Re: Howto refresh IIS 6 Application pool identity credential info
- From: Peke <peke@xxxxxxxxxxxxx>
- Date: Wed, 5 Mar 2008 23:47:00 -0800
David,
Thx for the response. I understand what is going on so I'll have to discuss
this with our security people.
In your previous mail, you mentioned something about 'lazy read', no recycle
on config change; how is this done ?
Kind regards,
Peter
"David Wang" wrote:
I'm sorry, but I do not have any suggestions. I understand what you.
are doing and it is pretty clever to a degree, but I believe there are
fundamental problems with your design beyond just incompatibility with
IIS6 that you must choose another design.
IIS is being consistent with security while what you are doing is not
consistent with security (but I do admit it is clever and can be
convenient in some contexts), so it is unlikely IIS will change. I
understand that you have an existing codebase that is being migrated,
so it is really not going to change. So the design has to change.
For example, your design either serializes access to the webserver to
one user at a time, or it is insecure. How? Proof by contradiction --
assume two different users belong to two different user groups have
authorized access overlapping in time. User1 comes in and the AppPool
identity changes group membership to have Group1 and accesses data.
While this is happening, User2 comes in and the AppPool identity
*needs* to change group membership to have Group2 and access data.
What if the two groups are different or conflicting in access
privileges -- you certainly do not want User1 to temporarily have
access to files of User2 simply because your AppPool Identity
momentarily has group membership in both Group1 and Group2 while both
users are accessing different resources through the same system at
overlapping times. Thus, to be secure, the process identity must be in
only one Group at a time, which means that only one user can be
actively using the web server at a time --> this is serialization. Or
if you allow multiple users simultaneously it means that User1 will
temporarily run with a process identity that is in both Group1 and
Group2, thus have additional and/or contradicting privileges --> this
is insecure.
Also, what if the action triggered by the user is asynchronous? How do
you ensure that the user group membership of the Process Identity on
the async callback is the same one as when the call was first made?
Remember, the async callback can happen at any time.
The only secure way to use your authorization scheme using Group
Membership is to make everything synchronous and single user, which
works but will never scale.
Basically, your design looks clever and avoids passwords, but it is
really not feasible when you look at the details. You basically mapped
Roles to Group Membership and to avoid passwords you chose the Process
Identity. However, this fails for all the reasons I stated above, so
IIS never allowed such behavior in Application Pool Identity (let's
not even get into how your scheme plays havoc with Web Garden, or Skip
Process Recycle on Config Change).
Impersonation with user identities and having delegation enabled on
credentials with static and diverse Group Membership flowing through
the system is really the built-in option of how to be secure and
scalable. AzMan approach is a suitable alternative where the Roles are
dynamically bound.
//David
http://w3-4u.blogspot.com
http://blogs.msdn.com/David.Wang
//
On Mar 4, 11:08 pm, Peke <p...@xxxxxxxxxxxxx> wrote:
Hello David,
Sorry for the delay.
I'll try to explain how our applications work.
We develop .NET application using multitier-layer (UI, Webservice, ...).
We've build our own application security, comparable to AzMan, which wasn't
available at that time (Windows 2000 Active Directory) ; it is based on roles
and privileges.
IIS (6) is configured to use 'Integrated Security'.
Basically : users are put in a group (or removed from if they no longer need
access) that has Read rights on the filesystem where the IIS virtual
directory (or IIS virtual server) is pointing to.
The user's privileges are checked in the business part (Business Facade),
and from that point de application pool identity (a domain user) is used to
access the data store(s).
That 'data store' can also be another WebService (Service Agent).
--> this is where the problem is : the application pool identity is becoming
a member of another group to get access to the other application. But the
security context is only 'refreshed' after IISRESET.
A few reasons why we do it that way :
- Easy security maintenance on the data store (only the application pool
account needs the necessary rights).
- A developer doesn't have to do anything special in code.
- Application pool identity password is not available in code (and can't be
mis-used; if we would use impersonation -using config file or in code - then
the password would be available).
I hope this makes any sense.
Do you have any suggestions ?
Kind regards,
Peter
P.S. You mentioned something about 'lazy read', no recycle on config change,
how is this done ?
"David Wang" wrote:
Can you explain why you want to dynamically change the security
permissions on the Application Pool Identity user?
The reason why SetSPN is failing is the same sort of logic behind why
you cannot dynamically change the security permissions on the
Application Pool Identity.
Imagine this scenario -- you have a web garden with lazy read (i.e.
don't recycle on config change) enabled, and you change permissions on
Application Pool Identity. *IF* things changed immediately, you end up
with w3wp.exe each with different security permissions and further
security implications.
Or in your scenario, what happens if two users which required
different permissions on the Application Pool Identity try to use the
same application served by the same application pool. The w3wp.exe can
only have one process identity, so one of those two users must wait
until the other is done -- not a good user experience.
Basically, we did not design for Process Identity changing on the fly
like that - we designed for thread impersonation to be changing on the
fly like that. The Process Identity is the base unit of isolation.
Impersonation is the base unit of functionality.
Is there anything that prevents you from using a single domain account
as Application Pool identity, and you dynamically impersonate
(depending on your application framework layer, this may be easy).
Because when you do that, SetSPN will also work against your single
fixed Application Pool identity, and I believe impersonation flows
outward on your next hop to the DB, FileSystem, etc.
//David
http://w3-4u.blogspot.com
http://blogs.msdn.com/David.Wang
//
On Feb 25, 11:28 pm, Peke <p...@xxxxxxxxxxxxx> wrote:
Hello WenJun,
Thx for all the information.
Kind regards,
Peter
""WenJun Zhang[msft]"" wrote:
Hi Peter,
Definitely this has been out of the scope of IIS newsgroup.. Probably it
has something to do with the WM_QUERYENDSESSION and WM_ENDSESSION Windows
messages. You may take a look at:
Logging Off
http://msdn2.microsoft.com/en-us/library/aa376876(VS.85).aspx
Have a nice week.
Sincerely,
WenJun Zhang
Microsoft Online Community Support
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