Merge pull request #2253 from questfever/master

BIP375: correctly detect SegWit v2+ witness programs

bip-0375/bip375_test_vectors.json

@@ -568,6 +568,23 @@
     }
   ],
   "valid": [
+    {
+      "description": "input eligibility: bare OP_2 script is not a segwit v2 witness program",
+      "psbt": "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",
+      "supplementary": {
+        "inputs": [
+          {
+            "input_index": 0,
+            "prevout_scriptpubkey": "52",
+            "amount": 100000,
+            "witness_utxo": "a0860100000000000152"
+          }
+        ]
+      },
+      "checks": [
+        "input_eligibility"
+      ]
+    },
     {
       "description": "can finalize: one P2PKH input single-signer",
       "psbt": "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",
@@ -1756,4 +1773,4 @@
       }
     }
   ]
-}
+}

bip-0375/validator/validate_psbt.py

@@ -250,6 +250,15 @@ def validate_dleq_proof(
     return True, None
 
 
+def is_segwit_v2_or_later(script_pubkey: bytes) -> bool:
+    """Return whether script_pubkey is a SegWit v2-v16 witness program."""
+    return (
+        4 <= len(script_pubkey) <= 42
+        and 0x52 <= script_pubkey[0] <= 0x60  # OP_2 through OP_16
+        and script_pubkey[1] == len(script_pubkey) - 2
+    )
+
+
 def validate_input_eligibility(psbt: PSBT) -> Tuple[bool, str]:
     """
     Validate input eligibility constraints for silent payments
@@ -268,7 +277,7 @@ def validate_input_eligibility(psbt: PSBT) -> Tuple[bool, str]:
         if PSBT_IN_WITNESS_UTXO in input_map:
             witness_utxo = input_map[PSBT_IN_WITNESS_UTXO]
             script = parse_witness_utxo(witness_utxo)
-            if script and 0x51 < script[0] <= 0x60:  # OP_2 or higher (segwit v2+)
+            if is_segwit_v2_or_later(script):
                 return False, f"Input {i} uses segwit version > 1 with silent payments"
 
     # Check SIGHASH_ALL requirement - PSBT_IN_SIGHASH_TYPE is optional, but if set it must be SIGHASH_ALL when SP outputs are present