feat(wasm-utxo): expose requiresPrevTx prevTx-inclusion policy#306
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Add a pure-JS prevTx-inclusion predicate to @bitgo/wasm-utxo so all callers share one source of truth for whether a p2sh PSBT input needs non_witness_utxo (full prevTx) or can be signed from witness_utxo-only. requiresPrevTxForP2sh(coinName) answers only the coin-level question for an input the caller has already determined is p2sh (non-segwit) and whose tx format includes prevTx (e.g. "psbt", not "psbt-lite"). It returns false for value-committing coins whose sighash commits the input amount, making prevTx cryptographically pointless for signing p2sh inputs: - Zcash (zec/tzec): ZIP-243 transparent sighash commits the amount. Including prevTx also crashes wasm-utxo, whose consensus::deserialize rejects Zcash overwintered transactions. - BCH family (bch/bcha/eCash, bsv, btg + testnets): replay-protected BIP-143 sighash (SIGHASH_FORKID, the default for the whole family) commits the 8-byte value as preimage item #6. The value-committing mainnet set {zec, bch, bcha, bsv, btg} is normalized via getMainnet (covers testnets). The module is pure JS — no WASM initialization — so the predicate is cheap to evaluate without loading wasm-utxo. Exported both namespaced (fixedScriptWallet.requiresPrevTxForP2sh) and as a top-level named export (alongside CoinName/getMainnet). Refs: T1-3654
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Summary
Expose a pure-JS
requiresPrevTxpolicy from@bitgo/wasm-utxoso all callers share one source of truth for whether a PSBT input needsnon_witness_utxo(full prevTx) or can be signed fromwitness_utxo-only.Why
wasm-utxo'sadd_wallet_input_to_psbtdeserializesprev_txwith the standard Bitcoinconsensus::deserialize, which rejects Zcash overwintered transactions — the root cause of the Zcash (tzec) signing failures (T1-3654). Centralizing the prevTx-inclusion decision inside the sharedwasm-utxopackage gives every caller the same correct policy without each one re-deriving it.Change
New pure-JS module
packages/wasm-utxo/js/fixedScriptWallet/prevTx.tsexporting:requiresPrevTx(coinName, txFormat, chain)— returnsfalsewhenwitness_utxo-only suffices:psbt-litenever includesnon_witness_utxo;witness_utxo;prevTxis pointless for signing p2sh inputs even whentxFormat === "psbt":zec/tzec): ZIP-243 transparent sighash commits the amount. (IncludingprevTxalso crasheswasm-utxo.)bch/bcha/eCash,bsv,btg+ testnets): replay-protected BIP-143 sighash (SIGHASH_FORKID, the default for the whole family) commits the 8-byte value as preimage item feat(wasm-utxo): implement MuSig2 with BitGo-specific p2tr variant #6.isValueCommittingCoin— backed by a mainnet Set{zec, bch, bcha, bsv, btg}normalized viagetMainnet(covers testnets).isZcashCoin— kept (selectsZcashBitGoPsbt).isNonSegwitChain— checkschain === 0 || 1literally so the module does not trigger WASM initialization; the predicate is cheap to evaluate without loadingwasm-utxo.TxFormattype ("psbt" | "psbt-lite" | "legacy").Exported both namespaced (
fixedScriptWallet.requiresPrevTx) and as top-level named exports alongsideCoinName/getMainnet.Test plan
npx mocha test/fixedScript/prevTx.ts— 26 passing (fullrequiresPrevTxtruth table +isValueCommittingCoin/isZcashCoin/isNonSegwitChainsuites)npm run build:ts-esm(tsc) — cleanOut of scope
wasm-utxoconsensus::deserializecrash site is untouched; this PR only exposes a shared predicate so callers can avoid sendingprevTxwhen it's pointless. (The Zcash-awaredecode_zcash_transaction_partshardening and the repro test live on a separate jj change.)Refs: T1-3654