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216 lines
8.2 KiB
Markdown
216 lines
8.2 KiB
Markdown
<!--[metadata]>
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+++
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aliases = ["/engine/articles/https/"]
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title = "Protect the Docker daemon socket"
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description = "How to setup and run Docker with HTTPS"
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keywords = ["docker, docs, article, example, https, daemon, tls, ca, certificate"]
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[menu.main]
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parent = "smn_secure_docker"
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+++
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<![end-metadata]-->
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# Protect the Docker daemon socket
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By default, Docker runs via a non-networked Unix socket. It can also
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optionally communicate using an HTTP socket.
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If you need Docker to be reachable via the network in a safe manner, you can
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enable TLS by specifying the `tlsverify` flag and pointing Docker's
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`tlscacert` flag to a trusted CA certificate.
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In the daemon mode, it will only allow connections from clients
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authenticated by a certificate signed by that CA. In the client mode,
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it will only connect to servers with a certificate signed by that CA.
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> **Warning**:
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> Using TLS and managing a CA is an advanced topic. Please familiarize yourself
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> with OpenSSL, x509 and TLS before using it in production.
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> **Warning**:
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> These TLS commands will only generate a working set of certificates on Linux.
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> Mac OS X comes with a version of OpenSSL that is incompatible with the
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> certificates that Docker requires.
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## Create a CA, server and client keys with OpenSSL
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> **Note**: replace all instances of `$HOST` in the following example with the
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> DNS name of your Docker daemon's host.
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First generate CA private and public keys:
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$ openssl genrsa -aes256 -out ca-key.pem 4096
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Generating RSA private key, 4096 bit long modulus
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............................................................................................................................................................................................++
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........++
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e is 65537 (0x10001)
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Enter pass phrase for ca-key.pem:
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Verifying - Enter pass phrase for ca-key.pem:
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$ openssl req -new -x509 -days 365 -key ca-key.pem -sha256 -out ca.pem
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Enter pass phrase for ca-key.pem:
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You are about to be asked to enter information that will be incorporated
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into your certificate request.
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What you are about to enter is what is called a Distinguished Name or a DN.
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There are quite a few fields but you can leave some blank
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For some fields there will be a default value,
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If you enter '.', the field will be left blank.
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-----
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Country Name (2 letter code) [AU]:
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State or Province Name (full name) [Some-State]:Queensland
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Locality Name (eg, city) []:Brisbane
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Organization Name (eg, company) [Internet Widgits Pty Ltd]:Docker Inc
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Organizational Unit Name (eg, section) []:Sales
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Common Name (e.g. server FQDN or YOUR name) []:$HOST
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Email Address []:Sven@home.org.au
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Now that we have a CA, you can create a server key and certificate
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signing request (CSR). Make sure that "Common Name" (i.e., server FQDN or YOUR
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name) matches the hostname you will use to connect to Docker:
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> **Note**: replace all instances of `$HOST` in the following example with the
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> DNS name of your Docker daemon's host.
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$ openssl genrsa -out server-key.pem 4096
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Generating RSA private key, 4096 bit long modulus
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.....................................................................++
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.................................................................................................++
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e is 65537 (0x10001)
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$ openssl req -subj "/CN=$HOST" -sha256 -new -key server-key.pem -out server.csr
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Next, we're going to sign the public key with our CA:
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Since TLS connections can be made via IP address as well as DNS name, they need
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to be specified when creating the certificate. For example, to allow connections
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using `10.10.10.20` and `127.0.0.1`:
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$ echo subjectAltName = IP:10.10.10.20,IP:127.0.0.1 > extfile.cnf
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$ openssl x509 -req -days 365 -sha256 -in server.csr -CA ca.pem -CAkey ca-key.pem \
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-CAcreateserial -out server-cert.pem -extfile extfile.cnf
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Signature ok
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subject=/CN=your.host.com
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Getting CA Private Key
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Enter pass phrase for ca-key.pem:
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For client authentication, create a client key and certificate signing
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request:
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$ openssl genrsa -out key.pem 4096
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Generating RSA private key, 4096 bit long modulus
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.........................................................++
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................++
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e is 65537 (0x10001)
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$ openssl req -subj '/CN=client' -new -key key.pem -out client.csr
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To make the key suitable for client authentication, create an extensions
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config file:
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$ echo extendedKeyUsage = clientAuth > extfile.cnf
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Now sign the public key:
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$ openssl x509 -req -days 365 -sha256 -in client.csr -CA ca.pem -CAkey ca-key.pem \
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-CAcreateserial -out cert.pem -extfile extfile.cnf
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Signature ok
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subject=/CN=client
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Getting CA Private Key
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Enter pass phrase for ca-key.pem:
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After generating `cert.pem` and `server-cert.pem` you can safely remove the
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two certificate signing requests:
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$ rm -v client.csr server.csr
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With a default `umask` of 022, your secret keys will be *world-readable* and
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writable for you and your group.
