D^3CTF2024逆向Writeup
作者论坛账号：zipkey
写在前面
第一次在52发帖，写的有问题的地方还请师傅们见谅
逆向部分题目很不错，VM题的伪随机控制流和迷宫题异常处理设置很巧妙，还剩两道没力气逆了，以后再补
ezjunk
花指令，直接NOP掉，反编译main函数
加密部分是xxtea，观察调用时传入的参数，a2是sum，来自loc_4015C3+2，a3是delta，来自loc_401A1C，a4是key,来自off_404350 + 400
delta在main里面，刚好是patch掉的部分，需要记录patch前的数据，sum在另一个函数里面，先去掉花指令
找到sum所在的地方，这部分在main运行前执行，LoadLibraryA没用，可以忽略，IsDebuggerPresent检测调试器，根据是否被调试设置key，patch掉反调试，记录patch前的sum值
写xxtea解密
复制代码 隐藏代码#!/usr/bin/env python flag = [0x5406CBB1, 0xA4A41EA2, 0x34489AC5, 0x53D68797, 0xB8E0C06F, 0x259F2DB, 0x52E38D82, 0x595D5E1D] k2 = 0xE8017300 k3 = 0xFF58F981 key = [0x5454, 0x4602, 0x4477, 0x5E5E, 0x33, 0x43, 0x54, 0x46] for i in range(0, 7, 2): v6 = flag[i+1] v7 = flag[i] a2 = k2 for _ in range(32) a2 = a2 + 0x100000000 - k3 a2 &= 0xFFFFFFFF for _ in range(32): a2 += k3 a2 &= 0xFFFFFFFF v6 = v6 + 0x100000000 - (((v7 + ((v7 << 5) ^ (v7 >> 6))) ^ (key[(a2>>11)&3]+a2) ^ 0x33) & 0xFFFFFFFF) v6 &= 0xFFFFFFFF v7 = v7 + 0x100000000 - (((v6 + ((v6 << 4) ^ (v6 >> 5))) ^ (key[a2&3]+a2) ^ 0x44) & 0xFFFFFFFF) v7 &= 0xFFFFFFFF flag[i+1] = v6 flag[i] = v7 print(hex(v7), hex(v6)) for f in flag: print(f.to_bytes(4, "little").decode(), end='') # fakeflag{Is_there_anywhere_else}
跑出来发现是假flagfakeflag{Is_there_anywhere_else}，main里面是假校验，
分析发现注册了一个退出时调用的函数sub_4016BC，NOP去混淆反编译
这里才是真check，对xxtea加密后的flag移位异或，再跟真ans校验
移位的时候根据最高为决定移位后是否异或0x84A6972F，逆向看的时候注意最低位，异或0x84A6972F后最低位为1，否则为0，所以解密根据最低位判断是否异或0x84A6972F
复制代码 隐藏代码flag = [0xB6DDB3A9, 0x36162C23, 0x1889FABF, 0x6CE4E73B, 0xA5AF8FC, 0x21FF8415, 0x44859557, 0x2DC227B7] for i in range(8): for _ in range(32): v0 = flag[i] if ((v0 & 1) == 1): v0 ^= 0x84A6972F v0 = v0 >> 1 v0 |= 0x80000000 else: v0 = v0 >> 1 flag[i] = v0
继续xxtea解密得到真flagd3ctf{ea3yjunk_c0d3_4nd_ea5y_re}
RandomVm
srand设置随机数种子0xD33B470，假随机，可以直接把rand跑出来
大量函数都是上面的结构，先进行一段操作，再设置跳转表，rand一个随机数选择下一个执行的函数
每个函数对应一条虚拟机指令，控制流由跳转表和rand控制，需要分析每个函数的功能与跳转关系，100+函数手动分析是不可能的，用IDA Python解析一下
从入口开始解析，通过解析汇编指令获取跳转表，同时记录每个函数反编译的虚拟机指令
复制代码 隐藏代码import idc import idaapi start = 0x717F funcs = {} # 递归找函数关系 def recur(addr): print(hex(addr)) if (addr == 0x241A): return ea = addr value_dic = {} while (True): ins = idc.generate_disasm_line(ea, 0) if (ins.startswith("mov")): op0 = idc.print_operand(ea, 0) op1 = idc.print_operand(ea, 1) # 过滤eax rax if (op0[0] in "er"): op0 = op0[1:] if (op1[0] in "er"): op1 = op1[1:] value_dic[op0] = op1 value_dic[op0] = op1 if (op0.startswith("[rbp+var_")): if (op1[-1] != 'h'): value_dic[op0] = value_dic[op1] # print(hex(ea), ins) if (ins == "call _rand" and len(value_dic) >= 10): break ins_len = idc.create_insn(ea) ea += ins_len # xor print(value_dic) xor_ins = idc.print_operand(ea+0x36, 1)[:-1] xor = int(xor_ins, 16) nexts = [] for i in ["60", "58", "50", "48", "40", "38", "30", "28", "20", "18"]: next = int(value_dic[f"[rbp+var_{i}]"][:-1], 16) next = ((next ^ xor) + addr) & 0xFFFFFFFFFFFFFFFF nexts.append(next) funcs[addr] = nexts for next in nexts: if (next not in funcs): recur(next) ea = start idc.set_name(ea, "main_main") recur(ea) print(funcs) for ea in funcs: src = str(idaapi.decompile(ea)).split('\n') print(f"{hex(ea)}: \"{src[5]}\",")
分析后得到所有函数的关系，以及每个函数对应的虚拟机指令，手动优化一下
复制代码 隐藏代码ops = { 0x717f: ([0x6bc8, 0x340a, 0x2917, 0x2db3, 0x6233, 0x4f23, 0x16f8, 0x1e22, 0x2f84, 0x2db3], " array[r0] = 0;"), 0x6bc8: ([0x55a9, 0x604e, 0x3725, 0x2917, 0x1fb5, 0x2425, 0x6d19, 0x7095, 0x16f8, 0x26a4], " *((_BYTE *)&flag + (unsigned __int8)r1) = ((int)*((unsigned __int8 *)&flag + (unsigned __int8)r1) >> array[r0]) | (*((_BYTE *)&flag + (unsigned __int8)r1) << (8 - array[r0]));"), 0x55a9: ([0x5c94, 0x62f3, 0x3d82, 0x3d82, 0x40cb, 0x3959, 0x5676, 0x40cb, 0x3f0e, 0x6154], " array[r0] = 0;"), 0x5c94: ([0x1cd0, 0x3308, 0x1a4c, 0x1e22, 0x1cd0, 0x16f8, 0x16f8, 0x1a4c, 0x1a4c, 0x44aa], " --r0;"), 0x1cd0: ([0x3f0e, 0x41aa, 0x66a4, 0x3a4b, 0x481b, 0x7375, 0x7375, 0x2cd4, 0x51ff, 0x5f5c], " array[r0] = syscall((char)array[r0], (unsigned int)(char)array[r0 + 1], &array[r0 + 2], (unsigned int)(char)array[r0 + 3]);"), 0x3f0e: ([0x2917, 0x2917, 0x3bf0, 0x5676, 0x55a9, 