tls: report a fatal post-handshake SSL error over a Duplex or a named pipe

[robobun]

Problem

• tls.connect({ socket: <Duplex> }), node:tls over a Windows named pipe, and the Http2SecureServer raw-socket upgrade end cleanly when a TLS record fails after the handshake. Node emits ERR_SSL_<REASON>, for example ERR_SSL_DECRYPTION_FAILED_OR_BAD_RECORD_MAC.
• The cause is SSLWrapper::handle_reading (src/uws/lib.rs). On SSL_ERROR_SSL it clears the error queue, drops the alert, and closes with no error.

Fix

• handle_reading takes the error before the queue is cleared, sends the alert, and calls the new Handlers::on_ssl_error before on_close.
• UpgradedDuplex and WindowsNamedPipe forward it to the new TLSSocket::on_ssl_error, which calls the error handler with a third argument true.
• node:net then emits the error and keeps the socket, like Node's onerror.
• Verified: 9 new cases in node-tls-connect.test.ts, node-tls-namedpipes.test.ts, node-http2-upgrade.test.mts. They fail on main and pass on Node.js v26.3.0.

Background

• SSLWrapper runs BoringSSL over memory BIOs for transports that are not sockets.
• A fatal SSL_read leaves its reason on OpenSSL's error queue and its alert in the write BIO. Nothing pumps that BIO after a close.
• Weighed: stay stacked on tls: report a fatal TLS error that arrives after the handshake #41272. It no longer builds on main, so this PR carries the delivery code both need.

Downsides

• A client TLSSocket over a Duplex with no 'error' listener now throws an uncaught exception, as Node does. Before, it closed silently.
• Bun.connect and Bun.listen with tls on a Windows named pipe: error now runs before close, with a third argument true. A maintainer must decide this.
• Release binary (linux x64): text +966 bytes, file size unchanged. Each SSL_read in SSLWrapper now starts with one ERR_clear_error().

Notes

History

• This replaces the earlier content of this PR, which was stacked on tls: report a fatal TLS error that arrives after the handshake #41272. tls: report a fatal TLS error that arrives after the handshake #41272 no longer merges into main: it has text conflicts in internal.h and node-tls-server.test.ts, and its on_ssl_error does not compile there because EventLoop::run_callback now takes a ContextId first.
• The first iteration was tls: report a fatal post-handshake SSL error over a Duplex instead of a clean close #41507. It was merged into the branch of tls: report a fatal post-handshake SSL error instead of a clean close #41463, which is closed without a merge, so it never reached main.
• tls: do not close the SSL wrapper from a write made during a fatal read #42326 (merged) is the write_data guard that was split out of this work. The 'data' listener case here depends on it.

What this PR shares with #41272

• The fetch and WebSocket proxy tunnels pass on_ssl_error: None. They still get the alert flush.
• The close that follows the error gives 'end' and 'close' with hadError false.
• NewSocket::on_ssl_error (socket_body.rs) and the two tlsFatal branches in net.ts are the text of tls: report a fatal TLS error that arrives after the handshake #41272, with ContextId::NONE added for the new run_callback. Whichever PR lands second drops them on rebase.
• us_ssl_take_fatal_error() is the picker tls: report a fatal TLS error that arrives after the handshake #41272 has inline in us_internal_ssl_on_data: the first SSL-library entry on the queue, else the oldest. BoringSSL queues the cipher's BAD_DECRYPT ahead of the TLS reason. On main, SSLWrapper is its only caller.
• The tlsFatal branches do not destroy the socket. That is an exception to the "Post-handshake TLS errors still destroy the socket" item that node:tls,node:net: follow-ups from the v26.3.0 review (error routing, manualStart reads, handshake timeout, setSecureContext) #35006 kept on purpose. It is safe here because the native close follows the error at once, so no connection stays alive. An accepted tls.Server socket keeps its internal 'error' listener, so a server with no listener of its own gets no uncaught exception.

Not in this PR

• Plain tls.connect(port) and tls.createServer (the uSockets engine) still close with no error until tls: report a fatal TLS error that arrives after the handshake #41272. The two-engine loop in node-tls-connect.test.ts records that: the tls.connect rows of the two new cases are it.failing. tls: report a fatal TLS error that arrives after the handshake #41272 flips them.
• A fatal SSL_write in SSLWrapper after the handshake still closes with no error. Node fails that write with write EPROTO. It needs its own change.
• A failed SSL_shutdown closes with no error, which matches Node.
• The handshake-time exit (update_handshake_state) still clears the queue and closes without sending the sealed alert. node:tls: report the fatal TLS alert when a handshake over a Duplex fails #32929 covers its reason, nothing covers its alert yet.
• ssl_park_fatal_reason in openssl.c (the handshake-time park for uSockets sockets) still reports the oldest queue entry, so the same bad record during a TCP handshake is EPROTO with the cipher-layer text.
• SSL_do_handshake, SSL_write and SSL_shutdown in SSLWrapper still run with no queue clear before them. A stale entry there would make SSL_get_error report SSL_ERROR_SSL, as on main. I could not produce a stale entry from JS (failed context builds through Bun.connect and tls.connect, then a Duplex connect with a cached context), so there is no failing case for it yet.
• With a write pending, SocketHandlers2.error keeps the old path: the write callback gets the error and the socket is destroyed ('error', then 'close' with hadError true). Node gives 'error', then 'end'. The 'data' listener case asserts only the first event for that reason.

