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Creating TLS Certificates, Keys and Other TLS Artifacts

This document describes how to create TLS certificates, keys and other artifacts for the server components. The generated CA certificate and Java truststore may also be used on client-side for validating the servers' certificates.

Overview

A TLS server certificate is an X.509 digital certificate that binds the server's identity (such as the server's DNS name or IP address or both) to the server's public key. The public key is part of the public-private key pair used for asymmetric encryption during the TLS handshake.

Each Controller and Segment Store service requires a pair of PEM-encoded TLS certificate and private key. Each service also requires a PEM-encoded certificate of the CA that has signed the server certificates. Moreover, the Controller REST interface requires its certificate and keys in Java JKS formats. We refer to all the required files as TLS artifacts, henceforth.

While the TLS certificate is public, the corresponding key is private and must be kept protected (typically in the server that uses the TLS certificate and the key). Each server should use its own set of TLS artifacts; reusing certificates requires reusing private keys as well, and sharing private keys across multiple servers increases the risk that they will be compromised.

Here are a few strategies for determining the sets of TLS artifacts required for a Pravega cluster:

  1. Use separate TLS artifacts for each host/machine or service.

Manual deployments supports this and the other configurations listed below. This is the most secure option. 2. Use two sets of TLS artifacts - one for the Controllers and the other for the Segment Stores.

In this case, each certificate is assigned to all the respective nodes (Controllers or Segment Stores) by specifying the nodes' DNS names and/or IP addresses in the certificate's Subject Alternative Name (SAN) field. Also, the server certificates might need to be recreated to add DNS names and/or IP addresses of the new servers whenever the Controllers or the Segment stores are scaled up.

Kubernetes and other forms of containerized deployments supports this configuration.

  1. Use the same set for all Controllers and Segment Store services.

In this case, the certificate must contain the DNS names and/or IP addresses of all the Controller and Segment Store services. This is the least secure option. Also, the server certificate might need to be recreated to add DNS names and/or IP addresses of the new servers whenever the Controllers or the Segment stores are scaled up.

All deployment options support this configuration.

The chosen configuration determines the number of TLS artifacts sets required for a Pravega cluster. Each set can be prepared using the process described later in this document under Generate TLS Certificates and Other TLS Artifacts for the Server.

Another important consideration is whether you want to terminate TLS at an external infrastructural component like reverse proxy, Kubernetes Ingress or a load balancer. If TLS is terminated at such an infrastructural component, instead of Pravega services, you will need to generate TLS artifacts for those infrastructural components instead, using similar steps described in this document; however, the exact steps may be slightly different and additional steps may be required to ensure that other parts of the infrastructure can communicate with it. Refer to the respective platform vendor's documentation, such as this one from Google Kubernetes Engine, for instructions.

Before you Begin:

The steps described in this document use OpenSSL and Java Keytool to generate TLS artifacts like certificates, keys, Java keystores and Java truststores. Install OpenSSL and Java Development Kit (JDK) on the hosts where the artifacts will be generated.

Note: * The examples shown in this document use command line arguments to pass all inputs to the command. To pass sensitive command arguments via prompts instead, just exclude the corresponding option (as shown in the second command below). 

# Passwords are passed as command line arguments.
$ keytool -keystore server01.keystore.jks -alias server01 -validity <validity> -genkey \
            -storepass <keystore-password> -keypass <key-password> \
            -dname <distinguished-name> -ext SAN=DNS:<hostname>,

# Passwords (and some other arguments) are to be entered interactively on the prompt.
$ keytool -keystore server01.keystore.jks -alias server01 -genkey
* A weak password changeit is used everywhere in this document for easier reading. Be sure to replace it with a strong and separate password for each file.

Setting up a Certificate Authority (CA)

If you are planning to use a public CA or an existing private/internal CA, you may skip this part altogether and go directly to the next section.

Here, we'll create a CA in the form of a public/private key pair and a self-signed certificate. Later, we'll use this CA certificate/key bundle to sign the servers' certificates.

