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>
Test-only refactor continuing #2523. Adds a shared import-state isolation helper with focused coverage and migrates two pilot tests that manually preserved sys.modules and parent package attributes.
Restores both sys.modules and parent src.database package state after the webhook SSRF tests import src.webhook_manager against the real database module. Fixes one focused #2580 CI-baseline pollution bucket.
The webhook URL guard's _ip_is_private() only checks a hardcoded
_PRIVATE_NETWORKS list, which misses several addresses that route
internally. validate_webhook_url() therefore ALLOWED:
- http://[::]/ (IPv6 unspecified, reaches localhost)
- http://[::ffff:127.0.0.1]/ (IPv4-mapped IPv6 loopback = 127.0.0.1)
- http://[::ffff:169.254.169.254]/ (IPv4-mapped cloud metadata endpoint)
The last one is the dangerous case: a webhook pointed at the mapped
169.254.169.254 can pull cloud instance credentials (SSRF -> credential
theft).
Harden _ip_is_private(): first unwrap IPv4-mapped IPv6 to its embedded IPv4
(addr.ipv4_mapped), then reject via the stdlib address properties
(is_private, is_loopback, is_link_local, is_reserved, is_multicast,
is_unspecified) in addition to the existing network list. Public addresses
still pass.
tests/test_webhook_ssrf_resilience.py asserts validate_webhook_url raises
for the three IPv6 bypasses plus 127.0.0.1 and 0.0.0.0, and still accepts a
public IP literal. The IPv6 cases fail before this change.
Wes Huber