fix(server): redact sensitive env vars and headers from connection logs

Closes #847

Author: SarthakB11

server/package.json

@@ -24,7 +24,8 @@
     "build": "tsc && shx cp -R static build",
     "start": "node build/index.js",
     "dev": "tsx watch --clear-screen=false src/index.ts",
-    "dev:windows": "tsx watch --clear-screen=false src/index.ts < NUL"
+    "dev:windows": "tsx watch --clear-screen=false src/index.ts < NUL",
+    "test": "node --import tsx --test test/*.test.ts"
   },
   "devDependencies": {
     "@types/cors": "^2.8.19",

server/src/index.ts

@@ -28,6 +28,7 @@ import express from "express";
 import rateLimit from "express-rate-limit";
 import { findActualExecutable } from "spawn-rx";
 import mcpProxy, { type ProxyHeaderHolder } from "./mcpProxy.js";
+import { redactSensitiveEntries, redactQueryForLogging } from "./redact.js";
 import { randomUUID, randomBytes, timingSafeEqual } from "node:crypto";
 import { fileURLToPath } from "url";
 import { dirname, join } from "path";
@@ -430,7 +431,10 @@ const createTransport = async (
   headerHolder?: ProxyHeaderHolder;
 }> => {
   const query = req.query;
-  console.log("Query parameters:", JSON.stringify(query));
+  console.log(
+    "Query parameters:",
+    JSON.stringify(redactQueryForLogging(query)),
+  );
 
   const transportType = query.transportType as string;
 
@@ -461,7 +465,9 @@ const createTransport = async (
     const headerHolder: ProxyHeaderHolder = { headers };
 
     console.log(
-      `SSE transport: url=${url}, headers=${JSON.stringify(headers)}`,
+      `SSE transport: url=${url}, headers=${JSON.stringify(
+        redactSensitiveEntries(headers),
+      )}`,
     );
 
     const transport = new SSEClientTransport(new URL(url), {

server/src/redact.ts

@@ -0,0 +1,48 @@
+// Patterns matching env-var/header keys whose values may contain secrets.
+// When logging, we keep the key (so users can see what was passed) but
+// replace the value with `***` so tokens don't end up in stdout/log files.
+export const SENSITIVE_KEY_PATTERNS: RegExp[] = [
+  /token/i,
+  /secret/i,
+  /password/i,
+  /passwd/i,
+  /credential/i,
+  /api[-_]?key/i,
+  /(^|_)key($|_)/i,
+  /auth/i,
+  /session/i,
+  /private/i,
+  /^aws_/i,
+];
+
+export const REDACTED = "***";
+
+export const isSensitiveKey = (key: string): boolean =>
+  SENSITIVE_KEY_PATTERNS.some((re) => re.test(key));
+
+export const redactSensitiveEntries = (
+  obj: Record<string, unknown> | null | undefined,
+): Record<string, unknown> => {
+  if (!obj) return {};
+  const out: Record<string, unknown> = {};
+  for (const [k, v] of Object.entries(obj)) {
+    out[k] = isSensitiveKey(k) ? REDACTED : v;
+  }
+  return out;
+};
+
+// Returns a copy of an Express query object with the `env` JSON value
+// re-serialized with sensitive entries redacted, suitable for logging.
+export const redactQueryForLogging = (q: unknown): unknown => {
+  if (!q || typeof q !== "object") return q;
+  const out: Record<string, unknown> = { ...(q as Record<string, unknown>) };
+  if (typeof out.env === "string") {
+    try {
+      const parsed = JSON.parse(out.env);
+      out.env = redactSensitiveEntries(parsed);
+    } catch {
+      out.env = REDACTED;
+    }
+  }
+  return out;
+};

server/test/redact.test.ts

@@ -0,0 +1,69 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import {
+  redactSensitiveEntries,
+  redactQueryForLogging,
+} from "../src/redact.js";
+
+test("redactSensitiveEntries: redacts common secret-bearing env vars and keeps benign ones", () => {
+  const input = {
+    GITHUB_TOKEN: "ghp_xxx",
+    PATH: "/usr/bin",
+    AWS_ACCESS_KEY_ID: "AKIA...",
+  };
+  assert.deepEqual(redactSensitiveEntries(input), {
+    GITHUB_TOKEN: "***",
+    PATH: "/usr/bin",
+    AWS_ACCESS_KEY_ID: "***",
+  });
+});
+
+test("redactSensitiveEntries: bare KEY and API_KEY are redacted", () => {
+  assert.deepEqual(redactSensitiveEntries({ KEY: "k" }), { KEY: "***" });
+  assert.deepEqual(redactSensitiveEntries({ API_KEY: "k" }), {
+    API_KEY: "***",
+  });
+  assert.deepEqual(redactSensitiveEntries({ "api-key": "k" }), {
+    "api-key": "***",
+  });
+});
+
+test("redactSensitiveEntries: word containing 'key' is NOT redacted (boundary)", () => {
+  // The boundary in /(^|_)key($|_)/i prevents naive substring matches like
+  // MONKEY, KEYBOARD, etc. from being flagged as secrets.
+  assert.deepEqual(redactSensitiveEntries({ MONKEY: "m" }), { MONKEY: "m" });
+  assert.deepEqual(redactSensitiveEntries({ KEYBOARD: "k" }), {
+    KEYBOARD: "k",
+  });
+});
+
+test("redactSensitiveEntries: Authorization header is redacted", () => {
+  assert.deepEqual(redactSensitiveEntries({ Authorization: "Bearer x" }), {
+    Authorization: "***",
+  });
+});
+
+test("redactQueryForLogging: env JSON is parsed and redacted entry-by-entry", () => {
+  const env = JSON.stringify({ PASSWORD: "p", PORT: "5432" });
+  const out = redactQueryForLogging({ env, transport: "stdio" }) as Record<
+    string,
+    unknown
+  >;
+  assert.deepEqual(out.env, { PASSWORD: "***", PORT: "5432" });
+  assert.equal(out.transport, "stdio");
+});
+
+test("redactQueryForLogging: malformed env falls back to ***", () => {
+  const out = redactQueryForLogging({ env: "not-json" }) as Record<
+    string,
+    unknown
+  >;
+  assert.equal(out.env, "***");
+});
+
+test("redactQueryForLogging: missing env passes through unchanged", () => {
+  assert.deepEqual(redactQueryForLogging({ transport: "sse" }), {
+    transport: "sse",
+  });
+});