Repro

• A TCP proxy between a Duplex-wrapped client and tls.createServer. After secureConnect, write an application_data record (17 03 03 00 20 plus 32 bytes of 0x42) toward the client. Node v26.3.0: error ERR_SSL_DECRYPTION_FAILED_OR_BAD_RECORD_MAC. Bun on main: end, close false. With the fix: the same error, then end, close false.
• The other peer gets the alert as ERR_SSL_SSLV3_ALERT_BAD_RECORD_MAC (BoringSSL's name. OpenSSL 3 says SSL/TLS_ALERT_BAD_RECORD_MAC). The tests pick the name from process.features.openssl_is_boringssl.
• Named pipes on Windows without the fix: the peer whose read fails gets a clean close, the other peer gets EPIPE (no alert went out). With the fix both get their ERR_SSL_* error.
• Http2SecureServer fed by emit("connection", rawSocket): the server now gets sessionError with ERR_SSL_DECRYPTION_FAILED_OR_BAD_RECORD_MAC, the same as Node.

Tests

• node-tls-connect.test.ts: two cases in the two-engine loop (4 rows: the Duplex rows assert error, then end; the tls.connect rows are it.failing), one 'data' listener case, one server socket over a Duplex (the ServerHandlers branch).
• node-tls-namedpipes.test.ts: both peers on a named pipe, the bad record toward the client and toward the server.
• node-http2-upgrade.test.mts: the raw-socket upgrade. That file also runs itself under Node in CI.
• Node.js v26.3.0 ran a line-for-line port of the bun:test cases with node:assert, on Linux and on Windows. All pass. In the tests the peer ends after the socket under test reports its error. A peer that ends or destroys from its own 'error' handler loses its alert on Node on Windows.
• With src/ and packages/ from main, the four Duplex rows and the http2 case fail on Linux, and the two named pipe cases fail on the Windows canary.
• Other suites run: test/js/node/tls/ (connect, server, cert, upgrade, renegotiation, namedpipes), test/js/bun/net/socket.test.ts, test/js/bun/http/proxy.test.ts, test/js/web/websocket/websocket-proxy.test.ts, test/js/node/http2/node-http2.test.js. 913 pass. should not call drain before handshake needs www.example.com and also fails without the change.

Measurements

• Release builds of the merge base (36cd151) and the PR head, linux x64, size: text 80661004 to 80661970 (+966), data 110424 and bss 1822992 unchanged. Both files are 80827976 bytes.
• Per connection: one more function pointer (8 bytes) in ssl_wrapper::Handlers and in the owner's Handlers. Per SSL_read: one ERR_clear_error() before it (BoringSSL resets 16 queue slots), and one more branch where the read returns no data. No allocation, no syscall. This applies to the fetch and WebSocket proxy tunnels too.
• The clear makes the error that handle_reading takes belong to that read. openssl.c clears the queue at the start of us_internal_ssl_on_data for the same reason.
• 20000 echo round trips over a Duplex, 20 interleaved runs each: base median 793.5 ms, PR 769.5 ms. The noise floor (base against base) is 58 ms, so there is no difference above it. valgrind and perf are not installed here, so there is no instruction count.

Self-review

• Self-reviewed: 12 concerns raised, 9 addressed (rebuilt on main, one picker in openssl.c, the http2 upgrade path covered, a case that pins each net.ts branch, the uSockets gap recorded in the two-engine loop, the exclusions above, the node:tls,node:net: follow-ups from the v26.3.0 review (error routing, manualStart reads, handshake timeout, setSecureContext) #35006 exception named, a Windows run of the named pipe cases, the write_data guard sent to main as tls: do not close the SSL wrapper from a write made during a fatal read #42326). Not done: a tracking issue for the two mirrored engines, the alert flush on the handshake exit (node:tls: report the fatal TLS alert when a handshake over a Duplex fails #32929 edits the same lines), and the third-argument contract, which is a maintainer's call.

---

no test proof · iteration 4 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/node/tls/node-tls-namedpipes.test.ts

[robobun]

Status: reproduced with a TCP proxy that injects a bad application_data record toward a tls.connect({ socket: <Duplex> }) client after secureConnect. Bun on main: end, close false. Node v26.3.0: error ERR_SSL_DECRYPTION_FAILED_OR_BAD_RECORD_MAC. With this PR: the same error, then end.

