ipfwadm_core.c

linux-2.4.29操作系统的源码

/* Minor modifications to fit on compatibility framework:
   [e-mail]
*/

#include <linux/config.h>
#define CONFIG_IP_FIREWALL
#define CONFIG_IP_FIREWALL_VERBOSE
#define CONFIG_IP_MASQUERADE
#define CONFIG_IP_ACCT
#define CONFIG_IP_TRANSPARENT_PROXY
#if defined(CONFIG_NETLINK_DEV) || defined(CONFIG_NETLINK_DEV_MODULE)
#define CONFIG_IP_FIREWALL_NETLINK
#endif

/*
 *	IP firewalling code. This is taken from 4.4BSD. Please note the
 *	copyright message below. As per the GPL it must be maintained
 *	and the licenses thus do not conflict. While this port is subject
 *	to the GPL I also place my modifications under the original
 *	license in recognition of the original copyright.
 *				-- Alan Cox.
 *
 *	$Id: ipfwadm_core.c,v 1.9.2.2 2002/01/24 15:50:42 davem Exp $
 *
 *	Ported from BSD to Linux,
 *		Alan Cox 22/Nov/1994.
 *	Zeroing /proc and other additions
 *		Jos Vos 4/Feb/1995.
 *	Merged and included the FreeBSD-Current changes at Ugen's request
 *	(but hey it's a lot cleaner now). Ugen would prefer in some ways
 *	we waited for his final product but since Linux 1.2.0 is about to
 *	appear it's not practical - Read: It works, it's not clean but please
 *	don't consider it to be his standard of finished work.
 *		Alan Cox 12/Feb/1995
 *	Porting bidirectional entries from BSD, fixing accounting issues,
 *	adding struct ip_fwpkt for checking packets with interface address
 *		Jos Vos 5/Mar/1995.
 *	Established connections (ACK check), ACK check on bidirectional rules,
 *	ICMP type check.
 *		Wilfred Mollenvanger 7/7/1995.
 *	TCP attack protection.
 *		Alan Cox 25/8/95, based on information from bugtraq.
 *	ICMP type printk, IP_FW_F_APPEND
 *		Bernd Eckenfels 1996-01-31
 *	Split blocking chain into input and output chains, add new "insert" and
 *	"append" commands to replace semi-intelligent "add" command, let "delete".
 *	only delete the first matching entry, use 0xFFFF (0xFF) as ports (ICMP
 *	types) when counting packets being 2nd and further fragments.
 *		Jos Vos <[e-mail]> 8/2/1996.
 *	Add support for matching on device names.
 *		Jos Vos <[e-mail]> 15/2/1996.
 *	Transparent proxying support.
 *		Willy Konynenberg <[e-mail]> 10/5/96.
 *	Make separate accounting on incoming and outgoing packets possible.
 *		Jos Vos <[e-mail]> 18/5/1996.
 *	Added trap out of bad frames.
 *		Alan Cox <[e-mail]> 17/11/1996
 *
 *
 * Masquerading functionality
 *
 * Copyright (c) 1994 Pauline Middelink
 *
 * The pieces which added masquerading functionality are totally
 * my responsibility and have nothing to with the original authors
 * copyright or doing.
 *
 * Parts distributed under GPL.
 *
 * Fixes:
 *	Pauline Middelink	:	Added masquerading.
 *	Alan Cox		:	Fixed an error in the merge.
 *	Thomas Quinot		:	Fixed port spoofing.
 *	Alan Cox		:	Cleaned up retransmits in spoofing.
 *	Alan Cox		:	Cleaned up length setting.
 *	Wouter Gadeyne		:	Fixed masquerading support of ftp PORT commands
 *
 *	Juan Jose Ciarlante	:	Masquerading code moved to ip_masq.c
 *	Andi Kleen :		Print frag_offsets and the ip flags properly.
 *
 *	All the real work was done by .....
 *
 */


