This is a CAS client written entirely using nginx's lua module. It is similar to apache mod_auth_cas.

• ngx_http_lua_module by OpenResty :

apt install libnginx-mod-http-lua

or

yum install nginx-mod-http-lua

• lua-resty-http :

mkdir -p /etc/nginx/lua/resty
cd /etc/nginx/lua/resty/
wget https://raw.githubusercontent.com/ledgetech/lua-resty-http/master/lib/resty/http_headers.lua
wget https://raw.githubusercontent.com/ledgetech/lua-resty-http/master/lib/resty/http.lua

cd /etc/nginx/lua/
wget https://raw.githubusercontent.com/prigaux/nginx-auth-cas-lua/master/src/cas.lua
wget https://raw.githubusercontent.com/prigaux/nginx-auth-cas-lua/master/src/global_cas_conf.lua

• configure cas_uri in /etc/nginx/lua/global_cas_conf.lua
• configure various global stuff in nginx config

# needed for resty.http
resolver 8.8.8.8;
lua_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;

lua_package_path '/etc/nginx/lua/?.lua;;';
lua_shared_dict cas_store 10M;

• protect a location (REMOTE_USER is passed to proxy implicitly):

location /secured {
    access_by_lua_block { require('cas').forceAuthentication() }
    proxy_pass ...;
    ...
}

NB: access_by_lua_block must be before proxy_pass

• or for FASTCGI protect a location and provide REMOTE_USER explicitly:

  location /secured {
    access_by_lua_block { require('cas').forceAuthentication() }
    fastcgi_pass ...;
    fastcgi_param REMOTE_USER $http_remote_user;
    ...
  }
  

• only CAS protocol v2
• no CAS proxy
• no CAS single sign out

• this work is based on Toshi Piazza's ngx-http-cas-client-lua
• we could be using ngx.location.capture, but it does not work with HTTP/2.
• with apache mod_auth_cas, you can not protect both in apache and in backend: mod_auth_cas will always validate the ticket, even if its session is valid. The current nginx-auth-cas-lua code does not have this limitation. NB: if the backend ask for proxy tickets, either use a different url to receive pgtIou, or use

if ($remote_addr !~ "^192[.]168[.]1[.](56|57)$") { # if request is from CAS, let it go to the backend unauthenticated (needed for pgtIOU)
    access_by_lua_block { require('cas').forceAuthentication() }
}