!ini
     119[groups]
     120admins = john, jack
     121devs = alice, bob
     122
     123[wiki:Dev@*]
     124@admins = TRAC_ADMIN
     125@devs = WIKI_VIEW
     126* =
     127
     128[*]
     129@admins = TRAC_ADMIN
     130* =
     131}}}
     132
     133Then:
     134- everything is blocked (whitelist approach), but
     135- admins get all TRAC_ADMIN everywhere and
     136- devs can view wiki pages.
     137
     138Some repository examples (Browse Source specific):
     139{{{#!ini
     140# A single repository:
     141[repository:test_repo@*]
     142john = BROWSER_VIEW, FILE_VIEW
     143# John has BROWSER_VIEW and FILE_VIEW for the entire test_repo
     144
     145# The default repository (requires Trac 1.0.2 or later):
     146[repository:@*]
     147john = BROWSER_VIEW, FILE_VIEW
     148# John has BROWSER_VIEW and FILE_VIEW for the entire default repository
     149
     150# All repositories:
     151[repository:*@*]
     152jack = BROWSER_VIEW, FILE_VIEW
     153# Jack has BROWSER_VIEW and FILE_VIEW for all repositories
     154}}}
     155
     156Very granular repository access:
     157{{{#!ini
     158# John has BROWSER_VIEW and FILE_VIEW access to trunk/src/some/location/ only
     159[repository:test_repo@*/source:trunk/src/some/location/*@*]
     160john = BROWSER_VIEW, FILE_VIEW
     161
     162# John has BROWSER_VIEW and FILE_VIEW access to only revision 1 of all files at trunk/src/some/location only
     163[repository:test_repo@*/source:trunk/src/some/location/*@1]
     164john = BROWSER_VIEW, FILE_VIEW
     165
     166# John has BROWSER_VIEW and FILE_VIEW access to all revisions of 'somefile' at trunk/src/some/location only
     167[repository:test_repo@*/source:trunk/src/some/location/somefile@*]
     168john = BROWSER_VIEW, FILE_VIEW
     169
     170# John has BROWSER_VIEW and FILE_VIEW access to only revision 1 of 'somefile' at trunk/src/some/location only
     171[repository:test_repo@*/source:trunk/src/some/location/somefile@1]
     172john = BROWSER_VIEW, FILE_VIEW
     173}}}
     174
     175Note: In order for Timeline to work/visible for John, we must add CHANGESET_VIEW to the above permission list.
     176
     177==== Missing Features
     178Although possible with the !DefaultPermissionPolicy handling (see Admin panel), fine-grained permissions still miss those grouping features (see [trac:ticket:9573 #9573], [trac:ticket:5648 #5648]). Patches are partially available, see authz_policy.2.patch, part of [trac:ticket:6680 #6680].
     179
     180You cannot do the following:
     181{{{#!ini
     182[groups]
     183team1 = a, b, c
     184team2 = d, e, f
     185team3 = g, h, i
     186departmentA = team1, team2
     187}}}
     188
     189Permission groups are not supported either, so you cannot do the following:
     190{{{#!ini
     191[groups]
     192permission_level_1 = WIKI_VIEW, TICKET_VIEW
     193permission_level_2  = permission_level_1, WIKI_MODIFY, TICKET_MODIFY
     194[*]
     195@team1 = permission_level_1
     196@team2 = permission_level_2
     197@team3 = permission_level_2, TICKET_CREATE
     198}}}
     199
     200=== !AuthzSourcePolicy  (mod_authz_svn-like permission policy) #AuthzSourcePolicy
     201
     202`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.
     203More information about this file format and about its usage in Subversion is available in the [http://svnbook.red-bean.com/en/1.7/svn.serverconfig.pathbasedauthz.html Path-Based Authorization] section in the Server Configuration chapter of the svn book.
    93204
    94205Example:
    95 {{{
     206{{{#!ini
    96207[/]
    97208* = r
    … …  
    109220 * '''/branches/calc/bug-142/secret''' = ''harry has no access, sally has read access (inherited as a sub folder permission)''
    110221
    111 ==== Trac Configuration ====
    112 
    113 To activate fine grained permissions you __must__ specify the {{{authz_file}}} option in the {{{[trac]}}} section of trac.ini. If this option is set to null or not specified the permissions will not be used.
    114 
    115 {{{
    116 [trac]
     222==== Trac Configuration
     223
     224To 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.
