David Jencks wrote:
There are 2 or 3 proposals that are getting mixed up here..... I'll try
to separate them.
1. hierarchical roles. This is a big part of the NIST RBAC model and
looks easy to implement in tsec to me. AFAICT a role would have granted
permissions, denied permissions, and a set of sub-roles.
Ok this is different as we already discussed than what tsec does today
but that's fine.
We'd
presumably need to implement something to prevent cycles in the
resulting graph.
Yeah exactly.
A role would imply a permission if some granted
permission in on of the set of role + transitive closure of sub-roles
implies the permission and no denied permission implied it.
Sounds like a good way to devise the composite implies for the role.
If and only if we do (1), we can think about (2)
2. The role above is almost the same thing as the current profile: as
far as data the only difference is that profile has a user attached.
That's a big thing to undo.
If
we associate users and profiles in some other way we can eliminate the
concept of profile, simplifying the model considerably.
This is a problem. Whether or not you call it a profile does not
matter. Call it anything you like.
To avoid having to muck with a user's entry you need some other entry to
store the roles associated with that user. It's like a record in a link
table in the RDBMS world. We just so happen to call that the authz profile.
If you muck with the user entry you make Tsec pretty useless in
enterprise scenarios where many will want to use a pre-established user
credential store like Active Directory.
There's the
other difference that roles are all loaded at startup and profiles are
loaded on demand.
Right since the number of profiles in the system ~= # of users and this
can be in the millions.
If loading everything at once turns out to be a
problem perhaps a LRU cache would work: in any case this does not
necessarily affect the data model.
Roles and permissions are preloaded because the number of permissions
and roles for applications are usually tiny in comparison to the
unbounded number of user profiles you can have.
Furthermore on startup without having any users logged into an
application an application can inquire about what roles and or
permissions are used.
Note that there's already a big
problem with the current association between users and profiles that
people are proposing to fix with a "groups" concept.
leading to
3. The current association between users and profiles is problematical,
independent of (1) or (2)
a. without something like groups, you get too many duplicated profiles,
which is unmaintainable. So, associating each profile with exactly one
user doesn't work. We need to do something else.
Yes this is why the group profile concept came about. You can still
fine tune this with having individual user based profiles.
b. I think the NIST model incorporates the idea of switching roles in an
app perhaps without logging in again. I'm pretty sure I've seen this
idea elsewhere. This is not supported by the "log in as your profile
id" concept.
Not necessarily. I think you're mixing some ideas here.
You're bringing in your conceived notion of a user's role here.
Strictly wrt to triplesec what you're talking about corresponds to a
triplesec profile. Apps can be designed to allow you to switch your
profile (which is what you're thinking about instead of role).
c. I'm not sure how the groups idea is supposed to work, but in my
mind's model I don't see it working.
Ok take a breather :). Step back and check this out. Users log into
applications using some login id. It could be anything ... it's up to
triplesec and it's login module to interpret that based on what is
defined within the application.
Triplesec will use the following algorithm to figure out what that id
corresponds to:
(1) check to see if the login id is a profile id of a profile defined
specifically for a user
(2a) if so the user is dereferenced and authentication occurs
(2b) if no profile exists, the id is presumed to be a user id in which
case we continue to #3 below
(3) check to see if a user exists with the login id, if so continue to
#4 if not reject access by the user to the application
(4) check to see if that user is a member of a group profile defined for
the application
(5a) if the user is a member of a group profile authenticate the user
and enable the user with the permissions associated with the group profile
(5b) if the user is not a member of any group profile deny access to the
application by that user
This is pretty straight forward to implement. As far as the application
is concerned no one cares what the login id is actually for or represents.
As far as the tsec admin is concerned he manages profiles for
individuals and for groups. Sometimes individual profiles are preferred
for special people and sometimes not. The admin is happy because he has
the power to group users and the power to work specifically with
individuals.
Now we are requiring you to supply your userId,
password, and profileId. This doesn't fit most login systems that well
AFAIK.
I agree with you completely but that's not what we're trying to do.
Ignoring any possible implementation for the moment, I wonder if we can
agree on the data model characteristics for this. From (1) and (2) we
may end up calling a bunch of permissions that can be associated with a
user a role or a profile: I'll try to remember to call it a profile even
though I think calling it a role is better :-) So:
Hehe yeah we need to agree on our jargon. We need a darn glossary
you're right.
Again to do this you have to understand the real world constraints on
us. We cannot put what is today in the profile into a user entry. So
we need something to associate roles with users. Just pick an name for
what this entity is to be called and we can call it that.
A. I think we need a many-many association between users and profiles.
Yep that's the group profile. It's a new construct that refers to a
group instead of a user.
This means the user ID by itself doesn't
determine the profile and the profileID by itself doesn't determine the
user.
True but there will be a way to determine this from the other side by
being provided a login id. The evaluation of what that corresponds to
will be handled by tsec using the heuristic I wrote up above.
B1. To cater to systems that can only accept userID and password, we
could have a "default profileId" for each user. This gets you past
authentication to the point where the system can show you your available
profiles and you can pick one to change to.
