这道题主要考察的是对多层jni调用的模拟，所谓多层jni调用指native java函数的实现c/c++函数中又反过来调用java函数，而这个被调用的java函数仍然是一个native函数。而对于AndroidNativeEmu和UniDbg目前(做题的时候)都不支持这种多层调用，UniDbg更新应该算是比较频繁的，有可能后边会支持。
不能直接支持，只能用取巧的方式来实现。我这里用了两个程序来实现，一个程序通过subprocess来调用另外一个程序，获取这个程序的结果进一步利用。这种实现方式是有缺陷的，如果模拟的程序函数对全局的变量产生了副作用，或者有共同的依赖，那么模拟可能会失败，在这种情况下需要做特殊的处理，单独处理同步共享的全局变量。
通过这个题目的练习可以学得AndroidNativeEmu和UniDbg不支持的地方，或者说有待改进的点。工具不支持，必要时必须自己写代码扩展功能。
单独为crypt2函数写一个源文件,crypt2_impl.py文件内容为:
main.py文件内容:
当输入值为'XUe'时打印出来的结果为:
当输入值不为'XUe'时打印出来的结果为:
模拟成功。
import logging
import sys
from androidemu.emulator import Emulator
from androidemu.java.helpers.native_method import native_method
from androidemu.utils import memory_helpers
@native_method
def sprintf(uc, str, format, args):
str_utf8 = memory_helpers.read_utf8(uc, str)
format_utf8 = memory_helpers.read_utf8(uc, format)
args_utf8 = memory_helpers.read_utf8(uc, args)
logger.info("str_utf8:{}, format_utf8:{}, args_utf8:{}".format(str_utf8, format_utf8, args_utf8))
result_string = format_utf8 % args_utf8
memory_helpers.write_utf8(uc, str, result_string)
return len(result_string)
@native_method
def malloc(uc, size):
return emulator.memory_manager.allocate(size)
@native_method
def strcmp(uc, s1, s2):
s1_utf8 = memory_helpers.read_utf8(uc, s1)
s2_utf8 = memory_helpers.read_utf8(uc, s2)
if s1_utf8 == s2_utf8:
ret = 0
elif s1_utf8 < s2_utf8:
ret = -1
else:
ret = 1
logger.info("s1:{},s2:{},ret:{}".format(s1_utf8, s2_utf8, ret))
return ret
logging.basicConfig(
stream=sys.stderr,
level=logging.DEBUG,
format="%(asctime)s %(levelname)7s %(name)34s | %(message)s"
)
logger = logging.getLogger(__name__)
so_file = "my_binaries/libnative-lib.so"
libc_file = "example_binaries/32/libc.so"
emulator = Emulator(vfp_inst_set=True)
emulator.modules.add_symbol_hook('sprintf', emulator.hooker.write_function(sprintf) + 1)
emulator.modules.add_symbol_hook('malloc', emulator.hooker.write_function(malloc) + 1)
emulator.modules.add_symbol_hook('strcmp', emulator.hooker.write_function(strcmp) + 1)
libc_module = emulator.load_library(libc_file, do_init=False)
lib_module = emulator.load_library(so_file, do_init=False)
emulator.call_native(lib_module.base + 0x320B8 + 1)
for funcptr in lib_module.init_array:
logger.info("init_array -->" + str(hex(funcptr)))
emulator.call_native(funcptr)
result = emulator.call_symbol(lib_module, "Java_com_kanxue_crackme_MainActivity_crypt2",
emulator.java_vm.jni_env.address_ptr, 0, sys.argv[1], is_return_jobject=False)
print(result)
import logging
import sys
from androidemu.emulator import Emulator
from androidemu.java.helpers.native_method import native_method
from androidemu.utils import memory_helpers
@native_method
def sprintf(uc, str, format, args):
str_utf8 = memory_helpers.read_utf8(uc, str)
format_utf8 = memory_helpers.read_utf8(uc, format)
args_utf8 = memory_helpers.read_utf8(uc, args)
logger.info("str_utf8:{}, format_utf8:{}, args_utf8:{}".format(str_utf8, format_utf8, args_utf8))
result_string = format_utf8 % args_utf8
memory_helpers.write_utf8(uc, str, result_string)
return len(result_string)
@native_method
def malloc(uc, size):
return emulator.memory_manager.allocate(size)
@native_method
def strcmp(uc, s1, s2):
s1_utf8 = memory_helpers.read_utf8(uc, s1)
s2_utf8 = memory_helpers.read_utf8(uc, s2)
if s1_utf8 == s2_utf8:
ret = 0
elif s1_utf8 < s2_utf8:
ret = -1
else:
ret = 1
logger.info("s1:{},s2:{},ret:{}".format(s1_utf8, s2_utf8, ret))
return ret
logging.basicConfig(
stream=sys.stderr,
level=logging.DEBUG,
format="%(asctime)s %(levelname)7s %(name)34s | %(message)s"
)
logger = logging.getLogger(__name__)
so_file = "my_binaries/libnative-lib.so"
libc_file = "example_binaries/32/libc.so"
emulator = Emulator(vfp_inst_set=True)
emulator.modules.add_symbol_hook('sprintf', emulator.hooker.write_function(sprintf) + 1)
emulator.modules.add_symbol_hook('malloc', emulator.hooker.write_function(malloc) + 1)
emulator.modules.add_symbol_hook('strcmp', emulator.hooker.write_function(strcmp) + 1)
libc_module = emulator.load_library(libc_file, do_init=False)
lib_module = emulator.load_library(so_file, do_init=False)
emulator.call_native(lib_module.base + 0x320B8 + 1)
for funcptr in lib_module.init_array:
logger.info("init_array -->" + str(hex(funcptr)))
emulator.call_native(funcptr)
result = emulator.call_symbol(lib_module, "Java_com_kanxue_crackme_MainActivity_crypt2",
emulator.java_vm.jni_env.address_ptr, 0, sys.argv[1], is_return_jobject=False)
print(result)
import logging
import sys
import unicorn
import capstone
from androidemu.emulator import Emulator
from androidemu.utils import memory_helpers
from androidemu.java.java_class_def import JavaClassDef
from androidemu.java.java_method_def import java_method_def
from androidemu.java.helpers.native_method import native_method
from subprocess import check_output
cs = capstone.Cs(capstone.CS_ARCH_ARM, capstone.CS_MODE_THUMB)
cs.detail = True
class MainActivity(metaclass=JavaClassDef, jvm_name='com/kanxue/crackme/MainActivity'):
def __init__(self):
pass
@java_method_def(name='crypt2', args_list=['jstring'], signature='(Ljava/lang/String;)Z', native=False)
def crypt2(self, *args, **kwargs):
arg = args[0].value
print("crypt2 args : {}".format(arg))
ret = check_output(["python","crypt2_impl.py",arg])
ret = int(ret.decode('utf-8').strip())
print("crypt2 result : {}".format(ret))
return ret
@native_method
def sprintf(uc, str, format, args):
str_utf8 = memory_helpers.read_utf8(uc, str)
format_utf8 = memory_helpers.read_utf8(uc, format)
args_utf8 = memory_helpers.read_utf8(uc, args)
print("str_utf8:{}, format_utf8:{}, args_utf8:{}".format(str_utf8, format_utf8, args_utf8))
result_string = format_utf8 % args_utf8
memory_helpers.write_utf8(uc, str, result_string)
return len(result_string)
@native_method
def malloc(uc, size):
return emulator.memory_manager.allocate(size)
@native_method
def strcmp(uc, s1, s2):
s1_utf8 = memory_helpers.read_utf8(uc, s1)
s2_utf8 = memory_helpers.read_utf8(uc, s2)
if s1_utf8 == s2_utf8:
return 0
print("s1:{},s2:{}".format(s1_utf8, s2_utf8))
return len(s1_utf8) - len(s2_utf8)
logging.basicConfig(
stream=sys.stdout,
level=logging.DEBUG,
format="%(asctime)s %(levelname)7s %(name)34s | %(message)s"
)
logger = logging.getLogger(__name__)
def mem_read_unmapped(uc, type, address, size, value, user_data):
print("mem_read_unmapped type:{},address:{},size:{},value:{},pc:{}".format(type, address, size, value,
hex(uc.reg_read(
unicorn.arm_const.UC_ARM_REG_PC) - libc_module.base)))
def hook_code(uc, address, size, user_data):
if lib_module.base < address < (lib_module.base + lib_module.size):
lib_name = "libnative-lib.so"
pc = uc.reg_read(unicorn.arm_const.UC_ARM_REG_PC) - lib_module.base
elif libc_module.base < address < (libc_module.base + libc_module.size):
lib_name = "libc.so"
pc = uc.reg_read(unicorn.arm_const.UC_ARM_REG_PC) - libc_module.base
else:
lib_name = "lib_Unknown"
pc = uc.reg_read(unicorn.arm_const.UC_ARM_REG_PC)
CODE = uc.mem_read(uc.reg_read(unicorn.arm_const.UC_ARM_REG_PC), size)
dis_code = None
for i in cs.disasm(CODE, 0, len(CODE)):
dis_code = i.mnemonic + " " + i.op_str
print(lib_name + " >>> Tracing instruction at {}, instruction size = {} , pc:{}, bytes:{}".format(pc, size,
hex(pc),
dis_code))
def UC_HOOK_MEM_WRITE(uc, type, address, size, value, userdata):
print("address:" + str(hex(address)) + ",value:" + str(value))
so_file = "my_binaries/libnative-lib.so"
libc_file = "example_binaries/32/libc.so"
emulator = Emulator(vfp_inst_set=True)
emulator.modules.add_symbol_hook('sprintf', emulator.hooker.write_function(sprintf) + 1)
emulator.modules.add_symbol_hook('malloc', emulator.hooker.write_function(malloc) + 1)
emulator.modules.add_symbol_hook('strcmp', emulator.hooker.write_function(strcmp) + 1)
libc_module = emulator.load_library(libc_file, do_init=False)
lib_module = emulator.load_library(so_file, do_init=False)
emulator.call_native(lib_module.base + 0x320B8 + 1)
for funcptr in lib_module.init_array:
logger.info("init_array -->" + str(hex(funcptr)))
emulator.call_native(funcptr)
emulator.java_classloader.add_class(MainActivity)
result = emulator.call_symbol(lib_module, "Java_com_kanxue_crackme_MainActivity_jnicheck",
emulator.java_vm.jni_env.address_ptr, 0, "XUe", is_return_jobject=False)
print("jnicheck result : {}".format(result))
import logging
import sys
import unicorn
import capstone
from androidemu.emulator import Emulator
from androidemu.utils import memory_helpers
from androidemu.java.java_class_def import JavaClassDef
from androidemu.java.java_method_def import java_method_def
from androidemu.java.helpers.native_method import native_method
from subprocess import check_output
cs = capstone.Cs(capstone.CS_ARCH_ARM, capstone.CS_MODE_THUMB)
cs.detail = True
class MainActivity(metaclass=JavaClassDef, jvm_name='com/kanxue/crackme/MainActivity'):
def __init__(self):
pass
@java_method_def(name='crypt2', args_list=['jstring'], signature='(Ljava/lang/String;)Z', native=False)
def crypt2(self, *args, **kwargs):
arg = args[0].value
print("crypt2 args : {}".format(arg))
ret = check_output(["python","crypt2_impl.py",arg])
ret = int(ret.decode('utf-8').strip())
print("crypt2 result : {}".format(ret))
return ret
@native_method
def sprintf(uc, str, format, args):
str_utf8 = memory_helpers.read_utf8(uc, str)
format_utf8 = memory_helpers.read_utf8(uc, format)
args_utf8 = memory_helpers.read_utf8(uc, args)
print("str_utf8:{}, format_utf8:{}, args_utf8:{}".format(str_utf8, format_utf8, args_utf8))
result_string = format_utf8 % args_utf8
memory_helpers.write_utf8(uc, str, result_string)
return len(result_string)
@native_method
def malloc(uc, size):
return emulator.memory_manager.allocate(size)
@native_method
def strcmp(uc, s1, s2):
s1_utf8 = memory_helpers.read_utf8(uc, s1)
s2_utf8 = memory_helpers.read_utf8(uc, s2)
if s1_utf8 == s2_utf8:
return 0
print("s1:{},s2:{}".format(s1_utf8, s2_utf8))
return len(s1_utf8) - len(s2_utf8)
logging.basicConfig(
stream=sys.stdout,
level=logging.DEBUG,
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最后于 2022-7-17 18:06
被飞翔的猫咪编辑
，原因：
