fix(protect): egress redirect re-screening + redaction case-sensitivity + IPv6-ULA over-match

[patchstackdave]

Three correctness fixes in the protect response/egress phases, from a review of the output-filtering surface. All contained; no API changes.

1. Egress: redirects weren't re-screened (SSRF via open redirect)

The guarded fetch screened only the initial URL, then delegated to native redirect: 'follow' — so a response that 302-redirects to an internal address (e.g. http://169.254.169.254/) reached it unchecked. Now we follow redirects ourselves with redirect: 'manual', screening every hop. Body is buffered once so 307/308 can replay it; 303 (and 301/302 on POST) rewrite to a bodyless GET; Authorization/Cookie are stripped on cross-origin hops; capped at 20 redirects; fail-open on un-normalizable input.

(The true fetch/undici connection pin — vs. resolve-and-screen — remains the separate roadmap item.)

2. Response redaction was case-sensitive while detection is case-insensitive

contains/stripos detection lowercases both sides, but the redactor masked with a case-sensitive split(literal). So a contains: "SECRET" rule detected secret yet masked nothing — the leak was served in the clear while telemetry reported a redaction. Now masks case-insensitively (escaped literal → gi regex), and encode escapes the actual matched span.

3. isInternalHost fc/fd prefix over-matched hostnames

The IPv6 ULA (fc00::/7) check fired on any hostname starting with fc/fd — e.g. fcm.googleapis.com — blocking legitimate egress in block mode. Now requires an actual IPv6 (: present).

Tests

tests/protect/correctness-fixes.test.ts (5 new): IPv6-ULA vs. hostname classification, case-insensitive redaction, redirect-to-internal blocked, redirect-to-allowed followed. Full suite 600 passed; typecheck clean.

🤖 Generated with Claude Code

[coderbuds]

Comprehensive bug-fix with robust egress screening and thorough edge-case tests.

🎯 Quality: 100% Elite · 📦 Size: Medium

📈 This month: Your 49th PR — above team average · Averaging Excellent

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[patchstackdave]

/review