feat(redact): add value-pattern redaction for JWTs and PEM blocks

src/record.ts

@@ -1,7 +1,7 @@
 import { spawn } from "node:child_process";
 import { createWriteStream } from "node:fs";
 import { lineFrames } from "./transport.js";
-import { redactDeep, DEFAULT_REDACT_PATTERNS } from "./redact.js";
+import { redactDeep, DEFAULT_REDACT_PATTERNS, redactValues, DEFAULT_REDACT_VALUE_PATTERNS } from "./redact.js";
 import type { Frame, JsonRpcMessage } from "./types.js";
 
 export interface RecordOptions {
@@ -69,7 +69,7 @@ function passthroughIn(
   childStdin.write(line + "\n");
   try {
     const msg = JSON.parse(line) as JsonRpcMessage;
-    const safe = redactDeep(msg, redact) as JsonRpcMessage;
+    const safe = redactValues(redactDeep(msg, redact), DEFAULT_REDACT_VALUE_PATTERNS) as JsonRpcMessage;
     append({ t: (Date.now() - start) / 1000, dir: "→", msg: safe });
   } catch {
     // not JSON - passed through, not recorded
@@ -85,7 +85,7 @@ function passthroughOut(
   process.stdout.write(line + "\n");
   try {
     const msg = JSON.parse(line) as JsonRpcMessage;
-    const safe = redactDeep(msg, redact) as JsonRpcMessage;
+    const safe = redactValues(redactDeep(msg, redact), DEFAULT_REDACT_VALUE_PATTERNS) as JsonRpcMessage;
     append({ t: (Date.now() - start) / 1000, dir: "←", msg: safe });
   } catch {
     // not JSON - passed through, not recorded

src/redact.ts

@@ -11,6 +11,18 @@ export const DEFAULT_REDACT_PATTERNS: string[] = [
   "*_secret",
 ];
 
+/**
+ * Value-content patterns applied automatically on every `record` run.
+ * Any string value (at any depth) whose content matches one of these
+ * patterns is replaced with `<REDACTED>` regardless of key name.
+ *
+ * Covers JWT bearer tokens (header starts with `eyJ`) and PEM blocks.
+ */
+export const DEFAULT_REDACT_VALUE_PATTERNS: RegExp[] = [
+  /^eyJ[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+$/,
+  /-----BEGIN [A-Z0-9 ]+-----/,
+];
+
 /**
  * Replace values whose keys match any of the given patterns with
  * `<REDACTED>`. Patterns may use `*` as a wildcard; matching is
@@ -50,3 +62,33 @@ function toRegex(pattern: string): RegExp {
   const withWild = escaped.replace(/\*/g, ".*");
   return new RegExp(`^${withWild}$`, "i");
 }
+
+/**
+ * Replace any string value (at any depth) that matches one of the
+ * given regexes with `<REDACTED>`. Key names are not inspected; only
+ * the content of string values is tested.
+ *
+ * Combine with `redactDeep` to get both key-name and value-content
+ * redaction: `redactValues(redactDeep(msg, keyPatterns), valuePatterns)`.
+ */
+export function redactValues(value: unknown, patterns: RegExp[]): unknown {
+  if (patterns.length === 0) return value;
+  return walkValues(value, patterns);
+}
+
+function walkValues(v: unknown, patterns: RegExp[]): unknown {
+  if (v === null || v === undefined) return v;
+  if (Array.isArray(v)) return v.map((x) => walkValues(x, patterns));
+  if (typeof v === "object") {
+    const obj = v as Record<string, unknown>;
+    const out: Record<string, unknown> = {};
+    for (const [k, val] of Object.entries(obj)) {
+      out[k] = walkValues(val, patterns);
+    }
+    return out;
+  }
+  if (typeof v === "string" && patterns.some((r) => r.test(v))) {
+    return "<REDACTED>";
+  }
+  return v;
+}

test/redact.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from "vitest";
-import { redactDeep, DEFAULT_REDACT_PATTERNS } from "../src/redact.js";
+import { redactDeep, DEFAULT_REDACT_PATTERNS, redactValues, DEFAULT_REDACT_VALUE_PATTERNS } from "../src/redact.js";
 
 describe("redactDeep", () => {
   it("redacts top-level keys", () => {
@@ -99,3 +99,73 @@ describe("DEFAULT_REDACT_PATTERNS", () => {
     ).toEqual({ method: "tools/call", q: "hello" });
   });
 });
+
+const TEST_JWT =
+  "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c2VyIn0.AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+const TEST_PEM =
+  "-----BEGIN PRIVATE KEY-----\nMIIEvgIBADANBgkqhkiG9w0BAQEFAASC\n-----END PRIVATE KEY-----";
+
+describe("redactValues", () => {
+  it("redacts a JWT-shaped string value", () => {
+    expect(redactValues({ bearer: TEST_JWT }, DEFAULT_REDACT_VALUE_PATTERNS)).toEqual({
+      bearer: "<REDACTED>",
+    });
+  });
+
+  it("redacts a PEM block value", () => {
+    expect(redactValues({ cert: TEST_PEM }, DEFAULT_REDACT_VALUE_PATTERNS)).toEqual({
+      cert: "<REDACTED>",
+    });
+  });
+
+  it("does not redact ordinary strings", () => {
+    expect(redactValues({ q: "hello world", n: 42 }, DEFAULT_REDACT_VALUE_PATTERNS)).toEqual({
+      q: "hello world",
+      n: 42,
+    });
+  });
+
+  it("redacts nested JWT values regardless of key name", () => {
+    expect(
+      redactValues({ params: { data: TEST_JWT } }, DEFAULT_REDACT_VALUE_PATTERNS),
+    ).toEqual({ params: { data: "<REDACTED>" } });
+  });
+
+  it("redacts JWT values inside arrays", () => {
+    expect(
+      redactValues([{ t: TEST_JWT }, { t: "plain" }], DEFAULT_REDACT_VALUE_PATTERNS),
+    ).toEqual([{ t: "<REDACTED>" }, { t: "plain" }]);
+  });
+
+  it("does nothing with empty patterns", () => {
+    expect(redactValues({ a: TEST_JWT }, [])).toEqual({ a: TEST_JWT });
+  });
+
+  it("does not redact a near-JWT (only two segments)", () => {
+    expect(
+      redactValues({ t: "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c2VyIn0" }, DEFAULT_REDACT_VALUE_PATTERNS),
+    ).toEqual({ t: "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c2VyIn0" });
+  });
+
+  it("redacts both JWT and PEM values in the same object", () => {
+    expect(
+      redactValues({ jwt: TEST_JWT, pem: TEST_PEM, safe: "ok" }, DEFAULT_REDACT_VALUE_PATTERNS),
+    ).toEqual({ jwt: "<REDACTED>", pem: "<REDACTED>", safe: "ok" });
+  });
+});
+
+describe("DEFAULT_REDACT_VALUE_PATTERNS", () => {
+  it("matches a JWT string", () => {
+    expect(DEFAULT_REDACT_VALUE_PATTERNS.some((r) => r.test(TEST_JWT))).toBe(true);
+  });
+
+  it("matches a PEM block", () => {
+    expect(DEFAULT_REDACT_VALUE_PATTERNS.some((r) => r.test(TEST_PEM))).toBe(true);
+  });
+
+  it("does not match a plain bearer token prefix without JWT structure", () => {
+    expect(
+      DEFAULT_REDACT_VALUE_PATTERNS.every((r) => !r.test("Bearer ghp_abc123")),
+    ).toBe(true);
+  });
+});