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[原创]2022祥云杯CTF babyparser
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发表于: 2022-11-25 20:43
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这道题是比赛结束前3小时放出来的， 最后是0解。 我有理由怀疑这是一道防ak题。
原题附件需要glibc2.34，但我的kali版本不够高，所以我patchelf成自编译的2.34，也因此搞丢了原题附件，现在上传的是patchelf以后的版本， 如果有需要可以自己patch回去。
比赛时候打开一看啊，发现这个程序用了ollvm的deflat来进行混淆，而且仔细一看是个全混淆，所有能混淆的地方它都混淆了。还好之前有所准备，拿起了之前备好的脚本准备一把梭。 梭完一看发现失败了，原来是这个ollvm改良过，出题人修改了deflat的llvm pass ，分发逻辑增加了一步。 其中真实块的样子大概是这样的
这时候我以为出题人把打乱的函数都用上图中类似的call rax 间接调用来实现。 此时我心态平和，我以为还剩三小时放出来的题必不会很难，于是想尝试修改上面那个基于angr的deflat脚本。我低估了其中的难度，对于angr本身也不熟悉的我根本改不来。所以最后尝试动调加手动patch binary。 但是只是尝试了一会我就发现这个做不到，因为量太大了。因此最后决定这题先放弃，跑去做别的了。
赛后当然还是想把这道题deflat出来， 于是在之前的基础上学习了angr的用法，折腾了几天，发现angr作为符号执行的工具对于这种去混淆的处理其实并不是很合适。 因为deflat部分的处理本质上是在模拟执行程序，并且记录真实的控制流，而这部分并不是angr所擅长的。那么谁更合适呢？ 当然是模拟执行的神器unicorn！
转头去尝试用unicorn完成deflat后，这题终于也走上了正轨。找了已有的unicorn deflat脚本，并在此基础上进行更改，写出了一个deflat脚本：
对于好几个关键函数进行去混淆以后，终于可以开始着手逆向了！
接下来就是逆向的问题了，先简单逆一下能知道，程序要求的输入是符号和数字，其中数字必须是0x[a-f][a-f][a-f][a-f] 符号只能是?!^| ，再加上题目说这是一个parser，我们可以猜到这是一个算式的解析。 那么肯定代码里会出现stack 这个stl 的数据结构， 而我对此并不是很熟悉。 果然我在动调的时候发现了sub_4151B0是一个parser功能的函数，其中它的第一个参数是这样的结构：
很有可能这就是栈的结构，我们都知道栈的默认底层container是deque， 因此去查了一下cpp里deque的实现：https://zhuanlan.zhihu.com/p/494261593 ， 通过这篇博客，我们可以写出deque的结构体。 当然还有vector也是逆向中很重要的数据结构：
在ida里加入这些结构体以后再逆向，整个逻辑就清楚了很多。 ?! 相当于是() ，只有^ 和 | 是运算符。 又根据明显的先序后序遍历能知道最后parser出来的是一个二叉树。 因此知道了输入的结构是 ?0x|0x!^?0x|0x!
我们把上面处理结果的四个未知量从左到右设为a，b，c， d， 最终的比对流程简化为：
sub_40F5B("hello123",d) ^ sub_40F5B("hello456",c) == cmp1
sub_411DE0("smithsmith666666", cmp1) ^ sub_411DE0("smithsmith777777", sub_40F5B(hello123,b) ^ sub_40F5B(hello456,a) ) == cmp2
通过对sbox的分析，以及密钥里smith的读音， 可以直接猜出sub_411DE0其实是sm4 加密，但是我没有看出sub_40F5B是什么加密。
由于a b c d 四个未知量，其中每个未知量都只有$6^4$种可能，而且由于sub_40F5B是ECB模式的块加密，每一个未知量又可以分为两个部分，可能性进一步退化到$6^2$。 因此可以采用爆破的方法。 虽然我们不知道sub_40F5B是什么加密，但是也可以用unicorn 来进行模拟执行。
最终的解密代码如下：
#coding=utf-8import collections
import angr
import am_graph
from util import *
# from keystone import *from unicorn import *
from unicorn.x86_const import *
from capstone import *
from capstone.x86 import *
obfus = [0x405DA0, 0x417610, 0x4149D0]
def reg_ctou(regname:str):
