nft_log.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
 * Copyright (c) 2012-2014 Pablo Neira Ayuso <pablo@netfilter.org>
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 */

#include <linux/audit.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/ipv6.h>
#include <net/ip.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_log.h>
#include <linux/netdevice.h>

static const char *nft_log_null_prefix = "";

struct nft_log {
	struct nf_loginfo	loginfo;
	char			*prefix;
};

static bool audit_ip4(struct audit_buffer *ab, struct sk_buff *skb)
{
	struct iphdr _iph;
	const struct iphdr *ih;

	ih = skb_header_pointer(skb, skb_network_offset(skb), sizeof(_iph), &_iph);
	if (!ih)
		return false;

	audit_log_format(ab, " saddr=%pI4 daddr=%pI4 proto=%hhu",
			 &ih->saddr, &ih->daddr, ih->protocol);

	return true;
}

static bool audit_ip6(struct audit_buffer *ab, struct sk_buff *skb)
{
	struct ipv6hdr _ip6h;
	const struct ipv6hdr *ih;
	u8 nexthdr;
	__be16 frag_off;

	ih = skb_header_pointer(skb, skb_network_offset(skb), sizeof(_ip6h), &_ip6h);
	if (!ih)
		return false;

	nexthdr = ih->nexthdr;
	ipv6_skip_exthdr(skb, skb_network_offset(skb) + sizeof(_ip6h), &nexthdr, &frag_off);

	audit_log_format(ab, " saddr=%pI6c daddr=%pI6c proto=%hhu",
			 &ih->saddr, &ih->daddr, nexthdr);

	return true;
}

static void nft_log_eval_audit(const struct nft_pktinfo *pkt)
{
	struct sk_buff *skb = pkt->skb;
	struct audit_buffer *ab;
	int fam = -1;

	if (!audit_enabled)
		return;

	ab = audit_log_start(NULL, GFP_ATOMIC, AUDIT_NETFILTER_PKT);
	if (!ab)
		return;

	audit_log_format(ab, "mark=%#x", skb->mark);

	switch (nft_pf(pkt)) {
	case NFPROTO_BRIDGE:
		switch (eth_hdr(skb)->h_proto) {
		case htons(ETH_P_IP):
			fam = audit_ip4(ab, skb) ? NFPROTO_IPV4 : -1;
			break;
		case htons(ETH_P_IPV6):
			fam = audit_ip6(ab, skb) ? NFPROTO_IPV6 : -1;
			break;
		}
		break;
	case NFPROTO_IPV4:
		fam = audit_ip4(ab, skb) ? NFPROTO_IPV4 : -1;
		break;
	case NFPROTO_IPV6:
		fam = audit_ip6(ab, skb) ? NFPROTO_IPV6 : -1;
		break;
	}

	if (fam == -1)
		audit_log_format(ab, " saddr=? daddr=? proto=-1");

	audit_log_end(ab);
}

static void nft_log_eval(const struct nft_expr *expr,
			 struct nft_regs *regs,
			 const struct nft_pktinfo *pkt)
{
	const struct nft_log *priv = nft_expr_priv(expr);

	if (priv->loginfo.type == NF_LOG_TYPE_LOG &&
	    priv->loginfo.u.log.level == NFT_LOGLEVEL_AUDIT) {
		nft_log_eval_audit(pkt);
		return;
	}

	nf_log_packet(nft_net(pkt), nft_pf(pkt), nft_hook(pkt), pkt->skb,
		      nft_in(pkt), nft_out(pkt), &priv->loginfo, "%s",
		      priv->prefix);
}

static const struct nla_policy nft_log_policy[NFTA_LOG_MAX + 1] = {
	[NFTA_LOG_GROUP]	= { .type = NLA_U16 },
	[NFTA_LOG_PREFIX]	= { .type = NLA_STRING,
				    .len = NF_LOG_PREFIXLEN - 1 },
	[NFTA_LOG_SNAPLEN]	= { .type = NLA_U32 },
	[NFTA_LOG_QTHRESHOLD]	= { .type = NLA_U16 },
	[NFTA_LOG_LEVEL]	= { .type = NLA_U32 },
	[NFTA_LOG_FLAGS]	= { .type = NLA_U32 },
};

static int nft_log_modprobe(struct net *net, enum nf_log_type t)
{
	switch (t) {
	case NF_LOG_TYPE_LOG:
		return nft_request_module(net, "%s", "nf_log_syslog");
	case NF_LOG_TYPE_ULOG:
		return nft_request_module(net, "%s", "nfnetlink_log");
	case NF_LOG_TYPE_MAX:
		break;
	}

	return -ENOENT;
}

static int nft_log_init(const struct nft_ctx *ctx,
			const struct nft_expr *expr,
			const struct nlattr * const tb[])
{
	struct nft_log *priv = nft_expr_priv(expr);
	struct nf_loginfo *li = &priv->loginfo;
	const struct nlattr *nla;
	int err;

	li->type = NF_LOG_TYPE_LOG;
	if (tb[NFTA_LOG_LEVEL] != NULL &&
	    tb[NFTA_LOG_GROUP] != NULL)
		return -EINVAL;
	if (tb[NFTA_LOG_GROUP] != NULL) {
		li->type = NF_LOG_TYPE_ULOG;
		if (tb[NFTA_LOG_FLAGS] != NULL)
			return -EINVAL;
	}