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In order to protect your keys from accidental damage, you will want to remove their
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write permissions. To make them only readable by you, change file modes as follows:
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$ chmod -v 0400 ca-key.pem key.pem server-key.pem
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Certificates can be world-readable, but you might want to remove write access to
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prevent accidental damage:
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$ chmod -v 0444 ca.pem server-cert.pem cert.pem
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Now you can make the Docker daemon only accept connections from clients
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providing a certificate trusted by our CA:
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$ docker daemon --tlsverify --tlscacert=ca.pem --tlscert=server-cert.pem --tlskey=server-key.pem \
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-H=0.0.0.0:2376
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To be able to connect to Docker and validate its certificate, you now
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need to provide your client keys, certificates and trusted CA:
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> **Note**: replace all instances of `$HOST` in the following example with the
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> DNS name of your Docker daemon's host.
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$ docker --tlsverify --tlscacert=ca.pem --tlscert=cert.pem --tlskey=key.pem \
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-H=$HOST:2376 version
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> **Note**:
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> Docker over TLS should run on TCP port 2376.
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> **Warning**:
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> As shown in the example above, you don't have to run the `docker` client
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> with `sudo` or the `docker` group when you use certificate authentication.
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> That means anyone with the keys can give any instructions to your Docker
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> daemon, giving them root access to the machine hosting the daemon. Guard
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> these keys as you would a root password!
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## Secure by default
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If you want to secure your Docker client connections by default, you can move
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the files to the `.docker` directory in your home directory -- and set the
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`DOCKER_HOST` and `DOCKER_TLS_VERIFY` variables as well (instead of passing
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`-H=tcp://$HOST:2376` and `--tlsverify` on every call).
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$ mkdir -pv ~/.docker
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$ cp -v {ca,cert,key}.pem ~/.docker
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$ export DOCKER_HOST=tcp://$HOST:2376 DOCKER_TLS_VERIFY=1
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Docker will now connect securely by default:
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$ docker ps
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## Other modes
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If you don't want to have complete two-way authentication, you can run
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Docker in various other modes by mixing the flags.
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### Daemon modes
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- `tlsverify`, `tlscacert`, `tlscert`, `tlskey` set: Authenticate clients
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- `tls`, `tlscert`, `tlskey`: Do not authenticate clients
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### Client modes
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- `tls`: Authenticate server based on public/default CA pool
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- `tlsverify`, `tlscacert`: Authenticate server based on given CA
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- `tls`, `tlscert`, `tlskey`: Authenticate with client certificate, do not
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authenticate server based on given CA
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- `tlsverify`, `tlscacert`, `tlscert`, `tlskey`: Authenticate with client
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certificate and authenticate server based on given CA
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If found, the client will send its client certificate, so you just need
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to drop your keys into `~/.docker/{ca,cert,key}.pem`. Alternatively,
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if you want to store your keys in another location, you can specify that
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location using the environment variable `DOCKER_CERT_PATH`.
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$ export DOCKER_CERT_PATH=~/.docker/zone1/
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$ docker --tlsverify ps
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### Connecting to the secure Docker port using `curl`
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To use `curl` to make test API requests, you need to use three extra command line
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flags:
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$ curl https://$HOST:2376/images/json \
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--cert ~/.docker/cert.pem \
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--key ~/.docker/key.pem \
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--cacert ~/.docker/ca.pem
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## Related information
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* [Using certificates for repository client verification](certificates.md)
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* [Use trusted images](trust/index.md)
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