# This function covert capstone reg name to unicorn reg const.
# https://github.com/unicorn-engine/unicorn/blob/master/bindings/python/unicorn/x86_const.py
mp = { 'INVALID' : 0, 'AH' : 1, 'AL' : 2, 'AX' : 3, 'BH' : 4, 'BL' : 5, 'BP' : 6, 'BPL' : 7, 'BX' : 8, 'CH' : 9, 'CL' : 10, 'CS' : 11, 'CX' : 12, 'DH' : 13, 'DI' : 14, 'DIL' : 15, 'DL' : 16, 'DS' : 17, 'DX' : 18, 'EAX' : 19, 'EBP' : 20, 'EBX' : 21, 'ECX' : 22, 'EDI' : 23, 'EDX' : 24, 'EFLAGS' : 25, 'EIP' : 26, 'ES' : 28, 'ESI' : 29, 'ESP' : 30, 'FPSW' : 31, 'FS' : 32, 'GS' : 33, 'IP' : 34, 'RAX' : 35, 'RBP' : 36, 'RBX' : 37, 'RCX' : 38, 'RDI' : 39, 'RDX' : 40, 'RIP' : 41, 'RSI' : 43, 'RSP' : 44, 'SI' : 45, 'SIL' : 46, 'SP' : 47, 'SPL' : 48, 'SS' : 49, 'CR0' : 50, 'CR1' : 51, 'CR2' : 52, 'CR3' : 53, 'CR4' : 54, 'CR8' : 58, 'DR0' : 66, 'DR1' : 67, 'DR2' : 68, 'DR3' : 69, 'DR4' : 70, 'DR5' : 71, 'DR6' : 72, 'DR7' : 73, 'FP0' : 82, 'FP1' : 83, 'FP2' : 84, 'FP3' : 85, 'FP4' : 86, 'FP5' : 87, 'FP6' : 88, 'FP7' : 89, 'K0' : 90, 'K1' : 91, 'K2' : 92, 'K3' : 93, 'K4' : 94, 'K5' : 95, 'K6' : 96, 'K7' : 97, 'MM0' : 98, 'MM1' : 99, 'MM2' : 100, 'MM3' : 101, 'MM4' : 102, 'MM5' : 103, 'MM6' : 104, 'MM7' : 105, 'R8' : 106, 'R9' : 107, 'R10' : 108, 'R11' : 109, 'R12' : 110, 'R13' : 111, 'R14' : 112, 'R15' : 113, 'ST0' : 114, 'ST1' : 115, 'ST2' : 116, 'ST3' : 117, 'ST4' : 118, 'ST5' : 119, 'ST6' : 120, 'ST7' : 121, 'XMM0' : 122, 'XMM1' : 123, 'XMM2' : 124, 'XMM3' : 125, 'XMM4' : 126, 'XMM5' : 127, 'XMM6' : 128, 'XMM7' : 129, 'XMM8' : 130, 'XMM9' : 131, 'XMM10' : 132, 'XMM11' : 133, 'XMM12' : 134, 'XMM13' : 135, 'XMM14' : 136, 'XMM15' : 137, 'XMM16' : 138, 'XMM17' : 139, 'XMM18' : 140, 'XMM19' : 141, 'XMM20' : 142, 'XMM21' : 143, 'XMM22' : 144, 'XMM23' : 145, 'XMM24' : 146, 'XMM25' : 147, 'XMM26' : 148, 'XMM27' : 149, 'XMM28' : 150, 'XMM29' : 151, 'XMM30' : 152, 'XMM31' : 153, 'YMM0' : 154, 'YMM1' : 155, 'YMM2' : 156, 'YMM3' : 157, 'YMM4' : 158, 'YMM5' : 159, 'YMM6' : 160, 'YMM7' : 161, 'YMM8' : 162, 'YMM9' : 163, 'YMM10' : 164, 'YMM11' : 165, 'YMM12' : 166, 'YMM13' : 167, 'YMM14' : 168, 'YMM15' : 169, 'YMM16' : 170, 'YMM17' : 171, 'YMM18' : 172, 'YMM19' : 173, 'YMM20' : 174, 'YMM21' : 175, 'YMM22' : 176, 'YMM23' : 177, 'YMM24' : 178, 'YMM25' : 179, 'YMM26' : 180, 'YMM27' : 181, 'YMM28' : 182, 'YMM29' : 183, 'YMM30' : 184, 'YMM31' : 185, 'ZMM0' : 186, 'ZMM1' : 187, 'ZMM2' : 188, 'ZMM3' : 189, 'ZMM4' : 190, 'ZMM5' : 191, 'ZMM6' : 192, 'ZMM7' : 193, 'ZMM8' : 194, 'ZMM9' : 195, 'ZMM10' : 196, 'ZMM11' : 197, 'ZMM12' : 198, 'ZMM13' : 199, 'ZMM14' : 200, 'ZMM15' : 201, 'ZMM16' : 202, 'ZMM17' : 203, 'ZMM18' : 204, 'ZMM19' : 205, 'ZMM20' : 206, 'ZMM21' : 207, 'ZMM22' : 208, 'ZMM23' : 209, 'ZMM24' : 210, 'ZMM25' : 211, 'ZMM26' : 212, 'ZMM27' : 213, 'ZMM28' : 214, 'ZMM29' : 215, 'ZMM30' : 216, 'ZMM31' : 217, 'R8B' : 218, 'R9B' : 219, 'R10B' : 220, 'R11B' : 221, 'R12B' : 222, 'R13B' : 223, 'R14B' : 224, 'R15B' : 225, 'R8D' : 226, 'R9D' : 227, 'R10D' : 228, 'R11D' : 229, 'R12D' : 230, 'R13D' : 231, 'R14D' : 232, 'R15D' : 233, 'R8W' : 234, 'R9W' : 235, 'R10W' : 236, 'R11W' : 237, 'R12W' : 238, 'R13W' : 239, 'R14W' : 240, 'R15W' : 241, 'IDTR' : 242, 'GDTR' : 243, 'LDTR' : 244, 'TR' : 245, 'FPCW' : 246, 'FPTAG' : 247, 'MSR' : 248, 'MXCSR' : 249, 'FS_BASE' : 250, 'GS_BASE' : 251, 'FLAGS' : 252, 'RFLAGS' : 253, 'FIP' : 254, 'FCS' : 255, 'FDP' : 256, 'FDS' : 257, 'FOP' : 258, 'ENDING' : 259, }
regname = regname.upper()
return mp[regname]
def get_context(): # record all X86/64 regs
global mu
return mu.context_save()
def set_context(context:bytes):
global mu
if context == None :
return
else:
mu.context_restore(context)
return
# callback for memory exceptiondef hook_mem_access(uc,type,address,size,value,userdata):
pc = uc.reg_read(UC_X86_REG_RIP)
print ('pc:%x type:%d addr:%x size:%x' % (pc,type,address,size))
def hook_code(uc, address, size, user_data):
global base
global is_success
global list_trace
global relevants
global next_real_block_addr
global block_start_addr
global branch_control
global instrs_size
global memset_count
global nop_instruc
instrs_size = size
if is_success:
uc.emu_stop()
return
# if address > end:
# uc.emu_stop()
# return
for ins in md.disasm(bin[address-base:address -base + size], address-base):
#print(">>> Tracing instruction at 0x%x, instruction size = 0x%x" % (address, size))
#print(">>> 0x%x:\t%s\t%s" % (ins.address, ins.mnemonic, ins.op_str))
# bfs 的visit array 防止陷入循环
if address in relevants:
if address in list_trace:
print("sssssss")
uc.emu_stop()
else:
list_trace[address] = 1
# 找到了下一个块
if address in relevants and address != block_start_addr:
is_success = True
next_real_block_addr = address
#print 'find:%x' % address
uc.emu_stop()
return
#是否跳过指令
flag_pass = False
if ins.mnemonic.startswith("call") :
if(ins.op_str == '0x2090' and memset_count < 2): # hook memset twice
memset_count += 1
ptr = uc.reg_read(UC_X86_REG_RDI)
val = uc.reg_read(UC_X86_REG_ESI).to_bytes(1,'little')
siz = uc.reg_read(UC_X86_REG_EDX)
uc.mem_write(ptr,val*siz)
flag_pass = True
elif(ins.op_str not in ('rax','rbx','rcx','rdx','rsi','rdi','r8','r9','r10','r11','r12','r13','r14','r15') ):
flag_pass = True
elif(ins.op_str in ('rax','rbx','rcx','rdx','rsi','rdi','r8','r9','r10','r11','r12','r13','r14','r15')):
func = uc.reg_read(reg_ctou(ins.op_str))
if func in obfus:
nop_instruc.add((address,size))
else:
flag_pass = True
# 用于跳过指令
if flag_pass:
uc.reg_write(UC_X86_REG_RIP, address + size)
return # 结束块单独处理
if ins.id == X86_INS_RET :
if relevants[block_start_addr] in retn_nodes:
# uc.reg_write(UC_X86_REG_RIP, 0) # 必须注释掉 https://github.com/unicorn-engine/unicorn/issues/1133
is_success = False
print ("ret ins in {}".format(hex(address)))
uc.emu_stop()
return
else: # in obfus function
pass
#ollvm branch
if ins.mnemonic.startswith('cmov'):
#print("csel 0x%x:\t%s\t%s" %(ins.address, ins.mnemonic, ins.op_str))
regs = [reg_ctou(x) for x in ins.op_str.split(', ')]
assert len(regs) == 2
v1 = uc.reg_read(regs[0])
v2 = uc.reg_read(regs[1])
if branch_control == 1:
uc.reg_write(regs[0], v1)
else:
uc.reg_write(regs[0], v2)
uc.reg_write(UC_X86_REG_RIP, address + size)
def find_path(start_addr,branch = None, from_error = False):
global bin
global base
global mu
global list_trace
global block_start_addr
global next_real_block_addr
global is_success
global branch_control
try:
list_trace = {}
if from_error == False:
block_start_addr = start_addr
is_success = False
next_real_block_addr = 0
branch_control = branch
mu.emu_start(start_addr, start_addr+0x10000) # unitl 参数不重要 因为hookcode会断住
except UcError as e:
