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From "Alan D. Cabrera" <l...@toolazydogs.com>
Subject Re: Unauthorized URL for different entries in filter chain
Date Mon, 27 Jun 2011 04:46:41 GMT
I like approach #1 and don't care so much for #2.  :)  Creating a filter just so that you could
set a property in other filters seems a bit awkward; it's not a mixin, imo, since all the
participating filters have to be prepared to collaborate ahead of time.  

/whatever/** = someFilter, roles[admin, unauthzUrl=/service/notadmin.jsp]

How would this work from a filter's perspective?  We can keep a single instance of a filter
around and it handles all requests or we can create a new instance of the filter per call.
 The former would be backward compatible so I'll discuss that first.

When set of filters match a path, a set of the filters's methods are called by the framework.
 This allows the filters to participate in the framework's processing of the client's request.
 Let's say that these methods are foo and bar.  The methods foo and bar have a set of required
arguments; these would be the arguments that Shiro 1.1 has.  But some filters could have additional
parameters and we map the key/value pairs in the filter chain config to those parameters.
 For the roles filter foo could be:

foo(ServletRequest request, ServletResponse response, String mappedValue, String unauthzUrl)

for the someFilter it would be:

foo(ServletRequest request, ServletResponse response)

where the last signature would have a default do-nothimg implementation.  The only problem
with this is that the current implementation extensively uses class inheritance to extend/override
features and it's not clear to me that we have a concise set of "event" methods between the
framework and filters; the events seem to be buried inside abstract classes.

The other way is for if we create the filter per request; something we are apparently thinking
for 2.0.  When we create that instance set we set it's bean properties from the key/value
pairs in the filter chain config.

Thoughts?


Regards,
Alan

On Jun 26, 2011, at 12:14 PM, Les Hazlewood wrote:

> Hi Alan,
> 
> Yep, that's one of two ways I can see this working (although I'd
> probably represent the string a bit differently - see below).
> 
> Approach #1:
> 
> Have url configurable on a per-request (e.g. per path) basis like
> you've shown, available to any of the AuthorizationFilter subclasses.
> 
> I'd probably represent this as a named key/value pair in the config
> string, e.g.:
> 
> /whatever/** = someFilter, roles[admin, unauthzUrl=/service/notadmin.jsp]
> 
> This way the string is a bit more specific and allows any configurable
> property to be configured no matter the order it is written.  A little
> nicer so people don't need to remember a particular string format or
> potentially leave empty spaces if other fields are introduced in the
> future (e.g. admin||somethingElse)
> 
> I believe this approximates more of what the 2.0 codebase will probably be like.
> 
> Approach #2:
> 
> Have a filter that configures the URL as a request attribute so any
> filter in the chain can react to it as needed.
> 
> This is my preferred approach and is definitely how the newer filters
> (and whatever mechanism we choose for 2.0) will probably work.  This
> technique is what will allow end-users to not have to subclass Shiro
> Filter classes so much since they can inspect the request in whatever
> way they wish.
> 
> For example:
> 
> /whatever/** = unauthzUrl[/service/notadmin.jsp], someFilter, roles[admin]
> 
> The 'unauthzUrl' filter will place the configured URL in the request
> as an attribute (request.setAttribute) using a well-known key.  Then,
> any AuthorizingFilter subclass (roles, ssl, perms, etc) can lookup
> that attribute if it exists.  If it exists, they redirect using that
> url.  If it doesn't exist, then they fallback to their
> 'unauthorizedUrl' property.
> 
> I believe both approaches should be supported, but I prefer the 2nd
> approach due to how clean it feels to me - it feels more like a
> 'mixin' which is much more flexible than subclassing (which we'd like
> to move away from as we've discussed).  It is definitely backwards
> compatible too (new support would be added, but existing functionality
> wouldn't be lost).
> 
> Thoughts?
> 
> Cheers,
> 
> -- 
> Les Hazlewood
> CTO, Katasoft | http://www.katasoft.com | 888.391.5282
> twitter: http://twitter.com/lhazlewood
> katasoft blog: http://www.katasoft.com/blogs/lhazlewood
> personal blog: http://leshazlewood.com
> 
> 
> On Sun, Jun 26, 2011 at 11:47 AM, Alan D. Cabrera <list@toolazydogs.com> wrote:
> 
>> Looking at the code I'm wondering if I shouldn't extend the particular filter to
do something like this.
>> 
>>       <property name="filterChainDefinitions">
>>           <value>
>>               /admin/** = myFilter, myRoles[admin|/service/notadmin.jsp]
>>               /work/** = myFilter, myRoles[verified|/service/notverified.jsp]
>>               /owners/** = myFilter, myRoles[owner|/service/notowner.jsp]
>>               /account/** = myFilter
>>           </value>
>>       </property>
>> 
>> No code changes needed then.
>> 
>> 
>> Regards,
>> Alan


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