  1. Generate a CA certificate and public/private key pair. 
$ openssl req -new -x509 -keyout <ca-private-key-file-path> -out <ca-cert-file-path> -days <validity-in-days> \
         -subj "<distinguished_name>" \
         -passout pass:<ca-private-key-password>

Example: 

# In MinGW/MSYS, the same -subj argument will be:
# "//C=US\ST=Washington\L=Seattle\O=Pravega\OU=CA\CN=Pravega-Stack-CA"
$ openssl req -new -x509 -keyout ca-key.key -out ca-cert.crt -days 365 \
         -subj "/C=US/ST=Washington/L=Seattle/O=Pravega/OU=CA/CN=Pravega-Stack-CA" \
         -passout pass:changeit

The command above will generate the following two PEM-encoded files: * A file ca-key.key containing the encrypted private key. * A file ca-cert.crt containing the CA certificate.

  1. Optionally, create a Java truststore containing the CA's certificate. This may be used by client applications if they configure the truststore using the javax.net.ssl.trustStore Java option. 
$ keytool -keystore <java-truststore-file-path> -noprompt \
          -alias <trusted-cert-entry-alias> \
          -import -file <ca-cert-file-path> \
          -storepass <java-truststore-file-password>

Example: 

$ keytool -keystore client.truststore.jks -noprompt \
          -alias caroot \ 
          -import -file ca-cert.crt \
          -storepass changeit

# Optionally, list the truststore's contents and inspect the output to verify everything is in order. The output 
# should show a single entry with alias name `caroot` and entry type `trustedCertEntry`.
$ keytool -list -v -keystore client.truststore.jks -storepass changeit

At this point, the following CA and truststore artifacts should be ready:

File Description Example command for inspecting the file's Contents
ca-cert.crt A PEM-encoded file containing the X.509 certificate of the CA $ openssl x509 -in ca-cert.crt -text -noout
ca-key.key A PEM-encoded file containing the CA's encrypted private key $ openssl pkcs8 -inform PEM -in ca-key.key -topk8
client.truststore.jks A password-protected truststore file containing the CA's certificate $ keytool -list -v -keystore client.truststore.jks -storepass changeit

Generate TLS Certificates and Other TLS Artifacts for the Server

Here, we prepare a set of TLS artifacts that can be used by one or more nodes.

We'll use the CA created in the previous stage to sign the server certificate for demonstration, but in real usage you may instead get it signed by an existing internal CA in your environment or a public CA.

The high-level steps involved in this stage are:

  1. Generate a set of server certificate and private key.
  2. Generate a Certificate Signing Request (CSR) for the server certificate.
  3. Submit the CSR to a CA and obtain a signed certificate.
  4. Prepare a keystore containing the signed server certificate and the CA's certificate.
  5. Export the server certificate's private key.

Note that these steps will need to be repeated with different input for each set. We discussed the number of sets required earlier in the Overview section.

The above steps are described below:

  1. Generate a set of server certificate and private key.

The following command will generate a Java JKS keystore containing the following artifacts for the server: * An X.509 certificate containing the public key identifying the server * A private key for the public/private key pair

$ keytool -storetype JKS -keystore <java-keystore-file-name> -storepass <java-keystore-password>\
        -genkey -keyalg <key-algorithm> -keysize <key-size> -keypass <private-key-password>\
        -alias <alias> -validity <validity>\
        -dname "<distinguished-name>"\
        -ext SAN=dns:<hostname1>,dns:<hostname2>,ip:<ipaddress1>

Example: 

$ keytool -storetype JKS -keystore server_unsigned.keystore.jks -storepass changeit\
           -genkey -keyalg RSA -keysize 2048 -keypass changeit\
           -alias server -validity 365\
           -dname "CN=server.pravega.io, OU=analytics, O=pravega, L=Seattle, ST=Washington, C=US"\
           -ext SAN=dns:server1.pravega.io,dns:server2.pravega.io,ip:127.0.0.1

# Optionally, verify the contents of the generated file
$ keytool -list -v -storetype JKS -keystore server_unsigned.keystore.jks -storepass changeit

  1. Generate a Certificate Signing Request (CSR) for the server certificate.

It helps to think of a CSR as an application for getting a certificate signed by a trusted authority.

A CSR is typically generated on the same server/node that uses the certificate, so that the corresponding private key doesn't need to be moved anywhere else. In some other environments, CSRs are generated in a central server and the resulting certificates are distributed to the services that need them. 

