再记一次经典Net程序的逆向过程

1.前言

上次发完，有网友问了一个问题：如果不绕过编译，而是直接编译怎么办？

记一次Net软件逆向的过程：https://www.cnblogs.com/dotnetcrazy/p/10142315.html

今天就来说说：本次提供样本：链接: https://pan.baidu.com/s/1ekYVKXt_Jz3ShwjoFknW0g 提取码: ywf6

2.调试破解

1.查壳知道是Net程序

2.dnspy打开发现乱码

3.de4dot脱壳

4.这个就是反混淆之后的程序

5.改名后重新打开就不乱码了

6.直接运行看看效果，找到提示信息

7.入口点下断

8.单步走一波

9.在疑似关键函数处下断，然后运行

10.单步走了几下发现到动态加载的dll文件中了

11.在疑是关键点前后下断，然后F11，跟进去看看

12.到达了Login的页面

13.尝试根据提示来搜索login里面的验证code（这个和上次讲的不一样，上次高度封装，这个很乱）

14.发现这段验证是在名称叫ok的按钮click事件中

15.发现有一段比较，下断，然后把text4的值改成right的值，看看什么效果

16.发现还有一处比较，不管的话运行依旧失败

17.看到一个vipdata转成datatime，那推测是和时间有关的

18.在loginfrom中搜索this.vipdate，发现了这处，那么可以确定是时间格式的字符串了（依据：可以转时间，而且可以使用字符串拼接）

19.设断然后单击调试

20.调试过程中修改值

21.再修改下vipdata

22.发现成功了

那么下面就是编译修改了

3.编译修改

1.编辑方法

2.修改完发现不能编译

PS：这就是为啥我名字写经典逆向的原因了（解决这个问题就解决了90%的Net逆向问题）

3.发现dnspy不能正确识别命名空间，而且代码太lou没法变相绕过（没有高度封装）

4.没关系，我们自己扒dll

5.把资源文件保存成一个个dll，找到我们需要的dll

6.那怎么知道dll的真实名字呢？其实也很简单，拖进Reflector就知道了

6.1.为了稳妥，我把Tianaya.x的dll都保存了（省得折腾）

7.重新运行后再编译，发现uploadxx.dll的某个方法不能识别

PS：其实你在uploadxx.dll里面搜一下就知道没有这个方法了，然后理想Net里面只有导入命名空间的方法才可以简写

8.其实你根据using的命令空间，或者去upload里面看都是没有Module1的，真正的命名空间是MyLibrary

9.这段可以删掉

10.发现已经修改好了，那么保存一下

11.只要这个放在原文件的根目录下就可以破解了（如果遇到不能破解的，可以用上次我讲的修改资源文件的方法）

4.小小验证

贴一个GIF结束

附录

贴一下我的ok_click：

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Runtime.CompilerServices;
using System.Text.RegularExpressions;
using System.Threading;
using System.Web;
using System.Windows.Forms;
using System.Xml;
using Microsoft.VisualBasic;
using Microsoft.VisualBasic.CompilerServices;
using Microsoft.Win32;
using Tianya.Data.SQLite;
using Tianya.MyLibrary;
using Tianya.UpLoadClient.My;

