xt_recent.c

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/*
 * Copyright (c) 2006 Patrick McHardy <[email protected]>
 * Copyright © CC Computer Consultants GmbH, 2007 - 2008
 *
 * 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.
 *
 * This is a replacement of the old ipt_recent module, which carried the
 * following copyright notice:
 *
 * Author: Stephen Frost <[email protected]>
 * Copyright 2002-2003, Stephen Frost, 2.5.x port by [email protected]
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/bitops.h>
#include <linux/skbuff.h>
#include <linux/inet.h>
#include <linux/slab.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_recent.h>

MODULE_AUTHOR("Patrick McHardy <[email protected]>");
MODULE_AUTHOR("Jan Engelhardt <[email protected]>");
MODULE_DESCRIPTION("Xtables: \"recently-seen\" host matching");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_recent");
MODULE_ALIAS("ip6t_recent");

static unsigned int ip_list_tot = 100;
static unsigned int ip_pkt_list_tot = 20;
static unsigned int ip_list_hash_size = 0;
static unsigned int ip_list_perms = 0644;
static unsigned int ip_list_uid = 0;
static unsigned int ip_list_gid = 0;
module_param(ip_list_tot, uint, 0400);
module_param(ip_pkt_list_tot, uint, 0400);
module_param(ip_list_hash_size, uint, 0400);
module_param(ip_list_perms, uint, 0400);
module_param(ip_list_uid, uint, S_IRUGO | S_IWUSR);
module_param(ip_list_gid, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(ip_list_tot, "number of IPs to remember per list");
MODULE_PARM_DESC(ip_pkt_list_tot, "number of packets per IP address to remember (max. 255)");
MODULE_PARM_DESC(ip_list_hash_size, "size of hash table used to look up IPs");
MODULE_PARM_DESC(ip_list_perms, "permissions on /proc/net/xt_recent/* files");
MODULE_PARM_DESC(ip_list_uid, "default owner of /proc/net/xt_recent/* files");
MODULE_PARM_DESC(ip_list_gid, "default owning group of /proc/net/xt_recent/* files");

struct recent_entry {
    struct list_head    list;
    struct list_head    lru_list;
    union nf_inet_addr  addr;
    u_int16_t       family;
    u_int8_t        ttl;
    u_int8_t        index;
    u_int16_t       nstamps;
    unsigned long       stamps[0];
};

struct recent_table {
    struct list_head    list;
    char            name[XT_RECENT_NAME_LEN];
    union nf_inet_addr  mask;
    unsigned int        refcnt;
    unsigned int        entries;
    struct list_head    lru_list;
    struct list_head    iphash[0];
};

struct recent_net {
    struct list_head    tables;
#ifdef CONFIG_PROC_FS
    struct proc_dir_entry   *xt_recent;
#endif
};

static int recent_net_id;
static inline struct recent_net *recent_pernet(struct net *net)
{
    return net_generic(net, recent_net_id);
}

static DEFINE_SPINLOCK(recent_lock);
static DEFINE_MUTEX(recent_mutex);

#ifdef CONFIG_PROC_FS
static const struct file_operations recent_old_fops, recent_mt_fops;
#endif

static u_int32_t hash_rnd __read_mostly;
static bool hash_rnd_inited __read_mostly;

static inline unsigned int recent_entry_hash4(const union nf_inet_addr *addr)
{
    return jhash_1word((__force u32)addr->ip, hash_rnd) &
           (ip_list_hash_size - 1);
}

static inline unsigned int recent_entry_hash6(const union nf_inet_addr *addr)
{
    return jhash2((u32 *)addr->ip6, ARRAY_SIZE(addr->ip6), hash_rnd) &
           (ip_list_hash_size - 1);
}

static struct recent_entry *
recent_entry_lookup(const struct recent_table *table,
            const union nf_inet_addr *addrp, u_int16_t family,
            u_int8_t ttl)
{
    struct recent_entry *e;
    unsigned int h;

    if (family == NFPROTO_IPV4)
        h = recent_entry_hash4(addrp);
    else
        h = recent_entry_hash6(addrp);

    list_for_each_entry(e, &table->iphash[h], list)
        if (e->family == family &&
            memcmp(&e->addr, addrp, sizeof(e->addr)) == 0 &&
            (ttl == e->ttl || ttl == 0 || e->ttl == 0))
            return e;
    return NULL;
}

static void recent_entry_remove(struct recent_table *t, struct recent_entry *e)
{
    list_del(&e->list);
    list_del(&e->lru_list);
    kfree(e);
    t->entries--;
}

/*
 * Drop entries with timestamps older then 'time'.
 */
static void recent_entry_reap(struct recent_table *t, unsigned long time)
{
    struct recent_entry *e;

    /*
     * The head of the LRU list is always the oldest entry.
     */
    e = list_entry(t->lru_list.next, struct recent_entry, lru_list);

    /*
     * The last time stamp is the most recent.
     */
    if (time_after(time, e->stamps[e->index-1]))
        recent_entry_remove(t, e);
}

static struct recent_entry *
recent_entry_init(struct recent_table *t, const union nf_inet_addr *addr,
          u_int16_t family, u_int8_t ttl)
{
    struct recent_entry *e;

    if (t->entries >= ip_list_tot) {
        e = list_entry(t->lru_list.next, struct recent_entry, lru_list);
        recent_entry_remove(t, e);
    }
    e = kmalloc(sizeof(*e) + sizeof(e->stamps[0]) * ip_pkt_list_tot,
            GFP_ATOMIC);
    if (e == NULL)
        return NULL;
    memcpy(&e->addr, addr, sizeof(e->addr));
    e->ttl       = ttl;
    e->stamps[0] = jiffies;
    e->nstamps   = 1;
    e->index     = 1;
    e->family    = family;
    if (family == NFPROTO_IPV4)
        list_add_tail(&e->list, &t->iphash[recent_entry_hash4(addr)]);
    else
        list_add_tail(&e->list, &t->iphash[recent_entry_hash6(addr)]);
    list_add_tail(&e->lru_list, &t->lru_list);
    t->entries++;
    return e;
}

static void recent_entry_update(struct recent_table *t, struct recent_entry *e)
{
    e->index %= ip_pkt_list_tot;
    e->stamps[e->index++] = jiffies;
    if (e->index > e->nstamps)
        e->nstamps = e->index;
    list_move_tail(&e->lru_list, &t->lru_list);
}

static struct recent_table *recent_table_lookup(struct recent_net *recent_net,
                        const char *name)
{
    struct recent_table *t;

    list_for_each_entry(t, &recent_net->tables, list)
        if (!strcmp(t->name, name))
            return t;
    return NULL;
}

static void recent_table_flush(struct recent_table *t)
{
    struct recent_entry *e, *next;
    unsigned int i;

    for (i = 0; i < ip_list_hash_size; i++)
        list_for_each_entry_safe(e, next, &t->iphash[i], list)
            recent_entry_remove(t, e);
}

static bool
recent_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
    struct net *net = dev_net(par->in ? par->in : par->out);
    struct recent_net *recent_net = recent_pernet(net);
    const struct xt_recent_mtinfo_v1 *info = par->matchinfo;
    struct recent_table *t;
    struct recent_entry *e;
    union nf_inet_addr addr = {}, addr_mask;
    u_int8_t ttl;
    bool ret = info->invert;

    if (par->family == NFPROTO_IPV4) {
        const struct iphdr *iph = ip_hdr(skb);

        if (info->side == XT_RECENT_DEST)
            addr.ip = iph->daddr;
        else
            addr.ip = iph->saddr;

        ttl = iph->ttl;
    } else {
        const struct ipv6hdr *iph = ipv6_hdr(skb);

        if (info->side == XT_RECENT_DEST)
            memcpy(&addr.in6, &iph->daddr, sizeof(addr.in6));
        else
            memcpy(&addr.in6, &iph->saddr, sizeof(addr.in6));

        ttl = iph->hop_limit;
    }

    /* use TTL as seen before forwarding */
    if (par->out != NULL && skb->sk == NULL)
        ttl++;

    spin_lock_bh(&recent_lock);
    t = recent_table_lookup(recent_net, info->name);

    nf_inet_addr_mask(&addr, &addr_mask, &t->mask);

    e = recent_entry_lookup(t, &addr_mask, par->family,
                (info->check_set & XT_RECENT_TTL) ? ttl : 0);
    if (e == NULL) {
        if (!(info->check_set & XT_RECENT_SET))
            goto out;
        e = recent_entry_init(t, &addr_mask, par->family, ttl);
        if (e == NULL)
            par->hotdrop = true;
        ret = !ret;
        goto out;
    }

    if (info->check_set & XT_RECENT_SET)
        ret = !ret;
    else if (info->check_set & XT_RECENT_REMOVE) {
        recent_entry_remove(t, e);
        ret = !ret;
    } else if (info->check_set & (XT_RECENT_CHECK | XT_RECENT_UPDATE)) {
        unsigned long time = jiffies - info->seconds * HZ;
        unsigned int i, hits = 0;

        for (i = 0; i < e->nstamps; i++) {
            if (info->seconds && time_after(time, e->stamps[i]))
                continue;
            if (!info->hit_count || ++hits >= info->hit_count) {
                ret = !ret;
                break;
            }
        }

