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… zeros The HTTP parser had one error value for every Content-Length failure, and node:http mapped it to HPE_UNEXPECTED_CONTENT_LENGTH. Node uses that code only for a second Content-Length field. An empty, non-numeric, or oversized value is HPE_INVALID_CONTENT_LENGTH. The parser now has one error value for each failure. It parses each Content-Length value in the header scan, in wire order, like llhttp. So the first bad field decides the error, and a bad value is reported before a Transfer-Encoding conflict or a missing Host. node:http sets err.reason and the message from the llhttp reason strings, for example "Parse Error: Empty Content-Length". The value is parsed by its digits. So a value with leading zeros that is longer than 18 bytes is now accepted by Bun.serve and node:http. Node accepts it too. The upper limit stays at STATE_SIZE_MASK. A second field with the same value is still accepted.
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Reproduction: a raw socket sends
With this branch, all four match node. The PR body has the table of changed rows, and the rows that still differ. |
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Updated 5:28 AM PT - Oct 3rd, 2026
❌ @robobun, your commit 95eda28 has 2 failures in
🧪 To try this PR locally: bunx bun-pr 41234That installs a local version of the PR into your bun-41234 --bun |
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Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review. WalkthroughThe HTTP parser validates ChangesContent-Length handling
Suggested reviewers: Priority: ⬇️ Low Merge Risk: 🔵 Low · up to Malformed Content-Length requests are now rejected with Node-compatible codes and reasons. One narrow gap remains: when Transfer-Encoding comes before an invalid Content-Length, the reported error reason differs from Node's. The request is still rejected, so this is a minor compatibility difference that can be followed up separately. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In `@packages/bun-uws/src/HttpParser.h`:
- Around line 1224-1225: Update the HTTP framing validation around
parseContentLength and the later Transfer-Encoding check to preserve wire-order
error precedence, so a Content-Length after chunked Transfer-Encoding reports
the later-field rejection rather than an earlier parse error. Track field order
or validate framing headers in a single wire-order pass, and add regression
coverage for the reverse-order case.
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packages/bun-uws/src/HttpParser.hsrc/js/node/_http_server.tstest/js/bun/http/request-smuggling.test.tstest/js/bun/test/parallel/test-http-should-emit-clientError-when-Content-Length-is-invalid.tstest/js/node/http/node-http-transfer-encoding.test.ts
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About the wire-order finding ( I probed six requests where
To match Node here, the parser must reject a |
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I reviewed this PR and didn't find any bugs. Because it changes the Content-Length parsing and error-ordering in the shared uWS HTTP parser — the request-smuggling defense path for both Bun.serve and node:http — a human look is still worthwhile.
What was reviewed:
parseContentLengthoverflow math:result ≤ STATE_SIZE_MASK(2⁵⁹−1) at each iteration entry, soresult*10+9 < 2⁶³— no uint64 wrap before the bound check.- Acceptance surface: the only newly-accepted shape is a >18-byte all-digit value that fits under
STATE_SIZE_MASK(leading zeros); every other previously-rejected request still returns 400, just with a differentHttpParserError. toUnsignedIntegerhas no other callers; the mirrored TS enum in_http_server.tsmatches the C++ values, and both$HPE_*codes were already registered inErrorCode.ts.- Duplicate-field ordering: empty second field → EMPTY, non-empty differing second field → DUPLICATE, matching the llhttp probe table in the description and covered by the new
test.eachrows.
Extended reasoning...
Overview
This PR splits the single HTTP_PARSER_ERROR_INVALID_CONTENT_LENGTH into four distinct parser errors (invalid character, empty, overflow, duplicate) so node:http's clientError can report the same err.code/err.reason/err.message as Node's llhttp. In packages/bun-uws/src/HttpParser.h, toUnsignedInteger (18-char hard cap, UINT64_MAX sentinel) is replaced by parseContentLength, which returns a typed error and bounds the value against STATE_SIZE_MASK per digit. The Content-Length header scan now parses the first field eagerly and reports its error before the Transfer-Encoding/Host checks, matching llhttp's wire-order reporting. src/js/node/_http_server.ts adds three enum values and maps each to the exact llhttp code and reason string, plus sets err.reason. Tests cover the new error shapes and the leading-zeros framing case in both Bun.serve and node:http.
