xt_AUDIT.c

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/*
 * Creates audit record for dropped/accepted packets
 *
 * (C) 2010-2011 Thomas Graf <[email protected]>
 * (C) 2010-2011 Red Hat, Inc.
 *
 * 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/audit.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/if_arp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_AUDIT.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <net/ipv6.h>
#include <net/ip.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Thomas Graf <[email protected]>");
MODULE_DESCRIPTION("Xtables: creates audit records for dropped/accepted packets");
MODULE_ALIAS("ipt_AUDIT");
MODULE_ALIAS("ip6t_AUDIT");
MODULE_ALIAS("ebt_AUDIT");
MODULE_ALIAS("arpt_AUDIT");

static void audit_proto(struct audit_buffer *ab, struct sk_buff *skb,
            unsigned int proto, unsigned int offset)
{
    switch (proto) {
    case IPPROTO_TCP:
    case IPPROTO_UDP:
    case IPPROTO_UDPLITE: {
        const __be16 *pptr;
        __be16 _ports[2];

        pptr = skb_header_pointer(skb, offset, sizeof(_ports), _ports);
        if (pptr == NULL) {
            audit_log_format(ab, " truncated=1");
            return;
        }

        audit_log_format(ab, " sport=%hu dport=%hu",
                 ntohs(pptr[0]), ntohs(pptr[1]));
        }
        break;

    case IPPROTO_ICMP:
    case IPPROTO_ICMPV6: {
        const u8 *iptr;
        u8 _ih[2];

        iptr = skb_header_pointer(skb, offset, sizeof(_ih), &_ih);
        if (iptr == NULL) {
            audit_log_format(ab, " truncated=1");
            return;
        }

        audit_log_format(ab, " icmptype=%hhu icmpcode=%hhu",
                 iptr[0], iptr[1]);

        }
        break;
    }
}

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

    ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
    if (!ih) {
        audit_log_format(ab, " truncated=1");
        return;
    }

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

    if (ntohs(ih->frag_off) & IP_OFFSET) {
        audit_log_format(ab, " frag=1");
        return;
    }

    audit_proto(ab, skb, ih->protocol, ih->ihl * 4);
}

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

    ih = skb_header_pointer(skb, skb_network_offset(skb), sizeof(_ip6h), &_ip6h);
    if (!ih) {
        audit_log_format(ab, " truncated=1");
        return;
    }

    nexthdr = ih->nexthdr;
    offset = 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);

    if (offset)
        audit_proto(ab, skb, nexthdr, offset);
}

static unsigned int
audit_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
    const struct xt_audit_info *info = par->targinfo;
    struct audit_buffer *ab;

    ab = audit_log_start(NULL, GFP_ATOMIC, AUDIT_NETFILTER_PKT);
    if (ab == NULL)
        goto errout;

    audit_log_format(ab, "action=%hhu hook=%u len=%u inif=%s outif=%s",
             info->type, par->hooknum, skb->len,
             par->in ? par->in->name : "?",
             par->out ? par->out->name : "?");

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

    if (skb->dev && skb->dev->type == ARPHRD_ETHER) {
        audit_log_format(ab, " smac=%pM dmac=%pM macproto=0x%04x",
                 eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest,
                 ntohs(eth_hdr(skb)->h_proto));

        if (par->family == NFPROTO_BRIDGE) {
            switch (eth_hdr(skb)->h_proto) {
            case __constant_htons(ETH_P_IP):
                audit_ip4(ab, skb);
                break;

            case __constant_htons(ETH_P_IPV6):
                audit_ip6(ab, skb);
                break;
            }
        }
    }

    switch (par->family) {
    case NFPROTO_IPV4:
        audit_ip4(ab, skb);
        break;

    case NFPROTO_IPV6:
        audit_ip6(ab, skb);
        break;
    }

#ifdef CONFIG_NETWORK_SECMARK
    if (skb->secmark)
        audit_log_secctx(ab, skb->secmark);
#endif

    audit_log_end(ab);

errout:
    return XT_CONTINUE;
}

static unsigned int
audit_tg_ebt(struct sk_buff *skb, const struct xt_action_param *par)
{
    audit_tg(skb, par);
    return EBT_CONTINUE;
}

static int audit_tg_check(const struct xt_tgchk_param *par)
{
    const struct xt_audit_info *info = par->targinfo;

    if (info->type > XT_AUDIT_TYPE_MAX) {
        pr_info("Audit type out of range (valid range: 0..%hhu)\n",
            XT_AUDIT_TYPE_MAX);
        return -ERANGE;
    }

    return 0;
}

static struct xt_target audit_tg_reg[] __read_mostly = {
    {
        .name       = "AUDIT",
        .family     = NFPROTO_UNSPEC,
        .target     = audit_tg,
        .targetsize = sizeof(struct xt_audit_info),
        .checkentry = audit_tg_check,
        .me     = THIS_MODULE,
    },
    {
        .name       = "AUDIT",
        .family     = NFPROTO_BRIDGE,
        .target     = audit_tg_ebt,
        .targetsize = sizeof(struct xt_audit_info),
        .checkentry = audit_tg_check,
        .me     = THIS_MODULE,
    },
};

static int __init audit_tg_init(void)
{
    return xt_register_targets(audit_tg_reg, ARRAY_SIZE(audit_tg_reg));
}

static void __exit audit_tg_exit(void)
{
    xt_unregister_targets(audit_tg_reg, ARRAY_SIZE(audit_tg_reg));
}

module_init(audit_tg_init);
module_exit(audit_tg_exit);