[Webhacking] php7cmp4re

• Problem path
• Problem information
• Problem solving

 

 

 

[Problem path]

https://dreamhack.io/wargame/challenges/1113

php7cmp4re

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[Problem information]

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[Problem solving]

1. First, I accessed the web server. There was a page where you can get input1 and input2.

 

 

2. Second, I downloaded the problem file. There were three php files in it. When I checked the code, the check.php file  specified the conditions of input1 and input2.

 

 

3. It seems that the flag is echoed only when both input1 and input2 conditions are suitable. The conditions are summarized in the following table.

Input	Length	Size
input_1	input_1 < 4	input_1 < "8" && input_1 < "7.A" && input_1 > "7.9"
input_2	input_2 < 3 && input_2 > 1	input_2 < 74 && input_2 > "74"

 

Looking at input1, I guessed that it was an ASCII code value because it was compared with the letters "8", "7.A", and "7.9". Therefore, referring to the ASCII code table, it was confirmed that the number of characters ranging from 

7.: to 7.@, which is larger than the letter 9 and smaller than the letter A, and has less than 4 characters, can be put into input1. It has been confirmed that input2 can contain numbers ranging from 7: to 7~, which are 2 characters and larger 

than the letter 4 and smaller than the number 4.

 

 

4. I simply put in the input value according to the conditions.

 

The flag was derived as follows.