Wes Huber 6114ef0d6d fix(security): pin webhook delivery to the SSRF-validated IP (DNS rebinding) (#5147) ...

validate_webhook_url resolves the host to accept/reject, but the delivery
connect (httpx.AsyncClient.post) re-resolved independently — a DNS record
flipping between the two lookups (rebinding) could slip an internal IP
(127.0.0.1 / 169.254.169.254 / LAN) past the check and receive the signed
payload. The module docstring already flagged this as only a "partial
defense".

Resolve + validate once via _validated_public_ips, then pin the delivery
TCP connect to that approved IP with an async _PinnedAsyncTransport built
on the public httpcore/httpx APIs (mirrors the sync search-fetch pin from
#704). The URL, Host header, and TLS SNI are unchanged, so certificate
validation and vhost routing still target the original hostname; only the
socket destination is pinned.

Delivery now uses a per-request pinned client instead of one shared client,
so close() is a no-op kept for API compatibility. Adds end-to-end tests that
drive the real transport against loopback servers, proving the connect
follows the pin rather than re-resolving the URL host.

Fixes #5146

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

2026-07-04 17:03:38 +01:00

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