Verisign PKI: anyone to subordinate CA

["Pidgorny, Slav" <pidgorns () anz com>]

G'day Bugtraq,

Microsoft Security Bulletin MS01-017
(http://www.microsoft.com/technet/security/bulletin/MS01-017.asp) inspired
me to do some testing. Here are the results:

1. I configured Microsoft Certificate services to act as a standalone
subordinate CA. A request for a CA certificate was generated.
2. I sent this request as a request for a Web server SSL certificate.
3. The Verisign test CA did not complain upon processing this request. It
generated and signed the certificate.
4. I installed the certificate to MS Certificate Services and start the CA
service.
5. From now on, I effectively have a signed CA certification.  Any generated
signatures from this point will have a certification path leading to the
root CA.

I only used Verisign test root CA in my test. The steps above can probably
be repeated using Verisign production root CA, resulting the situation
whereas I'm becoming a subordinate CA to Verisign trusted root without
letting them know.

Thawte test CA also signs the CA certificate submitted as a Web server
certificate, but MS Certificate Server refuses to install the certificate as
the CA certificate. The difference between Verisign and Thawte certificates
is the Basic Constraints field. If I would be using OpenSSL tools instead of
MS Certificate Server, I can probably disable all the checks against the CA
certificate.

Any thoughts? Do you think it's a security problem?

Regards,

S. Pidgorny, MS MVP, MCSE

DISCLAIMER: Opinions expressed by me is not necessarily my employer's, it is
not intended to be formal and accurate. Neither myself nor my employer
assume any responsibility for any consequences.

P.S. Many thanks to Dave Ahmad for the discussion leading to this post.