[deliverable/linux.git] / net / netfilter / xt_tcpudp.c

#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");

#ifdef DEBUG_IP_FIREWALL_USER
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif


/* 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;

	duprintf("tcp_match: 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, const struct net_device *in,
       const struct net_device *out, const struct xt_match *match,
       const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
{
	const struct tcphdr *th;
	struct tcphdr _tcph;
	const struct xt_tcp *tcpinfo = matchinfo;

	if (offset) {
		/* 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 (offset == 1) {
			duprintf("Dropping evil TCP offset=1 frag.\n");
			*hotdrop = true;
		}
		/* Must not be a fragment. */
		return false;
	}

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

	th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
	if (th == NULL) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		duprintf("Dropping evil TCP offset=0 tinygram.\n");
		*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)) {
			*hotdrop = true;
			return false;
		}
		if (!tcp_find_option(tcpinfo->option, skb, protoff,
				     th->doff*4 - sizeof(_tcph),
				     tcpinfo->invflags & XT_TCP_INV_OPTION,
				     hotdrop))
			return false;
	}
	return true;
}

/* Called when user tries to insert an entry of this type. */
static bool
tcp_mt_check(const char *tablename, const void *info,
             const struct xt_match *match, void *matchinfo,
             unsigned int hook_mask)
{
	const struct xt_tcp *tcpinfo = matchinfo;

	/* Must specify no unknown invflags */
	return !(tcpinfo->invflags & ~XT_TCP_INV_MASK);
}

static bool
udp_mt(const struct sk_buff *skb, const struct net_device *in,
       const struct net_device *out, const struct xt_match *match,
       const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
{
	const struct udphdr *uh;
	struct udphdr _udph;
	const struct xt_udp *udpinfo = matchinfo;

	/* Must not be a fragment. */
	if (offset)
		return false;

	uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph);
	if (uh == NULL) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		duprintf("Dropping evil UDP tinygram.\n");
		*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));
}

/* Called when user tries to insert an entry of this type. */
static bool
udp_mt_check(const char *tablename, const void *info,
             const struct xt_match *match, void *matchinfo,
             unsigned int hook_mask)
{
	const struct xt_udp *udpinfo = matchinfo;

	/* Must specify no unknown invflags */
	return !(udpinfo->invflags & ~XT_UDP_INV_MASK);
}

static struct xt_match tcpudp_mt_reg[] __read_mostly = {
	{
		.name		= "tcp",
		.family		= AF_INET,
		.checkentry	= tcp_mt_check,
		.match		= tcp_mt,
		.matchsize	= sizeof(struct xt_tcp),
		.proto		= IPPROTO_TCP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "tcp",
		.family		= AF_INET6,
		.checkentry	= tcp_mt_check,
		.match		= tcp_mt,
		.matchsize	= sizeof(struct xt_tcp),
		.proto		= IPPROTO_TCP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udp",
		.family		= AF_INET,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udp",
		.family		= AF_INET6,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDP,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udplite",
		.family		= AF_INET,
		.checkentry	= udp_mt_check,
		.match		= udp_mt,
		.matchsize	= sizeof(struct xt_udp),
		.proto		= IPPROTO_UDPLITE,
		.me		= THIS_MODULE,
	},
	{
		.name		= "udplite",
		.family		= AF_INET6,
		.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
2e4e6a17 HW	1	#include <linux/types.h>
	2	#include <linux/module.h>
	3	#include <net/ip.h>
37d8dc82	4	#include <linux/ipv6.h>
2e4e6a17 HW	5	#include <net/ipv6.h>
	6	#include <net/tcp.h>
	7	#include <net/udp.h>
	8	#include <linux/netfilter/x_tables.h>
	9	#include <linux/netfilter/xt_tcpudp.h>
	10	#include <linux/netfilter_ipv4/ip_tables.h>
	11	#include <linux/netfilter_ipv6/ip6_tables.h>
	12
2ae15b64	13	MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
2e4e6a17 HW	14	MODULE_LICENSE("GPL");
	15	MODULE_ALIAS("xt_tcp");
	16	MODULE_ALIAS("xt_udp");
	17	MODULE_ALIAS("ipt_udp");
	18	MODULE_ALIAS("ipt_tcp");
	19	MODULE_ALIAS("ip6t_udp");
	20	MODULE_ALIAS("ip6t_tcp");
	21
	22	#ifdef DEBUG_IP_FIREWALL_USER
	23	#define duprintf(format, args...) printk(format , ## args)
	24	#else
	25	#define duprintf(format, args...)
	26	#endif
	27
	28
	29	/* Returns 1 if the port is matched by the range, 0 otherwise */
1d93a9cb JE	30	static inline bool
1d93a9cb JE	31	port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
2e4e6a17	32	{
1d93a9cb	33	return (port >= min && port <= max) ^ invert;
2e4e6a17 HW	34	}
2e4e6a17 HW	35
1d93a9cb	36	static bool
2e4e6a17 HW	37	tcp_find_option(u_int8_t option,
	38	const struct sk_buff *skb,
	39	unsigned int protoff,
	40	unsigned int optlen,
1d93a9cb	41	bool invert,
cff533ac	42	bool *hotdrop)
2e4e6a17 HW	43	{
2e4e6a17 HW	44	/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
3cf93c96 JE	45	const u_int8_t *op;
3cf93c96 JE	46	u_int8_t _opt[60 - sizeof(struct tcphdr)];
2e4e6a17 HW	47	unsigned int i;
	48
	49	duprintf("tcp_match: finding option\n");
	50
	51	if (!optlen)
	52	return invert;
	53
	54	/* If we don't have the whole header, drop packet. */
	55	op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
	56	optlen, _opt);
	57	if (op == NULL) {
cff533ac	58	*hotdrop = true;
1d93a9cb	59	return false;
2e4e6a17 HW	60	}
	61
	62	for (i = 0; i < optlen; ) {
	63	if (op[i] == option) return !invert;
	64	if (op[i] < 2) i++;
	65	else i += op[i+1]?:1;
	66	}
	67
	68	return invert;
	69	}
	70
1d93a9cb	71	static bool
d3c5ee6d JE	72	tcp_mt(const struct sk_buff skb, const struct net_device in,
	73	const struct net_device out, const struct xt_match match,
	74	const void matchinfo, int offset, unsigned int protoff, bool hotdrop)
2e4e6a17	75	{
3cf93c96 JE	76	const struct tcphdr *th;
3cf93c96 JE	77	struct tcphdr _tcph;
2e4e6a17 HW	78	const struct xt_tcp *tcpinfo = matchinfo;
	79
	80	if (offset) {
	81	/* To quote Alan:
	82
	83	Don't allow a fragment of TCP 8 bytes in. Nobody normal
	84	causes this. Its a cracker trying to break in by doing a
	85	flag overwrite to pass the direction checks.
	86	*/
	87	if (offset == 1) {
	88	duprintf("Dropping evil TCP offset=1 frag.\n");
cff533ac	89	*hotdrop = true;
2e4e6a17 HW	90	}
2e4e6a17 HW	91	/* Must not be a fragment. */
1d93a9cb	92	return false;
2e4e6a17 HW	93	}
2e4e6a17 HW	94
7c4e36bc	95	#define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))
2e4e6a17 HW	96
	97	th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
	98	if (th == NULL) {
	99	/* We've been asked to examine this packet, and we
	100	can't. Hence, no choice but to drop. */
	101	duprintf("Dropping evil TCP offset=0 tinygram.\n");
cff533ac	102	*hotdrop = true;
1d93a9cb	103	return false;
2e4e6a17 HW	104	}
	105
	106	if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
	107	ntohs(th->source),
	108	!!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
1d93a9cb	109	return false;
2e4e6a17 HW	110	if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
	111	ntohs(th->dest),
	112	!!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
1d93a9cb	113	return false;
