Portainer and Mutual TLS (mTLS) through Docker Remote API
Prepare the certificates for your Docker Remote API
This command requires you to setup a passphrase.
# Preferably a DNS Name
HOST_INFO="localhost"
COUNTRY="CA"
STATE="Quebec"
LOCALITY="Montreal"
ORGANIZATION="Studio Webux"
OU="IT"
openssl genrsa -aes256 -out ca-key.pem 4096
openssl req -new -x509 -days 365 -key ca-key.pem -sha256 -out ca.pem \
-subj "/C=$COUNTRY/ST=$STATE/L=$LOCALITY/O=$ORGANIZATION/OU=$OU/CN=$HOST_INFO"
openssl genrsa -out server-key.pem 4096
openssl req -subj "/CN=$HOST_INFO" -sha256 -new -key server-key.pem -out server.csr
echo subjectAltName = DNS:$HOST_INFO,IP:127.0.0.1 >> extfile.cnf
echo extendedKeyUsage = serverAuth >> extfile.cnf
openssl x509 -req -days 365 -sha256 -in server.csr -CA ca.pem -CAkey ca-key.pem \
-CAcreateserial -out server-cert.pem -extfile extfile.cnf
openssl genrsa -out key.pem 4096
openssl req -subj '/CN=client' -new -key key.pem -out client.csr
echo extendedKeyUsage = clientAuth > extfile-client.cnf
openssl x509 -req -days 365 -sha256 -in client.csr -CA ca.pem -CAkey ca-key.pem \
-CAcreateserial -out cert.pem -extfile extfile-client.cnf
rm -v client.csr server.csr extfile.cnf extfile-client.cnf
chmod -v 0400 ca-key.pem key.pem server-key.pem
chmod -v 0444 ca.pem server-cert.pem cert.pem
Copy the file for the Docker Remote API
sudo mkdir -p /var/ssl
sudo cp ca.pem server-cert.pem server-key.pem /var/ssl/
Configure and Restart Docker Service
sed -i 's|ExecStart=/usr/bin/dockerd -H fd://|& --tlsverify --tlscacert=/var/ssl/ca.pem --tlscert=/var/ssl/server-cert.pem --tlskey=/var/ssl/server-key.pem -H 0.0.0.0:2376|' /lib/systemd/system/docker.service
cat /lib/systemd/system/docker.service
Expected line:
ExecStart=/usr/bin/dockerd -H fd:// --tlsverify --tlscacert=/var/ssl/ca.pem --tlscert=/var/ssl/server-cert.pem --tlskey=/var/ssl/server-key.pem -H 0.0.0.0:2376 --containerd=/run/containerd/containerd.sock
sudo systemctl daemon-reload
sudo systemctl restart docker
Don't forget to setup your firewall properly. The port is
2376
Setup Portainer
The hostname must match the $HOST_INFO from above, and the port to use is 2376
- Using the Web UI, you can create a new environment.
- Enable the TLS
- Select the CA Certificate :
ca.pem - Select the Client Certificate :
cert.pem - Select the Client Key :
key.pem
At this point you should be able to connect to the remote Docker API