Re: Can't disable "Trusted" for Certificates Issued by MS Certificate Server

From: Ohaya (ohaya_at_NO_SPAM.cox.net)
Date: 10/30/03 

Date: Thu, 30 Oct 2003 17:35:23 -0500

Sergio,

Thanks for the followup. Believe me, I am MORE than happy to provide
whatever information that I can on this. I'll try to respond to all of
your questions (interspersed below), and hope that I don't miss
anything...

"Sergio Dutra [MS]" wrote:
>
> Could you specify how you generated the Root CA and SSL server certificates
> (enough details so I can reproduce it)?

The certificate for the root CA (the one that is being used by the MS
Certificate Server) was created when I installed MS Certificate Server.

When I installed the system (Win2K Advanced Server), I think that the
steps that I went through were:

1) Install Windows 2K Advanced Server SP3 (MS Cert Server not selected
during installation) and IIS from CD.

2) Using the popup program that starts up automatically after Windows
installation, configured machine as the first DC (i.e., installed AD).
Did not install DNS Server as part of this.

3) Installed MS Certificate Server.

At this point, the root CA certificate now existed in the system.

I then used Windows Update to bring IE to 6.0 and Windows to SP4.

I then imaged my hard drive. I did this so that I could restore the
system back to this point for subsequent system, i.e., so I could use
this configuration as my test baseline.

I then used IIS Server Certificate wizard to create a cert request for
the server.

The next day, when I got the server cert back from the 3rd-party CA, I
imported the root CA cert and the sub-CA cert from my 3rd-party
CA/sub-CA into the Local Machine Trusted and Intermediate stores,
respectively.

I then used IIS Server Certificate wizard to process the server
certificate that I had received from my 3rd-party CA.

Note that at this point, I had:

- the root CA cert for MS Certificate Server installed on the machine
- the certs for the root CA and sub-CA for my 3rd-party CA installed
- the server cert issued by my 3rd-party CA imported into Windows, and
installed in IIS

I did not have a server cert issued by my MS Certificate Server (I had
not issued any yet). As I alluded to in my previous post, I kind of am
guessing that this is the "root' of this "bug" (sorry for the pun :)!).

[Please DON'T FLAME me for the following! This is all just GUESSING on
my part, trying to imagine what kind of mistake I might have made if I
was coding this stuff myself that would result in the behavior that I am
actually witnessing.]:

I think what's going on is a kind of "boundary" problem, i.e., something
like this: The code in either IIS or CryptoAPI (I can't determine
which) *assume* that there is more than one certificate created by
Certificate Server already in the system. So, during the SSL handshake,
when it (either IIS or CryptoAPI) starts enumerating through these certs
to build the SSL CertificateRequest message, it starts checking from the
2nd cert, rather than the 1st (the MS Certificate Server CA cert), and
as a result, it skips checking the "Client Authentication" purpose in
the first (the MS Certificate Server root cert) cert.

> The list you specify for the root CA, is that from the Details pane or the
> General pane of the certificate UI?

The list was from the Details tab, displayed in the lower pane of the
certificate UI when I clicked on Enhanced Key Usage in the upper pane.

> Also, are you attempting to perform client authentication from the same
> machine as the root CA?

I think that you're asking if the client machine that I'm testing with
is the same as the machine that is running the MS Certificate Server?

If that is an accurate interpretation of your question, then the answer
is "no".

As I explained in detail in the 1st post in this thread I am using two
machines in these tests:

Server: Win2K Advanced Server SP4, updated on Friday (10/24/03)
        Server is the DC (i.e., ActiveDirectory is installed)
        MS Certificate Server is installed
        IIS5

Client: Win2K Pro SP4, updated same date as server
        IE 6.0.2800.1106

If so, the root CA may have a copy in another store
> (usually, "MY" store), and that copy may not have a property restricting the
> usages, so that IE would pick the SSL certificate issued by that root.

Again, that (client machine = server machine) is not the configuration
that I have. The client machine (running Win2K Pro) is a physically
separate machine from the server (running Win2K Advanced Server).

