1package middleware
2
3import (
4 "encoding/json"
5 "net"
6 "net/http"
7
8 "github.com/bnema/zerowrap"
9
10 "github.com/bnema/gordon/internal/adapters/dto"
11)
12
13// localhostNets contains IPv4 and IPv6 loopback ranges that are always allowed.
14var localhostNets = ParseTrustedProxies([]string{"127.0.0.0/8", "::1"})
15
16// cidrAllowlist is the shared implementation for CIDR-based access control middleware.
17// ipExtractor determines how the client IP is obtained from the request.
18// logLabel is used in the deny log message (e.g. "registry", "proxy origin").
19func cidrAllowlist(allowedNets []*net.IPNet, ipExtractor func(*http.Request) string, logLabel string, log zerowrap.Logger) func(http.Handler) http.Handler {
20 return func(next http.Handler) http.Handler {
21 if len(allowedNets) == 0 {
22 return next
23 }
24 return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
25 clientIP := ipExtractor(r)
26
27 if IsTrustedProxy(clientIP, localhostNets) {
28 next.ServeHTTP(w, r)
29 return
30 }
31
32 if IsTrustedProxy(clientIP, allowedNets) {
33 next.ServeHTTP(w, r)
34 return
35 }
36
37 log.Warn().
38 Str(zerowrap.FieldLayer, "adapter").
39 Str(zerowrap.FieldAdapter, "http").
40 Str(zerowrap.FieldMethod, r.Method).
41 Str(zerowrap.FieldClientIP, clientIP).
42 Msgf("%s access denied by CIDR allowlist", logLabel)
43
44 w.Header().Set("Content-Type", "application/json")
45 w.WriteHeader(http.StatusForbidden)
46 _ = json.NewEncoder(w).Encode(dto.ErrorResponse{Error: "Forbidden"})
47 })
48 }
49}
50
51// RegistryCIDRAllowlist returns middleware that restricts access to the given CIDR ranges.
52// Localhost is always allowed so Gordon can pull from its own registry.
53// An empty allowedNets slice is a no-op (all traffic passes through).
54func RegistryCIDRAllowlist(allowedNets, trustedNets []*net.IPNet, log zerowrap.Logger) func(http.Handler) http.Handler {
55 return cidrAllowlist(allowedNets, func(r *http.Request) string {
56 return GetClientIP(r, trustedNets)
57 }, "registry", log)
58}
59
60// ProxyCIDRAllowlist returns middleware that restricts proxy access to the given CIDR ranges.
61// This validates the direct network peer (RemoteAddr), not forwarded IPs, to ensure only
62// trusted sources (e.g. Cloudflare edge IPs) can reach the proxy server.
63// An empty allowedNets slice is a no-op (all traffic passes through).
64func ProxyCIDRAllowlist(allowedNets []*net.IPNet, log zerowrap.Logger) func(http.Handler) http.Handler {
65 return cidrAllowlist(allowedNets, func(r *http.Request) string {
66 remoteIP, _, err := net.SplitHostPort(r.RemoteAddr)
67 if err != nil {
68 return r.RemoteAddr
69 }
70 return remoteIP
71 }, "proxy origin", log)
72}