Enabling CORS in HAProxy

blog20190830-01.cfg

frontend www
    bind :80

    # Add a response header
    http-response add-header X-XSS-Protection "1; mode=block"

    # Remove a response header
    http-response del-header X-Powered-By

    # Change a response header
    http-response set-header Via "HTTP/2.0 haproxy1"
    default_backend webservers

blog20190830-02.sh

$ haproxy -vv | grep Lua
Built with Lua version: Lua 5.3.5

blog20190830-03.cfg

global
    lua-load /etc/haproxy/cors.lua

blog20190830-04.sh

Origin: http://example.com

blog20190830-05.cfg

listen api
    bind :80
    http-request lua.cors "GET,PUT,POST" "example.com" "*"
    http-response lua.cors 
    server s1 192.168.50.20 check
    server s2 192.168.50.21 check
    server s3 192.168.50.22 check