module OpenSSL

Overview

NOTE To use OpenSSL, you must explicitly import it with require "openssl"

OpenSSL Integration

• TLS sockets need a context, potentially with keys (required for servers) and configuration.
• TLS sockets will wrap the underlying TCP socket, and any further communication must happen through the OpenSSL::SSL::Socket only.

Usage Example

Recommended ciphers can be taken from:

• OWASP Wiki
• Cipherli.st
• A full list is available at the OpenSSL Docs

Do note that:

• Crystal does its best to provide sane configuration defaults (see Mozilla-Intermediate).
• Linked version of OpenSSL need to be checked for supporting specific protocols and ciphers.
• If any configurations or choices in Crystal regarding SSL settings and security are found to be lacking or need improvement please open an issue and let us know.

Server side

NOTE For the below example to work, a key pair should be attained.

require "socket"
require "openssl"

def server
  # Bind new TCPSocket to port 5555
  socket = TCPServer.new(5555)

  context = OpenSSL::SSL::Context::Server.new
  context.private_key = "/path/to/private.key"
  context.certificate_chain = "/path/to/public.cert"

  puts "Server is up"

  socket.accept do |client|
    puts "Got client"

    bytes = Bytes.new(20)

    ssl_socket = OpenSSL::SSL::Socket::Server.new(client, context)
    ssl_socket.read(bytes)

    puts String.new(bytes)
  end
end

Client side

require "socket"
require "openssl"

def client
  socket = TCPSocket.new("127.0.0.1", 5555)
  context = OpenSSL::SSL::Context::Client.new

  ssl_socket = OpenSSL::SSL::Socket::Client.new(socket, context)
  ssl_socket << "Testing"
end

Defined in:

openssl_ext/bio.cr
openssl_ext/pkey.cr
openssl_ext/rsa.cr