0x5676, 0x3bf0, 0x3f0e, 0x3959, 0x3f0e], " ++r0;"), 0x2917: ([0x340a, 0x43c2, 0x3e48, 0x24db, 0x24db, 0x1ee8, 0x55a9, 0x5002, 0x2425, 0x2771], " *((_BYTE *)&flag + (unsigned __int8)r1) ^= array[r0];"), 0x340a: ([0x3f0e, 0x25b1, 0x42fc, 0x51ff, 0x3f0e, 0x5676, 0x64d3, 0x3058, 0x3f0e, 0x3959], " array[r0] = syscall((char)array[r0], (unsigned int)(char)array[r0 + 1], &array[r0 + 2], (unsigned int)(char)array[r0 + 3]);"), 0x25b1: ([0x24db, 0x7809, 0x42fc, 0x5baf, 0x1ee8, 0x26a4, 0x4570, 0x5baf, 0x284a, 0x340a], " *((_BYTE *)&flag + (unsigned __int8)r1) = array[r0];"), 0x24db: ([0x5754, 0x2f84, 0x3f0e, 0x42fc, 0x3d82, 0x7462, 0x3b11, 0x4f23, 0x2db3, 0x7375], " array[r0] = 0;"), 0x5754: ([0x3876, 0x7809, 0x2261, 0x2261, 0x51ff, 0x6bc8, 0x340a, 0x51ff, 0x2261, 0x51ff], " --array[r0];"), 0x3876: ([0x2cd4, 0x196d, 0x6ed7, 0x3876, 0x5002, 0x7462, 0x196d, 0x7462, 0x6ed7, 0x4a13], " ++array[r0];"), 0x2cd4: ([0x63d2, 0x3725, 0x6154, 0x63d2, 0x3058, 0x196d, 0x209a, 0x2182, 0x2cd4, 0x6154], " ++array[r0];"), 0x63d2: ([0x1b12, 0x5c94, 0x63d2, 0x472e, 0x1bf1, 0x43c2, 0x679b, 0x196d, 0x63d2, 0x7462], " ++array[r0];"), 0x1b12: ([0x6154, 0x7462, 0x1b12, 0x6ed7, 0x2f84, 0x2e92, 0x3137, 0x4a13, 0x4a13, 0x1bf1], " ++array[r0];"), 0x6154: ([0x6ed7, 0x65c5, 0x4a13, 0x6ed7, 0x5aa9, 0x5aa9, 0x43c2, 0x63d2, 0x679b, 0x3137], " ++array[r0];"), 0x6ed7: ([0x209a, 0x2337, 0x209a, 0x6ed7, 0x3fd4, 0x6a77, 0x68a6, 0x209a, 0x3876, 0x6ed7], " ++array[r0];"), 0x209a: ([0x5002, 0x3b11, 0x3058, 0x3216, 0x5103, 0x209a, 0x1b12, 0x4570, 0x5002, 0x5aa9], " ++array[r0];"), 0x5002: ([0x5f5c, 0x604e, 0x209a, 0x3058, 0x6154, 0x2182, 0x196d, 0x4570, 0x4570, 0x3876], " ++array[r0];"), 0x5f5c: ([0x7462, 0x2182, 0x5e5b, 0x5e5b, 0x1bf1, 0x2182, 0x2cd4, 0x6a77, 0x7541, 0x5f5c], " ++array[r0];"), 0x7462: ([0x4570, 0x188f, 0x5e5b, 0x4f23, 0x5002, 0x7462, 0x196d, 0x2cd4, 0x3876, 0x4570], " ++array[r0];"), 0x4570: ([0x65c5, 0x52ed, 0x5002, 0x4570, 0x3876, 0x209a, 0x604e, 0x16f8, 0x1a4c, 0x5f5c], " ++array[r0];"), 0x65c5: ([0x2337, 0x52ed, 0x5002, 0x6ed7, 0x5e5b, 0x2337, 0x7462, 0x5c94, 0x52ed, 0x196d], " ++array[r0];"), 0x2337: ([0x2337, 0x4f23, 0x196d, 0x5f5c, 0x196d, 0x3725, 0x1a4c, 0x604e, 0x4f23, 0x5f5c], " ++array[r0];"), 0x4f23: ([0x16f8, 0x2db3, 0x3058, 0x62f3, 0x3b11, 0x3b11, 0x65c5, 0x62f3, 0x188f, 0x604e], " ++array[r0];"), 0x16f8: ([0x6fb6, 0x6fb6, 0x340a, 0x1a4c, 0x5c94, 0x6233, 0x5c94, 0x1cd0, 0x5c94, 0x6a77], " --r0;"), 0x6fb6: ([0x4f23, 0x40cb, 0x5e5b, 0x66a4, 0x604e, 0x2db3, 0x2db3, 0x6fb6, 0x6df8, 0x66a4], " ++array[r0];"), 0x40cb: ([0x3725, 0x3725, 0x6233, 0x40cb, 0x464f, 0x6d19, 0x7375, 0x66a4, 0x464f, 0x40cb], " ++array[r0];"), 0x3725: ([0x55a9, 0x2917, 0x5e5b, 0x48fe, 0x2425, 0x2b07, 0x136e, 0x2337, 0x724c, 0x66a4], " *((_BYTE *)&flag + (unsigned __int8)r1) = ((int)*((unsigned __int8 *)&flag + (unsigned __int8)r1) >> array[r0]) | (*((_BYTE *)&flag + (unsigned __int8)r1) << (8 - array[r0]));"), 0x5e5b: ([0x5002, 0x5f5c, 0x63d2, 0x2337, 0x5f5c, 0x196d, 0x1b12, 0x2182, 0x1bf1, 0x5e5b], " ++array[r0];"), 0x196d: ([0x5f5c, 0x604e, 0x2cd4, 0x63d2, 0x3876, 0x3876, 0x5e5b, 0x6154, 0x65c5, 0x5e5b], " ++array[r0];"), 0x604e: ([0x2182, 0x66a4, 0x3876, 0x52ed, 0x188f, 0x62f3, 0x62f3, 0x4f23, 0x2337, 0x4570], " ++array[r0];"), 0x2182: ([0x65c5, 0x52ed, 0x3876, 0x2182, 0x2337, 0x65c5, 0x2182, 0x5927, 0x3725, 0x5e5b], " ++array[r0];"), 0x52ed: ([0x3b11, 0x52ed, 0x2182, 0x188f, 0x6fb6, 0x52ed, 0x65c5, 0x3b11, 0x188f, 0x52ed], " ++array[r0];"), 0x3b11: ([0x2337, 0x6d19, 0x7462, 0x188f, 0x62f3, 0x3b11, 0x62f3, 0x6fb6, 0x66a4, 0x7462], " ++array[r0];"), 0x6d19: ([0x6df8, 0x6df8, 0x188f, 0x66a4, 0x6fb6, 0x40cb, 0x66a4, 0x2db3, 0x464f, 0x2db3], " ++array[r0];"), 0x6df8: ([0x464f, 0x40cb, 0x6d19, 0x6fb6, 0x6df8, 0x464f, 0x6fb6, 0x66a4, 0x6233, 0x464f], " ++array[r0];"), 0x464f: ([0x40cb, 0x40cb, 0x6d19, 0x5927, 0x6df8, 0x464f, 0x188f, 0x6d19, 0x6bc8, 0x6233], " ++array[r0];"), 0x5927: ([0x55a9, 0x1cd0, 0x16f8, 0x2b07, 0x64d3, 0x6a77, 0x3a4b, 0x41aa, 0x2261, 0x3e48], " *((_BYTE *)&flag + (unsigned __int8)r1) = ((int)*((unsigned __int8 *)&flag + (unsigned __int8)r1) >> array[r0]) | (*((_BYTE *)&flag + (unsigned __int8)r1) << (8 - array[r0]));"), 0x2b07: ([0x3d82, 0x7809, 0x5e5b, 0x5676, 0x3a4b, 0x3e48, 0x5676, 0x3959, 0x6df8, 0x17be], " array[r0] = 0;"), 0x3d82: ([0x2b07, 0x3f0e, 0x3959, 0x3d82, 0x7375, 0x3308, 0x48fe, 0x55a9, 0x5676, 0x3bf0], " ++r0;"), 0x3959: ([0x53cc, 0x153a, 0x284a, 0x2917, 0x3bf0, 0x136e, 0x2b07, 0x2f84, 0x26a4, 0x55a9], " ++r0;"), 0x53cc: ([0x472e, 0x2bdd, 0x2771, 0x4e18, 0x3137, 0x2182, 0x5baf, 0x7462, 0x43c2, 0x3959], " array[r0] = 0;"), 0x472e: ([0x4e18, 0x6154, 0x5aa9, 0x63d2, 0x7541, 0x65c5, 0x3725, 0x43c2, 0x4e18, 0x66a4], " ++array[r0];"), 0x4e18: ([0x679b, 0x5002, 0x472e, 0x2a19, 0x153a, 0x63d2, 0x2182, 0x2cd4, 0x3137, 0x42fc], " ++array[r0];"), 0x679b: ([0x4e18, 0x1bf1, 0x3137, 0x679b, 0x7375, 0x3cbc, 0x62f3, 0x6ed7, 0x43c2, 0x55a9], " ++array[r0];"), 0x1bf1: ([0x3137, 0x65c5, 0x1bf1, 0x209a, 0x3058, 0x63d2, 0x5aa9, 0x5f5c, 0x4e18, 0x3058], " ++array[r0];"), 0x3137: ([0x1610, 0x3a4b, 0x3137, 0x3216, 0x3959, 0x4a13, 0x1b12, 0x1bf1, 0x68a6, 0x3876], " ++array[r0];"), 0x1610: ([0x3725, 0x2e92, 0x340a, 0x6233, 0x481b, 0x44aa, 0x4d52, 0x2f84, 0x7375, 0x16f8], " ++array[r0];"), 0x2e92: ([0x188f, 0x43c2, 0x6233, 0x3876, 0x65c5, 0x464f, 0x196d, 0x679b, 0x4b0f, 0x7375], " ++array[r0];"), 0x188f: ([0x62f3, 0x6df8, 0x6bc8, 0x52ed, 0x6fb6, 0x6fb6, 0x188f, 0x2182, 0x6d19, 0x52ed], " ++array[r0];"), 0x62f3: ([0x604e, 0x6d19, 0x604e, 0x66a4, 0x4f23, 0x4570, 0x4f23, 0x2337, 0x3b11, 0x6fb6], " ++array[r0];"), 0x66a4: ([0x6fb6, 0x2db3, 0x3b11, 0x188f, 0x4f23, 0x464f, 0x2db3, 0x66a4, 0x6d19, 0x2db3], " ++array[r0];"), 0x2db3: ([0x3b11, 0x6df8, 0x604e, 0x464f, 0x62f3, 0x6d19, 0x62f3, 0x2db3, 0x6df8, 0x6d19], " ++array[r0];"), 0x43c2: ([0x3137, 0x5002, 0x1b12, 0x4a13, 0x1b12, 0x1bf1, 0x7809, 0x7809, 0x4a13, 0x679b], " ++array[r0];"), 0x4a13: ([0x63d2, 0x65c5, 0x1b12, 0x3058, 0x68a6, 0x3058, 0x472e, 0x3876, 0x2cd4, 0x4a13], " ++array[r0];"), 0x3058: ([0x2cd4, 0x5f5c, 0x1bf1, 0x472e, 0x5aa9, 0x6154, 0x43c2, 0x209a, 0x2cd4, 0x4e18], " ++array[r0];"), 0x5aa9: ([0x1bf1, 0x2cd4, 0x6154, 0x43c2, 0x6df8, 0x3216, 0x2e92, 0x6154, 0x54ca, 0x5676], " ++array[r0];"), 0x3216: ([0x7375, 0x3058, 0x5aa9, 0x5c94, 0x12a8, 0x78f1, 0x65c5, 0x11c9, 0x5103, 0x78f1], " ++array[r0];"), 0x7375: ([0x26a4, 0x153a, 0x7095, 0x64d3, 0x7375, 0x3959, 0x284a, 0x7095, 0x78f1, 0x3bf0], " ++r0;"), 0x26a4: ([0x5002, 0x3725, 0x2f84, 0x5676, 0x604e, 0x62f3, 0x2f84, 0x5754, 0x2bdd, 0x3876], " array[r0] = 0;"), 0x2f84: ([0x136e, 0x1ee8, 0x48fe, 0x3959, 0x5833, 0x3565, 0x3bf0, 0x2f84, 0x3959, 0x724c], " ++r0;"), 0x136e: ([0x2a19, 0x5f5c, 0x17be, 0x42fc, 0x3959, 0x78f1, 0x3e48, 0x3bf0, 0x2771, 0x3725], " *((_BYTE *)&flag + (unsigned __int8)r1) ^= array[r0];"), 0x2a19: ([0x3bf0, 0x209a, 0x65c5, 0x3bf0, 0x3bf0, 0x24db, 0x7095, 0x78f1, 0x17be, 0x7095], " *((_BYTE *)&flag + (unsigned __int8)r1) = array[r0];"), 0x3bf0: ([0x5754, 0x3d82, 0x3d82, 0x40cb, 0x464f, 0x3959, 0x6df8, 0x3d82, 0x5754, 0x481b], " array[r0] = 0;"), 0x481b: ([0x48fe, 0x340a, 0x5676, 0x5754, 0x6ed7, 0x5d6d, 0x153a, 0x3cbc, 0x6df8, 0x2f84], " ++r0;"), 0x48fe: ([0x1fb5, 0x2771, 0x241a, 0x44aa, 0x1fb5, 0x12a8, 0x5d6d, 0x5d6d, 0x5d6d, 0x5baf], " *((_BYTE *)&flag + (unsigned __int8)r1) ^= array[r0];"), 0x1fb5: ([0x65c5, 0x2425, 0x69b1, 0x6d19, 0x464f, 0x241a, 0x5676, 0x153a, 0x2425, 0x3e48], " array[r0] = *((_BYTE *)&flag + (unsigned __int8)r1);"), 0x2425: ([0x2cd4, 0x2f84, 0x3308, 0x3308, 0x48fe, 0x2a19, 0x48fe, 0x2a19, 0x3308, 0x2a19], " ++r1;"), 0x3308: ([0x62f3, 0x724c, 0x5d6d, 0x5676, 0x3e48, 0x3e48, 0x5d6d, 0x6154, 0x1fb5, 0x5d6d], " *((_BYTE *)&flag + (unsigned __int8)r1) ^= array[r0];"), 0x724c: ([0x16f8, 0x64d3, 0x2425, 0x7717, 0x2bdd, 0x3959, 0x4d52, 0x78f1, 0x2425, 0x2b07], " *((_BYTE *)&flag + (unsigned __int8)r1) ^= array[r0];"), 0x64d3: ([0x3308, 0x5d6d, 0x3d82, 0x26a4, 0x724c, 0x209a, 0x51ff, 0x5002, 0x5676, 0x724c], " ++r0;"), 0x5d6d: ([0x2425, 0x3e48, 0x3e48, 0x55a9, 0x5676, 0x3e48, 0x2a19, 0x3e48, 