fix(auth): allowlist the gh runner to read-only commands (isolation by construction)

src/services/gh-cli.ts

@@ -45,8 +45,33 @@ export type GhRunner = (args: Array<string>) => Promise<GhRunResult>
 // can't hang the settings request.
 const GH_TIMEOUT_MS = 5000
 
-const defaultRunner: GhRunner = (args) =>
-  new Promise((resolve) => {
+/**
+ * The ONLY gh subcommands maximal may run — all strictly read-only.
+ * Enforced in the real runner so a future caller can never invoke a MUTATING
+ * gh command (`auth login`/`logout`/`switch`/`refresh`/`setup-git`,
+ * `config set`, `api -X POST`, …). maximal must never change what gh is signed
+ * into or otherwise touch gh's state; this turns that prose contract into a
+ * gate. `gh auth status` and `gh auth token` only READ; `--version` is inert.
+ */
+export function isReadOnlyGhArgs(args: Array<string>): boolean {
+  if (args.length === 1 && args[0] === "--version") return true
+  if (args[0] === "auth" && (args[1] === "status" || args[1] === "token")) {
+    return true
+  }
+  return false
+}
+
+const defaultRunner: GhRunner = (args) => {
+  if (!isReadOnlyGhArgs(args)) {
+    // Defense-in-depth: never shell out a non-read-only gh command, even if a
+    // future caller passes one. Reject rather than execute.
+    return Promise.reject(
+      new Error(
+        `Refusing to run a non-read-only gh command: gh ${args.join(" ")}`,
+      ),
+    )
+  }
+  return new Promise<GhRunResult>((resolve) => {
     execFile(
       "gh",
       args,
@@ -64,6 +89,7 @@ const defaultRunner: GhRunner = (args) =>
       },
     )
   })
+}
 
 // "gh version 2.92.0 (2026-04-28)\n..." -> "2.92.0"
 function parseVersion(stdout: string): string | null {

tests/gh-cli.test.ts

@@ -4,6 +4,7 @@ import {
   detectGhCli,
   getGhAccountToken,
   type GhRunner,
+  isReadOnlyGhArgs,
 } from "~/services/gh-cli"
 
 // Build a runner that returns canned results keyed by the gh subcommand, so
@@ -154,6 +155,40 @@ describe("detectGhCli", () => {
   })
 })
 
+describe("isReadOnlyGhArgs", () => {
+  test("allows the read-only commands maximal uses", () => {
+    expect(isReadOnlyGhArgs(["--version"])).toBe(true)
+    expect(isReadOnlyGhArgs(["auth", "status", "--json", "hosts"])).toBe(true)
+    expect(
+      isReadOnlyGhArgs([
+        "auth",
+        "token",
+        "--hostname",
+        "github.com",
+        "--user",
+        "x",
+      ]),
+    ).toBe(true)
+  })
+
+  test("rejects every mutating / unknown gh command", () => {
+    for (const args of [
+      ["auth", "login"],
+      ["auth", "logout"],
+      ["auth", "switch"],
+      ["auth", "refresh"],
+      ["auth", "setup-git"],
+      ["config", "set", "x", "y"],
+      ["api", "user", "-X", "POST"],
+      ["repo", "delete", "x"],
+      ["version"], // not the "--version" form
+      [],
+    ]) {
+      expect(isReadOnlyGhArgs(args)).toBe(false)
+    }
+  })
+})
+
 describe("getGhAccountToken", () => {
   test("returns the trimmed token on success", async () => {
     const token = await getGhAccountToken(