This PR targets main (4 commits, 12 files). It was stacked on #41272 before. #41272 no longer merges into main, so this PR carries the on_ssl_error delivery code it shares with #41272. #42326 (the write_data guard split out of this work) is merged.

The nine new cases fail with src/ and packages/ from main, pass with this branch (Linux and Windows builds), and pass on Node.js v26.3.0 (Linux and Windows).

CI: the diff is green. In builds 121037 and 121052 every TLS, socket, proxy, and http2 suite passed on every lane, including the named pipe cases on Windows. The red lanes are test/js/bun/s3/s3.test.ts on the Linux x64 lanes, where the CI could not start its minio service (Failed to start service minio: Image quay.io/minio/minio:latest Pulling). That is reported separately and does not involve this change.

Open for a maintainer: the contract of the error handler's third argument (see the comment below).

[robobun]

The write_data guard in this PR is also a fix for a use-after-free that exists on main today (fetch with Upgrade and a streaming body through a CONNECT proxy, when the 101 and a bad TLS record arrive together). It is now #42326 against main, with a fetch-level regression test. If #42326 lands first, that hunk disappears from this PR on rebase. The three tests here still need it.

[claude]

I reviewed this PR and didn't find any bugs. Because it changes fatal-error handling in the TLS engine across an FFI boundary and adds a re-entrancy guard on a path the description names as a live UAF, a human look is still worthwhile.

What was reviewed:

• us_ssl_take_fatal_error() refactor vs. the inlined loop it replaces — same peek-oldest / return-first-ERR_LIB_SSL semantics, and the Rust caller still clears the queue afterward.
• handle_reading fatal path ordering: fatal_error flag set before the data callback, alert flushed via handle_writing, then on_ssl_error, then close, with a liveness check after each callback.
• write_data fatal short-circuit — returns ConnectionClosed before SSL_write, so a data-handler write-back can't re-enter handle_traffic and reach on_close under its own frame.
• Callback threading through all four SSLWrapper owners plus explicit None opt-outs on both proxy tunnels; tests use port: 0, local proxies, no sleeps, and race 'error' vs 'close' so the pre-fix clean close fails them.

Extended reasoning...

Overview

This PR makes the Rust SSLWrapper engine (TLS over a generic Duplex, Windows named pipes, and proxy tunnels) surface fatal post-handshake SSL_read failures as an ERR_SSL_* 'error' event and flush the outgoing alert to the peer, matching Node's behavior and the uSockets C path from the stacked #41272. The inlined error-queue picker in openssl.c is factored into us_ssl_take_fatal_error() and shared with the Rust engine via a new safe fn extern. ssl_wrapper::Handlers gains an optional on_ssl_error slot; handle_reading now captures the packed error before clearing the queue, flushes the write BIO, calls the new callback, and then closes. write_data short-circuits with ConnectionClosed once the fatal flag is set. The callback is threaded through UpgradedDuplex, DuplexUpgradeContext, WindowsNamedPipe, and WindowsNamedPipeContext into the existing TLSSocket::on_ssl_error; the fetch and WebSocket proxy tunnels opt out with None. Six tests are added across three existing suites (Duplex TLS connect, Windows named-pipe TLS, HTTP/2 upgrade).

Security risks

The change is in TLS error handling but only affects how a fatal condition is reported — it doesn't relax validation, alter certificate checks, or change what is accepted. The us_ssl_take_fatal_error() refactor is behavior-preserving against the inline loop it replaces (peek oldest, drain until first ERR_LIB_SSL entry, return that or the oldest). The alert flush sends bytes BoringSSL already sealed; no new plaintext is exposed. The new extern is declared safe fn with no arguments and touches only the calling thread's error queue. I don't see a security regression here, but TLS engine code is inherently security-sensitive and warrants human sign-off.

Level of scrutiny

High. This touches (a) a crypto/TLS engine, (b) an FFI boundary between uSockets C and the Rust ssl_wrapper, (c) re-entrancy on a path where callbacks can synchronously free the owner — the PR description itself names a live UAF on main that the write_data guard fixes, and (d) #[cfg(windows)]-gated code that only compiles on the Windows target. REVIEW.md flags memory-safety re-entrancy as the most-blocked category and explicitly calls out TLS/crypto paths. Per the approval guidelines, changes to crypto paths and complex cross-platform native code should not be auto-approved.

