(PureBasic) IMAP Download and Verify Signed MIME

Downloads the original MIME of a digitally signed email and saves the .p7s signature along with other MIME parts. It then imports the email into a Chilkat email object to unwrap the S/MIME and verify the signature, and subsequently saves the attachments if they haven't been saved already.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkMime.pb"
IncludeFile "CkImap.pb"
IncludeFile "CkEmail.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkCert.pb"
IncludeFile "CkStringTable.pb"

Procedure ChilkatExample()

    success.i = 0

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

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

    ; Connect to an IMAP server.
    ; Use TLS
    CkImap::setCkSsl(imap, 1)
    CkImap::setCkPort(imap, 993)
    success = CkImap::ckConnect(imap,"imap.example.com")
    If success = 0
        Debug CkImap::ckLastErrorText(imap)
        CkImap::ckDispose(imap)
        ProcedureReturn
    EndIf

    success = CkImap::ckLogin(imap,"myLogin","myPassword")
    If success = 0
        Debug CkImap::ckLastErrorText(imap)
        CkImap::ckDispose(imap)
        ProcedureReturn
    EndIf

    ; Select an IMAP mailbox
    success = CkImap::ckSelectMailbox(imap,"Inbox")
    If success = 0
        Debug CkImap::ckLastErrorText(imap)
        CkImap::ckDispose(imap)
        ProcedureReturn
    EndIf

    ; Download the 1st email (as MIME) in the Inbox by sequence number.
    sbMime.i = CkStringBuilder::ckCreate()
    If sbMime.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkImap::ckFetchSingleAsMimeSb(imap,1,0,sbMime)
    If success = 0
        Debug CkImap::ckLastErrorText(imap)
        CkImap::ckDispose(imap)
        CkStringBuilder::ckDispose(sbMime)
        ProcedureReturn
    EndIf

    ; Load it into a MIME object and check to see if it is signed
    mime.i = CkMime::ckCreate()
    If mime.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkMime::ckLoadMimeSb(mime,sbMime)
    alreadySavedParts.i = 0
    If CkMime::ckContainsSignedParts(mime) = 1

        ; This will save the .p7s and other parts...
        st.i = CkStringTable::ckCreate()
        If st.i = 0
            Debug "Failed to create object."
            ProcedureReturn
        EndIf

        success = CkMime::ckPartsToFiles(mime,"c:/temp/qa_output",st)
        If success = 1
            numFiles.i = CkStringTable::ckCount(st)
            i.i = 0
            While i < numFiles
                Debug "Created: " + CkStringTable::ckStringAt(st,i)
                i = i + 1
            Wend
            alreadySavedParts = 1
        EndIf

    EndIf

    ; Load the MIME into an Email object.  This unwraps the security layers and verifies signatures.
    email.i = CkEmail::ckCreate()
    If email.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkEmail::ckSetFromMimeSb(email,sbMime)

    If CkEmail::ckReceivedSigned(email) = 1

        Debug "This email was signed."

        ; Check to see if the signatures were verified.
        If CkEmail::ckSignaturesValid(email) = 1
            Debug "Digital signature(s) verified."

            Debug "Signer: " + CkEmail::ckSignedBy(email)

            ; The certificate used for signing may be obtained
            ; by calling email.GetSignedByCert.
            cert.i = CkCert::ckCreate()
            If cert.i = 0
                Debug "Failed to create object."
                ProcedureReturn
            EndIf

            success = CkEmail::ckLastSignerCert(email,i,cert)
            If success = 0
                Debug "Failed to get signing certificate object."
            Else
                Debug "Signing cert: " + CkCert::ckSubjectCN(cert)
            EndIf

        EndIf

    Else
        Debug "Digital signature verification failed."
    EndIf

    If alreadySavedParts <> 1
        CkEmail::ckSaveAllAttachments(email,"c:/temp/qa_output")
    EndIf



    CkImap::ckDispose(imap)
    CkStringBuilder::ckDispose(sbMime)
    CkMime::ckDispose(mime)
    CkStringTable::ckDispose(st)
    CkEmail::ckDispose(email)
    CkCert::ckDispose(cert)


    ProcedureReturn
EndProcedure