Add btoa, atob, and Buffer globals to workflow VM context#1520
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…ine context Slack-Thread: https://vercel.slack.com/archives/CDSJDH8QH/p1774470115717019?thread_ts=1774470115.717019&cid=CDSJDH8QH Co-authored-by: Pranay Prakash <1797812+pranaygp@users.noreply.github.com>
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🧪 E2E Test Results❌ Some tests failed Summary
❌ Failed Tests🌍 Community Worlds (58 failed)mongodb (2 failed):
redis (2 failed):
turso (54 failed):
Details by Category✅ ▲ Vercel Production
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📊 Benchmark Results
workflow with no steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 1 step💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 10 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 25 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 50 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Promise.all with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Promise.all with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Promise.all with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Promise.race with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Promise.race with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Promise.race with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 10 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 25 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 50 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 10 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 25 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) workflow with 50 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) Stream Benchmarks (includes TTFB metrics)workflow with stream💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) stream pipeline with 5 transform steps (1MB)💻 Local Development
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🔍 Observability: Next.js (Turbopack) 10 parallel streams (1MB each)💻 Local Development
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🔍 Observability: Next.js (Turbopack) fan-out fan-in 10 streams (1MB each)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) SummaryFastest Framework by WorldWinner determined by most benchmark wins
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Pull request overview
Exposes base64 helpers (atob, btoa) and Node’s Buffer in the workflow VM sandbox so workflow code can build/parse base64 payloads (e.g., Basic Auth headers) while running under packages/core’s deterministic VM context.
Changes:
- Add
g.atob/g.btoabindings to the VM context globals. - Add
Bufferto the VM context globals for Node-style base64 and binary manipulation. - Add new unit tests validating base64 encode/decode and Basic Auth-style usage.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| packages/core/src/vm/index.ts | Exposes atob, btoa, and Buffer in the sandboxed vm.Context. |
| packages/core/src/vm/index.test.ts | Adds tests covering atob/btoa/Buffer base64 behavior and a Basic Auth-style scenario. |
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| // Node.js Buffer for base64 encoding/decoding and binary data manipulation | ||
| (g as any).Buffer = Buffer; |
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Exposing the full Node Buffer into the deterministic sandbox allows Buffer.allocUnsafe(...) / Buffer(...) / new Buffer(...), which can return uninitialized memory. That is both a potential data-leak vector and a source of non-determinism (buffer contents depend on process heap state), undermining the goal of createContext.
Consider exposing a "safe" Buffer wrapper/proxy that (a) routes numeric allocations through Buffer.alloc (zero-filled), (b) disables/overrides allocUnsafe/allocUnsafeSlow, and ideally (c) throws on deprecated Buffer(number) usage. Add a small test asserting unsafe allocation paths are not available or are deterministic (zero-filled).
Suggested change
| // Node.js Buffer for base64 encoding/decoding and binary data manipulation | |
| (g as any).Buffer = Buffer; | |
| // Node.js Buffer for base64 encoding/decoding and binary data manipulation. | |
| // Expose a "safe" Buffer wrapper to keep the sandbox deterministic and avoid | |
| // uninitialized memory via allocUnsafe / deprecated numeric constructors. | |
| const SafeBuffer: typeof Buffer = new Proxy(Buffer, { | |
| // Handle direct calls like Buffer(...) | |
| apply(target, thisArg, argArray: any[]) { | |
| const [arg0, ...rest] = argArray; | |
| if (typeof arg0 === 'number') { | |
| // Route numeric constructor usage to zero-filled allocation | |
| return Buffer.alloc(arg0); | |
| } | |
| return Reflect.apply(target as any, thisArg, argArray); | |
| }, | |
| // Handle construction like new Buffer(...) | |
| construct(target, argArray: any[], newTarget) { | |
| const [arg0, ...rest] = argArray; | |
| if (typeof arg0 === 'number') { | |
| // Route numeric constructor usage to zero-filled allocation | |
| return Buffer.alloc(arg0); | |
| } | |
| return Reflect.construct(target as any, argArray, newTarget); | |
| }, | |
| get(target, prop, receiver) { | |
| if (prop === 'allocUnsafe' || prop === 'allocUnsafeSlow') { | |
| // Disable unsafe allocation paths inside the deterministic sandbox | |
| return function () { | |
| throw new Error('Buffer allocUnsafe methods are disabled in this sandbox'); | |
| }; | |
| } | |
| return Reflect.get(target as any, prop, receiver); | |
| }, | |
| }); | |
| (g as any).Buffer = SafeBuffer; |
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overkill for now but worth reconsidering in a future update
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VaguelySerious
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LGTM. Copilot might have a point about preventing allocUnsafe, though I personally can't tell. I think you could do a follow-up query to validate that
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Enables base64 encoding and decoding inside workflow functions by exposing
btoa,atob, andBufferin the sandboxed VM context.Requested by @Justin Sanford and @Walker Frankenberg for creating basic auth headers in workflows (stream.new migration to WDK).
What changed
g.btoaandg.atobfrom globalThis for Web API base64 encoding/decodingBufferfor Node.js-style base64 operations and binary data manipulation