pc = mu.reg_read(UC_X86_REG_RIP)
if pc != 0:
# 模拟执行碰到和恢复控制流无关的问题，就略过该指令继续运行
# 是一个递归，block不大的情况下应该不会递归爆炸
print(" pc:%x block_start_addr:%x" % (pc,block_start_addr))
return find_path(pc + instrs_size, branch, from_error=True)
else:
print("ERROR: %s pc:%x block_start_addr:%x" % (e,pc,block_start_addr))
if is_success:
return next_real_block_addr
return None
def fix(bin:bytearray,flow:dict,nop_nodes:list, patch_instrs :dict):
ori_len = len(bin)
# patch irrelevant blocks
for nop_node in nop_nodes:
fill_nop(bin, nop_node.addr-base,
nop_node.size, project.arch)
for a in nop_instruc:
fill_nop(bin, a[0]-base, a[1], project.arch)
# remove unnecessary control flows
for parent, childs in flow.items():
parent = relevants[parent]
if len(childs) == 1:
parent_block = project.factory.block(parent.addr, size=parent.size)
last_instr = parent_block.capstone.insns[-1]
file_offset = last_instr.address - base
# patch the last instruction to jmp
if(parent.addr + parent.size == childs[0] and last_instr.op_str != hex(the_last_jmp_block)): # 下一个块就是要去的块就不用patch
continue
if project.arch.name in ARCH_X86:
fill_nop(bin, file_offset, last_instr.size, project.arch)
patch_value = ins_j_jmp_hex_x86(last_instr.address, childs[0], 'jmp')
patch_instruction(bin, file_offset, patch_value)
else:
instr = patch_instrs[parent]
file_offset = instr.address - base
# patch instructions starting from `cmovx` to the end of block
fill_nop(bin, file_offset, parent.addr +
parent.size - base - file_offset, project.arch)
if project.arch.name in ARCH_X86:
# patch the cmovx instruction to jx instruction
patch_value = ins_j_jmp_hex_x86(instr.address, childs[0], instr.mnemonic[len('cmov'):])
patch_instruction(bin, file_offset, patch_value)
file_offset += 6
# patch the next instruction to jmp instrcution
patch_value = ins_j_jmp_hex_x86(instr.address+6, childs[1], 'jmp')
patch_instruction(bin, file_offset, patch_value)
assert(ori_len == len(bin))
return bin
if __name__ == "__main__":
md = Cs(CS_ARCH_X86,CS_MODE_64)
md.detail = True
filename = "babyparser_recover_main"
new_filename = filename
with open(filename, 'rb') as fp:
bin = fp.read()
project = angr.Project(filename, load_options={'auto_load_libs': False})
base = project.loader.main_object.mapped_base >> 12 << 12 start = 0x40fe20
the_last_jmp_block = 0x411448
#cfg = project.analyses.CFGFast(normalize=True)
cfg = project.analyses.CFGFast(normalize=True,force_complete_scan=False)
target_function = cfg.functions.get(start)
assert target_function != None
# end = start + target_function.size
supergraph = am_graph.to_supergraph(target_function.transition_graph)
# *******************GET BLOCK***************************
# get prologue_node(开始结点) and retn_node
prologue_nodes = []
retn_nodes = []
relevant_nodes = []
nop_nodes = []
patch_instrs = {}
for node in supergraph.nodes():
if supergraph.in_degree(node) == 0:
prologue_nodes.append(node)
elif supergraph.out_degree(node) == 0 :
retn_nodes.append(node)
elif supergraph.out_degree(node) == 1 and node.addr != the_last_jmp_block:
relevant_nodes.append(node)
elif supergraph.out_degree(node) == 2 :
nop_nodes.append(node)
print(prologue_nodes)
print(retn_nodes)
if len(prologue_nodes) != 1 or prologue_nodes[0].addr != start:
print("Something must be wrong...")