Other factors

The change is well-scoped and follows repo conventions closely: liveness (self.ssl.get().is_none() || self.flags.closed_notified()) is re-checked after every callback in the new fatal path, matching the surrounding pattern; the fatal flag is set before the data callback so the write_data guard is armed when a 'data' listener writes back; every SSLWrapper owner is updated in one PR (the "fix the whole class" rule), with tunnels explicitly opting out. Tests are added to existing files, use port: 0 / 127.0.0.1, spin up local TCP/pipe proxies to inject the forged record, race 'error' against 'close' via a Promise (no sleeps), branch the alert code name on process.features.openssl_is_boringssl so they hold on Node too, and cover client-side, server-side, and the data-handler-writes-back variant. No CODEOWNERS entries cover the changed paths. No prior reviews or outstanding objections are on the timeline. The bug hunt ran to dry_streak with no findings, but the combination of TLS, FFI, re-entrancy, and Windows-only code paths means a human reviewer should confirm the ordering and lifetime reasoning.

[robobun]

^{Updated 4:46 PM PT - Sep 26th, 2026}

❌ @robobun, your commit 6c43aed has 1 failures in Build #121052 (All Failures):

• test/js/bun/s3/s3.test.ts - code 1 on 🐧 13 x64-asan
• test/js/bun/s3/s3.test.ts - code 1 on 🐧 13 x64
• test/js/bun/s3/s3.test.ts - code 1 on 🐧 25.04 x64
• test/js/bun/s3/s3.test.ts - code 1 on 🐧 3.23 x64

---

🧪   To try this PR locally:

bunx bun-pr 42324

That installs a local version of the PR into your bun-42324 executable, so you can run:

bun-42324 --bun

[robobun]

Pushed fb9f53c: the write_data guard comment is now the same two lines as in #42326. The other comment-cop flags are one- or two-line doc comments on a handler field, an extern declaration, and the alert-flush branch; they state what the value is or why the branch exists, so they stay.

[claude]

Code review found no issues

No high-confidence issues detected in this change.

[robobun]

This PR now targets main and stands on its own. What changed, and one decision I need from a maintainer.

What changed

• tls: do not close the SSL wrapper from a write made during a fatal read #42326 merged, so the write_data guard is on main and is no longer in this diff.
• The base, tls: report a fatal TLS error that arrives after the handshake #41272, no longer merges into main: text conflicts in internal.h and node-tls-server.test.ts, and its on_ssl_error does not compile there because EventLoop::run_callback now takes a ContextId first. main's SSLWrapper also changed in nine commits since that base.
• So I rebuilt this branch on main. It carries the delivery code it shares with tls: report a fatal TLS error that arrives after the handshake #41272 (NewSocket::on_ssl_error and the two tlsFatal branches in net.ts), with the one-line change for the new run_callback. Whichever of the two PRs lands second drops those hunks on rebase.
• Tests: the two-engine loop in node-tls-connect.test.ts now has both cases for both engines. The Duplex rows assert error, then end. The plain tls.connect rows are it.failing, because the uSockets engine still closes with no error until tls: report a fatal TLS error that arrives after the handshake #41272. There is also a case for a server socket over a Duplex, which pins the ServerHandlers branch.
• All nine cases pass on Node.js v26.3.0, on Linux and on Windows.

Decision needed: the third argument of the error handler
TLSSocket::on_ssl_error calls the socket's error handler as error(socket, err, true), then the close follows. node:net uses the true to emit the error and keep the socket, like Node's onerror. The same call reaches the public error handler of Bun.connect and Bun.listen with tls on a Windows named pipe. Two effects there:

1. That handler now runs for a fatal TLS record after the handshake. Before, only close ran.
2. It gets a third positional argument that is not documented.

This is the contract #41272 proposes for every TLS socket. If you prefer a different one (for example an internal-only handler, or the error as the second argument of close), tell me and I will change on_ssl_error and the two net.ts branches. Everything in SSLWrapper stays the same either way.

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Walkthrough

The change captures fatal TLS read errors and forwards them through socket and Node.js TLS handlers. Tests cover malformed post-handshake records across TLS, Duplex, HTTP/2, and named-pipe connections.

Changes

Fatal TLS Error Reporting

Layer / File(s)	Summary
Capture and report fatal read errors packages/bun-usockets/src/crypto/openssl.c, src/uws/lib.rs	The TLS wrapper captures packed fatal errors, flushes pending output, and reports nonzero errors through an optional callback before closure.
Forward errors through socket handlers src/runtime/socket/socket_body.rs, src/runtime/socket/UpgradedDuplex.rs, src/runtime/socket/WindowsNamedPipe.rs, src/runtime/socket/WindowsNamedPipeContext.rs	Socket dispatch, upgraded duplex handlers, and named-pipe handlers forward SSL errors to TLS socket handling.
Deliver fatal errors to Node.js handlers src/js/node/net.ts, src/http/ProxyTunnel.rs, src/http_jsc/websocket_client/WebSocketProxyTunnel.rs	Node.js TLS handlers use the TLS error path for eligible fatal errors. Proxy tunnel handlers leave the SSL error callback unset.
Test fatal TLS error delivery test/js/node/http2/node-http2-upgrade.test.mts, test/js/node/tls/node-tls-connect.test.ts, test/js/node/tls/node-tls-namedpipes.test.ts	Regression tests check error codes and event ordering for malformed post-handshake records across TLS, Duplex, HTTP/2, and named-pipe connections.

