refactor: loopback detection

This adjusts the behaviour of loopback network address detection to utilize the appropriate stdlib functionality.

authorize_helper.go

@@ -7,8 +7,8 @@ import (
 	"context"
 	"html/template"
 	"io"
+	"net"
 	"net/url"
-	"regexp"
 	"strings"
 
 	"authelia.com/provider/oauth2/internal/consts"
@@ -129,7 +129,7 @@ func isMatchingAsLoopback(requested *url.URL, registeredURI string) bool {
 	//
 	// Source: https://datatracker.ietf.org/doc/html/rfc8252#section-7.3
 	if requested.Scheme == "http" &&
-		isLoopbackAddress(requested.Host) &&
+		isLoopbackAddress(requested) &&
 		registered.Hostname() == requested.Hostname() &&
 		// The port is skipped here - see codedoc above!
 		registered.Path == requested.Path &&
@@ -140,14 +140,14 @@ func isMatchingAsLoopback(requested *url.URL, registeredURI string) bool {
 	return false
 }
 
-var (
-	regexLoopbackAddress = regexp.MustCompile(`^(127\.0\.0\.1|\[::1])(:\d+)?$`)
-)
-
 // Check if address is either an IPv4 loopback or an IPv6 loopback-
 // An optional port is ignored
-func isLoopbackAddress(address string) bool {
-	return regexLoopbackAddress.MatchString(address)
+func isLoopbackAddress(uri *url.URL) bool {
+	if uri == nil {
+		return false
+	}
+
+	return net.ParseIP(uri.Hostname()).IsLoopback()
 }
 
 // IsValidRedirectURI validates a redirect_uri as specified in:
@@ -185,7 +185,8 @@ func IsRedirectURISecureStrict(redirectURI *url.URL) bool {
 
 func IsLocalhost(redirectURI *url.URL) bool {
 	hn := redirectURI.Hostname()
-	return strings.HasSuffix(hn, ".localhost") || hn == "127.0.0.1" || hn == "::1" || hn == "localhost"
+
+	return strings.HasSuffix(hn, ".localhost") || hn == "localhost" || isLoopbackAddress(redirectURI)
 }
 
 func WriteAuthorizeFormPostResponse(redirectURL string, parameters url.Values, template *template.Template, rw io.Writer) {

authorize_helper_whitebox_test.go

@@ -4,9 +4,11 @@
 package oauth2
 
 import (
+	"net/url"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestIsLookbackAddress(t *testing.T) {
@@ -17,53 +19,42 @@ func TestIsLookbackAddress(t *testing.T) {
 	}{
 		{
 			"ShouldReturnTrueIPv4Loopback",
-			"127.0.0.1",
-			true,
-		},
-		{
-			"ShouldReturnTrueIPv4LoopbackWithPort",
-			"127.0.0.1:1230",
+			"http://127.0.0.1:1235",
 			true,
 		},
 		{
 			"ShouldReturnTrueIPv6Loopback",
-			"[::1]",
+			"http://[::1]:1234",
 			true,
 		},
 		{
-			"ShouldReturnTrueIPv6LoopbackWithPort",
-			"[::1]:1230",
-			true,
-		}, {
 			"ShouldReturnFalse12700255",
-			"127.0.0.255",
-			false,
+			"https://127.0.0.255",
+			true,
 		},
 		{
-			"ShouldReturnFalse12700255WithPort",
-			"127.0.0.255:1230",
-			false,
+			"ShouldReturnTrue127.0.0.255",
+			"https://127.0.0.255",
+			true,
 		},
 		{
 			"ShouldReturnFalseInvalidFourthOctet",
-			"127.0.0.11230",
+			"https://127.0.0.11230",
 			false,
 		},
 		{
 			"ShouldReturnFalseInvalidIPv4",
-			"127x0x0x11230",
-			false,
-		},
-		{
-			"ShouldReturnFalseInvalidIPv6",
-			"[::1]1230",
+			"https://127x0x0x11230",
 			false,
 		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			assert.Equal(t, tc.expected, isLoopbackAddress(tc.have))
+			have, err := url.Parse(tc.have)
+
+			require.NoError(t, err)
+			assert.Equal(t, tc.expected, isLoopbackAddress(have))
 		})
 	}
 }