fix(tlon): address security review issues

- Fix SSRF in upload.ts: use urbitFetch with SSRF protection
- Fix SSRF in media.ts: use urbitFetch with SSRF protection
- Add command whitelist to tlon tool to prevent command injection
- Add getDefaultSsrFPolicy() helper for uploads/downloads

extensions/tlon/index.ts

@@ -9,6 +9,21 @@ import { setTlonRuntime } from "./src/runtime.js";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
+// Whitelist of allowed tlon subcommands
+const ALLOWED_TLON_COMMANDS = new Set([
+  "activity",
+  "channels",
+  "contacts",
+  "groups",
+  "messages",
+  "dms",
+  "posts",
+  "notebook",
+  "settings",
+  "help",
+  "version",
+]);
+
 /**
  * Find the tlon binary from the skill package
  */
@@ -141,6 +156,21 @@ const plugin = {
       async execute(_id: string, params: { command: string }) {
         try {
           const args = shellSplit(params.command);
+
+          // Validate first argument is a whitelisted tlon subcommand
+          const subcommand = args[0];
+          if (!ALLOWED_TLON_COMMANDS.has(subcommand)) {
+            return {
+              content: [
+                {
+                  type: "text" as const,
+                  text: `Error: Unknown tlon subcommand '${subcommand}'. Allowed: ${[...ALLOWED_TLON_COMMANDS].join(", ")}`,
+                },
+              ],
+              details: { error: true },
+            };
+          }
+
           const output = await runTlonCommand(tlonBinary, args);
           return {
             content: [{ type: "text" as const, text: output }],

extensions/tlon/src/monitor/media.ts

@@ -5,6 +5,8 @@ import { homedir } from "node:os";
 import * as path from "node:path";
 import { Readable } from "node:stream";
 import { pipeline } from "node:stream/promises";
+import { getDefaultSsrFPolicy } from "../urbit/context.js";
+import { urbitFetch } from "../urbit/fetch.js";
 
 // Default to OpenClaw workspace media directory
 const DEFAULT_MEDIA_DIR = path.join(homedir(), ".openclaw", "workspace", "media", "inbound");
@@ -52,11 +54,25 @@ export async function downloadMedia(
   mediaDir: string = DEFAULT_MEDIA_DIR,
 ): Promise<DownloadedMedia | null> {
   try {
+    // Validate URL is http/https before fetching
+    const parsedUrl = new URL(url);
+    if (parsedUrl.protocol !== "http:" && parsedUrl.protocol !== "https:") {
+      console.warn(`[tlon-media] Rejected non-http(s) URL: ${url}`);
+      return null;
+    }
+
     // Ensure media directory exists
     await mkdir(mediaDir, { recursive: true });
 
-    // Fetch the image
-    const response = await fetch(url);
+    // Fetch with SSRF protection
+    const { response } = await urbitFetch({
+      baseUrl: url,
+      path: "",
+      init: { method: "GET" },
+      ssrfPolicy: getDefaultSsrFPolicy(),
+      auditContext: "tlon-media-download",
+    });
+
     if (!response.ok) {
       console.error(`[tlon-media] Failed to fetch ${url}: ${response.status}`);
       return null;

extensions/tlon/src/urbit/context.ts

@@ -45,3 +45,12 @@ export function ssrfPolicyFromAllowPrivateNetwork(
 ): SsrFPolicy | undefined {
   return allowPrivateNetwork ? { allowPrivateNetwork: true } : undefined;
 }
+
+/**
+ * Get the default SSRF policy for image uploads.
+ * Uses a restrictive policy that blocks private networks by default.
+ */
+export function getDefaultSsrFPolicy(): SsrFPolicy | undefined {
+  // Default: block private networks for image uploads (safer default)
+  return undefined;
+}

extensions/tlon/src/urbit/upload.ts

@@ -2,6 +2,8 @@
  * Upload an image from a URL to Tlon storage.
  */
 import { uploadFile } from "@tloncorp/api";
+import { getDefaultSsrFPolicy } from "./context.js";
+import { urbitFetch } from "./fetch.js";
 
 /**
  * Fetch an image from a URL and upload it to Tlon storage.
@@ -11,8 +13,22 @@ import { uploadFile } from "@tloncorp/api";
  */
 export async function uploadImageFromUrl(imageUrl: string): Promise<string> {
   try {
-    // Fetch the image
-    const response = await fetch(imageUrl);
+    // Validate URL is http/https before fetching
+    const url = new URL(imageUrl);
+    if (url.protocol !== "http:" && url.protocol !== "https:") {
+      console.warn(`[tlon] Rejected non-http(s) URL: ${imageUrl}`);
+      return imageUrl;
+    }
+
+    // Fetch the image with SSRF protection
+    const { response } = await urbitFetch({
+      baseUrl: imageUrl,
+      path: "",
+      init: { method: "GET" },
+      ssrfPolicy: getDefaultSsrFPolicy(),
+      auditContext: "tlon-upload-image",
+    });
+
     if (!response.ok) {
       console.warn(`[tlon] Failed to fetch image from ${imageUrl}: ${response.status}`);
       return imageUrl;