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[Android 原创] 汇编与反汇编神器Unicorn

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Richor 发表于 2019-9-19 15:40
我们来先说说Unicorn有啥子卵用。
Unicorn 是一款非常优秀的跨平台模拟执行框架,该框架可以跨平台执行Arm, Arm64 (Armv8), M68K, Mips, Sparc, & X86 (include X86_64)等指令集的原生程序。
好了说得那么官方,我们举个例子好了,研究OLLVM的时候是不是很头疼函数的地址,使用Unicorn就可以打印函数注册地址,已经参数名称,用某音的so来演示一下Unicorn的威力
[Asm] 纯文本查看 复制代码
RegisterNatives dvmClass=com/ss/android/common/applog/UserInfo, name=getUserInfo, signature=(ILjava/lang/String;[Ljava/lang/String;)Ljava/lang/String;, fnPtr=unicorn@0x4002c6c5[libcms.so]0x2c6c5
RegisterNatives dvmClass=com/ss/android/common/applog/UserInfo, name=getUserInfo, signature=(ILjava/lang/String;[Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;, fnPtr=unicorn@0x4002c6dd[libcms.so]0x2c6dd
RegisterNatives dvmClass=com/ss/android/common/applog/UserInfo, name=getUserInfoSkipGet, signature=(ILjava/lang/String;[Ljava/lang/String;)Ljava/lang/String;, fnPtr=unicorn@0x4002c7b1[libcms.so]0x2c7b1
RegisterNatives dvmClass=com/ss/android/common/applog/UserInfo, name=getUserInfo, signature=(I[Ljava/lang/String;[Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;, fnPtr=unicorn@0x4002c7d1[libcms.so]0x2c7d1
RegisterNatives dvmClass=com/ss/android/common/applog/UserInfo, name=getPackage, signature=(Ljava/lang/String;)V, fnPtr=unicorn@0x4002e0dd[libcms.so]0x2e0dd

1

1

很快就可以找到UserInfo的函数地址了,不管是Hook还是直接动态调试都是事半功倍。
(当初我找函数地址,找到想哭)

表情

表情

好了,开始Unicorn的入门
Unicorn 快速入门
多架构
Unicorn 是一款基于qemu模拟器的模拟执行框架,支持Arm, Arm64 (Armv8), M68K, Mips, Sparc, & X86 (include X86_64)等指令集。

多语言
Unicorn 为多种语言提供编程接口比如C/C++、Python、Java 等语言。Unicorn的DLL 可以被更多的语言调用,比如易语言、Delphi,前途无量。

多线程安全
Unicorn 设计之初就考虑到线程安全问题,能够同时并发模拟执行代码,极大的提高了实用性。

虚拟内存
Unicorn 采用虚拟内存机制,使得虚拟CPU的内存与真实CPU的内存隔离。Unicorn 使用如下API来操作内存:

uc_mem_map
uc_mem_read
uc_mem_write
使用uc_mem_map映射内存的时候,address 与 size 都需要与0x1000对齐,也就是0x1000的整数倍,否则会报UC_ERR_ARG 异常。如何动态分配管理内存并实现libc中的malloc功能将在后面的课程中讲解。
Hook 机制
Unicorn的Hook机制为编程控制虚拟CPU提供了便利。
Unicorn 支持多种不同类型的Hook。
大致可以分为(hook_add第一参数,Unicorn常量):
指令执行类

UC_HOOK_INTR
UC_HOOK_INSN
UC_HOOK_CODE
UC_HOOK_BLOCK
内存访问类

UC_HOOK_MEM_READ
UC_HOOK_MEM_WRITE
UC_HOOK_MEM_FETCH
UC_HOOK_MEM_READ_AFTER
UC_HOOK_MEM_PROT
UC_HOOK_MEM_FETCH_INVALID
UC_HOOK_MEM_INVALID
UC_HOOK_MEM_VALID
异常处理类

