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.