Security risks
Content-Length parsing is the core of HTTP/1.1 request-smuggling defense, so any relaxation matters. The one relaxation here is dropping the 18-character cap in favor of a numeric bound: a value like 0000000000000000005 is now accepted and framed as 5 bytes. RFC 9110 8.6 defines Content-Length as 1*DIGIT, so leading zeros are valid, and Node/llhttp already accept them — a compliant upstream proxy would parse the same value, so this does not introduce a framing disagreement. Every other previously-rejected request remains rejected; the only observable change is which HttpParserError code is attached to the 400. The reordering (CL parse error now fires before the TE/Host checks) changes which error the client sees on doubly-invalid input but never turns a rejection into an acceptance. The overflow check is sound: since result ≤ 2⁵⁹−1 at each loop entry, result*10+9 cannot wrap uint64 before the > STATE_SIZE_MASK test, and the resulting remainingStreamingBytes cannot collide with the chunked-encoding flag bits.
Level of scrutiny
High. This is the shared HTTP parser that frames request bodies for both Bun.serve and node:http, and the changed lines sit directly inside the smuggling-prevention block. Per the review guidelines, security-sensitive parser changes should get a human sign-off even when the automated review finds nothing. The change is small and well-reasoned (the PR description includes a thorough Node-vs-before-vs-after probe table and explicitly names the two behavioral divergences left unaddressed), which lowers risk, but does not remove the need for a maintainer familiar with the uWS parser to confirm the acceptance-surface delta is intended.
Other factors
toUnsignedInteger has no remaining callers (grep confirms), so its removal is clean. Both $HPE_INVALID_CONTENT_LENGTH and $HPE_UNEXPECTED_CONTENT_LENGTH were already registered in src/jsc/bindings/ErrorCode.ts, so the builtin change needs no codegen update. The mirrored HttpParserError enum in _http_server.ts matches the C++ values (18/19/20). Tests follow the harness conventions: port: 0/listen(0), Promise.withResolvers with error/close wired to reject, test.each for the parameter matrix, and the leading-zeros test asserts exact framing (body = "hello", pipelined GET dispatched) rather than just non-rejection. The updated test-http-should-emit-clientError-when-Content-Length-is-invalid.ts corrects an existing assertion that was checking for the wrong (non-Node-matching) code.
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…it is exact parseContentLength() takes acceptLong. node:http passes true and reads a value longer than 18 bytes by its digits, like llhttp. Bun.serve passes false and rejects such a value, as before this branch. A value of up to 18 bytes takes one loop and one limit check, the same work as before. onServerClientError() sets err.reason on every arm whose parser error maps to exactly one llhttp reason: the Content-Length arms, and the arms for HPE_LF_EXPECTED, HPE_CLOSED_CONNECTION, HPE_PAUSED_H2_UPGRADE, HPE_INVALID_EOF_STATE, HPE_HEADER_OVERFLOW and HPE_CHUNK_EXTENSIONS_OVERFLOW. The other arms stand for several llhttp reasons and stay without one.
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline finding, I also checked two things: the removed post-parse > STATE_SIZE_MASK guard in HttpParser.h — contentLength is only ever written by parseContentLength, which rejects anything above the mask on both the short and long branches, and remainingStreamingBytes is assigned from it only when contentLengthStringLen is non-zero, so the chunked flag bits remain unreachable; and the HttpParserError mirror — the enum lives only in HttpParser.h and _http_server.ts, and both gained the three new values with matching numbers.
Extended reasoning...
