[mirror_ubuntu-artful-kernel.git] / net / netfilter / xt_tcpudp.c

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/types.h>
#include <linux/module.h>
#include <net/ip.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_tcpudp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>

MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xt_tcp");
MODULE_ALIAS("xt_udp");
MODULE_ALIAS("ipt_udp");
MODULE_ALIAS("ipt_tcp");
MODULE_ALIAS("ip6t_udp");
MODULE_ALIAS("ip6t_tcp");

/* Returns 1 if the port is matched by the range, 0 otherwise */
static inline bool
port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
{
	return (port >= min && port <= max) ^ invert;
}

static bool
tcp_find_option(u_int8_t option,
		const struct sk_buff *skb,
		unsigned int protoff,
		unsigned int optlen,
		bool invert,
		bool *hotdrop)
{
	/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
	const u_int8_t *op;
	u_int8_t _opt[60 - sizeof(struct tcphdr)];
	unsigned int i;

	pr_debug("finding option\n");

	if (!optlen)
		return invert;

	/* If we don't have the whole header, drop packet. */
	op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
				optlen, _opt);
	if (op == NULL) {
		*hotdrop = true;
		return false;
	}

	for (i = 0; i < optlen; ) {
		if (op[i] == option) return !invert;
		if (op[i] < 2) i++;
		else i += op[i+1]?:1;
	}

	return invert;
}

static bool tcp_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
	const struct tcphdr *th;
	struct tcphdr _tcph;
	const struct xt_tcp *tcpinfo = par->matchinfo;

	if (par->fragoff != 0) {
		/* To quote Alan:

		   Don't allow a fragment of TCP 8 bytes in. Nobody normal
		   causes this. Its a cracker trying to break in by doing a
		   flag overwrite to pass the direction checks.
		*/
		if (par->fragoff == 1) {
			pr_debug("Dropping evil TCP offset=1 frag.\n");
			par->hotdrop = true;
		}
		/* Must not be a fragment. */
		return false;
	}

#define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))

	th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
	if (th == NULL) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		pr_debug("Dropping evil TCP offset=0 tinygram.\n");
		par->hotdrop = true;
		return false;
	}

	if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
			ntohs(th->source),
			!!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
		return false;
	if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
			ntohs(th->dest),
			!!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
		return false;
	if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
		      == tcpinfo->flg_cmp,
		      XT_TCP_INV_FLAGS))
		return false;
	if (tcpinfo->option) {
		if (th->doff * 4 < sizeof(_tcph)) {
			par->hotdrop = true;
			return false;
		}
		if (!tcp_find_option(tcpinfo->option, skb, par->thoff,
				     th->doff*4 - sizeof(_tcph),
				     tcpinfo->invflags & XT_TCP_INV_OPTION,
				     &par->hotdrop))
			return false;
	}
	return true;
}

static int tcp_mt_check(const struct xt_mtchk_param *par)
{
	const struct xt_tcp *tcpinfo = par->matchinfo;

	/* Must specify no unknown invflags */
	return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0;
}

static bool udp_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
	const struct udphdr *uh;
	struct udphdr _udph;
	const struct xt_udp *udpinfo = par->matchinfo;

	/* Must not be a fragment. */
	if (par->fragoff != 0)
		return false;

	uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
	if (uh == NULL) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		pr_debug("Dropping evil UDP tinygram.\n");
		par->hotdrop = true;
		return false;
	}

	return port_match(udpinfo->spts[0], udpinfo->spts[1],
			  ntohs(uh->source),
			  !!(udpinfo->invflags & XT_UDP_INV_SRCPT))
		&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
			      ntohs(uh->dest),
			      !!(udpinfo->invflags & XT_UDP_INV_DSTPT));
}

static int udp_mt_check(const struct xt_mtchk_param *par)
{
	const struct xt_udp *udpinfo = par->matchinfo;

