root/net/netfilter/xt_SECMARK.c

DEFINITIONS

1. secmark_tg
2. checkentry_selinux
3. secmark_tg_check
4. secmark_tg_destroy
5. secmark_tg_init
6. secmark_tg_exit

/*
 * Module for modifying the secmark field of the skb, for use by
 * security subsystems.
 *
 * Based on the nfmark match by:
 * (C) 1999-2001 Marc Boucher <marc@mbsi.ca>
 *
 * (C) 2006,2008 Red Hat, Inc., James Morris <jmorris@redhat.com>
 *
 * 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.
 *
 */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/selinux.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_SECMARK.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Morris <jmorris@redhat.com>");
MODULE_DESCRIPTION("Xtables: packet security mark modification");
MODULE_ALIAS("ipt_SECMARK");
MODULE_ALIAS("ip6t_SECMARK");

#define PFX "SECMARK: "

static u8 mode;

static unsigned int
secmark_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        u32 secmark = 0;
        const struct xt_secmark_target_info *info = par->targinfo;

        BUG_ON(info->mode != mode);

        switch (mode) {
        case SECMARK_MODE_SEL:
                secmark = info->u.sel.selsid;
                break;

        default:
                BUG();
        }

        skb->secmark = secmark;
        return XT_CONTINUE;
}

static bool checkentry_selinux(struct xt_secmark_target_info *info)
{
        int err;
        struct xt_secmark_target_selinux_info *sel = &info->u.sel;

        sel->selctx[SECMARK_SELCTX_MAX - 1] = '\0';

        err = selinux_string_to_sid(sel->selctx, &sel->selsid);
        if (err) {
                if (err == -EINVAL)
                        printk(KERN_INFO PFX "invalid SELinux context \'%s\'\n",
                               sel->selctx);
                return false;
        }

        if (!sel->selsid) {
                printk(KERN_INFO PFX "unable to map SELinux context \'%s\'\n",
                       sel->selctx);
                return false;
        }

        err = selinux_secmark_relabel_packet_permission(sel->selsid);
        if (err) {
                printk(KERN_INFO PFX "unable to obtain relabeling permission\n");
                return false;
        }

        selinux_secmark_refcount_inc();
        return true;
}

static bool secmark_tg_check(const struct xt_tgchk_param *par)
{
        struct xt_secmark_target_info *info = par->targinfo;

        if (strcmp(par->table, "mangle") != 0 &&
            strcmp(par->table, "security") != 0) {
                printk(KERN_INFO PFX "target only valid in the \'mangle\' "
                       "or \'security\' tables, not \'%s\'.\n", par->table);
                return false;
        }

        if (mode && mode != info->mode) {
                printk(KERN_INFO PFX "mode already set to %hu cannot mix with "
                       "rules for mode %hu\n", mode, info->mode);
                return false;
        }

        switch (info->mode) {
        case SECMARK_MODE_SEL:
                if (!checkentry_selinux(info))
                        return false;
                break;

        default:
                printk(KERN_INFO PFX "invalid mode: %hu\n", info->mode);
                return false;
        }

        if (!mode)
                mode = info->mode;
        return true;
}

static void secmark_tg_destroy(const struct xt_tgdtor_param *par)
{
        switch (mode) {
        case SECMARK_MODE_SEL:
                selinux_secmark_refcount_dec();
        }
}

static struct xt_target secmark_tg_reg __read_mostly = {
        .name       = "SECMARK",
        .revision   = 0,
        .family     = NFPROTO_UNSPEC,
        .checkentry = secmark_tg_check,
        .destroy    = secmark_tg_destroy,
        .target     = secmark_tg,
        .targetsize = sizeof(struct xt_secmark_target_info),
        .me         = THIS_MODULE,
};

static int __init secmark_tg_init(void)
{
        return xt_register_target(&secmark_tg_reg);
}

static void __exit secmark_tg_exit(void)
{
        xt_unregister_target(&secmark_tg_reg);
}

module_init(secmark_tg_init);
module_exit(secmark_tg_exit);