0x2425, 0x3e48], " array[r0] = *((_BYTE *)&flag + (unsigned __int8)r1);"), 0x3e48: ([0x25b1, 0x2a19, 0x48fe, 0x48fe, 0x48fe, 0x2a19, 0x48fe, 0x2a19, 0x3308, 0x48fe], " ++r1;"), 0x5676: ([0x2b07, 0x1ee8, 0x24db, 0x3d82, 0x7095, 0x5833, 0x24db, 0x7095, 0x7375, 0x3308], " ++r0;"), 0x1ee8: ([0x2337, 0x6a77, 0x7375, 0x196d, 0x3a4b, 0x65c5, 0x679b, 0x63d2, 0x7717, 0x7462], " array[r0] = 0;"), 0x6a77: ([0x24db, 0x5aa9, 0x51ff, 0x284a, 0x5927, 0x481b, 0x241a, 0x5baf, 0x6154, 0x40cb], " *((_BYTE *)&flag + (unsigned __int8)r1) = ((int)*((unsigned __int8 *)&flag + (unsigned __int8)r1) >> array[r0]) | (*((_BYTE *)&flag + (unsigned __int8)r1) << (8 - array[r0]));"), 0x51ff: ([0x26a4, 0x55a9, 0x53cc, 0x5e5b, 0x51ff, 0x24db, 0x26a4, 0x4e18, 0x5d6d, 0x2b07], " if ( (char)array[r0] < 0 ) rand();"), 0x284a: ([0x5676, 0x5e5b, 0x7375, 0x464f, 0x4570, 0x69b1, 0x7717, 0x1b12, 0x3f0e, 0x2337], " array[r0] = 0;"), 0x69b1: ([0x78f1, 0x153a, 0x3d82, 0x6ed7, 0x42fc, 0x44aa, 0x7809, 0x2cd4, 0x51ff, 0x44aa], " --r1;"), 0x78f1: ([0x7638, 0x5002, 0x41aa, 0x3876, 0x1a4c, 0x51ff, 0x3cbc, 0x7717, 0x2f84, 0x26a4], " array[r0] = 0;"), 0x7638: ([0x5aa9, 0x44aa, 0x464f, 0x3876, 0x2a19, 0x3137, 0x3d82, 0x2337, 0x2261, 0x48fe], " --array[r0];"), 0x44aa: ([0x44aa, 0x44aa, 0x44aa, 0x5c94, 0x69b1, 0x5d6d, 0x44aa, 0x69b1, 0x44aa, 0x44aa], " --r1;"), 0x2261: ([0x7095, 0x17be, 0x7095, 0x26a4, 0x284a, 0x3bf0, 0x24db, 0x55a9, 0x6bc8, 0x24db], " if ( (char)array[r0] < 0 ) rand();"), 0x7095: ([0x4570, 0x7717, 0x7375, 0x7717, 0x63d2, 0x4f23, 0x65c5, 0x5754, 0x7717, 0x3959], " array[r0] = 0;"), 0x7717: ([0x17be, 0x1cd0, 0x3565, 0x2261, 0x3565, 0x5c94, 0x43c2, 0x2261, 0x2261, 0x3565], " --array[r0];"), 0x17be: ([0x7717, 0x2425, 0x64d3, 0x284a, 0x2db3, 0x5002, 0x1ee8, 0x6df8, 0x6ed7, 0x2db3], " array[r0] = 0;"), 0x3565: ([0x55a9, 0x16f8, 0x6df8, 0x48fe, 0x62f3, 0x6bc8, 0x55a9, 0x2f84, 0x17be, 0x363b], " if ( (char)array[r0] < 0 ) rand();"), 0x363b: ([0x2771, 0x209a, 0x2917, 0x3565, 0x1b12, 0x1b12, 0x5676, 0x6fb6, 0x5754, 0x41aa], " array[r0] = 0;"), 0x2771: ([0x4f23, 0x24db, 0x6a77, 0x25b1, 0x40cb, 0x25b1, 0x2a19, 0x2db3, 0x679b, 0x12a8], " ++r1;"), 0x12a8: ([0x1cd0, 0x3725, 0x65c5, 0x17be, 0x7375, 0x2db3, 0x2a19, 0x604e, 0x1b12, 0x2425], " ++r1;"), 0x41aa: ([0x1cd0, 0x3565, 0x6d19, 0x2f84, 0x3137, 0x2261, 0x1cd0, 0x481b, 0x66a4, 0x3137], " array[r0] = syscall((char)array[r0], (unsigned int)(char)array[r0 + 1], &array[r0 + 2], (unsigned int)(char)array[r0 + 3]);"), 0x1a4c: ([0x1e22, 0x41aa, 0x6233, 0x1e22, 0x340a, 0x16f8, 0x1a4c, 0x6233, 0x6233, 0x16f8], " --r0;"), 0x1e22: ([0x1a4c, 0x4a13, 0x24db, 0x24db, 0x1cd0, 0x1a4c, 0x340a, 0x340a, 0x5c94, 0x42fc], " --r0;"), 0x42fc: ([0x3058, 0x7717, 0x7095, 0x7095, 0x6a77, 0x1cd0, 0x3e48, 0x5927, 0x63d2, 0x64d3], " ++r0;"), 0x6233: ([0x340a, 0x1cd0, 0x6233, 0x340a, 0x6233, 0x6233, 0x1a4c, 0x340a, 0x340a, 0x1a4c], " --r0;"), 0x3cbc: ([0x7375, 0x5754, 0x464f, 0x3bf0, 0x1a4c, 0x3cbc, 0x241a, 0x4a13, 0x1470, 0x55a9], " --r0;"), 0x1470: ([0x5e5b, 0x340a, 0x3725, 0x40cb, 0x41aa, 0x2771, 0x3959, 0x1a4c, 0x5e5b, 0x188f], " --r0;"), 0x153a: ([0x3a4b, 0x2f84, 0x1b12, 0x2337, 0x52ed, 0x209a, 0x4d52, 0x41aa, 0x43c2, 0x2182], " array[r0] = 0;"), 0x3a4b: ([0x4c8c, 0x6bc8, 0x284a, 0x26a4, 0x24db, 0x26a4, 0x3f0e, 0x4d52, 0x6a77, 0x2f84], " ++r0;"), 0x4c8c: ([0x340a, 0x3f0e, 0x1ee8, 0x1ee8, 0x3a4b, 0x4a13, 0x2bdd, 0x42fc, 0x7541, 0x41aa], " ++r0;"), 0x2bdd: ([0x78f1, 0x63d2, 0x2a19, 0x136e, 0x284a, 0x724c, 0x5676, 0x2261, 0x2261, 0x3058], " --array[r0];"), 0x7541: ([0x16f8, 0x62f3, 0x2b07, 0x2a19, 0x6154, 0x44aa, 0x42fc, 0x2cd4, 0x16f8, 0x51ff], " ++r0;"), 0x4d52: ([0x7375, 0x7095, 0x51ff, 0x2f84, 0x5f5c, 0x604e, 0x25b1, 0x64d3, 0x3b11, 0x7375], " ++r1;"), 0x7809: ([0x5002, 0x3959, 0x4d52, 0x241a, 0x1e22, 0x3cbc, 0x1e22, 0x7809, 0x7809, 0x5d6d], " --r0;"), 0x5baf: ([0x3058, 0x66a4, 0x5754, 0x604e, 0x40cb, 0x241a, 0x196d, 0x3959, 0x5833, 0x2425], " array[r0] = *((_BYTE *)&flag + (unsigned __int8)r1);"), 0x5833: ([0x5c94, 0x43c2, 0x7717, 0x51ff, 0x4f23, 0x5f5c, 0x2771, 