PSBTv2 (BIP-370) Support#87
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notTanveer
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Add a check for `p2sh-p2wsh`, `p2sh-p2wpkh` and raise an exception for unknow types. fix diybitcoinhardware#93 Co-authored-by: edilmedeiros <jose.edil@gmail.com> Co-authored-by: moisespompilio <93723302+moisesPompilio@users.noreply.github.com>
This reverts commit e1d7339.
In order to test the replace assertions with conditional error raising, specifically, in bip85 code, was added a test for `derive_entropy` method as well the failure cases described in `derive_mnemonic` and `derive_hex`.
…spaces should be invalid
…rsing - Add LOCKTIME_THRESHOLD constant (500000000) for locktime type discrimination - Add required_time_locktime and required_height_locktime fields to InputScope - Propagate those fields in InputScope.update() - Parse PSBT_IN_REQUIRED_TIME_LOCKTIME (0x11) and PSBT_IN_REQUIRED_HEIGHT_LOCKTIME (0x12) in InputScope.read_value(), with range validation - Serialize 0x11 and 0x12 in InputScope.write_to() under the version==2 block - Add version=None parameter to InputScope.read_value() and OutputScope.read_value() so callers can signal the PSBT version being parsed - Add InputScope.read_from() and OutputScope.read_from() classmethods that accept and forward the version parameter (supersede PSBTScope base classmethod for v2) - Propagate version in LInputScope.read_value() and LOutputScope.read_value() (pset.py) so the Liquid subclasses stay compatible - Pass version=self.version when PSBTView calls read_from() for input/output scopes so PSBTv2 scopes are parsed with the correct version context
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- Add TxModifiable class with INPUTS/OUTPUTS/SIGHASH_SINGLE bit flags - Add PSBT._validate_v2_output() classmethod to check required PSBTv2 output fields; PSET overrides it to allow value_commitment in place of value - Add tx_modifiable_flags field to PSBT.__init__() (None for v0/unset) - Update comment on self.version to note '2 for v2' - Add PSBT.determine_locktime(): implements BIP-370 locktime selection algorithm (height vs time preference, max-of-minimums) - Update PSBT.tx property to call determine_locktime() for PSBTv2 - Update PSBT.write_to(): serialize PSBT_GLOBAL_TX_MODIFIABLE (0x06) when set - Rewrite PSBT.read_from(): collect all global KVs into OrderedDict before branching on PSBTv2 vs PSBTv0; detect version from 0xfb; reject unsigned tx in PSBTv2 and reject v2-only keys in PSBTv0; validate required fields after parsing; call read_from with version=version on all scopes - Rewrite PSBT.parse_unknowns(): strip 0xfb/0x06; guard 0x02/0x03/0x04/0x05 behind version==2; track _raw_input_count_from_global and _raw_output_count_from_global for PSBTv2 scope parsing - Add version guards to InputScope.read_value() for 0x0e/0x0f/0x10: PSBT_IN_PREVIOUS_TXID, PSBT_IN_OUTPUT_INDEX, and PSBT_IN_SEQUENCE are rejected when version != 2 - Add version guards to OutputScope.read_value() for 0x03/0x04: PSBT_OUT_AMOUNT and PSBT_OUT_SCRIPT are rejected when version != 2
…_with - Update sign_with(): after each legacy/segwit signature, update tx_modifiable_flags per BIP-370: clear INPUTS bit if not ANYONECANPAY, clear OUTPUTS bit if not NONE, set SIGHASH_SINGLE bit if sighash type is SINGLE - Add get_tx_modifiable() / set_tx_modifiable(flags): getter/setter for PSBT_GLOBAL_TX_MODIFIABLE; setter raises PSBTError on PSBTv0 - Add is_inputs_modifiable(): True if version!=2, tx_modifiable_flags is None, or INPUTS bit is set - Add is_outputs_modifiable(): True if version!=2, tx_modifiable_flags is None, or OUTPUTS bit is set - Add has_sighash_single(): True only if version==2, tx_modifiable_flags is not None, and SIGHASH_SINGLE bit is set - Add add_input(input_scope): appends an InputScope, gated on is_inputs_modifiable(); updates _raw_input_count_from_global for PSBTv2 - Add add_output(output_scope): appends an OutputScope, gated on is_outputs_modifiable(); updates _raw_output_count_from_global for PSBTv2
Add test_psbtV2.py with 37 tests covering PSBTv2 parsing, serialization, locktime selection, TxModifiable flags, and add_input/add_output API.
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Please rebase with master (we plan to stop using develop branch). There shouldn't be conflicts rebasing it locally with git.
Later, there are a few things to take a look at:
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PSBTView does not fully enforce or apply PSBTv2 rules. It can accept a v2 PSBT with PSBT_GLOBAL_UNSIGNED_TX if that key appears before PSBT_GLOBAL_VERSION, and PSBTView.locktime uses only fallback locktime instead of deriving locktime from per-input requirements. Sighashes computed through PSBTView can therefore commit to the wrong locktime.
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add_input() / add_output() only check modifiable flags. BIP370 Constructor rules also require validating required fields, locktime compatibility, preserving existing signed locktime, and handling SIGHASH_SINGLE input/output pairing.
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Several PSBTv2 fixed-width input fields lack exact length validation: previous txid, output index, sequence, required time locktime, and required height locktime. Malformed values can be accepted and later serialize incorrectly or fail unexpectedly.
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compress mode can lose its OOM-protection benefit for PSBTv2 non-witness UTXOs when PSBT_IN_NON_WITNESS_UTXO appears before PSBT_IN_PREVIOUS_TXID / PSBT_IN_OUTPUT_INDEX in the input map. Since key order is not guaranteed, this should be pre-scanned, deferred, or documented.
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Signedness should be made consistent with BIP370: PSBT_OUT_AMOUNT is read as signed but written unsigned, and PSBT_GLOBAL_TX_VERSION is specified as signed int32 but read/written unsigned.
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Explicit PSBTv0 version handling is too strict. BIP174 allows v0 PSBTs to either omit
PSBT_GLOBAL_VERSIONor set it to0, but this parser rejects version0. -
PSBTv2 global input/output counts are used to allocate placeholder scope objects before parsing actual scopes. Since those counts are attacker-controlled and the placeholders are later discarded, this creates an avoidable memory-exhaustion risk. Store counts only and allocate scopes as they are parsed.
Recommended test additions: PSBTv2 parse/serialize roundtrips, PSBTView locktime/sighash behavior, constructor API behavior, signer TX_MODIFIABLE updates, malformed fixed-width field lengths, and the PSET v2 output validation path.
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This PR improves PSBT (Partially Signed Bitcoin Transaction) v2 support, especially strict validation and compatibility with BIP 370 test vectors. It also adds a comprehensive set of tests for PSBTv2 edge cases and locktime determination.
Details
1. PSBTv2 Compliance and Parsing Improvements
src/embit/liquid/pset.pyto allow passing theversionparameter down toread_valueand its parent implementations. This ensures correct handling of versioned PSBT fields.super().read_valueto pass along theversionargument, improving extensibility and correctness for PSBTv2.2. PSBT View Updates
src/embit/psbtview.py:input()andoutput()methods now pass theversionparameter when reading from the stream, allowing PSBT-in and out scopes to parse versioned fields correctly.3. Comprehensive PSBTv2 Test Vectors
tests/tests/test_psbtV2.pycontaining:Motivation
Testing
pytest tests/tests/test_psbtV2.pyto verify all BIP 370 test vectors and locktime cases.embitto confirm correct parsing — everything worked as expected.References