[Fix] safeFetch streaming maxSize memory DoS regression test (#408) by advancedresearcharray · Pull Request #534 · clawwork-ai/ClawWork

advancedresearcharray · 2026-06-08T21:42:26Z

Summary

Issue [Bug] safeFetch buffers entire response before enforcing maxSize — memory DoS #408 reported that safeFetch buffered the entire response via res.arrayBuffer() before enforcing maxSize, enabling a memory DoS. The streaming reader fix landed in fix(net): stream safeFetch body with incremental maxSize enforcement #487 and reader cancellation in [Fix] Cancel safeFetch body reader when maxSize exceeded #523, but the issue remained open.
Adds a regression test that verifies safeFetch stops reading an oversized streamed body before draining all chunks (bounded reads + reader cancel), matching the memory-DoS scenario in the issue.

Closes #408

Test plan

pnpm --filter @clawwork/desktop test -- safe-fetch.test.ts — 25 tests passed
New test: does not read the entire oversized body before rejecting — bounded streaming (#408)

release-note

NONE

gemini-code-assist · 2026-06-08T21:42:33Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a regression test for safeFetch to ensure that it properly handles oversized streamed responses. By validating that the fetch operation terminates and cancels the stream reader as soon as the size limit is reached, it confirms the fix for a potential memory denial-of-service vulnerability.

Highlights

Regression Testing: Added a new test case to verify that safeFetch correctly enforces maxSize limits during streaming, preventing memory DoS vulnerabilities.
Streaming Validation: Ensured that the reader is cancelled and processing stops immediately once the maxSize threshold is exceeded, rather than draining the entire body.

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github-actions · 2026-06-08T21:42:38Z

Hi @advancedresearcharray,
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clawwork-ai#408) The streaming maxSize enforcement and reader cancellation were merged in clawwork-ai#487 and clawwork-ai#523, but issue clawwork-ai#408 remained open. Add a regression test that verifies safeFetch stops reading an oversized body before draining all chunks, preventing the memory DoS described in the issue. Closes clawwork-ai#408 Signed-off-by: Array Agent <advancedresearcharray@array.com> Co-authored-by: Cursor <cursoragent@cursor.com>

gemini-code-assist

Code Review

This pull request adds a new test case to verify that safeFetch implements bounded streaming and does not read an entire oversized body before rejecting. The review feedback suggests simplifying the test mock setup by directly spying on the reader returned by streamReaderFrom and returning it, rather than manually reconstructing a duplicate reader object.

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gemini-code-assist · 2026-06-08T21:43:30Z

+    const reader = streamReaderFrom(new ArrayBuffer(bodySize), chunkSize, cancel);
+    const read = vi.fn(reader.read.bind(reader));
+    netFetchMock.mockResolvedValue({
+      ok: true,
+      status: 200,
+      headers: new Headers(),
+      body: {
+        getReader: () =>
+          ({
+            read,
+            cancel,
+            releaseLock: () => {},
+            closed: Promise.resolve(undefined),
+          }) as ReadableStreamDefaultReader<Uint8Array>,
+      },
+    } as unknown as Response);
+
+    await expect(safeFetch('https://cdn.example.com/huge-stream.bin', { maxSize })).rejects.toThrow('too large');
+
+    // 5 chunks (1280 bytes) exceed maxSize; must not drain the full 10 KiB body.
+    expect(read.mock.calls.length).toBeLessThan(bodySize / chunkSize);
+    expect(read.mock.calls.length).toBeLessThanOrEqual(Math.ceil(maxSize / chunkSize) + 1);
+    expect(cancel).toHaveBeenCalledOnce();


The streamReaderFrom helper function already returns a fully-formed ReadableStreamDefaultReader<Uint8Array> object containing read, cancel, releaseLock, and closed properties. Instead of manually reconstructing a duplicate reader object in the getReader mock and manually binding/wrapping reader.read with vi.fn, you can simplify the test by spying on the reader directly with vi.spyOn(reader, 'read') and returning reader from getReader.

