ip6_tables.c

Linux Kernel 2.6.9 for OMAP1710

	}

	/* Simplifies replace_table code. */
	table->private = &bootstrap;
	if (!replace_table(table, 0, newinfo, &ret))
		goto free_unlock;

	duprintf("table->private->number = %u\n",
		 table->private->number);

	/* save number of initial entries */
	table->private->initial_entries = table->private->number;

	table->lock = RW_LOCK_UNLOCKED;
	list_prepend(&ip6t_tables, table);

 unlock:
	up(&ip6t_mutex);
	return ret;

 free_unlock:
	vfree(newinfo);
	goto unlock;
}

void ip6t_unregister_table(struct ip6t_table *table)
{
	down(&ip6t_mutex);
	LIST_DELETE(&ip6t_tables, table);
	up(&ip6t_mutex);

	/* Decrease module usage counts and free resources */
	IP6T_ENTRY_ITERATE(table->private->entries, table->private->size,
			  cleanup_entry, NULL);
	vfree(table->private);
}

/* Returns 1 if the port is matched by the range, 0 otherwise */
static inline int
port_match(u_int16_t min, u_int16_t max, u_int16_t port, int invert)
{
	int ret;

	ret = (port >= min && port <= max) ^ invert;
	return ret;
}

static int
tcp_find_option(u_int8_t option,
		const struct tcphdr *tcp,
		u_int16_t datalen,
		int invert,
		int *hotdrop)
{
	unsigned int i = sizeof(struct tcphdr);
	const u_int8_t *opt = (u_int8_t *)tcp;

	duprintf("tcp_match: finding option\n");
	/* If we don't have the whole header, drop packet. */
	if (tcp->doff * 4 < sizeof(struct tcphdr) ||
	    tcp->doff * 4 > datalen) {
		*hotdrop = 1;
		return 0;
	}

	while (i < tcp->doff * 4) {
		if (opt[i] == option) return !invert;
		if (opt[i] < 2) i++;
		else i += opt[i+1]?:1;
	}

	return invert;
}

static int
tcp_match(const struct sk_buff *skb,
	  const struct net_device *in,
	  const struct net_device *out,
	  const void *matchinfo,
	  int offset,
	  const void *hdr,
	  u_int16_t datalen,
	  int *hotdrop)
{
	const struct tcphdr *tcp;
	const struct ip6t_tcp *tcpinfo = matchinfo;
	int tcpoff;
	u8 nexthdr = skb->nh.ipv6h->nexthdr;

	/* 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 = 1;
		return 0;
	} else if (offset == 0 && datalen < sizeof(struct tcphdr)) {
		/* 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 = 1;
		return 0;
	}

	tcpoff = (u8*)(skb->nh.ipv6h + 1) - skb->data;
	tcpoff = ipv6_skip_exthdr(skb, tcpoff, &nexthdr, skb->len - tcpoff);
	if (tcpoff < 0 || tcpoff > skb->len) {
		duprintf("tcp_match: cannot skip exthdr. Dropping.\n");
		*hotdrop = 1;
		return 0;
	} else if (nexthdr == IPPROTO_FRAGMENT)
		return 0;
	else if (nexthdr != IPPROTO_TCP ||
		 skb->len - tcpoff < sizeof(struct tcphdr)) {
		/* cannot be occured */
		duprintf("tcp_match: cannot get TCP header. Dropping.\n");
		*hotdrop = 1;
		return 0;
	}

	tcp = (struct tcphdr *)(skb->data + tcpoff);

	/* FIXME: Try tcp doff >> packet len against various stacks --RR */

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

	/* Must not be a fragment. */
	return !offset
		&& port_match(tcpinfo->spts[0], tcpinfo->spts[1],
			      ntohs(tcp->source),
			      !!(tcpinfo->invflags & IP6T_TCP_INV_SRCPT))
		&& port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
			      ntohs(tcp->dest),
			      !!(tcpinfo->invflags & IP6T_TCP_INV_DSTPT))
		&& FWINVTCP((((unsigned char *)tcp)[13]
			     & tcpinfo->flg_mask)
			    == tcpinfo->flg_cmp,
			    IP6T_TCP_INV_FLAGS)
		&& (!tcpinfo->option
		    || tcp_find_option(tcpinfo->option, tcp, datalen,
				       tcpinfo->invflags
				       & IP6T_TCP_INV_OPTION,
				       hotdrop));
}