2e4e6a17 HW	114	if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
	115	== tcpinfo->flg_cmp,
	116	XT_TCP_INV_FLAGS))
1d93a9cb	117	return false;
2e4e6a17 HW	118	if (tcpinfo->option) {
2e4e6a17 HW	119	if (th->doff * 4 < sizeof(_tcph)) {
cff533ac	120	*hotdrop = true;
1d93a9cb	121	return false;
2e4e6a17 HW	122	}
	123	if (!tcp_find_option(tcpinfo->option, skb, protoff,
	124	th->doff*4 - sizeof(_tcph),
	125	tcpinfo->invflags & XT_TCP_INV_OPTION,
	126	hotdrop))
1d93a9cb	127	return false;
2e4e6a17	128	}
1d93a9cb	129	return true;
2e4e6a17 HW	130	}
	131
	132	/* Called when user tries to insert an entry of this type. */
ccb79bdc	133	static bool
d3c5ee6d JE	134	tcp_mt_check(const char tablename, const void info,
	135	const struct xt_match match, void matchinfo,
	136	unsigned int hook_mask)
2e4e6a17	137	{
2e4e6a17 HW	138	const struct xt_tcp *tcpinfo = matchinfo;
2e4e6a17 HW	139
5d04bff0 PM	140	/* Must specify no unknown invflags */
5d04bff0 PM	141	return !(tcpinfo->invflags & ~XT_TCP_INV_MASK);
2e4e6a17 HW	142	}
2e4e6a17 HW	143
1d93a9cb	144	static bool
d3c5ee6d JE	145	udp_mt(const struct sk_buff skb, const struct net_device in,
	146	const struct net_device out, const struct xt_match match,
	147	const void matchinfo, int offset, unsigned int protoff, bool hotdrop)
2e4e6a17	148	{
3cf93c96 JE	149	const struct udphdr *uh;
3cf93c96 JE	150	struct udphdr _udph;
2e4e6a17 HW	151	const struct xt_udp *udpinfo = matchinfo;
	152
	153	/* Must not be a fragment. */
	154	if (offset)
1d93a9cb	155	return false;
2e4e6a17 HW	156
	157	uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph);
	158	if (uh == NULL) {
	159	/* We've been asked to examine this packet, and we
	160	can't. Hence, no choice but to drop. */
	161	duprintf("Dropping evil UDP tinygram.\n");
cff533ac	162	*hotdrop = true;
1d93a9cb	163	return false;
2e4e6a17 HW	164	}
	165
	166	return port_match(udpinfo->spts[0], udpinfo->spts[1],
	167	ntohs(uh->source),
	168	!!(udpinfo->invflags & XT_UDP_INV_SRCPT))
	169	&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
	170	ntohs(uh->dest),
	171	!!(udpinfo->invflags & XT_UDP_INV_DSTPT));
	172	}
	173
	174	/* Called when user tries to insert an entry of this type. */
ccb79bdc	175	static bool
d3c5ee6d JE	176	udp_mt_check(const char tablename, const void info,
	177	const struct xt_match match, void matchinfo,
	178	unsigned int hook_mask)
2e4e6a17	179	{
a289d70d	180	const struct xt_udp *udpinfo = matchinfo;
2e4e6a17	181
5d04bff0 PM	182	/* Must specify no unknown invflags */
5d04bff0 PM	183	return !(udpinfo->invflags & ~XT_UDP_INV_MASK);
2e4e6a17 HW	184	}
2e4e6a17 HW	185
d3c5ee6d	186	static struct xt_match tcpudp_mt_reg[] __read_mostly = {
4470bbc7 PM	187	{
	188	.name = "tcp",
	189	.family = AF_INET,
d3c5ee6d JE	190	.checkentry = tcp_mt_check,
d3c5ee6d JE	191	.match = tcp_mt,
4470bbc7 PM	192	.matchsize = sizeof(struct xt_tcp),
	193	.proto = IPPROTO_TCP,
	194	.me = THIS_MODULE,
	195	},
	196	{
	197	.name = "tcp",
	198	.family = AF_INET6,
d3c5ee6d JE	199	.checkentry = tcp_mt_check,
d3c5ee6d JE	200	.match = tcp_mt,
4470bbc7 PM	201	.matchsize = sizeof(struct xt_tcp),
	202	.proto = IPPROTO_TCP,
	203	.me = THIS_MODULE,
	204	},
	205	{
	206	.name = "udp",
	207	.family = AF_INET,
d3c5ee6d JE	208	.checkentry = udp_mt_check,
d3c5ee6d JE	209	.match = udp_mt,
4470bbc7 PM	210	.matchsize = sizeof(struct xt_udp),
	211	.proto = IPPROTO_UDP,
	212	.me = THIS_MODULE,
	213	},
	214	{
	215	.name = "udp",
	216	.family = AF_INET6,
d3c5ee6d JE	217	.checkentry = udp_mt_check,
d3c5ee6d JE	218	.match = udp_mt,
4470bbc7 PM	219	.matchsize = sizeof(struct xt_udp),
	220	.proto = IPPROTO_UDP,
	221	.me = THIS_MODULE,
	222	},
ba4e58ec GR	223	{
	224	.name = "udplite",
	225	.family = AF_INET,
d3c5ee6d JE	226	.checkentry = udp_mt_check,
d3c5ee6d JE	227	.match = udp_mt,
ba4e58ec GR	228	.matchsize = sizeof(struct xt_udp),
	229	.proto = IPPROTO_UDPLITE,
	230	.me = THIS_MODULE,
	231	},
	232	{
	233	.name = "udplite",
	234	.family = AF_INET6,
d3c5ee6d JE	235	.checkentry = udp_mt_check,
d3c5ee6d JE	236	.match = udp_mt,
ba4e58ec GR	237	.matchsize = sizeof(struct xt_udp),
	238	.proto = IPPROTO_UDPLITE,
	239	.me = THIS_MODULE,
	240	},
2e4e6a17 HW	241	};
2e4e6a17 HW	242
d3c5ee6d	243	static int __init tcpudp_mt_init(void)
2e4e6a17	244	{
d3c5ee6d	245	return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
2e4e6a17 HW	246	}
2e4e6a17 HW	247
d3c5ee6d	248	static void __exit tcpudp_mt_exit(void)
2e4e6a17	249	{
d3c5ee6d	250	xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
2e4e6a17 HW	251	}
2e4e6a17 HW	252
d3c5ee6d JE	253	module_init(tcpudp_mt_init);
d3c5ee6d JE	254	module_exit(tcpudp_mt_exit);