namespace Tianya.UpLoadClient
{
	// Token: 0x02000061 RID: 97
	[DesignerGenerated]
	public partial class LoginForm : Form
	{
		// Token: 0x06000CD4 RID: 3284 RVA: 0x000BA510 File Offset: 0x000B8910
		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
		private void OK_Click(object sender, EventArgs e)
		{
			try
			{
				this.Timer1.Enabled = false;
				this.OK.Enabled = false;
				string text = this.txtUsername.Text.Trim();
				string text2 = this.txtPassword.Text.Trim();
				if (text.Length < 1 | text2.Length < 1)
				{
					MessageBox.Show("請您輸入帳號密碼", "親愛的用戶", MessageBoxButtons.OK, MessageBoxIcon.Hand);
				}
				else
				{
					try
					{
						this.StrMacip = ClassGetRegCodeMD5.GetRegCodeMD5(16);
					}
					catch (Exception ex)
					{
						aModuleMain.MsgBox(ex.Message + "~Macip");
						return;
					}
					if (Operators.CompareString(this.StrMacip, "", false) == 0)
					{
						aModuleMain.MsgBox("系统异常");
					}
					else
					{
						this.Addlog("正在登入中...");
						string str = Conversions.ToString(Operators.ConcatenateObject("txtUserName=" + this.txtUsername.Text.Trim() + "&txtPassword=" + this.txtPassword.Text.Trim() + "&macip=" + this.StrMacip + "&logintime=" + HttpUtility.UrlEncode(Conversions.ToString(DateAndTime.Now)) + "&model=" + Conversions.ToString((int)aModuleMain.AppWebsite) + "&appname=" + this.appname + "&ComputerInfo=", NewLateBinding.LateGet(null, typeof(HttpUtility), "UrlEncode", new object[]
						{
							RuntimeHelpers.GetObjectValue(this.GetMyComputerInfo())
						}, null, null, null)));
						string right = Conversions.ToString(Conversion.Int(Conversions.ToDouble(Strings.Left(Conversions.ToString(this.strToAsc(this.txtUsername.Text.ToString().Trim())), 6)) + Conversion.Int(Conversions.ToDouble(Strings.Left(Conversions.ToString(this.strToAsc(this.txtPassword.Text.ToString().Trim())), 4))) * Conversion.Int(Conversions.ToDouble(Strings.Left(Conversions.ToString(this.strToAsc(Strings.Replace(Strings.Replace(this.StrMacip, ":", "", 1, -1, CompareMethod.Binary), ".", "", 1, -1, CompareMethod.Binary))), 5)))));
						int num = 1;
						checked
						{
							string text3;
							for (;;)
							{
								string getText = "/yahooreg/loginClient.aspx?" + str;
								text3 = Conversions.ToString(this.loginGeturl(getText, num, 30));
								if (text3.Trim().Length < 1)
								{
									break;
								}
								int num2 = Strings.InStr(text3, "</root>", CompareMethod.Binary);
								if (num2 > 0 && Operators.CompareString(Strings.Right(text3, "</root>".Length), "</root>", false) != 0)
								{
									num2 += "</root>".Length;
									text3 = Strings.Left(text3, num2);
								}
								string text4 = "";
								try
								{
									text4 = Regex.Match(text3, "\\[(?<v>[^\\[\\]{}]+)\\]").Groups["v"].Value.Trim();
									this.vipdate = Regex.Match(text3, "\\{(?<v>[^\\[\\]{}]+)\\}").Groups["v"].Value.Trim();
									XmlDocument xmlDocument = new XmlDocument();
									xmlDocument.LoadXml(text3);
									XmlNode xmlNode = xmlDocument.SelectSingleNode("root");
									if (xmlNode.HasChildNodes & xmlNode.ChildNodes.Count > 2)
									{
										try
										{
											foreach (object obj in xmlNode.ChildNodes)
											{
												XmlElement xmlElement = (XmlElement)obj;
												if (Operators.CompareString(xmlElement.Name, "sid", false) == 0)
												{
													text4 = xmlElement.InnerText.Trim();
												}
												else if (Operators.CompareString(xmlElement.Name, "vipdate", false) == 0)
												{
													this.vipdate = xmlElement.InnerText.Trim();
												}
											}
										}
										finally
										{
											 // delete
										}
									}
								}
								catch (Exception ex2)
								{
									if (num < 3)
									{
										num++;
										continue;
									}
									aModuleMain.MsgBox(ex2.Message + "~xml");
								}
								goto IL_439;
							}
							aModuleMain.MsgBox("網絡連接失敗");
							return;
							IL_439:
							if (text3.Contains("帐号已過期"))
							{
								this.Addlog("帐号已過期,請您續費後使用");
								this.TabControl1.SelectedTab = this.TabPage自助充值繳費;
							}
							else
							{
								string text4 = right; // add
								this.vipdate = "2029-10-01"; // add
								if (text4.Length > 0 && Operators.CompareString(text4, right, false) == 0)
								{
									if (Operators.CompareString(this.vipdate, "", false) == 0)
