(C) Decrypt S/MIME and Verify S/MIME Signatures

C example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

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

void ChilkatSample(void)
    {
    HCkMime mime;
    BOOL success;
    BOOL isEncrypted;
    BOOL isSigned;
    HCkCert signerCert;
    HCkCert encryptCert;

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

    mime = CkMime_Create();

    // Load an S/MIME message from a file:
    success = CkMime_LoadMimeFile(mime,"signedMime.txt");
    if (success != TRUE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    // The ContainsEncryptedParts/ContainsSignedParts methods
    // can be called to determine if the MIME is encrypted and/or signed:
    isEncrypted = CkMime_ContainsEncryptedParts(mime);
    isSigned = CkMime_ContainsSignedParts(mime);

    // We don't want the "unwrap extras".  You'll see what those
    // are in a few moments...
    CkMime_putUnwrapExtras(mime,FALSE);

    // To verify the signature, call UnwrapSecurity.  This will
    // verify the signature(s) and decrypt the S/MIME and restore
    // the MIME to the unsigned/unencrypted state.
    // The results of what was found are present in the MIME object's
    // properties, as well as extra header fields that are added
    // to the unwrapped MIME.
    success = CkMime_UnwrapSecurity(mime);
    if (success != TRUE) {
        // UnwrapSecurity returns TRUE if all signatures were
        // verified and all parts decrypted.
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    // The mime.UnwrapExtras property controls whether or not
    // these additional fields are added to the unwrapped MIME:
    // 
    // X-NumPartsSigned: 1
    // X-SignaturesValid: yes
    // X-NumPartsEncrypted: 1
    // X-Decrypted: no
    // 
    // The X-NumPartsSigned/X-SignaturesValid headers are added
    // if the MIME was signed.  
    // 
    // The X-NumPartsEncrypted/X-Decrypted headers are added
    // if the MIME was encrypted.
    // 

    // If the MIME was signed, get the certificate used for signing.
    if (isSigned == TRUE) {
        // The NumSignerCerts property indicates how many certificates
        // were used for signing.  This example will assume the value is 1.
        // To get the 1st signer cert, call GetSignerCert with an index of 0:
        signerCert = CkMime_GetSignerCert(mime,0);
        if (CkMime_getLastMethodSuccess(mime) == TRUE) {
            printf("**** Signer Cert: %s\n",CkCert_subjectCN(signerCert));
            CkCert_Dispose(signerCert);
        }

    }

    // If the MIME was encrypted, get the certificate used for encryption:
    if (isEncrypted == TRUE) {
        // The NumEncryptCerts property indicates how many certificates
        // were used for encrypting.  This example will assume the value is 1.
        // To get the 1st encrypt cert, call GetEncryptCert with an index of 0:
        encryptCert = CkMime_GetEncryptCert(mime,0);
        if (CkMime_getLastMethodSuccess(mime) == TRUE) {
            printf("**** Encrypt Cert: %s\n",CkCert_subjectCN(encryptCert));
            CkCert_Dispose(encryptCert);
        }

    }

    // Display the unwrapped MIME:
    printf("%s\n",CkMime_getMime(mime));

    // Save the unwrapped MIME to a file:
    success = CkMime_SaveMime(mime,"unwrappedMime.txt");


    CkMime_Dispose(mime);

    }