Verify DomainKey-Signature Headers in Downloaded Email

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoImap
    Handle hoDkim
    Boolean iBUid
    Integer iSeqNum
    Integer j
    Integer n
    Handle hoJson
    Variant vMimeData
    Handle hoMimeData
    Integer iNumSigs
    String sTemp1

    Move False To iSuccess

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

    Get Create (RefClass(cComChilkatImap)) To hoImap
    If (Not(IsComObjectCreated(hoImap))) Begin
        Send CreateComObject of hoImap
    End

    // Connect to an IMAP server, login, select mailbox..
    // Use TLS 
    Set ComSsl Of hoImap To True
    Set ComPort Of hoImap To 993
    Get ComConnect Of hoImap "imap.example.com" To iSuccess
    If (iSuccess = True) Begin
        Get ComLogin Of hoImap "myLogin" "myPassword" To iSuccess
        If (iSuccess = True) Begin
            Get ComSelectMailbox Of hoImap "Inbox" To iSuccess
        End

    End

    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoImap To sTemp1
        Showln sTemp1
        Procedure_Return
    End

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

    Get Create (RefClass(cComChilkatDkim)) To hoDkim
    If (Not(IsComObjectCreated(hoDkim))) Begin
        Send CreateComObject of hoDkim
    End

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

    // Download emails by sequence numbers (not UIDs).
    Move False To iBUid

    Get ComNumMessages Of hoImap To n
    If (n > 50) Begin
        Move 50 To n
    End

    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Set ComEmitCompact Of hoJson To False

    // To verify DomainKey-Signature headers, we need the exact unmodified MIME bytes of each email.
    Get Create (RefClass(cComChilkatBinData)) To hoMimeData
    If (Not(IsComObjectCreated(hoMimeData))) Begin
        Send CreateComObject of hoMimeData
    End
    Move 1 To iSeqNum
    While (iSeqNum <= n)
        // The FetchSingleBd method was introduced in v9.5.0.76
        Get pvComObject of hoMimeData to vMimeData
        Get ComFetchSingleBd Of hoImap iSeqNum iBUid vMimeData To iSuccess
        If (iSuccess <> True) Begin
            Get ComLastErrorText Of hoImap To sTemp1
            Showln sTemp1
            Procedure_Return
        End

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

        // Get the number of DomainKey-Signature headers.
        Get pvComObject of hoMimeData to vMimeData
        Get ComNumDomainKeySigs Of hoDkim vMimeData To iNumSigs

        // Verify each..
        Move 0 To j
        While (j < iNumSigs)
            Showln "------ DomainKey Signature " j

            Get pvComObject of hoMimeData to vMimeData
            Get ComDomainKeyVerify Of hoDkim j vMimeData To iSuccess
            If (iSuccess <> True) Begin
                Showln "Not valid."
                Get ComLastErrorText Of hoDkim To sTemp1
                Showln sTemp1
            End
            Else Begin
                Showln "valid."
            End

            // Show the additional information about the signature verification
            Get ComVerifyInfo Of hoDkim To sTemp1
            Get ComLoad Of hoJson sTemp1 To iSuccess
            Get ComEmit Of hoJson To sTemp1
            Showln sTemp1

            // 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"
            // 	}

            Move (j + 1) To j
        Loop

        Move (iSeqNum + 1) To iSeqNum
    Loop

    Get ComDisconnect Of hoImap To iSuccess


End_Procedure