Create PKCS7 Detached Signature (S/MIME)

Create an S/MIME message with a PKCS7 detached signature.

Downloads:

MS Windows Visual C/C++ Libraries

Linux/CentOS C/C++ Libraries

MAC OS X C/C++ Libraries

Solaris C/C++ Libraries

C++ Builder Libraries

#include <C_CkMime.h>
#include <C_CkCert.h>

void ChilkatSample(void)
    {
    HCkMime mime;
    BOOL success;
    HCkCert cert;

    mime = CkMime_Create();

    success = CkMime_UnlockComponent(mime,"Anything for 30-day trial");
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        return;
    }

    //  Load a certificate w/ private key for signing.
    //  There are many ways of getting a certificate object:
    //  from a pfx file, from .cer and private-key files, from the
    //  Windows registry-based certificate stores, etc.
    //  For this example, we'll use a pre-installed cert from
    //  a certificate store.
    cert = CkCert_Create();
    success = CkCert_LoadByCommonName(cert,"Chilkat Software, Inc.");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        return;
    }

    //  Create a very simple MIME message to be signed:
    CkMime_AddHeaderField(mime,"Subject","This is a test");
    CkMime_AddHeaderField(mime,"MyCustomHeader","abc123");
    CkMime_putContentType(mime,"text/plain");
    CkMime_SetBody(mime,"This is a plain-text body.");

    //  Examine the MIME prior to signing:
    printf("--- MIME prior to signing ---\n");
    printf("%s\n",CkMime_getMime(mime));

    //  The MIME prior to signing looks like this:
    //  -------------------------------------------------------------------------------
    //  
Subject: This is a test
MyCustomHeader: abc123
Content-Type: text/plain

This is a plain-text body.
    //  -------------------------------------------------------------------------------

    //  The default hash algorithm used in the signing process is "SHA1".
    //  To change it, set the SigningHashAlg property:
    CkMime_putSigningHashAlg(mime,"SHA256");

    //  Add a detached signature:
    success = CkMime_AddDetachedSignature(mime,cert);
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        return;
    }

    //  Examine the MIME with detached signature:
    printf("--- MIME with detached signature ---\n");
    printf("%s\n",CkMime_getMime(mime));

    //  The MIME after signing looks like this:
    //  -------------------------------------------------------------------------------
    //  
Content-Type: multipart/signed;
 boundary="----=_NextPart_a66_7f43_247e22d0.a03166d5";
 protocol="application/x-pkcs7-signature"; micalg="sha256"

This is a multi-part message in MIME format.

------=_NextPart_a66_7f43_247e22d0.a03166d5
Subject: This is a test
MyCustomHeader: abc123
Content-Type: text/plain

This is a plain-text body.
------=_NextPart_a66_7f43_247e22d0.a03166d5
Content-Transfer-Encoding: base64
Content-Type: application/x-pkcs7-signature;
 name="smime.p7s"
Content-Disposition: attachment; filename="smime.p7s"

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------=_NextPart_a66_7f43_247e22d0.a03166d5--
    //  -------------------------------------------------------------------------------


    CkMime_Dispose(mime);
    CkCert_Dispose(cert);

    }