security

HOSTING.md

@@ -241,6 +241,8 @@ Files in `storage/` are untouched by updates and keep working.
 
 - The app binds to loopback; only the proxy is exposed.
 - Download/deletion require the unguessable key; everything else is `404`.
+- Optional per-file passwords are stored only as scrypt hashes; entry mints a
+  short-lived HMAC-signed cookie (server secret in `storage/.secret`).
 - Rate limiting protects the keyed endpoints; `TRUST_PROXY=1` must only be set
   when a proxy really sets `X-Forwarded-For`/`CF-Connecting-IP`.
 - Files never expire. Deletion requires possession of the key

README.md

@@ -1,4 +1,4 @@
-# File Drop
+# File Drop (VYBECODED)
 
 A minimal, self-hosted private file hosting service built with **Bun** and
 **TypeScript**. Upload a file, get a secret, unguessable download link. Files are
@@ -10,6 +10,7 @@ database, no object storage, no queue, and no automatic cleanup.
 ## Features
 
 - Drag & drop / file-picker uploads with progress, straight from the browser.
+- **Optional per-file password**: protect a download link with a password.
 - Permanent storage on the local filesystem; files survive restarts.
 - A cryptographically secure, unguessable download key for every file.
 - Streaming uploads and downloads — no full buffering in RAM, large files work.
@@ -68,7 +69,7 @@ Then open http://localhost:3000.
 3. The server stores it permanently and returns a URL like
    `https://files.example.com/d/8fJ...random-secret...`.
 4. Copy the URL. Anyone possessing it can download the file; nobody without the
-   secret can.
+   secret can. If a password was set, the downloader must also enter it.
 5. The file stays available indefinitely. It is removed only by explicit
    deletion.
 
@@ -76,6 +77,7 @@ Then open http://localhost:3000.
 
 ```
 storage/
+├── .secret                   # server signing secret (0600), auto-generated
 ├── files/
 │   ├── <file-id>            # the raw uploaded bytes
 │   └── <file-id>
@@ -98,7 +100,10 @@ Example metadata record (`storage/metadata/<file-id>.json`):
 ```
 
 Only a SHA-256 **hash** of the download key is stored — the plaintext key exists
-only inside the URL shown to the uploader.
+only inside the URL shown to the uploader. If a download password is set, only
+its scrypt hash is stored (see [password protection](#password-protection)).
+The server signing secret for download cookies lives in `storage/.secret`
+(`0600`), created on first start and reused across restarts.
 
 Uploads are first streamed to a `<file-id>.part` temp file and atomically renamed
 into place on completion. At startup the server sweeps for orphans (a file
@@ -110,10 +115,12 @@ touched.
 
 ### `POST /api/upload`
 
-Multipart/form-data with a `file` field (this is what the web UI uses).
+Multipart/form-data with a `file` field (this is what the web UI uses). An
+optional `password` field protects the download with a password.
 
 ```bash
 curl -F "[email protected]" http://localhost:3000/api/upload
+curl -F "password=hunter2" -F "[email protected]" http://localhost:3000/api/upload
 ```
 
 ```json
@@ -122,19 +129,39 @@ curl -F "[email protected]" http://localhost:3000/api/upload
   "key": "YOWJyhDXxhe3-L8MpEFBbAN_e93AqTrEMYutkmStScq5VfbQlrqUt9yHkqmeRp7OQ",
   "url": "/d/YOWJyhDXxhe3-L8MpEFBbAN_e93AqTrEMYutkmStScq5VfbQlrqUt9yHkqmeRp7OQ",
   "originalName": "example.zip",
-  "size": 123456
+  "size": 123456,
+  "protected": false
 }
 ```
 
 ### `GET /d/:key` (also `HEAD`)
 
 Streams the file. Requires the full secret key; any wrong or non-existent key
-returns a generic `404`.
+returns a generic `404`. If the file has a password, the server first shows a
+password prompt (see below).
 
 ```bash
 curl -O http://localhost:3000/d/YOWJyh...7OQ
 ```
 
+### Password protection
+
+For files uploaded with a `password` field:
+
+1. `GET /d/:key` returns a small HTML password form.
+2. The browser submits it to `POST /api/auth/:key` with `password=...`.
+3. On success the server sets a short-lived (30 min), HttpOnly, SameSite=Lax,
+   signed cookie and redirects back to `/d/:key`, which then streams the file.
+
+```bash
+curl -c cookies.txt -X POST -d "password=hunter2" http://localhost:3000/api/auth/:key
+curl -b cookies.txt -O http://localhost:3000/d/:key
+```
+
+The cookie is signed with a server secret (`storage/.secret`) so it cannot be
+forged, and it survives server restarts. Without it, a protected file is never
+downloadable — not even by the uploader.
+
 ### `DELETE /api/files/:id`
 
 Permanently deletes the file and its metadata. The correct download key must be
@@ -164,6 +191,9 @@ paths or stack traces.
   or filenames are ever used as secrets.
 - **At-rest.** Only a SHA-256 hash of the key is persisted. Comparisons use
   constant-time `timingSafeEqual`.
+- **Passwords.** An optional per-file password is stored only as an **scrypt**
+  hash (salted), never in plaintext. Successful entry mints a short-lived
+  HMAC-signed cookie, so access is granted by the server and cannot be forged.
 - **Path safety.** Filesystem paths are built only from server-generated,
   regex-validated ids (`^[A-Za-z0-9_-]{22}$`). The original filename is metadata
   only and is sanitized (basename, control/null bytes stripped) before being
@@ -314,4 +344,4 @@ src/
 ```
 
 Intentionally small: no framework, no DI, no ORM, no repositories. Bun +
-TypeScript + filesystem + a simple frontend + secret URLs.
+TypeScript + filesystem + a simple frontend + secret URLs.

scripts/smoke-test.sh

@@ -73,6 +73,18 @@ check "delete with key succeeds" \
 check "file gone after delete" test \
   "$(curl -sS -o /dev/null -w '%{http_code}' "$BASE$URL")" = "404"
 
+echo
+echo "-- password protection --"
+check "upload with password" curl -sS -f -F "password=hunter2" -F "file=@$TMP/plain.txt" "$BASE/api/upload" > "$TMP/upP.json"
+KP="$(get "$TMP/upP.json" key)"
+check "protected file serves a password form" test \
+  "$(curl -sS -o /dev/null -w '%{content_type}' "$BASE/d/$KP")" = "text/html; charset=utf-8"
+check "wrong password is rejected" test \
+  "$(curl -sS -o /dev/null -w '%{http_code}' -X POST -d 'password=nope' "$BASE/api/auth/$KP")" = "302"
+check "correct password returns redirect" curl -sS -c "$TMP/cj.txt" -X POST -d "password=hunter2" "$BASE/api/auth/$KP" >/dev/null
+curl -sS -b "$TMP/cj.txt" -o "$TMP/downP.txt" "$BASE/d/$KP"
+check "download with cookie matches" cmp "$TMP/plain.txt" "$TMP/downP.txt"
+
 echo
 echo "passed: $pass, failed: $fail"
 [ "$fail" -eq 0 ] || exit 1

src/auth.ts

@@ -0,0 +1,98 @@
+import { makeAuthToken, parseAuthToken } from "./security";
+
+export const AUTH_COOKIE = "fh_auth";
+export const AUTH_TTL_MS = 30 * 60 * 1000;
+
+export function parseCookie(header: string | null, name: string): string | null {
+  if (!header) return null;
+  for (const part of header.split(";")) {
+    const idx = part.indexOf("=");
+    if (idx === -1) continue;
+    if (part.slice(0, idx).trim() === name) return part.slice(idx + 1).trim();
+  }
+  return null;
+}
+
+export function hasValidAuth(req: Request, secret: string, key: string): boolean {
+  const token = parseCookie(req.headers.get("cookie"), AUTH_COOKIE);
+  if (!token) return false;
+  const parsed = parseAuthToken(token, secret);
+  return parsed !== null && parsed.key === key;
+}
+
+export function authCookieValue(key: string, secret: string): string {
+  const token = makeAuthToken(key, secret, AUTH_TTL_MS);
+  return `${AUTH_COOKIE}=${token}`;
+}
+
+function escapeHtml(value: string): string {
+  return value