exit(0)
main_dispatcher_node = list(supergraph.successors(prologue_nodes[0]))[0]
relevant_block_addrs = [(node.addr) for node in relevant_nodes]
relevants = {}
for node in relevant_nodes+prologue_nodes+retn_nodes:
relevants[node.addr] = node
print('*******************relevant blocks************************')
print('prologue: %#x' % start)
print('main_dispatcher: %#x' % main_dispatcher_node.addr)
print('retn: ' , [hex(node.addr) for node in retn_nodes])
print('relevant_blocks:', [hex(addr) for addr in relevant_block_addrs])
print('*******************simulated execution*********************')
flow = collections.defaultdict(list)
instrs_size = 0
memset_count = 0
nop_instruc = set()
mu = Uc(UC_ARCH_X86, UC_MODE_64)
#init stack
mu.mem_map(0x80000000,0x10000 * 8)
# map 4MB memory for this emulation
mu.mem_map(base, 16 * 1024 * 1024)
# write machine code to be emulated to memory
mu.mem_write(0x401000, bin[0x2000:0x2000+0x19559]) # code segment
mu.mem_write(0x420dd0,bin[0x20dd0:0x20dd0+0x6270]) # data segment
mu.reg_write(UC_X86_REG_RSP, 0x80000000 + 0x10000 * 6)
mu.hook_add(UC_HOOK_CODE, hook_code) # 对每条指令hook
mu.hook_add(UC_HOOK_MEM_UNMAPPED, hook_mem_access)
#set function argv
mu.reg_write(UC_X86_REG_RDI, 1) # set argc
list_trace = {}
is_debug = False
queue = [(start, None)]
while len(queue) != 0:
env = queue.pop()
address = env[0]
context = env[1]
if address in flow:
continue
set_context(context)
node = relevants[address]
block = project.factory.block(address, size=node.size) # 当前处理的块
has_branches = False
hook_addr = []
#检测代码块中是否有ollvm生成的分支
for ins in block.capstone.insns:
if ins.insn.mnemonic.startswith('cmov'):
has_branches = True
if node not in patch_instrs:
patch_instrs[node] = ins
break
#代码块中有ollvm生成的分支
if has_branches:
ctx = get_context()
p1 = find_path(address, 0)
if p1 != None:
queue.append((p1, get_context()))
flow[address].append(p1)
set_context(ctx)
p2 = find_path(address, 1)
if p1 == p2:
p2 = None
if p2 != None:
queue.append((p2, get_context()))
flow[address].append(p2)
else:
p = find_path(address)
if p != None:
queue.append((p, get_context()))
flow[address].append(p)
# print(flow)
print('************************flow******************************')
for k, v in flow.items():
print('%#x: ' % k, [hex(child) for child in v])
print('************************fix******************************')
new_bin = fix(bytearray(bin), flow, nop_nodes, patch_instrs)
with open(new_filename,"wb") as fp:
fp.write(new_bin)
#coding=utf-8import collections
import angr
import am_graph
from util import *
# from keystone import *from unicorn import *
from unicorn.x86_const import *
from capstone import *
from capstone.x86 import *
obfus = [0x405DA0, 0x417610, 0x4149D0]
def reg_ctou(regname:str):
