Unreleased Changes in The Mainline

Breaking Changes

• The rfc5321_rustls_config cache has been renamed to rustls_client_config. If you have a policy that tunes this cache via kumo.set_lruttl_cache_capacity, you will need to update the cache name.

Other Changes and Enhancements

• Enhanced Access Control subsystem, supported by a new Authentication, Authorization and Accounting (AAA) module exposed to lua as kumo.aaa.
• The Handlebars template dialect now runs with recursive lookup for improved compatibility with other handlebars implementations.
• msg:check_fix_conformance() can now detect and attempt to fix issues where the charset is invalid for parts that use transfer-encoding, by applying any charset detection options, falling back to UTF-8.
• The lua HTTP Request object now supports AWS V4 signatures via a new request:aws_sign_v4 method. Thanks to @AdityaAudi! #458
• The HTTP Injection API and MIME Builder API now support creating messages with AMP HTML parts. mimepart:get_simple_structure() also supports AMP HTML parts.
• Improved the context shown in error messages produced by the HTTP injection API
• Kumo Proxy:
  • Now optionally supports configuration via a proxy policy lua script.
  • Optional support for TLS and mutual TLS when using a proxy policy script, however, kumod itself doesn't currently support using TLS for SOCKS5.
  • Optional support for RFC 1929 authentication
  • Use kumo.start_proxy_listener function to configure a SOCKS5 proxy server
  • Many thanks to @vietcgi! #459
• New kumo.xfer.xfer function to enable per-message transfer between nodes, which is useful in combination with the requeue_message event.

Fixes

• An SPF record containing U+200B (zero width space) could cause SPF record parsing to panic and the service to crash
• MIME part body extraction did not always consider the charset for text parts
• Errors raised while dispatching should_enqueue_log_record were not logged to the diagnostic log.
• Rebuilding (eg: for conformance fixing via msg:check_fix_conformance(), or as part of the post-HTTP injection fixup) a header like From: "something\n\tthat wraps lines" <user@example.com> would produce an invalid rendition of that header.
• Setting content.headers["To"] in the HTTP injection API would result in two To headers being generated in the message; one for the per-recipient To header, and one for the specified content.headers["To"] value. This has been fixed; the behavior now is to use the content.headers["To"] header and not to emit a per-recipient To header in this situation.