fix(runtime-local): harden the Windows PowerShell launch path

packages/credential-store-local/src/windows.ts

@@ -1,4 +1,5 @@
 import { execFile } from "node:child_process";
+import { join } from "node:path";
 import { fileURLToPath } from "node:url";
 
 type WindowsCredentialResult = {
@@ -9,6 +10,17 @@ type WindowsCredentialResult = {
 
 const windowsScript = fileURLToPath(new URL("../runtime/windows-credential.ps1", import.meta.url));
 
+/**
+ * The OS copy of Windows PowerShell. Resolved through SystemRoot because a bare name lets
+ * CreateProcess search the current directory first, where a planted powershell.exe would run.
+ */
+function windowsPowerShell(): string {
+  const systemRoot = process.env.SystemRoot;
+  return systemRoot === undefined
+    ? "powershell.exe"
+    : join(systemRoot, "System32", "WindowsPowerShell", "v1.0", "powershell.exe");
+}
+
 /** PasswordVault password field; OAuth JSON routinely exceeds this. */
 export const windowsLockerPasswordLimit = 512;
 
@@ -31,7 +43,7 @@ export function windowsCredential(
 ): Promise<WindowsCredentialResult> {
   if (secret !== undefined) assertWindowsLockerSecret(secret, account);
   return new Promise((resolve, reject) => {
-    const child = execFile("powershell.exe", [
+    const child = execFile(windowsPowerShell(), [
       "-NoLogo", "-NoProfile", "-NonInteractive", "-ExecutionPolicy", "Bypass",
       "-File", windowsScript, "-Operation", operation,
     ], {

packages/runtime-local/src/programs.ts

@@ -183,9 +183,24 @@ async function startDetached(start: ManagedProgramCommand, root: string, logFd:
   });
 }
 
-/** A PowerShell single-quoted literal, which escapes by doubling the quote and nothing else. */
-function powershellLiteral(value: string): string {
-  return `'${value.replaceAll("'", "''")}'`;
+/**
+ * A PowerShell single-quoted literal, which escapes by doubling the quote and nothing else.
+ * Windows PowerShell accepts U+2018–U+201B as quote delimiters beside the ASCII quote, so an
+ * unescaped typographic quote would end the literal early and reopen script parsing.
+ */
+export function powershellLiteral(value: string): string {
+  return `'${value.replace(/['\u2018-\u201B]/gu, (quote) => quote + quote)}'`;
+}
+
+/**
+ * The OS copy of Windows PowerShell. Resolved through SystemRoot because a bare name lets
+ * CreateProcess search the current directory first, where a planted powershell.exe would run.
+ */
+function windowsPowerShell(): string {
+  const systemRoot = process.env.SystemRoot;
+  return systemRoot === undefined
+    ? "powershell.exe"
+    : join(systemRoot, "System32", "WindowsPowerShell", "v1.0", "powershell.exe");
 }
 
 /**
@@ -238,7 +253,12 @@ export async function startWithOwnConsole(
 ): Promise<{ readonly pid?: number; readonly detail?: string }> {
   const errorPath = processErrorLogPath(logPath);
   const environment = Object.entries(start.env ?? {})
-    .map(([name, value]) => `$env:${name} = ${powershellLiteral(String(value))}`).join("\n");
+    .map(([name, value]) => {
+      if (!/^[A-Za-z_][A-Za-z0-9_]*$/u.test(name)) {
+        throw new Error(`Program environment name ${name} must be a portable variable name`);
+      }
+      return `$env:${name} = ${powershellLiteral(String(value))}`;
+    }).join("\n");
   const argumentList = start.args.length === 0
     ? ""
     : ` -ArgumentList ${powershellLiteral(windowsCommandLine(start.args))}`;
@@ -255,7 +275,7 @@ export async function startWithOwnConsole(
 
   const shell = await new Promise<{ readonly out: string; readonly err: string }>((settle) => {
     const encoded = Buffer.from(script, "utf16le").toString("base64");
-    const child = spawn("powershell.exe", ["-NoProfile", "-NonInteractive", "-EncodedCommand", encoded], {
+    const child = spawn(windowsPowerShell(), ["-NoProfile", "-NonInteractive", "-EncodedCommand", encoded], {
       windowsHide: true,
       stdio: ["ignore", "pipe", "pipe"],
     });

packages/runtime-local/test/powershell-literal.test.ts

@@ -0,0 +1,12 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { powershellLiteral } from "../src/programs.js";
+
+test("PowerShell literals escape every quote form the tokenizer accepts", () => {
+  assert.equal(powershellLiteral("plain"), "'plain'");
+  assert.equal(powershellLiteral("it's"), "'it''s'");
+  // Windows PowerShell accepts U+2018–U+201B as quote delimiters too; each must
+  // double or the literal ends early and reopens script parsing.
+  assert.equal(powershellLiteral("it’s"), "'it’’s'");
+  assert.equal(powershellLiteral("a‘b‚c‛d"), "'a‘‘b‚‚c‛‛d'");
+});