+    .replace(/&/g, "&")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;")
+    .replace(/'/g, "&#39;");
+}
+
+export function renderPasswordForm(
+  key: string,
+  filename: string,
+  error: boolean,
+): Response {
+  const message = error
+    ? '<p class="err">Incorrect password. Please try again.</p>'
+    : "";
+  const html = `<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="referrer" content="no-referrer" />
+    <title>Protected file</title>
+    <style>
+      * { box-sizing: border-box; }
+      body {
+        margin: 0; font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
+        background: #0f1115; color: #e6e8ee; min-height: 100vh;
+        display: flex; align-items: center; justify-content: center; padding: 16px;
+      }
+      .card {
+        width: 100%; max-width: 380px; background: #171a21; border: 1px solid #2a2f3a;
+        border-radius: 14px; padding: 26px; box-shadow: 0 10px 40px rgba(0,0,0,.35);
+      }
+      h1 { margin: 0 0 4px; font-size: 19px; }
+      p { margin: 6px 0 16px; color: #9aa3b2; font-size: 14px; word-break: break-all; }
+      .err { margin: 0 0 14px; color: #e05252; background: rgba(224,82,82,.08);
+             border: 1px solid rgba(224,82,82,.3); border-radius: 8px; padding: 9px 12px; }
+      input[type="password"] {
+        width: 100%; background: #0f1115; border: 1px solid #2a2f3a; color: #e6e8ee;
+        border-radius: 8px; padding: 11px 12px; font-size: 14px; margin-bottom: 12px;
+      }
+      button { width: 100%; font: inherit; cursor: pointer; border: none; border-radius: 8px;
+        padding: 11px 14px; font-size: 14px; background: #4f8cff; color: #fff; }
+      button:hover { background: #3a74e0; }
+    </style>
+  </head>
+  <body>
+    <main class="card">
+      <h1>Protected file</h1>
+      <p>Enter the password to download <strong>${escapeHtml(filename)}</strong>.</p>
+      ${message}
+      <form method="post" action="/api/auth/${key}">
+        <input type="password" name="password" placeholder="Password" autofocus autocomplete="off" />
+        <button type="submit">Download</button>
+      </form>
+    </main>
+  </body>
+</html>`;
+  return new Response(html, {
+    status: 200,
+    headers: {
+      "content-type": "text/html; charset=utf-8",
+      "cache-control": "private, no-store",
+      "x-content-type-options": "nosniff",
+      "referrer-policy": "no-referrer",
+      "content-security-policy": "default-src 'none'; style-src 'unsafe-inline'; form-action 'self'; base-uri 'none'; frame-ancestors 'none'",
+    },
+  });
+}

src/multipart.ts

@@ -2,8 +2,9 @@ const CR = 0x0d;
 const LF = 0x0a;
 const MAX_HEADER_LINE_BYTES = 64 * 1024;
 
-export interface MultipartFilePart {
+export interface MultipartPart {
-  filename: string;
+  name: string;
+  filename: string | null;
   contentType: string;
   chunks: AsyncIterable<Uint8Array>;
 }
@@ -36,7 +37,7 @@ async function* streamChunks(stream: ReadableStream<Uint8Array>): AsyncGenerator
 export async function* multipartParts(
   body: ReadableStream<Uint8Array>,
   boundary: string,
-): AsyncGenerator<MultipartFilePart> {
+): AsyncGenerator<MultipartPart> {
   const DELIMITER = Buffer.from(`--${boundary}`);
   const CRLF_DELIMITER = Buffer.concat([Buffer.from("\r\n"), DELIMITER]);
   const FINAL_MARKER = `--${boundary}--`;
@@ -128,18 +129,14 @@ export async function* multipartParts(
       const quoted = /filename\s*=\s*"([^"]*)"/i.exec(disposition);
       filename = quoted?.[1];
     }
+    const name = /name\s*=\s*"([^"]*)"/i.exec(disposition)?.[1] ?? "";
 
-    if (!filename) {
+    yield {
-      for await (const _ of contentChunks()) {
+      name,
-        void _;
+      filename: filename ?? null,
-      }
+      contentType: headers.get("content-type") ?? "application/octet-stream",
-    } else {
+      chunks: contentChunks(),
-      yield {
+    };
-        filename,
-        contentType: headers.get("content-type") ?? "application/octet-stream",
-        chunks: contentChunks(),
-      };
-    }
 
     for (;;) {
       const marker = await readLine();

src/public/app.js

@@ -6,6 +6,7 @@ const STORAGE_KEY = "filehost.uploads";
 
 const dropzone = $("dropzone");
 const fileInput = $("fileInput");
+const pwInput = $("pwInput");
 const progress = $("progress");
 const progressBar = $("progressBar");
 const progressPct = $("progressPct");
@@ -14,6 +15,7 @@ const result = $("result");
 const resultUrl = $("resultUrl");
 const resultName = $("resultName");
 const resultSize = $("resultSize");
+const resultLock = $("resultLock");
 const copyBtn = $("copyBtn");
 const deleteBtn = $("deleteBtn");
 const againBtn = $("againBtn");
@@ -57,10 +59,12 @@ function reset() {
   uploading = false;
   current = null;
   result.classList.add("hidden");
+  resultLock.classList.add("hidden");
   progress.classList.add("hidden");
   progressBar.style.width = "0%";
   progressPct.textContent = "0%";
   fileInput.value = "";
+  pwInput.value = "";
   clearNotice();
 }
 
@@ -160,6 +164,13 @@ function renderList() {
     name.textContent = item.originalName;
     name.title = item.originalName;
 
+    if (item.protected) {
+      const lock = document.createElement("span");
+      lock.className = "lock";
+      lock.textContent = "Password protected";
+      name.appendChild(lock);
+    }
+
     const sub = document.createElement("span");
     sub.className = "file-item-sub";
     let subText = formatBytes(item.size || 0);
@@ -182,7 +193,6 @@ function renderList() {
     dl.className = "btn-link";
     dl.href = downloadUrl(item);
     dl.textContent = "Download";
-    dl.setAttribute("download", "");
     dl.title = "Open download link";
 
     const copy = document.createElement("button");
@@ -243,6 +253,7 @@ function showResult(data) {
   resultName.textContent = data.originalName;
   resultSize.textContent = formatBytes(data.size);
   resultUrl.value = downloadUrl(data);
+  resultLock.classList.toggle("hidden", !data.protected);
   current = data;
   addUpload({
     id: data.id,
@@ -250,6 +261,7 @@ function showResult(data) {
     url: data.url,
     originalName: data.originalName,
     size: data.size,
+    protected: !!data.protected,
     createdAt: new Date().toISOString(),
   });
 }
@@ -264,6 +276,7 @@ function startUpload(file) {
 
   const xhr = new XMLHttpRequest();
   const form = new FormData();
+  if (pwInput.value) form.append("password", pwInput.value);
   form.append("file", file);
 
   xhr.upload.addEventListener("progress", (e) => {

src/public/index.html

@@ -19,6 +19,16 @@
         <p class="dz-sub">or click to choose</p>
       </div>
 
+      <div class="pw-row">
+        <input
+          type="password"
+          id="pwInput"
+          placeholder="Optional password (protects the download)"
+          autocomplete="off"
+          aria-label="Optional download password"
+        />
+      </div>
+
       <div id="progress" class="progress hidden">
         <div class="progress-label">
           <span id="progressName"></span>
@@ -33,6 +43,7 @@
         <div class="result-meta">
           <strong id="resultName"></strong>
           <span id="resultSize"></span>
+          <span id="resultLock" class="lock hidden">Password protected</span>
         </div>
         <div class="url-row">
           <input id="resultUrl" type="text" readonly aria-label="Download URL" />

src/public/style.css

@@ -75,6 +75,38 @@ h1 {
   font-size: 13px;
 }
 
+.pw-row {
+  margin-top: 12px;
+}
+
+.pw-row input {
+  width: 100%;
+  background: var(--bg);
+  border: 1px solid var(--border);
