Commit message: network plugin: Fix heap overflow in parse_packet().

Emilien Gaspar has identified a heap overflow in parse_packet(), the
function used by the network plugin to parse incoming network packets.

This is a vulnerability in collectd, though the scope is not clear at
this point. At the very least specially crafted network packets can be
used to crash the daemon. We can't rule out a potential remote code
execution though.

Fixes: CVE-2016-6254
CVE: CVE-2016-6254
CWE: CWE-119
Vulnerability description: Heap-based buffer overflow in the parse_packet function in network.c in collectd before 5.4.3 and 5.x before 5.5.2 allows remote attackers to cause a denial of service (daemon crash) or possibly execute arbitrary code via a crafted network packet.

Project: collectd
File: network.c

static int parse_packet (sockent_t *se, /* {{{ */
		void *buffer, size_t buffer_size, int flags,
		const char *username)
{
	int status;

	value_list_t vl = VALUE_LIST_INIT;
	notification_t n;

#if HAVE_LIBGCRYPT
	int packet_was_signed = (flags & PP_SIGNED);
        int packet_was_encrypted = (flags & PP_ENCRYPTED);
	int printed_ignore_warning = 0;
#endif /* HAVE_LIBGCRYPT */


	memset (&vl, '\0', sizeof (vl));
	memset (&n, '\0', sizeof (n));
	status = 0;

	while ((status == 0) && (0 < buffer_size)
			&& ((unsigned int) buffer_size > sizeof (part_header_t)))
	{
		uint16_t pkg_length;
		uint16_t pkg_type;

		memcpy ((void *) &pkg_type,
				(void *) buffer,
				sizeof (pkg_type));
		memcpy ((void *) &pkg_length,
				(void *) (buffer + sizeof (pkg_type)),
				sizeof (pkg_length));

		pkg_length = ntohs (pkg_length);
		pkg_type = ntohs (pkg_type);

		if (pkg_length > buffer_size)
			break;
		/* Ensure that this loop terminates eventually */
		if (pkg_length < (2 * sizeof (uint16_t)))
			break;

		if (pkg_type == TYPE_ENCR_AES256)
		{
			status = parse_part_encr_aes256 (se,
					&buffer, &buffer_size, flags);
			if (status != 0)
			{
				ERROR ("network plugin: Decrypting AES256 "
						"part failed "
						"with status %i.", status);
				break;
			}
		}
#if HAVE_LIBGCRYPT
		else if ((se->data.server.security_level == SECURITY_LEVEL_ENCRYPT)
				&& (packet_was_encrypted == 0))
		{
			if (printed_ignore_warning == 0)
			{
				INFO ("network plugin: Unencrypted packet or "
						"part has been ignored.");
 				printed_ignore_warning = 1;
 			}
 			buffer = ((char *) buffer) + pkg_length;
			buffer_size -= (size_t) pkg_length;
 			continue;
 		}
 #endif /* HAVE_LIBGCRYPT */
		else if (pkg_type == TYPE_SIGN_SHA256)
		{
			status = parse_part_sign_sha256 (se,
                                        &buffer, &buffer_size, flags);
			if (status != 0)
			{
				ERROR ("network plugin: Verifying HMAC-SHA-256 "
						"signature failed "
						"with status %i.", status);
				break;
			}
		}
#if HAVE_LIBGCRYPT
		else if ((se->data.server.security_level == SECURITY_LEVEL_SIGN)
				&& (packet_was_encrypted == 0)
				&& (packet_was_signed == 0))
		{
			if (printed_ignore_warning == 0)
			{
				INFO ("network plugin: Unsigned packet or "
						"part has been ignored.");
 				printed_ignore_warning = 1;
 			}
 			buffer = ((char *) buffer) + pkg_length;
			buffer_size -= (size_t) pkg_length;
 			continue;
 		}
 #endif /* HAVE_LIBGCRYPT */
		else if (pkg_type == TYPE_VALUES)
		{
			status = parse_part_values (&buffer, &buffer_size,
					&vl.values, &vl.values_len);
			if (status != 0)
				break;

			network_dispatch_values (&vl, username);

