Extending the issuer sample

The issuer may be extended in different ways. This site is going to document some examples on the use of various interfaces.

Adding a new certificate specification and handler:

A certificate specification is required to be available online for download by any client or verifier, as well as a handler for providing issuer values.

Certificate specifications are handled at runtime using I_IssuerConfig, which holds a list of specifications and access methods to retrieve the handlers attached to it. It is either possible to use the existing sample implementation for extension or to implement a custom I_IssuerConfig. In the following section only the first term should be covered

Use of certificate specifications in the example servlet

The example servlets web.xml defines certificate specifications with the pattern:

<init-param>
  <param-name>SPECn</param-name>
  <param-value><http-uri-where-public-available>|<file-uri-where-located-as-file></param-value>
</init-param>

Currently two certificate specifications are registered (SPEC1/SPEC2), so to add a new one you may simply add:

<init-param>
  <param-name>SPEC3</param-name>
  <param-value>http://localhost:8080/idenpa-issuer/files/CREDDEF3_LOCATION|file://${file.separator}${catalina.home}${file.separator}conf${file.separator}idemix${file.separator}credstruct3noeid.xml</param-value>
</init-param>

At the next deployment the spec will be loaded from from TOMCAT_ROOT/conf/idemix/credstruct3noeid.xml and will be used with the default specification handler, filling any issuer-related certificate fields with random values. If you want to use the specification with the default handler for eID-enabled specifications, the specification location must not contain the string "noeid".

However, in both cases a custom specification handler might be necessary. To exchange the default behaviour simply change the issuer servlets init() method and register a handler for your own spec in the following way:

  @Override
  public void init(ServletConfig config) throws ServletException {
    ...
    super.init(config);
    try {
      m_objCfg = new IssuerServletConfig(config);
      m_objCfg.init();
      ...
      m_objStorage = StorageWrapper.init(m_objCfg);
      m_objSrvHandler = ServiceHandler.init(m_objStorage);
      ...
      specStore.setHandler("http://localhost:8080/idenpa-issuer/files/CREDDEF3_LOCATION", new MyCustomSpecHandler());
    }
    ...
  }

The handler MyCustomSpecHandler() may either implement I_SpecHandler or I_EidSpecHandler depending whether a normal or eID-enabled specification was added. Refer to the JavaDoc for further implementation of those interfaces.

A new HTML element to use the aforementioned SPEC3 might look like this:

<html>
 <body>
  ....
    <form action="issue" method="get">
      <input type="hidden" name="STRUCT" value="http://localhost:8080/idenpa-issuer/files/CREDDEF3_LOCATION"/>
      <input type="submit" name="Submit" value="Issue custom certificate"/>
    </form>
  ....
  </body>
</html>

Integrating a third-party eID-library

To integrate a custom eID-library either the provided I_IssuerConfig implementation may be extended or a new one may be provided and used instead. In the first case, simply extend the exemplary implementation as follows and return your own implementation of I_EidProviderWrapper:

public class CustomServletConfig extends IssuerServletConfig implements I_IssuerConfig {
  
  /**
   * Delegate constructor for use of IssuerServletConfig()
   */
  public CustomServletConfig(ServletConfig cfg)
      throws IssuerServiceInitException {
      super(cfg);
  }
  
  /**
   * Overwrite default implementation
   */
  @Override
  public I_EidProviderWrapper getEidProviderWrapper() {
    return m_objEidWrapper;
  }
}