net/netfilter/xt_SECMARK.c

   1 /*
   2  * Module for modifying the secmark field of the skb, for use by
   3  * security subsystems.
   4  *
   5  * Based on the nfmark match by:
   6  * (C) 1999-2001 Marc Boucher <marc@mbsi.ca>
   7  *
   8  * (C) 2006 Red Hat, Inc., James Morris <jmorris@redhat.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  *
  14  */
  15 #include <linux/module.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/selinux.h>
  18 #include <linux/netfilter/x_tables.h>
  19 #include <linux/netfilter/xt_SECMARK.h>
  20
  21 MODULE_LICENSE("GPL");
  22 MODULE_AUTHOR("James Morris <jmorris@redhat.com>");
  23 MODULE_DESCRIPTION("ip[6]tables SECMARK modification module");
  24 MODULE_ALIAS("ipt_SECMARK");
  25 MODULE_ALIAS("ip6t_SECMARK");
  26
  27 #define PFX "SECMARK: "
  28
  29 static u8 mode;
  30
  31 static unsigned int target(struct sk_buff *skb, const struct net_device *in,
  32                            const struct net_device *out, unsigned int hooknum,
  33                            const struct xt_target *target,
  34                            const void *targinfo)
  35 {
  36         u32 secmark = 0;
  37         const struct xt_secmark_target_info *info = targinfo;
  38
  39         BUG_ON(info->mode != mode);
  40
  41         switch (mode) {
  42         case SECMARK_MODE_SEL:
  43                 secmark = info->u.sel.selsid;
  44                 break;
  45
  46         default:
  47                 BUG();
  48         }
  49
  50         skb->secmark = secmark;
  51         return XT_CONTINUE;
  52 }
  53
  54 static bool checkentry_selinux(struct xt_secmark_target_info *info)
  55 {
  56         int err;
  57         struct xt_secmark_target_selinux_info *sel = &info->u.sel;
  58
  59         sel->selctx[SECMARK_SELCTX_MAX - 1] = '\0';
  60
  61         err = selinux_string_to_sid(sel->selctx, &sel->selsid);
  62         if (err) {
  63                 if (err == -EINVAL)
  64                         printk(KERN_INFO PFX "invalid SELinux context \'%s\'\n",
  65                                sel->selctx);
  66                 return false;
  67         }
  68
  69         if (!sel->selsid) {
  70                 printk(KERN_INFO PFX "unable to map SELinux context \'%s\'\n",
  71                        sel->selctx);
  72                 return false;
  73         }
  74
  75         err = selinux_relabel_packet_permission(sel->selsid);
  76         if (err) {
  77                 printk(KERN_INFO PFX "unable to obtain relabeling permission\n");
  78                 return false;
  79         }
  80
  81         return true;
  82 }
  83
  84 static bool checkentry(const char *tablename, const void *entry,
  85                        const struct xt_target *target, void *targinfo,
  86                        unsigned int hook_mask)
  87 {
  88         struct xt_secmark_target_info *info = targinfo;
  89
  90         if (mode && mode != info->mode) {
  91                 printk(KERN_INFO PFX "mode already set to %hu cannot mix with "
  92                        "rules for mode %hu\n", mode, info->mode);
  93                 return false;
  94         }
  95
  96         switch (info->mode) {
  97         case SECMARK_MODE_SEL:
  98                 if (!checkentry_selinux(info))
  99                         return false;
 100                 break;
 101
 102         default:
 103                 printk(KERN_INFO PFX "invalid mode: %hu\n", info->mode);
 104                 return false;
 105         }
 106
 107         if (!mode)
 108                 mode = info->mode;
 109         return true;
 110 }
 111
 112 static struct xt_target xt_secmark_target[] __read_mostly = {
 113         {
 114                 .name           = "SECMARK",
 115                 .family         = AF_INET,
 116                 .checkentry     = checkentry,
 117                 .target         = target,
 118                 .targetsize     = sizeof(struct xt_secmark_target_info),
 119                 .table          = "mangle",
 120                 .me             = THIS_MODULE,
 121         },
 122         {
 123                 .name           = "SECMARK",
 124                 .family         = AF_INET6,
 125                 .checkentry     = checkentry,
 126                 .target         = target,
 127                 .targetsize     = sizeof(struct xt_secmark_target_info),
 128                 .table          = "mangle",
 129                 .me             = THIS_MODULE,
 130         },
 131 };
 132
 133 static int __init xt_secmark_init(void)
 134 {
 135         return xt_register_targets(xt_secmark_target,
 136                                    ARRAY_SIZE(xt_secmark_target));
 137 }
 138
 139 static void __exit xt_secmark_fini(void)
 140 {
 141         xt_unregister_targets(xt_secmark_target, ARRAY_SIZE(xt_secmark_target));
 142 }
 143
 144 module_init(xt_secmark_init);
 145 module_exit(xt_secmark_fini);