Client Certificate Mapper Documentation

This change adds the missing documentation for the Client Certificate Mapper.

Author: nebhale

README.md

@@ -73,6 +73,7 @@ To learn how to configure various properties of the buildpack, follow the "Confi
 	* [Tomcat](docs/container-tomcat.md) ([Configuration](docs/container-tomcat.md#configuration))
 * Standard Frameworks
 	* [AppDynamics Agent](docs/framework-app_dynamics_agent.md) ([Configuration](docs/framework-app_dynamics_agent.md#configuration))
+	* [Client Certificate Mapper](docs/framework-client_certificate_mapper.md) ([Configuration](docs/framework-client_certificate_mapper.md#configuration))
 	* [Container Customizer](docs/framework-container_customizer.md) ([Configuration](docs/framework-container_customizer.md#configuration))
 	* [Container Security Provider](docs/framework-container_security_provider.md) ([Configuration](docs/framework-container_security_provider.md#configuration))
 	* [Contrast Security Agent](docs/framework-contrast_security_agent.md) ([Configuration](docs/framework-contrast_security_agent.md#configuration))

docs/framework-client_certificate_mapper.md

@@ -0,0 +1,34 @@
+# Client Certificate Mapper
+The Client Certificate Mapper Framework adds a Servlet Filter to applications that will that maps the `X-Forwarded-Client-Cert` to the `javax.servlet.request.X509Certificate` Servlet attribute.
+
+<table>
+  <tr>
+    <td><strong>Detection Criterion</strong></td>
+    <td>Unconditional</td>
+  </tr>
+  <tr>
+    <td><strong>Tags</strong></td>
+    <td><tt>client-certificate-mapper=&lt;version&gt;</tt></td>
+  </tr>
+</table>
+Tags are printed to standard output by the buildpack detect script
+
+## Configuration
+For general information on configuring the buildpack, including how to specify configuration values through environment variables, refer to [Configuration and Extension][].
+
+The framework can be configured by modifying the [`config/client_certificate_mapper.yml`][] file in the buildpack fork.  The framework uses the [`Repository` utility support][repositories] and so it supports the [version syntax][] defined there.
+
+| Name | Description
+| ---- | -----------
+| `repository_root` | The URL of the Container Customizer repository index ([details][repositories]).
+| `version` | The version of Container Customizer to use. Candidate versions can be found in [this listing][].
+
+## Servlet Filter
+The [Servlet Filter][] added by this framework maps the `X-Forwarded-Client-Cert` to the `javax.servlet.request.X509Certificate` Servlet attribute for each request.  The `X-Forwarded-Client-Cert` header is contributed by the Cloud Foundry Router and contains the any TLS certificate presented by a client for mututal TLS authentication.  This certificate can then be used by any standard Java security framework to establish authentication and authorization for a request.
+
+[`config/client_certificate_mapper.yml`]: ../config/client_certificate_mapper.yml
+[Configuration and Extension]: ../README.md#configuration-and-extension
+[repositories]: extending-repositories.md
+[Servlet Filter]: https://github.com/cloudfoundry/java-buildpack-client-certificate-mapper
+[this listing]: http://download.pivotal.io.s3.amazonaws.com/container-security-provider/index.yml
+[version syntax]: extending-repositories.md#version-syntax-and-ordering