The change replaces the uWS parser's Content-Length integer parsing with a per-cause error enum and maps those causes to llhttp codes and reasons in node:http's clientError path; it touches request-framing validation shared by Bun.serve and node:http. The two concrete concerns ruled out here were the deleted STATE_SIZE_MASK safety check (covered by the new parser on all paths) and the enum mirror consistency across the two files.
node:http: 2^59 - 1 is dispatched and 2^59 overflows, as an 18-byte value and as a zero-padded 19-byte value. Bun.serve: an 18-byte zero-padded value is accepted next to the 19-byte rejection.
robobun
changed the title
parseContentLength() rejects every value longer than 18 bytes again, for Bun.serve and for node:http, as on main. So this branch changes which error a rejected request reports, and not which requests are accepted. A long value is an invalid character if a non-digit comes before the overflow, like llhttp, and an overflow otherwise.
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I reviewed the latest push and found no bugs, but because this reorders and rewrites Content-Length validation in the shared uWS parser (the request-smuggling defense for both Bun.serve and node:http), a human look is still worthwhile.
What was reviewed:
parseContentLengtharithmetic: 18 digits stay below 2^63 so the single post-loopSTATE_SIZE_MASKcheck is sufficient; the >18-byte branch breaks once past 2^59-1 soresultcannot wrap, and both branches surface a non-digit before the overflow like llhttp.- The move of parsing into the header-scan loop: the empty check now runs on every occurrence, the old
UINT64_MAX/STATE_SIZE_MASKguard at theremainingStreamingBytesassignment is fully replaced,toUnsignedIntegerhas no remaining callers, and the C++ and TSHttpParserErrortables are in sync (18/19/20); the error code is consumed only byonServerClientError. - Suite assertions on the old codes: the only remaining
HPE_UNEXPECTED_CONTENT_LENGTHexpectations are duplicate-field cases, which still map there. - One thing for the human reviewer: after commit 95eda28 the PR description is stale — it says node:http reads a value longer than 18 bytes by its digits and "now dispatches" a long zero-padded value, but the code rejects any >18-byte value as
Content-Length overflowfor both servers (and the new tests assert that), so the description should be updated to match.
Extended reasoning...
The change replaces the uWS HTTP parser's Content-Length helper with a typed-error parser, moves the parse into the header scan ahead of the Transfer-Encoding and Host checks, adds three enum values mirrored in src/js/node/_http_server.ts, and sets err.reason on the single-reason clientError arms, with table-driven tests in node-http-transfer-encoding.test.ts and request-smuggling.test.ts. It touches the request-smuggling defense on untrusted wire data shared by Bun.serve and node:http, which is a security-sensitive surface. The arithmetic, enum sync, dead-code removal and old-behavior assertions all check out, and prior inline feedback (limit-boundary tests) was addressed by later commits. Deferring rather than approving because the parser is security-sensitive and the latest commit changed acceptance behavior in a way the PR description no longer reflects.
Problem
node:httpserver emitsclientErrorwithHPE_UNEXPECTED_CONTENT_LENGTHfor every badContent-Length. Node uses that code only for a second field, andHPE_INVALID_CONTENT_LENGTHfor an empty, non-numeric, or oversized value. Node setserr.reason.packages/bun-uws/src/HttpParser.h:1305,:1310,:1424on main 468efac).src/js/node/_http_server.ts:1357maps it toHPE_UNEXPECTED_CONTENT_LENGTH("Parse Error").Fix
err.reasonis set where the parser error maps to exactly one llhttp reason: the Content-Length arms and six single-reason codes.node-http-transfer-encoding.test.tsandrequest-smuggling.test.ts(the new tests fail on main). Self-reviewed: 11 concerns raised, 8 addressed. Not taken: rejecting a same-value second field, HTTP/3, an llhttp-based classifier (node:http: clientError code, reason and message still differ from Node for some bad requests #44542).Background
clientErroris thehttp.Serverevent for a rejected request. One uWS parser servesBun.serveandnode:http.reasonon every arm: Node gives another reason for 17 of 62 probed requests. Considered parsing long zero-padded values like Node: that changes which requests are accepted, so it is in node:http: clientError code, reason and message still differ from Node for some bad requests #44542.Downsides
Content-Lengthwith noHostnow firesclientError, as in Node (before: the missing-Host 400, no event).Content-Lengthruns 1 more instruction (52 against 51 for1234), with equal compares and branches.Content-LengthafterTransfer-Encodingreports the value fault, and six coarse arms have noerr.reason.Notes
Probe. One script sends 62 bad requests on a raw socket to
http.createServer()and logs the events witherr.code,err.reasonanderr.message. It ran on node v26.3.0, on a debug build of main 468efac, and on a debug build of this branch. Full matches with Node (events, code, reason, message): main 0 of 62, this branch 11 of 62. In 3 more rows only the early-close message differs.Rows that this PR changes (the
HPE_prefix is left out):Content-Length:(empty)Content-Length: abcContent-Length:23 digitsContent-Length: 5then6Parse ErrorParse Error: Invalid EOF stateHPE_CLOSED_CONNECTIONneeds a pending first response, so the probe does not reach it. The test table covers it. Each row of the two test tables was also run on node v26.3.0 with the same bytes, and each one matches.Rows that still differ from Node. This PR does not change these. #44542 tracks them, with the rows of the six coarse arms.
