fix: harden web fetch SSRF and redirects

Co-authored-by: Eli <fogboots@users.noreply.github.com>

src/agents/tools/web-fetch.ssrf.test.ts

@@ -0,0 +1,160 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+const lookupMock = vi.fn();
+
+vi.mock("node:dns/promises", () => ({
+  lookup: lookupMock,
+}));
+
+function makeHeaders(map: Record<string, string>): { get: (key: string) => string | null } {
+  return {
+    get: (key) => map[key.toLowerCase()] ?? null,
+  };
+}
+
+function redirectResponse(location: string): Response {
+  return {
+    ok: false,
+    status: 302,
+    headers: makeHeaders({ location }),
+    body: { cancel: vi.fn() },
+  } as Response;
+}
+
+function textResponse(body: string): Response {
+  return {
+    ok: true,
+    status: 200,
+    headers: makeHeaders({ "content-type": "text/plain" }),
+    text: async () => body,
+  } as Response;
+}
+
+describe("web_fetch SSRF protection", () => {
+  const priorFetch = global.fetch;
+
+  afterEach(() => {
+    // @ts-expect-error restore
+    global.fetch = priorFetch;
+    lookupMock.mockReset();
+    vi.restoreAllMocks();
+  });
+
+  it("blocks localhost hostnames before fetch/firecrawl", async () => {
+    const fetchSpy = vi.fn();
+    // @ts-expect-error mock fetch
+    global.fetch = fetchSpy;
+
+    const { createWebFetchTool } = await import("./web-tools.js");
+    const tool = createWebFetchTool({
+      config: {
+        tools: {
+          web: {
+            fetch: {
+              cacheTtlMinutes: 0,
+              firecrawl: { apiKey: "firecrawl-test" },
+            },
+          },
+        },
+      },
+    });
+
+    await expect(tool?.execute?.("call", { url: "http://localhost/test" })).rejects.toThrow(
+      /Blocked hostname/i,
+    );
+    expect(fetchSpy).not.toHaveBeenCalled();
+    expect(lookupMock).not.toHaveBeenCalled();
+  });
+
+  it("blocks private IP literals without DNS", async () => {
+    const fetchSpy = vi.fn();
+    // @ts-expect-error mock fetch
+    global.fetch = fetchSpy;
+
+    const { createWebFetchTool } = await import("./web-tools.js");
+    const tool = createWebFetchTool({
+      config: {
+        tools: { web: { fetch: { cacheTtlMinutes: 0, firecrawl: { enabled: false } } } },
+      },
+    });
+
+    await expect(tool?.execute?.("call", { url: "http://127.0.0.1/test" })).rejects.toThrow(
+      /private|internal|blocked/i,
+    );
+    await expect(tool?.execute?.("call", { url: "http://[::ffff:127.0.0.1]/" })).rejects.toThrow(
+      /private|internal|blocked/i,
+    );
+    expect(fetchSpy).not.toHaveBeenCalled();
+    expect(lookupMock).not.toHaveBeenCalled();
+  });
+
+  it("blocks when DNS resolves to private addresses", async () => {
+    lookupMock.mockImplementation(async (hostname: string) => {
+      if (hostname === "public.test") {
+        return [{ address: "93.184.216.34", family: 4 }];
+      }
+      return [{ address: "10.0.0.5", family: 4 }];
+    });
+
+    const fetchSpy = vi.fn();
+    // @ts-expect-error mock fetch
+    global.fetch = fetchSpy;
+
+    const { createWebFetchTool } = await import("./web-tools.js");
+    const tool = createWebFetchTool({
+      config: {
+        tools: { web: { fetch: { cacheTtlMinutes: 0, firecrawl: { enabled: false } } } },
+      },
+    });
+
+    await expect(tool?.execute?.("call", { url: "https://private.test/resource" })).rejects.toThrow(
+      /private|internal|blocked/i,
+    );
+    expect(fetchSpy).not.toHaveBeenCalled();
+  });
+
+  it("blocks redirects to private hosts", async () => {
+    lookupMock.mockResolvedValue([{ address: "93.184.216.34", family: 4 }]);
+
+    const fetchSpy = vi.fn().mockResolvedValueOnce(redirectResponse("http://127.0.0.1/secret"));
+    // @ts-expect-error mock fetch
+    global.fetch = fetchSpy;
+
+    const { createWebFetchTool } = await import("./web-tools.js");
+    const tool = createWebFetchTool({
+      config: {
+        tools: {
+          web: {
+            fetch: { cacheTtlMinutes: 0, firecrawl: { apiKey: "firecrawl-test" } },
+          },
+        },
+      },
+    });
+
+    await expect(tool?.execute?.("call", { url: "https://example.com" })).rejects.toThrow(
+      /private|internal|blocked/i,
+    );
+    expect(fetchSpy).toHaveBeenCalledTimes(1);
+  });
+
+  it("allows public hosts", async () => {
+    lookupMock.mockResolvedValue([{ address: "93.184.216.34", family: 4 }]);
+
+    const fetchSpy = vi.fn().mockResolvedValue(textResponse("ok"));
+    // @ts-expect-error mock fetch
+    global.fetch = fetchSpy;
+
+    const { createWebFetchTool } = await import("./web-tools.js");
+    const tool = createWebFetchTool({
+      config: {
+        tools: { web: { fetch: { cacheTtlMinutes: 0, firecrawl: { enabled: false } } } },
+      },
+    });
+
+    const result = await tool?.execute?.("call", { url: "https://example.com" });
+    expect(result?.details).toMatchObject({
+      status: 200,
+      extractor: "raw",
+    });
+  });
+});