	/* Must specify no unknown invflags */
	return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0;
}

static struct xt_match tcpudp_mt_reg[] __read_mostly = {
	{
		.name		= "tcp",
		.family		= NFPROTO_IPV4,
		.checkentry	= tcp_mt_check,
		.match		= tcp_mt,
		.matchsize	= sizeof(struct xt_tcp),
		.proto		= IPPROTO_TCP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "tcp",
		.family		= NFPROTO_IPV6,
		.checkentry	= tcp_mt_check,
		.match		= tcp_mt,
		.matchsize	= sizeof(struct xt_tcp),
		.proto		= IPPROTO_TCP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udp",
		.family		= NFPROTO_IPV4,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udp",
		.family		= NFPROTO_IPV6,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udplite",
		.family		= NFPROTO_IPV4,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDPLITE,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udplite",
		.family		= NFPROTO_IPV6,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDPLITE,
		.me		= THIS_MODULE,
	},
};

static int __init tcpudp_mt_init(void)
{
	return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
}

static void __exit tcpudp_mt_exit(void)
{
	xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
}

module_init(tcpudp_mt_init);
module_exit(tcpudp_mt_exit);
Commit	Line	Data
	1	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
	2	#include <linux/types.h>
	3	#include <linux/module.h>
	4	#include <net/ip.h>
	5	#include <linux/ipv6.h>
	6	#include <net/ipv6.h>
	7	#include <net/tcp.h>
	8	#include <net/udp.h>
	9	#include <linux/netfilter/x_tables.h>
	10	#include <linux/netfilter/xt_tcpudp.h>
	11	#include <linux/netfilter_ipv4/ip_tables.h>
	12	#include <linux/netfilter_ipv6/ip6_tables.h>
	13
	14	MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
	15	MODULE_LICENSE("GPL");
	16	MODULE_ALIAS("xt_tcp");
	17	MODULE_ALIAS("xt_udp");
	18	MODULE_ALIAS("ipt_udp");
	19	MODULE_ALIAS("ipt_tcp");
	20	MODULE_ALIAS("ip6t_udp");
	21	MODULE_ALIAS("ip6t_tcp");
	22
	23	/* Returns 1 if the port is matched by the range, 0 otherwise */
	24	static inline bool
	25	port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
	26	{
	27	return (port >= min && port <= max) ^ invert;
	28	}
	29
	30	static bool
	31	tcp_find_option(u_int8_t option,
	32	const struct sk_buff *skb,
	33	unsigned int protoff,
	34	unsigned int optlen,
	35	bool invert,
	36	bool *hotdrop)
	37	{
	38	/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
	39	const u_int8_t *op;
	40	u_int8_t _opt[60 - sizeof(struct tcphdr)];
	41	unsigned int i;
	42
	43	pr_debug("finding option\n");
	44
	45	if (!optlen)
	46	return invert;
	47
	48	/* If we don't have the whole header, drop packet. */
	49	op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
	50	optlen, _opt);
	51	if (op == NULL) {
	52	*hotdrop = true;
	53	return false;
	54	}
	55
	56	for (i = 0; i < optlen; ) {
	57	if (op[i] == option) return !invert;
	58	if (op[i] < 2) i++;
	59	else i += op[i+1]?:1;
	60	}
	61
	62	return invert;
	63	}
	64
	65	static bool tcp_mt(const struct sk_buff skb, struct xt_action_param par)
	66	{
	67	const struct tcphdr *th;
	68	struct tcphdr _tcph;
	69	const struct xt_tcp *tcpinfo = par->matchinfo;
	70
	71	if (par->fragoff != 0) {
	72	/* To quote Alan:
	73
	74	Don't allow a fragment of TCP 8 bytes in. Nobody normal
	75	causes this. Its a cracker trying to break in by doing a
	76	flag overwrite to pass the direction checks.
	77	*/
	78	if (par->fragoff == 1) {
	79	pr_debug("Dropping evil TCP offset=1 frag.\n");
	80	par->hotdrop = true;
	81	}
	82	/* Must not be a fragment. */
	83	return false;
	84	}
	85
	86	#define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))
	87
	88	th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
	89	if (th == NULL) {
	90	/* We've been asked to examine this packet, and we
	91	can't. Hence, no choice but to drop. */
	92	pr_debug("Dropping evil TCP offset=0 tinygram.\n");
