(Android™) Create/Verify XML Signature with External Text Reference

See more XML Digital Signatures Examples

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

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// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

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

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

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

    CkCert cert = new CkCert();

    boolean success = cert.LoadPfxFile("qa_data/pfx/test_secret.pfx","secret");
    if (success == false) {
        Log.i(TAG, 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 text data to be referenced.
    CkHttp http = new CkHttp();
    CkStringBuilder sbExternalTxt = new CkStringBuilder();
    success = http.QuickGetSb("https://www.chilkatsoft.com/helloWorld.txt",sbExternalTxt);
    if (success == false) {
        Log.i(TAG, http.lastErrorText());
        return;
        }

    success = gen.AddExternalTextRef("https://www.chilkatsoft.com/helloWorld.txt",sbExternalTxt,"utf-8",false,"sha256","");
    if (success == false) {
        Log.i(TAG, 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) {
        Log.i(TAG, 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) {
        Log.i(TAG, gen.lastErrorText());
        return;
        }

    // Examine the XML with the digital signature inserted
    Log.i(TAG, sbXml.getAsString());

    // Here is the output:

    // <?xml version="1.0" encoding="utf-8"?>
    // <abc>
    //     <xyz>
    //         <name>helloWorld.txt</name>
    //         <url>https://www.chilkatsoft.com/helloWorld.txt</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/helloWorld.txt">
    //       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
    //       <ds:DigestValue>f4OxZX/x/FO5LcGBSKHWXfwtSx+j1ncoSt3SABJtkGk=</ds:DigestValue>
    //     </ds:Reference>
    //   </ds:SignedInfo>
    //   <ds:SignatureValue>syFSl...pZDiFQ==</ds:SignatureValue>
    //   <ds:KeyInfo>
    //     <ds:X509Data>
    //       <ds:X509Certificate>MIIHAz...GwnUZWCaDE=</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) {
        Log.i(TAG, 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) {
                Log.i(TAG, http.lastErrorText());
                return;
                }

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

    Log.i(TAG, "Signature verified!");

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}