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#. net zero basics reverse tutorial
If you've learned reverse before, or have seen it@Shark HengYou may have a cordial feeling towards the course I wrote. I try my best to copy shark Heng's "zero basis reverse graphics and text course" to write this series, so as to improve the readability and facilitate your transition from OllyDbg to dnspy.
Let's start learning~
Introduce this software, I write a simple software, convenient for beginners to learn, easy to understand.
The program needs to enter the correct account number and password to login successfully, otherwise the login fails.
But we don't know the correct password.(it can also be understood as other software registration codes)
Since he can prompt login success and login failure (or some software prompts registration code error), it shows that he has a judgment. Let's open dnspy-x86.exe, drag the software to be cracked into dnspy, and let him judge that all characters are successful through modification.
Because it is a primary zero foundation introductory course, it does not involve "various shells", "hidden piles" and other elements that interfere with novice
Right click the window in the upper left corner, select Edit > search assembly, enter "login failed" in the search box below, and select "number / string" to search. After finding the result, we double-click the search result.
We can see that the code jumps to the judgment point. Compared with OllyDbg or x64dbg, the visualization operation of dnspy that directly allows us to see the source code is very humanized. As long as you can read the. Net code slightly, you can complete the reverse process.
Now let's look at this code, as shown in the following figure:
After the button is pressed, if the content length of textbox1 (account number) is - 1, the prompt box of successful login will pop up; otherwise, the prompt box of login failure will pop up.
But in fact, if you have been exposed to programming, you will find that this is a wrong judgment, because when the edit box does not fill in the content, the content length is 0, and after filling in the text, the length is the text length.So its length will never be - 1.
Now, we need to change the judgment logic, so that when it is not equal to - 1, the login success will pop up, otherwise the login failure prompt box will pop up.
Right click on line 21 and select edit method
Modify the judgment of line 13 so that it is not equal to - 1
Note: = = is equal to,! = is not equal, code, including punctuation, should be input in non Chinese input method
After the modification, we can click compile to see that the code has been changed as shown in the figure below
Select File > save all > OK
Finally, let's open the new program saved just now (that is, the program we cracked). Is it really cracked?
Any input, or no text input, will prompt successful login, Congratulations, successful cracking!
Do you think cracking is so simple now?
Do you have the confidence to crack it in depth?
I have uploaded the small program to test the cracking, and I have packed the dnspy used.
Download and try it!You can crack it!
Get the courseware, reply Keywords:. net zero base reverse