ip_tables.c

linux-2.6.15.6

	if (ret != 0) {
		vfree(newinfo);
		return ret;
	}

	ret = down_interruptible(&ipt_mutex);
	if (ret != 0) {
		vfree(newinfo);
		return ret;
	}

	/* Don't autoload: we'd eat our tail... */
	if (list_named_find(&ipt_tables, table->name)) {
		ret = -EEXIST;
		goto free_unlock;
	}

	/* 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;

	rwlock_init(&table->lock);
	list_prepend(&ipt_tables, table);

 unlock:
	up(&ipt_mutex);
	return ret;

 free_unlock:
	vfree(newinfo);
	goto unlock;
}

void ipt_unregister_table(struct ipt_table *table)
{
	down(&ipt_mutex);
	LIST_DELETE(&ipt_tables, table);
	up(&ipt_mutex);

	/* Decrease module usage counts and free resources */
	IPT_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 sk_buff *skb,
		unsigned int optlen,
		int invert,
		int *hotdrop)
{
	/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
	u_int8_t _opt[60 - sizeof(struct tcphdr)], *op;
	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,
				skb->nh.iph->ihl*4 + sizeof(struct tcphdr),
				optlen, _opt);
	if (op == NULL) {
		*hotdrop = 1;
		return 0;
	}

	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 int
tcp_match(const struct sk_buff *skb,
	  const struct net_device *in,
	  const struct net_device *out,
	  const void *matchinfo,
	  int offset,
	  int *hotdrop)
{
	struct tcphdr _tcph, *th;
	const struct ipt_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 = 1;
		}
		/* Must not be a fragment. */
		return 0;
	}

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

	th = skb_header_pointer(skb, skb->nh.iph->ihl*4,
				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 = 1;
		return 0;
	}

	if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
			ntohs(th->source),
			!!(tcpinfo->invflags & IPT_TCP_INV_SRCPT)))
		return 0;
	if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
			ntohs(th->dest),
			!!(tcpinfo->invflags & IPT_TCP_INV_DSTPT)))
		return 0;
	if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
		      == tcpinfo->flg_cmp,
		      IPT_TCP_INV_FLAGS))
		return 0;
	if (tcpinfo->option) {
		if (th->doff * 4 < sizeof(_tcph)) {
			*hotdrop = 1;
			return 0;
		}
		if (!tcp_find_option(tcpinfo->option, skb,
				     th->doff*4 - sizeof(_tcph),
				     tcpinfo->invflags & IPT_TCP_INV_OPTION,
				     hotdrop))
			return 0;
	}
	return 1;
}

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

	/* Must specify proto == TCP, and no unknown invflags */
	return ip->proto == IPPROTO_TCP
		&& !(ip->invflags & IPT_INV_PROTO)
		&& matchsize == IPT_ALIGN(sizeof(struct ipt_tcp))
		&& !(tcpinfo->invflags & ~IPT_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,
	  int *hotdrop)
{
	struct udphdr _udph, *uh;
	const struct ipt_udp *udpinfo = matchinfo;

	/* Must not be a fragment. */
	if (offset)
		return 0;

	uh = skb_header_pointer(skb, skb->nh.iph->ihl*4,
				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 = 1;
		return 0;
	}

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

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

	/* Must specify proto == UDP, and no unknown invflags */
	if (ip->proto != IPPROTO_UDP || (ip->invflags & IPT_INV_PROTO)) {
		duprintf("ipt_udp: Protocol %u != %u\n", ip->proto,
			 IPPROTO_UDP);
		return 0;
	}
	if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_udp))) {
		duprintf("ipt_udp: matchsize %u != %u\n",
			 matchinfosize, IPT_ALIGN(sizeof(struct ipt_udp)));
		return 0;
	}
	if (udpinfo->invflags & ~IPT_UDP_INV_MASK) {
		duprintf("ipt_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
icmp_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 ((test_type == 0xFF) || (type == test_type && code >= min_code && code <= max_code))
		^ invert;
}

static int
icmp_match(const struct sk_buff *skb,
	   const struct net_device *in,
	   const struct net_device *out,
	   const void *matchinfo,
	   int offset,
	   int *hotdrop)
{
	struct icmphdr _icmph, *ic;
	const struct ipt_icmp *icmpinfo = matchinfo;

