React Native

Extract SignatureValue from Signed XML

See more XML Digital Signatures Examples

Demonstrates how to extract the signature value from signed XML. React Native

import { StringBuilder, Xml } from '@chilkat/react-native'

function chilkatExample() {
  // This example will work with the following signed XML, which as been reformatted for readability.

  // <?xml version="1.0" encoding="utf-8"?>
  // <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  //     <SOAP-ENV:Header>
  //         <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" SOAP-ENV:mustUnderstand="1">
  //             <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#">
  //                         <InclusiveNamespaces xmlns="http://www.w3.org/2001/10/xml-exc-c14n#" PrefixList="wsse SOAP-ENV"/>
  //                     </ds:CanonicalizationMethod>
  //                     <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
  //                     <ds:Reference URI="#Body">
  //                         <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>OwgHPZNfDkXnZsjpfzXqAcT3RV3HzmTsEy2bP44FJ0M=</ds:DigestValue>
  //                     </ds:Reference>
  //                 </ds:SignedInfo>
  //                 <ds:SignatureValue>C+7FWngU....DJFBcdg==</ds:SignatureValue>
  //                 <ds:KeyInfo>
  //                     <ds:KeyValue>
  //                         <ds:RSAKeyValue>
  //                             <ds:Modulus>sXeRhM55P13.....NAcibRw==</ds:Modulus>
  //                             <ds:Exponent>AQAB</ds:Exponent>
  //                         </ds:RSAKeyValue>
  //                     </ds:KeyValue>
  //                 </ds:KeyInfo>
  //             </ds:Signature>
  //         </wsse:Security>
  //     </SOAP-ENV:Header>
  //     <SOAP-ENV:Body xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12" SOAP-SEC:id="Body">
  //         <z:FooBar xmlns:z="http://example.com"/>
  //     </SOAP-ENV:Body>
  // </SOAP-ENV:Envelope>

  // -----------------------------------------------------------------------------------------
  // There are a number of ways we can get the contents of the  <ds:SignatureValue>...</ds:SignatureValue>

  const filePath = 'qa_data/xml_dsig_testing/sample_to_show_how_to_extract_sig.xml';

  // If you know there will only be a single SignatureValue in the XML, you don't need to parse XML.
  // Just do quick and simple string search..
  // For example:
  const sb = new StringBuilder();
  try {
    sb.loadFile(filePath, 'utf-8');
  } catch {
    console.log('Failed to load file.');
    return;
  }

  let base64Sig = sb.getBetween('SignatureValue>', '</');
  console.log(`base64Sig = ${base64Sig}`);

  // -----------------------------------------------------------------------------------------
  // If the XML might contain multiple signatures, but the signatures will always be located in the 
  // same place, then you can (beforehand) copy a sample signed XML into Chilkat's online tool
  // at Generate Parsing Code from XML
  // to get the path to the SignatureValue.  For example, the line of code generated for the SignatureValue
  // for the above XML is:
  // string ds_SignatureValue = xml.GetChildContent("SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue");

  // So you can simply use that path..
  const xml = new Xml();
  xml.loadXmlFile(filePath);
  // Assume success..

  base64Sig = xml.getChildContent('SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue');
  console.log(`base64Sig = ${base64Sig}`);

  // -----------------------------------------------------------------------------------------
  // Or perhaps you don't know where the signature is located in the XML.
  // You can search for the tag..
  try {
    const xSigVal = xml.searchForTag('*:SignatureValue', xml);
    console.log(`base64Sig = ${xSigVal.content}`);
  } catch {
    console.log('No SignatureValue found.');
  }
}