feat(protect): DNS-rebinding resistance for egress (Node http path) - #89
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DNS-rebinding guard is well-designed and thoroughly tested. 🎯 Quality: 100% Elite · 📦 Size: Medium 📈 This month: Your 38th PR — above team average · Averaging Excellent |
The egress guard screened outbound calls by hostname, so a name that passes the check but resolves to an internal/metadata IP (DNS rebinding, or just a hostname pointing inward) slipped through. On the Node http/https path, inject a screening DNS `lookup` into the request options: resolve the hostname, run each resolved address through the same egress predicate (so `internal_host` rules + allowlist apply to the IP too), block if any is disallowed, and pin the connection to the vetted resolution — closing the time-of-check/time-of-use gap. Only for real hostnames (literal IPs are already covered by the sync check). Default on via `screenDns` (disable with `screenDns: false`); needs node:dns/net, so it's a no-op on edge runtimes, where hostname rules still apply. Fail-open: a resolver or injection error proceeds unscreened rather than breaking the request. `lookup` is injectable for tests. The fetch/undici path is intentionally left for a follow-up. +5 tests, 495 total, typecheck (incl. template check) + build clean. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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mariojgt
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Jul 16, 2026
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The egress guard screened outbound calls by hostname, so a name that passes the check but resolves to an internal/metadata IP (DNS rebinding, or just a hostname pointing inward) slipped through.
On the Node http/https path, inject a screening DNS
lookupinto the request options:internal_hostrules + the allowlist apply to the resolved IP too),Only for real hostnames (literal IPs already covered by the sync check). Default on via
screenDns(disable withscreenDns: false); needsnode:dns/net, so it's a no-op on edge runtimes (hostname rules still apply). Fail-open: a resolver/injection error proceeds unscreened rather than breaking the request. The resolver is injectable for tests.The fetch/undici path is intentionally deferred (the fiddly part — needs a custom dispatcher to pin) — this is the easy, complete Node-path fix.
+5 tests. 495 pass, typecheck (incl. template check) + build clean.