	93	par->hotdrop = true;
	94	return false;
	95	}
	96
	97	if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
	98	ntohs(th->source),
	99	!!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
	100	return false;
	101	if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
	102	ntohs(th->dest),
	103	!!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
	104	return false;
	105	if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
	106	== tcpinfo->flg_cmp,
	107	XT_TCP_INV_FLAGS))
	108	return false;
	109	if (tcpinfo->option) {
	110	if (th->doff * 4 < sizeof(_tcph)) {
	111	par->hotdrop = true;
	112	return false;
	113	}
	114	if (!tcp_find_option(tcpinfo->option, skb, par->thoff,
	115	th->doff*4 - sizeof(_tcph),
	116	tcpinfo->invflags & XT_TCP_INV_OPTION,
	117	&par->hotdrop))
	118	return false;
	119	}
	120	return true;
	121	}
	122
	123	static int tcp_mt_check(const struct xt_mtchk_param *par)
	124	{
	125	const struct xt_tcp *tcpinfo = par->matchinfo;
	126
	127	/* Must specify no unknown invflags */
	128	return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0;
	129	}
	130
	131	static bool udp_mt(const struct sk_buff skb, struct xt_action_param par)
	132	{
	133	const struct udphdr *uh;
	134	struct udphdr _udph;
	135	const struct xt_udp *udpinfo = par->matchinfo;
	136
	137	/* Must not be a fragment. */
	138	if (par->fragoff != 0)
	139	return false;
	140
	141	uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
	142	if (uh == NULL) {
	143	/* We've been asked to examine this packet, and we
	144	can't. Hence, no choice but to drop. */
	145	pr_debug("Dropping evil UDP tinygram.\n");
	146	par->hotdrop = true;
	147	return false;
	148	}
	149
	150	return port_match(udpinfo->spts[0], udpinfo->spts[1],
	151	ntohs(uh->source),
	152	!!(udpinfo->invflags & XT_UDP_INV_SRCPT))
	153	&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
	154	ntohs(uh->dest),
	155	!!(udpinfo->invflags & XT_UDP_INV_DSTPT));
	156	}
	157
	158	static int udp_mt_check(const struct xt_mtchk_param *par)
	159	{
	160	const struct xt_udp *udpinfo = par->matchinfo;
	161
	162	/* Must specify no unknown invflags */
	163	return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0;
	164	}
	165
	166	static struct xt_match tcpudp_mt_reg[] __read_mostly = {
	167	{
	168	.name = "tcp",
	169	.family = NFPROTO_IPV4,
	170	.checkentry = tcp_mt_check,
	171	.match = tcp_mt,
	172	.matchsize = sizeof(struct xt_tcp),
	173	.proto = IPPROTO_TCP,
	174	.me = THIS_MODULE,
	175	},
	176	{
	177	.name = "tcp",
	178	.family = NFPROTO_IPV6,
	179	.checkentry = tcp_mt_check,
	180	.match = tcp_mt,
	181	.matchsize = sizeof(struct xt_tcp),
	182	.proto = IPPROTO_TCP,
	183	.me = THIS_MODULE,
	184	},
	185	{
	186	.name = "udp",
	187	.family = NFPROTO_IPV4,
	188	.checkentry = udp_mt_check,
	189	.match = udp_mt,
	190	.matchsize = sizeof(struct xt_udp),
	191	.proto = IPPROTO_UDP,
	192	.me = THIS_MODULE,
	193	},
	194	{
	195	.name = "udp",
	196	.family = NFPROTO_IPV6,
	197	.checkentry = udp_mt_check,
	198	.match = udp_mt,
	199	.matchsize = sizeof(struct xt_udp),
	200	.proto = IPPROTO_UDP,
	201	.me = THIS_MODULE,
	202	},
	203	{
	204	.name = "udplite",
	205	.family = NFPROTO_IPV4,
	206	.checkentry = udp_mt_check,
	207	.match = udp_mt,
	208	.matchsize = sizeof(struct xt_udp),
	209	.proto = IPPROTO_UDPLITE,
	210	.me = THIS_MODULE,
	211	},
	212	{
	213	.name = "udplite",
	214	.family = NFPROTO_IPV6,
	215	.checkentry = udp_mt_check,
	216	.match = udp_mt,
	217	.matchsize = sizeof(struct xt_udp),
	218	.proto = IPPROTO_UDPLITE,
	219	.me = THIS_MODULE,
	220	},
	221	};
	222
	223	static int __init tcpudp_mt_init(void)
	224	{
	225	return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
	226	}
	227
	228	static void __exit tcpudp_mt_exit(void)
	229	{
	230	xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
	231	}
	232
	233	module_init(tcpudp_mt_init);
	234	module_exit(tcpudp_mt_exit);