Rebasing INFRA-107 onto main folded #95's pytest suite into this
branch's tests. The unified conftest loads the PO/WO handlers by file
path, and handler.py now does `from ses_auth import
authenticate_inbound_email` -- a bare sibling import that resolves in
the Lambda only because the runtime puts each function's own directory
on sys.path. The shared load_handler now adds that directory so the
handler tests import correctly alongside the sender-auth tests.
Refs: INFRA-107
The From header and any raw-MIME Authentication-Results copies are
attacker-forgeable, so a forged email to apm@int.seahaven.com or
amazon_po@int.seahaven.com could create or mutate a WO/PO (INFRA-107,
CRITICAL). Both S3-triggered email processors now authenticate the
sender against the Authentication-Results header SES itself prepends
at delivery: only the topmost header is consulted, its authserv-id
must be amazonses.com, and it must carry dkim=pass for a domain in
the per-pipeline ALLOWED_DKIM_DOMAINS env var (comma-separated, set
in CDK so ops can adjust without code changes).
Allowlists come from live traffic observed 2026-07-15 on both ingest
buckets: WO mail arrives via the apm@ Google Groups forward, which
re-signs as seahaven.com (the hxgnsmartcloud.com signature does not
survive the forward); PO mail passes for amazon.coupahost.com.
amazonses.com also passes on PO mail but is deliberately excluded --
every SES customer's outbound mail passes for it.
Every failure path (env var unset, header missing or unparseable,
verdict fail, unaligned domain) rejects the email: a structured
warning with the reason and S3 key is logged and the record skipped
without erroring the invocation, so rejected mail causes no Lambda
retries or DLQ messages. Handler signatures and event sources are
unchanged.
Refs: INFRA-107
The repo had no automated tests, so regressions in the email
parsing pipeline could only be caught manually. The reusable
ci-python-sam workflow already supports a run-tests input at the
pinned SHA; enable it and add a first suite covering the pure
functions pad_zip and parse_raw_email.
tests/conftest.py sets AWS_DEFAULT_REGION and dummy credentials
before any handler import because the handlers create boto3
clients at module import time, and loads each handler.py via
importlib under a unique module name since the files share a
basename. pytest.ini scopes discovery to tests/ so the manual
test_local.py script at the repo root is not collected.
