Encryption

SSL/TLS

Free Certificates

Let's Encrypt is a non-profit certificate authority run by Internet Security Research Group that provides X.509 certificates for Transport Layer Security encryption at no charge. The certificate is valid for 90 days, during which renewal can take place at any time. This uses the Automated Certificate Management Environment (ACME) protocol. ACME Clients:

• List of ACME Client Implementations
• pfSense ACME Package

These days I prefer to let pfSense manage the certificate creation and renewal and use a post-renewal script to push the certificate(s) to the machines that need them.

Testing

• SSL Labs SSL Tester
• Security Certificate Revocation Awareness Test
• How To Use OpenSSL s_client To Check and Verify SSL/TLS Of HTTPS Webserver

Server Name Indication (SNI)

SNI allows you to determine where to route traffic based on host name
Allows you to use a single TCP port to provide access to multiple services, depending on the hostname the client is trying to connect to. In addition, each service can have its own unique SSL certificate. This is the most useful way to avoid requirement of a dedicated IP address for each DNS name on a web server.

• Wikipedia
• Enhanced SSL Load Balancing with Server Name Indication (SNI) TLS Extension

Key Management

SSH Key Management

Key Creation

As of December 2015, the most secure key type is ed25519 with 4096-bit:

ssh-keygen -t ed25519 -b 4096 -C my@email.com -f keyfile

Older clients may not support ed25519, but fuck them.

Secure Configuration

Using crypto is only the first step. You need to ensure that the tools you use are locked down to enforce only the protocols that are not known to be weak.

SSH

Server Config

Ciphers

As of 2015-12-04, the best Ciphers setting in /etc/ssh/sshd_config is:

Ciphers aes192-ctr,aes256-ctr,arcfour256,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,arcfour

MACs

As of 2015-12-04, the best MACs setting in /etc/ssh/sshd_config is:

• Disable anything using MD5
• Disable anything using less than 128 bits
• Disable anything not using -etm mode

Use the following config file:

MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com

SSL/TLS Key Management

Key Creation

If you need a SSL/TLS cert that is signed by a root authority for public use in a web browser or other SSL/TLS client, use Let’s Encrypt to get free SSL certificates.
Let’s Encrypt is a new Certificate Authority: It’s free, automated, and open. In Public Beta 2015-12-03.

Secure SSL/TLS Ciphers

See https://www.owasp.org/index.php/TLS_Cipher_String_Cheat_Sheet

Stunnel

As of 2018-07-02, using TLS 1.3 with stunnel, this is the most secure configuration (TLS 1.2 and 1.3 only):

verify = 2
sslVersion = all
options = NO_SSLv3
options = NO_TLSv1
options = NO_TLSv1.1
options = CIPHER_SERVER_PREFERENCE
options = DONT_INSERT_EMPTY_FRAGMENTS
ciphers = TLS13-AES-256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384

Apache

As of 2018-07-02, using TLS 1.2 with apache, this is the most secure configuration (TLS 1.2 only):

SSLEngine On
SSLProtocol TLSv1.2
SSLHonorCipherOrder On
SSLProtocol -ALL +TLSv1.2
SSLCipherSuite "ECDHE-RSA-AES256-GCM-SHA384 ECDHE-RSA-AES128-GCM-SHA256 DHE-RSA-AES256-GCM-SHA384 DHE-RSA-AES128-GCM-SHA256 !ECDHE-RSA-AES256-SHA384 !ECDHE-RSA-AES128-SHA256 !ECDHE-RSA-AES256-SHA !ECDHE-RSA-AES128-SHA !DHE-RSA-AES256-SHA256 !DHE-RSA-AES256-SHA !DHE-RSA-AES128-SHA256 !DHE-RSA-AES128-SHA"

# Enable HSTS
Header always set Strict-Transport-Security "max-age=63072000; includeSubdomains;"