---
id: wiki-2026-0508-sharedarraybuffer-보안-이슈와-cross-o
title: SharedArrayBuffer 보안 이슈와 Cross-Origin Isolation
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [SAB Security, COOP COEP, Cross-Origin Isolation]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [security, browser, web-platform, spectre]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: javascript
  framework: web-platform
---

# SharedArrayBuffer 보안 이슈와 Cross-Origin Isolation

## 매 한 줄
> **"매 SAB는 high-resolution timer 의 enabling primitive — Spectre 의 mitigation 위해 cross-origin isolation 의 required."**. 2018 Spectre 발표 후 매 brower 의 SAB disable 했고, 매 2020 부터 COOP+COEP+CORP triad 의 required for re-enable. 매 2026 modern WebAssembly threading / multi-threaded JS 의 prerequisite.

## 매 핵심

### 매 위협 모델
- Spectre v1 (bounds check bypass) 의 transient execution 의 cache side-channel leak.
- SAB + `Atomics.wait` 의 nanosecond-precision timer 제공 → cache hit/miss 의 distinguish 가능.
- Cross-origin attacker page 의 victim 의 secret data 의 read 가능 (same process).

### 매 mitigation triad
- **COOP** `Cross-Origin-Opener-Policy: same-origin` — window 의 cross-origin opener reference 의 cut.
- **COEP** `Cross-Origin-Embedder-Policy: require-corp` — sub-resource 의 explicit opt-in 의 require.
- **CORP** `Cross-Origin-Resource-Policy: same-origin|same-site|cross-origin` — resource owner 의 embedding policy 결정.

### 매 응용
1. WebAssembly threads (pthread, Rust async runtime).
2. FFmpeg.wasm / video encoding in browser.
3. Multi-threaded ML inference (ONNX.js, transformers.js).
4. Game engines (Unity, Unreal HTML5 export).
5. Excel-grade spreadsheet apps with worker pool.

## 💻 패턴

### COOP+COEP server headers (Express)
```javascript
app.use((req, res, next) => {
  res.setHeader('Cross-Origin-Opener-Policy', 'same-origin');
  res.setHeader('Cross-Origin-Embedder-Policy', 'require-corp');
  next();
});
```

### crossOriginIsolated check
```javascript
if (!self.crossOriginIsolated) {
  console.error('SAB unavailable — page not isolated');
} else {
  const sab = new SharedArrayBuffer(1024);
  const view = new Int32Array(sab);
  Atomics.store(view, 0, 42);
}
```

### Worker shared state
```javascript
const sab = new SharedArrayBuffer(4);
const counter = new Int32Array(sab);
const worker = new Worker('worker.js');
worker.postMessage(sab);
Atomics.add(counter, 0, 1);
Atomics.notify(counter, 0);
```

### CORP for static asset CDN
```nginx
location ~* \.(js|wasm|png)$ {
  add_header Cross-Origin-Resource-Policy "cross-origin";
}
```

### credentialless COEP (2024+)
```javascript
res.setHeader('Cross-Origin-Embedder-Policy', 'credentialless');
// cross-origin no-cors fetch without credentials — no CORP required
```

### iframe with allow attribute
```html
<iframe src="https://embed.example.com"
        allow="cross-origin-isolated"></iframe>
```

### Wasm threads init
```javascript
import init from './pkg/app.js';
await init();  // requires crossOriginIsolated for SAB-based threads
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| New app + threading needed | COOP same-origin + COEP require-corp |
| Legacy 3rd-party embeds | COEP credentialless (2024+) |
| Static asset CDN | CORP cross-origin header on all assets |
| No SAB needed | Skip isolation — broader compat |

**기본값**: `COOP same-origin` + `COEP require-corp` for threaded Wasm; credentialless if 3rd-party embeds.

## 🔗 Graph
- 응용: [[Web Worker (웹 워커)|Web-Workers]]
- Adjacent: [[CSP]]

## 🤖 LLM 활용
**언제**: SAB 의 use-case (Wasm threads, multi-thread JS) 의 enable 필요.
**언제 X**: simple SPA — overhead 의 worth 가 X.

## ❌ 안티패턴
- **CORP omission on CDN**: 매 silently break embedded resources.
- **COOP without COEP**: 매 SAB still blocked.
- **Naive credentialless adoption**: 매 cookie-based 3rd-party widgets break.

## 🧪 검증 / 중복
- Verified (web.dev coop-coep, MDN SharedArrayBuffer, Chrome blog).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — SAB security, COOP/COEP/CORP triad, Wasm threads enabling |