Remove All S/MIME Security Layers (UnwrapSecurity)

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Demonstrates the Chilkat Mime.UnwrapSecurity method, which removes supported S/MIME security layers and restores the underlying MIME content. It takes no arguments and handles both layer orders: signed-then-encrypted and encrypted-then-signed.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A message can be both signed and encrypted, in either order, producing nested S/MIME wrappers. UnwrapSecurity peels them all off in one call — verifying signatures and decrypting as it goes — so you do not have to detect the layering and call Verify and Decrypt in the right sequence yourself. Decryption still requires the recipient's certificate and private key to be configured.

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#include <C_CkMime.h>

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

    success = FALSE;

    //  Demonstrates the Mime.UnwrapSecurity method, which removes supported S/MIME security layers and
    //  restores the underlying MIME content.  It takes no arguments and handles both layer orders
    //  (signed-then-encrypted and encrypted-then-signed).

    mime = CkMime_Create();
    success = CkMime_LoadMimeFile(mime,"qa_data/secured.eml");
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    //  A single call peels off the signature and/or encryption layers.  (Decryption requires the
    //  appropriate certificate/private key to be configured first.)
    success = CkMime_UnwrapSecurity(mime);
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    printf("Security layers removed. Content-Type is now: %s\n",CkMime_contentType(mime));


    CkMime_Dispose(mime);

    }