     225
     226{{{#!ini
     227[svn]
    117228authz_file = /path/to/svnaccessfile
    118229}}}
    119230
    120 If you want to support the use of the `[`''modulename''`:/`''some''`/`''path''`]` syntax within the `authz_file`, add 
    121 
    122 {{{
     231If you want to support the use of the `[`''modulename''`:/`''some''`/`''path''`]` syntax within the `authz_file`, add:
     232
     233{{{#!ini
    123234authz_module_name = modulename
    124235}}}
    125236
    126 where ''modulename'' refers to the same repository indicated by the `repository_dir` entry in the `[trac]` section. As an example, if the `repository_dir` entry in the `[trac]` section is {{{/srv/active/svn/blahblah}}}, that would yield the following:
    127 
    128 {{{
    129 [trac]
     237where ''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:
     238
     239{{{ #!ini
     240[svn]
    130241authz_file = /path/to/svnaccessfile
    131 authz_module_name = blahblah
     242authz_module_name = somemodule
    132243...
    133 repository_dir = /srv/active/svn/blahblah
    134 }}}
    135 
    136 where the svn access file, {{{/path/to/svnaccessfile}}}, contains entries such as {{{[blahblah:/some/path]}}}.
     244[repositories]
     245somemodule.dir = /srv/active/svn/somemodule
     246}}}
     247
     248where the svn access file, {{{/path/to/svnaccessfile}}}, contains entries such as {{{[somemodule:/some/path]}}}.
    137249
    138250'''Note:''' Usernames inside the Authz file __must__ be the same as those used inside trac.
    … …  
    140252As of version 0.12, make sure you have ''!AuthzSourcePolicy'' included in the permission_policies list in trac.ini, otherwise the authz permissions file will be ignored.
    141253
    142 {{{ 
    143 [trac]
    144 permission_policies = AuthzSourcePolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
    145 }}}
    146 
    147 ==== Subversion Configuration ====
     254{{{#!ini
     255[trac]
     256permission_policies = AuthzSourcePolicy, ReadonlyWikiPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy
     257}}}
     258
     259==== Subversion Configuration
    148260
    149261The same access file is typically applied to the corresponding Subversion repository using an Apache directive like this:
    150 {{{
     262{{{#!apache
    151263<Location /repos>
    152264  DAV svn
    … …  
    158270}}}
    159271
    160 For information about how to restrict access to entire projects in a multiple project environment see [trac:wiki:TracMultipleProjectsSVNAccess]
     272For information about how to restrict access to entire projects in a multiple project environment see [trac:wiki:TracMultipleProjectsSVNAccess].
     273
     274=== ReadonlyWikiPolicy
     275
     276Since 1.1.2, the read-only attribute of wiki pages is enabled and enforced when `ReadonlyWikiPolicy` is in the list of active permission policies. The default for new Trac installations in 1.1.2 and later is:
     277{{{
     278[trac]
     279permission_policies = ReadonlyWikiPolicy,
     280 DefaultPermissionPolicy,
     281 LegacyAttachmentPolicy
     282}}}
     283
     284When upgrading from earlier versions of Trac, `ReadonlyWikiPolicy` will be appended to the list of `permission_policies` when upgrading the environment, provided that `permission_policies` has the default value. If any non-default `permission_polices` are active, `ReadonlyWikiPolicy` **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.
     285
     286**!ReadonlyWikiPolicy 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.
     287
     288The `ReadonlyWikiPolicy` 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.
     289
     290When active, the [#AuthzPolicy] should therefore come before `ReadonlyWikiPolicy`, allowing it to grant or deny the actions on individual resources, which is the usual ordering for `AuthzPolicy` in the `permission_policies` list.
     291{{{
     292[trac]
     293permission_policies = AuthzPolicy,
     294 ReadonlyWikiPolicy,
     295 DefaultPermissionPolicy,
     296 LegacyAttachmentPolicy
     297}}}
     298
     299The placement of [#AuthzSourcePolicy] relative to `ReadonlyWikiPolicy` does not matter since they don't perform checks on the same realms.
     300
     301For all other permission policies, the user will need to decide the proper ordering. Generally, if the permission policy should be capable of overriding the check performed by `ReadonlyWikiPolicy`, it should come before `ReadonlyWikiPolicy` in the list. If the `ReadonlyWikiPolicy` should override the check performed by another permission policy, as is the case for `DefaultPermissionPolicy`, then `ReadonlyWikiPolicy` should come first.
    161302
    162303== Debugging permissions
    163304In trac.ini set:
    164 {{{
     305{{{#!ini
    165306[logging]
    166307log_file = trac.log
    … …  
    169310}}}
    170311
    171 And watch:
    172 {{{
     312Display the trac.log to understand what checks are being performed:
     313{{{#!sh
    173314tail -n 0 -f log/trac.log | egrep '\[perm\]|\[authz_policy\]'
    174315}}}
    175316
    176 to understand what checks are being performed. See the sourced documentation of the plugin for more info.
    177 
     317See the sourced documentation of the plugin for more info.
    178318
    179319----