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Drop tmate for ngrok and Tor; add collaboration
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Tmate did not adequately support the necessary features of tmux
required for session groups that would allow proper collaboration.
Instead we use ttyd and/or an SSH server with an actual tmux
process configured the way we need.

For more information on the shortcomings of tmate in this
particular case, see (among others):
tmate-io/tmate#49
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@jstrieb
jstrieb committed Dec 23, 2020
1 parent 4a0d29c commit 47148f0
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1 change: 0 additions & 1 deletion .github/workflows/run-server-graphical.yml
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Expand Up @@ -135,7 +135,6 @@ jobs:
sudo systemctl enable xrdp

- name: Install ngrok
if: ${{ github.event.inputs.ngrok_token }}
run: |
cd
wget \
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187 changes: 129 additions & 58 deletions .github/workflows/run-server.yml
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Expand Up @@ -13,13 +13,8 @@ name: Run Collaborative CTF Environment
on:
workflow_dispatch:
inputs:
# tmate login info is sent to this webhook if it is entered. This is
# useful because sometimes the GitHub Actions view does not correctly
# show the printed output from the Action while it is running, and if you
# can't see the tmate URL, you can't ssh in. I usually use webhook.site
# to easily create a temporary receiving webhook
webhook_url:
description: Webhook URL (e.g. from https://webhook.site)
ngrok_token:
description: Token to use for ngrok (optional)
required: false

jobs:
Expand All @@ -46,7 +41,6 @@ jobs:
nmap
htop
gdb
tor
netcat
socat
build-essential
Expand All @@ -69,6 +63,7 @@ jobs:
)
python3 -m pip install --upgrade ${PIP_PACKAGES[@]}


# Make CTF files from the repo available in the ~/ctf directory
- uses: actions/checkout@v2
- name: Move checked out repository to ~/ctf
Expand All @@ -80,67 +75,143 @@ jobs:
# in a folder that doesn't exist and immediately fail
mkdir --parents "$GITHUB_WORKSPACE"


- name: Install dotfiles
run: |
cd ~/ctf/dotfiles
bash install.sh
cp ~/.tmux.conf ~/.tmate.conf

# Install tmate this way instead of using aptitude because the latest
# version doesn't yet seem available
- name: Install tmate (reverse shell)
cp ./ttyd_run.sh ~/ttyd_run.sh
cp ./ngrok.yml ~/ngrok.yml

# Change the runner password to "ctf"; by default it has no password,
# which complicates some things like connecting via SSH
echo "runner:ctf" | sudo chpasswd

# Add a command to kill the action by killing the "sleep" process
echo 'alias quit="pkill sleep"' >> ~/.bashrc


- name: Install ngrok and run in the background as a daemon
run: |
# Only proceed if there is a user-supplied authtoken for ngrok.
# Prefer one submitted with a workflow dispatch, but accept one
# stored as a repository secret.
NGROK_AUTHTOKEN="${{ github.event.inputs.ngrok_token }}"
if [ -z "$NGROK_AUTHTOKEN" ]; then
NGROK_AUTHTOKEN="${{ secrets.NGROK_TOKEN }}"
fi
if [ -z "$NGROK_AUTHTOKEN" ]; then
exit 0
fi

# Add the authtoken to the ngrok configuration file
echo "authtoken: $NGROK_AUTHTOKEN" >> ~/ngrok.yml

# Download and install ngrok
cd
wget \
--output-document ngrok.zip \
"https://bin.equinox.io/c/4VmDzA7iaHb/ngrok-stable-linux-amd64.zip"
unzip ngrok.zip
sudo mv ngrok /usr/local/bin/ngrok
touch ~/ngrok.log

# Run ngrok in the background as a daemon
start-stop-daemon \
--start \
--background \
--chdir ~/ctf \
--exec /usr/local/bin/ngrok \
-- \
start \
-config ~/ngrok.yml \
ttyd ssh


- name: Install ttyd and run in the background as a daemon
run: |
# xterm is required for a tmux/tmate tty. Included here rather than
# the install section above to make clear that this is a specific
# requirement for running tmate on this platform, even though other
# stuff probably uses xterm anyway.
# xterm is required for tmux\ttyd. Installed here to highlight that
# this is the specific part of the script that requires it.
sudo apt-get --yes install xterm

# tmate requires ssh keys, but it doesn't matter what they are. This
# generates them without a passcode and puts them in the usual
# location. The flags are the minimum such that there is no
# interactive prompt.
ssh-keygen -f ~/.ssh/id_rsa -N ""

# Download and install ttyd
cd
wget \
--output-document "tmate.tar.xz" \
"https://github.com/tmate-io/tmate/releases/download/2.4.0/tmate-2.4.0-static-linux-amd64.tar.xz"
tar \
--extract \
--verbose \
--file "tmate.tar.xz"

# Add a "quit" command that kills the tmate session, thereby ending
# the Action cleanly, without errors
echo 'alias quit="pkill tmate"' >> ~/.bashrc

# Run tmate in the background from the ctf repository folder, but give
# it some time to start. Done this way so we can both see tmate login
# info, and send the info to the webhook, both of which can only be
# done after it starts up.
- name: Run tmate; send login info via a webhook if applicable
--output-document ttyd \
"https://github.com/tsl0922/ttyd/releases/download/1.6.1/ttyd_linux.x86_64"
chmod +x ttyd
sudo mv ttyd /usr/local/bin/ttyd

# Run ttyd in the background as a daemon
start-stop-daemon \
--start \
--background \
--chdir ~/ctf \
--exec /usr/local/bin/ttyd \
-- \
--port 7681 \
--credential runner:ctf \
/bin/bash ~/ttyd_run.sh


- name: Install Tor and run a hidden service in the background as a daemon
run: |
sudo apt-get --yes install tor

# Sometimes it's already running for some reason...?
sudo service tor stop
sudo killall tor || true

# Run a hidden service in the background as a daemon -- allow
# connecting to the ttyd instance via a browser and allow SSH
tor \
--runasdaemon 1 \
--hiddenservicedir /home/runner/tor_service \
--hiddenserviceport "80 127.0.0.1:7681" \
--hiddenserviceport "22 127.0.0.1:22"


- name: Display connection information
run: |
# Required to use fg for jobs sent to the background - for some
# reason bash doesn't have job control enabled by default???
set -m

cd ~/ctf
~/tmate-2.4.0-static-linux-amd64/tmate -F > ~/tmate_info.txt &
sleep 5

# Print to stdout *and* send to a webhook
cat ~/tmate_info.txt
curl \
--request POST \
--header "Content-Type: text/plain" \
--data @/home/runner/tmate_info.txt \
${{ github.event.inputs.webhook_url }} \
|| true

# Bring tmate back to the foreground so the Action only ends when
# tmate is closed
fg
# Start a tmux session in the background whose window group everyone
# will share
tmux new-session -d -s ctf

echo Waiting for things to start up...
sleep 20s

echo
echo When connecting, use username "'runner'" and password "'ctf'"
echo

# Print Tor connection info
echo To connect securely over Tor:
printf "http://%s\n" "$(cat ~/tor_service/hostname)"
printf \
"ssh -o ProxyCommand='nc -x localhost:9150 %%h %%p' ssh://runner@%s\n\n" \
"$(cat ~/tor_service/hostname)"

# Print ngrok connection info (if applicable)
NGROK_AUTHTOKEN="${{ github.event.inputs.ngrok_token }}"
if [ -z "$NGROK_AUTHTOKEN" ]; then
NGROK_AUTHTOKEN="${{ secrets.NGROK_TOKEN }}"
fi
if [ -n "$NGROK_AUTHTOKEN" ]; then
echo "To connect using ngrok (i.e., not Tor):"
cat ~/ngrok.log \
| jq .url \
| grep -v "null" \
| tr -d '"' \
| sed 's/tcp:\/\/\(.*\)/ssh ssh:\/\/runner@\1/g' \
| sort
fi

# Wait... This process will be killed to end the Action. Return a
# non-failure exit code in any case so that there are no unnecessary
# notifications about a failed Actions workflow.
sleep 6h || true


- name: Clean up
run: |
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4 changes: 4 additions & 0 deletions dotfiles/.bashrc
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Expand Up @@ -25,3 +25,7 @@ alias sl="ls"
alias webserver="python3 -m http.server 8080 &> /dev/null &"
alias backup-website="wget --mirror --convert-links --adjust-extension --page-requisites --no-parent"
alias latest="ls -rt | tail"

if [ -n "$SSH_CONNECTION" ] && [ -z "$TMUX" ]; then
/bin/bash /home/runner/ttyd_run.sh
fi
13 changes: 13 additions & 0 deletions dotfiles/ngrok.yml
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@@ -0,0 +1,13 @@
console_ui: false
log: /home/runner/ngrok.log
log_format: json
web_addr: false
tunnels:
ttyd:
proto: http
addr: 7681
inspect: false
ssh:
proto: tcp
addr: 22
inspect: false
2 changes: 2 additions & 0 deletions dotfiles/ttyd_run.sh
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@@ -0,0 +1,2 @@
# Create a new tmux session with a randomized identifier
cd ~/ctf && tmux new-session -s "ctf""$(date +%s | sed "s/\(.\)/\1\n/g" | head -n -1 | shuf | tail -n 6 | tr -d "\n")" -t ctf

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