Dart

Create XML Signature with External Data Reference

See more XML Digital Signatures Examples

Demonstrates how to create an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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>
  //     <jpg>
  //         <name>starfish.jpg</name>
  //         <url>https://www.chilkatsoft.com/images/starfish.jpg</url>
  //     </jpg>
  //   </xyz>
  // </abc>

  // The above XML is available at https://www.chilkatsoft.com/exampleData/addSignatureToThis.xml
  // First fetch the XML:

  final url = 'https://www.chilkatsoft.com/exampleData/addSignatureToThis.xml';
  final http = CkHttp();
  final sbXml = CkStringBuilder();
  try {
    http.quickGetSb(url, sbXml);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // We'll use an RSA private key for signing.  
  final rsaKey = CkPrivateKey();
  try {
    rsaKey.loadPemFile('qa_data/rsa/rsaPrivKey_pkcs8.pem');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final xmlSigGen = CkXmlDSigGen();

  // Indicate were the Signature will be inserted:
  xmlSigGen.sigLocation = 'abc|xyz|jpg';

  // Provide the RSA key to be used for signing:
  xmlSigGen.setPrivateKey(rsaKey);

  // Fetch the JPG image data.
  final jpgUrl = 'https://www.chilkatsoft.com/images/starfish.jpg';
  final jpgData = CkBinData();
  try {
    http.quickGetBd(jpgUrl, jpgData);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Add the external data reference:
  xmlSigGen.addExternalBinaryRef(jpgUrl, jpgData, 'sha256', '');

  // Create the XML digital signature:
  try {
    xmlSigGen.createXmlDSigSb(sbXml);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Examine the XML that now contains the Signature:
  print(sbXml.getAsString());

  // <?xml version="1.0" encoding="UTF-8" standalone="no"?>
  // <abc>
  //   <xyz>
  //     <jpg>
  //         <name>starfish.jpg</name>
  //         <url>https://www.chilkatsoft.com/images/starfish.jpg</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/images/starfish.jpg"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>ApHRr6nilNrzt3dLveC9zlPoSllaCMfHsbAwr+vYBPkHkJ4wD5LzDDhi1tSJZAAeTckmvSqIG3Wi0rgXQiSM644MD3coBFx4QgrY+GZ+XJJE2Y0Ye3VvaQBiRdUW3INGsW4GLubncgQk5JhuAQjo6O/GKpfEuYqUJj/6CLHLQwMPwbZ2043ykgzuPFoOZf6EydJMBAn1ORMvrpUn+zuA9UngOTGap6eWE4CeiNx23BRC2wSztbUjdCLcqXvgiYu/v0tBNaTcwy7b6+IFtwv/lNUUBUQJ/3p+aErzFn3wLeH3yeqpDCU0U6Dqu5SS1jYupcWWsLHJjYnj2066DPJi/g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
  //   </xyz>
  // </abc>
  // 
}