fix(security): sanitize error messages to prevent token leakage

Error messages from adapter auth/send failures may contain token
fragments. Added sanitizeError() that strips Slack token patterns
(xoxb-, xoxp-, xoxa-) and long opaque secrets (20+ alphanumeric
chars). Also truncates verbose Discord API error responses to 200
chars. Applied to all error paths in manager.ts and discord-adapter.ts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/resources/extensions/gsd/tests/remote-questions.test.ts

@@ -2,6 +2,7 @@ import test from "node:test";
 import assert from "node:assert/strict";
 import { parseSlackReply, parseDiscordResponse } from "../../remote-questions/format.ts";
 import { resolveRemoteConfig, isValidChannelId } from "../../remote-questions/config.ts";
+import { sanitizeError } from "../../remote-questions/manager.ts";
 
 test("parseSlackReply handles single-number single-question answers", () => {
   const result = parseSlackReply("2", [{
@@ -131,3 +132,24 @@ test("isValidChannelId rejects invalid Discord channel IDs", () => {
   assert.equal(isValidChannelId("discord", "11234567890123456789"), true);
 });
 
+test("sanitizeError strips Slack token patterns from error messages", () => {
+  assert.equal(
+    sanitizeError("Auth failed: xoxb-1234-5678-abcdef"),
+    "Auth failed: [REDACTED]",
+  );
+  assert.equal(
+    sanitizeError("Bad token xoxp-abc-def-ghi in request"),
+    "Bad token [REDACTED] in request",
+  );
+});
+
+test("sanitizeError strips long opaque secrets", () => {
+  const fakeDiscordToken = "MTIzNDU2Nzg5MDEyMzQ1Njc4OQ.G1x2y3.abcdefghijklmnop";
+  assert.ok(!sanitizeError(`Token: ${fakeDiscordToken}`).includes(fakeDiscordToken));
+});
+
+test("sanitizeError preserves short safe messages", () => {
+  assert.equal(sanitizeError("HTTP 401: Unauthorized"), "HTTP 401: Unauthorized");
+  assert.equal(sanitizeError("Connection refused"), "Connection refused");
+});
+

src/resources/extensions/remote-questions/discord-adapter.ts

@@ -114,7 +114,9 @@ export class DiscordAdapter implements ChannelAdapter {
     if (response.status === 204) return {};
     if (!response.ok) {
       const text = await response.text().catch(() => "");
-      throw new Error(`Discord API HTTP ${response.status}: ${text}`);
+      // Limit error body length to avoid leaking verbose Discord error responses
+      const safeText = text.length > 200 ? text.slice(0, 200) + "…" : text;
+      throw new Error(`Discord API HTTP ${response.status}: ${safeText}`);
     }
     return response.json();
   }

src/resources/extensions/remote-questions/manager.ts

@@ -36,7 +36,7 @@ export async function tryRemoteQuestions(
   try {
     await adapter.validate();
   } catch (err) {
-    markPromptStatus(prompt.id, "failed", String((err as Error).message));
+    markPromptStatus(prompt.id, "failed", sanitizeError(String((err as Error).message)));
     return errorResult(`Remote auth failed (${config.channel}): ${(err as Error).message}`, config.channel);
   }
 
@@ -45,7 +45,7 @@ export async function tryRemoteQuestions(
     dispatch = await adapter.sendPrompt(prompt);
     markPromptDispatched(prompt.id, dispatch.ref);
   } catch (err) {
-    markPromptStatus(prompt.id, "failed", String((err as Error).message));
+    markPromptStatus(prompt.id, "failed", sanitizeError(String((err as Error).message)));
     return errorResult(`Failed to send questions via ${config.channel}: ${(err as Error).message}`, config.channel);
   }
 
@@ -128,7 +128,7 @@ async function pollUntilDone(
       updatePromptRecord(prompt.id, { lastPollAt: Date.now() });
       if (answer) return answer;
     } catch (err) {
-      markPromptStatus(prompt.id, "failed", String((err as Error).message));
+      markPromptStatus(prompt.id, "failed", sanitizeError(String((err as Error).message)));
       return null;
     }
 
@@ -163,9 +163,25 @@ function formatForTool(answer: RemoteAnswer): Record<string, { answers: string[]
   return out;
 }
 
+// Strip token-like strings from error messages before surfacing
+const TOKEN_PATTERNS = [
+  /xoxb-[A-Za-z0-9\-]+/g,    // Slack bot tokens
+  /xoxp-[A-Za-z0-9\-]+/g,    // Slack user tokens
+  /xoxa-[A-Za-z0-9\-]+/g,    // Slack app tokens
+  /[A-Za-z0-9_\-.]{20,}/g,   // Long opaque secrets (Discord tokens, etc.)
+];
+
+export function sanitizeError(msg: string): string {
+  let sanitized = msg;
+  for (const pattern of TOKEN_PATTERNS) {
+    sanitized = sanitized.replace(pattern, "[REDACTED]");
+  }
+  return sanitized;
+}
+
 function errorResult(message: string, channel: string): ToolResult {
   return {
-    content: [{ type: "text", text: message }],
+    content: [{ type: "text", text: sanitizeError(message) }],
     details: { remote: true, channel, error: true, status: "failed" },
   };
 }