I know I know, there are plenty of openssl cheat sheets out there already (1 or 2). But as I keep using googling it again and again to find the most useful openssl commands I decided to do my own – the first version of the blog entries is already 3 years old actually. Another reason for creating the list is that I remember things better when I am writing the down.

We are currently trying out the cloudflare service to protect one of our company service. In front of this service we are using haproxy as SSL endpoint and loadbalancer. Cloudflare adds a number of custom headers((http://www.linuxorz.com/2014/10/cloudflare-haproxy-get-real-ip/)): _SERVER["HTTP_CF_IPCOUNTRY"] CN _SERVER["HTTP_CF_RAY"] 17da8155355b0520-SEA _SERVER["HTTP_CF_VISITOR"] {"scheme":"http"} _SERVER["HTTP_CF_CONNECTING_IP"] XX.YY.ZZ.00 In order to extract the original client IP in the X_FORWARDD_FOR header, you need to use the following configuration((http://permalink.gmane.org/gmane.comp.web.haproxy/12019)) in haproxy: acl FROM_CLOUDFLARE src -f /etc/haproxy/cf-ips-v4 reqidel ^X-Forwarded-For:.