fix: handle bare IPv6 addresses in proxy protocol header (fixes minekube#670) (minekube#673)

When a client connects via IPv6 through Connect, the address string
(e.g. "2a09:bac6:d73f:28::4:31d") has no brackets or port.
net.SplitHostPort returns "too many colons in address" for this format,
which was unhandled, causing splitHostPort to return an empty host and
triggering a panic in protoutil.convert.

Author: robinbraemer

pkg/edition/java/internal/protoutil/util_test.go

@@ -22,20 +22,29 @@ func TestProxyHeader(t *testing.T) {
 		Port: 25566,
 	}
 
+	// Bare IPv6 addresses without brackets and port (as reported in issue #670)
+	bareIPv6Src := connect.Addr("2a09:bac6:d73f:28::4:31d")
+	bareIPv6Src2 := connect.Addr("2a09:bac6:d73f:3046::4cf:74")
+
 	testCases := []struct {
-		name     string
-		srcAddr  net.Addr
-		destAddr net.Addr
+		name           string
+		srcAddr        net.Addr
+		destAddr       net.Addr
+		skipStrCompare bool // bare IPv6 addr strings differ from net.TCPAddr strings
 	}{
-		{"virtual addr should not fail to write proxy header", srcAddr, destAddr},
-		{"mix of v4 and v6 should not fail to write proxy header", v4Addr, v6Addr},
-		{"mix of v6 and v4 should not fail to write proxy header", v6Addr, v4Addr},
-		{"v4 addr should not fail to write proxy header", v4Addr, v4Addr},
-		{"v6 addr should not fail to write proxy header", v6Addr, v6Addr},
-		{"mix of v4 and virtual should not fail to write proxy header", v4Addr, destAddr},
-		{"mix of v6 and virtual should not fail to write proxy header", v6Addr, destAddr},
-		{"mix of virtual and v4 should not fail to write proxy header", srcAddr, v4Addr},
-		{"mix of virtual and v6 should not fail to write proxy header", srcAddr, v6Addr},
+		{"virtual addr should not fail to write proxy header", srcAddr, destAddr, false},
+		{"mix of v4 and v6 should not fail to write proxy header", v4Addr, v6Addr, false},
+		{"mix of v6 and v4 should not fail to write proxy header", v6Addr, v4Addr, false},
+		{"v4 addr should not fail to write proxy header", v4Addr, v4Addr, false},
+		{"v6 addr should not fail to write proxy header", v6Addr, v6Addr, false},
+		{"mix of v4 and virtual should not fail to write proxy header", v4Addr, destAddr, false},
+		{"mix of v6 and virtual should not fail to write proxy header", v6Addr, destAddr, false},
+		{"mix of virtual and v4 should not fail to write proxy header", srcAddr, v4Addr, false},
+		{"mix of virtual and v6 should not fail to write proxy header", srcAddr, v6Addr, false},
+		{"bare IPv6 src should not panic", bareIPv6Src, destAddr, true},
+		{"bare IPv6 src2 should not panic", bareIPv6Src2, destAddr, true},
+		{"bare IPv6 src with v4 dest should not panic", bareIPv6Src, v4Addr, true},
+		{"bare IPv6 src with v6 dest should not panic", bareIPv6Src, v6Addr, true},
 	}
 
 	for _, tc := range testCases {
@@ -44,8 +53,10 @@ func TestProxyHeader(t *testing.T) {
 			require.NotNil(t, header)
 			require.NotNil(t, header.SourceAddr)
 			require.NotNil(t, header.DestinationAddr)
-			require.Equal(t, tc.srcAddr.String(), header.SourceAddr.String())
-			require.Equal(t, tc.destAddr.String(), header.DestinationAddr.String())
+			if !tc.skipStrCompare {
+				require.Equal(t, tc.srcAddr.String(), header.SourceAddr.String())
+				require.Equal(t, tc.destAddr.String(), header.DestinationAddr.String())
+			}
 
 			// Create a buffer to write the header
 			buf := new(bytes.Buffer)

pkg/util/netutil/util.go

@@ -56,7 +56,7 @@ func splitHostPort(addr string) (host string, port uint16, err error) {
 	host, portStr, err = net.SplitHostPort(addr)
 	if err == nil {
 		portInt, err = strconv.Atoi(portStr)
-	} else if isMissingPortErr(err) {
+	} else if isMissingPortErr(err) || isTooManyColonsErr(err) {
 		host = addr
 		err = nil
 	}
@@ -74,3 +74,8 @@ func isMissingPortErr(err error) bool {
 	var addrErr *net.AddrError
 	return err != nil && errors.As(err, &addrErr) && addrErr.Err == "missing port in address"
 }
+
+func isTooManyColonsErr(err error) bool {
+	var addrErr *net.AddrError
+	return err != nil && errors.As(err, &addrErr) && addrErr.Err == "too many colons in address"
+}

pkg/util/netutil/util_test.go

@@ -28,3 +28,27 @@ func TestSplitHostPort_isMissingPortErr(t *testing.T) {
 	_, _, err := net.SplitHostPort("host-without-port")
 	require.True(t, isMissingPortErr(err))
 }
+
+func TestHostPort_BareIPv6(t *testing.T) {
+	// Bare IPv6 addresses without brackets and port (e.g. from connect.Addr)
+	// should return the full address as host with port 0.
+	tests := []struct {
+		addr string
+		host string
+		port uint16
+	}{
+		{"2a09:bac6:d73f:28::4:31d", "2a09:bac6:d73f:28::4:31d", 0},
+		{"2a09:bac6:d73f:3046::4cf:74", "2a09:bac6:d73f:3046::4cf:74", 0},
+		{"::1", "::1", 0},
+		{"[::1]:25565", "::1", 25565},
+		{"127.0.0.1:25565", "127.0.0.1", 25565},
+	}
+	for _, tc := range tests {
+		t.Run(tc.addr, func(t *testing.T) {
+			addr := &address{addr: tc.addr}
+			host, port := HostPort(addr)
+			require.Equal(t, tc.host, host)
+			require.Equal(t, tc.port, port)
+		})
+	}
+}