Do I Bleed?
Exploitation
100-200 points
Network services are tricky things to build, especially when trusting user input. We found this service running that is having trouble with basic math. Could you help it with some answers? Maybe it'll provide a lengthy flag!
Try at f80ac865e59fcd25817722efd0225048.bsides.40bytectf.com:22380
Flag: 40ByteCTF{1_c@n-h4z=Th3_m3M0rI3s?}
Getting running
# Install rustup
sudo apt-get install build-essential software-properties-common -y
curl https://sh.rustup.rs -sSf | sh
rustup default nightly
# build and generate md5sum for dns and client binary
cd doibleed/
cargo build --release
strip target/release/doibleed
md5sum ./target/release/doibleed
cp ./target/release/doibleed ~/doibleed-noflag
# Build executable
cargo build --release --features=real_flag
# add user
useradd -m -U doibleed -s /bin/false
# copy binary to directory
cp ./target/release/doibleed /home/doibleed/
chown doibleed:doibleed /home/doibleed/doibleed/
chmod 540 /home/doibleed/doibleed- Add systemd service
/etc/systemd/system/doibleed.service[Unit] Description=Executes DoIBleed CTF challenge Wants=network.target After=network.target [Service] User=doibleed Group=doibleed WorkingDirectory=~ ExecStart=/home/doibleed/doibleed Restart=always RestartSec=10 [Install] WantedBy=multi-user.target - Start and enable
sudo systemctl start doibleed sudo systemctl enable doibleed