+  color: var(--text);
+  border-radius: 8px;
+  padding: 10px 12px;
+  font-size: 13px;
+}
+
+.pw-row input:focus {
+  outline: none;
+  border-color: var(--accent);
+}
+
+.lock {
+  display: inline-block;
+  margin-left: 8px;
+  font-size: 11px;
+  font-weight: 600;
+  color: var(--muted);
+  background: rgba(79, 140, 255, 0.12);
+  border: 1px solid rgba(79, 140, 255, 0.3);
+  border-radius: 99px;
+  padding: 2px 8px;
+  vertical-align: middle;
+}
+
 .progress {
   margin-top: 20px;
 }

src/routes/auth.ts

@@ -0,0 +1,45 @@
+import { AUTH_COOKIE, AUTH_TTL_MS } from "../auth";
+import { notFound } from "../http";
+import { log } from "../log";
+import { fileIdFromKey, KEY_PATTERN, makeAuthToken, passwordMatches } from "../security";
+import type { Storage } from "../storage";
+
+export async function handleAuth(
+  req: Request,
+  storage: Storage,
+  rawKey: string,
+  secret: string,
+  secure: boolean,
+): Promise<Response> {
+  if (!KEY_PATTERN.test(rawKey)) return notFound();
+  const id = fileIdFromKey(rawKey);
+  if (!id) return notFound();
+
+  const meta = await storage.readMetadata(id);
+  if (!meta) return notFound();
+
+  if (!meta.passwordHash) {
+    return new Response(null, { status: 302, headers: { location: `/d/${rawKey}` } });
+  }
+
+  const password = await req.formData().then(
+    (form) => {
+      const value = form.get("password");
+      return typeof value === "string" ? value : "";
+    },
+    () => "",
+  );
+
+  if (!passwordMatches(meta.passwordHash, password)) {
+    log("warn", `auth failed id=${id}`);
+    return new Response(null, { status: 302, headers: { location: `/d/${rawKey}?e=1` } });
+  }
+
+  const token = makeAuthToken(rawKey, secret, AUTH_TTL_MS);
+  const cookie = `${AUTH_COOKIE}=${token}; Path=/; HttpOnly; SameSite=Lax${
+    secure ? "; Secure" : ""
+  }; Max-Age=${Math.floor(AUTH_TTL_MS / 1000)}`;
+
+  log("info", `auth ok id=${id}`);
+  return new Response(null, { status: 302, headers: { location: `/d/${rawKey}`, "set-cookie": cookie } });
+}

src/routes/download.ts

@@ -1,4 +1,5 @@
 import { lstat } from "node:fs/promises";
+import { hasValidAuth, renderPasswordForm } from "../auth";
 import { notFound } from "../http";
 import { log } from "../log";
 import { contentDisposition, fileIdFromKey, KEY_PATTERN, secretMatches } from "../security";
@@ -8,6 +9,7 @@ export async function handleDownload(
   req: Request,
   storage: Storage,
   rawKey: string,
+  secret: string,
 ): Promise<Response> {
   if (!KEY_PATTERN.test(rawKey)) return notFound();
   const id = fileIdFromKey(rawKey);
@@ -17,6 +19,11 @@ export async function handleDownload(
   if (!meta) return notFound();
   if (!secretMatches(meta.downloadKeyHash, rawKey)) return notFound();
 
+  if (meta.passwordHash && !hasValidAuth(req, secret, rawKey)) {
+    const url = new URL(req.url);
+    return renderPasswordForm(rawKey, meta.originalName, url.searchParams.has("e"));
+  }
+
   const filePath = storage.filePath(id);
   let fileStat;
   try {

src/routes/upload.ts

@@ -1,9 +1,27 @@
 import { json, jsonError } from "../http";
 import { log } from "../log";
-import { getBoundary, MultipartError, multipartParts } from "../multipart";
+import { getBoundary, MultipartError, multipartParts, type MultipartPart } from "../multipart";
-import { hashSecret, newDownloadKey, newFileId, sanitizeMime, sanitizeOriginalName } from "../security";
+import {
+  hashPassword,
+  hashSecret,
+  newDownloadKey,
+  newFileId,
+  sanitizeMime,
+  sanitizeOriginalName,
+} from "../security";
 import { UploadTooLargeError, type Storage } from "../storage";
 
+const MAX_PASSWORD_LENGTH = 256;
+
+async function readField(part: MultipartPart, limit: number): Promise<string> {
+  let value = "";
+  for await (const chunk of part.chunks) {
