Impersonation/Delegation security considerations

[Rich]

I'm having trouble finding specific documentation
regarding the negative impact of using delegation in a
Windows 2000 environment. I've read through numerous
articles on using it, but if I do find anything that
cautions the use of it, it reads like the following:

Importantelegation is a very powerful feature and is
unconstrained on Windows 2000. It should be used with
caution. Computers that are configured to support
delegation should be under controlled access to prevent
misuse of this feature.

Our Network/Server side of the house does not want to
implement delegation without knowing the immediate and
potential security risks, and how to guard against them.

 

[Alek Davis]

Hi Rich,

Our AD/network guys illustrated a potential security issue using the
following example. By the way, I assume that by delegation you mean passing
user's credential from one machine to the other, which would allow a Web
application running on machine A to connect to a SQL server running on
machine B using integrated Windows authentication with credentials
(actually, authentication token or Kerberos ticket) of a remote user
accessing the site from machine C. Without delegation, a Web application can
only pass user's credentials to a SQL Server running on the same machine.
So, let's say that I am an internal hacker and I would like to connect to
some secure database using credentials of the company's CEO (CIO, or
whatever). If delegation is enabled on my network, what I can do is:

(1) Create a fake internal Web site.
(2) Send an HTML e-mail (or regular e-mail with a link) pointing to my fake
Web site to the CEO (CIO, or whatever).
(3) In the code-behind logic, use caller's credentials (Kerberos ticket) to
connect to the database and do whatever I want on behalf of the user.

The main danger in this scenario is that the user will never know what have
happened. Without delegation, this risk is eliminated because my fake Web
site would not be able to propagate user's credentials to the remote SQL
Server unless I use basic authentication for the Web site, which is also a
risk, but at least it will be visible to the user that some security-related
operation is happening.

Alek

 

[Rich]

Hi Alek,

Your assumption and illustration of machines A, B, and C
was 100% correct. Thank you very much for the internal
security risk example. I will forward this info on to our
network folks.