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 #include <linux/module.h>
   9 #include <linux/moduleparam.h>
  10 #include <linux/in.h>
  11 #include <linux/udp.h>
  12 #include <linux/netfilter.h>
  13
  14 #include <net/netfilter/nf_conntrack.h>
  15 #include <net/netfilter/nf_conntrack_tuple.h>
  16 #include <net/netfilter/nf_conntrack_expect.h>
  17 #include <net/netfilter/nf_conntrack_ecache.h>
  18 #include <net/netfilter/nf_conntrack_helper.h>
  19 #include <linux/netfilter/nf_conntrack_tftp.h>
  20
  21 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  22 MODULE_DESCRIPTION("TFTP connection tracking helper");
  23 MODULE_LICENSE("GPL");
  24 MODULE_ALIAS("ip_conntrack_tftp");
  25 MODULE_ALIAS_NFCT_HELPER("tftp");
  26
  27 #define MAX_PORTS 8
  28 static unsigned short ports[MAX_PORTS];
  29 static unsigned int ports_c;
  30 module_param_array(ports, ushort, &ports_c, 0400);
  31 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
  32
  33 unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
  34                                  enum ip_conntrack_info ctinfo,
  35                                  struct nf_conntrack_expect *exp) __read_mostly;
  36 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
  37
  38 static int tftp_help(struct sk_buff *skb,
  39                      unsigned int protoff,
  40                      struct nf_conn *ct,
  41                      enum ip_conntrack_info ctinfo)
  42 {
  43         const struct tftphdr *tfh;
  44         struct tftphdr _tftph;
  45         struct nf_conntrack_expect *exp;
  46         struct nf_conntrack_tuple *tuple;
  47         unsigned int ret = NF_ACCEPT;
  48         typeof(nf_nat_tftp_hook) nf_nat_tftp;
  49
  50         tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
  51                                  sizeof(_tftph), &_tftph);
  52         if (tfh == NULL)
  53                 return NF_ACCEPT;
  54
  55         switch (ntohs(tfh->opcode)) {
  56         case TFTP_OPCODE_READ:
  57         case TFTP_OPCODE_WRITE:
  58                 /* RRQ and WRQ works the same way */
  59                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  60                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  61
  62                 exp = nf_ct_expect_alloc(ct);
  63                 if (exp == NULL) {
  64                         nf_ct_helper_log(skb, ct, "cannot alloc expectation");
  65                         return NF_DROP;
  66                 }
  67                 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  68                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
  69                                   nf_ct_l3num(ct),
  70                                   &tuple->src.u3, &tuple->dst.u3,
  71                                   IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
  72
  73                 pr_debug("expect: ");
  74                 nf_ct_dump_tuple(&exp->tuple);
  75
  76                 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  77                 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  78                         ret = nf_nat_tftp(skb, ctinfo, exp);
  79                 else if (nf_ct_expect_related(exp) != 0) {
  80                         nf_ct_helper_log(skb, ct, "cannot add expectation");
  81                         ret = NF_DROP;
  82                 }
  83                 nf_ct_expect_put(exp);
  84                 break;
  85         case TFTP_OPCODE_DATA:
  86         case TFTP_OPCODE_ACK:
  87                 pr_debug("Data/ACK opcode\n");
  88                 break;
  89         case TFTP_OPCODE_ERROR:
  90                 pr_debug("Error opcode\n");
  91                 break;
  92         default:
  93                 pr_debug("Unknown opcode\n");
  94         }
  95         return ret;
  96 }
  97
  98 static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
  99
 100 static const struct nf_conntrack_expect_policy tftp_exp_policy = {
 101         .max_expected   = 1,
 102         .timeout        = 5 * 60,
 103 };
 104
 105 static void nf_conntrack_tftp_fini(void)
 106 {
 107         int i, j;
 108
 109         for (i = 0; i < ports_c; i++) {
 110                 for (j = 0; j < 2; j++)
 111                         nf_conntrack_helper_unregister(&tftp[i][j]);
 112         }
 113 }
 114
 115 static int __init nf_conntrack_tftp_init(void)
 116 {
 117         int i, j, ret;
 118
 119         if (ports_c == 0)
 120                 ports[ports_c++] = TFTP_PORT;
 121
 122         for (i = 0; i < ports_c; i++) {
 123                 memset(&tftp[i], 0, sizeof(tftp[i]));
 124
 125                 tftp[i][0].tuple.src.l3num = AF_INET;
 126                 tftp[i][1].tuple.src.l3num = AF_INET6;
 127                 for (j = 0; j < 2; j++) {
 128                         tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
 129                         tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
 130                         tftp[i][j].expect_policy = &tftp_exp_policy;
 131                         tftp[i][j].me = THIS_MODULE;
 132                         tftp[i][j].help = tftp_help;
 133
 134                         if (ports[i] == TFTP_PORT)
 135                                 sprintf(tftp[i][j].name, "tftp");
 136                         else
 137                                 sprintf(tftp[i][j].name, "tftp-%u", i);
 138
 139                         ret = nf_conntrack_helper_register(&tftp[i][j]);
 140                         if (ret) {
 141                                 printk(KERN_ERR "nf_ct_tftp: failed to register"
 142                                        " helper for pf: %u port: %u\n",
 143                                         tftp[i][j].tuple.src.l3num, ports[i]);
 144                                 nf_conntrack_tftp_fini();
 145                                 return ret;
 146                         }
 147                 }
 148         }
 149         return 0;
 150 }
 151
 152 module_init(nf_conntrack_tftp_init);
 153 module_exit(nf_conntrack_tftp_fini);