$ keytool -keystore <java-keystore-file-path> -storepass <java-keystore-password> -alias <alias> \
          -certreq -file <csr-file-path> \
          -storepass <java-keystore-password>

Example: 

$ keytool -keystore server_unsigned.keystore.jks -storepass changeit -alias server \ 
          -certreq -file server.csr \
          -ext SAN=dns:server1.pravega.io,dns:server2.pravega.io,ip:127.0.0.1

  1. Submit the CSR to a CA and obtain a signed certificate.

If you are using a public or internal CA service, follow that CA's process for submitting the CSR and obtaining a signed certificate. To use the custom CA generated using the steps mentioned earlier or an internal CA certificate/key bundle, use the steps below:

First create a server-csr.conf file with the following contents. Replace alt_names with the server's hostname/ IP address that Pravega will use to access the server. If the same certificate is used in multiple servers, add hostnames/IP addresses of all the servers. 

[req]
req_extensions = v3_req
prompt = no

[v3_req]
subjectAltName = @alt_names

[alt_names]
DNS.1 = server1.pravega.io
DNS.2 = server2.pravega.io
IP.1 = 127.0.0.1

Now, have the CA sign the certificate:

$ openssl x509 -req -CA <ca-cert-file-path> -CAkey <ca-private-key-file-path> \ 
        -in <csr-file-path> -out <signed-server-cert-file-path> \
        -days <validity> -CAcreateserial -passin pass:<csr-file-password> \
        -extfile server-csr.conf -extensions v3_req

Example: 

$ openssl x509 -req -CA ca-cert.crt -CAkey ca-key.key \
     -in server.csr -out server-cert.crt \
     -days 365 -CAcreateserial -passin pass:changeit \
     -extfile server-csr.conf -extensions v3_req

# Optionally, check the contents of the signed certificate.
$ openssl x509 -in server-cert.crt -text -noout

  1. Prepare a new keystore containing the signed server certificate and the CA's certificate chain. 
# Import the CA certificate into a new keystore file.
$ keytool -keystore <server-jks-keystore-file-path> -alias <ca-alias> -noprompt \
             -import -file <ca-cert-file-path> -storepass <server-jks-keystore-password>

# Import the signed server certificate into the keystore.
$ keytool -keystore <server-jks-keystore-file-path> -alias <server-alias> -noprompt \
             -import -file <signed-server-cert-file-path> -storepass <server-jks-keystore-password>

Example: 

$ keytool -keystore server.keystore.jks -alias CARoot -noprompt \
          -import -file ca-cert.crt -storepass changeit

$ keytool -keystore server.keystore.jks -alias server -noprompt \
             -import -file server-cert.crt -storepass changeit

# Optionally, list the keystore and inspect the output
$ keytool -list -v -storepass changeit -keystore server.keystore.jks

  1. Export the server certificate's private key.

This is a two-step process. * First, convert the server's keystore in .jks format into .p12 format.

 ```bash
 $ keytool -importkeystore \
           -srckeystore <server-jks-keystore-file-path> \
           -destkeystore <server-pkcs12-keystore-file-path> \
           -srcstoretype jks -deststoretype pkcs12 \
           -srcstorepass <server-jks-keystore-password> -deststorepass <server-pkcs12-keystore>
 ```

 Example:
 ```bash
 $ keytool -importkeystore \
           -srckeystore server.keystore.jks \
           -destkeystore server.keystore.p12 \
           -srcstoretype jks -deststoretype pkcs12 \
           -srcstorepass changeit -deststorepass changeit
 ```

  • Now, export the private key of the server into a PEM encoded file. Note that the generated PEM file is not protected by a password. The key itself is password-protected, as we are using the -nodes flag. So, be sure to protect it using operating system's technical and procedural controls.

    $ openssl pkcs12 -in <server-pkcs12-keystore-file-path> -passin pass:<key-password> \
                 -nodes -out <server-key-file-path>

    Example: 

    $ openssl pkcs12 -in server.keystore.p12 -out server-key.key -passin pass:changeit -nodes

Step 5 concludes this stage and we are now now set for installing the certificates and other TLS artifacts in Pravega.

The table below lists the key output of this stage.

File Description Command for Inspecting the Contents
server-cert.crt A PEM-encoded file containing the CA-signed X.509 server certificate openssl x509 -in server-cert.crt -text -noout
server-key.key A PEM-encoded file containing the server's encrypted private key openssl pkcs8 -inform PEM -in server-key.key -topk8
server.keystore.jks A password-protected server keystore file in .jks format keytool -list -v -keystore server.keystore.jks -storepass changeit