# This function covert capstone reg name to unicorn reg const.
# https://github.com/unicorn-engine/unicorn/blob/master/bindings/python/unicorn/x86_const.py
mp = { 'INVALID' : 0, 'AH' : 1, 'AL' : 2, 'AX' : 3, 'BH' : 4, 'BL' : 5, 'BP' : 6, 'BPL' : 7, 'BX' : 8, 'CH' : 9, 'CL' : 10, 'CS' : 11, 'CX' : 12, 'DH' : 13, 'DI' : 14, 'DIL' : 15, 'DL' : 16, 'DS' : 17, 'DX' : 18, 'EAX' : 19, 'EBP' : 20, 'EBX' : 21, 'ECX' : 22, 'EDI' : 23, 'EDX' : 24, 'EFLAGS' : 25, 'EIP' : 26, 'ES' : 28, 'ESI' : 29, 'ESP' : 30, 'FPSW' : 31, 'FS' : 32, 'GS' : 33, 'IP' : 34, 'RAX' : 35, 'RBP' : 36, 'RBX' : 37, 'RCX' : 38, 'RDI' : 39, 'RDX' : 40, 'RIP' : 41, 'RSI' : 43, 'RSP' : 44, 'SI' : 45, 'SIL' : 46, 'SP' : 47, 'SPL' : 48, 'SS' : 49, 'CR0' : 50, 'CR1' : 51, 'CR2' : 52, 'CR3' : 53, 'CR4' : 54, 'CR8' : 58, 'DR0' : 66, 'DR1' : 67, 'DR2' : 68, 'DR3' : 69, 'DR4' : 70, 'DR5' : 71, 'DR6' : 72, 'DR7' : 73, 'FP0' : 82, 'FP1' : 83, 'FP2' : 84, 'FP3' : 85, 'FP4' : 86, 'FP5' : 87, 'FP6' : 88, 'FP7' : 89, 'K0' : 90, 'K1' : 91, 'K2' : 92, 'K3' : 93, 'K4' : 94, 'K5' : 95, 'K6' : 96, 'K7' : 97, 'MM0' : 98, 'MM1' : 99, 'MM2' : 100, 'MM3' : 101, 'MM4' : 102, 'MM5' : 103, 'MM6' : 104, 'MM7' : 105, 'R8' : 106, 'R9' : 107, 'R10' : 108, 'R11' : 109, 'R12' : 110, 'R13' : 111, 'R14' : 112, 'R15' : 113, 'ST0' : 114, 'ST1' : 115, 'ST2' : 116, 'ST3' : 117, 'ST4' : 118, 'ST5' : 119, 'ST6' : 120, 'ST7' : 121, 'XMM0' : 122, 'XMM1' : 123, 'XMM2' : 124, 'XMM3' : 125, 'XMM4' : 126, 'XMM5' : 127, 'XMM6' : 128, 'XMM7' : 129, 'XMM8' : 130, 'XMM9' : 131, 'XMM10' : 132, 'XMM11' : 133, 'XMM12' : 134, 'XMM13' : 135, 'XMM14' : 136, 'XMM15' : 137, 'XMM16' : 138, 'XMM17' : 139, 'XMM18' : 140, 'XMM19' : 141, 'XMM20' : 142, 'XMM21' : 143, 'XMM22' : 144, 'XMM23' : 145, 'XMM24' : 146, 'XMM25' : 147, 'XMM26' : 148, 'XMM27' : 149, 'XMM28' : 150, 'XMM29' : 151, 'XMM30' : 152, 'XMM31' : 153, 'YMM0' : 154, 'YMM1' : 155, 'YMM2' : 156, 'YMM3' : 157, 'YMM4' : 158, 'YMM5' : 159, 'YMM6' : 160, 'YMM7' : 161, 'YMM8' : 162, 'YMM9' : 163, 'YMM10' : 164, 'YMM11' : 165, 'YMM12' : 166, 'YMM13' : 167, 'YMM14' : 168, 'YMM15' : 169, 'YMM16' : 170, 'YMM17' : 171, 'YMM18' : 172, 'YMM19' : 173, 'YMM20' : 174, 'YMM21' : 175, 'YMM22' : 176, 'YMM23' : 177, 'YMM24' : 178, 'YMM25' : 179, 'YMM26' : 180, 'YMM27' : 181, 'YMM28' : 182, 'YMM29' : 183, 'YMM30' : 184, 'YMM31' : 185, 'ZMM0' : 186, 'ZMM1' : 187, 'ZMM2' : 188, 'ZMM3' : 189, 'ZMM4' : 190, 'ZMM5' : 191, 'ZMM6' : 192, 'ZMM7' : 193, 'ZMM8' : 194, 'ZMM9' : 195, 'ZMM10' : 196, 'ZMM11' : 197, 'ZMM12' : 198, 'ZMM13' : 199, 'ZMM14' : 200, 'ZMM15' : 201, 'ZMM16' : 202, 'ZMM17' : 203, 'ZMM18' : 204, 'ZMM19' : 205, 'ZMM20' : 206, 'ZMM21' : 207, 'ZMM22' : 208, 'ZMM23' : 209, 'ZMM24' : 210, 'ZMM25' : 211, 'ZMM26' : 212, 'ZMM27' : 213, 'ZMM28' : 214, 'ZMM29' : 215, 'ZMM30' : 216, 'ZMM31' : 217, 'R8B' : 218, 'R9B' : 219, 'R10B' : 220, 'R11B' : 221, 'R12B' : 222, 'R13B' : 223, 'R14B' : 224, 'R15B' : 225, 'R8D' : 226, 'R9D' : 227, 'R10D' : 228, 'R11D' : 229, 'R12D' : 230, 'R13D' : 231, 'R14D' : 232, 'R15D' : 233, 'R8W' : 234, 'R9W' : 235, 'R10W' : 236, 'R11W' : 237, 'R12W' : 238, 'R13W' : 239, 'R14W' : 240, 'R15W' : 241, 'IDTR' : 242, 'GDTR' : 243, 'LDTR' : 244, 'TR' : 245, 'FPCW' : 246, 'FPTAG' : 247, 'MSR' : 248, 'MXCSR' : 249, 'FS_BASE' : 250, 'GS_BASE' : 251, 'FLAGS' : 252, 'RFLAGS' : 253, 'FIP' : 254, 'FCS' : 255, 'FDP' : 256, 'FDS' : 257, 'FOP' : 258, 'ENDING' : 259, }
regname = regname.upper()
return mp[regname]
def get_context(): # record all X86/64 regs
global mu
return mu.context_save()
def set_context(context:bytes):
global mu
if context == None :
return
else:
mu.context_restore(context)
return
# callback for memory exceptiondef hook_mem_access(uc,type,address,size,value,userdata):
pc = uc.reg_read(UC_X86_REG_RIP)
print ('pc:%x type:%d addr:%x size:%x' % (pc,type,address,size))
def hook_code(uc, address, size, user_data):
global base
global is_success
global list_trace
global relevants
global next_real_block_addr
global block_start_addr
global branch_control
global instrs_size
global memset_count
global nop_instruc
instrs_size = size
if is_success:
uc.emu_stop()
return
# if address > end:
# uc.emu_stop()
# return
for ins in md.disasm(bin[address-base:address -base + size], address-base):
#print(">>> Tracing instruction at 0x%x, instruction size = 0x%x" % (address, size))
#print(">>> 0x%x:\t%s\t%s" % (ins.address, ins.mnemonic, ins.op_str))
# bfs 的visit array 防止陷入循环
if address in relevants:
if address in list_trace:
print("sssssss")
uc.emu_stop()
else:
list_trace[address] = 1
# 找到了下一个块
if address in relevants and address != block_start_addr:
is_success = True
next_real_block_addr = address
#print 'find:%x' % address
uc.emu_stop()
return
#是否跳过指令
flag_pass = False
if ins.mnemonic.startswith("call") :
if(ins.op_str == '0x2090' and memset_count < 2): # hook memset twice
memset_count += 1
ptr = uc.reg_read(UC_X86_REG_RDI)
val = uc.reg_read(UC_X86_REG_ESI).to_bytes(1,'little')
siz = uc.reg_read(UC_X86_REG_EDX)
uc.mem_write(ptr,val*siz)
flag_pass = True
elif(ins.op_str not in ('rax','rbx','rcx','rdx','rsi','rdi','r8','r9','r10','r11','r12','r13','r14','r15') ):
flag_pass = True
elif(ins.op_str in ('rax','rbx','rcx','rdx','rsi','rdi','r8','r9','r10','r11','r12','r13','r14','r15')):
func = uc.reg_read(reg_ctou(ins.op_str))
if func in obfus:
nop_instruc.add((address,size))
else:
flag_pass = True
# 用于跳过指令
if flag_pass:
uc.reg_write(UC_X86_REG_RIP, address + size)
return # 结束块单独处理
if ins.id == X86_INS_RET :
if relevants[block_start_addr] in retn_nodes:
# uc.reg_write(UC_X86_REG_RIP, 0) # 必须注释掉 https://github.com/unicorn-engine/unicorn/issues/1133
is_success = False
print ("ret ins in {}".format(hex(address)))
uc.emu_stop()
return
else: # in obfus function
pass
#ollvm branch
if ins.mnemonic.startswith('cmov'):
#print("csel 0x%x:\t%s\t%s" %(ins.address, ins.mnemonic, ins.op_str))
regs = [reg_ctou(x) for x in ins.op_str.split(', ')]
assert len(regs) == 2
v1 = uc.reg_read(regs[0])
v2 = uc.reg_read(regs[1])
if branch_control == 1:
uc.reg_write(regs[0], v1)
else:
uc.reg_write(regs[0], v2)
uc.reg_write(UC_X86_REG_RIP, address + size)
def find_path(start_addr,branch = None, from_error = False):
global bin
global base
global mu
global list_trace
global block_start_addr
global next_real_block_addr
global is_success
global branch_control
try:
list_trace = {}
if from_error == False:
block_start_addr = start_addr
is_success = False
next_real_block_addr = 0
branch_control = branch
