Merge pull request #918 from estolfo/RUBY-1303-tls-doc

RUBY-1303 Document how to use latest TLS protocols

Author: estolfo

source/contribute.txt

@@ -42,5 +42,5 @@ Contribute to the MongoDB Ruby Driver
 The MongoDB Ruby driver source is located at
 `<https://github.com/mongodb/mongo-ruby-driver>`_.
 
-For instructions in contributing to the driver, see
+For instructions on contributing to the driver, see
 `<https://github.com/mongodb/mongo-ruby-driver/blob/master/CONTRIBUTING.md>`_.

source/installation.txt

@@ -18,5 +18,40 @@ To install the mongo gem manually:
 
 .. code-block:: sh
 
-   gem install mongo -v 2.5.0
+   gem install mongo -v 2.5.1
 
+TLS/SSL and the Ruby driver
+---------------------------
+
+Industry best practices, and some regulations, require the use of TLS 1.1 or newer. Though no application changes are
+required for the Ruby driver to make use of the newest protocols, some operating systems or versions may not provide
+an OpenSSL version new enough to support them.
+
+Users of macOS older than 10.13 (High Sierra) will need to install Ruby from `rvm`_, `homebrew`_, `macports`_, or
+another similar source. See `installation information on ruby-lang.org`_ for more options.
+
+Users of Linux or other non-macOS Unix can check their OpenSSL version like this:
+
+.. code-block:: sh
+
+   $ openssl version
+
+If the version number is less than 1.0.1 support for TLS 1.1 or newer is not available. Contact your operating system
+vendor for a solution or upgrade to a newer distribution.
+
+You can check your Ruby interpreter by executing the following command:
+
+.. code-block:: sh
+
+   ruby -e "require 'net/http'; require 'json'; puts JSON.parse(Net::HTTP.get(URI('https://www.howsmyssl.com/a/check')))['tls_version']"
+
+You should see "TLS 1.X" where X is >= 1.
+
+You can read more about TLS versions and their security implications here:
+
+`<https://www.owasp.org/index.php/Transport_Layer_Protection_Cheat_Sheet#Rule_-_Only_Support_Strong_Protocols>`_
+
+.. _rvm: https://rvm.io/
+.. _homebrew: https://brew.sh/
+.. _macports: https://www.macports.org/
+.. _installation information on ruby-lang.org: https://www.ruby-lang.org/en/documentation/installation