PowerBuilder

Verify DKIM-Signature Headers in Downloaded Email

See more DKIM / DomainKey Examples

Downloads email from an IMAP server and verifies the DKIM-Signature header(s) in each email, if present. PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Imap
oleobject loo_Dkim
integer li_BUid
integer li_SeqNum
integer j
integer n
oleobject loo_Json
oleobject loo_MimeData
integer li_NumDkim

li_Success = 0

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

loo_Imap = create oleobject
li_rc = loo_Imap.ConnectToNewObject("Chilkat.Imap")
if li_rc < 0 then
    destroy loo_Imap
    MessageBox("Error","Connecting to COM object failed")
    return
end if

// Connect to an IMAP server, login, select mailbox..
// Use TLS 
loo_Imap.Ssl = 1
loo_Imap.Port = 993
li_Success = loo_Imap.Connect("imap.example.com")
if li_Success = 1 then
    li_Success = loo_Imap.Login("myLogin","myPassword")
    if li_Success = 1 then
        li_Success = loo_Imap.SelectMailbox("Inbox")
    end if

end if

if li_Success <> 1 then
    Write-Debug loo_Imap.LastErrorText
    destroy loo_Imap
    return
end if

loo_Dkim = create oleobject
li_rc = loo_Dkim.ConnectToNewObject("Chilkat.Dkim")

// Download a max of 10 emails and verify any DKIM-Signature headers
// that are present.

// Download emails by sequence numbers (not UIDs).
li_BUid = 0

n = loo_Imap.NumMessages
if n > 10 then
    n = 10
end if

loo_Json = create oleobject
li_rc = loo_Json.ConnectToNewObject("Chilkat.JsonObject")

loo_Json.EmitCompact = 0

// To verify DKIM-Signature headers, we need the exact unmodified MIME bytes of each email.
loo_MimeData = create oleobject
li_rc = loo_MimeData.ConnectToNewObject("Chilkat.BinData")

li_SeqNum = 1
do while li_SeqNum <= n
    // The FetchSingleBd method was introduced in v9.5.0.76
    li_Success = loo_Imap.FetchSingleBd(li_SeqNum,li_BUid,loo_MimeData)
    if li_Success <> 1 then
        Write-Debug loo_Imap.LastErrorText
        destroy loo_Imap
        destroy loo_Dkim
        destroy loo_Json
        destroy loo_MimeData
        return
    end if

    // Get the number of DKIM-Signature headers.
    li_NumDkim = loo_Dkim.NumDkimSigs(loo_MimeData)

    // Verify each..
    j = 0
    do while j < li_NumDkim
        Write-Debug "------ DKIM Signature " + string(j)

        li_Success = loo_Dkim.DkimVerify(j,loo_MimeData)
        if li_Success <> 1 then
            Write-Debug "Not valid."
        else
            Write-Debug "valid."
        end if

        // Show the additional information about the signature verification
        loo_Json.Load(loo_Dkim.VerifyInfo)
        Write-Debug loo_Json.Emit()

        // The JSON contains information such as this:

        // 	{
        // 	  "domain": "amazonses.com",
        // 	  "selector": "7v7vs6w47njt4pimodk5mmttbegzsi6n",
        // 	  "publicKey": "MIGfMA0GCSqG...v2GvWPqGHz6uqeQIDAQAB",
        // 	  "canonicalization": "relaxed/simple",
        // 	  "algorithm": "rsa-sha256",
        // 	  "signedHeaders": "Subject:From:To:Date:Mime-Version:Content-Type:References:Message-Id:Feedback-ID",
        // 	  "verified": "yes"
        // 	}

        j = j + 1
    loop
    li_SeqNum = li_SeqNum + 1
loop

li_Success = loo_Imap.Disconnect()


destroy loo_Imap
destroy loo_Dkim
destroy loo_Json
destroy loo_MimeData