On Tuesday 08 July 2008 12:43:42 Andrea Aime wrote:
> David Winslow ha scritto:
> > Hi all,
> >
> > I started writing this email before I realized how long it would be, so I
> > have copied what I was originally going to say into
> > http://geoserver.org/display/GEOS/GSIP+25+-+Pluggable+Authentication+Mech
> >anisms on the wiki. This is just me musing on bugs
> > (http://jira.codehaus.org/browse/GEOS-1579 and GEOS-2000) so there's not
> > a specific use case driving it, but I think now (with GS 2 coming up) is
> > a good time to give some serious forethought to security configuration.
>
> I read the wiki page a few of times and I'm still a little
> confused, so sorry if my comments are off the mark. But here we go.
>
> > -David Winslow
> >
> > I have been doing some thinking about pluggable security systems in
> > GeoServer. (inspired mostly by http://jira.codehaus.org/browse/GEOS-1579)
>
> This jira states:
> "Make it possible to use different authentication providers by
> leveraging a plugin mechanism plus some settings in web.xml so that
> people can choose to use geoserver built in authentication provider, or
> JAAS one (in the specific, Tomcat's version, since JAAS authorization
> setup is container dependent, sigh) or whatever other provider the user
> may fancy to develop as a module."
>
> It is not at all about the zones, but about being able to pick up the
> provider that will authenticate users and give back the roles list,
> so something that would act as a replacement for users properties.
>
> This seems to me the most important aspect of a pluggable authentication
> mechanism. Is it what you're talking about when you're showing
> the example relating to the web.xml configuration?
Right. This basically amounts to having the different zones completely
defined in code, and referred to by name in some configuration file. I
mentioned putting these in web.xml mostly because the JIRA issue suggested
that's where they should be, but I agree with you about the data dir being a
better place for them.
> In my opinion the choice of security authentication mechanism is
> something that should be stored into the data directory, not in web.xml,
> so that you can move it around along with the data dir, and so that you
> can change it even in containers that do not unpack the war.
>
> The only thing you have to change in web.xml, should you need to,
> is the removal of the Acegi filter altogether... that's something we
> could think of making configurable outside of web.xml as well,
> it's just a little harder than the rest.
>
> > Right now we
> > have at least two "sections" of GeoServer which are guarded by different
> > authentication mechanisms, but share a database for authorization.
>
> The authentication mechanism is one as far as I know, it's the
> authorization mechanism that's different depending on how
> you access GeoServer?
We use HTTP basic auth for authentication in OWS services, and a 'custom' (not
really, since it's provided by Acegi) form + cookie system for the admin page.
These share the roles database (which is used for authorization, but not
sufficient for determining whether or not to deny a request), but use (very)
different rules for determining which roles are required for a request.
Apologies if I'm misusing terms here, I'm pretty green wrt security
discussions.
> > However, right now all that's available to users ("users" at the
> > moment being those willing to modify web.xml and some properties files by
> > hand) is the option to assign roles and passwords to users, and to
> > restrict either layers (if we include Andrea's recent work) or service
> > methods to a subset of those roles. That is, there are three
> > configuration sections relevant to security:
> >
> > <users.properties>
> > defines user, password, list of roles
>
> This is authentication, built in mechanism, something I would love to
> see as pluggable.
>
> > <layers.properties>
> > defines layer, read/write, list of allowed roles
> >
> > <service.properties>
> > defines service, operation, list of allowed roles
> >
> > <rest.properties>
> > defines URL, HTTP method, list of allowed roles
>
> This is authorization, decomposed in two orthogonal ways, data and
> services. This could (should) be made pluggable as well, thought
> it's probably a bit less important than making authentication pluggable.
>
> > What's not at all user-configurable right now is the authentication
> > mechanism used to find out what user is accessing GeoServer. We just
> > have the following hardcoded:
> > for the admin console, use an HTTP cookie, redirecting to a form if the
> > cookie is not found OR if the user is not in the required role (which is
> > also hardcoded).
> > for the OWS services, use HTTP basic auth, returning a 401 error when
> > permission is denied.
> > for rest stuff, no authentication is implemented.
> >
> > So we have GeoServer kind of divided into security 'zones;' the admin
> > console is one; the OWS services are another, and the REST stuff (or
> > maybe just the rest) constitutes a third. It might be nice for users to
> > be able to define these zones themselves, but right now they seem pretty
> > radically different in structure so that should probably wait until we
> > have enough use cases to better define them. Each zone has not only its
> > own authentication mechanism, but also its own type of restriction rules:
> > admin console: it's just 'you have to be in ROLE_ADMIN'
> > OWS service: layer+access or service+method -> list of allowed roles
> > REST API: URL+HTTP method -> list of allowed roles
>
> Admin console wise, seems like saying unix is not flexible
> enough because admins have to be in the ROOT group. What am I
> missing? ;)
To be pedantic: admins DON'T have to be in the root group; if you divide the
system into different sections you can assign UNIX groups based on what is
needed (ie, groups for database, webserver, etc.). One concept that Tim
Schaub was discussing when we were talking about REST was to have separate
admin permissions at each level of the hierarchy (this is similar in principle
to adding 'a' to the ACLs in the current layer security configuration). It
would probably be quite annoying to deal with, and maybe it's more
configurability than it's worth (ie, the number of users who would actually
benefit are not worth the amount of work it would be to do this, or the UI
clutter that would be added). But if we are talking about massive GeoServer
installations then it's probably at least considering supporting allowing
different groups of admins.