	nla = tb[NFTA_LOG_PREFIX];
	if (nla != NULL) {
		priv->prefix = kmalloc(nla_len(nla) + 1, GFP_KERNEL);
		if (priv->prefix == NULL)
			return -ENOMEM;
		nla_strscpy(priv->prefix, nla, nla_len(nla) + 1);
	} else {
		priv->prefix = (char *)nft_log_null_prefix;
	}

	switch (li->type) {
	case NF_LOG_TYPE_LOG:
		if (tb[NFTA_LOG_LEVEL] != NULL) {
			li->u.log.level =
				ntohl(nla_get_be32(tb[NFTA_LOG_LEVEL]));
		} else {
			li->u.log.level = NFT_LOGLEVEL_WARNING;
		}
		if (li->u.log.level > NFT_LOGLEVEL_AUDIT) {
			err = -EINVAL;
			goto err1;
		}

		if (tb[NFTA_LOG_FLAGS] != NULL) {
			li->u.log.logflags =
				ntohl(nla_get_be32(tb[NFTA_LOG_FLAGS]));
			if (li->u.log.logflags & ~NF_LOG_MASK) {
				err = -EINVAL;
				goto err1;
			}
		}
		break;
	case NF_LOG_TYPE_ULOG:
		li->u.ulog.group = ntohs(nla_get_be16(tb[NFTA_LOG_GROUP]));
		if (tb[NFTA_LOG_SNAPLEN] != NULL) {
			li->u.ulog.flags |= NF_LOG_F_COPY_LEN;
			li->u.ulog.copy_len =
				ntohl(nla_get_be32(tb[NFTA_LOG_SNAPLEN]));
		}
		if (tb[NFTA_LOG_QTHRESHOLD] != NULL) {
			li->u.ulog.qthreshold =
				ntohs(nla_get_be16(tb[NFTA_LOG_QTHRESHOLD]));
		}
		break;
	}

	if (li->u.log.level == NFT_LOGLEVEL_AUDIT)
		return 0;

	err = nf_logger_find_get(ctx->family, li->type);
	if (err < 0) {
		if (nft_log_modprobe(ctx->net, li->type) == -EAGAIN)
			err = -EAGAIN;

		goto err1;
	}

	return 0;

err1:
	if (priv->prefix != nft_log_null_prefix)
		kfree(priv->prefix);
	return err;
}

static void nft_log_destroy(const struct nft_ctx *ctx,
			    const struct nft_expr *expr)
{
	struct nft_log *priv = nft_expr_priv(expr);
	struct nf_loginfo *li = &priv->loginfo;

	if (priv->prefix != nft_log_null_prefix)
		kfree(priv->prefix);

	if (li->u.log.level == NFT_LOGLEVEL_AUDIT)
		return;

	nf_logger_put(ctx->family, li->type);
}

static int nft_log_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
	const struct nft_log *priv = nft_expr_priv(expr);
	const struct nf_loginfo *li = &priv->loginfo;

	if (priv->prefix != nft_log_null_prefix)
		if (nla_put_string(skb, NFTA_LOG_PREFIX, priv->prefix))
			goto nla_put_failure;
	switch (li->type) {
	case NF_LOG_TYPE_LOG:
		if (nla_put_be32(skb, NFTA_LOG_LEVEL, htonl(li->u.log.level)))
			goto nla_put_failure;

		if (li->u.log.logflags) {
			if (nla_put_be32(skb, NFTA_LOG_FLAGS,
					 htonl(li->u.log.logflags)))
				goto nla_put_failure;
		}
		break;
	case NF_LOG_TYPE_ULOG:
		if (nla_put_be16(skb, NFTA_LOG_GROUP, htons(li->u.ulog.group)))
			goto nla_put_failure;

		if (li->u.ulog.flags & NF_LOG_F_COPY_LEN) {
			if (nla_put_be32(skb, NFTA_LOG_SNAPLEN,
					 htonl(li->u.ulog.copy_len)))
				goto nla_put_failure;
		}
		if (li->u.ulog.qthreshold) {
			if (nla_put_be16(skb, NFTA_LOG_QTHRESHOLD,
					 htons(li->u.ulog.qthreshold)))
				goto nla_put_failure;
		}
		break;
	}
	return 0;

nla_put_failure:
	return -1;
}

static struct nft_expr_type nft_log_type;
static const struct nft_expr_ops nft_log_ops = {
	.type		= &nft_log_type,
	.size		= NFT_EXPR_SIZE(sizeof(struct nft_log)),
	.eval		= nft_log_eval,
	.init		= nft_log_init,
	.destroy	= nft_log_destroy,
	.dump		= nft_log_dump,
	.reduce		= NFT_REDUCE_READONLY,
};

static struct nft_expr_type nft_log_type __read_mostly = {
	.name		= "log",
	.ops		= &nft_log_ops,
	.policy		= nft_log_policy,
	.maxattr	= NFTA_LOG_MAX,
	.owner		= THIS_MODULE,
};

static int __init nft_log_module_init(void)
{
	return nft_register_expr(&nft_log_type);
}

static void __exit nft_log_module_exit(void)
{
	nft_unregister_expr(&nft_log_type);
}

module_init(nft_log_module_init);
module_exit(nft_log_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_ALIAS_NFT_EXPR("log");
MODULE_DESCRIPTION("Netfilter nf_tables log module");