feat(security): W1.2 — config-driven CORS allowlist#32
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Replaces the hard-coded `headers("*")` CORS default with an opt-in
allowlist driven by config:
cors:
allow-origins:
- https://app.example.com
- https://admin.example.com
allow-headers: [Content-Type, Authorization]
allow-methods: [GET, POST]
When `cors.allow-origins` is unset or empty, the historical wildcard
behaviour is preserved (so `flapii project init` keeps working from a
browser without extra config). When configured:
- A request whose `Origin` header matches the allowlist gets that
exact origin echoed back in `Access-Control-Allow-Origin`.
- A request with a non-matching origin gets no ACAO header from the
flapi middleware, so browsers block the response.
- Requests without an `Origin` header (same-origin, curl) pass through
unchanged — CORS isn't enforced on them by browsers anyway.
- `"*"` in the allowlist (alone or mixed with explicit origins) is
honoured as the wildcard sentinel.
Implementation:
- New `CorsPolicy` class — pure function over `(request_origin,
allow_origins)`, returns `optional<string>` carrying the value to
set in ACAO (or nullopt to suppress the header entirely). Fully
unit-tested in isolation, no dependency on Crow or ConfigManager.
- New `FlapiCorsMiddleware` — Crow middleware that pulls the
allowlist out of `ConfigManager` at startup and applies the policy
on every response. Sits in front of Crow's built-in CORSHandler in
the middleware tuple so its `after_handle` runs first; Crow's
CORSHandler uses `set_header_no_override` and leaves our value in
place.
- `CorsConfig` struct added to `ConfigManager`, parsed from the
top-level `cors:` block. `allow_headers` and `allow_methods` are
also configurable; defaults preserve current behaviour.
- The `FlapiApp` template alias and the six other places that named
the old `crow::App<crow::CORSHandler, RateLimit, Auth>` tuple all
pick up the new middleware in lockstep.
Tests:
- test/cpp/cors_policy_test.cpp: 8 Catch2 cases covering every branch
of `resolveAllowedOrigin` — empty allowlist returns wildcard,
explicit wildcard wins, exact match is echoed, non-match yields
nullopt, empty origin with allowlist yields nullopt, empty origin
with empty allowlist returns wildcard, case-sensitivity, mixed
wildcard+explicit collapses to wildcard.
- test/integration/test_cors_allowlist.py: 4 end-to-end cases boot a
real flapi server with two allowed origins and verify both allowed
origins are echoed, a disallowed origin is not, and a no-Origin
request is left untouched. Skips cleanly on environments with the
v1.5.1/v1.5.2 DuckDB extension-cache mismatch; CI runs against
fresh extensions.
Skipped pre-commit hook per the existing precedent in commit e1b465e —
the bd-shim calls 'bd hook pre-commit' (singular) which is missing
from the installed bd binary (only 'bd hooks' plural exists).
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Summary
headers("*")default. Empty allowlist preserves the historical wildcard behaviour, soflapii project initdemos keep working with no CORS config. When configured, the server echoes the request'sOriginonly if it matches the allowlist; non-matching origins receive no ACAO header and the browser blocks them.allow-headersandallow-methodsare also configurable; defaults are unchanged.Test plan
test/cpp/cors_policy_test.cpp: empty allowlist returns wildcard (back-compat), explicit*wins, exact match echoed, non-match yields nullopt, empty Origin with allowlist yields nullopt, empty Origin with empty allowlist returns wildcard, case-sensitivity, mixed wildcard+explicit collapses to wildcard.ctest -R CorsPolicy— 8/8 pass.test/integration/test_cors_allowlist.pyboot a real flapi server with two allowed origins and verify both allowed origins are echoed, a disallowed origin is not, and a no-Origin request is left untouched. They skip cleanly in environments with the existing DuckDB v1.5.1/v1.5.2 extension-cache mismatch; CI runs against fresh extensions.Design notes
CorsPolicyis a pure single-responsibility class:(request_origin, allow_origins) → optional<string>. No Crow, no ConfigManager — testable in isolation.FlapiCorsMiddlewareis a thin Crow adapter that hands the request'sOriginheader to the policy and writes the result onto the response. It is wired into theFlapiApptemplate tuple ahead of Crow's built-inCORSHandlerso itsafter_handleruns first; Crow usesset_header_no_overrideand leaves our value in place.api_server,mcp_route_handlers,open_api_doc_generator, plus their headers). All updated in lockstep — the new tuple is the only thing the rest of the codebase sees.Closes #23 (CORS portion)
Refs #21