Package com.mimecast.robin.signing

Class DkimSigningHelper

java.lang.Object

com.mimecast.robin.signing.DkimSigningHelper

public final class DkimSigningHelper
extends Object

Applies DKIM signatures to outbound RelaySession envelope files.

Every code path that enqueues an outbound message to the persistent relay queue must invoke applyDkimSignaturesIfEnabled(RelaySession) before enqueueing, so that the signature is baked into the file that the queue processor later delivers. Retries of a queued file therefore transmit the already-signed bytes unchanged.

There are two such call sites today:

• RelayMessage.deliver() — messages accepted over SMTP with an outbound Session.
• BotHelper.queueBotResponse() — bot-generated responses that construct an outbound session in-process rather than receiving one over SMTP.

Extracting this into a helper keeps the two paths from diverging (the bot path previously bypassed signing entirely, so bot replies went out unsigned).

Field Summary

Fields

Modifier and Type	Field	Description
private static final org.apache.logging.log4j.Logger	log

Constructor Summary

Constructors

Modifier	Constructor	Description
private	DkimSigningHelper()

Method Summary

Modifier and Type	Method	Description
static void	applyDkimSignaturesIfEnabled(RelaySession relaySession)	Signs each envelope file in the session (in place, on disk) with every configured (domain, selector) pair returned by DkimSigningLookup for the envelope's sender domain.
private static String	extractSenderDomain(String mail)	Extracts the domain part from an email address.
private static void	prependDkimSignatures(File emailFile, byte[] original, List<String> signatures)	Prepends DKIM-Signature headers to the email file.
private static String	readPrivateKey(String keyPath)	Reads a PKCS8 PEM private key file and returns the base64 content without PEM headers.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

log

private static final org.apache.logging.log4j.Logger log

Constructor Details

DkimSigningHelper

private DkimSigningHelper()

Method Details

applyDkimSignaturesIfEnabled

public static void applyDkimSignaturesIfEnabled(RelaySession relaySession)

Signs each envelope file in the session (in place, on disk) with every configured (domain, selector) pair returned by DkimSigningLookup for the envelope's sender domain. Idempotent per call: skips when DKIM signing is not enabled, when no signing key is configured, when the sender domain has no lookup rows, or when the envelope has no file.

Parameters:

relaySession - Session whose envelope files should be signed prior to enqueue.

readPrivateKey

private static String readPrivateKey(String keyPath)
                              throws IOException

Reads a PKCS8 PEM private key file and returns the base64 content without PEM headers.

Parameters:

keyPath - Path to the PEM key file.

Returns:

Base64 key content (no PEM headers/footers, single line).

Throws:

IOException - If the file cannot be read.

prependDkimSignatures

private static void prependDkimSignatures(File emailFile,
 byte[] original,
 List<String> signatures)
                                   throws IOException

Prepends DKIM-Signature headers to the email file.

Parameters:

emailFile - Email file to modify in place.

original - Original email content (already read from the file).

signatures - List of DKIM-Signature header values (already RFC 5322 folded by Rspamd).

Throws:

IOException - If the file cannot be written.

extractSenderDomain

private static String extractSenderDomain(String mail)

Extracts the domain part from an email address.

Parameters:

mail - Email address (e.g., "user@example.com").

Returns:

Domain, or null if no @ is present.