fix: keep disk proxy reads inside proxy root

lib/utils/resolve-file-proxy.ts

@@ -1,6 +1,6 @@
 import type { FileProxy } from "../db/schema"
 import { readFile } from "node:fs/promises"
-import { join } from "node:path"
+import { isAbsolute, relative, resolve, sep } from "node:path"
 import { normalizePath } from "./normalize-path"
 
 export async function resolveFileProxy(
@@ -26,7 +26,17 @@ async function resolveDiskProxy(
   diskPath: string,
   relativePath: string,
 ): Promise<Response> {
-  const fullPath = join(diskPath, relativePath)
+  const proxyRoot = resolve(diskPath)
+  const fullPath = resolve(proxyRoot, relativePath)
+  const pathFromRoot = relative(proxyRoot, fullPath)
+
+  if (
+    pathFromRoot === ".." ||
+    pathFromRoot.startsWith(`..${sep}`) ||
+    isAbsolute(pathFromRoot)
+  ) {
+    return new Response("File not found", { status: 404 })
+  }
 
   try {
     const content = await readFile(fullPath)

tests/routes/file-proxy02.test.ts

@@ -91,6 +91,42 @@ test("disk proxy with query param download", async () => {
   }
 })
 
+test("disk proxy blocks paths outside proxy root", async () => {
+  const { axios } = await getTestServer()
+
+  const tempDir = await mkdtemp(join(tmpdir(), "file-proxy-root-test-"))
+  const proxyRoot = join(tempDir, "public")
+
+  try {
+    await mkdir(proxyRoot)
+    await writeFile(join(proxyRoot, "allowed.txt"), "Allowed content")
+    await writeFile(join(tempDir, "secret.txt"), "Secret content")
+
+    await axios.post("/file_proxies/create", {
+      proxy_type: "disk",
+      disk_path: proxyRoot,
+      matching_pattern: "safe-disk/*",
+    })
+
+    const allowedRes = await axios.get("/files/download", {
+      params: { file_path: "/safe-disk/allowed.txt" },
+    })
+    expect(allowedRes.status).toBe(200)
+    expect(allowedRes.data).toBe("Allowed content")
+
+    await expect(
+      axios.get("/files/download", {
+        params: { file_path: "/safe-disk/../secret.txt" },
+      }),
+    ).rejects.toMatchObject({
+      status: 404,
+      data: "File not found",
+    })
+  } finally {
+    await rm(tempDir, { recursive: true, force: true })
+  }
+})
+
 test("disk proxy binary file", async () => {
   const { axios } = await getTestServer()