(MFC) Add DKIM-Signature Header to MIME / Email

Demonstrates how to add a DKIM-Signature header field to a MIME message.

Note: The DKIM / DomainKey functionality is included with the Chilkat MIME license.

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

See Also: Using MFC CString in Chilkat

#include <CkDkim.h>
#include <CkByteData.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkDkim dkim;

    // To create a DKIM signature for email (i.e. MIME),
    // you'll need to provide the following:
    // (1) An RSA private key in any common file format.
    // (2) The domain name (typically the same domain
    // as the sender of an email).
    // (3) A selector for the domain name -- an arbitrary string
    // to identify the matching public key in DNS.

    // To allow an email recipient to verify the DKIM signature via an
    // external email client supporting DKIM or using other software,
    // you will need to create a DNS record with the selector
    // and matching public key.  This example does not provide
    // information about DKIM DNS record creation.  
    // (Chilkat does not provide an API for creating DNS records.  
    // Creating the DKIM DNS record is something you would do
    // manually.)

    // Set the domain and selector:
    // You'll need to provide your own values here..
    dkim.put_DkimDomain("chilkatsoft.com");
    dkim.put_DkimSelector("tuna");

    // Load a private key from any common RSA private key
    // format, such as DER, PKCS8, PEM, XML, etc.
    // The LoadDkimPkFile method automatically detects
    // the file format and reads it appropriately.
    // If a password is not required, you'll still need to provide
    // a password string argument, but it is ignored.
    const char *password = 0;
    password = "optionalPassword";
    bool success = dkim.LoadDkimPkFile("myPrivateKey.pem",password);
    if (success != true) {
        strOut.append(dkim.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Load a MIME file.
    CkByteData mimeData;
    success = mimeData.loadFile("testMessage.eml");
    if (success != true) {
        strOut.append("Failed to load file.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Sign it.  This adds the DKIM-Signature header and
    // returns the new MIME with DKIM-Signature added.
    CkByteData dkimSignedMime;
    success = dkim.AddDkimSignature(mimeData,dkimSignedMime);
    if (success != true) {
        strOut.append(dkim.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    success = dkimSignedMime.saveFile("dkimSigned.eml");
    if (success != true) {
        strOut.append("Failed to save file.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Success.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }