(C) 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.

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#include <C_CkDkim.h>
#include <C_CkPrivateKey.h>
#include <C_CkByteData.h>

void ChilkatSample(void)
    {
    HCkDkim dkim;
    const char *password;
    HCkPrivateKey privKey;
    BOOL success;
    HCkByteData mimeData;
    HCkByteData dkimSignedMime;

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

    dkim = CkDkim_Create();

    // 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..
    CkDkim_putDkimDomain(dkim,"chilkatsoft.com");
    CkDkim_putDkimSelector(dkim,"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.

    password = "optionalPassword";
    privKey = CkPrivateKey_Create();
    success = CkPrivateKey_LoadAnyFormatFile(privKey,"myPrivateKey.pem",password);
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkDkim_Dispose(dkim);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    success = CkDkim_SetDkimPrivateKey(dkim,privKey);
    if (success != TRUE) {
        printf("%s\n",CkDkim_lastErrorText(dkim));
        CkDkim_Dispose(dkim);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    // Load a MIME file.
    mimeData = CkByteData_Create();
    success = CkByteData_loadFile(mimeData,"testMessage.eml");
    if (success != TRUE) {
        printf("Failed to load file.\n");
        CkDkim_Dispose(dkim);
        CkPrivateKey_Dispose(privKey);
        CkByteData_Dispose(mimeData);
        return;
    }

    // Sign it.  This adds the DKIM-Signature header and
    // returns the new MIME with DKIM-Signature added.
    dkimSignedMime = CkByteData_Create();
    success = CkDkim_AddDkimSignature(dkim,mimeData,dkimSignedMime);
    if (success != TRUE) {
        printf("%s\n",CkDkim_lastErrorText(dkim));
        CkDkim_Dispose(dkim);
        CkPrivateKey_Dispose(privKey);
        CkByteData_Dispose(mimeData);
        CkByteData_Dispose(dkimSignedMime);
        return;
    }

    success = CkByteData_saveFile(dkimSignedMime,"dkimSigned.eml");
    if (success != TRUE) {
        printf("Failed to save file.\n");
        CkDkim_Dispose(dkim);
        CkPrivateKey_Dispose(privKey);
        CkByteData_Dispose(mimeData);
        CkByteData_Dispose(dkimSignedMime);
        return;
    }

    printf("Success.\n");


    CkDkim_Dispose(dkim);
    CkPrivateKey_Dispose(privKey);
    CkByteData_Dispose(mimeData);
    CkByteData_Dispose(dkimSignedMime);

    }