Use raw format to GET data from IPFS gateway

packages/content/src/ipfs.ts

@@ -15,9 +15,13 @@ export async function fetchFromIpfs(
   data: Uint8Array;
   contentType?: string;
 }> {
-  const url = `${gateway}/ipfs/${cid}`;
+  // Request the raw block: a bare GET lets the gateway content-negotiate and
+  // mutate the body (e.g. serve it as text/html), breaking CID verification.
+  const url = `${gateway}/ipfs/${cid}?format=raw`;
 
-  const response = await fetch(url);
+  const response = await fetch(url, {
+    headers: { Accept: "application/vnd.ipld.raw" },
+  });
 
   if (!response.ok) {
     throw new Error(

packages/content/tests/ipfs.test.ts

@@ -0,0 +1,94 @@
+// Copyright 2026 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { fetchFromIpfs, fetchCarFromIpfs } from "@dotli/content/ipfs";
+
+const CID = "bafkreigh2akiscaildcqabsyg3dfr6chu3fgpregiymsck7e7aqa4s52zy";
+const GATEWAY = "https://gw.example";
+
+let fetchMock: ReturnType<typeof vi.fn>;
+
+beforeEach(() => {
+  fetchMock = vi.fn();
+  vi.stubGlobal("fetch", fetchMock);
+});
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe("fetchFromIpfs", () => {
+  // Regression guard: a bare GET lets a gateway content-negotiate and mutate
+  // the body (e.g. Cloudflare rewriting text/html), so the bytes no longer
+  // hash to the CID. We must request the raw block as a binary type.
+  it("requests the raw block with ?format=raw and the raw Accept header", async () => {
+    fetchMock.mockResolvedValue(
+      new Response(new Uint8Array([1, 2, 3]), { status: 200 }),
+    );
+
+    await fetchFromIpfs(CID, GATEWAY);
+
+    expect(fetchMock).toHaveBeenCalledWith(
+      `${GATEWAY}/ipfs/${CID}?format=raw`,
+      expect.objectContaining({
+        headers: { Accept: "application/vnd.ipld.raw" },
+      }),
+    );
+  });
+
+  it("returns the response bytes and content type", async () => {
+    fetchMock.mockResolvedValue(
+      new Response(new Uint8Array([0xde, 0xad, 0xbe, 0xef]), {
+        status: 200,
+        headers: { "content-type": "application/vnd.ipld.raw" },
+      }),
+    );
+
+    const { data, contentType } = await fetchFromIpfs(CID, GATEWAY);
+
+    expect(Array.from(data)).toEqual([0xde, 0xad, 0xbe, 0xef]);
+    expect(contentType).toBe("application/vnd.ipld.raw");
+  });
+
+  it("throws on a non-ok response", async () => {
+    fetchMock.mockResolvedValue(new Response(null, { status: 502 }));
+
+    await expect(fetchFromIpfs(CID, GATEWAY)).rejects.toThrow(/502/);
+  });
+});
+
+describe("fetchCarFromIpfs", () => {
+  // CAR is also a binary type, so it is likewise immune to gateway text/html
+  // rewriting — this asserts the request stays binary.
+  it("requests the CAR archive with ?format=car and the CAR Accept header", async () => {
+    fetchMock.mockResolvedValue(
+      new Response(new Uint8Array([1, 2, 3]), { status: 200 }),
+    );
+
+    await fetchCarFromIpfs(CID, GATEWAY);
+
+    expect(fetchMock).toHaveBeenCalledWith(
+      `${GATEWAY}/ipfs/${CID}?format=car`,
+      expect.objectContaining({
+        headers: { Accept: "application/vnd.ipld.car" },
+      }),
+    );
+  });
+
+  it("returns the response bytes", async () => {
+    fetchMock.mockResolvedValue(
+      new Response(new Uint8Array([0xca, 0xfe]), { status: 200 }),
+    );
+
+    const data = await fetchCarFromIpfs(CID, GATEWAY);
+
+    expect(Array.from(data)).toEqual([0xca, 0xfe]);
+  });
+
+  it("throws on a non-ok response", async () => {
+    fetchMock.mockResolvedValue(new Response(null, { status: 502 }));
+
+    await expect(fetchCarFromIpfs(CID, GATEWAY)).rejects.toThrow(/502/);
+  });
+});