/*
 * Copyright (c) 1993 Daniel Boulet
 * Copyright (c) 1994 Ugen J.S.Antsilevich
 *
 * Redistribution and use in source forms, with and without modification,
 * are permitted provided that this entire comment appears intact.
 *
 * Redistribution in binary form may occur without any restrictions.
 * Obviously, it would be nice if you gave credit where credit is due
 * but requiring it would be too onerous.
 *
 * This software is provided ``AS IS'' without any warranties of any kind.
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/module.h>

#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/icmp.h>
#include <linux/udp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/sock.h>
#include <net/icmp.h>
#include <linux/netlink.h>
#include <linux/init.h>
#include <linux/netfilter_ipv4/ipfwadm_core.h>
#include <linux/netfilter_ipv4/compat_firewall.h>

#include <net/checksum.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/version.h>

/*
 *	Implement IP packet firewall
 */

#ifdef DEBUG_IP_FIREWALL
#define dprintf1(a)		printk(a)
#define dprintf2(a1,a2)		printk(a1,a2)
#define dprintf3(a1,a2,a3)	printk(a1,a2,a3)
#define dprintf4(a1,a2,a3,a4)	printk(a1,a2,a3,a4)
#else
#define dprintf1(a)
#define dprintf2(a1,a2)
#define dprintf3(a1,a2,a3)
#define dprintf4(a1,a2,a3,a4)
#endif

#define print_ip(a)	 printk("%u.%u.%u.%u", NIPQUAD(a));

#ifdef DEBUG_IP_FIREWALL
#define dprint_ip(a)	print_ip(a)
#else
#define dprint_ip(a)
#endif

#if defined(CONFIG_IP_ACCT) || defined(CONFIG_IP_FIREWALL)

struct ip_fw *ip_fw_fwd_chain;
struct ip_fw *ip_fw_in_chain;
struct ip_fw *ip_fw_out_chain;
struct ip_fw *ip_acct_chain;
struct ip_fw *ip_masq_chain;

static struct ip_fw **chains[] =
	{&ip_fw_fwd_chain, &ip_fw_in_chain, &ip_fw_out_chain, &ip_acct_chain,
	 &ip_masq_chain
	};
#endif /* CONFIG_IP_ACCT || CONFIG_IP_FIREWALL */

#ifdef CONFIG_IP_FIREWALL
int ip_fw_fwd_policy=IP_FW_F_ACCEPT;
int ip_fw_in_policy=IP_FW_F_ACCEPT;
int ip_fw_out_policy=IP_FW_F_ACCEPT;

static int *policies[] =
	{&ip_fw_fwd_policy, &ip_fw_in_policy, &ip_fw_out_policy};

#endif

#ifdef CONFIG_IP_FIREWALL_NETLINK
struct sock *ipfwsk;
#endif

/*
 *	Returns 1 if the port is matched by the vector, 0 otherwise
 */

extern inline int port_match(unsigned short *portptr,int nports,unsigned short port,int range_flag)
{
	if (!nports)
		return 1;
	if ( range_flag )
	{
		if ( portptr[0] <= port && port <= portptr[1] )
		{
			return( 1 );
		}
		nports -= 2;
		portptr += 2;
	}
	while ( nports-- > 0 )
	{
		if ( *portptr++ == port )
		{
			return( 1 );
		}
	}
	return(0);
}

#if defined(CONFIG_IP_ACCT) || defined(CONFIG_IP_FIREWALL)

#ifdef CONFIG_IP_FIREWALL_VERBOSE

/*
 *	VERY ugly piece of code which actually makes kernel printf for
 * 	matching packets.
 */

static char *chain_name(struct ip_fw *chain, int mode)
{
	switch (mode) {
	case IP_FW_MODE_ACCT_IN: return "acct in";
	case IP_FW_MODE_ACCT_OUT: return "acct out";
	default:
		if (chain == ip_fw_fwd_chain)
			return "fw-fwd";
		else if (chain == ip_fw_in_chain)
			return "fw-in";
		else
			return "fw-out";
	}
}

