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