Securing Datacenter-to-Datacenter Replication

This section includes information related to the Datacenter-to-Datacenter Replication security.

Firewall settings

The components of ArangoSync use (TCP) network connections to communicate with each other. Below you’ll find an overview of these connections and the TCP ports that should be accessible.

1. The sync masters must be allowed to connect to the following components within the same datacenter:

   • ArangoDB Agents and Coordinators (default ports: 8531 and 8529)
   • Sync workers (default port 8729)

   Additionally the sync masters must be allowed to connect to the sync masters in the other datacenter.

   By default the sync masters will operate on port 8629.

2. The sync workers must be allowed to connect to the following components within the same datacenter:

   • ArangoDB Coordinators (default port 8529)
   • Sync masters (default port 8629)

   By default the sync workers will operate on port 8729.

Certificates

Digital certificates are used in many places in ArangoSync for both encryption and authentication.

In ArangoSync all network connections are using Transport Layer Security (TLS), a set of protocols that ensure that all network traffic is encrypted. For this TLS certificates are used. The server side of the network connection offers a TLS certificate. This certificate is (often) verified by the client side of the network connection, to ensure that the certificate is signed by a trusted Certificate Authority (CA). This ensures the integrity of the server.
In several places additional certificates are used for authentication. In those cases the client side of the connection offers a client certificate (on top of an existing TLS connection). The server side of the connection uses the client certificate to authenticate the client and (optionally) decides which rights should be assigned to the client.

Formats

All certificates are x509 certificates with a public key, a private key and an optional chain of certificates used to sign the certificate. This chain is typically provided by the Certificate Authority (CA).
Depending on their use, certificates stored in a different format.

The following formats are used:

• Public key only (.crt): A file that contains only the public key of a certificate with an optional chain of parent certificates (public keys of certificates used to signed the certificate).
  Since this format contains only public keys, it is not a problem if its contents are exposed. It must still be store it in a safe place to avoid losing it.
• Private key only (.key): A file that contains only the private key of a certificate.
  It is vital to protect these files and store them in a safe place.
• Keyfile with public & private key (.keyfile): A file that contains the public key of a certificate, an optional chain of parent certificates and a private key.
  Since this format also contains a private key, it is vital to protect these files and store them in a safe place.
• Java keystore (.jks): A file containing a set of public and private keys.
  It is possible to protect access to the content of this file using a keystore password.
  Since this format can contain private keys, it is vital to protect these files and store them in a safe place (even when its content is protected with a keystore password).

Creating certificates

ArangoSync provides commands to create all certificates needed.

TLS server certificates

To create a certificate used for TLS servers in the keyfile format, you need the public key of the CA (--cacert), the private key of the CA (--cakey) and one or more hostnames (or IP addresses). Then run:

arangosync create tls keyfile \
    --cacert=my-tls-ca.crt --cakey=my-tls-ca.key \
    --host=<hostname> \
    --keyfile=my-tls-cert.keyfile

Make sure to store the generated keyfile (my-tls-cert.keyfile) in a safe place.

To create a certificate used for TLS servers in the crt & key format, you need the public key of the CA (--cacert), the private key of the CA (--cakey) and one or more hostnames (or IP addresses). Then run:

arangosync create tls certificate \
    --cacert=my-tls-ca.crt --cakey=my-tls-ca.key \
    --host=<hostname> \
    --cert=my-tls-cert.crt \
    --key=my-tls-cert.key \

Make sure to protect and store the generated files (my-tls-cert.crt & my-tls-cert.key) in a safe place.

Client authentication certificates

To create a certificate used for client authentication in the keyfile format, you need the public key of the CA (--cacert), the private key of the CA (--cakey) and one or more hostnames (or IP addresses) or email addresses. Then run:

arangosync create client-auth keyfile \
    --cacert=my-client-auth-ca.crt --cakey=my-client-auth-ca.key \
    [--host=<hostname> | --email=<emailaddress>] \
    --keyfile=my-client-auth-cert.keyfile

Make sure to protect and store the generated keyfile (my-client-auth-cert.keyfile) in a safe place.

CA certificates

To create a CA certificate used to sign TLS certificates, run:

arangosync create tls ca \
    --cert=my-tls-ca.crt --key=my-tls-ca.key 

Make sure to protect and store both generated files (my-tls-ca.crt & my-tls-ca.key) in a safe place.

To create a CA certificate used to sign client authentication certificates, run:

arangosync create client-auth ca \
    --cert=my-client-auth-ca.crt --key=my-client-auth-ca.key

Make sure to protect and store both generated files (my-client-auth-ca.crt & my-client-auth-ca.key) in a safe place.

Renewing certificates

All certificates have meta information in them the limit their use in function, target & lifetime.
A certificate created for client authentication (function) cannot be used as a TLS server certificate (same is true for the reverse).
A certificate for host myserver (target) cannot be used for host anotherserver.
A certificate that is valid until October 2017 (lifetime) cannot be used after October 2017.

If anything changes in function, target or lifetime you need a new certificate.

The procedure for creating a renewed certificate is the same as for creating a “first” certificate.
After creating the renewed certificate the process(es) using them have to be updated. This mean restarting them. All ArangoSync components are designed to support stopping and starting single instances, but do not restart more than 1 instance at the same time. As soon as 1 instance has been restarted, give it some time to “catch up” before restarting the next instance.