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/security.h>
  18 #include <linux/skbuff.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->secid;
  43                 break;
  44         default:
  45                 BUG();
  46         }
  47
  48         skb->secmark = secmark;
  49         return XT_CONTINUE;
  50 }
  51
  52 static int checkentry_lsm(struct xt_secmark_target_info *info)
  53 {
  54         int err;
  55
  56         info->secctx[SECMARK_SECCTX_MAX - 1] = '\0';
  57         info->secid = 0;
  58
  59         err = security_secctx_to_secid(info->secctx, strlen(info->secctx),
  60                                        &info->secid);
  61         if (err) {
  62                 if (err == -EINVAL)
  63                         pr_info_ratelimited("invalid security context \'%s\'\n",
  64                                             info->secctx);
  65                 return err;
  66         }
  67
  68         if (!info->secid) {
  69                 pr_info_ratelimited("unable to map security context \'%s\'\n",
  70                                     info->secctx);
  71                 return -ENOENT;
  72         }
  73
  74         err = security_secmark_relabel_packet(info->secid);
  75         if (err) {
  76                 pr_info_ratelimited("unable to obtain relabeling permission\n");
  77                 return err;
  78         }
  79
  80         security_secmark_refcount_inc();
  81         return 0;
  82 }
  83
  84 static int secmark_tg_check(const struct xt_tgchk_param *par)
  85 {
  86         struct xt_secmark_target_info *info = par->targinfo;
  87         int err;
  88
  89         if (strcmp(par->table, "mangle") != 0 &&
  90             strcmp(par->table, "security") != 0) {
  91                 pr_info_ratelimited("only valid in \'mangle\' or \'security\' table, not \'%s\'\n",
  92                                     par->table);
  93                 return -EINVAL;
  94         }
  95
  96         if (mode && mode != info->mode) {
  97                 pr_info_ratelimited("mode already set to %hu cannot mix with rules for mode %hu\n",
  98                                     mode, info->mode);
  99                 return -EINVAL;
 100         }
 101
 102         switch (info->mode) {
 103         case SECMARK_MODE_SEL:
 104                 break;
 105         default:
 106                 pr_info_ratelimited("invalid mode: %hu\n", info->mode);
 107                 return -EINVAL;
 108         }
 109
 110         err = checkentry_lsm(info);
 111         if (err)
 112                 return err;
 113
 114         if (!mode)
 115                 mode = info->mode;
 116         return 0;
 117 }
 118
 119 static void secmark_tg_destroy(const struct xt_tgdtor_param *par)
 120 {
 121         switch (mode) {
 122         case SECMARK_MODE_SEL:
 123                 security_secmark_refcount_dec();
 124         }
 125 }
 126
 127 static struct xt_target secmark_tg_reg __read_mostly = {
 128         .name       = "SECMARK",
 129         .revision   = 0,
 130         .family     = NFPROTO_UNSPEC,
 131         .checkentry = secmark_tg_check,
 132         .destroy    = secmark_tg_destroy,
 133         .target     = secmark_tg,
 134         .targetsize = sizeof(struct xt_secmark_target_info),
 135         .me         = THIS_MODULE,
 136 };
 137
 138 static int __init secmark_tg_init(void)
 139 {
 140         return xt_register_target(&secmark_tg_reg);
 141 }
 142
 143 static void __exit secmark_tg_exit(void)
 144 {
 145         xt_unregister_target(&secmark_tg_reg);
 146 }
 147
 148 module_init(secmark_tg_init);
 149 module_exit(secmark_tg_exit);