net/ipv6/netfilter/ip6t_LOG.c

/*
 * This is a module which is used for logging packets.
 */

/* (C) 2001 Jan Rekorajski <baggins@pld.org.pl>
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/ip.h>
#include <linux/spinlock.h>
#include <linux/icmpv6.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/ipv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <net/netfilter/nf_log.h>
#include <net/netfilter/xt_log.h>

MODULE_AUTHOR("Jan Rekorajski <baggins@pld.org.pl>");
MODULE_DESCRIPTION("Xtables: IPv6 packet logging to syslog");
MODULE_LICENSE("GPL");

struct in_device;
#include <net/route.h>
#include <linux/netfilter_ipv6/ip6t_LOG.h>

/* One level of recursion won't kill us */
static void dump_packet(struct sbuff *m,
			const struct nf_loginfo *info,
			const struct sk_buff *skb, unsigned int ip6hoff,
			int recurse)
{
	u_int8_t currenthdr;
	int fragment;
	struct ipv6hdr _ip6h;
	const struct ipv6hdr *ih;
	unsigned int ptr;
	unsigned int hdrlen = 0;
	unsigned int logflags;

	if (info->type == NF_LOG_TYPE_LOG)
		logflags = info->u.log.logflags;
	else
		logflags = NF_LOG_MASK;

	ih = skb_header_pointer(skb, ip6hoff, sizeof(_ip6h), &_ip6h);
	if (ih == NULL) {
		sb_add(m, "TRUNCATED");
		return;
	}

	/* Max length: 88 "SRC=0000.0000.0000.0000.0000.0000.0000.0000 DST=0000.0000.0000.0000.0000.0000.0000.0000 " */
	sb_add(m, "SRC=%pI6 DST=%pI6 ", &ih->saddr, &ih->daddr);

	/* Max length: 44 "LEN=65535 TC=255 HOPLIMIT=255 FLOWLBL=FFFFF " */
	sb_add(m, "LEN=%Zu TC=%u HOPLIMIT=%u FLOWLBL=%u ",
	       ntohs(ih->payload_len) + sizeof(struct ipv6hdr),
	       (ntohl(*(__be32 *)ih) & 0x0ff00000) >> 20,
	       ih->hop_limit,
	       (ntohl(*(__be32 *)ih) & 0x000fffff));

	fragment = 0;
	ptr = ip6hoff + sizeof(struct ipv6hdr);
	currenthdr = ih->nexthdr;
	while (currenthdr != NEXTHDR_NONE && ip6t_ext_hdr(currenthdr)) {
		struct ipv6_opt_hdr _hdr;
		const struct ipv6_opt_hdr *hp;

		hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
		if (hp == NULL) {
			sb_add(m, "TRUNCATED");
			return;
		}

		/* Max length: 48 "OPT (...) " */
		if (logflags & IP6T_LOG_IPOPT)
			sb_add(m, "OPT ( ");

		switch (currenthdr) {
		case IPPROTO_FRAGMENT: {
			struct frag_hdr _fhdr;
			const struct frag_hdr *fh;

			sb_add(m, "FRAG:");
			fh = skb_header_pointer(skb, ptr, sizeof(_fhdr),
						&_fhdr);
			if (fh == NULL) {
				sb_add(m, "TRUNCATED ");
				return;
			}

			/* Max length: 6 "65535 " */
			sb_add(m, "%u ", ntohs(fh->frag_off) & 0xFFF8);

			/* Max length: 11 "INCOMPLETE " */
			if (fh->frag_off & htons(0x0001))
				sb_add(m, "INCOMPLETE ");

			sb_add(m, "ID:%08x ", ntohl(fh->identification));

			if (ntohs(fh->frag_off) & 0xFFF8)
				fragment = 1;

			hdrlen = 8;

			break;
		}
		case IPPROTO_DSTOPTS:
		case IPPROTO_ROUTING:
		case IPPROTO_HOPOPTS:
			if (fragment) {
				if (logflags & IP6T_LOG_IPOPT)
					sb_add(m, ")");
				return;
			}
			hdrlen = ipv6_optlen(hp);
			break;
		/* Max Length */
		case IPPROTO_AH:
			if (logflags & IP6T_LOG_IPOPT) {
				struct ip_auth_hdr _ahdr;
				const struct ip_auth_hdr *ah;

