(MFC) Verify an XML Signature with Multiple References

Demonstrates how to verify an XML digital signature that contains multiple references.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkHttp.h>
#include <CkStringBuilder.h>
#include <CkXmlDSig.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // An example of an enveloping XML signature with mulitple references is available at
    // https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml

    // This example will show how to verify the signature and all references, and also how
    // to verify each reference individually.  This is useful to distinguish which part
    // of the XML signature validation failed.  It could be that one or more of the references
    // failed because of a hash computation mismatch.  Or it could be that the signature over
    // the SignedInfo failed.  

    // First, let's grab the sample XML signature.
    CkHttp http;
    CkStringBuilder sbXml;
    bool success = http.QuickGetSb("https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml",sbXml);
    if (success != true) {
        strOut.append(http.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Load the XML containing the signature to be verified.
    CkXmlDSig verifier;
    success = verifier.LoadSignatureSb(sbXml);
    if (success != true) {
        strOut.append(verifier.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    bool verifyReferenceDigests = true;

    // The quick way to validate all references and the signature over the SignedInfo
    // is to call VerifySignature with verifyReferenceDigests equal to true.
    bool verified = verifier.VerifySignature(verifyReferenceDigests);
    strOut.append("Signature and all reference digests verified = ");
    strOut.appendInt(verified);
    strOut.append("\r\n");

    // Let's pretend the call to VerifySignature returned false.  Something did not validate.
    // Was it one or more of the References that did not hash to the correct value?
    // Or was it the signature over the SignedInfo that failed?
    // We can check just the signature over the SignedInfo by passing false to VerifySignature.
    // This allows us to skip the hashing and checking each Reference.  
    verifyReferenceDigests = false;
    bool signedInfoVerified = verifier.VerifySignature(verifyReferenceDigests);
    strOut.append("Neglecting the reference hashes, the SignedInfo validation result = ");
    strOut.appendInt(signedInfoVerified);
    strOut.append("\r\n");

    // We can also verify each reference digest separately
    int numRefs = verifier.get_NumReferences();
    int i = 0;
    while (i < numRefs) {
        bool refDigestVerified = verifier.VerifyReferenceDigest(i);
        strOut.append("Reference ");
        strOut.appendInt(i);
        strOut.append(" digest verified = ");
        strOut.appendInt(refDigestVerified);
        strOut.append("\r\n");
        i = i + 1;
    }

    // For this sample XML signature with 3 References, we get the following output:

    // Signature and all reference digests verified = True
    // Neglecting the reference hashes, the SignedInfo validation result = True
    // Reference 0 digest verified = True
    // Reference 1 digest verified = True
    // Reference 2 digest verified = Tru


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }