BIP-375: add test_runner and validate PSBT structure

Implement psbt structure checks
Add test_runner.py for processing test vectors

bip-0375/validator/validate_psbt.py

@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+"""
+Validates PSBTs according to BIP-375 rules
+
+Provides independent checks for PSBT structure, ECDH share coverage,
+input eligibility, and output script correctness.
+"""
+
+from typing import Tuple
+
+from deps.bitcoin_test.psbt import (
+    PSBT,
+    PSBT_GLOBAL_TX_MODIFIABLE,
+    PSBT_OUT_SCRIPT,
+)
+
+from .psbt_bip375 import (
+    PSBT_GLOBAL_SP_ECDH_SHARE,
+    PSBT_GLOBAL_SP_DLEQ,
+    PSBT_IN_SP_ECDH_SHARE,
+    PSBT_IN_SP_DLEQ,
+    PSBT_OUT_SP_V0_INFO,
+    PSBT_OUT_SP_V0_LABEL,
+)
+
+
+def validate_psbt_structure(psbt: PSBT) -> Tuple[bool, str]:
+    """
+    Validate PSBT structure requirements
+
+    Checks:
+    - Each output must have PSBT_OUT_SCRIPT or PSBT_OUT_SP_V0_INFO
+    - PSBT_OUT_SP_V0_LABEL requires PSBT_OUT_SP_V0_INFO
+    - SP_V0_INFO must be 66 bytes (33-byte scan key + 33-byte spend key)
+    - ECDH shares must be 33 bytes
+    - DLEQ proofs must be 64 bytes
+    - TX_MODIFIABLE is zero when PSBT_OUT_SCRIPT set for SP output
+    """
+    # Check output requirements
+    for i, output_map in enumerate(psbt.o):
+        has_script = (
+            PSBT_OUT_SCRIPT in output_map and len(output_map[PSBT_OUT_SCRIPT]) > 0
+        )
+        has_sp_info = PSBT_OUT_SP_V0_INFO in output_map
+        has_sp_label = PSBT_OUT_SP_V0_LABEL in output_map
+
+        # Output must have script or SP info
+        if not has_script and not has_sp_info:
+            return (
+                False,
+                f"Output {i} must have either PSBT_OUT_SCRIPT or PSBT_OUT_SP_V0_INFO",
+            )
+
+        # SP label requires SP info
+        if has_sp_label and not has_sp_info:
+            return (
+                False,
+                f"Output {i} has PSBT_OUT_SP_V0_LABEL but missing PSBT_OUT_SP_V0_INFO",
+            )
+
+        # Validate SP_V0_INFO field length
+        if has_sp_info:
+            sp_info = output_map[PSBT_OUT_SP_V0_INFO]
+            if len(sp_info) != 66:
+                return (
+                    False,
+                    f"Output {i} SP_V0_INFO has wrong length ({len(sp_info)} bytes, expected 66)",
+                )
+
+    # Validate ECDH share lengths (global and per-input)
+    global_ecdh_shares = psbt.g.get_all_by_type(PSBT_GLOBAL_SP_ECDH_SHARE)
+    for _, ecdh_share in global_ecdh_shares:
+        if len(ecdh_share) != 33:
+            return (
+                False,
+                f"Global ECDH share has wrong length ({len(ecdh_share)} bytes, expected 33)",
+            )
+
+    for i, input_map in enumerate(psbt.i):
+        input_ecdh_shares = input_map.get_all_by_type(PSBT_IN_SP_ECDH_SHARE)
+        for _, ecdh_share in input_ecdh_shares:
+            if len(ecdh_share) != 33:
+                return (
+                    False,
+                    f"Input {i} ECDH share has wrong length ({len(ecdh_share)} bytes, expected 33)",
+                )
+
+    # Validate DLEQ proof lengths (global and per-input)
+    global_dleq_proofs = psbt.g.get_all_by_type(PSBT_GLOBAL_SP_DLEQ)
+    for _, dleq_proof in global_dleq_proofs:
+        if len(dleq_proof) != 64:
+            return (
+                False,
+                f"Global DLEQ proof has wrong length ({len(dleq_proof)} bytes, expected 64)",
+            )
+
+    for i, input_map in enumerate(psbt.i):
+        input_dleq_proofs = input_map.get_all_by_type(PSBT_IN_SP_DLEQ)
+        for _, dleq_proof in input_dleq_proofs:
+            if len(dleq_proof) != 64:
+                return (
+                    False,
+                    f"Input {i} DLEQ proof has wrong length ({len(dleq_proof)} bytes, expected 64)",
+                )
+
+    # Check TX_MODIFIABLE flag when PSBT_OUT_SCRIPT is set
+    for output_map in psbt.o:
+        if PSBT_OUT_SP_V0_INFO in output_map and PSBT_OUT_SCRIPT in output_map:
+            if len(output_map.get(PSBT_OUT_SCRIPT, b"")) > 0:
+                if psbt.g.get(PSBT_GLOBAL_TX_MODIFIABLE) != b"\x00":
+                    return (
+                        False,
+                        "PSBT_OUT_SCRIPT set for silent payments output but PSBT_GLOBAL_TX_MODIFIABLE not zeroed",
+                    )
+    return True, None
+
+
+def validate_ecdh_coverage(psbt: PSBT) -> Tuple[bool, str]:
+    return False, "ECDH coverage check not implemented yet"
+
+
+def validate_input_eligibility(psbt: PSBT) -> Tuple[bool, str]:
+    return False, "Input eligibility check not implemented yet"
+
+
+def validate_output_scripts(psbt: PSBT) -> Tuple[bool, str]:
+    return False, "Output scripts check not implemented yet"