        /* info->seconds must be non-zero */
        if (info->check_set & XT_RECENT_REAP)
            recent_entry_reap(t, time);
    }

    if (info->check_set & XT_RECENT_SET ||
        (info->check_set & XT_RECENT_UPDATE && ret)) {
        recent_entry_update(t, e);
        e->ttl = ttl;
    }
out:
    spin_unlock_bh(&recent_lock);
    return ret;
}

static int recent_mt_check(const struct xt_mtchk_param *par,
               const struct xt_recent_mtinfo_v1 *info)
{
    struct recent_net *recent_net = recent_pernet(par->net);
    struct recent_table *t;
#ifdef CONFIG_PROC_FS
    struct proc_dir_entry *pde;
    kuid_t uid;
    kgid_t gid;
#endif
    unsigned int i;
    int ret = -EINVAL;

    if (unlikely(!hash_rnd_inited)) {
        get_random_bytes(&hash_rnd, sizeof(hash_rnd));
        hash_rnd_inited = true;
    }
    if (info->check_set & ~XT_RECENT_VALID_FLAGS) {
        pr_info("Unsupported user space flags (%08x)\n",
            info->check_set);
        return -EINVAL;
    }
    if (hweight8(info->check_set &
             (XT_RECENT_SET | XT_RECENT_REMOVE |
              XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1)
        return -EINVAL;
    if ((info->check_set & (XT_RECENT_SET | XT_RECENT_REMOVE)) &&
        (info->seconds || info->hit_count ||
        (info->check_set & XT_RECENT_MODIFIERS)))
        return -EINVAL;
    if ((info->check_set & XT_RECENT_REAP) && !info->seconds)
        return -EINVAL;
    if (info->hit_count > ip_pkt_list_tot) {
        pr_info("hitcount (%u) is larger than "
            "packets to be remembered (%u)\n",
            info->hit_count, ip_pkt_list_tot);
        return -EINVAL;
    }
    if (info->name[0] == '\0' ||
        strnlen(info->name, XT_RECENT_NAME_LEN) == XT_RECENT_NAME_LEN)
        return -EINVAL;

    mutex_lock(&recent_mutex);
    t = recent_table_lookup(recent_net, info->name);
    if (t != NULL) {
        t->refcnt++;
        ret = 0;
        goto out;
    }

    t = kzalloc(sizeof(*t) + sizeof(t->iphash[0]) * ip_list_hash_size,
            GFP_KERNEL);
    if (t == NULL) {
        ret = -ENOMEM;
        goto out;
    }
    t->refcnt = 1;

    memcpy(&t->mask, &info->mask, sizeof(t->mask));
    strcpy(t->name, info->name);
    INIT_LIST_HEAD(&t->lru_list);
    for (i = 0; i < ip_list_hash_size; i++)
        INIT_LIST_HEAD(&t->iphash[i]);
#ifdef CONFIG_PROC_FS
    uid = make_kuid(&init_user_ns, ip_list_uid);
    gid = make_kgid(&init_user_ns, ip_list_gid);
    if (!uid_valid(uid) || !gid_valid(gid)) {
        kfree(t);
        ret = -EINVAL;
        goto out;
    }
    pde = proc_create_data(t->name, ip_list_perms, recent_net->xt_recent,
          &recent_mt_fops, t);
    if (pde == NULL) {
        kfree(t);
        ret = -ENOMEM;
        goto out;
    }
    pde->uid = uid;
    pde->gid = gid;
#endif
    spin_lock_bh(&recent_lock);
    list_add_tail(&t->list, &recent_net->tables);
    spin_unlock_bh(&recent_lock);
    ret = 0;
out:
    mutex_unlock(&recent_mutex);
    return ret;
}

static int recent_mt_check_v0(const struct xt_mtchk_param *par)
{
    const struct xt_recent_mtinfo_v0 *info_v0 = par->matchinfo;
    struct xt_recent_mtinfo_v1 info_v1;

    /* Copy revision 0 structure to revision 1 */
    memcpy(&info_v1, info_v0, sizeof(struct xt_recent_mtinfo));
    /* Set default mask to ensure backward compatible behaviour */
    memset(info_v1.mask.all, 0xFF, sizeof(info_v1.mask.all));

    return recent_mt_check(par, &info_v1);
}

static int recent_mt_check_v1(const struct xt_mtchk_param *par)
{
    return recent_mt_check(par, par->matchinfo);
}

static void recent_mt_destroy(const struct xt_mtdtor_param *par)
{
    struct recent_net *recent_net = recent_pernet(par->net);
    const struct xt_recent_mtinfo_v1 *info = par->matchinfo;
    struct recent_table *t;

    mutex_lock(&recent_mutex);
    t = recent_table_lookup(recent_net, info->name);
    if (--t->refcnt == 0) {
        spin_lock_bh(&recent_lock);
        list_del(&t->list);
        spin_unlock_bh(&recent_lock);
#ifdef CONFIG_PROC_FS
        remove_proc_entry(t->name, recent_net->xt_recent);
#endif
        recent_table_flush(t);
        kfree(t);
    }
    mutex_unlock(&recent_mutex);
}

#ifdef CONFIG_PROC_FS
struct recent_iter_state {
    const struct recent_table *table;
    unsigned int        bucket;
};

static void *recent_seq_start(struct seq_file *seq, loff_t *pos)
    __acquires(recent_lock)
{
    struct recent_iter_state *st = seq->private;
    const struct recent_table *t = st->table;
    struct recent_entry *e;
    loff_t p = *pos;

    spin_lock_bh(&recent_lock);

    for (st->bucket = 0; st->bucket < ip_list_hash_size; st->bucket++)
        list_for_each_entry(e, &t->iphash[st->bucket], list)
            if (p-- == 0)
                return e;
    return NULL;
}

static void *recent_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct recent_iter_state *st = seq->private;
    const struct recent_table *t = st->table;
    const struct recent_entry *e = v;
    const struct list_head *head = e->list.next;

    while (head == &t->iphash[st->bucket]) {
        if (++st->bucket >= ip_list_hash_size)
            return NULL;
        head = t->iphash[st->bucket].next;
    }
    (*pos)++;
    return list_entry(head, struct recent_entry, list);
}

static void recent_seq_stop(struct seq_file *s, void *v)
    __releases(recent_lock)
{
    spin_unlock_bh(&recent_lock);
}

static int recent_seq_show(struct seq_file *seq, void *v)
{
    const struct recent_entry *e = v;
    unsigned int i;

    i = (e->index - 1) % ip_pkt_list_tot;
    if (e->family == NFPROTO_IPV4)
        seq_printf(seq, "src=%pI4 ttl: %u last_seen: %lu oldest_pkt: %u",
               &e->addr.ip, e->ttl, e->stamps[i], e->index);
    else
        seq_printf(seq, "src=%pI6 ttl: %u last_seen: %lu oldest_pkt: %u",
               &e->addr.in6, e->ttl, e->stamps[i], e->index);
    for (i = 0; i < e->nstamps; i++)
        seq_printf(seq, "%s %lu", i ? "," : "", e->stamps[i]);
    seq_printf(seq, "\n");
    return 0;
}

static const struct seq_operations recent_seq_ops = {
    .start      = recent_seq_start,
    .next       = recent_seq_next,
    .stop       = recent_seq_stop,
    .show       = recent_seq_show,
};

static int recent_seq_open(struct inode *inode, struct file *file)
{
    struct proc_dir_entry *pde = PDE(inode);
    struct recent_iter_state *st;

    st = __seq_open_private(file, &recent_seq_ops, sizeof(*st));
    if (st == NULL)
        return -ENOMEM;

    st->table    = pde->data;
    return 0;
}

static ssize_t
recent_mt_proc_write(struct file *file, const char __user *input,
             size_t size, loff_t *loff)
{
    const struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
    struct recent_table *t = pde->data;
    struct recent_entry *e;
    char buf[sizeof("+b335:1d35:1e55:dead:c0de:1715:5afe:c0de")];
    const char *c = buf;
    union nf_inet_addr addr = {};
    u_int16_t family;
    bool add, succ;

    if (size == 0)
        return 0;
    if (size > sizeof(buf))
        size = sizeof(buf);
    if (copy_from_user(buf, input, size) != 0)
        return -EFAULT;

    /* Strict protocol! */
    if (*loff != 0)
        return -ESPIPE;
    switch (*c) {
    case '/': /* flush table */
        spin_lock_bh(&recent_lock);
        recent_table_flush(t);
        spin_unlock_bh(&recent_lock);
        return size;
    case '-': /* remove address */
        add = false;
        break;
    case '+': /* add address */
        add = true;
        break;
    default:
        pr_info("Need \"+ip\", \"-ip\" or \"/\"\n");
        return -EINVAL;
    }

