picoCTF General Skills Guide

Blame Game

Name: Blame Game
Description: Someone's commits seems to be preventing the program from working. Who is it? You can download the challenge files here: challenge.zip
Author: Jeffery John
Tags: Easy, General Skills, picoCTF 2024, browser_webshell_solvable, git
Challenge from: picoCTF 2024
Files: challenge.zip
Hints:
1. In collaborative projects, many users can make many changes. How can you see the changes within one file?
2. Read the chapter on Git from the picoPrimer here.
3. You can use python3 <file>.py to try running the code, though you won't need to for this challenge.

Theory

According to the description, to get the flag I think we'll have to look through git log. And yeah that's kind of everything I think we have to do, but yeah, we'll use git log to view the history and the name of the author of the commit that ruined the file will be the flag probably:

git log

Solution

First we need to download the repository and unzip it:

shukularuni-picoctf@webshell:~$ wget https://artifacts.picoctf.net/c_titan/157/challenge.zip
--2025-04-11 00:50:04--  https://artifacts.picoctf.net/c_titan/157/challenge.zip
Resolving artifacts.picoctf.net (artifacts.picoctf.net)... 3.160.22.128, 3.160.22.16, 3.160.22.92, ...
Connecting to artifacts.picoctf.net (artifacts.picoctf.net)|3.160.22.128|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 293587 (287K) [application/octet-stream]
Saving to: 'challenge.zip'

challenge.zip                                                       100%[=================================================================================================================================================================>] 286.71K  --.-KB/s    in 0.1s    

2025-04-11 00:50:04 (1.92 MB/s) - 'challenge.zip' saved [293587/293587]

shukularuni-picoctf@webshell:~$ unzip challenge.zip

shukularuni-picoctf@webshell:~$ cd drop-in

shukularuni-picoctf@webshell:~/drop-in$ ls
message.py

shukularuni-picoctf@webshell:~/drop-in$ cat message.py
print("Hello, World!"

Bruh, whoever edited the file to remove that parenthesis and make the program not work must be a bad person, anyways, let's look through the history:

shukularuni-picoctf@webshell:~/drop-in$ git log
commit b7f1fb20f72e493f604ccb3b9f2639a00c566939 (HEAD -> master)
Author: picoCTF <ops@picoctf.com>
Date:   Tue Mar 12 00:07:08 2024 +0000

    important business work

commit c16a2576a68c7166d13f3e877ea4b4cfc675d343
Author: picoCTF <ops@picoctf.com>
Date:   Tue Mar 12 00:07:08 2024 +0000

    important business work

commit ec9b57cadceec5aecebd3319ba2be0430a56b3e3
Author: picoCTF <ops@picoctf.com>
Date:   Tue Mar 12 00:07:08 2024 +0000

    important business work

commit 343b68ee036b913155226d96423d130bed3974e3
Author: picoCTF <ops@picoctf.com>
Date:   Tue Mar 12 00:07:08 2024 +0000

    important business work

commit fbe16b1f2729cffbdbeeabe84f8a37407c7d4622
Author: picoCTF <ops@picoctf.com>
Date:   Tue Mar 12 00:07:08 2024 +0000

    important business work
...
...

Or maybe not, because there is a bajillion of commits in there, so I guess the next best option is to find the flag manually with grep. And because most of the commits are done by picoCTF, we'll have to search for the `{` too:

shukularuni-picoctf@webshell:~/drop-in$ git log | grep "picoCTF{"
Author: picoCTF{@sk_th3_1nt3rn_cfca95b2} <ops@picoctf.com>

There we go! That's the flag.

I rated this level as "good"! :3