(MFC) Get Public Key from CSR

Demonstrates how to get the public key from a CSR.

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

See Also: Using MFC CString in Chilkat

#include <CkPem.h>
#include <CkAsn.h>
#include <CkXml.h>
#include <CkBinData.h>
#include <CkPublicKey.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkPem pem;

    // No password is required.  Pass an empty password string..
    const char *noPassword = "";
    bool success = pem.LoadPemFile("qa_data/csr/csr2.pem",noPassword);
    if (success != true) {
        strOut.append(pem.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    const char *strBase64 = pem.getEncodedItem("csr","","base64",0);

    CkAsn asn;
    success = asn.LoadEncoded(strBase64,"base64");
    if (success != true) {
        strOut.append(asn.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Convert the ASN.1 to XML.
    CkXml xml;
    success = xml.LoadXml(asn.asnToXml());
    strOut.append(xml.getXml());
    strOut.append("\r\n");
    strOut.append("----");
    strOut.append("\r\n");

    const char *strModulusHex = xml.getChildContent("bits");
    strOut.append("strModulusHex = ");
    strOut.append(strModulusHex);
    strOut.append("\r\n");
    strOut.append("----");
    strOut.append("\r\n");

    // We need the modulus as base64.
    CkBinData bd;
    bd.AppendEncoded(strModulusHex,"hex");
    const char *modulus64 = bd.getEncoded("base64");
    strOut.append("modulus64 = ");
    strOut.append(modulus64);
    strOut.append("\r\n");
    strOut.append("----");
    strOut.append("\r\n");

    // Build the XML for the public key.
    CkXml xmlPubKey;
    xmlPubKey.put_Tag("RSAPublicKey");
    xmlPubKey.UpdateChildContent("Modulus",modulus64);
    // The RSA exponent will always be decimal 65537 (base64 = AQAB)
    xmlPubKey.UpdateChildContent("Exponent","AQAB");

    strOut.append("RSA public key as XML:");
    strOut.append("\r\n");
    strOut.append(xmlPubKey.getXml());
    strOut.append("\r\n");
    strOut.append("----");
    strOut.append("\r\n");

    // Load the XML into a Chilkat public key object.
    CkPublicKey pubkey;
    success = pubkey.LoadFromString(xmlPubKey.getXml());
    if (success != true) {
        strOut.append(pubkey.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Show the public key as PEM.
    bool preferPkcs1 = true;
    strOut.append(pubkey.getPem(preferPkcs1));
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }