General Skills 250: absolutely relative

Challenge

In a filesystem, everything is relative ¯_(ツ)_/¯. Can you find a way to get a flag from this program? You can find it in /problems/absolutely-relative_1_15eb86fcf5d05ec169cc417d24e02c87 on the shell server. Source.

Solution

They provide the source of absolutely-relative, it checks for a file named ./permission.txt with the contents yes.

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hxr@pico-2018-shell-1:~$ echo -n 'yes'  > permission.txt
hxr@pico-2018-shell-1:~$ /problems/absolutely-relative_1_15eb86fcf5d05ec169cc417d24e02c87/absolutely-relative
You have the write permissions.
picoCTF{3v3r1ng_1$_r3l3t1v3_a97be50e}

Flag