Configuring One-to-One Client Certificate Mappings

By Robert Lucero

June 5, 2008

Background

IIS 6 had a User Interface to configure and map one to one certificates for authentication. It allowed users to select the validation client certificate and assign the authorized user credentials. There isn't a similar UI in IIS 7 and above. This walkthrough is designed to instruct users to configure one to one client certificates using Administration Pack's Configuration Editor. Users who do not have this add-on can view the appendix section for AppCmd arguments and C# code examples to perform this walkthrough.

IIS 7 and Above Schema

This is the schema for the IIS Client Certificate Mapping Authentication Feature in IIS 7 and above.

<sectionSchema name="system.webServer/security/authentication/iisClientCertificateMappingAuthentication">
  <attribute name="enabled" type="bool" defaultValue="false" />
  <attribute name="oneToOneCertificateMappingsEnabled" type="bool" defaultValue="true" />
  <element name="oneToOneMappings">
    <collection addElement="add" clearElement="clear">
      <attribute name="enabled" type="bool" defaultValue="true" />
      <attribute name="userName" type="string" />
      <attribute name="password" type="string" encrypted="true" />
      <attribute name="certificate" type="string" required="true" isUniqueKey="true" />
    </collection>
  </element>
</sectionSchema>

Prerequisites

These are the prerequisites needed for this walkthrough. I won't be covering how to create or do these things.

  1. Installed IIS Client Certificate Mapping module
  2. A Web Site with an HTTPS binding, properly configured
  3. A Base-64 certificate (.cer file). [Note: This can be any valid 64-bit certificate, but it must be in file form]
  4. Installed a client certificate on a client
  5. Installation of IIS 7 Administration Pack Technical Preview 2

Step 1: Getting the Certificate Blob

The oneToOneMappings collection item has an attribute called certificate. The required value for this attribute is not the certificate has but the actual certificate blob. Here's how you extract it.

  1. Right click on your .cer file.
  2. Select Open With... in the context menu
  3. Select Notepad from the list of Other Programs and click OK. [Note: Notepad may be hidden beneath a drop down in the Vista/Windows 2008 list view]
  4. This is what should be displayed in notepad:
  5. -----BEGIN CERTIFICATE-----
    MIIEfjCCA2agAwIBAgIKFW1IXAAAAAAAAjANBgkqhkiG9w0BAQUFADAbMRkwFwYD
    VQQDExBJSVNSZW1vdGVNZ3JUZXN0MB4XDTA4MDIxMTIxNTk1NloXDTA5MDIxMTIy
    MDk1NlowaDELMAkGA1UEBhMCVVMxEzARBgNVBAgTCldhc2hpbmd0b24xEDAOBgNV
    BAcTB1JlZG1vbmQxDTALBgNVBAoTBE1TRlQxDDAKBgNVBAsTA0lJUzEVMBMGA1UE
    AxMMUkxVQ0VSTzItSUlTMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC3611j
    34q2qQgHa7ao11TcQMDYlJMrqET05MWFY1/Vso+leujLoIGTfdHOuz4IBVoeUE+y
    mlL8r53s2BQeVFROnDtg4Jko1zJsz7AUAnQNBk/GYA1AHYmhY79Z0p1KXW/wSTJB
    tdUn732GQOqYf4wY8jOD2zUJDUG4HXm6ib8ajwIDAQABo4IB+TCCAfUwDgYDVR0P
    AQH/BAQDAgTwMBMGA1UdJQQMMAoGCCsGAQUFBwMBMHgGCSqGSIb3DQEJDwRrMGkw
    DgYIKoZIhvcNAwICAgCAMA4GCCqGSIb3DQMEAgIAgDALBglghkgBZQMEASowCwYJ
    YIZIAWUDBAEtMAsGCWCGSAFlAwQBAjALBglghkgBZQMEAQUwBwYFKw4DAgcwCgYI
    KoZIhvcNAwcwHQYDVR0OBBYEFHbHA+HwZcIrslklj1W3O23UFrBgMB8GA1UdIwQY
    MBaAFMxzlGbmkp2+phhDg7TPfi83d7UVMHMGA1UdHwRsMGowaKBmoGSGL2h0dHA6
    Ly9paXNzYjMwNS9DZXJ0RW5yb2xsL0lJU1JlbW90ZU1nclRlc3QuY3JshjFmaWxl
    Oi8vXFxpaXNzYjMwNVxDZXJ0RW5yb2xsXElJU1JlbW90ZU1nclRlc3QuY3JsMIGe
    BggrBgEFBQcBAQSBkTCBjjBEBggrBgEFBQcwAoY4aHR0cDovL2lpc3NiMzA1L0Nl
    cnRFbnJvbGwvaWlzc2IzMDVfSUlTUmVtb3RlTWdyVGVzdC5jcnQwRgYIKwYBBQUH
    MAKGOmZpbGU6Ly9cXGlpc3NiMzA1XENlcnRFbnJvbGxcaWlzc2IzMDVfSUlTUmVt
    b3RlTWdyVGVzdC5jcnQwDQYJKoZIhvcNAQEFBQADggEBAEsSkcx0re36IL80UphJ
    w/srR3LBsy8sfwqxBMzMTdF7k6jYtUVpn3D2Dd4JXXVOaEVud9YNn9pr6xJL4t79
    Zh+hJzIPA5pQLbccx4vjWB4cWEYxzcoKYCuUdZrfPFXO1a5kQAj8IZ0/6bhMceyR
    Z7dRDoaIuAGQLFAlC/KjIBCemDi54MlWtvATQ8bmiRuEOWeneK2Vd2e0fxyezk05
    dRqa8DEC74CQN4rQuz395ECm+M/hQnN+dHOygV8n9swd0bdNq8qypwfVUes5HIpj
    LFmKTuGyFSVj7jv+64oTxvxtYX2QFp9q6Bi+qj0uyrX8Xjxy5rPSVPEfnxPCBg58
    RCI=
    -----END CERTIFICATE-----
  6. Remove -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----
  7. Format the certificate blob to be a single line.
  8. Save this file as clientCertBlob.txt

