Make IIS require SSL client certificate during initial handshake

client-certificatesiisssl

I am trying to configure an IIS website to require SSL client certificates. The website is set up in both IIS 6 and 7, though I am more interested in making it work for 7. I set the require client certificates property in IIS and it works fine when accessing the site through a web browser, but a Java-based client is having trouble accessing it.

I believe the problem is that IIS does not request a client certificate during the initial SSL handshake. Instead it negotiates a normal SSL connection, checks to see if the resource requires client certificates, and if it does it then initiates a new SSL handshake that requests a client certificate. IIS does this so support sites that only require the client certificates for certain resources. Even when the requirement is specified for the entire website, IIS still initiates two SSL handshakes. I want to force IIS to request the client certificate on the first SSL handshake, which will hopefully get things working for the client. (The client is developed by an external partner and I have virtually no knowledge of how it is set up and no access to its source code)

Has anyone dealt with this problem in IIS before?

Best Answer

Here's how I did this, on IIS 7.5:

  1. Run the following in an admin command prompt: netsh http show sslcert

  2. Save the output in a text file. Will look something like this:

    IP:port                 : 0.0.0.0:443
Certificate Hash        : [a hash value]
Application ID          : {[a GUID]}
Certificate Store Name  : MY
Verify Client Certificate Revocation    : Enabled
Verify Revocation Using Cached Client Certificate Only    : Disabled
Usage Check    : Enabled
Revocation Freshness Time : 0
URL Retrieval Timeout   : 0
Ctl Identifier          : (null)
Ctl Store Name          : (null)
DS Mapper Usage    : Disabled
Negotiate Client Certificate    : Disabled

  3. Create a batch file using that info: 

    netsh http show sslcert
netsh http delete sslcert ipport=0.0.0.0:443
netsh http add sslcert ipport=0.0.0.0:443 certhash=[your cert hash from above] appid={[your GUID from above]} certstorename=MY verifyclientcertrevocation=enable VerifyRevocationWithCachedClientCertOnly=disable UsageCheck=Enable clientcertnegotiation=enable
netsh http show sslcert

    (Yes, you have to delete and re-add; you can't just alter clientcertnegotiation in-place. That's why it's important to save the hash and GUID, so it knows what to re-add.)

  4. Run that batch file, check for any errors, done.

Keep in mind that this setting is applied per-certificate, not per-server. So if you use multiple certs, or change/update your cert, you will have to do this again.

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