fix: block ISATAP SSRF bypass via shared host/ip guard

src/infra/net/ssrf.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from "vitest";
 import { normalizeFingerprint } from "../tls/fingerprint.js";
-import { isPrivateIpAddress } from "./ssrf.js";
+import { isBlockedHostnameOrIp, isPrivateIpAddress } from "./ssrf.js";
 
 const privateIpCases = [
   "::ffff:127.0.0.1",
@@ -24,6 +24,8 @@ const privateIpCases = [
   "fe80::1%lo0",
   "fd00::1",
   "fec0::1",
+  "2001:db8:1234::5efe:127.0.0.1",
+  "2001:db8:1234:1:200:5efe:7f00:1",
 ];
 
 const publicIpCases = [
@@ -34,6 +36,8 @@ const publicIpCases = [
   "64:ff9b:1::8.8.8.8",
   "2002:0808:0808::",
   "2001:0000:0:0:0:0:f7f7:f7f7",
+  "2001:db8:1234::5efe:8.8.8.8",
+  "2001:db8:1234:1:1111:5efe:7f00:1",
 ];
 
 const malformedIpv6Cases = ["::::", "2001:db8::gggg"];
@@ -59,3 +63,15 @@ describe("normalizeFingerprint", () => {
     expect(normalizeFingerprint("aa:bb:cc")).toBe("aabbcc");
   });
 });
+
+describe("isBlockedHostnameOrIp", () => {
+  it("blocks localhost.localdomain and metadata hostname aliases", () => {
+    expect(isBlockedHostnameOrIp("localhost.localdomain")).toBe(true);
+    expect(isBlockedHostnameOrIp("metadata.google.internal")).toBe(true);
+  });
+
+  it("blocks private transition addresses via shared IP classifier", () => {
+    expect(isBlockedHostnameOrIp("2001:db8:1234::5efe:127.0.0.1")).toBe(true);
+    expect(isBlockedHostnameOrIp("2001:db8::1")).toBe(false);
+  });
+});

src/infra/net/ssrf.ts

@@ -24,7 +24,11 @@ export type SsrFPolicy = {
   hostnameAllowlist?: string[];
 };
 
-const BLOCKED_HOSTNAMES = new Set(["localhost", "metadata.google.internal"]);
+const BLOCKED_HOSTNAMES = new Set([
+  "localhost",
+  "localhost.localdomain",
+  "metadata.google.internal",
+]);
 
 function normalizeHostnameSet(values?: string[]): Set<string> {
   if (!values || values.length === 0) {
@@ -195,6 +199,12 @@ const EMBEDDED_IPV4_RULES: EmbeddedIpv4Rule[] = [
     matches: (hextets) => hextets[0] === 0x2001 && hextets[1] === 0x0000,
     extract: (hextets) => [hextets[6] ^ 0xffff, hextets[7] ^ 0xffff],
   },
+  {
+    // ISATAP IID format: 000000ug00000000:5efe:w.x.y.z (RFC 5214 section 6.1).
+    // Match only the IID marker bits to avoid over-broad :5efe: detection.
+    matches: (hextets) => (hextets[4] & 0xfcff) === 0 && hextets[5] === 0x5efe,
+    extract: (hextets) => [hextets[6], hextets[7]],
+  },
 ];
 
 function extractIpv4FromEmbeddedIpv6(hextets: number[]): number[] | null {
@@ -316,6 +326,14 @@ export function isBlockedHostname(hostname: string): boolean {
   );
 }
 
+export function isBlockedHostnameOrIp(hostname: string): boolean {
+  const normalized = normalizeHostname(hostname);
+  if (!normalized) {
+    return false;
+  }
+  return isBlockedHostname(normalized) || isPrivateIpAddress(normalized);
+}
+
 export function createPinnedLookup(params: {
   hostname: string;
   addresses: string[];