fix: validate PDF options in template render route (BUG-103)

src/__tests__/templates-render-validation.test.ts

@@ -0,0 +1,96 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import express from "express";
+import request from "supertest";
+
+let app: express.Express;
+
+const baseData = {
+  invoiceNumber: "INV-001",
+  date: "2026-01-15",
+  from: { name: "Acme Corp" },
+  to: { name: "Client Inc" },
+  items: [{ description: "Service", quantity: 1, unitPrice: 100 }],
+};
+
+beforeEach(async () => {
+  vi.clearAllMocks();
+
+  const { renderPdf } = await import("../services/browser.js");
+  vi.mocked(renderPdf).mockResolvedValue(Buffer.from("%PDF-1.4 mock"));
+
+  const { authMiddleware } = await import("../middleware/auth.js");
+  const { usageMiddleware } = await import("../middleware/usage.js");
+  const { templatesRouter } = await import("../routes/templates.js");
+
+  app = express();
+  app.use(express.json());
+  app.use("/v1/templates", authMiddleware, usageMiddleware, templatesRouter);
+});
+
+describe("BUG-103: PDF option validation in template render", () => {
+  it("should reject invalid _format with 400", async () => {
+    const res = await request(app)
+      .post("/v1/templates/invoice/render")
+      .set("X-API-Key", "test-key")
+      .send({ data: { ...baseData, _format: "EVIL_FORMAT" } });
+    expect(res.status).toBe(400);
+    expect(res.body.error).toMatch(/format/i);
+  });
+
+  it("should accept and sanitize lowercase _format", async () => {
+    const { renderPdf } = await import("../services/browser.js");
+    const res = await request(app)
+      .post("/v1/templates/invoice/render")
+      .set("X-API-Key", "test-key")
+      .send({ data: { ...baseData, _format: "a4" } });
+    expect(res.status).toBe(200);
+    expect(vi.mocked(renderPdf)).toHaveBeenCalledWith(
+      expect.any(String),
+      expect.objectContaining({ format: "A4" })
+    );
+  });
+
+  it("should reject _margin that is not an object", async () => {
+    const res = await request(app)
+      .post("/v1/templates/invoice/render")
+      .set("X-API-Key", "test-key")
+      .send({ data: { ...baseData, _margin: "10px" } });
+    expect(res.status).toBe(400);
+    expect(res.body.error).toMatch(/margin/i);
+  });
+
+  it("should reject _margin with unknown keys", async () => {
+    const res = await request(app)
+      .post("/v1/templates/invoice/render")
+      .set("X-API-Key", "test-key")
+      .send({ data: { ...baseData, _margin: { top: "10px", bogus: "5px" } } });
+    expect(res.status).toBe(400);
+    expect(res.body.error).toMatch(/margin/i);
+  });
+
+  it("should accept valid _margin and pass sanitized to renderPdf", async () => {
+    const { renderPdf } = await import("../services/browser.js");
+    const res = await request(app)
+      .post("/v1/templates/invoice/render")
+      .set("X-API-Key", "test-key")
+      .send({ data: { ...baseData, _margin: { top: "10px", bottom: "20px" } } });
+    expect(res.status).toBe(200);
+    expect(vi.mocked(renderPdf)).toHaveBeenCalledWith(
+      expect.any(String),
+      expect.objectContaining({ margin: { top: "10px", bottom: "20px" } })
+    );
+  });
+
+  it("should default to A4 when no _format provided", async () => {
+    const { renderPdf } = await import("../services/browser.js");
+    const res = await request(app)
+      .post("/v1/templates/invoice/render")
+      .set("X-API-Key", "test-key")
+      .send({ data: { ...baseData } });
+    expect(res.status).toBe(200);
+    expect(vi.mocked(renderPdf)).toHaveBeenCalledWith(
+      expect.any(String),
+      expect.objectContaining({ format: "A4" })
+    );
+  });
+});

src/routes/templates.ts

@@ -3,6 +3,7 @@ import { renderPdf } from "../services/browser.js";
 import logger from "../services/logger.js";
 import { templates, renderTemplate } from "../services/templates.js";
 import { sanitizeFilename } from "../utils/sanitize.js";
+import { validatePdfOptions } from "../utils/pdf-options.js";
 
 export const templatesRouter = Router();
 
@@ -153,11 +154,19 @@ templatesRouter.post("/:id/render", async (req: Request, res: Response) => {
       return;
     }
 
+    // Validate PDF options from underscore-prefixed fields (BUG-103)
+    const pdfOpts: Record<string, any> = {};
+    if (data._format !== undefined) pdfOpts.format = data._format;
+    if (data._margin !== undefined) pdfOpts.margin = data._margin;
+    const validation = validatePdfOptions(pdfOpts);
+    if (!validation.valid) {
+      res.status(400).json({ error: validation.error });
+      return;
+    }
+    const sanitizedPdf = { format: "A4" as string, ...validation.sanitized };
+
     const html = renderTemplate(id, data);
-    const pdf = await renderPdf(html, {
+    const pdf = await renderPdf(html, sanitizedPdf);
-      format: data._format || "A4",
-      margin: data._margin,
-    });
 
     const filename = sanitizeFilename(data._filename || `${id}.pdf`);
     res.setHeader("Content-Type", "application/pdf");