(C) Verify HMAC XML Digital Signature

Demonstrates how to validate an XML digital signature signed with an HMAC key.

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#include <C_CkHttp.h>
#include <C_CkStringBuilder.h>
#include <C_CkXmlDSig.h>

void ChilkatSample(void)
    {
    const char *url;
    HCkHttp http;
    HCkStringBuilder sbXml;
    BOOL success;
    HCkXmlDSig verifier;
    BOOL bVerified;

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

    // The XML containing the Signature to be verified contains the following:

    // <?xml version="1.0" encoding="UTF-8" standalone="no"?>
    // <collection Id="root">
    // 	<album>
    // 		<title>Questions, unanswered</title>
    // 		<artist>Steve and the flubberblubs</artist>
    // 		<year>1989</year>
    // 		<t:tracks xmlns:t="http://test.xades4j/tracks">
    // 			<t:song length="4:05" tracknumber="1">
    // 				<t:title>What do you know?</t:title>
    // 				<t:artist>Steve and the flubberblubs</t:artist>
    // 				<t:lastplayed>2006-10-17-08:31</t:lastplayed>
    // 			</t:song>
    // 			<t:song length="3:45" tracknumber="2">
    // 				<t:title>Who do you know?</t:title>
    // 				<t:artist>Steve and the flubberblubs</t:artist>
    // 				<t:lastplayed>2006-10-17-08:35</t:lastplayed>
    // 			</t:song>
    // 			<t:song length="5:14" tracknumber="3">
    // 				<t:title>When do you know?</t:title>
    // 				<t:artist>Steve and the flubberblubs</t:artist>
    // 				<t:lastplayed>2006-10-17-08:39</t:lastplayed>
    // 			</t:song>
    // 			<t:song length="4:19" tracknumber="4">
    // 				<t:title>Do you know?</t:title>
    // 				<t:artist>Steve and the flubberblubs</t:artist>
    // 				<t:lastplayed>2006-10-17-08:44</t:lastplayed>
    // 			</t:song>
    // 		</t:tracks>
    // 	</album>
    // <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#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#hmac-sha256"/><ds:Reference URI="#root"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>rD/g8soqKz8EiPUBhEWfcQacS0ta4ULHX3dKMEH6ZoQ=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>R8dXP95VRYJBfL6d0Peogybdk27+R+JIfX8jnVu0NOI=</ds:SignatureValue></ds:Signature></collection>

    // The above XML is available at https://www.chilkatsoft.com/exampleData/hmacSigned.xml
    // First fetch the XML..

    url = "https://www.chilkatsoft.com/exampleData/hmacSigned.xml";
    http = CkHttp_Create();
    sbXml = CkStringBuilder_Create();
    success = CkHttp_QuickGetSb(http,url,sbXml);
    if (success != TRUE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbXml);
        return;
    }

    verifier = CkXmlDSig_Create();

    // Load the XML containing the signature to be verified.
    success = CkXmlDSig_LoadSignatureSb(verifier,sbXml);
    if (success != TRUE) {
        printf("%s\n",CkXmlDSig_lastErrorText(verifier));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbXml);
        CkXmlDSig_Dispose(verifier);
        return;
    }

    // Provide the HMAC key
    // The HMAC key for this signature is the us-ascii bytes of the string "secret",
    // It can be set in any of the following ways (and also more ways not shown here..)
    CkXmlDSig_SetHmacKey(verifier,"secret","ascii");
    // or
    CkXmlDSig_SetHmacKey(verifier,"c2VjcmV0","base64");
    // or
    CkXmlDSig_SetHmacKey(verifier,"736563726574","hex");

    // Verify the signature
    bVerified = CkXmlDSig_VerifySignature(verifier,TRUE);
    printf("Signature verified = %d\n",bVerified);


    CkHttp_Dispose(http);
    CkStringBuilder_Dispose(sbXml);
    CkXmlDSig_Dispose(verifier);

    }