>
> --
> This posting is provided "AS IS" with no warranties, and confers no rights.
> Use of included script samples are subject to the terms specified at
> http://www.microsoft.com/info/cpyright.htm

> "Ohaya" <ohaya@NO_SPAM.cox.net> wrote in message
> news:3FA142DC.4DFC1230@NO_SPAM.cox.net...
> > Sergio,
> >
> > Sorry, I messed up typing out the list of Extended Key Usage (the cert
> > is on a different machine than I use to post, so I had to manually key
> > everything into the post). The list should have been:
> >
> > File Recover
> > Digital Rights
> > Smart Card Logon
> > License Server Verification
> > Key Pack Licenses
> > Embedded Windows System...
> > OEM Windows...
> > Windows System Component Verification
> > Windows Hardware Driver Verification
> > Encrypting File System
> > IP Security User
> > IP Security tunnel termination
> > IP Security end system
> > Microsoft Time Stamping
> > Microsoft Trust List Signing
> > Time Stamping
> > Secure email
> > Code Signing
> > Client Authentication
> > Server Authentication
> >
> >
> > And, yes, I can confirm that that list was from the root certificate
> > used for MS Certificate Server.
> >
> > So, I think that, based on what you described below, I should be able to
> > control whether this CA gets sent out by IIS in the SSL
> > CertificateRequest message by enabling/disabling the "Client
> > Authentication" purpose in the root CA cert, but as I indicated, this
> > does not seem to be working.
> >
> > IIS is including this CA name in the CertificateRequest regardless of
> > the setting of the "Client Authentication" purpose in the Certificate
> > Server/root CA certificate, and as I've indicated in a previous post,
> > I've confirmed this using OpenSSL's s_client.
> >
> > One thing that I noticed when testing with OpenSSL s_client is that if
> > the "Client Authentication" purpose is disabled, the MS Certificate
> > Server CA name is always the first in the list of CAs that IIS sends in
> > the CertificateRequest message.
> >
> > I'm thinking that this "bug" is related to some kind of indexing problem
> > in either IIS or maybe in CryptoAPI when it enumerates the CAs from the
> > Trusted Root store. In other words, maybe since my MS Certificate
> > Server's root CA cert is #0, there's a bug in either IIS or CryptoAPI
> > where it's skipping the checking of the "Client Authentication" purpose.
> >
> > As I've also posted, I've sent an email to MS, and posted on the website
> > as a possible bug, but I haven't heard anything back (I didn't expect
> > that anyway :)), so I hope that since you're with MS, you might bring
> > this up to the appropriate people.
> >
> > If someone was malicious, and depending on how you look at it, this
> > could be regarded as a semi-serious security vulnerability, akin to a
> > "hijacking a CA" exploit.
> >
> >
> >
> >
> >
> > "Sergio Dutra [MS]" wrote:
> > >
> > > The way certificate properties work is by restricting the usages allowed
> by
> > > the certificate. Hence, for a certificate that has no EKU extension
> (meaning
> > > it's good for anything) or for a certificate that has multiple usages
> > > (including Client Auth) specified in the EKU extension, enabling the
> Client
> > > Auth property restricts the certificate to being good only for client
> > > authentication.
> > >
> > > If the certificate does have the EKU extension but it does not have the
> > > Client Auth usage, enabling the Client Auth property makes the
> certificate
> > > valid for nothing, since the intersection of the EKU extension usages
> and
> > > the property usages is nil.
> > >
> > > Typically, the EKU property is set on the root certificate and not on
> end
> > > certificates. I assume that the MS Certificate Server cert you listed
> the
> > > usages for is the root certificate, and not the end certificate issued
> by it
> > > that is actually used by SSL.
> > >
> > > In your case, the MS Certificate Server CA cert does seem to have the
> EKU
> > > extension and it has several usages in it, but I do not see the Client
> Auth
> > > usage in the list below. If this is the case, then you should not be
> able to
> > > enable the Client Auth property since the certificate does not contain
> that
> > > usage already.
> > > --
> > > This posting is provided "AS IS" with no warranties, and confers no
> rights.
> > > Use of included script samples are subject to the terms specified at
> > > http://www.microsoft.com/info/cpyright.htm
> > > "Ohaya" <ohaya@cox.net> wrote in message
> news:3F9EAE9A.4C769D45@cox.net...
> > > > Sergio,
> > > >
> > > > There are no intermediate CAs or intermediate CA certs for the MS
> > > > Certificate Server CA chain. MS Certificate Server was installed with
> > > > all the normal defaults.
> > > >
> > > > When I look at the MS Certificate Server CA cert under
> Details->Enhanced
> > > > Key Usage extension, it lists:
> > > >
> > > > File Recover
> > > > Digital Rights
> > > > Smart Card Logon
> > > > License Server Verification
> > > > Key Pack Licenses
> > > > Embedded Windows System...
> > > > OEM Windows...
> > > > Windows System Component Verification
> > > > Windows Hardware Driver Verification
> > > > Encrypting File System
> > > > IP Security User
> > > > IP Security tunnel termination
> > > > IP Security end system
> > > > Microsoft Time Stamping
> > > > Microsoft Trust List Signing
> > > > Time Stamping
> > > > Secure email
> > > > Code Signing
> > > > Server Authentication
> > > >
> > > > Under Edit Properties:
> > > >
> > > > No matter whether I choose "Enable All", "Disable All", or "Enable
> Only"
> > > > and uncheck all boxes, IIS sends out the MS Cert Server in the
> > > > acceptable CA list.
> > > >
> > > > Some of my subsequent posts showed up in the NGs, some didn't, but
> FYI,
> > > > I have used OpenSSL to confirm the above, and I have an image of a
> clean
> > > > Win2K/IIS/Cert Server install, and this problem is repeatable.
> > > >
> > > >
> > > >
> > > > "Sergio Dutra [MS]" wrote:
> > > > >
> > > > > What usages does the root certificate of your MS Certificate Server
> have
> > > > > (from the Enhanced Key Usage extension)? Are there any intermediate
> > > certs
> > > > > and, if so, what are their usages?
> > > > >
> > > > > --
> > > > > This posting is provided "AS IS" with no warranties, and confers no
> > > rights.
> > > > > Use of included script samples are subject to the terms specified at
> > > > > http://www.microsoft.com/info/cpyright.htm
> > > > > "Ohaya" <ohaya@NO_SPAM.cox.net> wrote in message
> > > > > news:3F9D3A7F.7294A454@NO_SPAM.cox.net...
> > > > > > Hi,
> > > > > >
> > > > > > I think that I have encountered a somewhat serious "bug"
> somewhere. I
> > > > > > can't tell if it's a CryptoAPI bug, an IIS bug, or whatever, so
> I'm
> > > > > > cross-posting this to several newsgroups. This seems like (to me)
> a
> > > > > > rather serious problem, and I'll try to describe what's happening
> as
> > > > > > best I can, and also provide a somewhat kludgy workaround.
> > > > > >
> > > > > >
> > > > > > Background:
> > > > > > ===========
> > > > > > Server: Win2K Advanced Server SP4, updated on Friday (10/24/03)
> > > > > > Server is the DC (i.e., ActiveDirectory is installed)
> > > > > > MS Certificate Server is installed
> > > > > > IIS5
> > > > > >
> > > > > > Client: Win2K Pro SP4, updated same date as server
> > > > > > IE 6.0.2800.1106
> > > > > >
> > > > > >
> > > > > > I have been preparing to configure the above server for SSL with
> > > server
> > > > > > and client authentication for awhile.
> > > > > >
> > > > > > Before I did that, in order to do some pre-testing, I issued a
> server
> > > > > > cert for IIS with MS Certificate Server, and several client certs.
> > > > > >
> > > > > > I got all of this (SSL with client and server authentication)
> working,
> > > > > > including IE would display the client certs that were issued by MS
> > > > > > Certificate Server whenever I tried to connect from IE to IIS.
> > > > > >
> > > > > >
> > > > > > Then, using the IIS server certificate wizard, I deleted the
> original
> > > MS
> > > > > > Certificate Server-issued server cert, then created a new server
> > > > > > certificate request, which I then sent to my commerical CA one
> night.
> > > > > > The next morning, I received the new server cert from my
> commercial
> > > CA,
> > > > > > along with a set of test client certificates.
