C/C++ Source: createSAXProxy.cpp

#include <stdio.h>
#import <msxml5.dll>
using namespace MSXML2;

#define DSIGNS "xmlns:ds='http://www.w3.org/2000/09/xmldsig#'"
// Change this key container name to your own if necessary.
#define RSA_KEY "MyRSAFullKeys"
#define INFILE "signature_template.rsa.xml"

IXMLDOMDocument3Ptr xmldoc = NULL;
IXMLDigitalSignaturePtr xmldsig = NULL;

VARIANT_BOOL objectsAreInitialized = VARIANT_FALSE;

VARIANT_BOOL LoadXML(_bstr_t sigFile)
{
   if (!objectsAreInitialized) {
      printf("Must initialize objects before loading signature.\n");
      return VARIANT_FALSE;
   }

   if (xmldoc->load(sigFile) == VARIANT_FALSE) {
      printf("Can't load %s\n", (LPCSTR)sigFile);
      return VARIANT_FALSE;
   }

   xmldoc->setProperty("SelectionNamespaces", DSIGNS);

   // Set the signature property to a <ds:Signature> DOM node.
   xmldsig->signature = xmldoc->selectSingleNode(".//ds:Signature");

   if (xmldsig->signature == NULL) {
      printf("Failed to set the signature property.\n");
      return VARIANT_FALSE;
   }

   return VARIANT_TRUE;
}

VARIANT_BOOL SignXML(unsigned short * refID, unsigned short* newSrc)
{
   HRESULT hr;
   ISAXXMLReaderPtr saxReader=NULL;
   if (xmldsig->signature == NULL) {
      printf("Invalid signature template\n");
      return VARIANT_FALSE;
   }

   if (refID==NULL || refID == L"") {
      printf("Invalid reference ID\n");
      return VARIANT_FALSE;
   }

   if (newSrc!=NULL && newSrc != L"") {
      hr = saxReader.CreateInstance(__uuidof(SAXXMLReader50));
      if (FAILED(hr)) {
         printf("Invalid SAXReader object\n");
         return VARIANT_FALSE;
      }
      IUnknownPtr saxProxy = xmldsig->createSAXProxy();
      if (saxProxy == NULL) {
         printf("Failed to create SAX proxy\n");
         return VARIANT_FALSE;
      }
      ISAXContentHandlerPtr ch = NULL;
      hr = saxProxy.QueryInterface(__uuidof(ISAXContentHandler),(ISAXContentHandler**)&ch);
      if (FAILED(hr)) {
         printf("Can't QI ISAXContentHandler\n");
         return VARIANT_FALSE;
      }

      hr = saxReader->putContentHandler(ch);
      if (FAILED(hr)) {
         printf("Can't set saxProxy\n");
         return VARIANT_FALSE;
      }

      hr = xmldsig->setReferenceData(refID, saxProxy);
      if (FAILED(hr)) {
         printf("Can't set reference data\n");
         return VARIANT_FALSE;
      }

      hr = saxReader->parseURL(newSrc);
      if (FAILED(hr)) {
         printf("Failed to parseURL\n");
         return VARIANT_FALSE;
      }

   }  // At this point, saxReader and ch will be out of scope.

   IXMLDSigKeyPtr pKey = xmldsig->createKeyFromCSP(
            PROV_RSA_FULL, "", RSA_KEY, 0);
   if (pKey==NULL) {
      printf("Invalid key\n");
      return VARIANT_FALSE;
   }

   IXMLDSigKeyPtr pKeyOut = xmldsig->sign(pKey, PURGE);
   if (NULL == pKeyOut) {
      printf("sign failed.\n");
      return VARIANT_FALSE;
   }
      
   printf("Signing was successful.\n");
   printf("Resultant signature:\n\n");
   printf((LPCSTR)xmldoc->xml);
   printf("\n");

   return VARIANT_TRUE;
}


VARIANT_BOOL initObjects()
{
   if (FAILED(xmldsig.CreateInstance(__uuidof(MXDigitalSignature50)) )) {
      printf("Installation of msxml5 is required to run this app.\n");
      return VARIANT_FALSE;
   }

   if (FAILED(xmldoc.CreateInstance(__uuidof(DOMDocument50)) )) {
      printf("Installation of msxml5 is required to run this app.\n");
      return VARIANT_FALSE;
   }
   xmldoc->async = VARIANT_FALSE;
   xmldoc->validateOnParse = VARIANT_FALSE;
   xmldoc->preserveWhiteSpace = VARIANT_TRUE;
   xmldoc->resolveExternals = VARIANT_FALSE;
   objectsAreInitialized = VARIANT_TRUE;

   return VARIANT_TRUE;
}

void cleanObjects()
{
   if (xmldoc) xmldoc.Release();
   if (xmldsig) xmldsig.Release();
}

void main() 
{

   if ( CoInitialize(NULL) == E_FAIL) {
      printf("can't initialize COM Lib\n");
      exit(-1);
   }

   if (!initObjects()) {
      cleanObjects();
      exit(-1);
   }


   if (VARIANT_TRUE == LoadXML(INFILE)) {
      printf("Signing data referenced in signature...\n");
      SignXML(L"#objData", L"");
   }

   if(VARIANT_TRUE == LoadXML(INFILE)) {
      printf("Signing test.xml fed through SAX proxy...\n");
      SignXML(L"#objData", L"test.xml");
   }

   cleanObjects();
   CoUninitialize();
}

Try It!

1. Ensure that you have completed all the procedures in Getting Started with XML Digital Signatures.
2. Start Visual C++.
3. From the File menu, select New. On the Projects tab of the New dialog box that appears, select Win32 Console Application in the left pane. Then type "createSAXProxyProj" in the Project name field. For the project Location field, either accept the default setting or choose another location. Click OK.
4. The Win32 Console Application property page will appear. For the type of Console Application, select An empty project and click Finish. When the New Project Information box displays, click OK.
5. Select FileView on the project browser, and highlight createSAXProxyProj files. From the File menu, select New.
6. On the Files tab of the New dialog box, highlight C++ Source File. Then type "signature_template.rsa.xml" in the File name text box.
7. Click OK.
8. Copy the XML signature template resource file, and paste it into the text file you just created.
9. Repeat steps 5-8 for the XML data file, test.xml.

   Note   You can also copy the file into the project's main directory using Windows Explorer (or a command prompt).

10. Repeat steps 5-8 for the C++ file above (createSAXProxy.cpp).
11. From the Project menu, click Settings..., then click the Link tab.
12. In Object/library modules, type "crypt32.lib". Insert this text either before or after the existing string that lists all objects and modules for the current project. Then click OK.
13. Build the sample by selecting Build createSAXProxyProj.exe from the Build menu.
14. Execute the sample application by selecting !Execute createSAXProxyProj.exe from the Build menu.
15. Verify that your output is similar to that listed in the Output topic.