positive proposal, so here is a stab at what I think would be a
compelling integrated architecture of ACLs. If I were to try to adapt a
basic OS achitecture for permissions, I'd note that the object (files,
etc) have permissions attached to them, like in the filesystem itself.
But permission checking is integral to the core, most likely even the
kernel.
I'd think the same type of system would fit ZF very well. Let most
everything be able to be defined as a resource with applicable
permissions set if desired. But have the Front controller process
permissions. You could have certain front controller parameters to
enable or disable permission checking, like you do with view renderers,
etc. When enabled, it looks to check for permission based on an ACL that
is tied to definable resources before it executes any applicable method.
Heck, with this type of separated elements (resource/ACL vs permission
checking), even a plugin could be an access controlled
resource...basically anything other than the FC itself.
And as an added benefit, it would seem that this would solve the
argument of where to implement ACLs. Service? Fine, make services
resources. Controllers? Fine. Make controllers resources. Something
else? Fine. Make that something else a resource.
Just a thought.
--Seth
-----Original Message-----
From: Atkins, Seth (RICH1:5278)
Sent: Tuesday, September 01, 2009 1:55 AM
To: Matthew Weier O'Phinney; fw-mvc@lists.zend.com
Subject: RE: [fw-mvc] MVC integration of Zend_Acl
>As I noted earlier, I personally like to put my ACLs with my service
layer. This means that I'm actually >executing my action before I find
out if the user has the ability to do something -- probably your worst
>nightmare.
True, that wouldn't be my preference. The analogy I would make is that
it is like a file system retrieving the file, reading it, and even
opening it, just to find that permission isn't granted and averting
showing it to the display. Not that there might not be advantages, but
to extend the analogy a bit further, in some cases, it is also like
executing a bash script that alters other files or processes just to
find out later, when output is being processed that execute permission
wasn't allowed in the first place.
The point is that in some applications, where actions alter the
database, you can't afford to have access checking performed later,
because the damage would already have occurred by the time you ever
checked! It isn't a matter of preference, rather an imperative. In other
applications where actions mostly relate to just viewing information, it
doesn't matter so much where access is checked as long as it is any time
before data is sent to the client browser. And in this realm, I wouldn't
dare suggest that there is ONE right answer, or even that my view is
better, since I recognize my inexperience.
--Seth
-----Original Message-----
From: Matthew Weier O'Phinney [mailto:matthew@zend.com]
Sent: Friday, August 28, 2009 1:23 PM
To: fw-mvc@lists.zend.com
Subject: Re: [fw-mvc] MVC integration of Zend_Acl
-- Seth Atkins <satkins@nortel.com> wrote (on Friday, 28 August 2009,
12:52 PM -0500):
> Two main comments from my part. The first is a fairly open ended
> question I can't answer for you. While an action helper may fit your
> needs very well, IMHO, a successful integration is one which serves
> many common approaches and is the least limited implementation. For
> example, some of the comments so far have related to treating actions
> as resources. Many people see actions as privileges on resources, and
> one common view of what a resource is is a controller resource. If
> this is such a person's view on the subject, an action helper seems
> fairly limited since you are dispatching to a controller before you
> actually check resource access. I'd rather back things up a few steps
> and check before any particular resource is called. But that is my
> opinion, and I do know I'm not alone there. I believe, and correct me
> if I am wrong here, but the action helper preDispatch() method is
> called after the controller init(), which is also after any controller
> preDispatch() method, which is also after any plugin preDispatch
methods.
Close, but not quite. Order is:
front controller plugin preDispatch
action helper init()
controller init()
action helper preDispatch()
controller preDispatch()
The only place you can circumvent is at the plugin preDispatch(); if you
call _forward() later, it will continue to execute through the
controller preDispatch(); the only thing skipped will be the actual
controller action (and postDispatch, of course).
> Seems to me a lot has happened before you ever checked to see if any
> of that should have happened in the first place.