Suggested reviewers: jarred-sumner

Priority: ➖ Normal

Merge Risk: 🔵 Low · up to 6c43a

A narrow re-entrant close path can suppress a fatal TLS error notification, although the connection still closes. This limits error reporting rather than leaving the connection usable in an invalid state, so the change is mergeable with awareness of this edge case.

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✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: reporting fatal post-handshake SSL errors for Duplex and named-pipe transports.
Description check	✅ Passed	The description explains the problem, implementation, scope, tradeoffs, and verification results. It does not use the template headings exactly, but it provides the required change summary and test ev…

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In @packages/bun-usockets/src/crypto/openssl.c:
- Around line 1799-1812: Clear the thread’s OpenSSL error queue immediately
before each Rust SSL_read call in handle_reading, including reads reached
through handle_traffic, so us_ssl_take_fatal_error cannot return a stale error
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• packages/bun-usockets/src/crypto/openssl.c
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• src/runtime/socket/UpgradedDuplex.rs
• src/runtime/socket/WindowsNamedPipe.rs
• src/runtime/socket/WindowsNamedPipeContext.rs
• src/runtime/socket/socket_body.rs
• src/uws/lib.rs
• test/js/node/http2/node-http2-upgrade.test.mts
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[claude]

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 the new alert flush in handle_reading (src/uws/lib.rs:1224-1231): handle_writing can run the owner's write handler (user Duplex _write), but handle_traffic is guarded by its Traffic state so a nested write cannot re-enter handle_reading, and the ssl/closed_notified re-check after it covers synchronous teardown. Reusing buffer for the ciphertext there is safe because any decrypted bytes were already handed to trigger_data_callback above.

Extended reasoning...

The change adds a fatal post-handshake SSL_read error path to the Rust ssl_wrapper (used by TLS-over-Duplex, Windows named pipes, and the fetch/WebSocket proxy tunnels), a C helper in openssl.c that picks the error off the BoringSSL queue, new on_ssl_error trampolines through UpgradedDuplex/WindowsNamedPipe/socket_body, and two tlsFatal branches in node:net that emit via _emitTLSError without destroying. It touches TLS error delivery, not credentials or auth decisions. A verified finding about the Bun.connect/Bun.listen named-pipe path silently dropping the error is being posted inline, and the Windows-only code is not type-checked on this Linux checkout, so a human look is still warranted.

[robobun]

Pushed 6c43aed for the review point on the error queue: handle_reading now clears the queue before each SSL_read, so the error it takes after a fatal read belongs to that read. openssl.c clears at the start of us_internal_ssl_on_data for the same reason. Measured again on release builds of the merge base and the new head: text +966 bytes, file size unchanged, and the Duplex echo loop shows no difference above the noise floor (the PR body has the numbers).

On the optional point about a socket with no error handler: that is deliberate. A fatal TLS record is an error the remote peer chooses to cause, so a socket with no handler gets only the close and cannot be turned into an uncaught exception by its peer. It belongs to the same contract decision as the third argument.

[claude]

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 the two new re-entrant steps in SSLWrapper::handle_reading (src/uws/lib.rs): the alert flush via handle_writing re-reads self.ssl on every loop iteration and the caller re-checks ssl.get().is_none() || closed_notified() after it and after trigger_ssl_error_callback, so a peer that closes the wrapper from inside the write or error callback does not reach the shutdown/close on freed state. The server-side tlsFatal branch in net.ts is only reachable after the !_secureEstablished destroy branch, matching the client-side _secureEstablished guard.

Extended reasoning...

The change adds an on_ssl_error slot to the Rust SSLWrapper handlers, flushes the sealed alert and reports the packed BoringSSL error to node:tls before the close, and wires it through the Duplex and Windows named-pipe owners with tests. It touches TLS error-reporting code but no auth, credential, or verification logic. The one confirmed finding is pre-existing and posted inline; this note records the re-entrancy paths that were examined and ruled out.

[robobun]

On the review's note about the other SSL_* calls in SSLWrapper (SSL_do_handshake, SSL_write, SSL_shutdown): they are unchanged from main and I left them out of this PR. SSL_read is the one site where this PR takes an entry off the error queue and reports it, so the clear is needed there. For the other three I could not produce a stale queue entry from JS to prove a change (failed context builds through Bun.connect and tls.connect, then a Duplex connect with a cached context: the handshake succeeded each time). They are in the "Not in this PR" list in the PR body.

[robobun]

Two facts for the open decisions on this PR, at the head 6c43aed.