/* Called when user tries to insert an entry of this type. */
static int
tcp_checkentry(const char *tablename,
	       const struct ip6t_ip6 *ipv6,
	       void *matchinfo,
	       unsigned int matchsize,
	       unsigned int hook_mask)
{
	const struct ip6t_tcp *tcpinfo = matchinfo;

	/* Must specify proto == TCP, and no unknown invflags */
	return ipv6->proto == IPPROTO_TCP
		&& !(ipv6->invflags & IP6T_INV_PROTO)
		&& matchsize == IP6T_ALIGN(sizeof(struct ip6t_tcp))
		&& !(tcpinfo->invflags & ~IP6T_TCP_INV_MASK);
}

static int
udp_match(const struct sk_buff *skb,
	  const struct net_device *in,
	  const struct net_device *out,
	  const void *matchinfo,
	  int offset,
	  const void *hdr,
	  u_int16_t datalen,
	  int *hotdrop)
{
	const struct udphdr *udp;
	const struct ip6t_udp *udpinfo = matchinfo;
	int udpoff;
	u8 nexthdr = skb->nh.ipv6h->nexthdr;

	if (offset == 0 && datalen < sizeof(struct udphdr)) {
		/* 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 = 1;
		return 0;
	}

	udpoff = (u8*)(skb->nh.ipv6h + 1) - skb->data;
	udpoff = ipv6_skip_exthdr(skb, udpoff, &nexthdr, skb->len - udpoff);
	if (udpoff < 0 || udpoff > skb->len) {
		duprintf("udp_match: cannot skip exthdr. Dropping.\n");
		*hotdrop = 1;
		return 0;
	} else if (nexthdr == IPPROTO_FRAGMENT)
		return 0;
	else if (nexthdr != IPPROTO_UDP ||
		 skb->len - udpoff < sizeof(struct udphdr)) {
		duprintf("udp_match: cannot get UDP header. Dropping.\n");
		*hotdrop = 1;
		return 0;
	}

	udp = (struct udphdr *)(skb->data + udpoff);

	/* Must not be a fragment. */
	return !offset
		&& port_match(udpinfo->spts[0], udpinfo->spts[1],
			      ntohs(udp->source),
			      !!(udpinfo->invflags & IP6T_UDP_INV_SRCPT))
		&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
			      ntohs(udp->dest),
			      !!(udpinfo->invflags & IP6T_UDP_INV_DSTPT));
}

/* Called when user tries to insert an entry of this type. */
static int
udp_checkentry(const char *tablename,
	       const struct ip6t_ip6 *ipv6,
	       void *matchinfo,
	       unsigned int matchinfosize,
	       unsigned int hook_mask)
{
	const struct ip6t_udp *udpinfo = matchinfo;

	/* Must specify proto == UDP, and no unknown invflags */
	if (ipv6->proto != IPPROTO_UDP || (ipv6->invflags & IP6T_INV_PROTO)) {
		duprintf("ip6t_udp: Protocol %u != %u\n", ipv6->proto,
			 IPPROTO_UDP);
		return 0;
	}
	if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_udp))) {
		duprintf("ip6t_udp: matchsize %u != %u\n",
			 matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_udp)));
		return 0;
	}
	if (udpinfo->invflags & ~IP6T_UDP_INV_MASK) {
		duprintf("ip6t_udp: unknown flags %X\n",
			 udpinfo->invflags);
		return 0;
	}

