Verify DomainKey-Signature Headers in Downloaded Email

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

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

//  Note: DKIM-Signatures are much more common than DomainKey-Signature
//  See DKIM-Signature Verify Sample.

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

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

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

n = loo_Imap.NumMessages
if n > 50 then
    n = 50
end if

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

loo_Json.EmitCompact = 0

//  To verify DomainKey-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

    //  Note: DKIM-Signatures are much more common than DomainKey-Signature
    //  See DKIM-Signature Verify Sample.

    //  Get the number of DomainKey-Signature headers.
    li_NumSigs = loo_Dkim.NumDomainKeySigs(loo_MimeData)

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

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