There are two different systems that need to be configured separately to encrypt communication within the datacenter: gossip encryption and TLS. TLS is used to secure the RPC calls between agents. Gossip communication is secured with a symmetric key, since gossip between agents is done over UDP. In this tutorial, you will only configure gossip encryption
To enable gossip encryption, you need to use an encryption key when starting the Consul agent. The key can be set with the
encrypt parameter in the agent configuration file. Alternatively, the encryption key can be placed in a separate configuration file with only the
encrypt field, since the agent can merge multiple configuration files. The key must be 16-bytes, Base64 encoded.
You can use the Consul CLI command,
consul keygen, to generate a cryptographically suitable key.
$ consul keygen cg8StVXbQJ0gPvMd9o7yrg==
»Enable on a new Consul datacenter
To enable gossip on a new datacenter, you will add the encryption key parameter to the
agent configuration file and then pass the file at startup with the
data_dir = "/opt/consul", log_level = "INFO", node_name = "bulldog", server = true, encrypt = "cg8StVXbQJ0gPvMd9o7yrg=="
$ consul agent -config-dir=/etc/consul.d/ ==> Starting Consul agent... Version: '1.8.1+ent' Node ID: 'b5b5a237-458d-c9eb-b301-db1445e50b80' Node name: 'bulldog' Datacenter: 'dc1' (Segment: '<all>') Server: true (Bootstrap: false) Client Addr: [127.0.0.1] (HTTP: 8500, HTTPS: -1, gRPC: 8502, DNS: 8600) Cluster Addr: 127.0.0.1 (LAN: 8301, WAN: 8302) Encrypt: Gossip: true, TLS-Outgoing: false, TLS-Incoming: false, Auto-Encrypt-TLS: false ...
"Encrypt: true" will be included in the output, if encryption is properly configured.
Note: all nodes within the same datacenter must share the same encryption key in order to send and receive datacenter information, including clients and servers. Additionally, if you're using multiple WAN joined datacenters, be sure to use the same encryption key in all datacenters.
»Enable on an existing Consul datacenter
Gossip encryption can also be enabled on existing datacenters, but requires several extra steps. The additional configuration of the agent configuration parameters,
encrypt_verify_outgoing is necessary.
Step 1: Generate an encryption key using
$ consul keygen JY34uTPZyfUE+6tinMYEVw==
Step 2: Set the
encrypt key, and set
false in the agent configuration file. Then initiate a rolling update of all the agents with these new values. After this step, the agents will be able to decrypt gossip but will not yet be able to send encrypted traffic.
data_dir = "/opt/consul", log_level = "INFO", node_name = "bulldog", server = true, encrypt = "JY34uTPZyfUE+6tinMYEVw==", encrypt_verify_incoming = false, encrypt_verify_outgoing = false
A rolling update can be made by restarting the Consul agents (clients and servers) in turn.
consul reload or
kill -HUP <process_id> is not sufficient to change the gossip configuration.
Step 3: Update the
encrypt_verify_outgoing setting to
true and perform another rolling update of all the agents by restarting Consul on each agent. The agents will now be sending encrypted gossip but will still allow incoming unencrypted traffic.
data_dir = "/opt/consul", log_level = "INFO", node_name = "bulldog", server = true, encrypt = "JY34uTPZyfUE+6tinMYEVw==", encrypt_verify_incoming = false, encrypt_verify_outgoing = true
Step 4: The previous step, enabling verify outgoing, must be completed on all agents before continuing. Update the
encrypt_verify_incoming setting to
true and perform a final rolling update on all the agents .
data_dir = "/opt/consul", log_level = "INFO", node_name = "bulldog", server = true, encrypt = "JY34uTPZyfUE+6tinMYEVw==", encrypt_verify_incoming = true, encrypt_verify_outgoing = true
All the agents will now be strictly enforcing encrypted gossip. Note, the default
behavior of both
You have set them in the configuration file as an explicit example.
In this tutorial, you configured gossip encryption for all agents in your Consul datacenter. Complete the Secure Agent Communication with TLS Encryption tutorial and Secure Consul with Access Control Lists (ACLs) to finish securing your Consul datacenter.