									{
										aModuleMain.MsgBox("登入出错");
										return;
									}
									DateTime date = DateAndTime.Now.AddYears(-1);
									DateTime.TryParse(this.vipdate, out date);
									int num3 = (int)DateAndTime.DateDiff(DateInterval.Second, date, DateAndTime.Now, FirstDayOfWeek.Sunday, FirstWeekOfYear.Jan1);
									if (num3 > 0)
									{
										aModuleMain.MsgBox("程序已到期,請續費後再使用" + Conversions.ToString(num3));
										this.TabControl1.SelectedTab = this.TabPage自助充值繳費;
										return;
									}
									Thread thread = new Thread(delegate()
									{
										try
										{
											string setting = Interaction.GetSetting(Application.StartupPath, "cache", "time", "");
											bool flag = true;
											if (!string.IsNullOrEmpty(setting))
											{
												DateTime now = DateAndTime.Now;
												DateTime.TryParse(setting, out now);
												if (DateAndTime.DateDiff(DateInterval.Day, now, DateAndTime.Now, FirstDayOfWeek.Sunday, FirstWeekOfYear.Jan1) <= 0L)
												{
													flag = false;
												}
											}
											if (flag)
											{
												string text5 = Application.StartupPath + "\\Cache";
												this.Addlog("正在清理緩存..." + text5.Replace(Application.StartupPath, ""));
												ClassMy.DelOldFile(text5, "", 30);
												text5 = Application.StartupPath + "\\upload";
												this.Addlog("正在清理緩存..." + text5.Replace(Application.StartupPath, ""));
												ClassMy.DelOldFile(text5, "", 30);
												text5 = Application.StartupPath + "\\test\\login";
												this.Addlog("正在清理緩存..." + text5.Replace(Application.StartupPath, ""));
												ClassMy.DelOldFile(text5, "", 30);
												text5 = Application.StartupPath + "\\test\\ThumbnailImage";
												this.Addlog("正在清理緩存..." + text5.Replace(Application.StartupPath, ""));
												ClassMy.DelOldFile(text5, "", 30);
												text5 = Application.StartupPath + "\\test\\" + Application.ProductName;
												this.Addlog("正在清理緩存..." + text5.Replace(Application.StartupPath, ""));
												ClassMy.DelOldFile(text5, "", 30);
												Interaction.SaveSetting(Application.StartupPath, "cache", "time", DateAndTime.Now.ToString("s"));
											}
											this.Addlog("正在優化數據庫...");
											 // update
											MySQLiteCreateFile.Create(Tianya.MyLibrary.Module1.dbfile, LoginForm.ds);
											this.Addlog("正在備份數據庫...");
											// update
											ClassMy.DBBackup(Tianya.MyLibrary.Module1.dbname, Tianya.MyLibrary.Module1.dbfile, delegate(string n)
											{
												this.Addlog("正在備份數據庫 " + n);
											});
										}
										catch (Exception ex4)
										{
											aModuleMain.MsgBox(ex4.Message + "~2");
										}
									});
									Thread thread2 = thread;
									thread2.IsBackground = true;
									thread2.Start();
									while (thread2.IsAlive)
									{
										Application.DoEvents();
										Thread.Sleep(1);
									}
									LoginForm.IsLoginSucceeded = true;
									this.Addlog("登入成功,正在启动中...");
									this.Visible = false;
									this.checkmacip();
									this.checkUpdate(false);
									this.ShowNotifyIcon1(this.NotifyIcon1);
									aModuleMain.LoginFormvipdate = this.vipdate;
									aModuleMain.LoginFormtxtUsername = this.txtUsername.Text.Trim();
									aModuleMain.LoginFormtxtPassword = this.txtPassword.Text.Trim();
									LoginForm.MethodInvoker1();
									SystemEvents.PowerModeChanged += this.PowerModeChanged;
									this.Addlog("登入 - " + MyProject.Application.Info.AssemblyName);
								}
								else if (Strings.InStr(text3, "帐号或密码不正确", CompareMethod.Binary) > 0 | Strings.InStr(text3, "资料不正确", CompareMethod.Binary) > 0)
								{
									this.TabControl1.SelectedIndex = 0;
									this.Addlog("帐号或密码不正确");
								}
								else if (Strings.InStr(text3, "帐号未激活", CompareMethod.Binary) > 0)
								{
									this.TabControl1.SelectedIndex = 0;
									this.Addlog("帐号已注册未激活,请联系提供者");
								}
								else
								{
									this.TabControl1.SelectedIndex = 0;
									this.Addlog("登入失败,请稍后重试");
								}
								this.formSaveSetting();
							}
						}
					}
				}
			}
			catch (Exception ex3)
			{
				aModuleMain.MsgBox(ex3.Message + "~login");
			}
			finally
			{
				this.OK.Enabled = !LoginForm.IsLoginSucceeded;
			}
		}
	}
}