X-Git-Url: https://sipb.mit.edu/gitweb.cgi/ikiwiki.git/blobdiff_plain/60188d728080c3e558b647d7595ea376944f51d0..5397cca7350747805cf47df05e63f18ac6746bf2:/doc/todo/Zoned_ikiwiki.mdwn diff --git a/doc/todo/Zoned_ikiwiki.mdwn b/doc/todo/Zoned_ikiwiki.mdwn index b2edef7ba..76b2b69c7 100644 --- a/doc/todo/Zoned_ikiwiki.mdwn +++ b/doc/todo/Zoned_ikiwiki.mdwn @@ -5,13 +5,113 @@ ## The idea The idea behind this would be to have one ikiwiki behave as a dynamic private wiki in a specified area -and a more static publiczone wiki. Actually private wiki page can be addressed via a *pagespec*. +and a more static publiczone wiki. -What is ready /can be done: +## Use cases -* We already can more or less do this for example with [[httpauth|/plugins/httpauth/]], *.htaccess* files and a proper *httpauth_pagespec* -yet at the cost of maintaining two different user/pass logbase (native ikiwiki signin) -* Furthermore we can [[lockedit|plugins/lockedit/]] some pagespecs, ie in the public zone. +This can be more or less difficult depending on the use case. + +### Purely static public zone with a single, controlled-access inward zone + +For this case, only a known set of people are authorized to see the inward zone +or edit anything. Everybody else sees only the public zone. This use case is mostly +easy to handle now, as long as access to things like the `recentchanges` page and +repository browser are not granted for the public zone. In particular, the features +that allow information exposure via edit access are not of concern in this case. + +### Static public zone, more than one controlled inward zone + +In this case, the known, controlled set of people with special access are divided +into groups with access to different (or overlapping) zones. The public still sees only a static zone. + +Here, some of the harder issues, like information disclosure via edit access, do apply, +but only to members of the known, controlled groups. How much of a problem that is +depends on _how sensitive_ the information is that each group might reveal from another +zone. The rcs logs will show when a page has been edited to contain an [[ikiwiki/directive/inline]] +directive or other trick to reveal information, so if it is enough to treat the trusted users' conduct +as a management issue ("don't do that, please") then the risks can be acceptable in this case. + +### Public zone allows contribution/editing by external users + +This case is the most difficult to cover at present, and probably shouldn't be attempted +without solutions to most or all of the **obstacles** identified here. + +## Implementation techniques + +### Edit control by user and pagespec: lockedit + +This works today, using the [[plugins/lockedit]] plugin. Because the `user` predicate +can be part of a [[ikiwiki/PageSpec]], this is all we need to flexibly control edit access +using any authentication method `ikiwiki` supports. + +### View control in the `http` server + +We already can more or less do this for example with [[httpauth|/plugins/httpauth/]], `.htaccess` files and a proper `httpauth_pagespec`. + +_Drawbacks:_ might be fiddly to configure and require maintaining two different user/pass logbases (native ikiwiki +signin), or impractical if ikiwiki is using an authentication method not natively supported +in the `http` server (e.g., OpenID). + +### View control in ikiwiki CGI + +By requiring access to private zones to go through an ikiwiki CGI wrapper, +any ikiwiki-supported authentication method can be used, and the accessible +pages can be specified using the `user` predicate with [[ikiwiki/PageSpec]]s, +just as with the [[plugins/lockedit]] plugin. + +The [[plugins/contrib/signinview]] plugin implements this idea, using very +simple configuration that is possible even in shared-hosting environments +without complete access to the `http` server configuration, as long as +`.htaccess` files or their equivalent can be created. The top directory of +a private zone needs only a `.htaccess` file with `Deny from All` or +`Require all denied` (or other equivalent directive for the `http` server +in use), and a `403` error handler of `{$cgiurl}?do=view`. + +The plugin emits response headers intended to discourage non-private caches +from retaining the retrieved content. (They are already supposed to avoid +caching any response to a request with an `Authorization` header, but this +plugin can be used with any ikiwiki-supported auth method, not all of which +require that header.) + +A plugin like [[plugins/contrib/pagespec_alias]] can be very useful for +defining a group of authorized users: + + us: user(alice) or user(bob) or user(clotaldo) + +so that zone access can be a simple [[ikiwiki/PageSpec]]: + + us() and ours/* + +*Drawbacks:* The private zones no longer reap all the benefits of a static +wiki generator, as a (fairly heavy) ikiwiki CGI wrapper must be started for +each access. (On the other hand, all it needs to do after confirming authorization +is basically `cat` the statically-generated page with appropriate response headers, +keeping the code simple and easy to audit.) + +This can be adequate for a case where the static, public zone could receive a lot +of traffic, with the private zone(s) accessed only by a known small group of people. + +### View control with a FastCGI Authorizer + +A plugin implementing a [FastCGI](http://www.fastcgi.com/) +[Authorizer](http://www.fastcgi.com/drupal/node/6?q=node/22#S6.3) could provide +the same benefits as [[plugins/contrib/signinview]] (any ikiwiki-supported auth +method, simple zone definition with [[ikiwiki/PageSpec]]s) with less overhead +per access. It would also be simpler than [[plugins/contrib/signinview]] by +leaving it as the `http` server's responsibility to generate the proper headers +and serve the content. + +Caching proxies are already supposed to avoid caching any response to a request +that included an `Authorization` header. For some ikiwiki-supported auth methods, +that header might not be needed in the request, and care may be needed to configure +the server to emit other necessary response headers to discourage caching of +content from a private zone. + +*Drawbacks:* Not yet implemented, someone would have to do it. +It's not clear [[what code changes fastcgi|todo/fastcgi or modperl installation instructions]] +would require in ikiwiki. An Authorizer seems like a good place to start because of its +limited, simple functionality--but as it could make use of any ikiwiki-supported auth method, +evaluate `PageSpec`s, and the like, it could still run a non-trivial amount of the code. ## Obstacles @@ -23,6 +123,18 @@ but I'll begin it here. Note that not all of these issues will be problems for all **zoned ikiwiki use cases**. +### Leakage of page existence by `do=goto` + +An unauthorized client can use a `do=goto` request to find out whether a +page exists (will be forbidden to view it) or not (will be forbidden to create it). + +In [[plugins/contrib/signinview]] this is handled by hooking +`cgi` first and checking for `goto` and a non-public page. If the requested page +(existing or not) matches the `public_pages` PageSpec, it is handed off for the `goto` +plugin to handle normally. Otherwise, the `do` parameter is changed to `signingoto` +so the `goto` plugin's `cgi` hook will _not_ handle it, and the `sessioncgi` hook +takes care of it when the user's identity is available. + ### Backlinks What is problematic is when you link a public page in a private page : @@ -154,3 +266,10 @@ review of the code and plugins (including third-party plugins) to complete. * Not to forget `contrib` plugins * [[plugins/contrib/report]] ? * _others_? + +Note that, _with_ the right controls on who can edit the pages and insert +the directives, the fact that a public page can inline stuff from private +pages can be very useful. Public pages can be created that are populated +by selected content that's maintained on the private side. The [[ikiwiki/directive/if]] +directive can be used in the private content to control what parts can be +inlined into public pages. All of this is in ikiwiki today.