> > For a first stab at pluggable authentication mechanisms, maybe it's
> > sufficient to just let users set the mechanism for each of these zones
> > individually; it could be as simple as including a set of parameters in
> > web.xml that are expected to be class names of authentication plugins,
> > something like
> >
> > <context-param>
> > <param-name>OWS_AUTHENTICATOR</param-name>
> > <param-value>org.geoserver.acegi.HttpBasicAuthenticator</param-value>
> > </context-param>
> >
> > Bean names could work here as well. The default values would just
> > emulate the current authentication system, and the current properties
> > files would still be used for the authorization tasks.
> >
> > In the long run though, it may be that users would like to be able to
> > define their own zones (example use case: multiple REST plugins are
> > provided that need to provide access to different clients; so you want to
> > allow two different authentication mechanisms to clients using different
> > subsets of the REST API). Since a zone as I've defined it is just a
> > subset of GeoServer's functionality combined with an authentication
> > mechanism and a type of rule, we could probably have just a file
> > zones.properties that looks something like:
> >
> > <zones.properties>
> > #prefix[,prefix...]=authenticator,filter[config[,config]]
> > /config/=org.geoserver.acegi.FormAndCookieAuthenticator,org.geoserver.sec
> >urity.AdminOnlyFilter
> > /ows,/wfs,/wms,/wcs,/wfsv=org.geoserver.acegi.HttpBasicAuthenticator,org.
> >geoserver.security.MethodAndLayerFilter(service.properties,layers.properti
> >es)
> > /rest/=org.geoserver.acegi.HttpBasicAuthenticator,org.geoserver.security.
> >HttpMethodFilter(rest.properties)
>
> Here I'm loosing you. The authentication mechanism should be one for
> the whole server imho... do you want the console to use the built in
> mechanism and the services to use a LDAP server instead? In the long
> run I would also love to see the authentication mechanism configurable
> from the user interface, like a drop down listing "built-in", "JAAS",
> "CAS", "LDAP" and so on, but still be used "server wide".
Okay, it seems that I have been misusing 'authentication mechanism' so far to
refer to ways of getting authentication information from the client, rather
than validating and getting the role list from the credentials provided. It
does seem to make sense to have that database shared across the different
'zones'.
> As for the path based approach above, hum, I'm uncertain.
> It seems inspired by the acegi ant based filters defined here in
> the Acegi configuration file:
> http://svn.codehaus.org/geoserver/trunk/geoserver/main/src/main/java/applic
>ationSecurityContext.xml but they don't look like a replacement of all the
> structure that's being set in place.
>
> Usually with Spring you define the static part of your application,
> and there is code in the application that handles the dynamic part
> by using lookups.
>
> For example, if I were to create a pluggable authentication system,
> I would declare in the applicationSecurityContext.xml a
> GeoserverAuthenticationManager that would be just a router, and
> it would decide what actual authentication system to use by
> looking into the spring context (for pluggable authenticators)
> and in the configuration (to see which one the user chose to use).
> Failing the lookup, it would know how to fall back on the default
> authenticator.
>
> What I would see as doable is having pluggable authorization
> classes able to handle data, rest and ows authorizations, using
> the same approach as above (router class + lookup and default
> implementation), so that you can roll your own way to authorize
> calls as needed. But it seems to me each zone would retain
> its own peculiar way to do the authorization, OWS by parsing
> the request and coming up with a service and a method (eventually
> a version, the request params), REST by the resource path,
> what I see as pluggable is the way you use to associate
> those tokens to a list of roles.
> Doing the same for the actual filter chains that performs the
> cookie handling, sessions integration and such is harder thought,
> the Acegi list of filters is critical, you can make it not
> work at all by just listing the filters in the wrong order.
>
> Consider how many changes you'd have to
> do in order to use Digest authentication in place of the
> basic one, you'd have to declare new beans, wire them up
> in a different way. Do you really want to expose that to the user?
>
> Also, I don't easily see how the above zones configuration and the Acegi
> configuration could work together, do you already have a plan?
I had in mind the zones configuration replacing the current setup; if
everything is user configurable then you should never need to mess with
settings in the source code. But nothing terribly concrete thus far. I may
have given the wrong impression by listing this as a GSIP on the wiki
(although it is definitely up for discussion).
> Cheers
> Andrea
>
>
>
>
>
> !DSPAM:4040,4873994532951804284693!
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