Suggested change

const reader = streamReaderFrom(new ArrayBuffer(bodySize), chunkSize, cancel);

const read = vi.fn(reader.read.bind(reader));

netFetchMock.mockResolvedValue({

ok: true,

status: 200,

headers: new Headers(),

body: {

getReader: () =>

({

read,

cancel,

releaseLock: () => {},

closed: Promise.resolve(undefined),

}) as ReadableStreamDefaultReader<Uint8Array>,

},

} as unknown as Response);

await expect(safeFetch('https://cdn.example.com/huge-stream.bin', { maxSize })).rejects.toThrow('too large');

// 5 chunks (1280 bytes) exceed maxSize; must not drain the full 10 KiB body.

expect(read.mock.calls.length).toBeLessThan(bodySize / chunkSize);

expect(read.mock.calls.length).toBeLessThanOrEqual(Math.ceil(maxSize / chunkSize) + 1);

expect(cancel).toHaveBeenCalledOnce();

const reader = streamReaderFrom(new ArrayBuffer(bodySize), chunkSize, cancel);

const readSpy = vi.spyOn(reader, 'read');

netFetchMock.mockResolvedValue({

ok: true,

status: 200,

headers: new Headers(),

body: {

getReader: () => reader,

},

} as unknown as Response);

await expect(safeFetch('https://cdn.example.com/huge-stream.bin', { maxSize })).rejects.toThrow('too large');

// 5 chunks (1280 bytes) exceed maxSize; must not drain the full 10 KiB body.

expect(readSpy.mock.calls.length).toBeLessThan(bodySize / chunkSize);

expect(readSpy.mock.calls.length).toBeLessThanOrEqual(Math.ceil(maxSize / chunkSize) + 1);

expect(cancel).toHaveBeenCalledOnce();

…lawwork-ai#408) Use vi.spyOn on streamReaderFrom's read method instead of reconstructing a duplicate reader object, addressing PR review feedback on clawwork-ai#534. Signed-off-by: Array Agent <advancedresearcharray@array.com> Co-authored-by: Cursor <cursoragent@cursor.com>

advancedresearcharray · 2026-06-09T21:26:56Z

/auto-cc

advancedresearcharray · 2026-06-09T21:27:24Z

Friendly follow-up: CI is green on the latest commit and this PR is ready for review/merge when you have a moment. Thanks!

samzong · 2026-06-10T17:49:11Z

Thanks @advancedresearcharray!
/lgtm
/approve

Closes clawwork-ai#408 The streaming maxSize enforcement (clawwork-ai#487), reader cancellation (clawwork-ai#523), and regression tests (clawwork-ai#534) are already on main. This commit closes the issue that remained open after squash merges omitted the closing keyword. Signed-off-by: advancedresearcharray <advancedresearcharray@github.com> Co-authored-by: Cursor <cursoragent@cursor.com>

Verified reader.cancel() + controller.abort() on streamed bytes exceeding maxSize, IPv6 pinned hostname bracketing, and 25 regression tests passing. Fix already landed on main via clawwork-ai#487, clawwork-ai#523, clawwork-ai#534; this commit closes clawwork-ai#408. Closes clawwork-ai#408 Co-authored-by: Cursor <cursoragent@cursor.com>

advancedresearcharray requested review from HiddenPuppy, mvanhorn and samzong as code owners June 8, 2026 21:42

advancedresearcharray force-pushed the fix/408-safefetch-memory-dos branch from de3b747 to 34b9ebb Compare June 8, 2026 21:42

gemini-code-assist Bot reviewed Jun 8, 2026

View reviewed changes

github-actions Bot added lgtm Looks good to me approved Approved for merge labels Jun 10, 2026

github-actions Bot merged commit d7c1a70 into clawwork-ai:main Jun 10, 2026
11 checks passed

advancedresearcharray deleted the fix/408-safefetch-memory-dos branch June 10, 2026 20:03

advancedresearcharray mentioned this pull request Jun 13, 2026

[Fix] Close #408 — safeFetch maxSize memory DoS (already on main) #537

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[Fix] safeFetch streaming maxSize memory DoS regression test (#408)#534

[Fix] safeFetch streaming maxSize memory DoS regression test (#408)#534
github-actions[bot] merged 2 commits into
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advancedresearcharray:fix/408-safefetch-memory-dos

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