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The server socket of the built-in ws shim forwarded close(code, reason) straight to ServerWebSocket.close(). A code an endpoint may not send (999, 1004-1006, 1015, 2999, 5000, -1, NaN, a string) and a reason over 123 bytes went on the wire. Peers reported 1002, 1005 or 1007, and Chromium fails the connection for 1015 and for a reason cut inside a UTF-8 character. npm ws throws in Sender.close and sends nothing. Both socket classes now run the same checks with the same errors as npm ws when the socket is OPEN: TypeError for the code, RangeError for the reason. Like npm ws, the data is ignored without a code or without a length, and a typed array reason is sent as its bytes instead of "104,105". The client class threw the native DOMException before and now matches the server class.
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Status: reproduced on bun 1.4.3 with the script under Notes (every invalid |
WalkthroughThe WebSocket implementation now validates close codes and reasons, including typed-array inputs and the 123-byte limit. Client and mocked server sockets apply validation according to socket state. Tests cover invalid arguments, valid payloads, peer events, and close-frame transmission. ChangesWebSocket close validation
Suggested reviewers: Priority: ⬇️ Low — Defer the WebSocket close validation because it is a focused compatibility fix limited to argument checks and related tests. Merge Risk: 🟡 Moderate · up to The WebSocket close-validation behavior is not merge-ready because its changed test suite cannot parse. Remove the duplicate declaration before merging. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@test/js/first_party/ws/ws.test.ts`:
- Line 565: Remove the duplicate const cases declaration in the test block,
keeping a single cases variable with its existing type and initialization so the
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LGTM — focused npm-ws parity fix with the same error classes and messages as Sender.prototype.close.
What was reviewed:
closeReason()against npm wslib/validation.js/Sender.close: code ranges, 123-byte limit,data.lengthgate, and TypeError/RangeError text all match;new Buffer(view.buffer, off, len)mirrors the existingnormalizeDatapattern in this file.- Both socket classes route through the helper; server path validates before mutating
#state, so a caught throw leaves the socket OPEN as the test asserts. - Tests:
port: 0, events awaited viawithResolverswitherrorwired to reject, server closed infinally, boundary codes (999/1015/2999/5000 vs 1000/1014/3000/4999) and 123-vs-124-byte reason both covered.
Extended reasoning...
Overview
This PR ports npm ws's Sender.prototype.close argument validation into Bun's built-in ws shim (src/js/thirdparty/ws.js). Two helpers are added: isValidStatusCode (RFC 6455 §7.4 code ranges, matching npm ws lib/validation.js) and closeReason (throws TypeError for invalid codes, RangeError for reasons over 123 bytes, decodes typed-array views to UTF-8 first). Both BunWebSocket.prototype.close (client wrapper over the native WebSocket) and BunWebSocketMocked.prototype.close (server socket over Bun.serve) now call it, gated on readyState === OPEN so CONNECTING/CLOSING/CLOSED skip validation like upstream. New describe.each(["server","client"]) tests in test/js/first_party/ws/ws.test.ts exercise the full boundary matrix over real connections.
Security risks
None. This is input validation being added in the fail-closed direction — invalid close codes and over-long reasons that previously reached the wire (causing peer-side 1002/1007 errors or truncated UTF-8) now throw before any state change. No auth, crypto, filesystem, or privilege paths are touched. The data.length access can throw on null, but that matches npm ws exactly and is the parity target.
Level of scrutiny
Moderate is appropriate. Third-party shim parity changes are judged against the upstream package as the spec, and this PR cites the upstream source (lib/validation.js, Sender.prototype.close) and RFC 6455 §7.4/§5.5 for every constant. The helper is small and pure; the two call sites are one-liners. The new Buffer(arrayBuffer, offset, len) construction copies the existing normalizeData pattern six lines above in the same file, and $isTypedArrayView is the correct primordial-safe intrinsic. The server path calls closeReason before assigning #state = CLOSING, so a thrown error leaves the socket reusable — the first test pins this by asserting readyState === OPEN after 16 rejected calls, then confirming a subsequent valid close(4000, "ok") reaches the peer.
Other factors
Test coverage is thorough and follows the repo's harness conventions closely: port: 0, Promise.withResolvers awaiting the actual close event with error wired to reject, try/finally server cleanup, describe.each for the client/server matrix, Buffer.alloc(n, fill).toString() instead of .repeat, and exact error-class-plus-message assertions rather than bare toThrow(). Boundaries are covered on both sides (1014/3000/4999 pass; 1015/1016/2999/5000 fail; 123-byte reason passes, 124 fails) and the "peer sees the later valid close" assertion proves the invalid attempts sent nothing on the wire. No CODEOWNERS cover these paths, no prior reviewer objections exist, and the bug hunt ran to a dry streak with no findings.
