Add p2sh validation

src/transaction.py

@@ -104,8 +104,7 @@ def valid_input(self, vin_idx, vin):
         if scriptpubkey_type == "p2pkh":
             return self.validate_p2pkh(vin_idx, vin)
         elif scriptpubkey_type == "p2sh":
-            pass
-            #return self.validate_p2sh(vin)             
+            return self.validate_p2sh_p2wpkh(vin_idx, vin)
         elif scriptpubkey_type == "v0_p2wsh":
             pass
             #return self.validate_p2wsh(vin)
@@ -124,92 +123,176 @@ def valid_output(self, vout):
         return scriptpubkey_type in ["v0_p2wpkh", "p2sh", "v0_p2wsh", "v1_p2tr", "p2pkh"]
 
     def validate_p2pkh(self, vin_idx, vin):
-        # Checking input signatures.
-        if "scriptsig" in vin:
-            #################
-            # Pubkey script #
-            #################
-            scriptsig = decode_hex(vin.get("scriptsig", ""))
-
-            if not scriptsig:
-                return False
+        #################
+        # Pubkey script #
+        #################
+        scriptsig = decode_hex(vin.get("scriptsig", ""))
 
-            prevout = vin.get("prevout", {})
+        if not scriptsig:
+            return False
 
-            if not prevout:
-                return False
-
-            scriptpubkey = decode_hex(prevout.get("scriptpubkey", ""))
-
-            #####################################################################
-            # Extract signature and public key from scriptSig (Parse scriptSig) #
-            #####################################################################
-            # https://learnmeabitcoin.com/technical/script/p2pkh/
-            # Explanation: the scriptSig contains the signature and the public key (including ASM instructions).            
-
-            signature_len = scriptsig[0] # The first byte represents the length of the DER signature (including hash type)
-            signature_w_hash_type = scriptsig[1:1+signature_len] # Extract the signature (includes the hash type at the end)
-
-            # The last byte of the signature is the hash type (e.g., SIGHASH_ALL = 0x01)
-            signature = signature_w_hash_type[:-1]
-            hash_type = signature_w_hash_type[-1]
-
-            public_key_idx = 1 + signature_len
-            public_key_len = scriptsig[public_key_idx]
-            public_key = scriptsig[public_key_idx+1:public_key_idx+1+public_key_len]
-
-            #######################
-            # Parse DER signature #
-            #######################
-            # https://bitcoin.stackexchange.com/questions/92680/what-are-the-der-signature-and-sec-format
-            # https://learnmeabitcoin.com/technical/keys/signature/
-
-            # Remove the hash_type from the DER signature
-            der_signature = signature_w_hash_type[:-1]
-
-            r, s, hash_type = parse_der_signature_bytes(der_signature)
-
-            der_len = len(der_signature)
-            signature_len = len(r + s) + 6
-
-            if der_len != signature_len:        
-                return False
+        prevout = vin.get("prevout", {})
 
-            signature = r + s
+        if not prevout:
+            return False
+
+        scriptpubkey = decode_hex(prevout.get("scriptpubkey", ""))
+
+        #####################################################################
+        # Extract signature and public key from scriptSig (Parse scriptSig) #
+        #####################################################################
+        # https://learnmeabitcoin.com/technical/script/p2pkh/
+        # Explanation: the scriptSig contains the signature and the public key (including ASM instructions).            
+
+        signature_len = scriptsig[0] # The first byte represents the length of the DER signature (including hash type)
+        signature_w_hash_type = scriptsig[1:1+signature_len] # Extract the signature (includes the hash type at the end)
 
-            ######################
-            # Parse scriptPubKey #
-            ######################
-            # https://learnmeabitcoin.com/technical/script/p2pkh/
-            # Explanation: the scriptPubKey contains: DUP, HASH160, public key hash (including OP_PUSHBYTES_20), EQUALVERIFY and CHECKSIG.
+        # The last byte of the signature is the hash type (e.g., SIGHASH_ALL = 0x01)
+        signature = signature_w_hash_type[:-1]
+        hash_type = signature_w_hash_type[-1]
 
-            if scriptpubkey[0:1] != b'\x76' or scriptpubkey[1:2] != b'\xa9' or scriptpubkey[2:3] != b'\x14':
-                return False  # Not a valid P2PKH scriptPubKey (missing OP_DUP, OP_HASH160, or length mismatch)
+        public_key_idx = 1 + signature_len
+        public_key_len = scriptsig[public_key_idx]
+        public_key = scriptsig[public_key_idx+1:public_key_idx+1+public_key_len]
 
-            if scriptpubkey[23:24] != b'\x88' or scriptpubkey[24:25] != b'\xac':
-                return False  # Not a valid P2PKH scriptPubKey (missing OP_EQUALVERIFY or OP_CHECKSIG)
+        #######################
+        # Parse DER signature #
+        #######################
+        # https://bitcoin.stackexchange.com/questions/92680/what-are-the-der-signature-and-sec-format
+        # https://learnmeabitcoin.com/technical/keys/signature/
 
-            pkh = scriptpubkey[3:23]
+        # Remove the hash_type from the DER signature
+        der_signature = signature_w_hash_type[:-1]
 
-            # Compute the public key hash (HASH160 of the public key) and compare with scriptPubKey
-            calc_pkh = hash160(public_key)
-            if calc_pkh != pkh:
-                return False  # Public key hash does not match
+        r, s, hash_type = parse_der_signature_bytes(der_signature)
+
+        der_len = len(der_signature)
+        signature_len = len(r + s) + 6
 