	/* Must not be a fragment. */
	if (offset)
		return 0;

	ic = skb_header_pointer(skb, skb->nh.iph->ihl*4,
				sizeof(_icmph), &_icmph);
	if (ic == NULL) {
		/* 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;
	}

	return icmp_type_code_match(icmpinfo->type,
				    icmpinfo->code[0],
				    icmpinfo->code[1],
				    ic->type, ic->code,
				    !!(icmpinfo->invflags&IPT_ICMP_INV));
}

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

	/* Must specify proto == ICMP, and no unknown invflags */
	return ip->proto == IPPROTO_ICMP
		&& !(ip->invflags & IPT_INV_PROTO)
		&& matchsize == IPT_ALIGN(sizeof(struct ipt_icmp))
		&& !(icmpinfo->invflags & ~IPT_ICMP_INV);
}

/* The built-in targets: standard (NULL) and error. */
static struct ipt_target ipt_standard_target = {
	.name		= IPT_STANDARD_TARGET,
};

static struct ipt_target ipt_error_target = {
	.name		= IPT_ERROR_TARGET,
	.target		= ipt_error,
};

static struct nf_sockopt_ops ipt_sockopts = {
	.pf		= PF_INET,
	.set_optmin	= IPT_BASE_CTL,
	.set_optmax	= IPT_SO_SET_MAX+1,
	.set		= do_ipt_set_ctl,
	.get_optmin	= IPT_BASE_CTL,
	.get_optmax	= IPT_SO_GET_MAX+1,
	.get		= do_ipt_get_ctl,
};

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

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

static struct ipt_match icmp_matchstruct = {
	.name		= "icmp",
	.match		= &icmp_match,
	.checkentry	= &icmp_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 ipt_target *t,
                               off_t start_offset, char *buffer, int length,
                               off_t *pos, unsigned int *count)
{
	if (t == &ipt_standard_target || t == &ipt_error_target)
		return 0;
	return print_name((char *)t, start_offset, buffer, length, pos, count);
}

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

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

	LIST_FIND(&ipt_tables, print_name, void *,
		  offset, buffer, length, &pos, &count);

	up(&ipt_mutex);

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

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

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

	LIST_FIND(&ipt_target, print_target, struct ipt_target *,
		  offset, buffer, length, &pos, &count);
	
	up(&ipt_mutex);

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

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

	if (down_interruptible(&ipt_mutex) != 0)
		return 0;
	
	LIST_FIND(&ipt_match, print_name, void *,
		  offset, buffer, length, &pos, &count);

	up(&ipt_mutex);

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

static const struct { char *name; get_info_t *get_info; } ipt_proc_entry[] =
{ { "ip_tables_names", ipt_get_tables },
  { "ip_tables_targets", ipt_get_targets },
  { "ip_tables_matches", ipt_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(&ipt_mutex);
	list_append(&ipt_target, &ipt_standard_target);
	list_append(&ipt_target, &ipt_error_target);
	list_append(&ipt_match, &tcp_matchstruct);
	list_append(&ipt_match, &udp_matchstruct);
	list_append(&ipt_match, &icmp_matchstruct);
	up(&ipt_mutex);

	/* Register setsockopt */
	ret = nf_register_sockopt(&ipt_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; ipt_proc_entry[i].name; i++) {
		proc = proc_net_create(ipt_proc_entry[i].name, 0,
				       ipt_proc_entry[i].get_info);
		if (!proc) {
			while (--i >= 0)
				proc_net_remove(ipt_proc_entry[i].name);
			nf_unregister_sockopt(&ipt_sockopts);
			return -ENOMEM;
		}
		proc->owner = THIS_MODULE;
	}
	}
#endif

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

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

EXPORT_SYMBOL(ipt_register_table);
EXPORT_SYMBOL(ipt_unregister_table);
EXPORT_SYMBOL(ipt_register_match);
EXPORT_SYMBOL(ipt_unregister_match);
EXPORT_SYMBOL(ipt_do_table);
EXPORT_SYMBOL(ipt_register_target);
EXPORT_SYMBOL(ipt_unregister_target);
EXPORT_SYMBOL(ipt_find_target);

module_init(init);
module_exit(fini);