Created
September 16, 2019 05:09
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Decrypt Emotet Stirng
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| from __future__ import print_function | |
| import idc | |
| import idaapi | |
| import idautils | |
| import flare_emu | |
| import unicorn | |
| # test sample https://www.virustotal.com/gui/file/c7a9609c212f275415e678ac7452f19aa9fbc39f9c1fd2708f43629edfd28a3e/detection | |
| decrypted_blocks = [] | |
| def ins_hook(unicornObject, address, instructionSize, userData): | |
| global decrypted_blocks | |
| if address == 0x00401BF8: | |
| eh = userData["EmuHelper"] | |
| decrypted_len = unicornObject.reg_read(unicorn.x86_const.UC_X86_REG_EAX) | |
| print('string len:{}'.format(decrypted_len)) | |
| decrypted_addr = unicornObject.reg_read(unicorn.x86_const.UC_X86_REG_EDI) | |
| print('#####################\n addr : {:08x}'.format(decrypted_addr)) | |
| buf = eh.getEmuBytes(decrypted_addr, (decrypted_len+1)*2) | |
| result = '' | |
| for idx in range(0, (decrypted_len)*2, 2): | |
| result += buf[idx] | |
| decrypted_blocks.append(result) | |
| print('size:{} data:{}'.format(len(buf), result)) | |
| print('#####################\n') | |
| def iterateHook(eh, address, argv, userData): | |
| decrypt_fun_name = 'DecryptString_401B60' | |
| print('\n0x{:08x}:call {}'.format(address, decrypt_fun_name)) | |
| argv_hex = [hex(x) for x in argv] | |
| key = eh.getRegVal('ecx') | |
| len_ = eh.getRegVal('edx') | |
| print('-------------', hex(key), hex(len_), argv_hex) | |
| if len_ > 1000: | |
| print('TOO LONG:{}'.format(len_)) | |
| return | |
| myEH = flare_emu.EmuHelper() | |
| mu = myEH.emulateRange(idc.get_name_ea_simple(decrypt_fun_name), | |
| registers = {'ecx':key, 'edx':len_ }, | |
| instructionHook=ins_hook, stack = [0, argv[0]]) | |
| ret = myEH.getRegVal('eax') | |
| print(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>> start") | |
| eh = flare_emu.EmuHelper() | |
| eh.iterate(idc.get_name_ea_simple("DecryptString_401B60"), iterateHook) | |
| # eh.iterate(idc.get_name_ea_simple("DecryptStirng_401AD0"), iterateHook) | |
| print(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>> results") | |
| print('\n'.join(decrypted_blocks)) | |
| print('end') |
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