net/netfilter/nf_conntrack_tftp.c

   1 /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
   2  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License version 2 as
   5  * published by the Free Software Foundation.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/module.h>
  11 #include <linux/moduleparam.h>
  12 #include <linux/in.h>
  13 #include <linux/udp.h>
  14 #include <linux/netfilter.h>
  15
  16 #include <net/netfilter/nf_conntrack.h>
  17 #include <net/netfilter/nf_conntrack_tuple.h>
  18 #include <net/netfilter/nf_conntrack_expect.h>
  19 #include <net/netfilter/nf_conntrack_ecache.h>
  20 #include <net/netfilter/nf_conntrack_helper.h>
  21 #include <linux/netfilter/nf_conntrack_tftp.h>
  22
  23 #define HELPER_NAME "tftp"
  24
  25 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  26 MODULE_DESCRIPTION("TFTP connection tracking helper");
  27 MODULE_LICENSE("GPL");
  28 MODULE_ALIAS("ip_conntrack_tftp");
  29 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
  30
  31 #define MAX_PORTS 8
  32 static unsigned short ports[MAX_PORTS];
  33 static unsigned int ports_c;
  34 module_param_array(ports, ushort, &ports_c, 0400);
  35 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
  36
  37 unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
  38                                  enum ip_conntrack_info ctinfo,
  39                                  struct nf_conntrack_expect *exp) __read_mostly;
  40 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
  41
  42 static int tftp_help(struct sk_buff *skb,
  43                      unsigned int protoff,
  44                      struct nf_conn *ct,
  45                      enum ip_conntrack_info ctinfo)
  46 {
  47         const struct tftphdr *tfh;
  48         struct tftphdr _tftph;
  49         struct nf_conntrack_expect *exp;
  50         struct nf_conntrack_tuple *tuple;
  51         unsigned int ret = NF_ACCEPT;
  52         typeof(nf_nat_tftp_hook) nf_nat_tftp;
  53
  54         tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
  55                                  sizeof(_tftph), &_tftph);
  56         if (tfh == NULL)
  57                 return NF_ACCEPT;
  58
  59         switch (ntohs(tfh->opcode)) {
  60         case TFTP_OPCODE_READ:
  61         case TFTP_OPCODE_WRITE:
  62                 /* RRQ and WRQ works the same way */
  63                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  64                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  65
  66                 exp = nf_ct_expect_alloc(ct);
  67                 if (exp == NULL) {
  68                         nf_ct_helper_log(skb, ct, "cannot alloc expectation");
  69                         return NF_DROP;
  70                 }
  71                 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  72                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
  73                                   nf_ct_l3num(ct),
  74                                   &tuple->src.u3, &tuple->dst.u3,
  75                                   IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
  76
  77                 pr_debug("expect: ");
  78                 nf_ct_dump_tuple(&exp->tuple);
  79
  80                 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  81                 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  82                         ret = nf_nat_tftp(skb, ctinfo, exp);
  83                 else if (nf_ct_expect_related(exp) != 0) {
  84                         nf_ct_helper_log(skb, ct, "cannot add expectation");
  85                         ret = NF_DROP;
  86                 }
  87                 nf_ct_expect_put(exp);
  88                 break;
  89         case TFTP_OPCODE_DATA:
  90         case TFTP_OPCODE_ACK:
  91                 pr_debug("Data/ACK opcode\n");
  92                 break;
  93         case TFTP_OPCODE_ERROR:
  94                 pr_debug("Error opcode\n");
  95                 break;
  96         default:
  97                 pr_debug("Unknown opcode\n");
  98         }
  99         return ret;
 100 }
 101
 102 static struct nf_conntrack_helper tftp[MAX_PORTS * 2] __read_mostly;
 103
 104 static const struct nf_conntrack_expect_policy tftp_exp_policy = {
 105         .max_expected   = 1,
 106         .timeout        = 5 * 60,
 107 };
 108
 109 static void __exit nf_conntrack_tftp_fini(void)
 110 {
 111         nf_conntrack_helpers_unregister(tftp, ports_c * 2);
 112 }
 113
 114 static int __init nf_conntrack_tftp_init(void)
 115 {
 116         int i, ret;
 117
 118         NF_CT_HELPER_BUILD_BUG_ON(0);
 119
 120         if (ports_c == 0)
 121                 ports[ports_c++] = TFTP_PORT;
 122
 123         for (i = 0; i < ports_c; i++) {
 124                 nf_ct_helper_init(&tftp[2 * i], AF_INET, IPPROTO_UDP,
 125                                   HELPER_NAME, TFTP_PORT, ports[i], i,
 126                                   &tftp_exp_policy, 0, tftp_help, NULL,
 127                                   THIS_MODULE);
 128                 nf_ct_helper_init(&tftp[2 * i + 1], AF_INET6, IPPROTO_UDP,
 129                                   HELPER_NAME, TFTP_PORT, ports[i], i,
 130                                   &tftp_exp_policy, 0, tftp_help, NULL,
 131                                   THIS_MODULE);
 132         }
 133
 134         ret = nf_conntrack_helpers_register(tftp, ports_c * 2);
 135         if (ret < 0) {
 136                 pr_err("failed to register helpers\n");
 137                 return ret;
 138         }
 139         return 0;
 140 }
 141
 142 module_init(nf_conntrack_tftp_init);
 143 module_exit(nf_conntrack_tftp_fini);