Verify DomainKey-Signature Headers in Downloaded Email

Dim success As Boolean = False

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

Dim imap As ChilkatImap
imap.Initialize("imap")

'  Connect to an IMAP server, login, select mailbox..
'  Use TLS 
imap.Ssl = True
imap.Port = 993
success = imap.Connect("imap.example.com")
If success = True Then
    success = imap.Login("myLogin", "myPassword")
    If success = True Then
        success = imap.SelectMailbox("Inbox")
    End If

End If

If success <> True Then
    Log(imap.LastErrorText)
    Return
End If


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

Dim dkim As ChilkatDkim
dkim.Initialize("dkim")

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

'  Download emails by sequence numbers (not UIDs).
Dim bUid As Boolean = False
Dim seqNum As Int
Dim j As Int
Dim n As Int = imap.NumMessages
If n > 50 Then
    n = 50
End If


Dim json As ChilkatJsonObject
json.Initialize
json.EmitCompact = False

'  To verify DomainKey-Signature headers, we need the exact unmodified MIME bytes of each email.
Dim mimeData As ChilkatBinData
mimeData.Initialize
seqNum = 1
Do While seqNum <= n
    '  The FetchSingleBd method was introduced in v9.5.0.76
    success = imap.FetchSingleBd(seqNum, bUid, mimeData)
    If success <> True Then
        Log(imap.LastErrorText)
        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.
    Dim numSigs As Int = dkim.NumDomainKeySigs(mimeData)

    '  Verify each..
    j = 0
    Do While j < numSigs
        Log("------ DomainKey Signature " & j)

        success = dkim.DomainKeyVerify(j, mimeData)
        If success <> True Then
            Log("Not valid.")
            Log(dkim.LastErrorText)
        Else
            Log("valid.")
        End If


        '  Show the additional information about the signature verification
        json.Load(dkim.VerifyInfo)
        Log(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
    seqNum = seqNum + 1
Loop

success = imap.Disconnect