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node:crypto: make Hash update()/copy() after end() throw instead of reusing the finalized context - #42208
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Hash.prototype._flush takes the digest with finalized=false so that an explicit digest() after the stream ends still returns the cached value. That left m_finalized clear while EVP_DigestFinal_ex had already cleansed the EVP_MD_CTX. A later update() fed the zeroed context: for sha3-* BoringSSL's keccak absorb loop runs with rate_bytes == 0 and never returns, other digests silently hashed from a zeroed state, and copy() duplicated that state. digest() now frees the EVP_MD_CTX (or the ExternZigHash hasher) as soon as the result is cached. update() then fails with ERR_CRYPTO_HASH_UPDATE_FAILED like Node, copy() throws ERR_CRYPTO_HASH_FINALIZED, and a repeated digest() after _flush now sets m_finalized on the ExternZigHash path too.
…update() after end() Node's Hash.prototype._flush calls the native digest without the kFinalized check, so ending the stream after an explicit digest() pushes the cached digest instead of erroring. digest(enc, false) now does the same and never clears m_finalized. A zero-length update() after the stream has ended succeeds in Node because OpenSSL's EVP_DigestUpdate returns before its finalized check. JSHash::update mirrors that. Also report only the cached digest to the GC once the context is freed.
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Status Reproduced on Bun 1.4.3 and main (4ff9193) before the change: import crypto from "node:crypto";
const h = crypto.createHash("sha3-256");
h.update("abc");
h.end();
h.update("late"); // never returns, 100% CPU in BORINGSSL_keccak_absorb
The new cases in CI: the diff is green. Every test lane passed in build 113847 or build 113851. The remaining red is unrelated: in 113851 both |
Walkthrough
ChangesHash finalization compatibility
Suggested reviewers: Merge Risk: 🟡 Moderate · up to Zero-length XOF hashes may remain reusable after stream completion, causing incorrect finalized-state behavior. This should be fixed before merge. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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I reviewed this PR and didn't find any bugs. Because it reworks native-state lifetime in a node:crypto C++ binding and takes a deliberate divergence from Node (copy() after end() throws instead of returning an unusable Hash), a human sign-off on that trade-off is still worthwhile.
What was reviewed:
- Double-free:
m_zigHasheris nulled afterdestroy()and the destructor guards on it;m_ctx.reset()is idempotent via the smart pointer. constructHashcopy path with released state — the newm_digestguard is required; without itgetDigest()/m_zigHasheron the freed context would fall through to the wrong error.len == 0(XOFoutputLength: 0) still skips the release block, som_digest.data()is null with a zero-length span and the live context is left intact — same as before for both backends.- Tests: subprocess pipes drained concurrently, combined-object assertion,
errorwired to reject in the stream test, both EVP and ExternZigHash algorithms covered.
Extended reasoning...
Overview
The PR fixes crypto.Hash lifecycle after finalization: end() (via _flush) previously ran EVP_DigestFinal_ex without setting m_finalized, leaving a cleansed context that update()/copy() would reuse — hanging forever on SHA-3 (zeroed keccak rate_bytes) or hashing garbage on other digests. The fix caches the digest in m_digest, releases the native EVP_MD_CTX/ExternZigHash handle immediately, and gates update()/copy()/digest() on that cached state. It also makes _flush skip the finalized check so end() after digest() pushes the cached digest instead of erroring, matching Node. Two tests in node-crypto.test.js cover both native backends across five algorithms.
Security risks
This is node:crypto, but the change is lifecycle/state-machine semantics rather than any cryptographic primitive, key handling, or randomness. The main risk class is memory safety: explicitly destroying m_zigHasher and resetting m_ctx inside digest() while the destructor also frees them. I checked both — m_zigHasher is set to nullptr after destroy and the destructor is guarded; EVPMDCtxPointer::reset() is a smart-pointer reset, safe to call twice. The new m_digest check in constructHash is necessary because the released state would otherwise be dereferenced on the copy path. I did not find UAF, double-free, or a way to reach the old cleansed-context reuse after this change.
Level of scrutiny
Medium-high. Native C++ bindings with manual resource release, a unification of two previously-divergent code paths (EVP vs ExternZigHash), and an intentional Node-compat divergence (copy() after end() throws ERR_CRYPTO_HASH_FINALIZED where Node returns a Hash whose methods all throw). The divergence is documented in code comments and the PR description with a rationale (no live state to clone under BoringSSL), but per the repo's Node-compat conventions a maintainer should confirm that trade-off is acceptable. The PR also notes overlap with #35991 and a rebase conflict with #40075 that will need to preserve the context release — coordination a human is better placed to manage.
Other factors
Test construction follows the harness rules closely: the hang case is isolated in a subprocess with bunExe()/bunEnv, stdout/stderr/exited are drained via Promise.all, and the assertion is a single combined {stdout, stderr, exitCode} object. The stream-order test wires error to reject and awaits the actual end event rather than sleeping. Both backends and both orderings (end→digest, digest→end) are covered, and the second-digest() regression on the ExternZigHash path is now asserted. Comments cite upstream Node/OpenSSL lines for the counterintuitive choices. No findings from the bug hunt (dry_streak); no prior reviewer objections on the timeline.
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Updated 6:40 AM PT - Sep 10th, 2026
❌ @robobun, your commit dc573ee has some failures in 🧪 To try this PR locally: bunx bun-pr 42208That installs a local version of the PR into your bun-42208 --bun |
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Inline comments:
In `@src/jsc/bindings/node/crypto/JSHash.cpp`:
- Line 263: Update the _flush logic around m_digest so native finalization and
state cleanup also occur when m_mdLen is zero, ensuring subsequent update() or
copy() calls throw ERR_CRYPTO_HASH_FINALIZED. Extend the existing lifecycle
regression to cover createHash("shake128", { outputLength: 0 }) after end().
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src/jsc/bindings/node/crypto/JSHash.cpp
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Problem
createHash("sha3-*"):hash.update()afterhash.end()never returns. The thread spins inbssl::BORINGSSL_keccak_absorb←EVP_DigestUpdate←Bun::jsHashProtoFuncUpdate. Acopy()made afterend()hangs on use.Hash.prototype._flushcallsdigest(null, false), sojsHashProtoFuncDigest(src/jsc/bindings/node/crypto/JSHash.cpp:225) runsEVP_DigestFinal_exbut leavesm_finalizedclear.update()andcopy()check only that and reuse the cleansedEVP_MD_CTX. Zeroed keccak state hasrate_bytes == 0, so the absorb loop never advances.digest()thenend(), emittedERR_CRYPTO_HASH_FINALIZEDfrom_flush. Node pushes the cached digest.Fix
digest()frees the native state once the result is cached inm_digest. Later calls read it. The_flushcall (finalized == false) skips the finalized check and never clearsm_finalized, as in Node.update()with no native state throwsERR_CRYPTO_HASH_UPDATE_FAILEDlike Node (zero-length input still succeeds, as in OpenSSL).copy()also checksm_digestand throwsERR_CRYPTO_HASH_FINALIZED.copy()afterend()returns aHashwhose methods all throw. Bun throws atcopy().test/js/node/crypto/node-crypto.test.js(two new cases, both fail on 1.4.3), all oftest/js/node/crypto/, thetest-crypto-hash*Node tests. Self-reviewed: 3 concerns, 3 addressed.Background
crypto.Hashis a JSLazyTransformover a nativeJSHashcell holding a BoringSSLEVP_MD_CTX(md5, sha1/2/3) or anExternZigHashhandle (blake2, shake).m_finalizedis the JS-visible "Digest already called" bit. Node's_flushbypasses it:end()works afterdigest(), onedigest()works afterend()(Piping streams into SHA3 without end: false crashes nodejs/node#28245).EVP_DigestFinal_exzeroes the context. OpenSSL 3 flags itFINALISEDand fails the next non-empty update, hence Node's error code.Notes
Repro:
Deterministic on 1.4.2, 1.4.3 and main, release and ASAN builds.
h.copy().update(),h.copy().digest()and evenh.update("")afterend()spin too (the loop iswhile (in_len >= ctx->rate_bytes)with both zero). On sha256,h.copy().digest("hex")afterend()returned 64 zeros.Behaviour after
h.update("abc"); h.end()(Node v26.3.0 / Bun 1.4.3 / this PR):h.update("late")ERR_CRYPTO_HASH_UPDATE_FAILEDERR_CRYPTO_HASH_UPDATE_FAILEDh.update("")h(OpenSSL returns before the finalized check)hh.copy()FINALISEDflag, so itsupdate()/digest()throw)ERR_CRYPTO_HASH_FINALIZEDh.digest("hex")h.digest("hex")againERR_CRYPTO_HASH_FINALIZEDERR_CRYPTO_HASH_FINALIZEDAnd after
h.update("abc"); h.digest():h.end()'error'withERR_CRYPTO_HASH_FINALIZED(uncaught without a listener)h.update()/h.copy()/h.digest()afterwardsERR_CRYPTO_HASH_FINALIZEDThe realistic shape of the second table is:
This exited with an uncaught
ERR_CRYPTO_HASH_FINALIZEDon 1.4.3 and works in Node.The "digest again" row changes for blake2b512/shake128 because the
ExternZigHashbranch returned the cached digest before reaching them_finalizedassignment. Both branches now share one tail.Hmacis not touched:JSHmac::digestalready resets its context and setsm_finalizedeven from_flush.#35991 (stream
write()after a directdigest(), the_transformpath) and #40075 (Hash/Hmac as single native classes) touch the same file. #40075 will conflict injsHashProtoFuncDigestand needs to keep the context release on rebase; its_flush() after digest()test expects the behaviour this PR implements.[human-review] gate passed · iteration 2 · 2 files touched
fails on main (without fix)
passes on PR (with fix)
diff hotspot
gate history · 2 passed · 0 rejected · iteration 2
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