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) 2006,2008 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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  16 #include <linux/module.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/selinux.h>
  19 #include <linux/netfilter/x_tables.h>
  20 #include <linux/netfilter/xt_SECMARK.h>
  21
  22 MODULE_LICENSE("GPL");
  23 MODULE_AUTHOR("James Morris <jmorris@redhat.com>");
  24 MODULE_DESCRIPTION("Xtables: packet security mark modification");
  25 MODULE_ALIAS("ipt_SECMARK");
  26 MODULE_ALIAS("ip6t_SECMARK");
  27
  28 #define PFX "SECMARK: "
  29
  30 static u8 mode;
  31
  32 static unsigned int
  33 secmark_tg(struct sk_buff *skb, const struct xt_action_param *par)
  34 {
  35         u32 secmark = 0;
  36         const struct xt_secmark_target_info *info = par->targinfo;
  37
  38         BUG_ON(info->mode != mode);
  39
  40         switch (mode) {
  41         case SECMARK_MODE_SEL:
  42                 secmark = info->u.sel.selsid;
  43                 break;
  44
  45         default:
  46                 BUG();
  47         }
  48
  49         skb->secmark = secmark;
  50         return XT_CONTINUE;
  51 }
  52
  53 static int checkentry_selinux(struct xt_secmark_target_info *info)
  54 {
  55         int err;
  56         struct xt_secmark_target_selinux_info *sel = &info->u.sel;
  57
  58         sel->selctx[SECMARK_SELCTX_MAX - 1] = '\0';
  59
  60         err = selinux_string_to_sid(sel->selctx, &sel->selsid);
  61         if (err) {
  62                 if (err == -EINVAL)
  63                         pr_info("invalid SELinux context \'%s\'\n",
  64                                 sel->selctx);
  65                 return err;
  66         }
  67
  68         if (!sel->selsid) {
  69                 pr_info("unable to map SELinux context \'%s\'\n", sel->selctx);
  70                 return -ENOENT;
  71         }
  72
  73         err = selinux_secmark_relabel_packet_permission(sel->selsid);
  74         if (err) {
  75                 pr_info("unable to obtain relabeling permission\n");
  76                 return err;
  77         }
  78
  79         selinux_secmark_refcount_inc();
  80         return 0;
  81 }
  82
  83 static int secmark_tg_check(const struct xt_tgchk_param *par)
  84 {
  85         struct xt_secmark_target_info *info = par->targinfo;
  86         int err;
  87
  88         if (strcmp(par->table, "mangle") != 0 &&
  89             strcmp(par->table, "security") != 0) {
  90                 pr_info("target only valid in the \'mangle\' "
  91                         "or \'security\' tables, not \'%s\'.\n", par->table);
  92                 return -EINVAL;
  93         }
  94
  95         if (mode && mode != info->mode) {
  96                 pr_info("mode already set to %hu cannot mix with "
  97                         "rules for mode %hu\n", mode, info->mode);
  98                 return -EINVAL;
  99         }
 100
 101         switch (info->mode) {
 102         case SECMARK_MODE_SEL:
 103                 err = checkentry_selinux(info);
 104                 if (err <= 0)
 105                         return err;
 106                 break;
 107
 108         default:
 109                 pr_info("invalid mode: %hu\n", info->mode);
 110                 return -EINVAL;
 111         }
 112
 113         if (!mode)
 114                 mode = info->mode;
 115         return 0;
 116 }
 117
 118 static void secmark_tg_destroy(const struct xt_tgdtor_param *par)
 119 {
 120         switch (mode) {
 121         case SECMARK_MODE_SEL:
 122                 selinux_secmark_refcount_dec();
 123         }
 124 }
 125
 126 static struct xt_target secmark_tg_reg __read_mostly = {
 127         .name       = "SECMARK",
 128         .revision   = 0,
 129         .family     = NFPROTO_UNSPEC,
 130         .checkentry = secmark_tg_check,
 131         .destroy    = secmark_tg_destroy,
 132         .target     = secmark_tg,
 133         .targetsize = sizeof(struct xt_secmark_target_info),
 134         .me         = THIS_MODULE,
 135 };
 136
 137 static int __init secmark_tg_init(void)
 138 {
 139         return xt_register_target(&secmark_tg_reg);
 140 }
 141
 142 static void __exit secmark_tg_exit(void)
 143 {
 144         xt_unregister_target(&secmark_tg_reg);
 145 }
 146
 147 module_init(secmark_tg_init);
 148 module_exit(secmark_tg_exit);