static char *rule_name(struct ip_fw *f, int mode, char *buf)
{
	if (mode == IP_FW_MODE_ACCT_IN || mode == IP_FW_MODE_ACCT_OUT)
		return "";

	if(f->fw_flg&IP_FW_F_ACCEPT) {
		if(f->fw_flg&IP_FW_F_REDIR) {
			sprintf(buf, "acc/r%d ", f->fw_pts[f->fw_nsp+f->fw_ndp]);
			return buf;
		} else if(f->fw_flg&IP_FW_F_MASQ)
			return "acc/masq ";
		else
			return "acc ";
	} else if(f->fw_flg&IP_FW_F_ICMPRPL) {
		return "rej ";
	} else {
		return "deny ";
	}
}

static void print_packet(struct iphdr *ip,
			 u16 src_port, u16 dst_port, u16 icmp_type,
			 char *chain, char *rule, char *devname)
{
	__u32 *opt = (__u32 *) (ip + 1);
	int opti;
	__u16 foff = ntohs(ip->frag_off);

	printk(KERN_INFO "IP %s %s%s", chain, rule, devname);

	switch(ip->protocol)
	{
	case IPPROTO_TCP:
		printk(" TCP ");
		break;
	case IPPROTO_UDP:
		printk(" UDP ");
		break;
	case IPPROTO_ICMP:
		printk(" ICMP/%d ", icmp_type);
		break;
	default:
		printk(" PROTO=%d ", ip->protocol);
		break;
	}
	print_ip(ip->saddr);
	if(ip->protocol == IPPROTO_TCP || ip->protocol == IPPROTO_UDP)
		printk(":%hu", src_port);
	printk(" ");
	print_ip(ip->daddr);
	if(ip->protocol == IPPROTO_TCP || ip->protocol == IPPROTO_UDP)
		printk(":%hu", dst_port);
	printk(" L=%hu S=0x%2.2hX I=%hu FO=0x%4.4hX T=%hu",
	       ntohs(ip->tot_len), ip->tos, ntohs(ip->id),
	       foff & IP_OFFSET, ip->ttl);
	if (foff & IP_DF) printk(" DF=1");
	if (foff & IP_MF) printk(" MF=1");
	for (opti = 0; opti < (ip->ihl - sizeof(struct iphdr) / 4); opti++)
		printk(" O=0x%8.8X", *opt++);
	printk("\n");
}
#endif

/*
 *	Returns one of the generic firewall policies, like FW_ACCEPT.
 *	Also does accounting so you can feed it the accounting chain.
 *
 *	The modes is either IP_FW_MODE_FW (normal firewall mode),
 *	IP_FW_MODE_ACCT_IN or IP_FW_MODE_ACCT_OUT (accounting mode,
 *	steps through the entire chain and handles fragments
 *	differently), or IP_FW_MODE_CHK (handles user-level check,
 *	counters are not updated).
 */


int ip_fw_chk(struct iphdr *ip, struct net_device *rif, __u16 *redirport,
	      struct ip_fw *chain, int policy, int mode)
{
	struct ip_fw *f;
	struct tcphdr		*tcp=(struct tcphdr *)((__u32 *)ip+ip->ihl);
	struct udphdr		*udp=(struct udphdr *)((__u32 *)ip+ip->ihl);
	struct icmphdr		*icmp=(struct icmphdr *)((__u32 *)ip+ip->ihl);
	__u32			src, dst;
	__u16			src_port=0xFFFF, dst_port=0xFFFF, icmp_type=0xFF;
	unsigned short		f_prt=0, prt;
	char			notcpsyn=0, notcpack=0, match;
	unsigned short		offset;
	int			answer;
	unsigned char		tosand, tosxor;

	/*
	 *	If the chain is empty follow policy. The BSD one
	 *	accepts anything giving you a time window while
	 *	flushing and rebuilding the tables.
	 */

	src = ip->saddr;
	dst = ip->daddr;

