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[原创] Blue Water CTF 2024 re OORM wp 模拟执行爆破+剪枝
发表于: 2024-10-14 16:03 5494

[原创] Blue Water CTF 2024 re OORM wp 模拟执行爆破+剪枝

2024-10-14 16:03
5494

肝了一下午,拿了个一血,开心hh
如果patch或者插桩之类的方法,代替模拟执行的话,可能速度会更快,不过这题规模还能接受,就用模拟执行跑了,这个方便一点,切个片段出来就能直接执行
需要注意的是避免用unicorn的单步,指定until会快很多;然后unicorn不知道为什么emu_start多次后会报一个OS Error什么访问-1指针异常啥的,得隔一定次数重新new一个Uc

main:

输入100个hex

然后每一个hex,转int,接着按位拆分,存进QWORD[400]数组unk_214EE0,unk_214260中,低位在数组低地址

接着轮询800个函数,总共需要执行800次

最后需要dword_212940 == 40

那800个函数的定义:void (__fastcall *)(__int64 key, __int64 input_bit)

keyAs_2135E0、keyBs_212960初始化地方sub_6160,好像是什么PHT里引用了这个函数

keyAs、keyBs分别初始了20个非0元素,dump出这两个数组

funcs_A[0](key, input_bit)大致逻辑,根据keyAs[0]和input_bit[0],给keyAs[20]赋值:

funcs_A[1](key, input_bit)大致逻辑,根据keyAs[1]和input_bit[1],给keyAs[21]赋值:

funcs_A[399](key, input_bit)大致逻辑,根据keyAs[399]和input_bit[399],给dwCheck_212940赋值:

fA_0~fA_19 生成 fA_20~fA_39 的key

然后fA_20~fA_39 生成 fA_40~fA59 的key

直到fA_380~fA_399 是检验

整体大概是这么个顺序:

fA_0 ⇒ fA_20 … fA_360,fA_380校验

fA_1 ⇒ fA_21 … fA_361,fA_381校验

fB_0 ⇒ fB_1 … fB_18,fB_19校验

fB_20 ⇒ fB_21 … fB_38,fB_39校验

相当于输入是20*20的值只能为0、1的矩阵

fA系列函数是做列校验

fB系列函数是做行校验

使用fA_0、fA_20、...、fA_380爆破第一列,有很多结果:

模拟执行fA爆破列的脚本(使用fB爆破行的脚本也差不多):

爆破列校验发现有多解,检查列的所有解,如果某一位在该列的所有解中全为0或1可以确认该位为0或1,一次列验证确认结果如下:

然后用这个确认的结果,对爆破做剪枝加速,继续跑一次行验证、一次列验证、一次行验证(每次跑完验证都按前面的思路更新这个确认的结果),就出来完整结果了

times = 0;
  do
  {
    for ( i = 0LL; i != 400; ++i )
    {
      keyA = keyAs_2135E0[i];
      if ( runA )
      {
        ++times;
        funcs_A_211CA0[i](keyA, input_in_bits_A_214EE0[i]);
        keyAs_2135E0[i] = 0LL;
      }
      keyB = keyBs_212960[i];
      if ( keyB )
      {
        ++times;
        funcs_B_211020[i](keyB, input_in_bits_B_214260[i]);
        keyBs_212960[i] = 0LL;
      }
    }
  }
  while ( times <= 799 );
times = 0;
  do
  {
    for ( i = 0LL; i != 400; ++i )
    {
      keyA = keyAs_2135E0[i];
      if ( runA )
      {
        ++times;
        funcs_A_211CA0[i](keyA, input_in_bits_A_214EE0[i]);
        keyAs_2135E0[i] = 0LL;
      }
      keyB = keyBs_212960[i];
      if ( keyB )
      {
        ++times;
        funcs_B_211020[i](keyB, input_in_bits_B_214260[i]);
        keyBs_212960[i] = 0LL;
      }
    }
  }
  while ( times <= 799 );
void funcs_A_0(__int64 key, __int64 input_bit) {
    x = input_bit | (key<< 1);
    y = hashA0(x);
    // 48 89 3D B7 C5                 mov     cs:keyAs_2135E0+0A0h, rdi
    keyAs[20] = y;
}
void funcs_A_0(__int64 key, __int64 input_bit) {
    x = input_bit | (key<< 1);
    y = hashA0(x);
    // 48 89 3D B7 C5                 mov     cs:keyAs_2135E0+0A0h, rdi
    keyAs[20] = y;
}
void funcs_A_1(__int64 key, __int64 input_bit) {
    x = input_bit | (key<< 1);
    y = hashA1(x);
    // 48 89 3D FF BA                 mov     cs:keyAs_2135E0+0A8h, rdi
    keyAs[21] = y;
}
void funcs_A_1(__int64 key, __int64 input_bit) {
    x = input_bit | (key<< 1);
    y = hashA1(x);
    // 48 89 3D FF BA                 mov     cs:keyAs_2135E0+0A8h, rdi
    keyAs[21] = y;
}
void funcs_A_399(__int64 key, __int64 input_bit) {
    x = input_bit | (key<< 1);
    y = hashA399(x);
    if ( y == 21961 || y == 27098 )
        ++dwCheck_212940;
}
void funcs_A_399(__int64 key, __int64 input_bit) {
    x = input_bit | (key<< 1);
    y = hashA399(x);
    if ( y == 21961 || y == 27098 )
        ++dwCheck_212940;
}
[0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0] 3090
...
[1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 1] 32766
[1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 0] 3090
[1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0] 3090
...
[0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1] 32766
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0] 3090
...
[1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 1] 32766
[1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 0] 3090
[1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0] 3090
...
from capstone import *
from unicorn import *
from unicorn.x86_const import *
from elftools.elf.elffile import ELFFile
 
