Malicious RDP server security fixes

This commit includes fixes for a set of 21 vulnerabilities in
rdesktop when a malicious RDP server is used.

All vulnerabilities was identified and reported by Eyal Itkin.

 * Add rdp_protocol_error function that is used in several fixes
 * Refactor of process_bitmap_updates
 * Fix possible integer overflow in s_check_rem() on 32bit arch
 * Fix memory corruption in process_bitmap_data - CVE-2018-8794
 * Fix remote code execution in process_bitmap_data - CVE-2018-8795
 * Fix remote code execution in process_plane - CVE-2018-8797
 * Fix Denial of Service in mcs_recv_connect_response - CVE-2018-20175
 * Fix Denial of Service in mcs_parse_domain_params - CVE-2018-20175
 * Fix Denial of Service in sec_parse_crypt_info - CVE-2018-20176
 * Fix Denial of Service in sec_recv - CVE-2018-20176
 * Fix minor information leak in rdpdr_process - CVE-2018-8791
 * Fix Denial of Service in cssp_read_tsrequest - CVE-2018-8792
 * Fix remote code execution in cssp_read_tsrequest - CVE-2018-8793
 * Fix Denial of Service in process_bitmap_data - CVE-2018-8796
 * Fix minor information leak in rdpsnd_process_ping - CVE-2018-8798
 * Fix Denial of Service in process_secondary_order - CVE-2018-8799
 * Fix remote code execution in in ui_clip_handle_data - CVE-2018-8800
 * Fix major information leak in ui_clip_handle_data - CVE-2018-20174
 * Fix memory corruption in rdp_in_unistr - CVE-2018-20177
 * Fix Denial of Service in process_demand_active - CVE-2018-20178
 * Fix remote code execution in lspci_process - CVE-2018-20179
 * Fix remote code execution in rdpsnddbg_process - CVE-2018-20180
 * Fix remote code execution in seamless_process - CVE-2018-20181
 * Fix remote code execution in seamless_process_line - CVE-2018-20182
process_pointer_pdu(STREAM s)
{
	uint16 message_type;
	uint16 x, y;

	logger(Protocol, Debug, "%s()", __func__);

	in_uint16_le(s, message_type);
	in_uint8s(s, 2);	/* pad */

	switch (message_type)
	{
		case RDP_POINTER_MOVE:
			in_uint16_le(s, x);
			in_uint16_le(s, y);
			if (s_check(s))
				ui_move_pointer(x, y);
			break;

		case RDP_POINTER_COLOR:
			process_colour_pointer_pdu(s);
			break;

		case RDP_POINTER_CACHED:
			process_cached_pointer_pdu(s);
			break;

		case RDP_POINTER_SYSTEM:
			process_system_pointer_pdu(s);
			break;

		case RDP_POINTER_NEW:
			process_new_pointer_pdu(s);
			break;

		default:
			logger(Protocol, Warning,
			       "process_pointer_pdu(), unhandled message type 0x%x", message_type);
 	}
 }

process_pointer_pdu(STREAM s)
{
	uint16 message_type;
	uint16 x, y;

	logger(Protocol, Debug, "%s()", __func__);

	in_uint16_le(s, message_type);
	in_uint8s(s, 2);	/* pad */

	switch (message_type)
	{
		case RDP_POINTER_MOVE:
			in_uint16_le(s, x);
			in_uint16_le(s, y);
			if (s_check(s))
				ui_move_pointer(x, y);
			break;

		case RDP_POINTER_COLOR:
			process_colour_pointer_pdu(s);
			break;

		case RDP_POINTER_CACHED:
			process_cached_pointer_pdu(s);
			break;

		case RDP_POINTER_SYSTEM:
			process_system_pointer_pdu(s);
			break;

		case RDP_POINTER_NEW:
			process_new_pointer_pdu(s);
			break;

		default:
			logger(Protocol, Warning,
			       "process_pointer_pdu(), unhandled message type 0x%x", message_type);
 	}
 }