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Updated 9:58 AM PT - Sep 8th, 2026
✅ @robobun, your commit cace07f6e037fa95fb9f35a40356e015c63f4b55 passed in 🧪 To try this PR locally: bunx bun-pr 42011That installs a local version of the PR into your bun-42011 --bun |
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Problem
wsshim, a server connection'sws.close(code, reason)reachedServerWebSocket.close()unchecked.close(999),close(1015),close(-1)andclose(1000, "é".repeat(70))each put a Close frame on the wire. Peers report 1002, 1005 or 1007, and Chromium fails the connection for 1015 and for a reason cut inside a character.Sender.prototype.closeand sends nothing: aTypeErroroutside 1000-1003, 1007-1014 and 3000-4999, aRangeErrorfor a reason over 123 bytes. The shim's client class threw aDOMExceptioninstead, and sent aUint8Arrayreason as"104,105".Fix
closeReason()insrc/js/thirdparty/ws.jsports those checks with the same errors. Both socket classes run it on an OPEN socket before any state change, so a caught error leaves the socket usable.datais ignored without a code or without alength, a typed array reason is sent as its bytes, and a socket that is not OPEN checks nothing.ServerWebSocket.close()itself (ServerWebSocket.close: cut a long reason on a UTF-8 character boundary #41665 covers its UTF-8 cut, a range check there changesBun.serve). Found by a parity audit, not a user report.test/js/first_party/ws/ws.test.ts, block "close() arguments" (all four fail on 1.4.3), plus the otherwssuites.Background
"ws"always resolves to the shim. Its server socket sits on aBun.servewebsocket, where uWSend()casts the code touint16_tand cuts the reason at byte 123. Its client socket wraps the globalWebSocket, which checks the same codes since websocket: validate close() arguments and reject unmasked client frames #32820.Notes
Repro,
bun shimclose.mjswith nonode_modulesagainstnode shimclose.mjswith ws 8.18.3:bun 1.4.3: every call returns. The peer sees 1002 for 999, 1004, 1015, 1016, 2999, 5000, 65535, 100000 and -1, 1005 for 1005, 1006 and NaN, a reason cut to 123 bytes for the 200-byte case,
1007for"é"×70,"104,105"for theUint8Arrayand"42"for42.close("1000")threwclose requires a numeric code or undefinedand left the socket in CLOSING with the connection open.node 26 + ws 8.18.3:
TypeErrorfor the 13 code cases,RangeErrorfor the two long reasons.close(undefined, long)sends an empty Close frame, theUint8Arrayarrives ashi,42is ignored,close(4000, "ok")arrives as given. With this change the shim matches that table, except that a no-codeclose()still sends code 1000 where npm ws sends an empty Close frame (the peer sees 1005). That difference existed before and is not touched here.npm ws sets
_readyState = CLOSINGbeforeSender.closethrows, which leaves a socket whoseclose()no longer does anything. The shim checks first, so the state is unchanged after a throw. The first test pins that (readyState 1, thenclose(4000, "ok")reaches the peer).Client class before this change: an OPEN socket threw
InvalidAccessErrororSyntaxError(DOMException) from the nativeclose(),close("1000")was accepted as 1000, and a CONNECTING, CLOSING or CLOSED socket also threw for a bad code. npm ws only checks on an OPEN socket: CONNECTING aborts the handshake, CLOSING and CLOSED return. The client class now does the same by calling the nativeclose()without arguments in those states. The native check from #32820 stays as it is underneath.A typed array reason is decoded to UTF-8 before the length check, so the 123-byte limit applies to the bytes that go on the wire. For a view that holds invalid UTF-8 this differs from npm ws, which sends the raw bytes.
#32820 added the same code set to the native client
close()and namedServerWebSocket#close()as not addressed. This change covers thewsside of that. #41665 is the native-side complement for the reason. Overlap with open PRs: #35031 (WHATWG range for the globalWebSocket.close()) carries an older version of the code check for both shim classes, without the reason check; itsws.jshunks are superseded by this. #39802 rewrites the server socket close lifecycle and touches the sameclose()method;closeReason()has to run before its pending-close bookkeeping, otherwise the conflict is mechanical.Suites run on the debug build:
test/js/first_party/ws/ws.test.ts(69 pass),ws-upgrade-events.test.ts,ws-proxy.test.ts,test/js/node/http/node-http-with-ws.test.ts,test/js/web/websocket/websocket-client.test.ts,websocket-close-connecting.test.ts,websocket-buffered-amount.test.ts,test/regression/issue/{32734,3613,012040,26358,29684,03844}.Self-reviewed: the review asked for the client class to go through the same helper and for the PR text to name the related PRs; both done.
[human-review] gate passed · iteration 0 · 2 files touched
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passes on PR (with fix)
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evidence per changed file
root cause · written by the author bot
Bun's built-in
wsshim forwardedclose(code, reason)straight to the underlying socket without running the argument checks that npm ws performs inSender.prototype.close, so codes an endpoint may not send (999, 1004-1006, 1015, 1016, 2999, 5000 and out-of-range values) and reasons longer than 123 bytes were written to the wire, where peers and real browsers rejected them as protocol errors or truncated the reason mid-codepoint. The fix adds upstream-matching validation helpers that reject invalid status codes with aTypeErrorand over-long reasons with aRangeError, and routes bot…