BTC Parser

	* Fix- The number of bytes to push onto the stack was incorrect.
	  Example: a0 should be interpreted as 160, not -32

symbolic_execution/language/bitcoin/parser.py

@@ -22,7 +22,6 @@ from symbolic_execution.language.exceptions import IncompleteIfEndIfClause
 
 pyparsing.ParserElement.enablePackrat()
 from collections import deque
-from symbolic_execution.hardware.machines.btc_machine import str_to_int
 from symbolic_execution.program.block.interfaces import IInstructionBlock
 
 from symbolic_execution.program.block.instruction_block import InstructionBlock
@@ -33,6 +32,23 @@ import sys
 
 sys.setrecursionlimit(1000000)
 
+def read_little_endian(hex: str, bytes: int, start: int = 0) -> int:
+    """Read and returns the integer value of a hexadecimal value in little endian contained in a string.
+
+    Args:
+        hex: A string containing a hexadecimal value encoded in little endian.
+        bytes: The number of bytes to read.
+        start: The offset of the beginning of the hex value.
+
+    Returns:
+        int: The integer value of the hex string in little endian.
+
+    Examples:
+        read_little_endian('xxxaf12xx', 2, 3) will return 4783
+    """
+    ordered = [hex[i : i + 2] for i in range(start, start + bytes * 2, 2)][::-1]
+    string = "".join(ordered)
+    return int(string, 16)
 
 class BitcoinParser(ILanguage):
     """Parser for the Bitcoin script language."""
@@ -72,11 +88,11 @@ class BitcoinParser(ILanguage):
         OP_PUSH_0 = MatchFirst([format(op, "02x") for op in range(0x01, 0x4C)])
         OP_PUSH_0.addParseAction(lambda t: int(t[0], 16))
         OP_PUSH_1 = Literal("4c") + Word(hexnums, exact=2)
-        OP_PUSH_1.addParseAction(lambda t: str_to_int(t[1]))
+        OP_PUSH_1.addParseAction(lambda t: read_little_endian(t[1], 1))
         OP_PUSH_2 = Literal("4d") + Word(hexnums, exact=4)
-        OP_PUSH_2.addParseAction(lambda t: str_to_int(t[1]))
+        OP_PUSH_2.addParseAction(lambda t: read_little_endian(t[1], 2))
         OP_PUSH_4 = Literal("4e") + Word(hexnums, exact=8)
-        OP_PUSH_4.addParseAction(lambda t: str_to_int(t[1]))
+        OP_PUSH_4.addParseAction(lambda t: read_little_endian(t[1], 4))
         OP_PUSH = MatchFirst([OP_PUSH_0, OP_PUSH_1, OP_PUSH_2, OP_PUSH_4])
         DATA = Combine(countedArray(BYTE, intExpr=OP_PUSH))