0x42fc, 0x3959, 0x7375], " array[r0] = 0;"), 0x11c9: ([0x62f3, 0x5aa9, 0x2182, 0x2cd4, 0x6154, 0x5f5c, 0x4a13, 0x241a, 0x3d82, 0x1fb5], " ++array[r0];"), 0x5103: ([0x1a4c, 0x1b12, 0x5927, 0x64d3, 0x25b1, 0x2771, 0x5f5c, 0x4a13, 0x6233, 0x5f5c], " ++array[r0];"), 0x54ca: ([0x209a, 0x1b12, 0x724c, 0x5baf, 0x209a, 0x5f5c, 0x2bdd, 0x3058, 0x3058, 0x3bf0], " ++array[r0];"), 0x68a6: ([0x3565, 0x209a, 0x3308, 0x42fc, 0x6fb6, 0x42fc, 0x3725, 0x3058, 0x5aa9, 0x1bf1], " ++array[r0];"), 0x4b0f: ([0x2917, 0x48fe, 0x3137, 0x5baf, 0x2bdd, 0x2425, 0x62f3, 0x2771, 0x136e, 0x5754], " *((_BYTE *)&flag + (unsigned __int8)r1) = ((int)*((unsigned __int8 *)&flag + (unsigned __int8)r1) >> array[r0]) | (*((_BYTE *)&flag + (unsigned __int8)r1) << (8 - array[r0]));"), 0x3fd4: ([0x3bf0, 0x4a13, 0x209a, 0x6a77, 0x17be, 0x1cd0, 0x63d2, 0x5002, 0x63d2, 0x64d3], " ++array[r0];") }
虚拟机指令有下面几种
复制代码 隐藏代码""" array[r0] = 0 array[r0] += 1 array[r0] -= 1 r0 += 1 r0 -= 1 r1 += 1 r1 -= 1 flag[r1] = (flag[r1] >> array[r0]) | (flag[r1] << (8 - array[r0])) array[r0] = syscall(array[r0], array[r0+1], &array[r0+2], array[r0+3]) flag[r1] ^= array[r0] flag[r1] = array[r0] array[r0] = flag[r1] if (array[r0] < 0) rand(); """
除了基本的数据处理外，使用syscall实现系统调用，还有if分支根据array[r0]决定是否跳过一个随机数，即控制执行流
复制代码 隐藏代码pc = 0x717F i = 0 skips = [18, 22, 48, 168, 172, 312, 340, 370, 397, 449, 478, 595, 599, 623, 627, 675] while (pc != 0x241A): print(i, hex(pc), ops[pc][1]) if (i in skips): i += 1 r = rands[i] i += 1 pc = ops[pc][0][r]
根据跑出来的随机数解析一下控制流，类似于下面这种需要手动设置一下skip跳过一个随机数
复制代码 隐藏代码""" 16 0x284a array[r0] = 0; 17 0x7717 --array[r0]; 18 0x3565 if ( (char)array[r0] < 0 ) rand(); """
虚拟指令里面用syscall(0)输入1个字符，进行一些移位异或操作
复制代码 隐藏代码""" array[0] = 0 array[1] = 0 array[3] = 1 10 array[2] = getchar() flag[0] ^= array[2] flag[1] = array[2] array[2] = 3 flag[1] = (flag[1] >> 3 | (flag[1] << 5) flag[1] ^= 3 """
还有syscall(101, 0, 0, 0)，即ptrace反调试检测，需要注意在无调试的情况下，第一次调用ptrace返回值为0，if不跳过rand，但是后续继续调用ptrace会返回-1，if需要跳过rand
复制代码 隐藏代码""" array[4] = 101 array[5] = 0 array[6] = 0 array[7] = 0 array[8] = 0 array[4] = syscall(101, 0, 0, 0) # ptrace反调试, 0 """
输入完12个字符后，最后还有一段异或操作，人肉解析一下，纯体力活
复制代码 隐藏代码""" array[0] = 0 array[1] = 0 array[3] = 1 10 array[2] = getchar() flag[0] ^= array[2] flag[1] = array[2] array[2] = 3 flag[1] = (flag[1] >> 3 | (flag[1] << 5) flag[1] ^= 3 array[2] = 0 array[3] = 0 array[5] = 1 40 array[4] = getchar() flag[1] ^= array[4] flag[2] = array[4] array[4] = 101 array[5] = 0 array[6] = 0 array[7] = 0 array[8] = 0 array[4] = syscall(101, 0, 0, 0) # ptrace反调试, 0 array[4] = 5 flag[2] = (flag[2] >> 5 | (flag[2] << 3) array[4] = 0 array[5] = 0 array[7] = 1 191 array[6] = getchar() # array[4] = 1 flag[2] ^= array[6] flag[3] = array[6] array[6] = 101 array[7] = 0 array[8] = 0 array[9] = 0 array[10] = 0 array[6] = syscall(101, 0, 0, 0) # ptrace反调试, -1 array[6] = 6 flag[3] = (flag[3] >> 6 | (flag[3] << 2) array[6] = 0 array[7] = 0 array[9] = 1 332 array[8] = getchar() # array[6] = 1 flag[3] ^= array[8] falg[4] = array[8] array[8] = 7 flag[4] = (flag[4] >> 7 | (flag[4] << 1) flag[4] ^= 7 array[8] = 0 arry[9] = 0 array[11] = 1 362 array[10] = getchar() # array[8] = 1 flag[4] ^= array[10] flag[5] = array[10] array[10] = 4 flag[5] = (flag[5] >> 4 | (flag[5] << 4) flag[5] ^= 4 array[10] = 0 array[11] = 0 array[13] = 1 389 array[12] = getchar() # array[10] = 1 flag[5] ^= array[12] flag[6] = array[12] array[12] = 4 flag[6] = (flag[6] >> 4 | (flag[6] << 4) array[12] = 0 array[13] = 0 array[15] = 1 415 array[14] = getchar() # array[12] = 1 flag[6] ^= array[14] flag[7] = array[14] array[14] = 7 flag[7] = (flag[7] >> 7 | (flag[7] << 1) flag[7] ^= 7 array[14] = 0 array[15] = 0 array[17] = 1 441 array[16] = getchar() # array[14] = 1 flag[7] ^= array[16] flag[8] = array[16] array[16] = 7 flag[8] = (flag[8] >> 7 | (flag[8] << 1) array[16] = 0 array[17] = 0 array[19] = 1 470 array[18] = getchar() # array[16] = 1 flag[8] ^= array[18] flag[9] = array[18] flag[9] = (flag[9] >> 2 | (flag[9] << 6) 615 c = getchar() flag[9] ^= c flag[10] = c flag[10] = (flag[10] >> 4) | (flag[10] << 4) 645 c = getchar() flag[10] ^= c flag[11] = c flag[11] = (flag[11] >> 4) | (flag[11] << 4) 667 c = getchar() flag[11] ^= c flag[12] = c flag[12] = (flag[12] >> 7) | (flag[12] << 1) flag[12] ^= 7 flag[2] ^= flag[1] . . . flag[12] ^= flag[11] """