Step 2: Enabling IIS Client Certificates Mapping Authentication and One to One Certificate Mapping For A Web Site

The next steps will cover how to enable the Client Certificate Mapping Authentication feature, One to One Certificate Mapping and added a mapping entry.

  1. Start Inetmgr, the IIS Manager UI
  2. Select the SSL web site that is being configured and open Configuration Editor
  3. Type "system.webServer/security/authentication/iisClientCertificateMappingAuthentication" in the Section drop down box.
  4. Select the enabled field and change the value to true
  5. Select the oneToOneCertificateMappingsEnabled property grid entry and change the value to true
  6. Select the oneToOneMappings property grid entry and click Edit Items... in the Actions Task Pane
  7. Click Add in the Collection Editor task list
  8. Copy the single string certificate blob from above and paste it into the certificate field
  9. Set the userName and password that clients will be authenticated as.
  10. Set the enabled field to true
  11. Close Collection Editor
  12. Click Apply in the Actions Task Pane [Note: Click Script Generation prior to clicking Apply to get scripts for this process]

Once this is complete the server will be configured to handle IIS Client Certificate Mapping authentication with a single one to one certificate mapping entry.

Step 3: Enabling Client Certificate Authentication For A Web Site Using SSL

Once a mapping has been created and the feature has been enabled, a site must be configured to use client certificates.

  1. From within Inetmgr, the IIS Manager UI, select the SSL web site you want to use client certificates
  2. Select the SSL UI module
  3. Under Client certificates: select the Accept radio button
  4. Click Apply in the Actions Task Pane

Now the web site is configured to accept and authenticate clients based on client certificates.

Step 4: Verifying It All Works

The client that is trying to access the SSL web page needs the client certificate properly installed. If a client attempts to request a page without the certificate a 401 will be served. Once the client certificate is correctly installed, the page will be served as normal.

Play around with different combinations of authorization rules to suit your needs.

Summary

You have now configured IIS Client Certificate Mappings and a single One to One Certificate mapping.

Appendix

These are the Code Snippets to perform walkthrough steps 2 and 3. All of this was generated using Configuration Editor's Script Generation.

AppCmd specific instructions

appcmd.exe set config "Default Web Site" -section:system.webServer/security/authentication/iisClientCertificateMappingAuthentication 
/enabled:"True" /oneToOneCertificateMappingsEnabled:"True" /commit:apphost appcmd.exe set config "Default Web Site" -section:system.webServer/security/authentication/iisClientCertificateMappingAuthentication
/+"oneToOneMappings.[userName='testUser',password='securePassWord!1',certificate='CERTIFICATE_BLOB']" /commit:apphost appcmd.exe set config "Default Web Site" -section:system.webServer/security/access /sslFlags:"Ssl, SslNegotiateCert, Ssl128" /commit:apphost

C# Code:

using System;
using System.Text;
using Microsoft.Web.Administration;

internal static class Sample {

    private static void Main() {
        
        using(ServerManager serverManager = new ServerManager()) { 
            Configuration config = serverManager.GetApplicationHostConfiguration();
            
            ConfigurationSection iisClientCertificateMappingAuthenticationSection = 
config.GetSection("system.webServer/security/authentication/iisClientCertificateMappingAuthentication", "Default Web Site"); iisClientCertificateMappingAuthenticationSection["enabled"] = true; iisClientCertificateMappingAuthenticationSection["oneToOneCertificateMappingsEnabled"] = true; ConfigurationElementCollection oneToOneMappingsCollection =
iisClientCertificateMappingAuthenticationSection.GetCollection("oneToOneMappings"); ConfigurationElement addElement = oneToOneMappingsCollection.CreateElement("add"); addElement["userName"] = @"testUser"; addElement["password"] = @"securePassWord!1"; addElement["certificate"] = @"CERTIFICATE_BLOB"; oneToOneMappingsCollection.Add(addElement); serverManager.CommitChanges(); } } } using System; using System.Text; using Microsoft.Web.Administration; internal static class Sample { private static void Main() { using(ServerManager serverManager = new ServerManager()) { Configuration config = serverManager.GetApplicationHostConfiguration(); ConfigurationSection accessSection = config.GetSection("system.webServer/security/access", "Default Web Site"); accessSection["sslFlags"] = @"Ssl, SslNegotiateCert, Ssl128"; serverManager.CommitChanges(); } } }


Discuss in IIS Forums