Content-Length: 5twice5,5, then an empty valueclientErrorTransfer-Encoding: chunked, thenContent-Length: xor emptyTransfer-Encoding: chunked, thenContent-Length: 5and6Transfer-Encoding: chunked, thenContent-Length: 5Content-Length: 5, thenTransfer-Encoding: chunkednode:httpis a new rejection rule, so this PR does not do it.remainingStreamingByteskeeps the chunked state flags in its top bits. Node's limit is 2^64 - 1, with any number of leading zeros. An earlier version of this PR parsed long zero-padded values innode:http. That changes which requests are accepted, so it is out of this PR.clientErrornow, because the value is checked first.err.reason: chunk size, transfer-encoding, request line, method, version, header token. One parser value stands for several llhttp reasons there. In the probe, Node gives another reason than the arm's text for 17 rows, and another code for 10. Two of the texts ("Expected HTTP/", "Invalid header token encountered") are not llhttp strings.Parse Errorand the error has norawPacket. Both Bun server paths (this one andhttp1_server_fallback.ts) buildParse Error: Invalid EOF state, so this PR leaves the message.err.bytesParsedis set on 3 of the arms, as before.Designs weighed. Four independent reviews of the same evidence agreed on
err.reasonfor exactly the arms with one llhttp reason. Classifying only inside the old reject branches was rejected: it keeps the number parse behind the Host check, so a bad value with no Host gets noclientError. A table that names the llhttp rule at every rejection site, or a pass of the rejected head through the vendored llhttp, is a larger change that needs a maintainer's decision first (#44542).Cost measurement.
perfandvalgrindare not available in the build container, andperf_event_openis not permitted. So a standalone copy of both code paths (main's empty check,toUnsignedIntegerand limit check, against this branch'sparseContentLengthcall) was built with clang 23 at-O2and-O3and single-stepped underptracebetween two breakpoints. Instructions for one valid value:512344294967296576460752303423487The digit loop is 10 instructions in both. The one extra instruction is a register move: main stores the number before the limit check, and this branch stores it after. A request with no Content-Length takes the same path as on main (the bloom filter skips the scan).
Related.
HttpParser::toUnsignedInteger, which this PR replaces withparseContentLength.Tests run on the ASAN debug build.
node-http-transfer-encoding.test.ts140 pass,request-smuggling.test.ts93 pass.src/andpackages/: 20 of 138 fail in the first file and 1 of 92 in the second, each within 100 ms. On that version's own build:http-server-chunking.test.ts13 pass,hspec.test.ts1 pass, and the updatedtest-http-should-emit-clientError-when-Content-Length-is-invalid.tsand upstreamtest-http-double-content-length.js,test-http-header-overflow.js,test-http-parser-finish-error.jspass.[human-review] gate passed · iteration 0 · 5 files touched
fails on main (without fix)
passes on PR (with fix)
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gate history · 1 passed · 0 rejected · iteration 0
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