a

internal/dkim/dkim.go

@@ -327,13 +327,18 @@ func Verify(message []byte) (domain string, err error) {
 }
 
 // DNSRecord returns the DKIM TXT record string for publishing.
-func DNSRecord(selector, domain, publicKeyPEM string) string {
+// algo must be "rsa2048" or "ed25519"; any other value defaults to "rsa".
+func DNSRecord(selector, domain, publicKeyPEM, algo string) string {
 	block, _ := pem.Decode([]byte(publicKeyPEM))
 	var p string
 	if block != nil {
 		p = base64.StdEncoding.EncodeToString(block.Bytes)
 	}
-	return fmt.Sprintf("%s._domainkey.%s. IN TXT \"v=DKIM1; k=rsa; p=%s\"", selector, domain, p)
+	k := "rsa"
+	if algo == "ed25519" {
+		k = "ed25519"
+	}
+	return fmt.Sprintf("%s._domainkey.%s. IN TXT \"v=DKIM1; k=%s; p=%s\"", selector, domain, k, p)
 }
 
 // SPFRecord returns the recommended SPF TXT record for a domain.