>
> I am less familiar with all the things you can do with an action
> helper and how one might wrest it to do your will. My understanding of
> the ZF plugin architecture is more detailed since I have spent some
> time tracing through the code, how plugins are called, when, etc.
> Anyway, I know that plugins can do exactly what I want, but I'm less
> sure that an action helper would fit my needs.
What action helpers provide you is integration with the action
controller. Basically, you can place metadata or methods in your action
controllers that the action helpers can then query (or manipulate) to do
things.
Some examples of such integration:
* ViewRenderer: sets the view object, as well as renders the view
script postDispatch() based on the action executed
* ContextSwitch/AjaxContext: if certain properties are set in the
action controller, will query those to determine if a context was
invoked, and, if so, change the view script rendered (as well as
potentially inject response headers)
Basically, what action helpers do is make it easier to place the context
for a decision close to the decision point.
However, as you note, there may be a performance cost associated with
this.
> The second comment is that plugins are called before ANY dispatching
> (of any sort) occurs. Not even a controller init() method has been
> called yet. I can create one plugin, set it up in Zend_Application,
> and all my ACL code is in one place, once line of code to setup the
> plugin, and I'm done. The plugin is post routing, so it has the
> filtered request object to work from. You can load your rules and then
> feed isAllowed your controller or action name, or whatever criteria
> you want. If you want actions to be resources, fine. If you want
> controllers to be resources and actions privileges, fine.
>
> And best of all, a plugin can alter the request object before
> dispatching occurs. So I can actually redirect without "redirecting",
> if you know what I mean, in response to access being denied.
>
> To sum up, I don't think an action helper would be an implementation
> that I would personally want to use.
You have valid points. The points in the proposal are also valid. They
are very different approaches, however, and there are different
ramifications involved with both. In your situation, you get good
execution speed -- but at the cost of having to update ACLs and
controllers separately. In the approach proposed, your ACLs are part of
your application structure, making maintenance easy -- but you lose some
performance.
As I noted earlier, I personally like to put my ACLs with my service
layer. This means that I'm actually executing my action before I find
out if the user has the ability to do something -- probably your worst
nightmare.
However, what this affords me is the ability to re-use my service layer
for web services -- I can create a service proxy object that I attach to
Zend_XmlRpc_Server, Zend_Json_Server, Zend_Amf_Server, etc -- and my
ACLs continue to work as expected. I don't have to do anything different
whatsoever.
> I have many modules, many controllers, many actions, and while, yes, I
> could write one action helper and call it from anywhere, I'd really
> rather not have to write 50 lines of code to just to call it from each
> controller I happen to have. And I'd rather not instantiate a
> controller that a person doesn't have access to in the first place.
> Just my 2 cents.
Again, as noted above: there are different approaches. Use the one that
suits your application and/or programming needs.
> -----Original Message-----
> From: jThierry [mailto:thierry@jossermoz.net]
> Sent: Thursday, August 27, 2009 9:44 PM
> To: fw-mvc@lists.zend.com
> Subject: [fw-mvc] MVC integration of Zend_Acl
>
>
> Hi all,
>
> I've been working on a component to realise the MVC integration of
> Zend_Acl which is different from the proposal
> (http://framework.zend.com/wiki/pages/viewpage.action?pageId=39025)
> that seems to be on hold.
>
> I'm using an action helper the perform the checks at pre dispatch time
> on controllers implementing Zend_Acl_Resource_Interface instead of a
> plugin and am wondering if there's any underlying reason that would
> encourage the use of a plugin.
>
> I would really much appreciate your feedback on the action helper
> approach.
>
> The code can be found there: http://code.google.com/p/oolala/
>
> Thanks,
>
> Thierry
> --
> View this message in context:
> http://www.nabble.com/MVC-integration-of-Zend_Acl-tp25183254p25183254.
> ht
> ml
> Sent from the Zend MVC mailing list archive at Nabble.com.
>
>
--
Matthew Weier O'Phinney
Project Lead | matthew@zend.com
Zend Framework | http://framework.zend.com/
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