50 points
Category: General Skills
Tags: #generalskills #git
I accidentally wrote the flag down. Good thing I deleted it! You download the challenge files here: challenge.zip
Unzipping the provided challenge.zip archive, we immediately see its a git repository with the presence of the .git folder.
$ unzip challenge.zip
Archive: challenge.zip
creating: drop-in/
creating: drop-in/.git/
creating: drop-in/.git/branches/
inflating: drop-in/.git/description
creating: drop-in/.git/hooks/
inflating: drop-in/.git/hooks/applypatch-msg.sample
inflating: drop-in/.git/hooks/commit-msg.sample
inflating: drop-in/.git/hooks/fsmonitor-watchman.sample
inflating: drop-in/.git/hooks/post-update.sample
inflating: drop-in/.git/hooks/pre-applypatch.sample
inflating: drop-in/.git/hooks/pre-commit.sample
inflating: drop-in/.git/hooks/pre-merge-commit.sample
inflating: drop-in/.git/hooks/pre-push.sample
inflating: drop-in/.git/hooks/pre-rebase.sample
inflating: drop-in/.git/hooks/pre-receive.sample
inflating: drop-in/.git/hooks/prepare-commit-msg.sample
inflating: drop-in/.git/hooks/update.sample
creating: drop-in/.git/info/
inflating: drop-in/.git/info/exclude
creating: drop-in/.git/refs/
creating: drop-in/.git/refs/heads/
extracting: drop-in/.git/refs/heads/master
creating: drop-in/.git/refs/tags/
extracting: drop-in/.git/HEAD
inflating: drop-in/.git/config
creating: drop-in/.git/objects/
creating: drop-in/.git/objects/pack/
creating: drop-in/.git/objects/info/
creating: drop-in/.git/objects/ba/
extracting: drop-in/.git/objects/ba/e247ddd9f730bb7a2a9425d4616b116bc7b07b
creating: drop-in/.git/objects/68/
extracting: drop-in/.git/objects/68/df36301019ecc05a65a4e87a754c83411ac925
creating: drop-in/.git/objects/87/
extracting: drop-in/.git/objects/87/b85d7dfb839b077678611280fa023d76e017b8
creating: drop-in/.git/objects/d5/
extracting: drop-in/.git/objects/d5/52d1ecd2d83fa2e65b6724d1ff73b45a7d59b7
creating: drop-in/.git/objects/0c/
extracting: drop-in/.git/objects/0c/1ab266b7a3a1cd099bb509f82b7a2d03aecd03
creating: drop-in/.git/objects/8d/
extracting: drop-in/.git/objects/8d/c51806c760dfdbb34b33a2008926d3d8e8ad49
inflating: drop-in/.git/index
extracting: drop-in/.git/COMMIT_EDITMSG
creating: drop-in/.git/logs/
inflating: drop-in/.git/logs/HEAD
creating: drop-in/.git/logs/refs/
creating: drop-in/.git/logs/refs/heads/
inflating: drop-in/.git/logs/refs/heads/master
extracting: drop-in/message.txt
Listing the contents of the unzipped folder and displaying the contents of the single message.txt file :
$ ls
message.txt
$ cat message.txt
TOP SECRET
Nothing of interest there, lets look at the commit history for any clues :
$ git log
commit 8dc51806c760dfdbb34b33a2008926d3d8e8ad49 (HEAD -> master)
Author: picoCTF <ops@picoctf.com>
Date: Tue Mar 12 00:06:17 2024 +0000
remove sensitive info
commit 87b85d7dfb839b077678611280fa023d76e017b8
Author: picoCTF <ops@picoctf.com>
Date: Tue Mar 12 00:06:17 2024 +0000
create flag
The commit message for the commit with hash 87b85d7 looks interesting, referencing the creation of a flag.
Let's check out this commit :
$ git checkout 87b85d7dfb839b077678611280fa023d76e017b8
Note: switching to '87b85d7dfb839b077678611280fa023d76e017b8'.
You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.
If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:
git switch -c <new-branch-name>
Or undo this operation with:
git switch -
Turn off this advice by setting config variable advice.detachedHead to false
HEAD is now at 87b85d7 create flag
Then again list the contents of the folder and file(s) reverted to by checking out this commit :
$ ls
message.txt
$ cat message.txt
picoCTF{...........redacted.............}
Where the actual flag value has been redacted for the purposes of this write up.
It's always worth paying attention to the challenge names, giving a clue to git commits.