🛡️ Sentinel: [CRITICAL] Fix SSRF vulnerability in web_fetch tool

[mudcube]

🚨 Severity: CRITICAL
💡 Vulnerability: The web_fetch tool used reqwest::blocking::get without validating the resolved IP address, which allows an attacker to make requests to internal services or private IP addresses via Server-Side Request Forgery (SSRF).
🎯 Impact: Attackers could access internal services, read sensitive metadata endpoints (e.g., AWS IMDS), or scan internal networks.
🔧 Fix: Implemented an IP pinning mechanism with manual redirect tracking. Created a custom is_allowed_ip helper to block loopback, private, unspecified, multicast, broadcast, and link-local IPs. Configured the reqwest client to disable automatic redirects and used ClientBuilder::resolve() to pin the manually validated IP for each hop, preventing TOCTOU DNS rebinding without breaking SNI.
✅ Verification: Ran cargo check -p mill-plugin-system and cargo test -p mill-plugin-system.

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PR created automatically by Jules for task 11692208846023727398 started by @mudcube

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[chatgpt-codex-connector]

Block non-global IPv4 ranges in SSRF filter

This fallback allows any IPv4 address that is not RFC1918/loopback/link-local/multicast/broadcast, so web_fetch still accepts non-global ranges such as 100.64.0.0/10 and 198.18.0.0/15. In environments that place internal services on shared-address or benchmarking ranges, an attacker-controlled hostname resolving there will pass validation and the pinned request will still SSRF those internal endpoints; the filter should reject all non-global/special-use IPv4 ranges rather than returning true here.

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