(MFC) Decrypt MIME using RSAES-OAEP with SHA256 and AES-128 content encryption

Demonstrates how to decrypt MIME what was encrypted with RSAES-OAEP with SHA256 and AES-128 content encryption.

In actuality, we don't really need to know in advance the various algorithms used to encrypt the MIME. When decrypting, the information about the algorithms required are embedded in the PCKS7 message itself, and this tells a decryptor what it should use.

Note: This example requires Chilkat v9.5.0.67 or greater.

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

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

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

    // We begin with this encrypted MIME:

    // Content-Type: application/x-pkcs7-mime; name="smime.p7m"; smime-type="enveloped-data"
    // someHeader1: Some value 1
    // someHeader2: Some value 2
    // Content-Disposition: attachment; filename="smime.p7m"
    // Content-Transfer-Encoding: base64
    // 
    // MIIDvAYJKoZIhvcNAQcDoIIDrTCCA6kCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw
    // CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ
    // dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP
    // oA0wCwYJYIZIAWUDBAIBBIIBAFaUL1ga1bOrdqYKcMm+FHUacBvzfBxk0fnPA0AMBdN8BvTWT3CN
    // YuqBhjOGyq0FpYD9pVZybUuFMCVsVyIW2O62HnsOK58YaPEUUcdH2sI+yjqX9UAn0P0nVDSsVdeK
    // W8x9kMfZg+3UP+y1q+lu7VRJO3f2C9oLQpTkc4VW4n7UOcUI0waykLCjCTL8lFDb7/J3GeuMKyhH
    // 5riNz50kpbzqn7m2Ks9yA+QmcTdXclclGFr2vwEUFzSdT2pxh/vaUrogCxkYWbQ2eV7vZg6O4kV0
    // aqHBqySkPTAzHKiHH8K8GVdlTuJ8350CpICa4T8w7/Ht5I7dyOPPKy4C+rVtrvcwggH+BgkqhkiG
    // 9w0BBwEwHQYJYIZIAWUDBAECBBDTC2WNBN+z2I47/4Feu9YqgIIB0MZvl3nC/q/Wzil6HtfQTr12
    // Q5moHY+ORzAa1P9XvX2ZUFhW530mV395mQw/A4o4ekmX9eRPEZquYzZPLT8hNeZIuNdhpcSQUmad
    // rKnKkR0wKJ3jJ3LhOIohVBQSYs8kVDZKq6lJBIznlsurFelZoNEhyRschhteDZx5rb7fCe8c2+/O
    // DHxaqaHCAzm/Bd7kcg6FFfuTZy3tu0PgP5IsXN4OFA3kkvwjAs4XsVS8jdIcmDNBkYieE8WmJOIm
    // Mz7mh/CHWLgWfGKa0Dkb9RcbFgLwYNT3GzuXFw9XPbKkEZjEAtJajWbN6P0WQl96YYd9qZxUpGxZ
    // zjTHEYzViUdUXolfpLufttrRXyxN1RFWhNFMFbv66xYqklMSgpdM/Mbk+EuvX6eXayDPvDBpfYMw
    // NoRAzv1Ony2c0ez9rBemJICicxAzpuvHbRxdjYs63Dnv+TYgpBK12AxWWpPIjXvw0WQKgTC3Tg8s
    // EnuGhpENqso/clJBEBSn4+2WhYtYbdI5sVme67lvqQl1Xxy3r18SWaQbyDOwgYi1E+54lMDOxMy0
    // y0FPHk5pP45DnXWj+XORPp5LhuZr5mf62YOXSSUwR5P0cXy4Rc+pN5lhRQPCf5z2

