feat: more elaborate XFF compute (#350)

* feat: more elaborate XFF compute #328 followup now featuring configuration and defaults that shouldn't break most setups. fixes #344 * refactor: obvious condition eval order optimization * feat: add StripLLU implementation * chore: I'm sorry it's 7 AM * test: add test environment for unix socket serving Signed-off-by: Xe Iaso <me@xeiaso.net> * test(unix-socket-xff): comment out the shell script more Signed-off-by: Xe Iaso <me@xeiaso.net> * fix(internal): fix logic bug in XFF computation, add tests Signed-off-by: Xe Iaso <me@xeiaso.net> * fix(internal): prevent panic in local testing Signed-off-by: Xe Iaso <me@xeiaso.net> * fix(internal): shuffle around return values to flow better Signed-off-by: Xe Iaso <me@xeiaso.net> --------- Signed-off-by: Xe Iaso <me@xeiaso.net> Co-authored-by: Xe Iaso <me@xeiaso.net>
2025-04-25 13:59:55 +02:00 · 2025-04-25 13:59:55 +02:00 · a420db8b8a
commit a420db8b8a
parent 5a4f68d384
8 changed files with 619 additions and 22 deletions
--- a/internal/xff_test.go
+++ b/internal/xff_test.go
@ -0,0 +1,166 @@
+package internal
+
+import (
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestXForwardedForUpdateIgnoreUnix(t *testing.T) {
+	var remoteAddr = ""
+	var xff = ""
+
+	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		remoteAddr = r.RemoteAddr
+		xff = r.Header.Get("X-Forwarded-For")
+		w.WriteHeader(http.StatusOK)
+	})
+
+	r := httptest.NewRequest(http.MethodGet, "/", nil)
+
+	r.RemoteAddr = "@"
+
+	w := httptest.NewRecorder()
+
+	XForwardedForUpdate(h).ServeHTTP(w, r)
+
+	if r.RemoteAddr != remoteAddr {
+		t.Errorf("wanted remoteAddr to be %s, got: %s", r.RemoteAddr, remoteAddr)
+	}
+
+	if xff != "" {
+		t.Error("handler added X-Forwarded-For when it should not have")
+	}
+}
+
+func TestXForwardedForUpdateAddToChain(t *testing.T) {
+	var xff = ""
+	const expected = "1.1.1.1"
+
+	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		xff = r.Header.Get("X-Forwarded-For")
+		w.WriteHeader(http.StatusOK)
+	})
+
+	srv := httptest.NewServer(XForwardedForUpdate(h))
+
+	r, err := http.NewRequest(http.MethodGet, srv.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	r.Header.Set("X-Forwarded-For", "1.1.1.1,10.20.30.40")
+
+	if _, err := srv.Client().Do(r); err != nil {
+		t.Fatal(err)
+	}
+
+	if xff != expected {
+		t.Logf("expected: %s", expected)
+		t.Logf("got:      %s", xff)
+		t.Error("X-Forwarded-For header was not what was expected")
+	}
+}
+
+func TestComputeXFFHeader(t *testing.T) {
+	for _, tt := range []struct {
+		name          string
+		remoteAddr    string
+		origXFFHeader string
+		pref          XFFComputePreferences
+		result        string
+		err           error
+	}{
+		{
+			name:          "StripPrivate",
+			remoteAddr:    "127.0.0.1:80",
+			origXFFHeader: "1.1.1.1,10.0.0.1",
+			pref: XFFComputePreferences{
+				StripPrivate: true,
+			},
+			result: "1.1.1.1,127.0.0.1",
+		},
+		{
+			name:          "StripLoopback",
+			remoteAddr:    "127.0.0.1:80",
+			origXFFHeader: "1.1.1.1,10.0.0.1,127.0.0.1",
+			pref: XFFComputePreferences{
+				StripLoopback: true,
+			},
+			result: "1.1.1.1,10.0.0.1",
+		},
+		{
+			name:          "StripCGNAT",
+			remoteAddr:    "100.64.0.1:80",
+			origXFFHeader: "1.1.1.1,10.0.0.1,100.64.0.1",
+			pref: XFFComputePreferences{
+				StripCGNAT: true,
+			},
+			result: "1.1.1.1,10.0.0.1",
+		},
+		{
+			name:          "StripLinkLocalUnicastIPv4",
+			remoteAddr:    "169.254.0.1:80",
+			origXFFHeader: "1.1.1.1,10.0.0.1,169.254.0.1",
+			pref: XFFComputePreferences{
+				StripLLU: true,
+			},
+			result: "1.1.1.1,10.0.0.1",
+		},
+		{
+			name:          "StripLinkLocalUnicastIPv6",
+			remoteAddr:    "169.254.0.1:80",
+			origXFFHeader: "1.1.1.1,10.0.0.1,fe80::",
+			pref: XFFComputePreferences{
+				StripLLU: true,
+			},
+			result: "1.1.1.1,10.0.0.1",
+		},
+		{
+			name:          "Flatten",
+			remoteAddr:    "127.0.0.1:80",
+			origXFFHeader: "1.1.1.1,10.0.0.1,fe80::,100.64.0.1,169.254.0.1",
+			pref: XFFComputePreferences{
+				StripPrivate:  true,
+				StripLoopback: true,
+				StripCGNAT:    true,
+				StripLLU:      true,
+				Flatten:       true,
+			},
+			result: "1.1.1.1",
+		},
+		{
+			name:       "invalid-ip-port",
+			remoteAddr: "fe80::",
+			err:        ErrCantSplitHostParse,
+		},
+		{
+			name:       "invalid-remote-ip",
+			remoteAddr: "anubis:80",
+			err:        ErrCantParseRemoteIP,
+		},
+		{
+			name:       "no-xff-dont-panic",
+			remoteAddr: "127.0.0.1:80",
+			pref: XFFComputePreferences{
+				StripPrivate:  true,
+				StripLoopback: true,
+				StripCGNAT:    true,
+				StripLLU:      true,
+				Flatten:       true,
+			},
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := computeXFFHeader(tt.remoteAddr, tt.origXFFHeader, tt.pref)
+			if err != nil && !errors.Is(err, tt.err) {
+				t.Errorf("computeXFFHeader got the wrong error, wanted %v but got: %v", tt.err, err)
+			}
+
+			if result != tt.result {
+				t.Errorf("computeXFFHeader returned the wrong result, wanted %q but got: %q", tt.result, result)
+			}
+		})
+	}
+}