PowerBuilder

Prefetch a DKIM Public Key from DNS

Demonstrates the Chilkat Dkim.PrefetchPublicKey method, which retrieves a DKIM public key from DNS and caches it for a specific selector and domain. The arguments are the selector and the domain. The TXT lookup is made at selector._domainkey.domain.

Background: DkimVerify already fetches the key from DNS on demand, so prefetching is about when the lookup happens: doing it up front lets you separate a potentially slow network step from the verification itself, warm the cache before a batch of messages from the same domain, or confirm the key is publishable before relying on it. After a successful prefetch, verification of a matching signature uses the cached key with no further DNS traffic.

Chilkat PowerBuilder Downloads

Download Chilkat for PowerBuilder

PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Dkim

li_Success = 0

//  Demonstrates the Dkim.PrefetchPublicKey method, which retrieves a DKIM public key from DNS and
//  caches it for a specific selector and domain.  The 1st argument is the selector and the 2nd is
//  the domain.

loo_Dkim = create oleobject
li_rc = loo_Dkim.ConnectToNewObject("Chilkat.Dkim")
if li_rc < 0 then
    destroy loo_Dkim
    MessageBox("Error","Connecting to COM object failed")
    return
end if

//  Retrieve the public key from the DNS TXT record at selector._domainkey.domain and cache it.
//  A later DkimVerify for the same selector and domain then uses the cached key.
li_Success = loo_Dkim.PrefetchPublicKey("myselector","example.com")
if li_Success = 0 then
    Write-Debug loo_Dkim.LastErrorText
    destroy loo_Dkim
    return
end if

Write-Debug "Public key prefetched from DNS and cached."


destroy loo_Dkim