UC_HOOK_MEM_READ_UNMAPPED
UC_HOOK_MEM_WRITE_UNMAPPED
UC_HOOK_MEM_FETCH_UNMAPPED
调用hook_add函数可添加一个Hook。Unicorn的Hook是链式的,而不是传统Hook的覆盖式,也就是说,可以同时添加多个同类型的Hook,Unicorn会依次调用每一个handler。hook callback 是有作用范围的(见hook_add begin参数)。
我们来写一个举一个简单的栗子:
先装一下Unicorn的导入包
[Asm] 纯文本查看 复制代码
	
pip install unicorn

然后新建一个py文件
[Python] 纯文本查看 复制代码
from unicorn import *
from unicorn.arm_const import *

ARM_CODE = b"\x37\x00\xa0\xe3\x03\x10\x42\xe0"


# mov r0, #0x37;
# sub r1, r2, r3
# Test ARM

# callback for tracing instructions
def hook_code(uc, address, size, user_data):
    print(">>> Tracing instruction at 0x%x, instruction size = 0x%x" % (address, size))


def test_arm():
    print("Emulate ARM code")
    try:
        # Initialize emulator in ARM mode
        mu = Uc(UC_ARCH_ARM, UC_MODE_THUMB) #创建UC对象

        # map 2MB memory for this emulation 创建2MB的内存空间
        ADDRESS = 0x10000
        mu.mem_map(ADDRESS, 2 * 0x10000)
        mu.mem_write(ADDRESS, ARM_CODE) #将前面定义的ARM_CODE传入内存空间内,只支持byte

        #未开机前寄存器赋值
        mu.reg_write(UC_ARM_REG_R0, 0x1234)
        mu.reg_write(UC_ARM_REG_R2, 0x6789)
        mu.reg_write(UC_ARM_REG_R3, 0x3333)
        #添加指令集Hook
#        mu.hook_add(UC_HOOK_CODE, hook_code, begin=ADDRESS, end=ADDRESS)

        # emulate machine code in infinite time,开机
        mu.emu_start(ADDRESS, ADDRESS + len(ARM_CODE))
        print("已开机")
        #获取计算器结果
        r0 = mu.reg_read(UC_ARM_REG_R0)
        r1 = mu.reg_read(UC_ARM_REG_R1)
        print(">>> R0 = 0x%x" % r0)
        print(">>> R1 = 0x%x" % r1)
    except UcError as e:
        print("ERROR: %s" % e)

test_arm()

我把核心的位置都写了备注,这样很明显了吧
我们看看运行结果

2

2

R0寄存器的就变成了0x37,R1=0x3456,
上面我们明明没有对R1寄存器进行任何操作,为什么R1会有值呢?

3

3

于是我们引入第二个汇编神器Capstone
其实ARM_CODE = b"\x37\x00\xa0\xe3\x03\x10\x42\xe0"就是对寄存器的操作
我们用Capstone来翻译看看是什么指令
先插个件
[Asm] 纯文本查看 复制代码
pip install capstone

建个py文件
[Python] 纯文本查看 复制代码
from capstone import *
from capstone.arm import *

CODE = b"\x37\x00\xa0\xe3\x03\x10\x42\xe0"

md = Cs(CS_ARCH_ARM, CS_MODE_ARM)
for i in md.disasm(CODE, 0x1000):
    print("%x:\t%s\t%s" % (i.address, i.mnemonic, i.op_str))

查看运行结果

4

4

这个总是看得懂了吧,就是简单arm的指令R1=R2-R3

5

5

接下来你们肯定关心怎么打印地址?怎么让Unicorn想普通模拟器可以单步调试对不对?

6

6

无名大佬写了一个调试,我们来看看这个调试器的源码
(本菜是无名大佬的脑残粉)
[Python] 纯文本查看 复制代码
from unicorn import *
from unicorn import arm_const
from unicorn.arm_const import *
import sys
import hexdump
import capstone as cp