	/*
	 *	This way we handle fragmented packets.
	 *	we ignore all fragments but the first one
	 *	so the whole packet can't be reassembled.
	 *	This way we relay on the full info which
	 *	stored only in first packet.
	 *
	 *	Note that this theoretically allows partial packet
	 *	spoofing. Not very dangerous but paranoid people may
	 *	wish to play with this. It also allows the so called
	 *	"fragment bomb" denial of service attack on some types
	 *	of system.
	 */

	offset = ntohs(ip->frag_off) & IP_OFFSET;

	/*
	 *	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 && ip->protocol == IPPROTO_TCP)
		return FW_BLOCK;

	if (offset!=0 && !(mode & (IP_FW_MODE_ACCT_IN|IP_FW_MODE_ACCT_OUT)) &&
		(ip->protocol == IPPROTO_TCP || ip->protocol == IPPROTO_UDP ||
			ip->protocol == IPPROTO_ICMP))
		return FW_ACCEPT;

	/*
	 *	 Header fragment for TCP is too small to check the bits.
	 */

	if(ip->protocol==IPPROTO_TCP && (ip->ihl<<2)+16 > ntohs(ip->tot_len))
		return FW_BLOCK;

	/*
	 *	Too short.
	 *
	 *	But only too short for a packet with ports...
	 */

	else if((ntohs(ip->tot_len)<8+(ip->ihl<<2))&&(ip->protocol==IPPROTO_TCP || ip->protocol==IPPROTO_UDP))
		return FW_BLOCK;

	src = ip->saddr;
	dst = ip->daddr;

	/*
	 *	If we got interface from which packet came
	 *	we can use the address directly. This is unlike
	 *	4.4BSD derived systems that have an address chain
	 *	per device. We have a device per address with dummy
	 *	devices instead.
	 */

	dprintf1("Packet ");
	switch(ip->protocol)
	{
		case IPPROTO_TCP:
			dprintf1("TCP ");
			/* ports stay 0xFFFF if it is not the first fragment */
			if (!offset) {
				src_port=ntohs(tcp->source);
				dst_port=ntohs(tcp->dest);
				if(!tcp->ack && !tcp->rst)
					/* We do NOT have ACK, value TRUE */
					notcpack=1;
				if(!tcp->syn || !notcpack)
					/* We do NOT have SYN, value TRUE */
					notcpsyn=1;
			}
			prt=IP_FW_F_TCP;
			break;
		case IPPROTO_UDP:
			dprintf1("UDP ");
			/* ports stay 0xFFFF if it is not the first fragment */
			if (!offset) {
				src_port=ntohs(udp->source);
				dst_port=ntohs(udp->dest);
			}
			prt=IP_FW_F_UDP;
			break;
		case IPPROTO_ICMP:
			/* icmp_type stays 255 if it is not the first fragment */
			if (!offset)
				icmp_type=(__u16)(icmp->type);
			dprintf2("ICMP:%d ",icmp_type);
			prt=IP_FW_F_ICMP;
			break;
		default:
			dprintf2("p=%d ",ip->protocol);
			prt=IP_FW_F_ALL;
			break;
	}
#ifdef DEBUG_IP_FIREWALL
	dprint_ip(ip->saddr);

	if (ip->protocol==IPPROTO_TCP || ip->protocol==IPPROTO_UDP)
		/* This will print 65535 when it is not the first fragment! */
		dprintf2(":%d ", src_port);
	dprint_ip(ip->daddr);
	if (ip->protocol==IPPROTO_TCP || ip->protocol==IPPROTO_UDP)
		/* This will print 65535 when it is not the first fragment! */
		dprintf2(":%d ",dst_port);
	dprintf1("\n");
#endif

	for (f=chain;f;f=f->fw_next)
	{
		/*
		 *	This is a bit simpler as we don't have to walk
		 *	an interface chain as you do in BSD - same logic
		 *	however.
		 */

		/*
		 *	Match can become 0x01 (a "normal" match was found),
		 *	0x02 (a reverse match was found), and 0x03 (the
		 *	IP addresses match in both directions).
		 *	Now we know in which direction(s) we should look