				/* Max length: 3 "AH " */
				sb_add(m, "AH ");

				if (fragment) {
					sb_add(m, ")");
					return;
				}

				ah = skb_header_pointer(skb, ptr, sizeof(_ahdr),
							&_ahdr);
				if (ah == NULL) {
					/*
					 * Max length: 26 "INCOMPLETE [65535
					 *  bytes] )"
					 */
					sb_add(m, "INCOMPLETE [%u bytes] )",
					       skb->len - ptr);
					return;
				}

				/* Length: 15 "SPI=0xF1234567 */
				sb_add(m, "SPI=0x%x ", ntohl(ah->spi));

			}

			hdrlen = (hp->hdrlen+2)<<2;
			break;
		case IPPROTO_ESP:
			if (logflags & IP6T_LOG_IPOPT) {
				struct ip_esp_hdr _esph;
				const struct ip_esp_hdr *eh;

				/* Max length: 4 "ESP " */
				sb_add(m, "ESP ");

				if (fragment) {
					sb_add(m, ")");
					return;
				}

				/*
				 * Max length: 26 "INCOMPLETE [65535 bytes] )"
				 */
				eh = skb_header_pointer(skb, ptr, sizeof(_esph),
							&_esph);
				if (eh == NULL) {
					sb_add(m, "INCOMPLETE [%u bytes] )",
					       skb->len - ptr);
					return;
				}

				/* Length: 16 "SPI=0xF1234567 )" */
				sb_add(m, "SPI=0x%x )", ntohl(eh->spi) );

			}
			return;
		default:
			/* Max length: 20 "Unknown Ext Hdr 255" */
			sb_add(m, "Unknown Ext Hdr %u", currenthdr);
			return;
		}
		if (logflags & IP6T_LOG_IPOPT)
			sb_add(m, ") ");

		currenthdr = hp->nexthdr;
		ptr += hdrlen;
	}

	switch (currenthdr) {
	case IPPROTO_TCP: {
		struct tcphdr _tcph;
		const struct tcphdr *th;

		/* Max length: 10 "PROTO=TCP " */
		sb_add(m, "PROTO=TCP ");

		if (fragment)
			break;

		/* Max length: 25 "INCOMPLETE [65535 bytes] " */
		th = skb_header_pointer(skb, ptr, sizeof(_tcph), &_tcph);
		if (th == NULL) {
			sb_add(m, "INCOMPLETE [%u bytes] ", skb->len - ptr);
			return;
		}

		/* Max length: 20 "SPT=65535 DPT=65535 " */
		sb_add(m, "SPT=%u DPT=%u ",
		       ntohs(th->source), ntohs(th->dest));
		/* Max length: 30 "SEQ=4294967295 ACK=4294967295 " */
		if (logflags & IP6T_LOG_TCPSEQ)
			sb_add(m, "SEQ=%u ACK=%u ",
			       ntohl(th->seq), ntohl(th->ack_seq));
		/* Max length: 13 "WINDOW=65535 " */
		sb_add(m, "WINDOW=%u ", ntohs(th->window));
		/* Max length: 9 "RES=0x3C " */
		sb_add(m, "RES=0x%02x ", (u_int8_t)(ntohl(tcp_flag_word(th) & TCP_RESERVED_BITS) >> 22));
		/* Max length: 32 "CWR ECE URG ACK PSH RST SYN FIN " */
		if (th->cwr)
			sb_add(m, "CWR ");
		if (th->ece)
			sb_add(m, "ECE ");
		if (th->urg)
			sb_add(m, "URG ");
		if (th->ack)
			sb_add(m, "ACK ");
		if (th->psh)
			sb_add(m, "PSH ");
		if (th->rst)
			sb_add(m, "RST ");
		if (th->syn)
			sb_add(m, "SYN ");
		if (th->fin)
			sb_add(m, "FIN ");
		/* Max length: 11 "URGP=65535 " */
		sb_add(m, "URGP=%u ", ntohs(th->urg_ptr));

		if ((logflags & IP6T_LOG_TCPOPT) &&
		    th->doff * 4 > sizeof(struct tcphdr)) {
			u_int8_t _opt[60 - sizeof(struct tcphdr)];
			const u_int8_t *op;
			unsigned int i;
			unsigned int optsize = th->doff * 4
					       - sizeof(struct tcphdr);

			op = skb_header_pointer(skb,
						ptr + sizeof(struct tcphdr),
						optsize, _opt);
			if (op == NULL) {
				sb_add(m, "OPT (TRUNCATED)");
				return;
			}

			/* Max length: 127 "OPT (" 15*4*2chars ") " */
			sb_add(m, "OPT (");
			for (i =0; i < optsize; i++)
				sb_add(m, "%02X", op[i]);
			sb_add(m, ") ");
		}
		break;
	}
	case IPPROTO_UDP:
	case IPPROTO_UDPLITE: {
		struct udphdr _udph;
		const struct udphdr *uh;

		if (currenthdr == IPPROTO_UDP)
			/* Max length: 10 "PROTO=UDP "     */
			sb_add(m, "PROTO=UDP " );
		else	/* Max length: 14 "PROTO=UDPLITE " */
			sb_add(m, "PROTO=UDPLITE ");

		if (fragment)
			break;

		/* Max length: 25 "INCOMPLETE [65535 bytes] " */
		uh = skb_header_pointer(skb, ptr, sizeof(_udph), &_udph);
		if (uh == NULL) {
			sb_add(m, "INCOMPLETE [%u bytes] ", skb->len - ptr);
			return;
		}

		/* Max length: 20 "SPT=65535 DPT=65535 " */
		sb_add(m, "SPT=%u DPT=%u LEN=%u ",
		       ntohs(uh->source), ntohs(uh->dest),
		       ntohs(uh->len));
		break;
	}
	case IPPROTO_ICMPV6: {
		struct icmp6hdr _icmp6h;
		const struct icmp6hdr *ic;

		/* Max length: 13 "PROTO=ICMPv6 " */
		sb_add(m, "PROTO=ICMPv6 ");

		if (fragment)
			break;

		/* Max length: 25 "INCOMPLETE [65535 bytes] " */
		ic = skb_header_pointer(skb, ptr, sizeof(_icmp6h), &_icmp6h);
		if (ic == NULL) {
			sb_add(m, "INCOMPLETE [%u bytes] ", skb->len - ptr);
			return;
		}

		/* Max length: 18 "TYPE=255 CODE=255 " */
		sb_add(m, "TYPE=%u CODE=%u ", ic->icmp6_type, ic->icmp6_code);

		switch (ic->icmp6_type) {
		case ICMPV6_ECHO_REQUEST:
		case ICMPV6_ECHO_REPLY:
			/* Max length: 19 "ID=65535 SEQ=65535 " */
			sb_add(m, "ID=%u SEQ=%u ",
				ntohs(ic->icmp6_identifier),
				ntohs(ic->icmp6_sequence));
			break;
		case ICMPV6_MGM_QUERY:
		case ICMPV6_MGM_REPORT:
		case ICMPV6_MGM_REDUCTION:
			break;

		case ICMPV6_PARAMPROB:
			/* Max length: 17 "POINTER=ffffffff " */
			sb_add(m, "POINTER=%08x ", ntohl(ic->icmp6_pointer));
			/* Fall through */
		case ICMPV6_DEST_UNREACH:
		case ICMPV6_PKT_TOOBIG:
		case ICMPV6_TIME_EXCEED:
			/* Max length: 3+maxlen */
			if (recurse) {
				sb_add(m, "[");
				dump_packet(m, info, skb,
					    ptr + sizeof(_icmp6h), 0);
				sb_add(m, "] ");
			}

			/* Max length: 10 "MTU=65535 " */
			if (ic->icmp6_type == ICMPV6_PKT_TOOBIG)
				sb_add(m, "MTU=%u ", ntohl(ic->icmp6_mtu));
		}
		break;
	}
	/* Max length: 10 "PROTO=255 " */
	default:
		sb_add(m, "PROTO=%u ", currenthdr);
	}

	/* Max length: 15 "UID=4294967295 " */
	if ((logflags & IP6T_LOG_UID) && recurse && skb->sk) {
		read_lock_bh(&skb->sk->sk_callback_lock);
		if (skb->sk->sk_socket && skb->sk->sk_socket->file)
			sb_add(m, "UID=%u GID=%u ",
				skb->sk->sk_socket->file->f_cred->fsuid,
				skb->sk->sk_socket->file->f_cred->fsgid);
		read_unlock_bh(&skb->sk->sk_callback_lock);
	}

