(PureBasic) 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 PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkCert.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkMime.pb"
IncludeFile "CkPrivateKey.pb"

Procedure ChilkatExample()

    ; 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

    success.i
    sb.i = CkStringBuilder::ckCreate()
    If sb.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    bCrlf.i = 1
    CkStringBuilder::ckAppendLine(sb,"Content-Type: application/x-pkcs7-mime; name=" + Chr(34) + "smime.p7m" + Chr(34) + "; smime-type=" + Chr(34) + "enveloped-data" + Chr(34),bCrlf)
    CkStringBuilder::ckAppendLine(sb,"someHeader1: Some value 1",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"someHeader2: Some value 2",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"Content-Disposition: attachment; filename=" + Chr(34) + "smime.p7m" + Chr(34),bCrlf)
    CkStringBuilder::ckAppendLine(sb,"Content-Transfer-Encoding: base64",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"MIIDvAYJKoZIhvcNAQcDoIIDrTCCA6kCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"oA0wCwYJYIZIAWUDBAIBBIIBAFaUL1ga1bOrdqYKcMm+FHUacBvzfBxk0fnPA0AMBdN8BvTWT3CN",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"YuqBhjOGyq0FpYD9pVZybUuFMCVsVyIW2O62HnsOK58YaPEUUcdH2sI+yjqX9UAn0P0nVDSsVdeK",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"W8x9kMfZg+3UP+y1q+lu7VRJO3f2C9oLQpTkc4VW4n7UOcUI0waykLCjCTL8lFDb7/J3GeuMKyhH",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"5riNz50kpbzqn7m2Ks9yA+QmcTdXclclGFr2vwEUFzSdT2pxh/vaUrogCxkYWbQ2eV7vZg6O4kV0",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"aqHBqySkPTAzHKiHH8K8GVdlTuJ8350CpICa4T8w7/Ht5I7dyOPPKy4C+rVtrvcwggH+BgkqhkiG",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"9w0BBwEwHQYJYIZIAWUDBAECBBDTC2WNBN+z2I47/4Feu9YqgIIB0MZvl3nC/q/Wzil6HtfQTr12",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"Q5moHY+ORzAa1P9XvX2ZUFhW530mV395mQw/A4o4ekmX9eRPEZquYzZPLT8hNeZIuNdhpcSQUmad",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"rKnKkR0wKJ3jJ3LhOIohVBQSYs8kVDZKq6lJBIznlsurFelZoNEhyRschhteDZx5rb7fCe8c2+/O",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"DHxaqaHCAzm/Bd7kcg6FFfuTZy3tu0PgP5IsXN4OFA3kkvwjAs4XsVS8jdIcmDNBkYieE8WmJOIm",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"Mz7mh/CHWLgWfGKa0Dkb9RcbFgLwYNT3GzuXFw9XPbKkEZjEAtJajWbN6P0WQl96YYd9qZxUpGxZ",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"zjTHEYzViUdUXolfpLufttrRXyxN1RFWhNFMFbv66xYqklMSgpdM/Mbk+EuvX6eXayDPvDBpfYMw",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"NoRAzv1Ony2c0ez9rBemJICicxAzpuvHbRxdjYs63Dnv+TYgpBK12AxWWpPIjXvw0WQKgTC3Tg8s",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"EnuGhpENqso/clJBEBSn4+2WhYtYbdI5sVme67lvqQl1Xxy3r18SWaQbyDOwgYi1E+54lMDOxMy0",bCrlf)
    CkStringBuilder::ckAppendLine(sb,"y0FPHk5pP45DnXWj+XORPp5LhuZr5mf62YOXSSUwR5P0cXy4Rc+pN5lhRQPCf5z2",bCrlf)

    ; Load the encrypted MIME into the MIME object.
    mime.i = CkMime::ckCreate()
    If mime.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkMime::ckLoadMimeSb(mime,sb)

    ; Provide the required cert + private key from a PFX (.pfx/.p12) file.
    success = CkMime::ckAddPfxSourceFile(mime,"qa_data/rsaes-oaep/cert_plus_privatekey.pfx","PFX_PASSWORD")
    If success <> 1
        Debug CkMime::ckLastErrorText(mime)
        CkStringBuilder::ckDispose(sb)
        CkMime::ckDispose(mime)
        ProcedureReturn
    EndIf

    ; Decrypt.
    success = CkMime::ckDecrypt(mime)
    If success <> 1
        Debug CkMime::ckLastErrorText(mime)
        CkStringBuilder::ckDispose(sb)
        CkMime::ckDispose(mime)
        ProcedureReturn
    EndIf

    ; Examine the decrypted MIME.
    Debug CkMime::ckGetMime(mime)
    Debug "Decrypt test 1 succeeded."

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

    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadFromFile(cert,"qa_data/rsaes-oaep/cert.pem")

    privKey.i = CkPrivateKey::ckCreate()
    If privKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPrivateKey::ckLoadPemFile(privKey,"qa_data/rsaes-oaep/privatekey.pem")

    ; Decrypt using the cert + private key
    mime2.i = CkMime::ckCreate()
    If mime2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkMime::ckLoadMimeSb(mime2,sb)

    success = CkMime::ckDecrypt2(mime2,cert,privKey)
    If success <> 1
        Debug CkMime::ckLastErrorText(mime2)
        CkStringBuilder::ckDispose(sb)
        CkMime::ckDispose(mime)
        CkCert::ckDispose(cert)
        CkPrivateKey::ckDispose(privKey)
        CkMime::ckDispose(mime2)
        ProcedureReturn
    EndIf

    ; Examine the decrypted MIME.
    Debug CkMime::ckGetMime(mime2)
    Debug "Decrypt test 2 succeeded."


    CkStringBuilder::ckDispose(sb)
    CkMime::ckDispose(mime)
    CkCert::ckDispose(cert)
    CkPrivateKey::ckDispose(privKey)
    CkMime::ckDispose(mime2)


    ProcedureReturn
EndProcedure