mu.emu_start(start_addr, start_addr+0x10000) # unitl 参数不重要 因为hookcode会断住
except UcError as e:
pc = mu.reg_read(UC_X86_REG_RIP)
if pc != 0:
# 模拟执行碰到和恢复控制流无关的问题，就略过该指令继续运行
# 是一个递归，block不大的情况下应该不会递归爆炸
print(" pc:%x block_start_addr:%x" % (pc,block_start_addr))
return find_path(pc + instrs_size, branch, from_error=True)
else:
print("ERROR: %s pc:%x block_start_addr:%x" % (e,pc,block_start_addr))
if is_success:
return next_real_block_addr
return None
def fix(bin:bytearray,flow:dict,nop_nodes:list, patch_instrs :dict):
ori_len = len(bin)
# patch irrelevant blocks
for nop_node in nop_nodes:
fill_nop(bin, nop_node.addr-base,
nop_node.size, project.arch)
for a in nop_instruc:
fill_nop(bin, a[0]-base, a[1], project.arch)
# remove unnecessary control flows
for parent, childs in flow.items():
parent = relevants[parent]
if len(childs) == 1:
parent_block = project.factory.block(parent.addr, size=parent.size)
last_instr = parent_block.capstone.insns[-1]
file_offset = last_instr.address - base
# patch the last instruction to jmp
if(parent.addr + parent.size == childs[0] and last_instr.op_str != hex(the_last_jmp_block)): # 下一个块就是要去的块就不用patch
continue
if project.arch.name in ARCH_X86:
fill_nop(bin, file_offset, last_instr.size, project.arch)
patch_value = ins_j_jmp_hex_x86(last_instr.address, childs[0], 'jmp')
patch_instruction(bin, file_offset, patch_value)
else:
instr = patch_instrs[parent]
file_offset = instr.address - base
# patch instructions starting from `cmovx` to the end of block
fill_nop(bin, file_offset, parent.addr +
parent.size - base - file_offset, project.arch)
if project.arch.name in ARCH_X86:
# patch the cmovx instruction to jx instruction
patch_value = ins_j_jmp_hex_x86(instr.address, childs[0], instr.mnemonic[len('cmov'):])
patch_instruction(bin, file_offset, patch_value)
file_offset += 6
# patch the next instruction to jmp instrcution
patch_value = ins_j_jmp_hex_x86(instr.address+6, childs[1], 'jmp')
patch_instruction(bin, file_offset, patch_value)
assert(ori_len == len(bin))
return bin
if __name__ == "__main__":
md = Cs(CS_ARCH_X86,CS_MODE_64)
md.detail = True
filename = "babyparser_recover_main"
new_filename = filename
with open(filename, 'rb') as fp:
bin = fp.read()
project = angr.Project(filename, load_options={'auto_load_libs': False})
base = project.loader.main_object.mapped_base >> 12 << 12 start = 0x40fe20
the_last_jmp_block = 0x411448
#cfg = project.analyses.CFGFast(normalize=True)
cfg = project.analyses.CFGFast(normalize=True,force_complete_scan=False)
target_function = cfg.functions.get(start)
assert target_function != None
# end = start + target_function.size
supergraph = am_graph.to_supergraph(target_function.transition_graph)
[招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
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这个脚本，是神仙的味道
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并不算是。 本质是一个对CFG进行BFS遍历执行所有真实块的过程，所以模拟部分是对每一个真实块找到它下一个（或两个）真实块结束
最后于 2022-12-9 14:30
被1mmortal编辑
，原因：
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哦哦 我明白了 这个是保证了基本块执行上下文的bfs 如果是使用类似deflat的思路从单独的基本块出发模拟执行确定后继应该是不行的
最后于 2022-12-9 20:43
被R1mao编辑
，原因：
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对的 所以遍历是从先序结点开始的 符合程序运行顺序 |
