ipfilter

A package for IP Filtering in Go (golang)

Install

go get github.com/jpillora/ipfilter

Features

• Simple
• Thread-safe
• IPv4 / IPv6 support
• Subnet support
• Location filtering (via GeoLite2)
• Simple HTTP middleware

Usage

Country-block HTTP middleware

h := http.Handler(...)
myProtectedHandler := ipfilter.Wrap(h, ipfilter.Options{
    //block requests from China and Russia by IP
    BlockedCountries: []string{"CN", "RU"},
})
http.ListenAndServe(":8080", myProtectedHandler)

Country-block stand-alone

f, err := ipfilter.New(ipfilter.Options{
    BlockedCountries: []string{"CN"},
})

f.Blocked("116.31.116.51") //=> true (CN)
f.Allowed("216.58.199.67") //=> true (US)

Async allow LAN hosts middleware

f, err := ipfilter.New(ipfilter.Options{
    BlockByDefault: true,
})

go func() {
	time.Sleep(15 * time.Second)
	//react to admin change....
	f.AllowIP("192.168.0.23")
}()

h := http.Handler(...)
myProtectedHandler := f.Wrap(h)
http.ListenAndServe(":8080", myProtectedHandler)

Allow your entire LAN only

f, err := ipfilter.New(ipfilter.Options{
    AllowedIPs: []string{"192.168.0.0/24"},
    BlockByDefault: true,
})
//only allow 192.168.0.X IPs
f.Allowed("192.168.0.42") //=> true
f.Allowed("10.0.0.42") //=> false

... and with dynamic list updates

//and allow 10.X.X.X
f.AllowIP("10.0.0.0/8")
f.Allowed("10.0.0.42") //=> true
f.Allowed("203.25.111.68") //=> false
//and allow everyone in Australia
f.AllowCountry("AU")
f.Allowed("203.25.111.68") //=> true

Check with net.IP

f.NetAllowed(net.IP{203,25,111,68}) //=> true

Low-level single IP to country

f.IPToCountry("203.25.111.68") //=> "AU"
f.NetIPToCountry(net.IP{203,25,111,68}) //=> "AU"

Advanced HTTP middleware

Make your own with:

func (m *myMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	//use remote addr as it cant be spoofed
	ip, _, _ := net.SplitHostPort(r.RemoteAddr)
	//show simple forbidden text
	if !m.IPFilter.Allowed(ip) {
		http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
		return
	}
	//success!
	m.next.ServeHTTP(w, r)
}

Issues

• Due to the nature of IP address allocation, determining location based of a single IP address is quite difficult (if you're not Google) and is therefore not very reliable. For this reason BlockByDefault is off by default.
• IP DB lookups take on the order of 5µs to perform, though the initial load from disk into memory takes takes about 350ms so be wary of excessive ipfilter.New use.

Todo

• Use a good algorithm to perform faster prefix matches
• Investigate reliability of other detectable attributes
• Add TOR/anonymizer filter options
• Add great-circle distance filter options (e.g. Allow 500KM radius from code/lat,lon)

Credits

• github.com/oschwald/maxminddb-golang
• This software uses GeoLite2 data created by MaxMind, available from http://www.maxmind.com

MIT License

Copyright © 2016 <dev@jpillora.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.