Unicode C

Verify XML Signature with External Data Reference

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

Unicode C

#include <C_CkHttpW.h>
#include <C_CkStringBuilderW.h>
#include <C_CkXmlDSigW.h>
#include <C_CkBinDataW.h>

void ChilkatSample(void)
    {
    BOOL success;
    const wchar_t *url;
    HCkHttpW http;
    HCkStringBuilderW sbXml;
    HCkXmlDSigW verifier;
    const wchar_t *refUri;
    HCkBinDataW jpgData;
    BOOL bVerified;

    success = FALSE;

    // 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"?>
    // <abc>
    //   <xyz>
    //     <jpg>
    //         <name>starfish.jpg</name>
    //         <url>https://www.chilkatsoft.com/images/starfish.jpg</url>
    //     <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#rsa-sha256"/><ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>MbHOti6nOh9DJP/u7u1+a1u0wRYIGEdaAVk5ehxqeBhcR4qvGvCQ7wLxcfDuwFG2grSg43ANxDYngLqZTeFb5nCfywcuNBQI8FrNRVY5hkyv6kDW1BVN8ot9qPYX9oHxJp1e+nMszIiSxqHX3XDI7YnvFt/0CyeO5JaQQEzXzIwqqb8iUNcH/bJzR6CrTf1hGuQ5MPorG0bRwbYPPHHzipUqHBinK8VbHobnxL7GQHAhR8k9gDD35kZcMxf/74U7pGO19ZzTbdJW5S7q4bVVxvsuU3itTbhHI60pOE14ibrjZtIrPZLVUD3TQqIIF04TChW2NXdYOo3+ij4ZnP8x+g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
    //   </xyz>
    // </abc>

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

    url = L"https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml";
    http = CkHttpW_Create();
    sbXml = CkStringBuilderW_Create();
    success = CkHttpW_QuickGetSb(http,url,sbXml);
    if (success != TRUE) {
        wprintf(L"%s\n",CkHttpW_lastErrorText(http));
        CkHttpW_Dispose(http);
        CkStringBuilderW_Dispose(sbXml);
        return;
    }

    verifier = CkXmlDSigW_Create();

    // Load the XML containing the signatures to be verified.
    // Note that this particular Signature already contains the RSA public key that will be used
    // for verification.
    success = CkXmlDSigW_LoadSignatureSb(verifier,sbXml);
    if (success != TRUE) {
        wprintf(L"%s\n",CkXmlDSigW_lastErrorText(verifier));
        CkHttpW_Dispose(http);
        CkStringBuilderW_Dispose(sbXml);
        CkXmlDSigW_Dispose(verifier);
        return;
    }

    // Get the Reference URI, which in this case is the URL to the binary data that was hashed.
    // This fetchs the URI attribute value from:  <ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg">
    refUri = CkXmlDSigW_referenceUri(verifier,0);
    if (CkXmlDSigW_getLastMethodSuccess(verifier) != TRUE) {
        wprintf(L"No reference URI found.\n");
        CkHttpW_Dispose(http);
        CkStringBuilderW_Dispose(sbXml);
        CkXmlDSigW_Dispose(verifier);
        return;
    }

    // Download the JPG data to be verified.
    jpgData = CkBinDataW_Create();
    success = CkHttpW_QuickGetBd(http,refUri,jpgData);
    if (success != TRUE) {
        wprintf(L"%s\n",CkHttpW_lastErrorText(http));
        CkHttpW_Dispose(http);
        CkStringBuilderW_Dispose(sbXml);
        CkXmlDSigW_Dispose(verifier);
        CkBinDataW_Dispose(jpgData);
        return;
    }

    // Provide the JPG data to the verifier
    CkXmlDSigW_SetRefDataBd(verifier,0,jpgData);

    // Verify the signature
    bVerified = CkXmlDSigW_VerifySignature(verifier,TRUE);
    wprintf(L"Signature verified = %d\n",bVerified);


    CkHttpW_Dispose(http);
    CkStringBuilderW_Dispose(sbXml);
    CkXmlDSigW_Dispose(verifier);
    CkBinDataW_Dispose(jpgData);

    }