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import sys
import shutil
from elftools.elf.elffile import ELFFile
from capstone import *
from capstone.x86 import *
if len(sys.argv) < 2:
print(f"Usage: {sys.argv[0]} [path to discord_krisp.node]")
# "Unix programs generally use 2 for command line syntax errors and 1 for all other kind of errors."
sys.exit(2)
executable = sys.argv[1]
elf = ELFFile(open(executable, "rb"))
symtab = elf.get_section_by_name('.symtab')
krisp_initialize_address = symtab.get_symbol_by_name("_ZN7discord15KrispInitializeEv")[0].entry.st_value
isSignedByDiscord_address = symtab.get_symbol_by_name("_ZN7discord4util17IsSignedByDiscordERKNSt4__Cr12basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE")[0].entry.st_value
text = elf.get_section_by_name('.text')
text_start = text['sh_addr']
text_start_file = text['sh_offset']
# This seems to always be zero (.text starts at the right offset in the file). Do it just in case?
address_to_file = text_start_file - text_start
# Done with the ELF now.
# elf.close()
krisp_initialize_offset = krisp_initialize_address - address_to_file
isSignedByDiscord_offset = krisp_initialize_address - address_to_file
f = open(executable, "rb")
f.seek(krisp_initialize_offset)
krisp_initialize = f.read(64)
f.close()
# States
found_issigned_by_discord_call = False
found_issigned_by_discord_test = False
found_issigned_by_discord_je = False
found_already_patched = False
je_location = None
# We are looking for a call to IsSignedByDiscord, followed by a test, followed by a je.
# Then we patch the je into a two byte nop.
md = Cs(CS_ARCH_X86, CS_MODE_64)
md.detail = True
for i in md.disasm(krisp_initialize, krisp_initialize_address):
if i.id == X86_INS_CALL:
if i.operands[0].type == X86_OP_IMM:
if i.operands[0].imm == isSignedByDiscord_address:
found_issigned_by_discord_call = True
if i.id == X86_INS_TEST:
if found_issigned_by_discord_call:
found_issigned_by_discord_test = True
if i.id == X86_INS_JE:
if found_issigned_by_discord_test:
found_issigned_by_discord_je = True
je_location = i.address
break
if i.id == X86_INS_NOP:
if found_issigned_by_discord_test:
found_already_patched = True
break
if je_location:
print(f"Found patch location: 0x{je_location:x}")
shutil.copyfile(executable, executable + ".orig")
f = open(executable, 'rb+')
f.seek(je_location - address_to_file)
f.write(b'\x66\x90') # Two byte NOP
f.close()
else:
if found_already_patched:
print("Couldn't find patch location - already patched.")
else:
print("Couldn't find patch location - review manually. Sorry.")
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