C-C++ Source: verify.cpp

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[This sample code uses features that were implemented in MSXML 5.0 for Microsoft Office Applications. XML digital signatures are not supported in MXSML 6.0 and later.]

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

#define DSIGNS "xmlns:ds='http://www.w3.org/2000/09/xmldsig#'"
#define INFILE "signature.verify.dsa.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 VerifyXML()
{
   IXMLDOMNodePtr pKeyInfo, pNode;
   IXMLDSigKeyPtr pKey, pKeyOut;

   pKeyInfo = xmldoc->selectSingleNode(".//ds:KeyInfo/ds:KeyValue");
   if (pKeyInfo == NULL) {
      printf("Invalid <ds:KeyInfo>\n");
      return VARIANT_FALSE;
   }

   pKey = xmldsig->createKeyFromNode(pKeyInfo);
   if (pKey== NULL) {
      printf("Invalid key from <ds:KeyInfo>\n");
      return VARIANT_FALSE;
   }

   pKeyOut = xmldsig->verify(pKey);
   if (pKeyOut== NULL) {
      printf("Invalid signature.\n");
      return VARIANT_FALSE;
   }

   printf("Signature verified.\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);
   }

   printf("Verifying signature.\n\n");
   if (VARIANT_TRUE == LoadXML(INFILE)) {
      VerifyXML();
   }

   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 "verifyProj" 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 verifyProj files. From the File menu, select New.

  6. On the Files tab of the New dialog box, highlight C++ Source File. Then type "signature.verify.dsa.xml" in the File name text box.

  7. Copy the XML signature resource file, and paste it into the file you've just created.

  8. Click OK.

    Note

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

  9. Repeat steps 5-8 for the C++ file above (verify.cpp).

  10. From the Project menu, click Settings..., then click the Link tab.

  11. 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.

  12. Build the sample by selecting Build verifyProj.exe from the Build menu.

  13. Execute the sample application by selecting !Execute verifyProj.exe from the Build menu.

  14. Verify that the result is the same as that listed in the Output topic.