-            ############################################
-            # Verify the signature with the public key #
-            ############################################
+        if der_len != signature_len:        
+            return False
 
-            data_signed = serialize_transaction(self.json_transaction, vin_idx, int(hash_type))
-            data_hash = hashlib.sha256(data_signed).digest()
+        signature = r + s
 
-            # Verify the signature
-            verifying_key = VerifyingKey.from_string(public_key, curve=SECP256k1)
-            try:
-                verifying_key.verify(signature, data_hash, hashlib.sha256)
-            except BadSignatureError:
-                return False
-
-            return True
+        ######################
+        # Parse scriptPubKey #
+        ######################
+        # https://learnmeabitcoin.com/technical/script/p2pkh/
+        # Explanation: the scriptPubKey contains: DUP, HASH160, public key hash (including OP_PUSHBYTES_20), EQUALVERIFY and CHECKSIG.
+
+        if scriptpubkey[0:1] != b'\x76' or scriptpubkey[1:2] != b'\xa9' or scriptpubkey[2:3] != b'\x14':
+            return False  # Not a valid P2PKH scriptPubKey (missing OP_DUP, OP_HASH160, or length mismatch)
+
+        if scriptpubkey[23:24] != b'\x88' or scriptpubkey[24:25] != b'\xac':
+            return False  # Not a valid P2PKH scriptPubKey (missing OP_EQUALVERIFY or OP_CHECKSIG)
+
+        pkh = scriptpubkey[3:23]
+
+        # Compute the public key hash (HASH160 of the public key) and compare with scriptPubKey
+        calc_pkh = hash160(public_key)
+        if calc_pkh != pkh:
+            return False  # Public key hash does not match
+
+        ############################################
+        # Verify the signature with the public key #
+        ############################################
+
+        data_signed = serialize_transaction(self.json_transaction, vin_idx, int(hash_type))
+        data_hash = hashlib.sha256(data_signed).digest()
+
+        # Verify the signature
+        verifying_key = VerifyingKey.from_string(public_key, curve=SECP256k1)
+        try:
+            verifying_key.verify(signature, data_hash, hashlib.sha256)
+        except BadSignatureError:
+            return False
+
+        return True
+
+    def validate_p2sh_p2wpkh(self, vin_idx, vin):
+        # Extract scriptSig and witness
+        scriptsig = decode_hex(vin.get("scriptsig", ""))
+        witness = vin.get("witness", [])
+
+        if not scriptsig or len(witness) < 2:
+            return False
+
+        prevout = vin.get("prevout", {})
+
+        if not prevout:
+            return False
+
+        scriptpubkey = decode_hex(prevout.get("scriptpubkey", ""))
+
+        #############################
+        # Check if it's a P2SH script #
+        #############################
+        if len(scriptpubkey) != 23 or scriptpubkey[0:1] != b'\xa9' or scriptpubkey[-1:] != b'\x87':
+            return False  # Not a valid P2SH scriptPubKey
+
+        # Extract the redeem script hash from the scriptPubKey
+        # Extract redeem script hash from scriptPubKey
+        if scriptpubkey[0] != 0xa9:  # Check for OP_HASH160
+            return False
+
+        length_of_hash = scriptpubkey[1]
+        if length_of_hash != 0x14:  # 20 bytes
+            return False
+
+        expected_redeem_script_hash = scriptpubkey[2:2+length_of_hash]
+
+        ###########################
+        # Extract the redeem script #
+        ###########################
+        # The redeem script is the data in the scriptSig
+        redeem_script = scriptsig
+
+        # Hash the redeem script and compare it with the expected hash in the scriptPubKey
+        redeem_script_hash = hash160(redeem_script)
+
+        #print("rsh: ", redeem_script_hash)
+        #print("ersh: ", expected_redeem_script_hash)
+
+        if redeem_script_hash != expected_redeem_script_hash:
+            return False  # Redeem script hash does not match        
+
+        ##############################
+        # Parse and execute redeem script #
+        ##############################
+        # The redeem script should be a P2WPKH script: OP_0 <20-byte-public-key-hash>
+        if len(redeem_script) != 22 or redeem_script[0:1] != b'\x00' or redeem_script[1:2] != b'\x14':
+            return False  # Not a valid P2WPKH redeem script
+
+        # Extract the public key hash from the redeem script
+        public_key_hash = redeem_script[2:]
+
+        ######################
+        # Verify the witness #
+        ######################
+        # The witness field contains:
+        #  - witness[0] = signature
+        #  - witness[1] = public key
+
+        signature = decode_hex(witness[0])
+        public_key = decode_hex(witness[1])
+
+        # Compute the public key hash (HASH160 of the public key) and compare with the public key hash in the redeem script
+        calc_pkh = hash160(public_key)
+        if calc_pkh != public_key_hash:
+            return False  # Public key hash does not match
+
+        ############################################
+        # Verify the signature with the public key #
+        ############################################
+
+        data_signed = serialize_transaction(self.json_transaction, vin_idx, 1)  # SIGHASH_ALL is typically 1
+        data_hash = hashlib.sha256(data_signed).digest()
+
+        # Verify the signature
+        verifying_key = VerifyingKey.from_string(public_key, curve=SECP256k1)
+        try:
+            verifying_key.verify(signature[:-1], data_hash, hashlib.sha256)  # Remove the last byte (hash type)
+        except BadSignatureError:
+            return False
 
-        return False
+        return True