balenaOS device proxy tunnel

redirect all TCP traffic from balenaOS devices via an SSH tunnel to a SOCKS5 proxy, running on DigitalOcean or AWS/EC2

ToC

• overview
• generate keys
• cloud proxy server
• balenaCloud application
• test and verify
• troubleshooting

overview

The examples give below demonstrate how to forward/redirect all balenaOS traffic via a user provided proxy. In the specific instance, we use a SOCKS5 proxy, which we tunnel to over SSH on DigitalOcean and AWS/EC2 using public key authentication.

Configuration of the hostOS is done within a ~10MB container on the host network. This container interacts with the Supervisor API to configure the redsocks redirector. As well as configuring the redirector, the container optionally establishes a tunnel to a remote server via SSH, if a private key is provided.

The redirection on the host is performed by redsocks using iptables. Redsocks supports socks4, socks5, http-connect, and http-relay proxy types, and while in these examples we use socks5 (default), any supported proxy type can be deployed and used.

In our example, we do not enable proxy authentication, since we are already tunneling to it via SSH, however in case where such local tunneling may not be desirable, setting PROXY_LOGIN and PROXY_PASSWORD environment variables and omitting SSH_PRIVATE_KEY will not create a tunnel and assume direct communication with the proxy using provided proxy authentication credentials.

The general approach uses in this example is as follows:

• decide which cloud provider to use for hosting the proxy server (i.e. Digital Ocean or AWS)
• generate test SSH keys, using an appropriate format for the selected cloud provider
• deploy a proxy server using Terraform into the selected cloud provider
• create a balenaCloud application
• build and deploy a release
• provision a balenaOS device (e.g balenaFin, RaspberryPi, Intel NUC, etc.)
• test and verify
• destroy test resources to avoid unexpected billing

generate keys

generate SSH keys for proxy tunnel authentication

mkdir -p keys

EC

EC keys can be used with DigitalOcean servers

ssh_key_type=ed25519

ssh-keygen -o -a 100 -t "${ssh_key_type}" -f "keys/id_${ssh_key_type}" -C 'balena' -N ''

ssh_public_key="$(cat keys/id_ed25519.pub)"

ssh_private_key="$(cat keys/id_ed25519 | openssl base64 -A)"

RSA

used for AWS/EC2 since EC cryptography is not supported at the time of writing

ssh_key_type=rsa

ssh-keygen -t "${ssh_key_type}" -f "keys/id_${ssh_key_type}" -C 'balena' -N ''

ssh_public_key="$(cat keys/id_rsa.pub)"

ssh_private_key="$(cat keys/id_rsa | openssl base64 -A)"

cloud proxy server

deploy a proxy server into a desired cloud provider

DigitalOcean

deploy a DigitalOcean cloud proxy server using Terraform

create proxy server

export DO_TOKEN={{ digital-ocean-api-token }}

pushd terraform/digitalocean

terraform init

terraform plan -var "do_token=${DO_TOKEN}"  

terraform apply -var "do_token=${DO_TOKEN}"

proxy_ip="$(terraform output -json | jq -r .ipv4_address.value)"

ssh_user=root

popd

(finally) clean up resources

optionally destroy DigitalOcean Droplet after finishing with the PoC

pushd terraform/digitalocean

terraform destroy -var "do_token=${DO_TOKEN}"

popd

AWS/EC2

deploy a cloud proxy server into AWS/EC2 using Terraform

create proxy server

ensure your AWS credentials are configured correctly

pushd terraform/aws-ec2

terraform init

terraform plan -var "key_pair=${ssh_public_key}"

terraform apply -var "key_pair=${ssh_public_key}"

proxy_ip="$(terraform output -json | jq -r .instance_public_ip.value)"

ssh_user=ec2-user

popd

(finally) clean up resources

optionally destroy AWS/EC2 resources after finishing with the PoC

pushd terraform/aws-ec2

terraform destroy -var "key_pair=${ssh_public_key}"

popd

balenaCloud application

deploy balenaCloud application, which will configure balenaOS to proxy all traffic via your cloud proxy

build and deploy the app

once the app is created and the release is deployed, provision at least one balenaOS device into it

balena login

# to build to other architectures, also change ALPINE_ARCH in docker-compose.yml
arch=armv7l

device_type=fincm3

app_name=${device_type}-${arch}

balena app create ${app_name} --type ${device_type}

app_slug=$(balena app ${app_name} | grep SLUG | awk '{print $2}')

balena env add SSH_USER "${ssh_user}" --application ${app_slug}

balena env add SSH_KEY_TYPE "${ssh_key_type}" --application ${app_slug}

balena env add SSH_PRIVATE_KEY "${ssh_private_key}" --application ${app_slug}

balena env add PROXY_IP "${proxy_ip}" --application ${app_slug}

balena push ${app_slug}

test and verify

terminal into the hostOS container and verify all traffic is exiting via your proxy

DigitalOcean

echo 'curl -s https://ipinfo.io/org; exit' \
  | balena ssh $(balena devices --app ${app_name} -j | jq -r .[0].uuid)

=============================================================
	Welcome to balenaOS
=============================================================
AS14061 DigitalOcean, LLC

AWS/EC2

...

=============================================================
	Welcome to balenaOS
=============================================================
AS16509 Amazon.com, Inc.

troubleshooting

• test proxy connectivity bypassing redsocks redirector on the balenaOS device

curl -x socks5://127.0.0.1:1080 https://ipinfo.io/

• to temporarily restore access in the event of proxy connectivity issues, on the hostOS run the following

iptables -t nat -F OUTPUT
iptables -t nat -F PREROUTING
iptables -t nat -F REDSOCKS

---

Icon made by Freepik from www.flaticon.com.