fix: MCP cannot upload files with local storage (#13023)

* fix: MCP cannot upload files with local storage

* refactor

plugins/storage/server/api/files.test.ts

@@ -3,6 +3,7 @@ import { readFile } from "node:fs/promises";
 import path from "node:path";
 import FormData from "form-data";
 import { ensureDirSync } from "fs-extra";
+import JWT from "jsonwebtoken";
 import { FileOperationState, FileOperationType } from "@shared/types";
 import env from "@server/env";
 import AttachmentHelper, {
@@ -194,6 +195,110 @@ describe("#files.create", () => {
       existsSync(path.join(env.FILE_STORAGE_LOCAL_ROOT_DIR, attachment.key))
     ).toBe(true);
   });
+
+  it("should succeed with a valid upload signature and no session", async () => {
+    const user = await buildUser();
+    const fileName = "images.docx";
+    const attachment = await buildAttachment(
+      {
+        teamId: user.teamId,
+        userId: user.id,
+        contentType:
+          "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+      },
+      fileName
+    );
+
+    const sig = JWT.sign(
+      { key: attachment.key, type: "attachment-upload" },
+      env.SECRET_KEY,
+      { expiresIn: 3600 }
+    );
+
+    const content = await readFile(
+      path.resolve(__dirname, "..", "test", "fixtures", fileName)
+    );
+    const form = new FormData();
+    form.append("key", attachment.key);
+    form.append("file", content, fileName);
+    form.append("sig", sig);
+
+    const res = await server.post(`/api/files.create`, {
+      headers: form.getHeaders(),
+      body: form,
+    });
+
+    const body = await res.json();
+    expect(res.status).toEqual(200);
+    expect(body.success).toEqual(true);
+    expect(
+      existsSync(path.join(env.FILE_STORAGE_LOCAL_ROOT_DIR, attachment.key))
+    ).toBe(true);
+  });
+
+  it("should fail with a signature scoped to a different key", async () => {
+    const user = await buildUser();
+    const fileName = "images.docx";
+    const attachment = await buildAttachment(
+      {
+        teamId: user.teamId,
+        userId: user.id,
+        contentType:
+          "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+      },
+      fileName
+    );
+
+    const sig = JWT.sign(
+      { key: "public/foo/bar/other.png", type: "attachment-upload" },
+      env.SECRET_KEY,
+      { expiresIn: 3600 }
+    );
+
+    const content = await readFile(
+      path.resolve(__dirname, "..", "test", "fixtures", fileName)
+    );
+    const form = new FormData();
+    form.append("key", attachment.key);
+    form.append("file", content, fileName);
+    form.append("sig", sig);
+
+    const res = await server.post(`/api/files.create`, {
+      headers: form.getHeaders(),
+      body: form,
+    });
+    expect(res.status).toEqual(401);
+    expect(
+      existsSync(path.join(env.FILE_STORAGE_LOCAL_ROOT_DIR, attachment.key))
+    ).toBe(false);
+  });
+
+  it("should fail with status 401 when neither session nor signature is provided", async () => {
+    const user = await buildUser();
+    const fileName = "images.docx";
+    const attachment = await buildAttachment(
+      {
+        teamId: user.teamId,
+        userId: user.id,
+        contentType:
+          "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+      },
+      fileName
+    );
+
+    const content = await readFile(
+      path.resolve(__dirname, "..", "test", "fixtures", fileName)
+    );
+    const form = new FormData();
+    form.append("key", attachment.key);
+    form.append("file", content, fileName);
+
+    const res = await server.post(`/api/files.create`, {
+      headers: form.getHeaders(),
+      body: form,
+    });
+    expect(res.status).toEqual(401);
+  });
 });
 
 describe("#files.get", () => {

plugins/storage/server/api/files.ts

@@ -30,7 +30,7 @@ const router = new Router();
 router.post(
   "files.create",
   rateLimiter(RateLimiterStrategy.TwentyFivePerMinute),
-  auth(),
+  auth({ optional: true }),
   validate(T.FilesCreateSchema),
   timeout(30 * 60 * 1000), // 30 minutes for large file uploads
   multipart({
@@ -41,19 +41,27 @@ router.post(
   }),
   async (ctx: APIContext<T.FilesCreateReq>) => {
     const actor = ctx.state.auth.user;
-    const { key } = ctx.input.body;
+    const { key, sig } = ctx.input.body;
     const file = ctx.input.file;
 
     if (!file) {
       throw ValidationError("Request must include a file parameter");
     }
 
+    // A short-lived signature authorizes the upload to this key without a session.
+    if (sig) {
+      verifyUploadSignature(sig, key);
+    } else if (!actor) {
+      throw AuthenticationError("Authentication required");
+    }
+
     const attachment = await Attachment.findOne({
       where: { key },
       rejectOnEmpty: true,
     });
 
-    if (attachment.userId !== actor.id) {
+    // For session-based uploads, ensure the attachment belongs to the actor.
+    if (!sig && actor && attachment.userId !== actor.id) {
       throw AuthorizationError("Invalid key");
     }
 
@@ -186,6 +194,28 @@ function getByteRange(
   return { start, end };
 }
 
+/**
+ * Verifies a short-lived signature authorizing an upload to a single key.
+ *
+ * @param sig The signature to verify.
+ * @param key The key the upload is being made to.
+ * @throws AuthenticationError if the signature is invalid, expired, or scoped
+ * to a different key.
+ */
+function verifyUploadSignature(sig: string, key: string) {
+  const payload = getJWTPayload(sig);
+
+  if (payload.type !== "attachment-upload" || payload.key !== key) {
+    throw AuthenticationError("Invalid signature");
+  }
+
+  try {
+    JWT.verify(sig, env.SECRET_KEY);
+  } catch (_err) {
+    throw AuthenticationError("Invalid signature");
+  }
+}
+
 function getKeyFromContext(ctx: APIContext<T.FilesGetReq>): string {
   const { key, sig } = ctx.input.query;
   if (sig) {

plugins/storage/server/api/schema.ts

@@ -9,6 +9,7 @@ export const FilesCreateSchema = z.object({
       .string()
       .refine(ValidateKey.isValid, { message: ValidateKey.message })
       .transform(ValidateKey.sanitize),
+    sig: z.string().optional(),
   }),
   file: z.custom<formidable.File>().optional(),
 });

server/storage/files/LocalStorage.ts

@@ -23,6 +23,11 @@ export default class LocalStorage extends BaseStorage {
     maxUploadSize: number,
     contentType = "image"
   ): Promise<Partial<PresignedPost>> {
+    // A short-lived signature that authorizes uploading to this key only
+    const sig = JWT.sign({ key, type: "attachment-upload" }, env.SECRET_KEY, {
+      expiresIn: 3600,
+    });
+
     return Promise.resolve({
       url: this.getUrlForKey(key),
       fields: {
@@ -30,6 +35,7 @@ export default class LocalStorage extends BaseStorage {
         acl,
         maxUploadSize: String(maxUploadSize),
         contentType,
+        sig,
         [CSRF.fieldName]: ctx.cookies.get(CSRF.cookieName) || "",
       },
     });