    ++c;
    --size;
    if (strnchr(c, size, ':') != NULL) {
        family = NFPROTO_IPV6;
        succ   = in6_pton(c, size, (void *)&addr, '\n', NULL);
    } else {
        family = NFPROTO_IPV4;
        succ   = in4_pton(c, size, (void *)&addr, '\n', NULL);
    }

    if (!succ) {
        pr_info("illegal address written to procfs\n");
        return -EINVAL;
    }

    spin_lock_bh(&recent_lock);
    e = recent_entry_lookup(t, &addr, family, 0);
    if (e == NULL) {
        if (add)
            recent_entry_init(t, &addr, family, 0);
    } else {
        if (add)
            recent_entry_update(t, e);
        else
            recent_entry_remove(t, e);
    }
    spin_unlock_bh(&recent_lock);
    /* Note we removed one above */
    *loff += size + 1;
    return size + 1;
}

static const struct file_operations recent_mt_fops = {
    .open    = recent_seq_open,
    .read    = seq_read,
    .write   = recent_mt_proc_write,
    .release = seq_release_private,
    .owner   = THIS_MODULE,
    .llseek = seq_lseek,
};

static int __net_init recent_proc_net_init(struct net *net)
{
    struct recent_net *recent_net = recent_pernet(net);

    recent_net->xt_recent = proc_mkdir("xt_recent", net->proc_net);
    if (!recent_net->xt_recent)
        return -ENOMEM;
    return 0;
}

static void __net_exit recent_proc_net_exit(struct net *net)
{
    proc_net_remove(net, "xt_recent");
}
#else
static inline int recent_proc_net_init(struct net *net)
{
    return 0;
}

static inline void recent_proc_net_exit(struct net *net)
{
}
#endif /* CONFIG_PROC_FS */

static int __net_init recent_net_init(struct net *net)
{
    struct recent_net *recent_net = recent_pernet(net);

    INIT_LIST_HEAD(&recent_net->tables);
    return recent_proc_net_init(net);
}

static void __net_exit recent_net_exit(struct net *net)
{
    struct recent_net *recent_net = recent_pernet(net);

    BUG_ON(!list_empty(&recent_net->tables));
    recent_proc_net_exit(net);
}

static struct pernet_operations recent_net_ops = {
    .init   = recent_net_init,
    .exit   = recent_net_exit,
    .id = &recent_net_id,
    .size   = sizeof(struct recent_net),
};

static struct xt_match recent_mt_reg[] __read_mostly = {
    {
        .name       = "recent",
        .revision   = 0,
        .family     = NFPROTO_IPV4,
        .match      = recent_mt,
        .matchsize  = sizeof(struct xt_recent_mtinfo),
        .checkentry = recent_mt_check_v0,
        .destroy    = recent_mt_destroy,
        .me         = THIS_MODULE,
    },
    {
        .name       = "recent",
        .revision   = 0,
        .family     = NFPROTO_IPV6,
        .match      = recent_mt,
        .matchsize  = sizeof(struct xt_recent_mtinfo),
        .checkentry = recent_mt_check_v0,
        .destroy    = recent_mt_destroy,
        .me         = THIS_MODULE,
    },
    {
        .name       = "recent",
        .revision   = 1,
        .family     = NFPROTO_IPV4,
        .match      = recent_mt,
        .matchsize  = sizeof(struct xt_recent_mtinfo_v1),
        .checkentry = recent_mt_check_v1,
        .destroy    = recent_mt_destroy,
        .me         = THIS_MODULE,
    },
    {
        .name       = "recent",
        .revision   = 1,
        .family     = NFPROTO_IPV6,
        .match      = recent_mt,
        .matchsize  = sizeof(struct xt_recent_mtinfo_v1),
        .checkentry = recent_mt_check_v1,
        .destroy    = recent_mt_destroy,
        .me         = THIS_MODULE,
    }
};

static int __init recent_mt_init(void)
{
    int err;

    if (!ip_list_tot || !ip_pkt_list_tot || ip_pkt_list_tot > 255)
        return -EINVAL;
    ip_list_hash_size = 1 << fls(ip_list_tot);

    err = register_pernet_subsys(&recent_net_ops);
    if (err)
        return err;
    err = xt_register_matches(recent_mt_reg, ARRAY_SIZE(recent_mt_reg));
    if (err)
        unregister_pernet_subsys(&recent_net_ops);
    return err;
}

static void __exit recent_mt_exit(void)
{
    xt_unregister_matches(recent_mt_reg, ARRAY_SIZE(recent_mt_reg));
    unregister_pernet_subsys(&recent_net_ops);
}

module_init(recent_mt_init);
module_exit(recent_mt_exit);