fix(imessage): sanitize SCP remote path to prevent shell metacharacter injection

References GHSA-g2f6-pwvx-r275.

src/infra/scp-host.test.ts

@@ -1,5 +1,10 @@
 import { describe, expect, it } from "vitest";
-import { isSafeScpRemoteHost, normalizeScpRemoteHost } from "./scp-host.js";
+import {
+  isSafeScpRemoteHost,
+  isSafeScpRemotePath,
+  normalizeScpRemoteHost,
+  normalizeScpRemotePath,
+} from "./scp-host.js";
 
 describe("scp remote host", () => {
   it.each([
@@ -33,3 +38,40 @@ describe("scp remote host", () => {
     expect(isSafeScpRemoteHost(value)).toBe(false);
   });
 });
+
+describe("scp remote path", () => {
+  it.each([
+    {
+      value: "/Users/demo/Library/Messages/Attachments/ab/cd/photo.jpg",
+      expected: "/Users/demo/Library/Messages/Attachments/ab/cd/photo.jpg",
+    },
+    {
+      value: " /Users/demo/Library/Messages/Attachments/ab/cd/IMG 1234 (1).jpg ",
+      expected: "/Users/demo/Library/Messages/Attachments/ab/cd/IMG 1234 (1).jpg",
+    },
+  ])("normalizes safe paths for %j", ({ value, expected }) => {
+    expect(normalizeScpRemotePath(value)).toBe(expected);
+    expect(isSafeScpRemotePath(value)).toBe(true);
+  });
+
+  it.each([
+    null,
+    undefined,
+    "",
+    "   ",
+    "relative/path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad$path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad`path`.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad;path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad|path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad&path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad<path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad>path.jpg",
+    '/Users/demo/Library/Messages/Attachments/ab/cd/bad"path.jpg',
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad'path.jpg",
+    "/Users/demo/Library/Messages/Attachments/ab/cd/bad\\path.jpg",
+  ])("rejects unsafe path tokens: %j", (value) => {
+    expect(normalizeScpRemotePath(value)).toBeUndefined();
+    expect(isSafeScpRemotePath(value)).toBe(false);
+  });
+});

src/infra/scp-host.ts

@@ -1,6 +1,7 @@
 const SSH_TOKEN = /^[A-Za-z0-9._-]+$/;
 const BRACKETED_IPV6 = /^\[[0-9A-Fa-f:.%]+\]$/;
 const WHITESPACE = /\s/;
+const SCP_REMOTE_PATH_UNSAFE_CHARS = new Set(["\\", "'", '"', "`", "$", ";", "|", "&", "<", ">"]);
 
 function hasControlOrWhitespace(value: string): boolean {
   for (const char of value) {
@@ -60,3 +61,26 @@ export function normalizeScpRemoteHost(value: string | null | undefined): string
 export function isSafeScpRemoteHost(value: string | null | undefined): boolean {
   return normalizeScpRemoteHost(value) !== undefined;
 }
+
+export function normalizeScpRemotePath(value: string | null | undefined): string | undefined {
+  if (typeof value !== "string") {
+    return undefined;
+  }
+  const trimmed = value.trim();
+  if (!trimmed || !trimmed.startsWith("/")) {
+    return undefined;
+  }
+
+  for (const char of trimmed) {
+    const code = char.charCodeAt(0);
+    if (code <= 0x1f || code === 0x7f || SCP_REMOTE_PATH_UNSAFE_CHARS.has(char)) {
+      return undefined;
+    }
+  }
+
+  return trimmed;
+}
+
+export function isSafeScpRemotePath(value: string | null | undefined): boolean {
+  return normalizeScpRemotePath(value) !== undefined;
+}