逆一下加密算法
复制代码 隐藏代码flag = [0, 0x9D, 0x6B, 0xA1, 0x02, 0xD7, 0xED, 0x40, 0xF6, 0x0E, 0xAE, 0x84, 0x19] for i in range(12, 1, -1): flag[i] ^= flag[i-1] flag[12] ^= 7 flag[12] = (flag[12] << 7) | (flag[12] >> 1) flag[12] &= 0xFF flag[11] ^= flag[12] flag[11] = (flag[11] << 4) | (flag[11] >> 4) flag[11] &= 0xFF flag[10] ^= flag[11] flag[10] = (flag[10] << 4) | (flag[10] >> 4) flag[10] &= 0xFF flag[9] ^= flag[10] flag[9] = (flag[9] << 2) | (flag[9] >> 6) flag[9] &= 0xFF flag[8] ^= flag[9] flag[8] = (flag[8] << 7) | (flag[8] >> 1) flag[8] &= 0xFF flag[7] ^= flag[8] flag[7] ^= 7 flag[7] = (flag[7] << 7) | (flag[7] >> 1) flag[7] &= 0xFF flag[6] ^= flag[7] flag[6] = (flag[6] << 4) | (flag[6] >> 4) flag[6] &= 0xFF flag[5] ^= flag[6] flag[5] ^= 4 flag[5] = (flag[5] << 4) | (flag[5] >> 4) flag[5] &= 0xFF flag[4] ^= flag[5] flag[4] ^= 7 flag[4] = (flag[4] << 7) | (flag[4] >> 1) flag[4] &= 0xFF flag[3] ^= flag[4] flag[3] = (flag[3] << 6) | (flag[3] >> 2) flag[3] &= 0xFF flag[2] ^= flag[3] flag[2] = (flag[2] << 5) | (flag[2] >> 3) flag[2] &= 0xFF flag[1] ^= flag[2] flag[1] ^= 3 flag[1] = (flag[1] << 3) | (flag[1] >> 5) flag[1] &= 0xFF # flag[0] ^= flag[1] print(bytes(flag))
解密拿到flagd3ctf{m3owJumpVmvM}
forest
main里面检查flag格式，把输入的17个字符转换称01字符串，末尾加0
重点在sub_CE1F50里面，把一段内存设置为可执行，然后触发int 3异常，使用sub_CE1A00函数（execption_handle）处理异常
复制代码 隐藏代码unsigned int __thiscall execption_handle(unsigned int **this) { unsigned int result; // eax unsigned int *v3; // ecx unsigned int *v4; // eax _DWORD *v5; // eax int v6; // ecx unsigned int v7; // edx void **v8; // ecx int v9; // esi int i; // ecx int v11; // edx int v12; // eax int v13; // esi int v14; // edx void **v15; // eax int v16; // [esp+10h] [ebp-2Ch] int v17; // [esp+14h] [ebp-28h] _DWORD *v18; // [esp+18h] [ebp-24h] GetCurrentThreadId(); result = **this; if ( result <= 0xC0000005 ) { if ( result != 0xC0000005 ) { if ( result != 0x80000003 ) { if ( result != 0x80000004 ) return result; v3 = this[1]; if ( ((v3[46] - (_DWORD)&code) & 0x3F) == 7 && v3[44] == 1 ) v3[46] += 0x17; v4 = this[1]; goto LABEL_33; } if ( byte_CE6028 ) { byte_CE6028 = 0; R2 = (int)malloc(4u); R1 = (int)malloc(4u); v5 = malloc(4u); v6 = R1; v7 = kk; v18 = v5; R0 = (int)v5; *(_DWORD *)R1 = 0; *v5 = 0; v17 = v6; if ( (unsigned int)len > v7 ) { v8 = &flag; if ( HIDWORD(len) >= 0x10 ) v8 = (void **)flag; v16 = R2; v9 = 0; *(_DWORD *)R2 = *((_BYTE *)v8 + v7) != 0x30; kk = v7 + 1; for ( i = 0; i < 0x483D; ++i ) { if ( *((_BYTE *)&code + i) == 0xFF && *((_BYTE *)&code + i + 1) == 0xFF && *((_BYTE *)&code + i + 2) == 0xFF && *((_BYTE *)&code + i + 3) == 0xFF ) { v11 = v9 % 5; if ( v9 % 5 == 1 || v11 == 3 ) { v12 = v17; // R1 } else if ( v11 == 2 || v11 == 4 ) { v12 = (int)v18; // R0 } else { v12 = v16; // R2 } *(_DWORD *)((char *)&code + i) = v12; ++v9; i += 3; } } this[1][46] = (unsigned int)&code; this[1][48] |= 0x100u; return -1; } LABEL_39: sub_CE28B0(); } return(0); } right(); } if ( result != 0xC0000096 ) return result; v13 = kk; v14 = *(_DWORD *)R1 + 17 * *(_DWORD *)R0; if ( kk >= (unsigned int)len ) { return(1); goto LABEL_39; } v15 = &flag; if ( HIDWORD(len) >= 0x10 ) v15 = (void **)flag; *(_DWORD *)R2 = *((_BYTE *)v15 + kk) != 0x30; kk = v13 + 1; this[1][46] = (unsigned int)&code + 0x40 * v14; v4 = this[1]; LABEL_33: v4[48] |= 0x100u; return -1; }
在execption_handle中根据异常码进行处理
复制代码 隐藏代码// ksarm.h #define STATUS_ACCESS_VIOLATION 0xc0000005 #define STAUSBREAKPOINT 0x80000003 #define STATUS_SINGLE_STEP 0x80000004 #define STATUS_PRIVILEGED_INSTRUCTION 0xc0000096
第一次int 3触发断点异常0x80000003，对应下面的异常处理代码