	return 1;
}

/* Returns 1 if the type and code is matched by the range, 0 otherwise */
static inline int
icmp6_type_code_match(u_int8_t test_type, u_int8_t min_code, u_int8_t max_code,
		     u_int8_t type, u_int8_t code,
		     int invert)
{
	return (type == test_type && code >= min_code && code <= max_code)
		^ invert;
}

static int
icmp6_match(const struct sk_buff *skb,
	   const struct net_device *in,
	   const struct net_device *out,
	   const void *matchinfo,
	   int offset,
	   const void *hdr,
	   u_int16_t datalen,
	   int *hotdrop)
{
	const struct icmp6hdr *icmp = hdr;
	const struct ip6t_icmp *icmpinfo = matchinfo;

	if (offset == 0 && datalen < 2) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		duprintf("Dropping evil ICMP tinygram.\n");
		*hotdrop = 1;
		return 0;
	}

	/* Must not be a fragment. */
	return !offset
		&& icmp6_type_code_match(icmpinfo->type,
					icmpinfo->code[0],
					icmpinfo->code[1],
					icmp->icmp6_type, icmp->icmp6_code,
					!!(icmpinfo->invflags&IP6T_ICMP_INV));
}

/* Called when user tries to insert an entry of this type. */
static int
icmp6_checkentry(const char *tablename,
	   const struct ip6t_ip6 *ipv6,
	   void *matchinfo,
	   unsigned int matchsize,
	   unsigned int hook_mask)
{
	const struct ip6t_icmp *icmpinfo = matchinfo;

	/* Must specify proto == ICMP, and no unknown invflags */
	return ipv6->proto == IPPROTO_ICMPV6
		&& !(ipv6->invflags & IP6T_INV_PROTO)
		&& matchsize == IP6T_ALIGN(sizeof(struct ip6t_icmp))
		&& !(icmpinfo->invflags & ~IP6T_ICMP_INV);
}

/* The built-in targets: standard (NULL) and error. */
static struct ip6t_target ip6t_standard_target = {
	.name		= IP6T_STANDARD_TARGET,
};

static struct ip6t_target ip6t_error_target = {
	.name		= IP6T_ERROR_TARGET,
	.target		= ip6t_error,
};

static struct nf_sockopt_ops ip6t_sockopts = {
	.pf		= PF_INET6,
	.set_optmin	= IP6T_BASE_CTL,
	.set_optmax	= IP6T_SO_SET_MAX+1,
	.set		= do_ip6t_set_ctl,
	.get_optmin	= IP6T_BASE_CTL,
	.get_optmax	= IP6T_SO_GET_MAX+1,
	.get		= do_ip6t_get_ctl,
};

static struct ip6t_match tcp_matchstruct = {
	.name		= "tcp",
	.match		= &tcp_match,
	.checkentry	= &tcp_checkentry,
};

static struct ip6t_match udp_matchstruct = {
	.name		= "udp",
	.match		= &udp_match,
	.checkentry	= &udp_checkentry,
};

static struct ip6t_match icmp6_matchstruct = {
	.name		= "icmp6",
	.match		= &icmp6_match,
	.checkentry	= &icmp6_checkentry,
};

#ifdef CONFIG_PROC_FS
static inline int print_name(const char *i,
			     off_t start_offset, char *buffer, int length,
			     off_t *pos, unsigned int *count)
{
	if ((*count)++ >= start_offset) {
		unsigned int namelen;

		namelen = sprintf(buffer + *pos, "%s\n",
				  i + sizeof(struct list_head));
		if (*pos + namelen > length) {
			/* Stop iterating */
			return 1;
		}
		*pos += namelen;
	}
	return 0;
}

static inline int print_target(const struct ip6t_target *t,
                               off_t start_offset, char *buffer, int length,
                               off_t *pos, unsigned int *count)
{
	if (t == &ip6t_standard_target || t == &ip6t_error_target)
		return 0;
	return print_name((char *)t, start_offset, buffer, length, pos, count);
}

static int ip6t_get_tables(char *buffer, char **start, off_t offset, int length)
{
	off_t pos = 0;
	unsigned int count = 0;

	if (down_interruptible(&ip6t_mutex) != 0)
		return 0;

