Unverified Commit 118e3bc0 authored by Minseong Choi's avatar Minseong Choi 💬
Browse files

fix(rcon): refuse an oversize command before its length wraps

parent 3922aae9

internal/rcon/rcon.go

+5 −3
Changes for internal/rcon/rcon.go: 5 added lines, 3 removed lines.
Original line number Diff line number Diff line
@@ -211,11 +211,13 @@ func (c *Conn) nextID() int32 { 
// writePacket encodes one RCON packet: little-endian length, id, type, the

// null-terminated body, and a trailing null byte.

func writePacket(w io.Writer, id, typ int32, body string) error {

	// Bounded on the body, before the int32 conversion: one past 2 GiB would

	// wrap the length negative and slip under a check made after it.

	if len(body) > maxPacketLen-minPacketLen {

		return fmt.Errorf("rcon: outgoing packet too large: %d bytes", len(body)+minPacketLen)

	}

	bodyBytes := []byte(body)

	length := int32(4 + 4 + len(bodyBytes) + 2)

	if length > maxPacketLen {

		return fmt.Errorf("rcon: outgoing packet too large: %d bytes", length)

	}

	buf := make([]byte, 0, 4+length)

	buf = appendInt32(buf, length)

	buf = appendInt32(buf, id)

internal/rcon/rcon_test.go

+21 −0
Changes for internal/rcon/rcon_test.go: 21 added lines, 0 removed lines.
Original line number Diff line number Diff line
@@ -169,6 +169,27 @@ func TestDialAndExecute(t *testing.T) { 
	}

}



// A command goes out in one packet of at most 4096 bytes; a longer one is

// refused before anything is sent.

func TestExecuteRefusesAnOversizeCommand(t *testing.T) {

	longest := strings.Repeat("a", 4096-10) // 10: id, type, two terminators

	f := startFakeRCON(t, "s3cret", map[string]string{longest: "ok"})

	defer f.stop()



	c, err := rcon.Dial(f.addr(), "s3cret", 2*time.Second)

	if err != nil {

		t.Fatalf("Dial: %v", err)

	}

	defer c.Close()



	if got, err := c.Execute(longest); err != nil || got != "ok" {

		t.Fatalf("Execute(%d bytes) = %q, %v; want ok", len(longest), got, err)

	}

	if _, err := c.Execute(longest + "a"); err == nil || !strings.Contains(err.Error(), "too large") {

		t.Fatalf("Execute(%d bytes) err = %v, want the too-large refusal", len(longest)+1, err)

	}

}



func TestDialAuthFailure(t *testing.T) {

	f := startFakeRCON(t, "correct-horse", nil)

	defer f.stop()