复制代码 隐藏代码if (byte_CE6028) { byte_CE6028 = 0; R2 = (int)malloc(4u); R1 = (int)malloc(4u); v5 = malloc(4u); v6 = R1; v7 = kk; v18 = v5; R0 = (int)v5; *(_DWORD *)R1 = 0; *v5 = 0; v17 = v6; if ((unsigned int)len > v7) { v8 = &flag; if (HIDWORD(len) >= 0x10) v8 = (void **)flag; v16 = R2; v9 = 0; *(_DWORD *)R2 = *((_BYTE *)v8 + v7) != 0x30; kk = v7 + 1; for (i = 0; i < 0x483D; ++i) { if (*((_BYTE *)&code + i) == 0xFF && *((_BYTE *)&code + i + 1) == 0xFF && *((_BYTE *)&code + i + 2) == 0xFF && *((_BYTE *)&code + i + 3) == 0xFF) { v11 = v9 % 5; if (v9 % 5 == 1 || v11 == 3) { v12 = v17; // R1 } else if (v11 == 2 || v11 == 4) { v12 = (int)v18; // R0 } else { v12 = v16; // R2 } *(_DWORD *)((char *)&code + i) = v12; ++v9; i += 3; } } this[1][46] = (unsigned int)&code; this[1][48] |= 0x100u; return -1; } LABEL_39: sub_CE28B0(); }
这段代码只能执行一次，后续再触发0x80000003异常程序会结束运行，代码里面malloc了3个变量，并使用这3个变量替换code(前面修改了可执行权限的内存)中的0xFFFFFFFF
R2的初值由*(_DWORD *)R2 = *((_BYTE *)v8 + v7) != 0x30;决定，这里是flag的第一个字符
将code初始化之后，this[1][46] = (unsigned int)&code;修改线程结构体的EIP，使异常处理结束后程序进入到code中执行
分析一下code部分代码，code代码中包含很多的代码块，每一块的长度为0x40，根据前面修改的规律可以知道在code块中R0、R1、R2的位置固定
代码块中还有cli指令，由于cli指令是特权指令，ring3无法执行，因此运行到cli指令会触发0xc0000096异常，分析对应的处理代码
复制代码 隐藏代码v13 = kk; v14 = *(_DWORD *)R1 + 17 * *(_DWORD *)R0; if (kk >= (unsigned int)len) { return (1); goto LABEL_39; } v15 = &flag; if (HIDWORD(len) >= 0x10) v15 = (void **)flag; *(_DWORD *)R2 = *((_BYTE *)v15 + kk) != 0x30; kk = v13 + 1; this[1][46] = (unsigned int)&code + 0x40 * v14; v4 = this[1]; v4[48] |= 0x100u;
cli指令触发异常后，根据R1+17*R0的值确定下一个执行的代码块，修改EIP进入新的代码块，并且根据flag的01字符设置R2
结合code中的内容，在code代码中会设置R0、R1的值，接着使用cli触发异常，根据R0、R1的值选择下一个代码块，R2中储存了flag的一个bit
调试发现在code中还会触发0x80000004异常
跟踪一下发现这个异常是TF标志位造成的，TF标志位为1时，执行一条指令后就会触发0x80000004异常，在execption_handle中，返回时会设置v4[48] |= 0x100u;，这里设置的就是TF标志位
TF标志位触发异常后，会确定异常发生的位置，当异常发生位置为7，即mov eax, [eax]执行后，根据eax寄存器的确定是否进行跳转
复制代码 隐藏代码if (result != 0x80000004) return result; v3 = this[1]; if (((v3[46] - (_DWORD)&code) & 0x3F) == 7 && v3[44] == 1) v3[46] += 0x17; v4 = this[1]; v4[48] |= 0x100u;
结合跳转的位置和code中的代码，这里实际是根据R2进行调整，如果R2，即flag为1，跳转到下一个cli块中设置R1、R0，综合分析知道这里是根据flag的01值决定下一个代码块，在每一个代码块中有两个可跳转的位置
使用IDA Python解析代码块，获取每个代码块中的两个跳转位置
复制代码 隐藏代码import idc import idaapi image_base = idaapi.get_imagebase() code_off = 0x6030 code_size = 0x4840 start = image_base + code_off end = image_base + code_off + code_size op_ls = [(-1, -1) for _ in range(0x121)] for idx in range(0x121): ea = start + idx * 0x40 print(f"[{hex(ea)}]: ") ins = idc.generate_disasm_line(ea, 0) if (ins.startswith("mov eax, 0FFFFFFFFh")): op1 = idc.print_operand(ea+0x0C, 1) if (op1[-1] == 'h'): op1 = int(op1[:-1], 16) else: op1 = int(op1) op2 = idc.print_operand(ea+0x17, 1) if (op2[-1] == 'h'): op2 = int(op2[:-1], 16) else: op2 = int(op2) op3 = idc.print_operand(ea+0x23, 1) if (op3[-1] == 'h'): op3 = int(op3[:-1], 16) else: op3 = int(op3) op4 = idc.print_operand(ea+0x2E, 1) if (op4[-1] == 'h'): op4 = int(op4[:-1], 16) else: op4 = int(op4) ins = (op1+17*op2, op3+17*op4) elif (ins.startswith("int 3")): ins = (-1, -1) print(ins) op_ls[idx] = ins print(op_ls)
在解析时发现除了上面正常的代码块，还有下面几种代码块
复制代码 隐藏代码""" int 3 add [ecx-51h], ebx mov eax, 1; mov dword ptr [eax], 39393939h add [ebp+28D5560Ah], ecx """
其中int 3触发0x80000003异常，由于该异常只能处理一次，所有遇到int 3的代码块会直接die掉
剩余3条指令会触发0xC0000005异常，该异常会进入right，输出正确信息
分析后可以知道本题其实是一道迷宫题，根据输入的flag决定走的路径，走到出口胜利
先找一下实际可到达的出口
复制代码 隐藏代码op_ls = [(11, 41), (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (193, 52), (7, 7), (216, 43), (116, 13), (120, 189), (82, 244), (12, 12), (8, 15), (-1, -1), (-1, -1), (72, 95), (233, 272), (211, 194), (-1, -1), (59, 230), (237, 89), (60, 190), (23, 23), (243, 232), 'add [ecx-51h], ebx', (207, 224), 'mov eax, 1', (31, 61), (151, 179), (12, 180), (-1, -1), (76, 147), (-1, -1), (153, 196), (279, 271), (-1, -1), (276, 7), (38, 38), (39, 39), (48, 171), (-1, -1), (236, 251), (16, 192), (-1, -1), (125, 165), (46, 46), (260, 27), (45, 3), (174, 190), (219, 92), (51, 51), (-1, -1), 'add [ebp+28D5560Ah], ecx', (54, 54), (280, 204), (20, 135), (57, 57), (58, 58), (59, 59), (60, 60), (223, 235), (113, 265), (55, 278), (87, 6), (19, 214), (100, 36), (-1, -1), (68, 68), (69, 69), (70, 70), (130, 