+    value += Buffer.from(chunk).toString("utf8");
+    if (value.length > limit) throw new MultipartError("field too long");
+  }
+  return value;
+}
+
 export async function handleUpload(
   req: Request,
   storage: Storage,
@@ -21,34 +39,48 @@ export async function handleUpload(
     let mime = "application/octet-stream";
     let size = 0;
     let hasFile = false;
+    let password = "";
 
     for await (const part of multipartParts(req.body, boundary)) {
-      if (!hasFile) {
+      if (part.filename != null) {
-        hasFile = true;
+        if (!hasFile) {
-        filename = part.filename;
+          hasFile = true;
-        mime = sanitizeMime(part.contentType);
+          filename = part.filename;
-        size = await storage.saveFile(id, part.chunks, maxFileSize);
+          mime = sanitizeMime(part.contentType);
-        break;
+          size = await storage.saveFile(id, part.chunks, maxFileSize);
-      }
+        } else {
-      for await (const _ of part.chunks) {
+          for await (const _ of part.chunks) {
-        void _;
+            void _;
+          }
+        }
+      } else if (part.name === "password" && password === "") {
+        password = await readField(part, MAX_PASSWORD_LENGTH);
+      } else {
+        for await (const _ of part.chunks) {
+          void _;
+        }
       }
     }
 
     if (!hasFile) return jsonError(400, "no file part in the upload");
 
     const originalName = sanitizeOriginalName(filename);
+    const protected_ = password.trim().length > 0;
     await storage.writeMetadata({
       id,
       originalName,
       size,
       mimeType: mime,
       downloadKeyHash: hashSecret(key),
+      passwordHash: protected_ ? hashPassword(password) : undefined,
       createdAt: new Date().toISOString(),
     });
 
-    log("info", `upload ok id=${id} size=${size} name=${JSON.stringify(originalName)}`);
+    log(
-    return json({ id, key, url: `/d/${key}`, originalName, size });
+      "info",
+      `upload ok id=${id} size=${size} name=${JSON.stringify(originalName)} protected=${protected_}`,
+    );
+    return json({ id, key, url: `/d/${key}`, originalName, size, protected: protected_ });
   } catch (err) {
     await storage.delete(id);
     await storage.deletePartial(id);

src/security.ts

@@ -1,4 +1,4 @@
-import { createHash, randomBytes, timingSafeEqual } from "node:crypto";
+import { createHash, createHmac, randomBytes, scryptSync, timingSafeEqual } from "node:crypto";
 
 export const ID_BYTES = 16;
 export const KEY_BYTES = 32;
@@ -54,3 +54,51 @@ export function contentDisposition(name: string): string {
   );
   return `attachment; filename="${ascii}"; filename*=UTF-8''${encoded}`;
 }
+
+export function hashPassword(password: string): string {
+  const salt = randomBytes(16).toString("hex");
+  const hash = scryptSync(password, salt, 64).toString("hex");
+  return `scrypt:${salt}:${hash}`;
+}
+
+export function passwordMatches(stored: string, password: string): boolean {
+  const parts = stored.split(":");
+  if (parts.length !== 3 || parts[0] !== "scrypt") return false;
+  const salt = parts[1]!;
+  const expected = Buffer.from(parts[2]!, "hex");
+  const computed = scryptSync(password, salt, 64);
+  if (expected.length !== computed.length) return false;
+  return timingSafeEqual(expected, computed);
+}
+
+export function safeStringEqual(a: string, b: string): boolean {
+  const ab = Buffer.from(a);
+  const bb = Buffer.from(b);
+  if (ab.length !== bb.length) return false;
+  return timingSafeEqual(ab, bb);
+}
+
+function hmacSign(payload: string, secret: string): string {
+  return createHmac("sha256", secret).update(payload).digest("base64url");
+}
+
+export function makeAuthToken(key: string, secret: string, ttlMs: number): string {
