🛡️ Sentinel: [HIGH] Fix Server-Side Request Forgery (SSRF) vulnerability

[mttmcknn]

• 🚨 Severity: HIGH
• 💡 Vulnerability: The plugin manager uses http.Get and standard http.Client for fetching plugins from URLs provided by the user, and does not restrict requests to sensitive local IPs like cloud metadata endpoints.
• 🎯 Impact: An attacker could coerce the application to send HTTP requests to sensitive internal networks, such as cloud metadata APIs (169.254.169.254), potentially exposing credentials or internal services.
• 🔧 Fix: Implemented newSafeClient which uses a custom net.Dialer with a Control hook to inspect the resolved IP address before connection and explicitly blocks access to 169.254.169.254. Replaced http.Get and standard http.Client usages with this safe client.
• ✅ Verification: Tested successfully with go test ./... and go build ./....

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PR created automatically by Jules for task 11926236194630636081 started by @himattm

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