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search_codecopy.py
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search_codecopy.py
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#!/usr/bin/env python
"""
Ghidra-evm
Copyright (C) 2020 - Antonio de la Piedra
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
"""
search_codecopy.py analyzes EVM creation code and
finds the function_selector and the methods of the
contract in the runtime code part.
"""
import ghidra_bridge
import pprint
import sys
import binascii
from tqdm import tqdm
from evm_cfg_builder.cfg import CFG
# constants
JUMP_TABLE_WORD_SIZE = 4
# functions
def read_ram(ram, addr, size):
print("[*] Reading RAM:", size, "bytes", "at", addr)
addr_ram = ram.getStart().add(int(addr, 16))
evm_code = ""
for i in tqdm(range(0, int(copy_size, 16) - 1)):
ram_byte = ram.getByte(addr_ram.add(i))
evm_code = evm_code + "{:02x}".format(ram_byte & 0xff)
print(evm_code)
return evm_code
""" returns cfg """
def fill_jump_table(evm_code, evm_jump_table, copy_addr):
print("[*] Creating CFG...")
cfg = CFG(evm_code)
print("[*] Resolving jumps...")
addr = evm_jump_table.getStart()
for basic_block in cfg.basic_blocks:
if (basic_block.all_outgoing_basic_blocks):
print(basic_block)
print("Finishes at: ", hex(basic_block.end.pc + int(copy_addr, 16)))
if (len(basic_block.all_outgoing_basic_blocks) == 2): # JUMPI creates 2 branches
for out_block in basic_block.all_outgoing_basic_blocks:
if ((out_block.start.pc - 1) != basic_block.end.pc):
print("\tJUMPI to: ", hex(out_block.start.pc))
jmp_in_addr = out_block.start.pc
jmp_in_addr += int(copy_addr, 16)
jump_addr_list = jmp_in_addr.to_bytes(JUMP_TABLE_WORD_SIZE, byteorder="little")
jmp_out_addr = basic_block.end.pc
jmp_out_addr += int(copy_addr, 16)
evm_jump_table.putBytes(addr.add(JUMP_TABLE_WORD_SIZE*jmp_out_addr), jump_addr_list)
else:
print("\tJUMP to:", hex(basic_block.all_outgoing_basic_blocks[0].start.pc + int(copy_addr, 16)))
jmp_in_addr = basic_block.all_outgoing_basic_blocks[0].start.pc
jmp_in_addr += int(copy_addr, 16)
jump_addr_list = jmp_in_addr.to_bytes(JUMP_TABLE_WORD_SIZE, byteorder="little")
jmp_out_addr = basic_block.end.pc
jmp_out_addr += int(copy_addr, 16)
evm_jump_table.putBytes(addr.add(JUMP_TABLE_WORD_SIZE*jmp_out_addr), jump_addr_list)
return cfg
def explore_functions(cfg, copy_addr):
print("[*] Exploring functions...")
for function in sorted(cfg.functions, key=lambda x: x.start_addr):
print("\tFound function: ", function.name, "at: ", addr_ram.add(function.start_addr))
if (function.name == "_dispatcher"):
createFunction(addr_ram.add(function.start_addr), "function_selector")
else:
createFunction(addr_ram.add(function.start_addr), function.name)
listing = currentProgram.getListing()
codeUnit = listing.getCodeUnitAt(toAddr(function.start_addr + int(copy_addr, 16)))
attr_list = ""
for attr in function.attributes:
attr_list = attr_list + " " + attr
codeUnit.setComment(codeUnit.PRE_COMMENT, "attributes: " + attr_list)
# main
print("""\
_ _ _
__ _| |__ (_) __| |_ __ __ _ _____ ___ __ ___
/ _` | '_ \| |/ _` | '__/ _` |_____ / _ \ \ / / '_ ` _ \
| (_| | | | | | (_| | | | (_| |_____| __/\ V /| | | | | |
\__, |_| |_|_|\__,_|_| \__,_| \___| \_/ |_| |_| |_| v.0.1
|___/
""")
# creates the bridge and loads the flat API into the global namespace
b = ghidra_bridge.GhidraBridge(namespace=globals(), response_timeout=1000)
tid = currentProgram.startTransaction("ghidrda evm")
print("[*] Looking for _dispatcher...")
function_list = getGlobalFunctions("_dispatcher")
memory = currentProgram.getMemory()
ram = memory.getBlock("ram")
ram_size = ram.getSize()
if (function_list):
addr = function_list[0].getEntryPoint()
i = getInstructionAt(addr)
print("[*] Searching for CODECOPY operands...")
codecopy_list = []
while True:
codecopy_operands = []
nem = i.getMnemonicString()
if nem == "CODECOPY":
print("\tCODECOPY found at", i.getAddress())
j = i.getPrevious()
# look in the last 10 instructions for the CODECOPY arguments
for ins in range(1, 10):
if (j.getMnemonicString().startswith("PUSH")):
codecopy_operands.append(str(j.getOpObjects(0)[0]))
j = j.getPrevious()
# we only care about CODECOPY instructions
# with memory offsets at 0, generally they
# contain memory areas covered by other
# CODECOPYs with memory offsets != 0.
if (len(codecopy_operands) >= 3):
if(codecopy_operands[0] == "0x0"):
codecopy_elem = {}
codecopy_elem['addr'] = codecopy_operands[1]
codecopy_elem['size'] = codecopy_operands[2]
codecopy_list.append(codecopy_elem)
i = i.getNext()
if i is None:
break
for i in codecopy_list:
copy_addr = i['addr']
copy_size = i['size']
evm_code = read_ram(ram, copy_addr, copy_size)
addr_ram = ram.getStart().add(int(copy_addr, 16))
evm_jump_table = memory.getBlock("evm_jump_table")
cfg = fill_jump_table(evm_code, evm_jump_table, copy_addr)
explore_functions(cfg, copy_addr)
print("[*] Analyzing....")
analyzeAll(currentProgram)
print("[*] Disassemble all....")
disassemble(ram.getStart().add(int(copy_addr, 16)))
currentProgram.endTransaction(tid,True)