+  const expires = Date.now() + ttlMs;
+  const payload = `${key}.${expires}`;
+  return `${payload}.${hmacSign(payload, secret)}`;
+}
+
+export function parseAuthToken(token: string, secret: string): { key: string } | null {
+  const lastDot = token.lastIndexOf(".");
+  if (lastDot <= 0) return null;
+  const payload = token.slice(0, lastDot);
+  const signature = token.slice(lastDot + 1);
+  if (!safeStringEqual(signature, hmacSign(payload, secret))) return null;
+  const dot = payload.lastIndexOf(".");
+  if (dot <= 0) return null;
+  const key = payload.slice(0, dot);
+  const expires = Number(payload.slice(dot + 1));
+  if (!Number.isFinite(expires) || expires <= Date.now()) return null;
+  if (!KEY_PATTERN.test(key)) return null;
+  return { key };
+}

src/server.ts

@@ -3,6 +3,7 @@ import { loadConfig } from "./config";
 import { json, jsonError, notFound, securityHeaders } from "./http";
 import { log } from "./log";
 import { RateLimiter } from "./ratelimit";
+import { handleAuth } from "./routes/auth";
 import { handleDelete } from "./routes/delete";
 import { handleDownload } from "./routes/download";
 import { handleUpload } from "./routes/upload";
@@ -12,6 +13,7 @@ const cfg = loadConfig();
 
 const storage = new Storage(cfg.storageDir);
 await storage.init();
+const secret = await storage.loadSecret();
 const sweep = await storage.sweep();
 if (sweep.removedFiles > 0 || sweep.removedMetadata > 0) {
   log(
@@ -77,6 +79,11 @@ function serveStatic(path: string): Response {
   });
 }
 
+function isSecure(req: Request, url: URL): boolean {
+  if (cfg.trustProxy) return req.headers.get("x-forwarded-proto") === "https";
+  return url.protocol === "https:";
+}
+
 async function route(req: Request, srv: Server<undefined>): Promise<Response> {
   const url = new URL(req.url);
   const path = url.pathname;
@@ -92,11 +99,18 @@ async function route(req: Request, srv: Server<undefined>): Promise<Response> {
     return handleUpload(req, storage, cfg.maxFileSize);
   }
 
+  if (path.startsWith("/api/auth/") && method === "POST") {
+    if (cfg.rateLimitEnabled && !limiter.check(clientIp(req, srv))) {
+      return jsonError(429, "too many requests");
+    }
+    return handleAuth(req, storage, path.slice("/api/auth/".length), secret, isSecure(req, url));
+  }
+
   if (path.startsWith("/d/") && (method === "GET" || method === "HEAD")) {
     if (cfg.rateLimitEnabled && !limiter.check(clientIp(req, srv))) {
       return jsonError(429, "too many requests");
     }
-    return handleDownload(req, storage, path.slice(3));
+    return handleDownload(req, storage, path.slice(3), secret);
   }
 
   if (path.startsWith("/api/files/") && method === "DELETE") {

src/storage.ts

@@ -1,4 +1,5 @@
 import { mkdir, readdir, readFile, rename, rm, stat, writeFile } from "node:fs/promises";
+import { randomBytes } from "node:crypto";
 import { join } from "node:path";
 import { ID_PATTERN } from "./security";
 
@@ -8,6 +9,7 @@ export interface FileMeta {
   size: number;
   mimeType: string;
   downloadKeyHash: string;
+  passwordHash?: string;
   createdAt: string;
 }
 
@@ -35,6 +37,19 @@ export class Storage {
     await mkdir(this.metadataDir, { recursive: true });
   }
 
+  async loadSecret(): Promise<string> {
+    const path = join(this.root, ".secret");
+    try {
+      const existing = (await readFile(path, "utf8")).trim();
+      if (existing) return existing;
+    } catch {
+      /* missing or unreadable: create below */
+    }
+    const secret = randomBytes(32).toString("base64url");
+    await writeFile(path, secret, { encoding: "utf8", mode: 0o600 });
+    return secret;
+  }
+
   filePath(id: string): string {
     if (!ID_PATTERN.test(id)) throw new Error("invalid file id");
     return join(this.filesDir, id);