Harden persisted authentication recovery

Treat malformed authentication records as missing so browser sign-in can recover, preserve real file-read failures, and pin the Azure Identity persistence dependencies exactly.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

extensions/connector-namespaces/auth.mjs

@@ -28,14 +28,23 @@ let legacyAuthCacheRemoved = false;
 
 useIdentityPlugin(cachePersistencePlugin);
 
-async function loadAuthenticationRecord() {
+export async function loadAuthenticationRecord({
+    readFile = fs.readFile,
+    deserialize = deserializeAuthenticationRecord,
+    authRecordFile = AUTH_RECORD_FILE,
+} = {}) {
+    let serialized;
     try {
-        const serialized = await fs.readFile(AUTH_RECORD_FILE, "utf-8");
-        return deserializeAuthenticationRecord(serialized);
+        serialized = await readFile(authRecordFile, "utf-8");
     } catch (error) {
         if (error?.code === "ENOENT") return undefined;
         throw error;
     }
+    try {
+        return deserialize(serialized);
+    } catch {
+        return undefined;
+    }
 }
 
 async function saveAuthenticationRecord(record) {

extensions/connector-namespaces/auth.test.mjs

@@ -4,6 +4,7 @@ import assert from "node:assert/strict";
 import {
     ConnectorAuthenticationRequiredError,
     InteractiveAuthBroker,
+    loadAuthenticationRecord,
     TOKEN_CACHE_NAME,
 } from "./auth.mjs";
 
@@ -36,6 +37,7 @@ test("ARM token requests require an explicit browser sign-in", async () => {
         },
         loadAuthRecord: async () => undefined,
     });
+
     await assert.rejects(
         broker.getToken(),
         (error) => error instanceof ConnectorAuthenticationRequiredError
@@ -47,6 +49,25 @@ test("ARM token requests require an explicit browser sign-in", async () => {
     });
 });
 
+test("a malformed authentication record falls back to browser sign-in", async () => {
+    assert.equal(
+        await loadAuthenticationRecord({
+            readFile: async () => "{malformed-json",
+        }),
+        undefined,
+    );
+});
+
+test("authentication record read failures remain operational errors", async () => {
+    const readError = Object.assign(new Error("authentication record is unreadable"), { code: "EACCES" });
+    await assert.rejects(
+        loadAuthenticationRecord({
+            readFile: async () => { throw readError; },
+        }),
+        (error) => error === readError,
+    );
+});
+
 test("interactive sign-in reports pending then done and caches the ARM token", async () => {
     let credentialOptions;
     let authenticateOptions;

extensions/connector-namespaces/package.json

@@ -14,8 +14,8 @@
   ],
   "license": "MIT",
   "dependencies": {
-    "@azure/identity": "^4.13.1",
-    "@azure/identity-cache-persistence": "^1.3.0",
+    "@azure/identity": "4.13.1",
+    "@azure/identity-cache-persistence": "1.3.0",
     "@github/copilot-sdk": "1.0.6"
   }
 }