feat(email): add Message_Id_Util for RFC 5322 threading + signed Reply-To#31
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feat(email): add Message_Id_Util for RFC 5322 threading + signed Reply-To#31
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Ports the NestJS email/message-id.ts helpers to WordPress. Coexists
with the existing Email_Threading class during the migration window —
new outbound paths should prefer this util so inbound Reply-To
verification has something to check against.
API:
build_message_id(ticket_id, reply_id, domain)
parse_ticket_id_from_message_id(raw)
build_reply_to(ticket_id, secret, domain)
verify_reply_to(address, secret)
Uses hash_hmac('sha256', ...) + hash_equals for timing-safe verification.
Pure functions, no WP test harness — 13 unit tests covering round-trip,
tamper rejection, case-insensitive hex, malformed input, and the
local-part-only acceptance path.
This was referenced Apr 24, 2026
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Summary
Ports the NestJS
email/message-id.tshelpers to WordPress. Coexists with the existingEmail_Threadingclass during the migration window — new outbound paths should prefer this util so inbound Reply-To verification has something to check against.API
build_message_id(ticket_id, reply_id, domain)parse_ticket_id_from_message_id(raw)build_reply_to(ticket_id, secret, domain)verify_reply_to(address, secret)Uses
hash_hmac('sha256', ...)+hash_equalsfor timing-safe verification.Why signed Reply-To
The 8-char HMAC-SHA256 prefix on the Reply-To local part means even clients that strip our Message-ID / In-Reply-To headers still route replies back to the right ticket — the inbound provider webhook can verify the prefix before routing.
Design divergence note
The existing
Email_Threadingclass emits Message-IDs in a different shape:reply-{id}-ticket-{reference}@{domain}(usesreference, notid). This util uses the NestJS-compatible shape. Follow-up PR will migrateEmail_Threadingso inbound routing can use a single format.Test plan
test (8.1),test (8.2),lint