> > > > > >
> > > > > > I then installed the root cert from my commercial CA on the
> server,
> > > and
> > > > > > then using IIS, used the IIS server certificate wizard to install
> the
> > > > > > new server cert that I had just received from my commercial CA.
> > > > > >
> > > > > > I also installed one of the test client certificates from my
> > > commercial
> > > > > > CA, and installed it on my client machine, and began testing.
> > > > > >
> > > > > >
> > > > > > Problem:
> > > > > > ========
> > > > > > From some previous testing with an earlier similar (SSL client and
> > > > > > server authentication) setup, I found that I could control which
> > > client
> > > > > > certificates that IE would display, when connecting to the server,
> by
> > > > > > enabling or disabling the "Client Authentication" Purpose in the
> root
> > > CA
> > > > > > certificate Purposes for specific root CAs.
> > > > > >
> > > > > > In other words, if I disabled/unchecked the "Client
> Authentication"
> > > > > > purpose for the root CA cert for "Whatever CA", then client
> > > certificates
> > > > > > issued by "Whatever CA" would display in the IE popup when I tried
> to
> > > > > > connect to the server. If I enabled/checked the "Client
> > > Authentication"
> > > > > > purpose for the root CA cert for "Whatever CA", then client
> > > certificates
> > > > > > issued by "Whatever CA" would NOT display in the IE popup when I
> tried
> > > > > > to connect to the server.
> > > > > >
> > > > > >
> > > > > > However, it appears that with the setup that I ended up with above
> > > > > > (install MS Cert Server server cert, uninstall server cert,
> install
> > > new
> > > > > > commercial CA server cert), which I described above under
> > > "Background",
> > > > > > this (enabling/disabling "Client Authentication" purpose for the
> root
> > > CA
> > > > > > cert) does not appear to work for the client certs created with MS
> > > > > > Certificate Server.
> > > > > >
> > > > > > Specifically, the client certificates that I created using MS
> > > > > > Certificate Server still get displayed by IE when connecting to
> the
> > > > > > server, regardless of how the "Client Authentication" purpose is
> set
> > > in
> > > > > > the root CA certificate on the server-side, and there does not
> appear
> > > to
> > > > > > be any reasonable way to prevent these client certificates from
> being
> > > > > > displayed by IE during a connection attempt.
> > > > > >
> > > > > >
> > > > > > I'm guessing (I would HOPE) that deleting the root certificate for
> my
> > > MS
> > > > > > Certifate Server on the SERVER might work, but then that would
> kill my
> > > > > > MS Certificate Server installation, so that doesn't seem like a
> > > > > > reasonable solution, and really, I'm kind of puzzled about why the
> > > > > > "Client Authentication" purpose is "obeyed" for all client
> > > certificates
> > > > > > except for the ones created by MS Certificate Server.
> > > > > >
> > > > > >
> > > > > > Bottom line: It appears that if you install MS Certificate
> Server,
> > > > > > issue a server cert and some client certs, then install a server
> cert
> > > > > > from another CA, that there is no way way get IE browsers that had
> > > > > > client certs from MS Certificate Server not to display those
> > > previously
> > > > > > issued client certs.
> > > > > >
> > > > > >
> > > > > >
> > > > > > Possible workaround:
> > > > > > ====================
> > > > > > I haven't found a way, from the server-end, to cause IE not to
> display
> > > > > > those MS Certificate Server-issued client certs, but thankfully,
> with
> > > > > > IIS at least, the CTL functionality still works properly.
> > > > > >
> > > > > > In other words, if I set up a CTL with only the root cert from my
> > > > > > commercial CA, IE will STILL DISPLAY both the client certs from my
> > > > > > commercial CA and the client certs that were issued by MS
> Certificate
> > > > > > Server, but at least the authentication/connection will fail if
> > > someone
> > > > > > tries to connect using one of the client certs issued by MS
> > > Certificate
> > > > > > Server.

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