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

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

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

See Also: Using MFC CString in Chilkat

#include <CkMime.h>
#include <CkCert.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkMime mime;

    // Load an S/MIME message from a file:
    bool success = mime.LoadMimeFile("signedMime.txt");
    if (success != true) {
        strOut.append(mime.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

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

    // We don't want the "unwrap extras".  You'll see what those
    // are in a few moments...
    mime.put_UnwrapExtras(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 = mime.UnwrapSecurity();
    if (success != true) {
        // UnwrapSecurity returns true if all signatures were
        // verified and all parts decrypted.
        strOut.append(mime.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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:
        CkCert *signerCert = mime.GetSignerCert(0);
        if (mime.get_LastMethodSuccess() == true) {
            strOut.append("**** Signer Cert: ");
            strOut.append(signerCert->subjectCN());
            strOut.append("\r\n");
            delete 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:
        CkCert *encryptCert = mime.GetEncryptCert(0);
        if (mime.get_LastMethodSuccess() == true) {
            strOut.append("**** Encrypt Cert: ");
            strOut.append(encryptCert->subjectCN());
            strOut.append("\r\n");
            delete encryptCert;
        }

    }

    // Display the unwrapped MIME:
    strOut.append(mime.getMime());
    strOut.append("\r\n");

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


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }