DecodeTxErr: prevent potential DoS caused by a malformed tx or block - #5
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ronny wants to merge 1 commit into
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DecodeTxErr: prevent potential DoS caused by a malformed tx or block#5ronny wants to merge 1 commit into
ronny wants to merge 1 commit into
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SomeoneWeird
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DivineGod,
elusiveshiba,
raffecat and
tjstebbing
May 19, 2026 14:08
DivineGod
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May 19, 2026
A malformed tx or block with a varint count claiming more entries than the remaining buffer could possibly encode (e.g. a 0xff prefix declaring max-uint64 inputs) would make readVinVout/readBlock/readMerkleBranch loop billions of times against an exhausted stream, growing slices of zero-valued records until OOM. Recover() in consumers can't catch this — the goroutine never panics, it just never returns. Add tight lower-bound size constants (minTxInBytes=41, minTxOutBytes=9, minTxBytes=60, minHashBytes=32) and reject any varint count that would exceed remaining-bytes / min-per-element. Applied at every varint-driven loop in block.go: tx_count, merkle-branch hashes, vin_count, vout_count, and the witness stack count + per-item length. TestDecodeTxErr_MaliciousVinCount covers both the huge-varint case and the truncated-count case under a 500ms deadline, so a regression fails the test instead of hanging CI.
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@raffecat @SomeoneWeird could either of you please merge if this is good to go? I don't have access. |
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A malformed tx or block with a varint count claiming more entries than the remaining buffer could possibly encode (e.g. a
0xffprefix declaring max-uint64 inputs) would makereadVinVout/readBlock/readMerkleBranchloop billions of times against an exhausted stream, growing slices of zero-valued records until OOM.recover()in consumers can't catch this — the goroutine never panics, it just never returns.This change adds tight lower-bound size constants (
minTxInBytes=41,minTxOutBytes=9,minTxBytes=60,minHashBytes=32) and rejects any varint count that would exceed remaining-bytes / min-per-element. Applied at every varint-driven loop in block.go:tx_count, merkle-branch hashes,vin_count,vout_count, and the witness stack count + per-item length.TestDecodeTxErr_MaliciousVinCountcovers both the huge-varint case and the truncated-count case under a 500ms deadline, so a regression fails the test instead of hanging CI.