1. The ERR_clear_error() before each SSL_read has no effect

• BoringSSL empties the error queue of the thread at the entry of SSL_read. ssl_read_impl starts with ssl_reset_error_state (ssl/ssl_lib.cc:75, :836 at the pinned commit 41bf9b59c2). SSL_write (:952), SSL_do_handshake (:721) and SSL_shutdown (:1020) start with the same call.
• Probe: a C++ program linked to the BoringSSL objects of a debug build. Two peers over memory BIOs (the SSLWrapper setup), handshake complete, no data pending. The results are the same for TLS 1.2 and TLS 1.3.

Case	Result
An entry is on the queue before SSL_read	SSL_read returns -1, the queue is empty, SSL_get_error gives SSL_ERROR_WANT_READ
Control: an entry is put on the queue after SSL_read returns	SSL_get_error gives SSL_ERROR_SSL
An entry is on the queue before SSL_write	The write succeeds, the queue is empty
An entry is on the queue before an SSL_read that has data	The 5 bytes arrive, the queue is empty

• Thus the error that handle_reading takes after a fatal read belongs to that read, with or without 6c43aed. In the common case the commit adds two ERR_clear_error() calls for each record: one before the read that returns the data and one before the read that returns WANT_READ. BoringSSL does the same work again inside each SSL_read.
• The same applies to SSL_do_handshake, SSL_write and SSL_shutdown in SSLWrapper (the "Not in this PR" list and the review note). A stale entry cannot make SSL_get_error report SSL_ERROR_SSL there. That is why no stale entry could be produced from JS.
• Without the commit, src/ is the tree of da0f51d.

2. A TLSSocket over a Duplex with no 'error' listener

Scenario: two clients over a Duplex, no 'error' listener. After both handshakes a TCP proxy sends a bad record to client 0, and 1000 ms later to client 1. A timer fires 2000 ms after the first record. The file runs as a script, not in bun test.

	No uncaughtException handler	With process.on("uncaughtException")
Node.js v26.3.0	The process ends at the first error, status 1. No 'end'.	The handler gets the two errors. The process continues.
Bun 1.4.3 canary (367d939)	No error. 'end' and 'close' (false) for the two clients. Status 0.	The same.
This PR (debug build)	The error is printed. Client 0 gets 'end'. Then the process ends, status 1. Client 1 gets no record and the timer does not fire.	The handler gets the two errors. 'end' and 'close' (false) follow each one. The process continues.

• The process ends at the first error in Node.js and in this PR, with status 1. The difference is that Bun completes the current turn of the event loop first. This PR does not add that difference. Bun does it for each uncaught exception: VirtualMachine::uncaught_exception counts the error, and is_event_loop_alive_excluding_immediates is false from then on. On 1.4.3 canary, a net socket whose 'data' listener emits 'error' with no listener gives the same sequence.
• In bun test an uncaught exception does not end the process (the isBunTest branch of uncaught_exception). The run continues and fails at the end.
• tls: report a fatal TLS error that arrives after the handshake #41272 does the same as this PR for this case. The two tlsFatal branches in net.ts are the same text in the two PRs. "A socket with no handler gets only the close" is a different case: a Bun.connect or Bun.listen handler table with no error handler. NewSocket::on_ssl_error returns early there, in the two PRs.

Probe for 1

Build and run from the repo root, after a debug build:

clang++ -std=c++17 -fsanitize=address -fno-pic -fno-pie -Ivendor/boringssl/include -c probe.cc -o probe.o
clang++ -fsanitize=address -no-pie -fuse-ld=lld probe.o $(find build/debug/obj/vendor/boringssl -name '*.o') -lpthread -o probe
K=test/js/node/test/fixtures/keys
ASAN_OPTIONS=detect_leaks=0 ./probe $K/agent1-cert.pem $K/agent1-key.pem 1.3

Output (the same for 1.2, with TLSv1.2 on the first line):

TLSv1.3 established
A  queue before SSL_read:            1 entry
A  SSL_read=-1 queue after=empty  SSL_get_error=SSL_ERROR_WANT_READ
B  SSL_read=-1 entry queued after the read  SSL_get_error=SSL_ERROR_SSL
C  SSL_write=1 queue after=empty
D  SSL_read=5 (data) queue after=empty
RESULT: SSL_read and SSL_write clear the queue on entry

// Does a stale entry on the thread's error queue, left BEFORE SSL_read, reach
// SSL_get_error? Two in-process TLS peers over memory BIOs (the SSLWrapper
// setup: BIO_s_mem with eof_return -1), handshake completed, no data pending.
#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/ssl.h>
#include <stdio.h>
#include <stdlib.h>

static SSL *make(SSL_CTX *ctx, bool server) {
  SSL *ssl = SSL_new(ctx);
  BIO *in = BIO_new(BIO_s_mem());
  BIO *out = BIO_new(BIO_s_mem());
  BIO_set_mem_eof_return(in, -1);
  BIO_set_mem_eof_return(out, -1);
  SSL_set_bio(ssl, in, out);
  if (server) {
    SSL_set_accept_state(ssl);
  } else {
    SSL_set_connect_state(ssl);
  }
  return ssl;
}

// Move everything one peer sealed into the other peer's read BIO.
static int pump(SSL *from, SSL *to) {
  char buf[65536];
  int moved = 0;
  for (;;) {
    int n = BIO_read(SSL_get_wbio(from), buf, sizeof(buf));
    if (n <= 0) break;
    BIO_write(SSL_get_rbio(to), buf, n);
    moved += n;
  }
  return moved;
}

static void put_stale_entry() {
  OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
}

static const char *name(int err) {
  switch (err) {
    case SSL_ERROR_NONE: return "SSL_ERROR_NONE";
    case SSL_ERROR_SSL: return "SSL_ERROR_SSL";
    case SSL_ERROR_WANT_READ: return "SSL_ERROR_WANT_READ";
    case SSL_ERROR_WANT_WRITE: return "SSL_ERROR_WANT_WRITE";
    case SSL_ERROR_SYSCALL: return "SSL_ERROR_SYSCALL";
    case SSL_ERROR_ZERO_RETURN: return "SSL_ERROR_ZERO_RETURN";
    default: return "other";
  }
}

int main(int argc, char **argv) {
  if (argc < 4) {
    fprintf(stderr, "usage: probe cert.pem key.pem <1.2|1.3>\n");
    return 2;
  }
  uint16_t version = argv[3][2] == '2' ? TLS1_2_VERSION : TLS1_3_VERSION;
  SSL_CTX *sctx = SSL_CTX_new(TLS_method());
  SSL_CTX *cctx = SSL_CTX_new(TLS_method());
  SSL_CTX_set_min_proto_version(sctx, version);
  SSL_CTX_set_max_proto_version(sctx, version);
  SSL_CTX_set_min_proto_version(cctx, version);
  SSL_CTX_set_max_proto_version(cctx, version);
  if (SSL_CTX_use_certificate_chain_file(sctx, argv[1]) != 1 ||
      SSL_CTX_use_PrivateKey_file(sctx, argv[2], SSL_FILETYPE_PEM) != 1) {
    fprintf(stderr, "cannot load the certificate or the key\n");
    return 2;
  }
  SSL_CTX_set_verify(cctx, SSL_VERIFY_NONE, nullptr);
  SSL *server = make(sctx, true);
  SSL *client = make(cctx, false);

  for (int i = 0; i < 20 && !(SSL_is_init_finished(client) && SSL_is_init_finished(server)); i++) {
    SSL_do_handshake(client);
    pump(client, server);
    SSL_do_handshake(server);
    pump(server, client);
  }
  ERR_clear_error();
  if (!SSL_is_init_finished(client) || !SSL_is_init_finished(server)) {
    fprintf(stderr, "the handshake did not finish\n");
    return 2;
  }
  char buf[4096];
  // Drain post-handshake messages (TLS 1.3 tickets) so the next read has nothing.
  pump(server, client);
  SSL_read(client, buf, sizeof(buf));
  ERR_clear_error();
  printf("%s established\n", SSL_get_version(client));

  // Case A: the entry is on the queue BEFORE SSL_read. No clear by the caller.
  put_stale_entry();
  printf("A  queue before SSL_read:            %s\n", ERR_peek_error() ? "1 entry" : "empty");
  int ret = SSL_read(client, buf, sizeof(buf));
  uint32_t queued = ERR_peek_error();
  int err = SSL_get_error(client, ret);
  printf("A  SSL_read=%d queue after=%s  SSL_get_error=%s\n", ret, queued ? "1 entry" : "empty", name(err));
  int a_ok = err == SSL_ERROR_WANT_READ && queued == 0;
  ERR_clear_error();

  // Case B (control, shows that the probe can see the hazard): the entry is
  // queued AFTER SSL_read returned and before SSL_get_error.
  ret = SSL_read(client, buf, sizeof(buf));
  put_stale_entry();
  err = SSL_get_error(client, ret);
  printf("B  SSL_read=%d entry queued after the read  SSL_get_error=%s\n", ret, name(err));
  int b_ok = err == SSL_ERROR_SSL;
  ERR_clear_error();

  // Case C: SSL_write over a memory BIO succeeds. Check that it empties the
  // queue on entry.
  put_stale_entry();
  ret = SSL_write(client, "x", 1);
  queued = ERR_peek_error();
  printf("C  SSL_write=%d queue after=%s\n", ret, queued ? "1 entry" : "empty");
  int c_ok = ret == 1 && queued == 0;
  ERR_clear_error();

  // Case D: real data after a stale entry. The data must arrive.
  pump(client, server);
  SSL_read(server, buf, sizeof(buf));
  SSL_write(server, "hello", 5);
  pump(server, client);
  put_stale_entry();
  ret = SSL_read(client, buf, sizeof(buf));
  queued = ERR_peek_error();
  printf("D  SSL_read=%d (data) queue after=%s\n", ret, queued ? "1 entry" : "empty");
  int d_ok = ret == 5 && queued == 0;

  printf("%s\n", a_ok && b_ok && c_ok && d_ok ? "RESULT: SSL_read and SSL_write clear the queue on entry" : "RESULT: unexpected");
  return a_ok && b_ok && c_ok && d_ok ? 0 : 1;
}

// Bun supplies these two embedder hooks from simdutf. Reference bodies from
// vendor/boringssl/crypto/pem/pem_test.cc.
#include <ctype.h>
#include <openssl/base64.h>
#include <vector>
extern "C" int OPENSSL_pem_public_base64_decode(uint8_t *out, size_t *out_len, size_t max_out,
                                                const uint8_t *in, size_t in_len) {
  std::vector<uint8_t> stripped;
  for (size_t i = 0; i < in_len; i++) {
    if (!isspace(in[i])) stripped.push_back(in[i]);
  }
  return EVP_DecodeBase64(out, out_len, max_out, stripped.data(), stripped.size());
}
extern "C" size_t OPENSSL_pem_public_base64_encode(char *out, size_t max_out, const uint8_t *in,
                                                   size_t in_len) {
  size_t written = 0;
  while (in_len > 0) {
    size_t n = in_len > 48 ? 48 : in_len;
    if (written + (n + 2) / 3 * 4 + 1 > max_out) return 0;
    written += EVP_EncodeBlock(reinterpret_cast<uint8_t *>(out + written), in, n);
    out[written++] = '\n';
    in += n;
    in_len -= n;
  }
  return written;
}

Script for 2

Run from the repo root with no argument, and with the argument handler.

// Two TLS clients over a Duplex with NO 'error' listener. After both
// handshakes a TCP proxy writes a record that cannot be decrypted toward
// client 0, and 1000 ms later toward client 1. What runs after the first error?
//   node nolistener.js            no process-level handler
//   node nolistener.js handler    with process.on("uncaughtException")
const tls = require("node:tls");
const net = require("node:net");
const fs = require("node:fs");
const { Duplex } = require("node:stream");

// Run from the repo root.
const K = "test/js/node/test/fixtures/keys";
const cert = fs.readFileSync(K + "/agent1-cert.pem");
const key = fs.readFileSync(K + "/agent1-key.pem");
const BAD = Buffer.concat([Buffer.from([0x17, 3, 3, 0, 0x20]), Buffer.alloc(32, 0x42)]);
const t0 = Date.now();
const log = (...a) => console.log(String(Date.now() - t0).padStart(4), ...a);

if (process.argv[2] === "handler") {
  process.on("uncaughtException", e => log("uncaughtException handler:", e.code));
}
process.on("exit", code => log("exit event, code", code));

function wrap(sock) {
  const d = new Duplex({
    read() {},
    write(chunk, _enc, cb) {
      sock.write(chunk, cb);
    },
    final(cb) {
      sock.end();
      cb();
    },
  });
  sock.on("data", c => d.push(c));
  sock.on("end", () => d.push(null));
  sock.on("error", () => {});
  return d;
}

const towardClient = [];
const all = [];
const server = tls.createServer({ cert, key }, s => {
  all.push(s);
  s.on("error", () => {});
  s.resume();
});
const proxy = net.createServer(c => {
  const up = net.connect(server.address().port, "127.0.0.1");
  all.push(c, up);
  towardClient.push(c);
  c.pipe(up);
  up.pipe(c);
  c.on("error", () => {});
  up.on("error", () => {});
});

function client(i) {
  return new Promise(resolve => {
    const raw = net.connect(proxy.address().port, "127.0.0.1");
    all.push(raw);
    const t = tls.connect({ socket: wrap(raw), rejectUnauthorized: false });
    t.on("secureConnect", () => {
      log("client", i, "secureConnect");
      resolve();
    });
    t.on("end", () => log("client", i, "end"));
    t.on("close", hadError => log("client", i, "close hadError=" + hadError));
    t.resume();
  });
}

function inject(i) {
  log("client", i, "bad record sent");
  towardClient[i].write(BAD);
}

server.listen(0, "127.0.0.1", () => {
  proxy.listen(0, "127.0.0.1", async () => {
    await client(0);
    await client(1);
    // All timers are relative to this point, after both handshakes.
    inject(0);
    setTimeout(inject, 1000, 1);
    setTimeout(() => {
      log("timer 2000 ms after the first bad record: still running, closing everything");
      for (const s of all) s.destroy();
      server.close();
      proxy.close();
    }, 2000);
  });
});

[Jarred-Sumner]

Superseded by #44618, which consolidates the open TLS pull requests. This fix and its tests are in there, either as written, rewritten smaller, or merged with the other PRs that patched the same cause (see the "By area" list in that PR). Closing in favor of it.