Add article on OpenSSH public key auth

In addition to adding the article itself, make changes to the default
layout and stylesheets for better appearance of article pages.

Rules

@@ -40,4 +40,4 @@ route '*' do
   end
 end
 
-layout '*', :haml
+layout '*', :haml, :ugly => true

content/help/openssh-keygen.markdown

@@ -0,0 +1,89 @@
+---
+title: Key-based authentication with OpenSSH
+---
+
+In the interests of security, the Computer Science Club Dominion Server only
+accepts key-based authentication for logging into its SSH server.  This renders
+brute-force password attacks ineffective, and reduces the potential for remote
+access vulnerabilities.  Here’s a quick guide for OpenSSH users on how to
+create your own key pair and use it to log in to the CSCDS.
+
+<section markdown="1">
+Creating your keys
+==================
+
+To generate a key pair, first run `ssh-keygen` at a shell prompt on your local
+machine.  You’ll be prompted for a filename to use for the key pair (you can
+enter nothing to accept the default of `~/.ssh/id_rsa`), then a passphrase:
+
+    me@localhost:~$ ssh-keygen
+    Generating public/private rsa key pair.
+    Enter file in which to save the key (/home/me/.ssh/id_rsa): 
+    Enter passphrase (empty for no passphrase): Enter same passphrase again: 
+
+This passphrase is used to encrypt the private key on your local computer, so
+it’s recommended that you pick a strong one so that your account is not open to
+immediate compromise should the key files be lost.  After entering a filename
+and passphrase, you’ll get something like the following output:
+
+    Your identification has been saved in /home/me/.ssh/id_rsa.
+    Your public key has been saved in /home/me/.ssh/id_rsa.pub.
+    The key fingerprint is:
+    12:34:56:78:9a:bc:de:f0:12:34:56:78:9a:bc:de me@localhost
+    The key's randomart image is:
+    +--[ RSA 2048]----+
+    | ..o.            |
+    | .o..o           |
+    |o..oo .          |
+    |+o.. o           |
+    |E . . o S        |
+    |=o + . .         |
+    |+.o .            |
+    | ..o             |
+    | .. .            |
+    +-----------------+
+
+You’ll notice that two files have been created: a private key file with the
+filename that you specified (here, `id_rsa`) and a corresponding public key
+file (`id_rsa.pub`).  The private key is, as the name implies, only for
+you&nbsp;— you’ll use the (decrypted) contents of this file, which the SSH
+server checks against the public key on the server side, to log in.
+
+Which means, of course, that you’ll need to get the public key on the server
+first.  This is where you send an e-mail to the administrators with your SSH
+username and the contents of `id_rsa.pub` (_not_ `id_rsa`, which is for your
+eyes only and useless to the administrators anyway).
+</section>
+
+<section markdown="1">
+Logging in for the first time
+=============================
+
+Once you’ve received word that your private key can be used to log in, you can
+use the following command to specify your key file and log in to the CSCDS:
+
+    ssh -i /home/me/.ssh/id_rsa me@csclub.cs.unc.edu
+
+Of course, replace `me` with your username and the path after `-i` with the
+actual path to the private key file if you specified a different one.  You
+should be prompted for your passphrase, and if all goes well, you’ll get the
+CSCDS welcome banner and a shell prompt.  Yay!
+</section>
+
+<section markdown="1">
+Editing your SSH configuration file
+===================================
+
+Now, entering that entire command line every single time you want to log in
+will get old _really_ quickly.  Fortunately, you can edit your `~/.ssh/config`
+file and specify that you want to always send a certain key file and username
+when you log in to the CSCDS.  Simply add the following lines to `config`,
+creating it if it doesn’t exist:
+
+    Host csclub.cs.unc.edu
+    IdentityFile /home/me/.ssh/id_rsa
+    User me
+
+Now you can log in by simply entering `ssh csclub.cs.unc.edu`, and OpenSSH will
+automatically pick up on your key file and username.
+</section>

content/index.markdown

@@ -15,6 +15,7 @@ Informal leadership committee for 2011–12:
 
 Other things you may find useful:
 
+* [Key-based authentication with OpenSSH](help/openssh-keygen/)
 * [Slides for Chris Davis’ CrackChats](crackchat/)
 * CS Club SBP forum results:
     [2011](http://www.unc.edu/~zhoum/csclub_sbpforum_2011.html),

content/stylesheet.scss

@@ -7,13 +7,22 @@ html, body {
 }
 
 #wrapper {
+    position: relative;
     width: 566px;
     font: 83%/1.25 'Helvetica Neue', 'Arial', sans-serif;
     margin: 2em auto 0;
     padding: 65px 0 0 110px;
     background: url(cowlogo.png) no-repeat;
 }
 
-header {
-    display: none;
+header, header h1, header a {
+    display: block;
+    position: absolute;
+    left: 0;
+    top: 0;
+    width: 676px;
+    height: 65px;
+    text-indent: -999px;
+    margin: 0;
+    padding: 0;
 }

layouts/default.haml

@@ -11,6 +11,14 @@
     %body
         #wrapper
             %header
-                %h1 UNC Computer Science Club
+                %h1
+                    - if @item.identifier == '/'
+                        UNC Computer Science Club
+                    - else
+                        %a{:href => '/'} UNC Computer Science Club
 
-            = yield
+            %article
+                - if @item[:title]
+                    %h1= @item[:title]
+
+                = yield