Goloris - slowloris[1] for nginx DoS

FAQ

• Features

  • Uses as low network bandwidth as possible.
  • Low CPU and memory usage.
  • Automatically and silently eats all the available TCP connections to the server.
  • Supports https.
  • Easily hackable thanks to clear and concise Go syntax and powerful Golang features.

• Limitations

  • Can eat up to 64K TCP connections from a single IP due to TCP limitations. Just use proxies if you want overcoming this limitation :)

• How it works?

  It tries occupying and keeping busy as much tcp connections to the victim as possible by using as low network bandwidth as possible. If goloris is lucky enough, then eventually it should eat all the available connections to the victim, so no other client could connect to it. See the source code for more insights.

• How quickly it can take down unprotected nginx with default settings?

  In a few minutes with default config options.

• Which versions of nginx are vulnerable?

  All up to 1.5.9 if unprotected as described below (i.e. with default config).

• How to protect nginx against goloris?

  I know the following options:

  • Limit the number of simultaneous TCP connections from the same source ip. See, for example, connlimit in iptables or http://nginx.org/en/docs/http/ngx_http_limit_conn_module.html
  • Deny POST requests.
  • Patch nginx, so it drops connection if the client sends POST body at very slow rate.

• How to use it?

  go get -u -a github.com/valyala/goloris
  go build github.com/valyala/goloris
  ./goloris -help
  

P.S. Don't forget adjusting ulimit -n before experimenting.

And remember - goloris is published for educational purposes only.

[1] http://ha.ckers.org/slowloris/