98 lines
2.9 KiB
Go
98 lines
2.9 KiB
Go
// Package realip extracts a real IP address from the request.
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package realip
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import (
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"bytes"
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"fmt"
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"net"
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"net/http"
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"strings"
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)
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type ipRange struct {
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start net.IP
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end net.IP
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}
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// privateRanges contains the list of private and special-use IP ranges.
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// reference: https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml
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var privateRanges = []ipRange{
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// IPv4 Private Ranges
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{start: net.ParseIP("10.0.0.0"), end: net.ParseIP("10.255.255.255")},
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{start: net.ParseIP("172.16.0.0"), end: net.ParseIP("172.31.255.255")},
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{start: net.ParseIP("192.168.0.0"), end: net.ParseIP("192.168.255.255")},
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// IPv4 Link-Local
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{start: net.ParseIP("169.254.0.0"), end: net.ParseIP("169.254.255.255")},
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// IPv4 Shared Address Space (RFC 6598)
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{start: net.ParseIP("100.64.0.0"), end: net.ParseIP("100.127.255.255")},
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// IPv4 Benchmarking (RFC 2544)
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{start: net.ParseIP("198.18.0.0"), end: net.ParseIP("198.19.255.255")},
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// IPv6 Unique Local Addresses (ULA)
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{start: net.ParseIP("fc00::"), end: net.ParseIP("fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")},
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// IPv6 Link-local Addresses
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{start: net.ParseIP("fe80::"), end: net.ParseIP("febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff")},
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}
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// Get returns real ip from the given request
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// Prioritize public IPs over private IPs
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func Get(r *http.Request) (string, error) {
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var firstIP string
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for _, h := range []string{"X-Forwarded-For", "X-Real-Ip"} {
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addresses := strings.Split(r.Header.Get(h), ",")
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for i := len(addresses) - 1; i >= 0; i-- {
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ip := strings.TrimSpace(addresses[i])
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realIP := net.ParseIP(ip)
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if firstIP == "" && realIP != nil {
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firstIP = ip
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}
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// Guard against nil realIP
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if realIP == nil || !realIP.IsGlobalUnicast() || isPrivateSubnet(realIP) {
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continue
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}
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return ip, nil
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}
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}
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if firstIP != "" {
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return firstIP, nil
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}
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// handle RemoteAddr which may be just an IP or IP:port
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remoteIP := r.RemoteAddr
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// try to extract host from host:port format
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host, _, err := net.SplitHostPort(remoteIP)
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if err == nil {
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remoteIP = host
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}
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// at this point remoteIP could be either:
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// 1. the host part extracted from host:port
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// 2. yhe original RemoteAddr if it doesn't contain a port
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// try to parse it as a valid IP address
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if netIP := net.ParseIP(remoteIP); netIP == nil {
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return "", fmt.Errorf("no valid ip found in %q", r.RemoteAddr)
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}
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return remoteIP, nil
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}
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// isPrivateSubnet - check to see if this ip is in a private subnet
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func isPrivateSubnet(ipAddress net.IP) bool {
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inRange := func(r ipRange, ipAddress net.IP) bool { // check to see if a given ip address is within a range given
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// ensure the IPs are in the same format for comparison
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ipAddress = ipAddress.To16()
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r.start = r.start.To16()
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r.end = r.end.To16()
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return bytes.Compare(ipAddress, r.start) >= 0 && bytes.Compare(ipAddress, r.end) <= 0
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}
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for _, r := range privateRanges {
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if inRange(r, ipAddress) {
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return true
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}
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}
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return false
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}
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