core/bitcoin: Implement parsing of scripts and witnesses for signature verification.

core/src/apps/bitcoin/scripts.py

@@ -7,6 +7,7 @@ from trezor.messages.TxInputType import TxInputType
 
 from apps.common import address_type
 from apps.common.coininfo import CoinInfo
+from apps.common.readers import BytearrayReader, read_bitcoin_varint
 from apps.common.writers import empty_bytearray, write_bitcoin_varint
 
 from . import common
@@ -15,6 +16,7 @@ from .multisig import (
     multisig_get_pubkeys,
     multisig_pubkey_index,
 )
+from .readers import read_bytes_prefixed, read_op_push
 from .writers import (
     write_bytes_fixed,
     write_bytes_prefixed,
@@ -23,7 +25,7 @@ from .writers import (
 )
 
 if False:
-    from typing import List, Optional
+    from typing import List, Optional, Tuple
     from trezor.messages.TxInputType import EnumTypeInputScriptType
     from .writers import Writer
 
@@ -143,6 +145,23 @@ def input_script_p2pkh_or_p2sh(
     return w
 
 
+def parse_input_script_p2pkh(script_sig: bytes,) -> Tuple[bytes, bytes, int]:
+    try:
+        r = BytearrayReader(script_sig)
+        n = read_op_push(r)
+        signature = r.read(n - 1)
+        hash_type = r.get()
+
+        n = read_op_push(r)
+        pubkey = r.read()
+        if len(pubkey) != n:
+            raise ValueError
+    except (ValueError, IndexError):
+        wire.DataError("Invalid scriptSig.")
+
+    return pubkey, signature, hash_type
+
+
 def output_script_p2pkh(pubkeyhash: bytes) -> bytearray:
     utils.ensure(len(pubkeyhash) == 20)
     s = bytearray(25)
@@ -253,6 +272,27 @@ def witness_p2wpkh(signature: bytes, pubkey: bytes, sighash: int) -> bytearray:
     return w
 
 
+def parse_witness_p2wpkh(witness: bytes) -> Tuple[bytes, bytes, int]:
+    try:
+        r = BytearrayReader(witness)
+
+        if r.get() != 2:
+            # num of stack items, in P2WPKH it's always 2
+            raise ValueError
+
+        n = read_bitcoin_varint(r)
+        signature = r.read(n - 1)
+        hash_type = r.get()
+
+        pubkey = read_bytes_prefixed(r)
+        if r.remaining_count():
+            raise ValueError
+    except (ValueError, IndexError):
+        raise wire.DataError("Invalid witness.")
+
+    return pubkey, signature, hash_type
+
+
 def witness_p2wsh(
     multisig: MultisigRedeemScriptType,
     signature: bytes,
@@ -302,6 +342,33 @@ def witness_p2wsh(
     return w
 
 
+def parse_witness_p2wsh(witness: bytes) -> Tuple[bytes, List[Tuple[bytes, int]]]:
+    try:
+        r = BytearrayReader(witness)
+
+        # Get number of witness stack items.
+        item_count = read_bitcoin_varint(r)
+
+        # Skip over OP_FALSE, which is due to the old OP_CHECKMULTISIG bug.
+        if r.get() != 0:
+            raise ValueError
+
+        signatures = []
+        for i in range(item_count - 2):
+            n = read_bitcoin_varint(r)
+            signature = r.read(n - 1)
+            hash_type = r.get()
+            signatures.append((signature, hash_type))
+
+        script = read_bytes_prefixed(r)
+        if r.remaining_count():
+            raise ValueError
+    except (ValueError, IndexError):
+        raise wire.DataError("Invalid witness.")
+
+    return script, signatures
+
+
 # Multisig
 # ===
 #
@@ -351,6 +418,33 @@ def input_script_multisig(
     return w
 
 
+def parse_input_script_multisig(
+    script_sig: bytes,
+) -> Tuple[bytes, List[Tuple[bytes, int]]]:
+    try:
+        r = BytearrayReader(script_sig)
+
+        # Skip over OP_FALSE, which is due to the old OP_CHECKMULTISIG bug.
+        if r.get() != 0:
+            raise ValueError
+
+        signatures = []
+        n = read_op_push(r)
+        while r.remaining_count() > n:
+            signature = r.read(n - 1)
+            hash_type = r.get()
+            signatures.append((signature, hash_type))
+            n = read_op_push(r)
+
+        script = r.read()
+        if len(script) != n:
+            raise ValueError
+    except (ValueError, IndexError):
+        raise wire.DataError("Invalid scriptSig.")
+
+    return script, signatures
+
+
 def output_script_multisig(pubkeys: List[bytes], m: int) -> bytearray:
     w = empty_bytearray(output_script_multisig_length(pubkeys, m))
     write_output_script_multisig(w, pubkeys, m)
@@ -376,6 +470,39 @@ def output_script_multisig_length(pubkeys: List[bytes], m: int) -> int:
     return 1 + len(pubkeys) * (1 + 33) + 1 + 1  # see output_script_multisig
 
 
+def parse_output_script_multisig(script: bytes) -> Tuple[List[bytes], int]:
+    try:
+        r = BytearrayReader(script)
+
+        threshold = r.get() - 0x50
+        pubkey_count = script[-2] - 0x50
+
+        if (
+            not 1 <= threshold <= 15
+            or not 1 <= pubkey_count <= 15
+            or threshold > pubkey_count
+        ):
+            raise ValueError
+
+        public_keys = []
+        for i in range(pubkey_count):
+            n = read_op_push(r)
+            if n != 33:
+                raise ValueError
+            public_keys.append(r.read(n))
+
+        r.get()  # ignore pubkey_count
+        if r.get() != 0xAE:  # OP_CHECKMULTISIG
+            raise ValueError
+        if r.remaining_count():
+            raise ValueError
+
+    except (ValueError, IndexError):
+        raise wire.DataError("Invalid multisig script")
+
+    return public_keys, threshold
+
+
 # OP_RETURN
 # ===