C/C++ Source: KeyFromHMACSecret.cpp

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

#define HMACSECRET "c2VjcmV0"
#define HMACLENGTH  -1
#define DSIGNS "xmlns:ds='http://www.w3.org/2000/09/xmldsig#'"
#define SIG_IN "signature-template-enveloping-hmac-sha1.xml"
#define SIG_OUT "signature-enveloping-hmac-sha1.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);

   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(char *secret, long length)
{
   IXMLDSigKeyPtr pKey, pKeyOut;

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

   pKey = xmldsig->createKeyFromHMACSecret(_bstr_t(secret), length);
   if (pKey== NULL) {
      printf("Invalid key from HMACsecret\n");
      return VARIANT_FALSE;
   }

   // KEYVALUE is defined in XMLDSIG_WRITEKEYINFO enum.
   pKeyOut = xmldsig->sign(pKey, KEYVALUE); 
   if (pKeyOut== NULL) {
      printf("Invalid signature.\n");
      return VARIANT_FALSE;
   }

   xmldoc->save(SIG_OUT);
   printf("The data referenced in the signature template was signed ");
   printf("successfully.\nResultant signature:\n\n%s\n",(LPCSTR)xmldoc->xml);
   return VARIANT_TRUE;
}

VARIANT_BOOL VerifyXML(char* secret, long length)
{
   IXMLDSigKeyPtr pKey, pKeyOut;

   pKey = xmldsig->createKeyFromHMACSecret(_bstr_t(secret), length);
   if (pKey== NULL) {
      printf("Invalid key from HMACSecret\n");
      return VARIANT_FALSE;
   }

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

   printf("The data referenced in the signature object was verified successfully.\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;
   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(SIG_IN)) {
      if (VARIANT_TRUE != SignXML(HMACSECRET, HMACLENGTH)) {
         printf("exit with failure.\n");
         goto clean;
      }
   }

   if(VARIANT_TRUE == LoadXML(SIG_OUT)) {
      if (VARIANT_TRUE != VerifyXML(HMACSECRET, HMACLENGTH)) {
         printf("exit with failure.\n");
         goto clean;
      }
   }

clean:
   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 " KeyFromHMACSecretProj" 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 KeyFromHMACSecretProj 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-enveloping-hmac-sha1.xml" in the File name text box.
7. Click OK.
8. Copy the XML signature template file from Resource File, and paste it into the text file you just created.
9. Repeat steps 5-8 for the C++ file above (KeyFromHMACSecret.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 KeyFromHMACSecretProj.exe from the Build menu.
13. Execute the sample application by selecting !Execute KeyFromHMACSecretProj.exe from the Build menu.
14. Verify that your output is similar to that listed in the Output topic.