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