Packer

Challenge Description

Reverse this linux executable?

binary

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Solution

First download the given file. I used the file command to check the file type. The given file is a linux executable.

Next I run the application to check what its up to.

The given application prompts for password to unlock the file. Since, the challenge name is packer I just used the strings command and looked out for the keyword packer.

From the output of the strings command, we can see that the give file is packer using upx packer.

So I used the upx tool to decompress the given file. The command is upx -d out.

After unpacking the file, I opened the file with Cutter, to view the decompiled source code. In the main function, I found the hex encoded flag.

I used CyberChef to decode the hex string to get the flag.

Flag: picoCTF{U9X_UnP4ck1N6_B1n4Ri3S_e190c3f3}