Problem-solving process
The exe file title given dragged ida, view the main function.
Logical analysis functions, the user needs to output a character string stored in the variable v9. If the value of the value unk_413e90 v9 v5 is equal to the value is printed, or print the value of aFlag_0.
See the value of two outputs:
You can see if you enter the correct words will print flag get, indicating that the flag is stored in v5.
View value v5 and found no value:
Closer look main function found on line 10 has a storage operation, the stored value to a variable in v5. V5 value is in the process of implementation of the main function was only passed, and therefore can not find the value before you can understand.
Xmmword find the value stored in the variable:
The value of the variable can be converted to ascii code, also found qword variables can also be converted to ascii.
Is the string value reverse flag:
DUTCTF{We1c0met0DUTCTF}
to sum up
This is a simple inverse problem, just know that stored functions related to the topic, this topic solved.
There is a point to note is the value of the last flag is given in reverse order, which is affected by the storage method. Specifically understand the difference between big endian and little-endian memory storage.