Yeah this is too weird and we don't need to do it.
B2. Alternatively if there was some way of having lots of aliases for
users that could be linked with unique profiles you could log in with an
alias and that would determine a profile.
Again I don't think this is at all necessary.
B3. ??? Maybe we need more ideas or a better explanation of the groups
idea?
Yeah I hope the above explanation (heuristic) helps with that. If not
we can discuss this a bit more.
Moving over to implementation Alex points out that we can't rely on any
info being attached to users in the same place their authentication info
is stored. So, we have to store it with the application data somehow.
So, one easy thing we could do is have a ou=Users area in the
application where we store an entry for each user, with an ordered list
of profileIds. This is just an idea, not necessarily a good one.
Hmmm this may be another way. Basically your ou=users container under
applications is almost the same as ou=profiles. Why?
Because what's in there is not the user themselves but references to
profiles associated with them. However this is not good because you
still don't know which profile to associate with a user logging in.
On Jan 10, 2007, at 1:48 PM, Alex Karasulu wrote:
David Jencks wrote:
On Jan 8, 2007, at 12:58 AM, Alex Karasulu wrote:
David Jencks wrote:
On Jan 2, 2007, at 3:02 AM, Ersin Er wrote:
Hi (David),
I have two simple connected questions:
Is JACC basically a RBAC (Role Based Access Control) system?
If it's, do you think its model can be mapped onto the following
RBAC model:
http://csrc.nist.gov/rbac/rbacSTD-ACM.pdf ?
The NIST model for RBAC is quite sophisticated and can meet most of
the RBAC model requirements. We cannot implement this fast and it's
not our first priority but I am just dropping an email to keep
this in
mind. We would also like to support XACML and its RBAC module in the
future so we'll have a stable core and a service layer that can
easily
be adopted by providers as JACC. Lots of TODO.. :-)
It took me a long time to actually read the paper.. still not quite
done. I think we should be careful to make sure triplesec is
consistent with the NIST model and implement as much as we can to
start with.
+1 Incidentally this is one of the biggest issues we're going to run
into. I read somewhere in the JACC spec that it does not address
the need for RBAC so there may be some impedance mismatch here.
JACC basically makes the role >> permission mapping specified in
the j2ee/jee deployment descriptors somewhat more explicit, in
particular specifying the java classes for the permissions. It
leaves the identity >> role mapping up to the implementation. I'd
say it's consistent with RBAC but not the whole story.
Hope you're right - I really haven not been able to get a clear
picture of JACC up to this point.
A lot of the spec is not a model of clarity. It's really unclear on
who can change the role >> permission mappings when. On the one hand
it seems to state that they are determined by the spec deployment
descriptors, so presumably to change them you should redeploy. On
the other hand it provides a peculiar api for changing them, but
doesn't say who is supposed to use it other than deployment.
I'm hoping triplesec will provide usable administration.
I'm thinking that perhaps we could implement the role hierarchy
features of the NIST model by combining the role and profile object
classes: i.e. each role could have subsidiary roles as well as
granted and denied permissions. This might simplify the data model
as well as making it more powerful. I haven't read the admin
features part of the model yet.... this seems likely to be the hard
part.
It does seem to me that with a role hierarchy it's only necessary
for a user to be in one role at a time, since you can define the
set of roles they are in to be yet another role.
I talked a bit with Alex about the user <> role association and I
still don't think we've found a good solution: I'm not very happy
with the current restriction of 1 user for a profile but don't
really have a better idea. I don't yet see groups as providing a
big improvement.
Another approach can be to create a special group profile. Instead
of the profile referring to one *user* the group profile would refer
to the DN of a *group* using say a group attribute. This way users
in a group that is referred to by a group profile can gain access to
the application with the effective permissions defined for the group
via the group profile.
WDYT?
I'm not happy with this yet, but maybe I just haven't thought it
through enough. It seems to me that hierarchical roles make profiles
redundant,
Hmmm I don't know if I would agree with that. A profile is a place
where we can aggregate and associate a user with roles and other
tweaked permissions for an application.
Hierarchical roles would just help as an administrative tool to do
RBAC better essentially with less verbosity.
They seem to be an important part of the NIST model.... and I think
supporting them simplifies and clarifies our data model. However it's
not essential.
I would agree with you on this one. Many people ask for it so
supporting it is not a bad idea.
Basically view a profile as a security profile. You have profiles in
apps that track your user specific settings. This profile is just the
same. It tracks your authZ settings or the application.
I thought user profiles were usually modifyable by the user. IIUC this
would normally not be the case for security profiles.
Whether or not a profile is modifyable by the user is irrelevent.
Writability is orthogonal and unrelated to whether something is or is
not a profile.
Users will not be able to modify their profiles or even read them.
so I want to link users and roles, with the idea that a user can
choose one role at a time (like they can now choose one profile at a
time if they have several profiles). So to my mind there's a
many-many relationship between users and roles.
A user can be in any number of roles within an application. And a
role can be taken by any number of users in the same application.
