added documentation for psk auth

README.md

@@ -1,7 +1,7 @@
 Stunnel
 =========
 [![Galaxy](http://img.shields.io/badge/ansible--galaxy-stunnel-blue.svg)](https://galaxy.ansible.com/list#/roles/3502)
-[![License](http://img.shields.io/:license-mit-blue.svg)](http://doge.mit-license.org)  
+[![License](http://img.shields.io/:license-mit-blue.svg)](http://doge.mit-license.org)
 
 
 Ansible role to install stunnel in order to achieve SSL Termination on Linux machines.
@@ -13,6 +13,8 @@ Role Variables
 --------------
 
 ```
+stunnel_use_cert (default True) : determines if we use certificates
+stunnel_use_psk (default False) : determines if we use psk
 stunnel_certificate_generation (default False) : determines if this role has to generate a self signed certificate
 stunnel_certificate_duration: (optional, if stunnel_certificate_generation is True, default 365) : self signed certificate validity duration
 stunnel_certificate_domain: (optional, if stunnel_certificate_generation is True, default www.domain.com) : self signed certificate domain field
@@ -22,12 +24,16 @@ stunnel_certificate_state_name: (optional, if stunnel_certificate_generation is
 stunnel_certificate_locality: (optional, if stunnel_certificate_generation is True, default locality) : self signed certificate locality field
 stunnel_certificate_file: certificate file to generate or use, depends on stunnel_certificate_generation value. Default is /tmp/certificate.pem
 stunnel_key_file: key file to generate or use, depends on stunnel_certificate_generation value. Default is /tmp/key.pem
+stunnel_psks: a list of psk. This look like this:
+- name: client1
+  psk: AEO/WE+pBCn3+WBy3FJoyJF/HEBZqMym
+
 stunnel_services: list of services. They look like this:
 - service:
-    name: https
-    accept: 443
-    connect: 80
-  
+  name: https
+  accept: 443
+  connect: 80
+
 ```
 
 Dependencies
@@ -59,6 +65,30 @@ Example Playbook
         connect: 80
 ```
 
+you may also use [PSK (Pre Shared Keys)](https://www.stunnel.org/auth.html)
+which allow faster communication
+at the cost of knowing clients in advance.
+
+```
+- hosts: all
+
+  roles:
+  - role: stunnel-role
+    stunnel_use_cert: false
+    stunnel_use_psk: true
+    stunnel_psk:
+      - name: client1
+        psk: ATJX7VOAMIF2nhaknNVmSqSQGrCvMyPt
+      - name: client2
+        psk: enNezGQMkZmSyjTDjpndjrBEXhJ9ki3v
+    stunnel_services:
+      - service:
+        name: postfix
+        accept: 12221
+        connect: 21
+```
+
+
 License
 -------