(Lianja) Verify DKIM-Signature Headers in Downloaded Email

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

Chilkat Lianja Extension Download Chilkat Lianja Extension

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

loImap = createobject("CkImap")

// Connect to an IMAP server, login, select mailbox..
// Use TLS 
loImap.Ssl = .T.
loImap.Port = 993
llSuccess = loImap.Connect("imap.someMailServer.com")
if (llSuccess = .T.) then
    llSuccess = loImap.Login("myLogin","myPassword")
    if (llSuccess = .T.) then
        llSuccess = loImap.SelectMailbox("Inbox")
    endif

endif

if (llSuccess <> .T.) then
    ? loImap.LastErrorText
    release loImap
    return
endif

loDkim = createobject("CkDkim")

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

// Download emails by sequence numbers (not UIDs).
llBUid = .F.

n = loImap.NumMessages
if (n > 10) then
    n = 10
endif

loJson = createobject("CkJsonObject")
loJson.EmitCompact = .F.

// To verify DKIM-Signature headers, we need the exact unmodified MIME bytes of each email.
loMimeData = createobject("CkBinData")
lnSeqNum = 1
do while lnSeqNum <= n
    // The FetchSingleBd method was introduced in v9.5.0.76
    llSuccess = loImap.FetchSingleBd(lnSeqNum,llBUid,loMimeData)
    if (llSuccess <> .T.) then
        ? loImap.LastErrorText
        release loImap
        release loDkim
        release loJson
        release loMimeData
        return
    endif

    // Get the number of DKIM-Signature headers.
    lnNumDkim = loDkim.NumDkimSigs(loMimeData)

    // Verify each..
    j = 0
    do while j < lnNumDkim
        ? "------ DKIM Signature " + str(j)

        llSuccess = loDkim.DkimVerify(j,loMimeData)
        if (llSuccess <> .T.) then
            ? "Not valid."
        else
            ? "valid."
        endif

        // Show the additional information about the signature verification
        loJson.Load(loDkim.VerifyInfo)
        ? loJson.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
    enddo
    lnSeqNum = lnSeqNum + 1
enddo

llSuccess = loImap.Disconnect()


release loImap
release loDkim
release loJson
release loMimeData