LINE/Security: harden inbound media temp-file naming (#20792)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: f6f3eecdb3ce21ccdccd8b2c10a74ebd47ad809e
Co-authored-by: mbelinky <132747814+mbelinky@users.noreply.github.com>
Co-authored-by: mbelinky <132747814+mbelinky@users.noreply.github.com>
Reviewed-by: @mbelinky

CHANGELOG.md

@@ -16,6 +16,7 @@ Docs: https://docs.openclaw.ai
 ### Fixes
 
 - Security/Feishu: prevent path traversal in Feishu inbound media temp-file writes by replacing key-derived temp filenames with UUID-based names. Thanks @allsmog for reporting.
+- LINE/Security: harden inbound media temp-file naming by using UUID-based temp paths for downloaded media instead of external message IDs. (#20792) Thanks @mbelinky.
 - Security/Media: harden local media ingestion against TOCTOU/symlink swap attacks by pinning reads to a single file descriptor with symlink rejection and inode/device verification in `saveMediaSource`. Thanks @dorjoos for reporting.
 - Security/Lobster (Windows): for the next npm release, remove shell-based fallback when launching Lobster wrappers (`.cmd`/`.bat`) and switch to explicit argv execution with wrapper entrypoint resolution, preventing command injection while preserving Windows wrapper compatibility. Thanks @tdjackey for reporting.
 - Agents/Streaming: keep assistant partial streaming active during reasoning streams, handle native `thinking_*` stream events consistently, dedupe mixed reasoning-end signals, and clear stale mutating tool errors after same-target retry success. (#20635) Thanks @obviyus.

src/line/download.test.ts

@@ -0,0 +1,69 @@
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const getMessageContentMock = vi.hoisted(() => vi.fn());
+
+vi.mock("@line/bot-sdk", () => ({
+  messagingApi: {
+    MessagingApiBlobClient: class {
+      getMessageContent(messageId: string) {
+        return getMessageContentMock(messageId);
+      }
+    },
+  },
+}));
+
+vi.mock("../globals.js", () => ({
+  logVerbose: () => {},
+}));
+
+import { downloadLineMedia } from "./download.js";
+
+async function* chunks(parts: Buffer[]): AsyncGenerator<Buffer> {
+  for (const part of parts) {
+    yield part;
+  }
+}
+
+describe("downloadLineMedia", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("does not derive temp file path from external messageId", async () => {
+    const messageId = "a/../../../../etc/passwd";
+    const jpeg = Buffer.from([0xff, 0xd8, 0xff, 0x00]);
+    getMessageContentMock.mockResolvedValueOnce(chunks([jpeg]));
+
+    const writeSpy = vi.spyOn(fs.promises, "writeFile").mockResolvedValueOnce(undefined);
+
+    const result = await downloadLineMedia(messageId, "token");
+    const writtenPath = writeSpy.mock.calls[0]?.[0];
+
+    expect(result.size).toBe(jpeg.length);
+    expect(result.contentType).toBe("image/jpeg");
+    expect(typeof writtenPath).toBe("string");
+    if (typeof writtenPath !== "string") {
+      throw new Error("expected string temp file path");
+    }
+    expect(result.path).toBe(writtenPath);
+    expect(writtenPath).toContain("line-media-");
+    expect(writtenPath).toMatch(/\.jpg$/);
+    expect(writtenPath).not.toContain(messageId);
+    expect(writtenPath).not.toContain("..");
+
+    const tmpRoot = path.resolve(os.tmpdir());
+    const rel = path.relative(tmpRoot, path.resolve(writtenPath));
+    expect(rel === ".." || rel.startsWith(`..${path.sep}`)).toBe(false);
+  });
+
+  it("rejects oversized media before writing to disk", async () => {
+    getMessageContentMock.mockResolvedValueOnce(chunks([Buffer.alloc(4), Buffer.alloc(4)]));
+    const writeSpy = vi.spyOn(fs.promises, "writeFile").mockResolvedValue(undefined);
+
+    await expect(downloadLineMedia("mid", "token", 7)).rejects.toThrow(/Media exceeds/i);
+    expect(writeSpy).not.toHaveBeenCalled();
+  });
+});

src/line/download.ts

@@ -1,3 +1,4 @@
+import crypto from "node:crypto";
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
@@ -10,6 +11,10 @@ interface DownloadResult {
   size: number;
 }
 
+function buildLineTempMediaPath(extension: string): string {
+  return path.join(os.tmpdir(), `line-media-${Date.now()}-${crypto.randomUUID()}${extension}`);
+}
+
 export async function downloadLineMedia(
   messageId: string,
   channelAccessToken: string,
@@ -39,10 +44,8 @@ export async function downloadLineMedia(
   const contentType = detectContentType(buffer);
   const ext = getExtensionForContentType(contentType);
 
-  // Write to temp file
-  const tempDir = os.tmpdir();
-  const fileName = `line-media-${messageId}-${Date.now()}${ext}`;
-  const filePath = path.join(tempDir, fileName);
+  // Use random temp names; never derive paths from external message identifiers.
+  const filePath = buildLineTempMediaPath(ext);
 
   await fs.promises.writeFile(filePath, buffer);