Unicode C

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. Unicode C

#include <C_CkImapW.h>
#include <C_CkDkimW.h>
#include <C_CkJsonObjectW.h>
#include <C_CkBinDataW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkImapW imap;
    HCkDkimW dkim;
    BOOL bUid;
    int seqNum;
    int j;
    int n;
    HCkJsonObjectW json;
    HCkBinDataW mimeData;
    int numDkim;

    success = FALSE;

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

    imap = CkImapW_Create();

    // Connect to an IMAP server, login, select mailbox..
    // Use TLS 
    CkImapW_putSsl(imap,TRUE);
    CkImapW_putPort(imap,993);
    success = CkImapW_Connect(imap,L"imap.example.com");
    if (success == TRUE) {
        success = CkImapW_Login(imap,L"myLogin",L"myPassword");
        if (success == TRUE) {
            success = CkImapW_SelectMailbox(imap,L"Inbox");
        }

    }

    if (success != TRUE) {
        wprintf(L"%s\n",CkImapW_lastErrorText(imap));
        CkImapW_Dispose(imap);
        return;
    }

    dkim = CkDkimW_Create();

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

    // Download emails by sequence numbers (not UIDs).
    bUid = FALSE;

    n = CkImapW_getNumMessages(imap);
    if (n > 10) {
        n = 10;
    }

    json = CkJsonObjectW_Create();
    CkJsonObjectW_putEmitCompact(json,FALSE);

    // To verify DKIM-Signature headers, we need the exact unmodified MIME bytes of each email.
    mimeData = CkBinDataW_Create();
    seqNum = 1;
    while (seqNum <= n) {
        // The FetchSingleBd method was introduced in v9.5.0.76
        success = CkImapW_FetchSingleBd(imap,seqNum,bUid,mimeData);
        if (success != TRUE) {
            wprintf(L"%s\n",CkImapW_lastErrorText(imap));
            CkImapW_Dispose(imap);
            CkDkimW_Dispose(dkim);
            CkJsonObjectW_Dispose(json);
            CkBinDataW_Dispose(mimeData);
            return;
        }

        // Get the number of DKIM-Signature headers.
        numDkim = CkDkimW_NumDkimSigs(dkim,mimeData);

        // Verify each..
        j = 0;
        while (j < numDkim) {
            wprintf(L"------ DKIM Signature %d\n",j);

            success = CkDkimW_DkimVerify(dkim,j,mimeData);
            if (success != TRUE) {
                wprintf(L"Not valid.\n");
            }
            else {
                wprintf(L"valid.\n");
            }

            // Show the additional information about the signature verification
            CkJsonObjectW_Load(json,CkDkimW_verifyInfo(dkim));
            wprintf(L"%s\n",CkJsonObjectW_emit(json));

            // 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;
        }

        seqNum = seqNum + 1;
    }

    success = CkImapW_Disconnect(imap);


    CkImapW_Dispose(imap);
    CkDkimW_Dispose(dkim);
    CkJsonObjectW_Dispose(json);
    CkBinDataW_Dispose(mimeData);

    }