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.Net zero base reverse tutorial -- Lesson 1 (reverse principle)

If you had learned to reverse or read the Shark zero based reverse tutorial before, you might have a kind of familiarity with my tutorial. I try to follow the Shark constant tutorial to write this series, so as to improve the readability and make it easier for you to go from OllyDbg to dnSpy. Due to some limitations, all the key words related to Poe in this series are replaced by reverse ones.


Start the zero base reverse graphic series.

Let me introduce this software. I wrote a simple software which is easy for beginners to learn and easy to understand.
The program needs to enter the correct account and password to login successfully, otherwise the login fails.
But we don't know the correct password. (also can be understood as other software registration codes).

Since he can prompt login success and login failure (or some software prompts registration error), it shows that he has a judgement that we will open the dnSpy-x86.exe, drag the reverse software into dnSpy, and make him judge that all characters are successful through modification.
(since it is a beginner's zero basic entry course, it does not involve "shell", "hidden pile" and so on) interfering with novice elements.

Right click on the top left corner window, select Edit > search assembly, enter "login failure" in the search box below, select "search digit / string", and find the result, we double-click the search results.

We can see that the code jumps to the judgment point. Compared with OllyDbg or x64Dbg, dnSpy directly shows us that the visual operation of source code is very humane. As long as you can read the.Net code slightly, you can complete the reverse process.

Now let's look at the code as follows:

When the button is pressed, if the content length of textBox1 (account) is -1, the prompt prompt box will be popped out, otherwise the prompt box of landing failure will be popped up.

But in fact, if you have contacted programming, you will find this is a wrong judgment, because when the edit box does not fill in the content, the content length is 0, and the length of the text is the length of the text. So its length will never be -1.

So now we have to change this judgment logic, so that it does not equal to -1, when the landing is successful, otherwise it will pop up the prompt box for landing failure.

Right click in the 21 row and choose Edit method.

Modify the judgment of the 13 elements so that it is not equal to -1.

Note: = = = equal, = = equal, the code, including punctuation, need to be input under the non Chinese input method.

When we edit it, we can click the compiler to see that the code has been changed as shown in the figure below.

Select File > Save > > determine

Finally, let's turn on the new program that we just saved (that is, our reverse procedure). Is it really reversed?
Any input, or no typing, will prompt the landing to be successful. Congratulations!

What about?
Now do I think the reverse is so simple?
Do you have confidence to go deep into reverse?

I have uploaded the small program for testing, and I also packed the dnSpy I used.
Let's try it downloading. You are already going against it!


Courseware: Https://articles.zsxq.com/id_ Ewgw2 Iagzngr.html


 
 

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  Computer courses for College Students
Article title:.Net zero base reverse tutorial -- Lesson 1 (reverse principle)
The writer: Mu Ruoxi
Date of publication: 2019-03-25 05:55 starts on Monday Mu Yue Xi blog
Fixed links: Https://www.muruoxi.com/jiaocheng/4031.html
 
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6 comments

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  1. 5 floor
    Wangcheng   

    I want to ask where the I address is under the landlord software.

    3:30 p.m. on March 20, 2020   comment
  2. 4 floor
    Interesting   

    Thank you.

    10:21 p.m. on January 4, 2020   comment
  3. floor
    Sunset glow   

    Shark Heng. Starting from his tutorial, he began to contact the reverse.

    9:00 p.m. on March 26, 2019   comment
  4. Bench
    Ammo   

    Yes, thank you for sharing.

    1:00 p.m. on March 26, 2019   comment
  5. Sofa
    Flying snow   

    Because I didn't install VS, I modified the C# program I wrote before, EMM. Just use this dnspy to decompile and revise it. This software is easy to use.

    10:34 p.m. on March 25, 2019   comment

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