fix(outbound): ignore IPv6 zone identifiers when classifying addresses

pkg/gotenberg/outbound.go

@@ -109,11 +109,18 @@ var nonPublicIPv4Prefixes = []netip.Prefix{
 // the prefixes themselves are deprecated or translation-only. See
 // [nonPublicIPv6Prefixes] and [nonPublicIPv4Prefixes] for the full lists
 // and rationale.
+//
+// An IPv6 zone identifier is ignored, so [::%1] classifies the same as [::].
 func IsPublicIP(addr netip.Addr) bool {
 	if !addr.IsValid() {
 		return false
 	}
-	addr = addr.Unmap()
+	// A zone does not change where a non-link-local address routes, but
+	// [netip.Prefix.Contains] never matches a zoned address and
+	// [netip.Addr.IsUnspecified] compares the zone too. Keeping it would let
+	// http://[::%251]/ or any zoned address in the prefixes below pass as
+	// public.
+	addr = addr.WithZone("").Unmap()
 	switch {
 	case addr.IsLoopback(),
 		addr.IsPrivate(),

pkg/gotenberg/outbound_test.go

@@ -103,6 +103,23 @@ func TestIsPublicIP(t *testing.T) {
 
 		// Discard prefix (RFC 6666).
 		{"100::1", false},
+
+		// A zone identifier must not change the classification.
+		{"::%1", false},
+		{"::%lo", false},
+		{"::1%1", false},
+		{"fe80::1%eth0", false},
+		{"fc00::1%1", false},
+		{"::ffff:127.0.0.1%1", false},
+		{"fec0::1%eth0", false},
+		{"2002:a9fe:a9fe::%1", false},
+		{"2001:0:abcd:ef12:3456:7890:a9fe:a9fe%1", false},
+		{"64:ff9b::a9fe:a9fe%1", false},
+		{"64:ff9b:1::a9fe:a9fe%1", false},
+		{"::a9fe:a9fe%1", false},
+		{"2001:db8::1%1", false},
+		{"100::1%1", false},
+		{"2606:4700:4700::1111%1", true},
 	} {
 		t.Run(tc.addr, func(t *testing.T) {
 			addr, err := netip.ParseAddr(tc.addr)
@@ -304,6 +321,22 @@ func TestFilterOutboundURL(t *testing.T) {
 			expectErr: true,
 			expectIs:  ErrFiltered,
 		},
+		{
+			scenario:  "zoned unspecified address blocked with deny-private-ips",
+			rawURL:    "http://[::%251]:9999/",
+			deny:      defaultDeny,
+			opts:      []DecideOption{WithDenyPrivateIPs(true)},
+			expectErr: true,
+			expectIs:  ErrFiltered,
+		},
+		{
+			scenario:  "zoned site-local address blocked with deny-private-ips",
+			rawURL:    "http://[fec0:1234::3%25eth0]:8080/",
+			deny:      defaultDeny,
+			opts:      []DecideOption{WithDenyPrivateIPs(true)},
+			expectErr: true,
+			expectIs:  ErrFiltered,
+		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
 			if tc.stub != nil {