fix: harden machine federation boundaries

src/server/git/gitEnv.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from "vitest";
+import { sanitizedGitEnv } from "./gitEnv.js";
+
+describe("sanitizedGitEnv", () => {
+  it("removes repository-local Git variables inherited from hooks", () => {
+    const env = sanitizedGitEnv({
+      PATH: "/bin",
+      GIT_DIR: "/repo/.git",
+      GIT_WORK_TREE: "/repo",
+      GIT_INDEX_FILE: "/repo/.git/index.lock",
+      GIT_PREFIX: "src/",
+      GIT_COMMON_DIR: "/repo/.git",
+    });
+
+    expect(env).toEqual({ PATH: "/bin" });
+  });
+});

src/server/git/gitEnv.ts

@@ -0,0 +1,15 @@
+const GIT_LOCAL_ENV_VARS = [
+  "GIT_ALTERNATE_OBJECT_DIRECTORIES",
+  "GIT_COMMON_DIR",
+  "GIT_DIR",
+  "GIT_INDEX_FILE",
+  "GIT_OBJECT_DIRECTORY",
+  "GIT_PREFIX",
+  "GIT_QUARANTINE_PATH",
+  "GIT_WORK_TREE",
+];
+
+export function sanitizedGitEnv(env: NodeJS.ProcessEnv = process.env): NodeJS.ProcessEnv {
+  const blocked = new Set<string>(GIT_LOCAL_ENV_VARS);
+  return Object.fromEntries(Object.entries(env).filter(([key]) => !blocked.has(key)));
+}

src/server/git/gitService.ts

@@ -2,6 +2,7 @@ import { createHash } from "node:crypto";
 import { spawn } from "node:child_process";
 import type { GitDiffResponse, GitFileState, GitStatusFile, GitStatusResponse } from "../../shared/apiTypes.js";
 import { normalizeRelativePath } from "../workspaces/pathSafety.js";
+import { sanitizedGitEnv } from "./gitEnv.js";
 
 const MAX_OUTPUT = 2 * 1024 * 1024;
 
@@ -95,7 +96,7 @@ function hash(value: string): string {
 
 async function runGit(cwd: string, args: string[]): Promise<{ code: number; stdout: string; stderr: string; truncated: boolean }> {
   return new Promise((resolve, reject) => {
-    const child = spawn("git", args, { cwd, stdio: ["ignore", "pipe", "pipe"] });
+    const child = spawn("git", args, { cwd, env: sanitizedGitEnv(), stdio: ["ignore", "pipe", "pipe"] });
     const timer = setTimeout(() => { child.kill("SIGKILL"); }, 10000);
     let stdout = Buffer.alloc(0);
     let stderr = Buffer.alloc(0);