			sfree (vl.values);
		}
		else if (pkg_type == TYPE_TIME)
		{
			uint64_t tmp = 0;
			status = parse_part_number (&buffer, &buffer_size,
					&tmp);
			if (status == 0)
			{
				vl.time = TIME_T_TO_CDTIME_T (tmp);
				n.time  = TIME_T_TO_CDTIME_T (tmp);
			}
		}
		else if (pkg_type == TYPE_TIME_HR)
		{
			uint64_t tmp = 0;
			status = parse_part_number (&buffer, &buffer_size,
					&tmp);
			if (status == 0)
			{
				vl.time = (cdtime_t) tmp;
				n.time  = (cdtime_t) tmp;
			}
		}
		else if (pkg_type == TYPE_INTERVAL)
		{
			uint64_t tmp = 0;
			status = parse_part_number (&buffer, &buffer_size,
					&tmp);
			if (status == 0)
				vl.interval = TIME_T_TO_CDTIME_T (tmp);
		}
		else if (pkg_type == TYPE_INTERVAL_HR)
		{
			uint64_t tmp = 0;
			status = parse_part_number (&buffer, &buffer_size,
					&tmp);
			if (status == 0)
				vl.interval = (cdtime_t) tmp;
		}
		else if (pkg_type == TYPE_HOST)
		{
			status = parse_part_string (&buffer, &buffer_size,
					vl.host, sizeof (vl.host));
			if (status == 0)
				sstrncpy (n.host, vl.host, sizeof (n.host));
		}
		else if (pkg_type == TYPE_PLUGIN)
		{
			status = parse_part_string (&buffer, &buffer_size,
					vl.plugin, sizeof (vl.plugin));
			if (status == 0)
				sstrncpy (n.plugin, vl.plugin,
						sizeof (n.plugin));
		}
		else if (pkg_type == TYPE_PLUGIN_INSTANCE)
		{
			status = parse_part_string (&buffer, &buffer_size,
					vl.plugin_instance,
					sizeof (vl.plugin_instance));
			if (status == 0)
				sstrncpy (n.plugin_instance,
						vl.plugin_instance,
						sizeof (n.plugin_instance));
		}
		else if (pkg_type == TYPE_TYPE)
		{
			status = parse_part_string (&buffer, &buffer_size,
					vl.type, sizeof (vl.type));
			if (status == 0)
				sstrncpy (n.type, vl.type, sizeof (n.type));
		}
		else if (pkg_type == TYPE_TYPE_INSTANCE)
		{
			status = parse_part_string (&buffer, &buffer_size,
					vl.type_instance,
					sizeof (vl.type_instance));
			if (status == 0)
				sstrncpy (n.type_instance, vl.type_instance,
						sizeof (n.type_instance));
		}
		else if (pkg_type == TYPE_MESSAGE)
		{
			status = parse_part_string (&buffer, &buffer_size,
					n.message, sizeof (n.message));

			if (status != 0)
			{
				/* do nothing */
			}
			else if ((n.severity != NOTIF_FAILURE)
					&& (n.severity != NOTIF_WARNING)
					&& (n.severity != NOTIF_OKAY))
			{
				INFO ("network plugin: "
						"Ignoring notification with "
						"unknown severity %i.",
						n.severity);
			}
			else if (n.time <= 0)
			{
				INFO ("network plugin: "
						"Ignoring notification with "
						"time == 0.");
			}
			else if (strlen (n.message) <= 0)
			{
				INFO ("network plugin: "
						"Ignoring notification with "
						"an empty message.");
			}
			else
			{
				network_dispatch_notification (&n);
			}
		}
		else if (pkg_type == TYPE_SEVERITY)
		{
			uint64_t tmp = 0;
			status = parse_part_number (&buffer, &buffer_size,
					&tmp);
			if (status == 0)
				n.severity = (int) tmp;
		}
		else
		{
 			DEBUG ("network plugin: parse_packet: Unknown part"
 					" type: 0x%04hx", pkg_type);
 			buffer = ((char *) buffer) + pkg_length;
			buffer_size -= (size_t) pkg_length;
 		}
 	} /* while (buffer_size > sizeof (part_header_t)) */
 
	if (status == 0 && buffer_size > 0)
		WARNING ("network plugin: parse_packet: Received truncated "
				"packet, try increasing `MaxPacketSize'");

	return (status);
} /* }}} int parse_packet */