24), (258, 44), (73, 73), (74, 74), (75, 75), (76, 76), (77, 77), (122, 240), (79, 79), (80, 80), (-1, -1), (67, 26), (83, 83), (117, 118), (85, 85), (-1, -1), (-1, -1), (106, 73), (89, 89), (-1, -1), (-1, -1), (119, 129), (93, 93), (85, 167), (-1, -1), (96, 96), (97, 97), (123, 225), (259, 173), (229, 226), (101, 101), (269, 68), (169, 182), (104, 104), (105, 105), (154, 50), (-1, -1), (108, 108), (23, 112), (140, 99), (111, 111), (210, 202), (113, 113), (274, 56), (-1, -1), (-1, -1), (261, 42), (118, 118), (32, 115), (267, 209), (121, 121), (122, 122), (123, 123), (231, 256), (125, 125), (126, 126), (57, 206), (145, 245), (129, 129), (130, 130), (131, 131), (-1, -1), (133, 133), (155, 162), (135, 135), (136, 136), (-1, -1), (-1, -1), (-1, -1), (140, 140), (78, 197), (134, 163), (200, 103), (71, 218), (185, 283), (-1, -1), (139, 34), (188, 104), (-1, -1), (150, 150), (151, 151), (102, 253), (246, 157), (154, 154), (155, 155), 'add [ebp+57h], ebp', (93, 255), (158, 158), (38, 144), (281, 286), (28, 146), (186, 285), (163, 163), (138, 174), (69, 37), (166, 166), (241, 111), (168, 168), (169, 169), (-1, -1), (171, 171), (58, 148), (173, 173), (205, 64), (175, 175), (176, 176), (177, 177), 'add ds:0F215EE7Ch[edi*8], ecx', (181, 75), (128, 264), (257, 270), (160, 176), (221, 175), (101, 141), (220, 47), (88, 91), (195, 114), (158, 247), (189, 189), (80, 142), (287, 133), (-1, -1), (14, 161), (242, 166), (195, 195), (196, 196), (197, 197), 'add [edx], edi', (131, 65), (200, 200), (190, 130), (199, 96), (183, 105), (204, 204), (-1, -1), (35, 74), (-1, -1), (168, 109), (209, 209), (210, 210), (-1, -1), (-1, -1), (213, 213), (239, 108), (215, 215), (-1, -1), (217, 217), (218, 218), (219, 219), (220, 220), (136, 10), (222, 222), (107, 266), (66, 273), (1, 21), (-1, -1), (227, 227), (228, 228), (263, 170), (5, 191), (62, 46), (232, 232), (-1, -1), (103, 36), (-1, -1), (236, 236), (184, 2), (-1, -1), (98, 137), (126, 277), (217, 250), (172, 228), (102, 70), (-1, -1), (245, 245), (246, 246), (17, 86), (248, 248), (104, 38), (83, 268), (39, 187), (270, 128), (253, 253), (22, 149), (4, 94), (256, 256), (257, 257), (222, 84), (215, 288), (260, 260), (-1, -1), (254, 248), (164, 132), (264, 264), (54, 262), (33, 9), (253, 18), (213, 203), (30, 97), (40, 227), (271, 271), (79, 127), (-1, -1), (274, 274), (131, 241), (212, 63), (77, 143), (-1, -1), (121, 110), (124, 150), (281, 281), (282, 282), (-1, -1), 'add edi, esp', (285, 285), (51, 29), (282, 208), (159, 177)] for i in range(0x121): if (type(op_ls[i]) != str): continue for j in range(0x121): if (type(op_ls[j]) == str): continue if (i in op_ls[j]): print(f"[{i}]: {op_ls[i]}") break
真出口在[27] mov eax, 1; mov dword ptr [eax], 39393939h
dfs走迷宫找出口记录路径
复制代码 隐藏代码def dfs(cur, path=[]): # print(cur, path) if (cur == 27): print(path) return elif (type(op_ls[cur]) == str): return l = op_ls[cur][0] if (l != -1 and l not in path): new_path = path.copy() new_path.append(cur) dfs(l, new_path) r = op_ls[cur][1] if (r != -1 and r not in path): new_path = path.copy() new_path.append(cur) dfs(r, new_path) dfs(0, [])
只有一条路，长度正好是17 * 8，把路径转换为flag
复制代码 隐藏代码path = [11, 82, 26, 224, 66, 100, 229, 263, 164, 174, 64, 6, 193, 161, 28, 61, 223, 266, 9, 13, 8, 43, 16, 72, 258, 84, 117, 42, 251, 187, 114, 56, 20, 230, 191, 287, 208, 109, 112, 202, 199, 65, 214, 239, 98, 225, 21, 237, 184, 141, 78, 240, 277, 143, 103, 182, 160, 286, 29, 179, 181, 270, 40, 48, 45, 165, 37, 276, 63, 55, 280, 124, 231, 62, 265, 262, 254, 22, 190, 142, 134, 162, 186, 88, 106, 50, 92, 119, 32, 147, 34, 153, 157, 255, 94, 167, 241, 250, 268, 203, 183, 221, 10, 120, 267, 18, 194, 242, 172, 148, 188, 247, 17, 272, 127, 206, 35, 279, 110, 99, 259, 288, 159, 144, 71, 24, 243, 102, 269, 30, 180, 128, 145, 185, 47, 27] last = 0 flag = "" for cur in path: if (cur == op_ls[last][0]): flag += "0" else: flag += "1" last = cur print(int(flag, 2).to_bytes(17)) # d3ctf{0ut_of_th3ForesT#}
最后得到题目flagd3ctf{0ut_of_th3ForesT#}
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