keyAs = [9644, 31494, 15772, ..., 0, 0, 0, ...]
 
f = open('main', 'rb')
elff = ELFFile(f)
 
def rva_to_offset(elff, rva):
    for segment in elff.iter_sections():
        if rva >= segment['p_vaddr'] and rva < segment['p_vaddr'] + segment['p_memsz']:
            return rva - segment['p_vaddr'] + segment['p_offset']
    raise ValueError('RVA not within any segment')
  
def read_elf_content_by_rva(elff, rva, size):
    for segment in elff.iter_segments():
        # 检查RVA是否在当前段的范围内
        if rva >= segment['p_vaddr'] and rva < segment['p_vaddr'] + segment['p_memsz']:
            foa = rva - segment['p_vaddr']
            content = segment.data()[foa : foa + size]
            return content
 
# 收集函数的地址
 
funcs_A = [int.from_bytes(read_elf_content_by_rva(elff, 0x211CA0 + i * 8, 8), 'little') for i in range(400)]
 
funcs_A.append(0x106430)
 
endAs = [ 28866, 31618, 34242, ...]
tyAs = [ 39, 39, 39, ..., (35, 32766, 3090), (35, 6485, 4159), (35, 14535, 24449), ...]
 
def sim2(uc: Uc, i, j, key, input_bit):
    # func arg
    idx = i + j * 20
    uc.reg_write(UC_X86_REG_RDI, key)
    uc.reg_write(UC_X86_REG_RSI, input_bit)
    uc.emu_start(funcs_A[idx], endAs[idx], 0, 0)
    if j != 19:
        return uc.reg_read(tyAs[idx]), 0, 0
    else:
        return uc.reg_read(tyAs[idx][0]), tyAs[idx][1], tyAs[idx][2]
 
uc = Uc(UC_ARCH_X86, UC_MODE_64)
 
# code
for segment in elff.iter_segments():
    if segment['p_vaddr'] == 0x6000:
        uc.mem_map(segment['p_vaddr'], segment['p_memsz']//0x1000*0x1000 + 0x1000)
        uc.mem_write(segment['p_vaddr'], segment.data())
 
# 执行funcA[i + j * 20](key, 0) 和 funcA[i + j * 20](key, 1)
def dfsA(i, j, key) -> bool:
    global path, uc
 
    if j == 3: # unicron的bug,得隔一定次数重新创建一个Uc
        uc = Uc(UC_ARCH_X86, UC_MODE_64)
        for segment in elff.iter_segments():
            if segment['p_vaddr'] == 0x6000:
                uc.mem_map(segment['p_vaddr'], segment['p_memsz']//0x1000*0x1000 + 0x1000)
                uc.mem_write(segment['p_vaddr'], segment.data())
 
    if j == 6:
        print(path)
 
    if j == 19:
        new_key, t0, t1 = sim2(uc, i, j, key, 0)
        if new_key == t0 or new_key == t1:
            print('path', path + [0], new_key)
             
        new_key, t0, t1 = sim2(uc, i, j, key, 1)
        if new_key == t0 or new_key == t1:
            print('path', path + [1], new_key)
    else:
        new_key, _, _ = sim2(uc, i, j, key, 0)
        path.append(0)
        dfsA(i, j + 1, new_key)
        path.pop()
         
        new_key, _, _ = sim2(uc, i, j, key, 1)
        path.append(1)
        dfsA(i, j + 1, new_key)
        path.pop()
 
path = []
dfsA(0, 0, keyAs[0])
 
f.close()
from capstone import *
from unicorn import *
from unicorn.x86_const import *
from elftools.elf.elffile import ELFFile
 
keyAs = [9644, 31494, 15772, ..., 0, 0, 0, ...]
 
f = open('main', 'rb')
elff = ELFFile(f)
 
def rva_to_offset(elff, rva):
    for segment in elff.iter_sections():
        if rva >= segment['p_vaddr'] and rva < segment['p_vaddr'] + segment['p_memsz']:
            return rva - segment['p_vaddr'] + segment['p_offset']
    raise ValueError('RVA not within any segment')

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最后于 2024-10-14 16:15 被wx_御史神风编辑 ,原因:
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