Firmware

How often do we update our firm anyway? Hehe

Router firmware is a nice target to start your bug hunting journey. But you have to first understand how the firmware is loaded.

There is always a file in the firmware image that tells the router what services to start. Find this file.

MD5 (firmware.img.gz) = 488d36e3855f16972adec9067ca6deb2

Author: daniellimws

There are TWO ways to solve this challenge, and we will show both!

Solution 1

For this challenge, we were given an .img file, so the first this we did was open it with 7zip, and took a look inside. We noticed there was a bunch of folders inside and so we extracted it.

Given the challenge description, it gave us a hint on where to look for! In this case, it is the /etc/inittab. The inittab tells the router what processes to start, and what actions to take when it starts!

Looking inside that folder, we found the flag!!

flag!!

Flag: grey{inittab_1s_4n_1mp0rt4nt_p14c3_t0_100k_4t_wh3n_r3v3rs1ng_f1rmw4r3}

Solution 2

After extracting the folders out, we can run a PowerShell command that recursively search/find a string it directories, subdirectories and files!

Get-ChildItem -Path PATH_TO_YOUR_DIRECTORY -recurse 
| Select-String -Pattern "grey"

PowerShell command

Flag: grey{inittab_1s_4n_1mp0rt4nt_p14c3_t0_100k_4t_wh3n_r3v3rs1ng_f1rmw4r3}

Who updates their firmware anyway? Ain't nobody got time for that! 🐧