/
ip_finder.go
101 lines (89 loc) · 2.34 KB
/
ip_finder.go
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package gz
// Code originally taken from
// https://husobee.github.io/golang/ip-address/2015/12/17/remote-ip-go.html
import (
"bytes"
"net"
"net/http"
"strings"
)
// ipRange is a structure that holds the start and end of a range of
// ip addresses
type ipRange struct {
start net.IP
end net.IP
}
// private ranges lists IP ranges that are considered private or local
// addresses
var privateRanges = []ipRange{
{
start: net.ParseIP("10.0.0.0"),
end: net.ParseIP("10.255.255.255"),
},
{
start: net.ParseIP("100.64.0.0"),
end: net.ParseIP("100.127.255.255"),
},
{
start: net.ParseIP("172.16.0.0"),
end: net.ParseIP("172.31.255.255"),
},
{
start: net.ParseIP("192.0.0.0"),
end: net.ParseIP("192.0.0.255"),
},
{
start: net.ParseIP("192.168.0.0"),
end: net.ParseIP("192.168.255.255"),
},
{
start: net.ParseIP("198.18.0.0"),
end: net.ParseIP("198.19.255.255"),
},
}
// inRange checks to see if a given ip address is within a range given
func inRange(r ipRange, ipAddress net.IP) bool {
// strcmp type byte comparison
if bytes.Compare(ipAddress, r.start) >= 0 &&
bytes.Compare(ipAddress, r.end) < 0 {
return true
}
return false
}
// isPrivateSubnet checks to see if this ip is in a private subnet
func isPrivateSubnet(ipAddress net.IP) bool {
// my use case is only concerned with ipv4 atm
if ipCheck := ipAddress.To4(); ipCheck != nil {
// iterate over all our ranges
for _, r := range privateRanges {
// check if this ip is in a private range
if inRange(r, ipAddress) {
return true
}
}
}
return false
}
// ///////////////////////////////////////////////
// / getIPAddress searches, from right to left, for a valid IP address in a
// / request.
func getIPAddress(r *http.Request) string {
// Search over possible headers.
for _, h := range []string{"X-Forwarded-For", "X-Real-Ip"} {
// Number of addresses in the header
addresses := strings.Split(r.Header.Get(h), ",")
// March from right to left until we get a public address
// that will be the address right before our proxy.
for i := len(addresses) - 1; i >= 0; i-- {
ip := strings.TrimSpace(addresses[i])
// header can contain spaces too, strip those out.
realIP := net.ParseIP(ip)
if !realIP.IsGlobalUnicast() || isPrivateSubnet(realIP) {
// bad address, go to next
continue
}
return ip
}
}
return ""
}