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Generate certificates

If you don’t have access to a certificate authority (CA) for your organization and want to use Open Distro for Elasticsearch for non-demo purposes, you can generate your own self-signed certificates using OpenSSL.

You can probably find OpenSSL in the package manager for your operating system.

On CentOS, use Yum:

sudo yum install openssl

On macOS, use Homebrew:

brew install openssl

Generate a private key

The first step in this process is to generate a private key using the genrsa command. As the name suggests, you should keep this file private.

Private keys must be of sufficient length to be secure, so specify 2048:

openssl genrsa -out root-ca-key.pem 2048

You can optionally add the -aes256 option to encrypt the key using the AES-256 standard. This option requires a password.

Generate a root certificate

Next, use the key to generate a self-signed certificate for the root CA:

openssl req -new -x509 -sha256 -key root-ca-key.pem -out root-ca.pem -days 30

Change -days 30 to 3650 (10 years) or some other number to set a non-default expiration date. The default value of 30 days is best for testing purposes.

  • The -x509 option specifies that you want a self-signed certificate rather than a certificate request.
  • The -sha256 option sets the hash algorithm to SHA-256. SHA-256 is the default in later versions of OpenSSL, but earlier versions might use SHA-1.

Follow the prompts to specify details for your organization. Together, these details form the distinguished name (DN) of your CA.

Generate an admin certificate

To generate an admin certificate, first create a new key:

openssl genrsa -out admin-key-temp.pem 2048

Then convert that key to PKCS#8 format for use in Java using a PKCS#12-compatible algorithm (3DES):

openssl pkcs8 -inform PEM -outform PEM -in admin-key-temp.pem -topk8 -nocrypt -v1 PBE-SHA1-3DES -out admin-key.pem

Next, create a certificate signing request (CSR). This file acts as an application to a CA for a signed certificate:

openssl req -new -key admin-key.pem -out admin.csr

Follow the prompts to fill in the details. You don’t need to specify a challenge password. As noted in the OpenSSL Cookbook, “Having a challenge password does not increase the security of the CSR in any way.”

Finally, generate the certificate itself:

openssl x509 -req -in admin.csr -CA root-ca.pem -CAkey root-ca-key.pem -CAcreateserial -sha256 -out admin.pem -days 30

Just like the root certificate, use the -days option to specify an expiration date of longer than 30 days.

(Optional) Generate node and client certificates

Follow the steps in Generate an admin certificate with new file names to generate a new certificate for each node and as many client certificates as you need. Each certificate should use its own private key.

If you generate node certificates and have opendistro_security.ssl.transport.enforce_hostname_verification set to true (default), be sure to specify a common name (CN) for the certificate that matches the hostname of the intended node. If you want to use the same node certificate on all nodes (not recommended), set the hostname verification to false. For more information, see Configure TLS certificates.

Sample script

# Root CA
openssl genrsa -out root-ca-key.pem 2048
openssl req -new -x509 -sha256 -key root-ca-key.pem -out root-ca.pem -days 30
# Admin cert
openssl genrsa -out admin-key-temp.pem 2048
openssl pkcs8 -inform PEM -outform PEM -in admin-key-temp.pem -topk8 -nocrypt -v1 PBE-SHA1-3DES -out admin-key.pem
openssl req -new -key admin-key.pem -out admin.csr
openssl x509 -req -in admin.csr -CA root-ca.pem -CAkey root-ca-key.pem -CAcreateserial -sha256 -out admin.pem -days 30
# Node cert
openssl genrsa -out node-key-temp.pem 2048
openssl pkcs8 -inform PEM -outform PEM -in node-key-temp.pem -topk8 -nocrypt -v1 PBE-SHA1-3DES -out node-key.pem
openssl req -new -key node-key.pem -out node.csr
openssl x509 -req -in node.csr -CA root-ca.pem -CAkey root-ca-key.pem -CAcreateserial -sha256 -out node.pem -days 30
#Client cert
openssl genrsa -out client-key-temp.pem 2048
openssl pkcs8 -inform PEM -outform PEM -in client-key-temp.pem -topk8 -nocrypt -v1 PBE-SHA1-3DES -out client-key.pem
openssl req -new -key client-key.pem -out client.csr
openssl x509 -req -in client.csr -CA root-ca.pem -CAkey root-ca-key.pem -CAcreateserial -sha256 -out client.pem -days 30
# Cleanup
rm admin-key-temp.pem
rm admin.csr
rm node-key-temp.pem
rm node.csr
rm client-key-temp.pem
rm client.csr

If you already know the certificate details and don’t want to specify them as the script runs, use the -subj option in your root-ca.pem and CSR commands:

openssl req -new -key node-key.pem -subj "/C=CA/ST=ONTARIO/L=TORONTO/O=ORG/OU=UNIT/CN=node1.example.com" -out node.csr

Get distinguished names

If you created admin and node certificates, you must specify their distinguished names (DNs) in elasticsearch.yml on all nodes:

opendistro_security.authcz.admin_dn:
  - 'CN=ADMIN,OU=UNIT,O=ORG,L=TORONTO,ST=ONTARIO,C=CA'
opendistro_security.nodes_dn:
  - 'CN=node1.example.com,OU=UNIT,O=ORG,L=TORONTO,ST=ONTARIO,C=CA'
  - 'CN=node2.example.com,OU=UNIT,O=ORG,L=TORONTO,ST=ONTARIO,C=CA'

But if you look at the subject of the certificate after creating it, you might see different formatting:

subject=/C=CA/ST=ONTARIO/L=TORONTO/O=ORG/OU=UNIT/CN=node1.example.com

If you compare this string to the ones in elasticsearch.yml above, you can see that you need to invert the order of elements and use commas rather than slashes. Enter this command to get the correct string:

openssl x509 -subject -nameopt RFC2253 -noout -in node.pem

Then you can copy and paste the output into elasticsearch.yml:

subject= CN=node1.example.com,OU=UNIT,O=ORG,L=TORONTO,ST=ONTARIO,C=CA

Configure certificates

This process generates many files, but these are the ones you need to add to your cluster configuration:

  • root-ca.pem
  • admin.pem
  • admin-key.pem
  • (Optional) each-node-cert.pem
  • (Optional) each-node-key.pem

For information about adding and configuring these certificates, see Docker security configuration and Configure TLS certificates.

Run securityadmin.sh

After configuring your certificates and starting Elasticsearch, run securityadmin.sh to initialize the security plugin:

./securityadmin.sh -cd ../securityconfig/ -icl -nhnv -cacert ../../../config/root-ca.pem -cert ../../../config/admin.pem -key ../../../config/admin-key.pem

For more information about what this command does, see Apply configuration changes.

If you use Docker, see Bash access to containers.

Kibana

Depending on your settings in kibana.yml, you might need to add root-ca.pem to your Kibana node. You have two options: disable SSL verification or add the root CA.

  • Disable SSL verification:

    elasticsearch.ssl.verificationMode: none
    
  • Add the root CA:

    elasticsearch.ssl.certificateAuthorities: ["/usr/share/kibana/config/root-ca.pem"]
    elasticsearch.ssl.verificationMode: full