107 lines
2.7 KiB
Go
107 lines
2.7 KiB
Go
// Copyright (c) 2026 Probo Inc <hello@probo.com>.
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice appear in all copies.
|
|
//
|
|
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
|
|
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
|
|
// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
|
|
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
|
|
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
|
|
// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
|
|
// PERFORMANCE OF THIS SOFTWARE.
|
|
|
|
package trustedproxy
|
|
|
|
import (
|
|
"fmt"
|
|
"net"
|
|
"net/http"
|
|
"strings"
|
|
)
|
|
|
|
var forwardedHeaders = []string{
|
|
"Forwarded",
|
|
"X-Forwarded-For",
|
|
}
|
|
|
|
// NewMiddleware returns an HTTP middleware that strips forwarded
|
|
// headers from requests that did not originate from one of the given
|
|
// trusted proxies. Each entry in trusted may be either a single IP
|
|
// address (e.g. "10.0.0.1") or a CIDR range (e.g. "10.0.0.0/24").
|
|
// When the list is empty every request is treated as untrusted and
|
|
// the headers are always removed. An error is returned if any entry
|
|
// is neither a valid IP nor a valid CIDR.
|
|
func NewMiddleware(trusted []string) (func(http.Handler) http.Handler, error) {
|
|
ips, nets, err := parseTrusted(trusted)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return func(next http.Handler) http.Handler {
|
|
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
|
|
if !isTrusted(r.RemoteAddr, ips, nets) {
|
|
for _, h := range forwardedHeaders {
|
|
r.Header.Del(h)
|
|
}
|
|
}
|
|
|
|
next.ServeHTTP(w, r)
|
|
})
|
|
}, nil
|
|
}
|
|
|
|
func parseTrusted(trusted []string) ([]net.IP, []*net.IPNet, error) {
|
|
ips := make([]net.IP, 0, len(trusted))
|
|
|
|
nets := make([]*net.IPNet, 0, len(trusted))
|
|
for _, entry := range trusted {
|
|
if strings.Contains(entry, "/") {
|
|
_, ipNet, err := net.ParseCIDR(entry)
|
|
if err != nil {
|
|
return nil, nil, fmt.Errorf("cannot parse CIDR %q: %w", entry, err)
|
|
}
|
|
|
|
nets = append(nets, ipNet)
|
|
|
|
continue
|
|
}
|
|
|
|
ip := net.ParseIP(entry)
|
|
if ip == nil {
|
|
return nil, nil, fmt.Errorf("cannot parse IP address %q", entry)
|
|
}
|
|
|
|
ips = append(ips, ip)
|
|
}
|
|
|
|
return ips, nets, nil
|
|
}
|
|
|
|
func isTrusted(remoteAddr string, ips []net.IP, nets []*net.IPNet) bool {
|
|
host, _, err := net.SplitHostPort(remoteAddr)
|
|
if err != nil {
|
|
host = remoteAddr
|
|
}
|
|
|
|
ip := net.ParseIP(host)
|
|
if ip == nil {
|
|
return false
|
|
}
|
|
|
|
for _, t := range ips {
|
|
if t.Equal(ip) {
|
|
return true
|
|
}
|
|
}
|
|
|
|
for _, n := range nets {
|
|
if n.Contains(ip) {
|
|
return true
|
|
}
|
|
}
|
|
|
|
return false
|
|
}
|