    bool success;
    CkStringBuilder sb;
    bool bCrlf = true;
    sb.AppendLine("Content-Type: application/x-pkcs7-mime; name=\"smime.p7m\"; smime-type=\"enveloped-data\"",bCrlf);
    sb.AppendLine("someHeader1: Some value 1",bCrlf);
    sb.AppendLine("someHeader2: Some value 2",bCrlf);
    sb.AppendLine("Content-Disposition: attachment; filename=\"smime.p7m\"",bCrlf);
    sb.AppendLine("Content-Transfer-Encoding: base64",bCrlf);
    sb.AppendLine("",bCrlf);
    sb.AppendLine("MIIDvAYJKoZIhvcNAQcDoIIDrTCCA6kCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw",bCrlf);
    sb.AppendLine("CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ",bCrlf);
    sb.AppendLine("dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP",bCrlf);
    sb.AppendLine("oA0wCwYJYIZIAWUDBAIBBIIBAFaUL1ga1bOrdqYKcMm+FHUacBvzfBxk0fnPA0AMBdN8BvTWT3CN",bCrlf);
    sb.AppendLine("YuqBhjOGyq0FpYD9pVZybUuFMCVsVyIW2O62HnsOK58YaPEUUcdH2sI+yjqX9UAn0P0nVDSsVdeK",bCrlf);
    sb.AppendLine("W8x9kMfZg+3UP+y1q+lu7VRJO3f2C9oLQpTkc4VW4n7UOcUI0waykLCjCTL8lFDb7/J3GeuMKyhH",bCrlf);
    sb.AppendLine("5riNz50kpbzqn7m2Ks9yA+QmcTdXclclGFr2vwEUFzSdT2pxh/vaUrogCxkYWbQ2eV7vZg6O4kV0",bCrlf);
    sb.AppendLine("aqHBqySkPTAzHKiHH8K8GVdlTuJ8350CpICa4T8w7/Ht5I7dyOPPKy4C+rVtrvcwggH+BgkqhkiG",bCrlf);
    sb.AppendLine("9w0BBwEwHQYJYIZIAWUDBAECBBDTC2WNBN+z2I47/4Feu9YqgIIB0MZvl3nC/q/Wzil6HtfQTr12",bCrlf);
    sb.AppendLine("Q5moHY+ORzAa1P9XvX2ZUFhW530mV395mQw/A4o4ekmX9eRPEZquYzZPLT8hNeZIuNdhpcSQUmad",bCrlf);
    sb.AppendLine("rKnKkR0wKJ3jJ3LhOIohVBQSYs8kVDZKq6lJBIznlsurFelZoNEhyRschhteDZx5rb7fCe8c2+/O",bCrlf);
    sb.AppendLine("DHxaqaHCAzm/Bd7kcg6FFfuTZy3tu0PgP5IsXN4OFA3kkvwjAs4XsVS8jdIcmDNBkYieE8WmJOIm",bCrlf);
    sb.AppendLine("Mz7mh/CHWLgWfGKa0Dkb9RcbFgLwYNT3GzuXFw9XPbKkEZjEAtJajWbN6P0WQl96YYd9qZxUpGxZ",bCrlf);
    sb.AppendLine("zjTHEYzViUdUXolfpLufttrRXyxN1RFWhNFMFbv66xYqklMSgpdM/Mbk+EuvX6eXayDPvDBpfYMw",bCrlf);
    sb.AppendLine("NoRAzv1Ony2c0ez9rBemJICicxAzpuvHbRxdjYs63Dnv+TYgpBK12AxWWpPIjXvw0WQKgTC3Tg8s",bCrlf);
    sb.AppendLine("EnuGhpENqso/clJBEBSn4+2WhYtYbdI5sVme67lvqQl1Xxy3r18SWaQbyDOwgYi1E+54lMDOxMy0",bCrlf);
    sb.AppendLine("y0FPHk5pP45DnXWj+XORPp5LhuZr5mf62YOXSSUwR5P0cXy4Rc+pN5lhRQPCf5z2",bCrlf);

    // Load the encrypted MIME into the MIME object.
    CkMime mime;
    mime.LoadMimeSb(sb);

    // Provide the required cert + private key from a PFX (.pfx/.p12) file.
    success = mime.AddPfxSourceFile("qa_data/rsaes-oaep/cert_plus_privatekey.pfx","PFX_PASSWORD");
    if (success != true) {
        strOut.append(mime.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Decrypt.
    success = mime.Decrypt();
    if (success != true) {
        strOut.append(mime.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Examine the decrypted MIME.
    strOut.append(mime.getMime());
    strOut.append("\r\n");
    strOut.append("Decrypt test 1 succeeded.");
    strOut.append("\r\n");

    // -----------------------------------------------------------
    // Now let's decrypt another way..
    // We have the same cert and private key in PEM files..

    CkCert cert;
    success = cert.LoadFromFile("qa_data/rsaes-oaep/cert.pem");

    CkPrivateKey privKey;
    success = privKey.LoadPemFile("qa_data/rsaes-oaep/privatekey.pem");

    // Decrypt using the cert + private key
    CkMime mime2;
    mime2.LoadMimeSb(sb);

    success = mime2.Decrypt2(cert,privKey);
    if (success != true) {
        strOut.append(mime2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Examine the decrypted MIME.
    strOut.append(mime2.getMime());
    strOut.append("\r\n");
    strOut.append("Decrypt test 2 succeeded.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }