script: add and default to SIGHASH_ALL_WITH_RANGEPROOF for pre-taproot signing - #1584
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delta1 wants to merge 9 commits into
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script: add and default to SIGHASH_ALL_WITH_RANGEPROOF for pre-taproot signing #1584delta1 wants to merge 9 commits into
delta1 wants to merge 9 commits into
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… rangeproof bit for Taproot signing Add a named default constant SIGHASH_ALL_WITH_RANGEPROOF (SIGHASH_ALL | SIGHASH_RANGEPROOF) and a DefaultSighashType() helper that selects the default pre-Taproot sighash based on whether SIGHASH_RANGEPROOF is active for the target chain. Strip the 0x40 (SIGHASH_RANGEPROOF) bit when computing Schnorr signatures, since the BIP341-style sighash always commits to rangeproofs and rejects the bit. This keeps SIGHASH_ALL_WITH_RANGEPROOF a valid universal default for both pre-Taproot and Taproot signing.
…eck) Add a Chain interface method that reports whether SIGHASH_RANGEPROOF is active for signing at the current chain tip, mirroring the mempool standardness check (DeploymentActiveAfter for DEPLOYMENT_DYNA_FED). This is the live-tip gating source used by the wallet and wallet-backed RPC to decide the default pre-Taproot sighash.
Add a CChainParams helper that decides, from chain parameters alone (without a chain tip), whether SIGHASH_RANGEPROOF can be assumed active. This is true when dynafed is configured ALWAYS_ACTIVE, or on liquidv1 where dynafed is height-activated (not the ALWAYS_ACTIVE sentinel) but is long since active on the live chain. This is the chainstate-less gating source used by elements-tx. Add a unit test covering liquidv1 (active by chain type, nStartTime != ALWAYS_ACTIVE), liquidv1test (active via ALWAYS_ACTIVE override), and regtest (inactive).
Change the wallet's default pre-Taproot sighash to commit to output rangeproofs when dynafed is active at the current tip, closing the pre-Taproot rangeproof (witness) malleability gap. Route the default through DefaultSighashType(chain().isSighashRangeproofActive()) in CWallet::SignTransaction and in the signrawtransactionwithwallet / walletprocesspsbt RPCs when the caller does not supply a sighash. Explicit user-supplied sighash types are left untouched.
…d active Default the raw signing RPCs to commit to output rangeproofs when dynafed is active at the current tip. The SignTransaction util gains a sighash_rangeproof_active parameter and, when no sighash is supplied, resolves the default via DefaultSighashType. Wire this through signrawtransactionwithkey and descriptorprocesspsbt using DeploymentActiveAfter(DEPLOYMENT_DYNA_FED) for tip activation. Explicit user-supplied sighash types are left untouched.
elements-tx has no chainstate, so gate the default sighash on chain parameters via CChainParams::SighashRangeproofActiveByParams(): commit to rangeproofs by default on chains where dynafed is known active (including liquidv1), otherwise use the historical SIGHASH_ALL default so offline-built txs stay standard and valid. Normalize SIGHASH_DEFAULT to SIGHASH_ALL for the legacy tool path; explicit sighash=... still overrides.
Extend feature_sighash_rangeproof.py with a case asserting that the wallet's default sign path (no explicit sighash arg) produces signatures that commit to output rangeproofs once dynafed is active.
Document the new default pre-Taproot sighash (SIGHASH_ALL | SIGHASH_RANGEPROOF), its scope (wallet + raw RPC + bitcoin-tx), and the activation/chain-params gating.
apoelstra
approved these changes
Aug 19, 2026
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Pre-Taproot signatures using the historical SIGHASH_ALL default do not commit to output rangeproofs, leaving a witness malleability gap: an attacker can alter a transaction's rangeproofs without invalidating its signatures. This branch closes that gap by making signing default to SIGHASH_ALL | SIGHASH_RANGEPROOF on chains where dynafed is active, while leaving explicit user-supplied sighash types untouched and preserving the legacy default.
Scope: