[ELK Stack] Generate TLS certs for filebeat and logstash

gistfile1.txt

1. Generate new domain name for logstash server.

For this tutorial 
domain name = logstash-prod.xyz.com
ip = 1.2.3.4

* Enter to following directory
```
$ sudo mkdir /etc/pki
$ cd /etc/pki
```

* Generate CA and self-sign it.

```
$ mkdir -p certs/{devices,client,ca,tmp}
$ openssl genrsa -out certs/ca/root-ca.key.pem 2048
$ openssl req -x509 -new -nodes -key certs/ca/root-ca.key.pem -days 9131 -out certs/ca/root-ca.crt.pem -subj "/C=US/ST=Utah/L=Provo/O=ACME Signing Authority Inc/CN=logstash-prod.xyz.com"
```

* Generate logstash certs

```
$ openssl genrsa -out certs/devices/logstash.key.pem 2048
$ openssl req -new -key certs/devices/logstash.key.pem -out certs/tmp/logstash.csr.pem -subj "/C=US/ST=Utah/L=Provo/O=ACME Service/CN=logstash-prod.xyz.com"
$ openssl x509 -req -in certs/tmp/logstash.csr.pem -CA certs/ca/root-ca.crt.pem -CAkey certs/ca/root-ca.key.pem -CAcreateserial -out certs/devices/logstash.crt.pem -days 9131
```

* Generate filebeat certs
```
$ openssl genrsa -out certs/devices/filebeat.key.pem 2048
$ openssl req -new -key certs/devices/filebeat.key.pem -out certs/tmp/filebeat.csr.pem -subj "/C=US/ST=Utah/L=Provo/O=ACME Service/CN=logstash-prod.xyz.com"
$ openssl x509 -req -in certs/tmp/filebeat.csr.pem -CA certs/ca/root-ca.crt.pem -CAkey certs/ca/root-ca.key.pem -CAcreateserial -out certs/devices/filebeat.crt.pem -days 9131
```

* convert private key to PKCS8 format
```
$ openssl pkcs8 -topk8 -inform pem -in certs/devices/logstash.key.pem -outform pem -nocrypt -out certs/devices/logstash-pkcs8.pem
$ openssl pkcs8 -topk8 -inform pem -in certs/devices/filebeat.key.pem -outform pem -nocrypt -out certs/devices/filebeat-pkcs8.pem
```
* Give `777` file permission to all these certs

* Restart logstash if you did it after starting logstash
`$ cd /etc/deploy/docker-compose && sudo docker-compose down`

* verify it
```
$ curl -v --key certs/devices/filebeat-pkcs8.pem --cert certs/devices/filebeat.crt.pem --cacert certs/ca/root-ca.crt.pem https://logstash-prod.xyz.com:5044
```