	/* Max length: 16 "MARK=0xFFFFFFFF " */
	if (!recurse && skb->mark)
		sb_add(m, "MARK=0x%x ", skb->mark);
}

static void dump_mac_header(struct sbuff *m,
			    const struct nf_loginfo *info,
			    const struct sk_buff *skb)
{
	struct net_device *dev = skb->dev;
	unsigned int logflags = 0;

	if (info->type == NF_LOG_TYPE_LOG)
		logflags = info->u.log.logflags;

	if (!(logflags & IP6T_LOG_MACDECODE))
		goto fallback;

	switch (dev->type) {
	case ARPHRD_ETHER:
		sb_add(m, "MACSRC=%pM MACDST=%pM MACPROTO=%04x ",
		       eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest,
		       ntohs(eth_hdr(skb)->h_proto));
		return;
	default:
		break;
	}

fallback:
	sb_add(m, "MAC=");
	if (dev->hard_header_len &&
	    skb->mac_header != skb->network_header) {
		const unsigned char *p = skb_mac_header(skb);
		unsigned int len = dev->hard_header_len;
		unsigned int i;

		if (dev->type == ARPHRD_SIT &&
		    (p -= ETH_HLEN) < skb->head)
			p = NULL;

		if (p != NULL) {
			sb_add(m, "%02x", *p++);
			for (i = 1; i < len; i++)
				sb_add(m, ":%02x", *p++);
		}
		sb_add(m, " ");

		if (dev->type == ARPHRD_SIT) {
			const struct iphdr *iph =
				(struct iphdr *)skb_mac_header(skb);
			sb_add(m, "TUNNEL=%pI4->%pI4 ", &iph->saddr, &iph->daddr);
		}
	} else
		sb_add(m, " ");
}

static struct nf_loginfo default_loginfo = {
	.type	= NF_LOG_TYPE_LOG,
	.u = {
		.log = {
			.level	  = 5,
			.logflags = NF_LOG_MASK,
		},
	},
};

static void
ip6t_log_packet(u_int8_t pf,
		unsigned int hooknum,
		const struct sk_buff *skb,
		const struct net_device *in,
		const struct net_device *out,
		const struct nf_loginfo *loginfo,
		const char *prefix)
{
	struct sbuff *m = sb_open();

	if (!loginfo)
		loginfo = &default_loginfo;

	sb_add(m, "<%d>%sIN=%s OUT=%s ", loginfo->u.log.level,
	       prefix,
	       in ? in->name : "",
	       out ? out->name : "");

	if (in != NULL)
		dump_mac_header(m, loginfo, skb);

	dump_packet(m, loginfo, skb, skb_network_offset(skb), 1);

	sb_close(m);
}

static unsigned int
log_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
	const struct ip6t_log_info *loginfo = par->targinfo;
	struct nf_loginfo li;

	li.type = NF_LOG_TYPE_LOG;
	li.u.log.level = loginfo->level;
	li.u.log.logflags = loginfo->logflags;

	ip6t_log_packet(NFPROTO_IPV6, par->hooknum, skb, par->in, par->out,
			&li, loginfo->prefix);
	return XT_CONTINUE;
}


static int log_tg6_check(const struct xt_tgchk_param *par)
{
	const struct ip6t_log_info *loginfo = par->targinfo;

	if (loginfo->level >= 8) {
		pr_debug("level %u >= 8\n", loginfo->level);
		return -EINVAL;
	}
	if (loginfo->prefix[sizeof(loginfo->prefix)-1] != '\0') {
		pr_debug("prefix not null-terminated\n");
		return -EINVAL;
	}
	return 0;
}

static struct xt_target log_tg6_reg __read_mostly = {
	.name 		= "LOG",
	.family		= NFPROTO_IPV6,
	.target 	= log_tg6,
	.targetsize	= sizeof(struct ip6t_log_info),
	.checkentry	= log_tg6_check,
	.me 		= THIS_MODULE,
};

static struct nf_logger ip6t_logger __read_mostly = {
	.name		= "ip6t_LOG",
	.logfn		= &ip6t_log_packet,
	.me		= THIS_MODULE,
};

static int __init log_tg6_init(void)
{
	int ret;

	ret = xt_register_target(&log_tg6_reg);
	if (ret < 0)
		return ret;
	nf_log_register(NFPROTO_IPV6, &ip6t_logger);
	return 0;
}

static void __exit log_tg6_exit(void)
{
	nf_log_unregister(&ip6t_logger);
	xt_unregister_target(&log_tg6_reg);
}

module_init(log_tg6_init);
module_exit(log_tg6_exit);