From 21022eaa7340559088f3def144d7a2fe770257eb Mon Sep 17 00:00:00 2001
From: Jannis Braun <151788261+TheZwiss@users.noreply.github.com>
Date: Thu, 30 Apr 2026 01:13:45 +0200
Subject: [PATCH] feat(server): tus hook helpers (metadata parse, extension
 extract, ownership check)

---
 packages/server/src/utils/tusHooks.test.ts | 62 ++++++++++++++++++++++
 packages/server/src/utils/tusHooks.ts      | 57 ++++++++++++++++++++
 2 files changed, 119 insertions(+)
 create mode 100644 packages/server/src/utils/tusHooks.test.ts
 create mode 100644 packages/server/src/utils/tusHooks.ts

diff --git a/packages/server/src/utils/tusHooks.test.ts b/packages/server/src/utils/tusHooks.test.ts
new file mode 100644
index 00000000..180215f7
--- /dev/null
+++ b/packages/server/src/utils/tusHooks.test.ts
@@ -0,0 +1,62 @@
+import { describe, it, expect } from 'vitest';
+import {
+  parseUploadMetadata,
+  extractExtension,
+  buildTusMetadata,
+  isOwnerOfUpload,
+} from './tusHooks.js';
+
+describe('parseUploadMetadata', () => {
+  it('parses base64-encoded metadata pairs', () => {
+    const filename = Buffer.from('photo.png').toString('base64');
+    const meta = parseUploadMetadata(`filename ${filename},foo bar`);
+    expect(meta.filename).toBe('photo.png');
+    expect(meta.foo).toBeUndefined();          // 'bar' is not valid base64 padding here
+  });
+
+  it('returns empty object on null input', () => {
+    expect(parseUploadMetadata(null)).toEqual({});
+  });
+});
+
+describe('extractExtension', () => {
+  it('lowercases the extension', () => {
+    expect(extractExtension('Photo.PNG')).toBe('.png');
+  });
+  it('returns empty string when no extension', () => {
+    expect(extractExtension('Makefile')).toBe('');
+  });
+  it('strips path components', () => {
+    expect(extractExtension('../../../etc/passwd.txt')).toBe('.txt');
+  });
+});
+
+describe('buildTusMetadata', () => {
+  it('includes snowflakeId, userId, originalName', () => {
+    const meta = buildTusMetadata({
+      snowflakeId: '1234',
+      userId: 'u-9',
+      originalName: 'photo.png',
+    });
+    expect(meta).toMatchObject({
+      snowflakeId: '1234',
+      userId: 'u-9',
+      originalName: 'photo.png',
+    });
+  });
+});
+
+describe('isOwnerOfUpload', () => {
+  it('returns true on matching userId', () => {
+    expect(isOwnerOfUpload({ userId: 'u-9' }, 'u-9')).toBe(true);
+  });
+  it('returns false on mismatch', () => {
+    expect(isOwnerOfUpload({ userId: 'u-9' }, 'u-10')).toBe(false);
+  });
+  it('returns false on missing metadata', () => {
+    expect(isOwnerOfUpload({}, 'u-9')).toBe(false);
+  });
+  it('returns false when metadata.userId is an empty string', () => {
+    expect(isOwnerOfUpload({ userId: '' }, 'u-9')).toBe(false);
+  });
+});
diff --git a/packages/server/src/utils/tusHooks.ts b/packages/server/src/utils/tusHooks.ts
new file mode 100644
index 00000000..d54a1065
--- /dev/null
+++ b/packages/server/src/utils/tusHooks.ts
@@ -0,0 +1,57 @@
+import * as path from 'node:path';
+
+export interface UploadMetadata {
+  snowflakeId?: string;
+  userId?: string;
+  originalName?: string;
+  [k: string]: string | undefined;
+}
+
+/** Parse the comma-separated `Upload-Metadata` header into a flat object. */
+export function parseUploadMetadata(raw: string | null | undefined): UploadMetadata {
+  if (!raw) return {};
+  const out: UploadMetadata = {};
+  for (const pair of raw.split(',')) {
+    const trimmed = pair.trim();
+    if (!trimmed) continue;
+    const [key, b64] = trimmed.split(' ');
+    if (!key) continue;
+    if (!b64) {
+      // Boolean-style key (no value)
+      continue;
+    }
+    try {
+      const decoded = Buffer.from(b64, 'base64').toString('utf8');
+      // Reject if base64 round-trip mismatches — protects against odd encodings
+      if (Buffer.from(decoded, 'utf8').toString('base64').replace(/=+$/, '') !==
+          b64.replace(/=+$/, '')) continue;
+      out[key] = decoded;
+    } catch { /* ignore */ }
+  }
+  return out;
+}
+
+/** Extract a sanitized lowercase extension, stripped of path components. */
+export function extractExtension(originalName: string): string {
+  const base = path.basename(originalName);
+  const ext = path.extname(base).toLowerCase();
+  return ext;
+}
+
+/** Build the metadata object stored on tus uploads at PRE_CREATE. */
+export function buildTusMetadata(input: {
+  snowflakeId: string;
+  userId: string;
+  originalName: string;
+}): UploadMetadata {
+  return {
+    snowflakeId: input.snowflakeId,
+    userId: input.userId,
+    originalName: input.originalName,
+  };
+}
+
+/** True iff the supplied userId matches metadata.userId. Used in PRE_PATCH. */
+export function isOwnerOfUpload(metadata: UploadMetadata, userId: string): boolean {
+  return Boolean(metadata.userId) && metadata.userId === userId;
+}