	LIST_FIND(&ip6t_tables, print_name, char *,
		  offset, buffer, length, &pos, &count);

	up(&ip6t_mutex);

	/* `start' hack - see fs/proc/generic.c line ~105 */
	*start=(char *)((unsigned long)count-offset);
	return pos;
}

static int ip6t_get_targets(char *buffer, char **start, off_t offset, int length)
{
	off_t pos = 0;
	unsigned int count = 0;

	if (down_interruptible(&ip6t_mutex) != 0)
		return 0;

	LIST_FIND(&ip6t_target, print_target, struct ip6t_target *,
		  offset, buffer, length, &pos, &count);

	up(&ip6t_mutex);

	*start = (char *)((unsigned long)count - offset);
	return pos;
}

static int ip6t_get_matches(char *buffer, char **start, off_t offset, int length)
{
	off_t pos = 0;
	unsigned int count = 0;

	if (down_interruptible(&ip6t_mutex) != 0)
		return 0;

	LIST_FIND(&ip6t_match, print_name, char *,
		  offset, buffer, length, &pos, &count);

	up(&ip6t_mutex);

	*start = (char *)((unsigned long)count - offset);
	return pos;
}

static struct { char *name; get_info_t *get_info; } ip6t_proc_entry[] =
{ { "ip6_tables_names", ip6t_get_tables },
  { "ip6_tables_targets", ip6t_get_targets },
  { "ip6_tables_matches", ip6t_get_matches },
  { NULL, NULL} };
#endif /*CONFIG_PROC_FS*/

static int __init init(void)
{
	int ret;

	/* Noone else will be downing sem now, so we won't sleep */
	down(&ip6t_mutex);
	list_append(&ip6t_target, &ip6t_standard_target);
	list_append(&ip6t_target, &ip6t_error_target);
	list_append(&ip6t_match, &tcp_matchstruct);
	list_append(&ip6t_match, &udp_matchstruct);
	list_append(&ip6t_match, &icmp6_matchstruct);
	up(&ip6t_mutex);

	/* Register setsockopt */
	ret = nf_register_sockopt(&ip6t_sockopts);
	if (ret < 0) {
		duprintf("Unable to register sockopts.\n");
		return ret;
	}

#ifdef CONFIG_PROC_FS
	{
		struct proc_dir_entry *proc;
		int i;

		for (i = 0; ip6t_proc_entry[i].name; i++) {
			proc = proc_net_create(ip6t_proc_entry[i].name, 0,
					       ip6t_proc_entry[i].get_info);
			if (!proc) {
				while (--i >= 0)
				       proc_net_remove(ip6t_proc_entry[i].name);
				nf_unregister_sockopt(&ip6t_sockopts);
				return -ENOMEM;
			}
			proc->owner = THIS_MODULE;
		}
	}
#endif

	printk("ip6_tables: (C) 2000-2002 Netfilter core team\n");
	return 0;
}

static void __exit fini(void)
{
	nf_unregister_sockopt(&ip6t_sockopts);
#ifdef CONFIG_PROC_FS
	{
		int i;
		for (i = 0; ip6t_proc_entry[i].name; i++)
			proc_net_remove(ip6t_proc_entry[i].name);
	}
#endif
}

EXPORT_SYMBOL(ip6t_register_table);
EXPORT_SYMBOL(ip6t_unregister_table);
EXPORT_SYMBOL(ip6t_do_table);
EXPORT_SYMBOL(ip6t_find_target_lock);
EXPORT_SYMBOL(ip6t_register_match);
EXPORT_SYMBOL(ip6t_unregister_match);
EXPORT_SYMBOL(ip6t_register_target);
EXPORT_SYMBOL(ip6t_unregister_target);
EXPORT_SYMBOL(ip6t_ext_hdr);

module_init(init);
module_exit(fini);