I suspect this is getting hard to understand between hierarchical roles
and profiles. With hierarchical roles, what we are now calling a
profile is a role + userId.
Not really. A user profile also has tweaking attributes to grant or
deny permissions that may or may not be inherited from roles assigned to
the profile.
So saying that every user is in exactly one
role at a time is exactly the same as what we have now.
No I disagree with this statement. You're basing this on the
presumption that a profile ~= role which is not correct.
One of the problems I have here is wondering how the ui for logging
on is going to work. In say a web app you can usually only supply
the username and password to log on. How do you then specify the
role (or profileId)?
The username would be the profileId. Basically the profileId usually
is the same as the username 99.99% of the time.
As noted at the top, I don't think this works.
Again I think you're basing this conclusion on a misunderstanding.
Behind the scenes the login module/triplesec will determine what
actual user that profileId corresponds to. Note the user is only used
for doing the authN.
Why is this separation a good thing you might ask?
Well sometimes the user info will not be contained in tsec although it
might be. Instead the users may be in the companies ActiveDirectory
or in another data source that Tsec will chase a referral to.
This way we can store app specific profile information in tsec even if
the users and their credentials for authentication are maintained in
another store.
I didn't get that earlier.... I agree completely.
Cool. Then it becomes a question of how we satisfy these constraints
while doing RBAC (satisfy nist) with LDAP and working well with JACC.
I think it would be nice after authenticating the user to
provide a list of their role/profile choices. It seems really
strange to me to provide the role/profileId as your user name....
You would not provide the role as your username. Just the profileId
but the user will never need to know this unless the user needs
different profiles on that same application.
Again, I was mixing up too many things at once. I'm using roleId to
mean what we now call profileId.
Yeah this is not going to work. I think we just need to talk more about
this.
Sometimes you might have an alex user with both an alex and an
alex-admin profile. One may allow more privs than the other.
You asked then why don't you just create two users instead. Well then
you would have different passwords for each user. And what would you
do if that user was not in fact stored in Triplsec but stored in
ActiveDirectory and some delegation/proxying was required? Also it's
the same user so we want to correlate the audit trails.
The two user alternative is not sound IMO.
I agree, multiple users is a non-starter.
Great.
So I guess one way to do this is to have a login page, which results
in you getting to a low-permissions role that then lets you change
roles, giving you a choice. Basically this gives each user a default
role, which is handy for the perhaps common situation where in fact
each user only has one role.
I don't think any of these measures are necessary.
I hope you're right but don't see any alternative yet.
We're getting there I think... Hopefully my response in this email will
clarify some things.
I think alex tried to explain to me what the problem was with giving
each user a multi-valued attribute of their roles/profiles but I'm
not remembering it clearly enough to still believe it :-( and it's
seeming like a good idea to me...
Hmm let me see ... instead of having a profile for the user you want
to stuff role information as attributes into the user entry to form
associations that way?
To avoid mixing up 3 ideas lets call it profileIds for now :-)
This is a very bad idea IMO. Reason being that again we may be
proxying users from ActiveDirectory for example. This will be very
common. If so no Domain Admin will want to mess with the AD schema to
add triplesec or application specific schema elements to it.
Let me make a clear statement that the user credential store may not
be Triplesec while the application specific policy will be. Most
enterprises will not change their central credential store but need to
leverage it.
I get it now :-)
Great.
so I'm thinking of a required single valued attribute defaultRole and
an optional multivalued attribute roles in a new object class that we
can attach to users (or groups).
Again this is not a good idea. Easy to do and we can do it for sure
but it will make this solution very inflexible for real world use cases.
So, I now agree we certainly can't attach this to the credential store.
I wonder about keeping this info in the application though. This also
makes more sense since profiles or roles generally won't go across
applications.... another reason attaching it to the user/credential
store is a terrible idea.
Glad you recognize this.
When you log in you get the defaultRole,
but then you can change to one of the others. Why wont this work?
This is a very convoluted IMHO. It could be made to work .. many
things can be made to work but this is not the question. Whether it
is going to lead to a viable enterprise solution is the question.
convoluted == bad, viable == good :-). I'm not convinced we have any
viable solutions yet though...
:)
[NOTE: goal discussed below is wrt authZ aspects of tsec]
The goal of Triplesec is not to become a simple JACC implementation in
which case you can just use some flat file with some custom syntax to
represent policy as a simple static policy store.
It's supposed to be a central service to administer & control policy
for applications across the enterprise which works for real world
scenarios.
IMO jacc won't really mean anything useful until there is something like
triplesec hooked up that allows meaningful administration. That's why
I'm so excited about trying to hook it up to jacc.
Yeah me too ... glad you're so enthusiastic about this. Finally someone
besides me is too :).
This is why LDAP comes into the picture.
I think we need some more conversation around these concepts so we can
re-approach the JACC integration problem. I don't understand JACC
enough and perhaps Triplesec still alludes you a bit. We can do it
though please bear with us. We will find the solution.
Regards,
Alex
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