BPT_EXECUTE = 1
BPT_MEMREAD = 2
UDBG_MODE_ALL = 1
UDBG_MODE_FAST = 2

REG_ARM = {arm_const.UC_ARM_REG_R0: "R0",
           arm_const.UC_ARM_REG_R1: "R1",
           arm_const.UC_ARM_REG_R2: "R2",
           arm_const.UC_ARM_REG_R3: "R3",
           arm_const.UC_ARM_REG_R4: "R4",
           arm_const.UC_ARM_REG_R5: "R5",
           arm_const.UC_ARM_REG_R6: "R6",
           arm_const.UC_ARM_REG_R7: "R7",
           arm_const.UC_ARM_REG_R8: "R8",
           arm_const.UC_ARM_REG_R9: "R9",
           arm_const.UC_ARM_REG_R10: "R10",
           arm_const.UC_ARM_REG_R11: "R11",
           arm_const.UC_ARM_REG_R12: "R12",
           arm_const.UC_ARM_REG_R13: "R13",
           arm_const.UC_ARM_REG_R14: "R14",
           arm_const.UC_ARM_REG_R15: "R15",
           arm_const.UC_ARM_REG_PC: "PC",
           arm_const.UC_ARM_REG_SP: "SP",
           arm_const.UC_ARM_REG_LR: "LR"
           }

REG_TABLE = {UC_ARCH_ARM: REG_ARM}


def str2int(s):
    if s.startswith('0x') or s.startswith("0X"):
        return int(s[2:], 16)
    return int(s)


def advance_dump(data, base):
    PY3K = sys.version_info >= (3, 0)
    generator = hexdump.genchunks(data, 16)
    retstr = ''
    for addr, d in enumerate(generator):
        # 00000000:
        line = '%08X: ' % (base + addr * 16)
        # 00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
        dumpstr = hexdump.dump(d)
        line += dumpstr[:8 * 3]
        if len(d) > 8:  # insert separator if needed
            line += ' ' + dumpstr[8 * 3:]
        # ................
        # calculate indentation, which may be different for the last line
        pad = 2
        if len(d) < 16:
            pad += 3 * (16 - len(d))
        if len(d) <= 8:
            pad += 1
        line += ' ' * pad

        for byte in d:
            # printable ASCII range 0x20 to 0x7E
            if not PY3K:
                byte = ord(byte)
            if 0x20 <= byte <= 0x7E:
                line += chr(byte)
            else:
                line += '.'
        retstr += line + '\n'
    return retstr


def _dbg_trace(mu, address, size, self):
    self._tracks.append(address)
    if not self._is_step and self._tmp_bpt == 0:
        if address not in self._list_bpt:
            return

    if self._tmp_bpt != address and self._tmp_bpt != 0:
        return

    return _dbg_trace_internal(mu, address, size, self)


def _dbg_memory(mu, access, address, length, value, self):
    pc = mu.reg_read(arm_const.UC_ARM_REG_PC)
    print("memory error: pc: %x access: %x address: %x length: %x value: %x" %
          (pc, access, address, length, value))
    _dbg_trace_internal(mu, pc, 4, self)
    mu.emu_stop()
    return True


def _dbg_trace_internal(mu, address, size, self):
    self._is_step = False
    print("======================= Registers =======================")
    self.dump_reg()
    print("======================= Disassembly =====================")
    self.dump_asm(address, size * self.dis_count)

    while True:
        raw_command = input(">")
        if raw_command == '':
            raw_command = self._last_command
        self._last_command = raw_command
        command = []
        for c in raw_command.split(" "):
            if c != "":
                command.append(c)
        try:
            if command[0] == 'set':
                if command[1] == 'reg':  # set reg regname value
                    self.write_reg(command[2], str2int(command[3]))
                elif command[1] == 'bpt':
                    self.add_bpt(str2int(command[2]))
                else:
                    print("[Debugger Error]command error see help.")

            elif command[0] == 's' or command[0] == 'step':
                # self._tmp_bpt = address + size
                self._tmp_bpt = 0
                self._is_step = True
                break
            elif command[0] == 'n' or command[0] == 'next':
                self._tmp_bpt = address + size
                self._is_step = False
                break

            elif command[0] == 'r' or command[0] == 'run':
                self._tmp_bpt = 0
                self._is_step = False
                break
            elif command[0] == 'dump':
                if len(command) >= 3:
                    nsize = str2int(command[2])
                else:
                    nsize = 4 * 16
                self.dump_mem(str2int(command[1]), nsize)
            elif command[0] == 'list':
                if command[1] == 'bpt':
                    self.list_bpt()
            elif command[0] == 'del':
                if command[1] == 'bpt':
                    self.del_bpt(str2int(command[2]))
            elif command[0] == 'stop':
                exit(0)
            elif command[0] == 't':
                self._castone = self._capstone_thumb
                print("======================= Disassembly =====================")
                self.dump_asm(address, size * self.dis_count)
            elif command[0] == 'a':
                self._castone = self._capstone_arm
                print("======================= Disassembly =====================")
                self.dump_asm(address, size * self.dis_count)
            elif command[0] == 'f':
                print(" == recent ==")
                for i in self._tracks[-10:-1]:
                    print(self.sym_handler(i))
            else:
                print("Command Not Found!")

        except:
            print("[Debugger Error]command error see help.")


class UnicornDebugger:
    def __init__(self, mu, mode=UDBG_MODE_ALL):
        self._tracks = []
        self._mu = mu
        self._arch = mu._arch
        self._mode = mu._mode
        self._list_bpt = []
        self._tmp_bpt = 0
        self._error = ''
        self._last_command = ''
        self.dis_count = 5
        self._is_step = False
        self.sym_handler = self._default_sym_handler
        self._capstone_arm = None
        self._capstone_thumb = None

        if self._arch != UC_ARCH_ARM:
            mu.emu_stop()
            raise RuntimeError("arch:%d is not supported! " % self._arch)

        if self._arch == UC_ARCH_ARM:
            capstone_arch = cp.CS_ARCH_ARM
        elif self._arch == UC_ARCH_ARM64:
            capstone_arch = cp.CS_ARCH_ARM64
        elif self._arch == UC_ARCH_X86:
            capstone_arch = cp.CS_ARCH_X86
        else:
            mu.emu_stop()
            raise RuntimeError("arch:%d is not supported! " % self._arch)

        if self._mode == UC_MODE_THUMB:
            capstone_mode = cp.CS_MODE_THUMB
        elif self._mode == UC_MODE_ARM:
            capstone_mode = cp.CS_MODE_ARM
        elif self._mode == UC_MODE_32:
            capstone_mode = cp.CS_MODE_32
        elif self._mode == UC_MODE_64:
            capstone_mode = cp.CS_MODE_64
        else:
            mu.emu_stop()
            raise RuntimeError("mode:%d is not supported! " % self._mode)

        self._capstone_thumb = cp.Cs(cp.CS_ARCH_ARM, cp.CS_MODE_THUMB)
        self._capstone_arm = cp.Cs(cp.CS_ARCH_ARM, cp.CS_MODE_ARM)

        self._capstone = self._capstone_thumb

        if mode == UDBG_MODE_ALL:
            mu.hook_add(UC_HOOK_CODE, _dbg_trace, self)

        mu.hook_add(UC_HOOK_MEM_UNMAPPED, _dbg_memory, self)
        mu.hook_add(UC_HOOK_MEM_FETCH_PROT, _dbg_memory, self)

        self._regs = REG_TABLE[self._arch]

    def dump_mem(self, addr, size):
        data = self._mu.mem_read(addr, size)
        print(advance_dump(data, addr))

    def dump_asm(self, addr, size):
        md = self._capstone
        code = self._mu.mem_read(addr, size)
        count = 0
        for ins in md.disasm(code, addr):
            if count >= self.dis_count:
                break
            print("%s:\t%s\t%s" % (self.sym_handler(ins.address), ins.mnemonic, ins.op_str))

    def dump_reg(self):
        result_format = ''
        count = 0
        for rid in self._regs:
            rname = self._regs[rid]
            value = self._mu.reg_read(rid)
            if count < 4:
                result_format = result_format + '  ' + rname + '=' + hex(value)
                count += 1
            else:
                count = 0
                result_format += '\n' + rname + '=' + hex(value)
        print(result_format)

    def write_reg(self, reg_name, value):
        for rid in self._regs:
            rname = self._regs[rid]
            if rname == reg_name:
                self._mu.reg_write(rid, value)
                return
        print("[Debugger Error] Reg not found:%s " % reg_name)

    def show_help(self):
        help_info = """
        # commands
        # set reg <regname> <value>
        # set bpt <addr>
        # n[ext]
        # s[etp]
        # r[un]
        # dump <addr> <size>
        # list bpt
        # del bpt <addr>
        # stop
        # a/t change arm/thumb
        # f show ins flow
        """
        print(help_info)

    def list_bpt(self):
        for idx in range(len(self._list_bpt)):
            print("[%d] %s" % (idx, self.sym_handler(self._list_bpt[idx])))

    def add_bpt(self, addr):
        self._list_bpt.append(addr)

    def del_bpt(self, addr):
        self._list_bpt.remove(addr)

    def get_tracks(self):
        for i in self._tracks[-100:-1]:
            # print (self.sym_handler(i))
            pass
        return self._tracks

    def _default_sym_handler(self, address):
        return hex(address)

    def set_symbol_name_handler(self, handler):
        self.sym_handler = handler


def test_arm():
    print("Emulate Thumb code")
    THUMB = b"\x37\x00\xa0\xe3\x03\x10\x42\xe0"
    # sub    sp, #0xc
    # sub    sp, #0xc
    # sub    sp, #0xc
    try:
        # Initialize emulator in ARM mrode
        mu = Uc(UC_ARCH_ARM, UC_MODE_THUMB)

        # map 2MB memory for this emulation
        ADDRESS = 0x10000
        mu.mem_map(ADDRESS, 2 * 0x10000)
        mu.mem_write(ADDRESS, THUMB)

        mu.reg_write(UC_ARM_REG_SP, 0x1234)
        mu.reg_write(UC_ARM_REG_R2, 0x6789)

        # debugger attach
        udbg = UnicornDebugger(mu)
        udbg.add_bpt(ADDRESS)

        # emulate machine code in infinite time
        mu.emu_start(ADDRESS, ADDRESS + len(THUMB))
        r0 = mu.reg_read(UC_ARM_REG_SP)
        r1 = mu.reg_read(UC_ARM_REG_R1)
        print(">>> SP = 0x%x" % r0)
        print(">>> R1 = 0x%x" % r1)
    except UcError as e:
        print("ERROR: %s" % e)

test_arm()

我们看看运行结果

7

7

寄存器的值,和反编译后的指令都显示出来了
接下来就是输入指令了,step,run,next,这是不是跟F8,F9,F10,步入,步过,运行很像呢
这个大家可以自己去尝试以下,我就直接run了

8

8

值都打印出来啦。
这些都是Unicorn的基础,那些大佬已经基于Unicorn写出很多很强大的逆向工具,大家有兴趣可以自己找找

9

9

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75769837 发表于 2019-9-19 16:23
这个不是从看雪那边搬过来的嘛?
加了几个图片
 楼主| Richor 发表于 2019-9-19 17:48
75769837 发表于 2019-9-19 17:45
https://bbs.pediy.com/thread-253868.htm
和这个帖子 和 内容 以及其公布的调用抖音So的项目有啥大点 ...

没看清楚内容么?我说了调试器是无名写的,但是抖音so调用,你有本事倒是做个出来看看啊?
高苗苗 发表于 2019-9-19 16:01
三枫大神 发表于 2019-9-19 16:17
工具呢在哪呢?
 楼主| Richor 发表于 2019-9-19 16:26
75769837 发表于 2019-9-19 16:23
这个不是从看雪那边搬过来的嘛?
加了几个图片

来,你给我搬运一个某音so地址打印
qybl999 发表于 2019-9-19 16:44
工具怎么下
头像被屏蔽
Zeno___Lee 发表于 2019-9-19 17:40
大佬来一个汇编入门的自学链接呗
75769837 发表于 2019-9-19 17:45
Richor 发表于 2019-9-19 16:26
来,你给我搬运一个某音so地址打印

https://bbs.pediy.com/thread-253868.htm
和这个帖子 和 内容 以及其公布的调用抖音So的项目有啥大点的区别嘛?
一人之下123456 发表于 2019-9-19 17:56
虽然看不懂,但感觉好厉害。收藏了,有需要再下载研究一下。
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