(Java) Create XML Signature with External XML Reference

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is an XML file located at the following URL: https://www.chilkatsoft.com/data/helloWorld.xml

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example inserts an XML signature in the following XML:

    // <?xml version="1.0" encoding="UTF-8" standalone="no"?>
    // <abc>
    //   <xyz>
    // 	<name>helloWorld.xml</name>
    // 	<url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
    //   </xyz>
    // </abc>

    // Build the above XML to be signed.
    CkXml xml = new CkXml();
    xml.put_Tag("abc");
    xml.UpdateChildContent("xyz|name","helloWorld.xml");
    xml.UpdateChildContent("xyz|url","https://www.chilkatsoft.com/data/helloWorld.xml");

    CkCert cert = new CkCert();

    boolean success = cert.LoadPfxFile("qa_data/pfx/test_secret.pfx","secret");
    if (success == false) {
        System.out.println(cert.lastErrorText());
        return;
        }

    CkXmlDSigGen gen = new CkXmlDSigGen();

    // Indicate the location within the XML the Signature will be inserted.
    gen.put_SigLocation("abc|xyz");

    // Get the content of the XML data to be referenced.
    CkHttp http = new CkHttp();
    CkStringBuilder sbExternalXml = new CkStringBuilder();
    success = http.QuickGetSb("https://www.chilkatsoft.com/data/helloWorld.xml",sbExternalXml);
    if (success == false) {
        System.out.println(http.lastErrorText());
        return;
        }

    success = gen.AddExternalXmlRef("https://www.chilkatsoft.com/data/helloWorld.xml",sbExternalXml,"sha256","EXCL_C14N","");
    if (success == false) {
        System.out.println(gen.lastErrorText());
        return;
        }

    // Provide the private key for signing via the certificate, and indicate that
    // we want the base64 of the certificate embedded in the KeyInfo.
    gen.put_KeyInfoType("X509Data");
    gen.put_X509Type("Certificate");

    boolean bUsePrivateKey = true;
    success = gen.SetX509Cert(cert,bUsePrivateKey);
    if (success != true) {
        System.out.println(gen.lastErrorText());
        return;
        }

    // Indicate we want an indented signature for readability.
    // This can be removed after debugging is finished..
    gen.put_Behaviors("IndentedSignature");

    // Now create and insert the Signature
    CkStringBuilder sbXml = new CkStringBuilder();
    xml.GetXmlSb(sbXml);
    success = gen.CreateXmlDSigSb(sbXml);
    if (success != true) {
        System.out.println(gen.lastErrorText());
        return;
        }

    // Examine the XML with the digital signature inserted
    System.out.println(sbXml.getAsString());

    // Here is the output:

    // <?xml version="1.0" encoding="utf-8"?>
    // <abc>
    //     <xyz>
    //         <name>helloWorld.xml</name>
    //         <url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
    //     <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    //   <ds:SignedInfo>
    //     <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
    //     <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
    //     <ds:Reference URI="https://www.chilkatsoft.com/data/helloWorld.xml">
    //       <ds:Transforms>
    //         <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
    //       </ds:Transforms>
    //       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
    //       <ds:DigestValue>H/s775OZhel6wdBhe02l4LK6m0lkplOisKxAbVwWxp0=</ds:DigestValue>
    //     </ds:Reference>
    //   </ds:SignedInfo>
    //   <ds:SignatureValue>UruwnBqh..Ll4IzUA==</ds:SignatureValue>
    //   <ds:KeyInfo>
    //     <ds:X509Data>
    //       <ds:X509Certificate>MIIHAz...nUZWCaDE=</ds:X509Certificate>
    //     </ds:X509Data>
    //   </ds:KeyInfo>
    // </ds:Signature></xyz>
    // </abc>

    // Let's verify the signature...
    CkXmlDSig verifier = new CkXmlDSig();
    success = verifier.LoadSignatureSb(sbXml);
    if (success != true) {
        System.out.println(verifier.lastErrorText());
        return;
        }

    // Let's examine the external references, and fetch the data for each..
    CkStringBuilder sbExternalData = new CkStringBuilder();
    int numRefs = verifier.get_NumReferences();
    int i = 0;
    while (i < numRefs) {
        boolean bExternal = verifier.IsReferenceExternal(i);
        if (bExternal == true) {
            String uri = verifier.referenceUri(i);

            // We're assuming the URI is an https:// or http:// URL...
            // Let's also assume we know that the referenced data is text and we want the utf-8 byte representation.
            sbExternalData.Clear();
            success = http.QuickGetSb(uri,sbExternalData);
            if (success == false) {
                System.out.println(http.lastErrorText());
                return;
                }

            // Because the referenced external data was explicitly XML, it was the canonicalized XML that was digested.
            // We need to canonicalize the XML in the same way as when signed.
            String canonXml = verifier.canonicalizeXml(sbExternalData.getAsString(),"EXCL_C14N",false);
            sbExternalData.SetString(canonXml);

            success = verifier.SetRefDataSb(i,sbExternalData,"utf-8");
            if (success == false) {
                System.out.println(verifier.lastErrorText());
                return;
                }

            }

        i = i+1;
        }

    // Now that we have the external data available, we can verify the reference digest(s) and the signature.
    boolean bVerified = verifier.VerifySignature(true);
    if (bVerified != true) {
        System.out.println(verifier.lastErrorText());
        return;
        }

    System.out.println("Signature verified!");
  }
}