net/netfilter/nf_conntrack_tftp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 2001-2002 Magnus Boden <[email protected]>
   3  * (C) 2006-2012 Patrick McHardy <[email protected]>
   4  */
   5
   6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   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 #define HELPER_NAME "tftp"
  22
  23 MODULE_AUTHOR("Magnus Boden <[email protected]>");
  24 MODULE_DESCRIPTION("TFTP connection tracking helper");
  25 MODULE_LICENSE("GPL");
  26 MODULE_ALIAS("ip_conntrack_tftp");
  27 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
  28
  29 #define MAX_PORTS 8
  30 static unsigned short ports[MAX_PORTS];
  31 static unsigned int ports_c;
  32 module_param_array(ports, ushort, &ports_c, 0400);
  33 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
  34
  35 unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
  36                                  enum ip_conntrack_info ctinfo,
  37                                  struct nf_conntrack_expect *exp) __read_mostly;
  38 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
  39
  40 static int tftp_help(struct sk_buff *skb,
  41                      unsigned int protoff,
  42                      struct nf_conn *ct,
  43                      enum ip_conntrack_info ctinfo)
  44 {
  45         const struct tftphdr *tfh;
  46         struct tftphdr _tftph;
  47         struct nf_conntrack_expect *exp;
  48         struct nf_conntrack_tuple *tuple;
  49         unsigned int ret = NF_ACCEPT;
  50         typeof(nf_nat_tftp_hook) nf_nat_tftp;
  51
  52         tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
  53                                  sizeof(_tftph), &_tftph);
  54         if (tfh == NULL)
  55                 return NF_ACCEPT;
  56
  57         switch (ntohs(tfh->opcode)) {
  58         case TFTP_OPCODE_READ:
  59         case TFTP_OPCODE_WRITE:
  60                 /* RRQ and WRQ works the same way */
  61                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  62                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  63
  64                 exp = nf_ct_expect_alloc(ct);
  65                 if (exp == NULL) {
  66                         nf_ct_helper_log(skb, ct, "cannot alloc expectation");
  67                         return NF_DROP;
  68                 }
  69                 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  70                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
  71                                   nf_ct_l3num(ct),
  72                                   &tuple->src.u3, &tuple->dst.u3,
  73                                   IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
  74
  75                 pr_debug("expect: ");
  76                 nf_ct_dump_tuple(&exp->tuple);
  77
  78                 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  79                 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  80                         ret = nf_nat_tftp(skb, ctinfo, exp);
  81                 else if (nf_ct_expect_related(exp, 0) != 0) {
  82                         nf_ct_helper_log(skb, ct, "cannot add expectation");
  83                         ret = NF_DROP;
  84                 }
  85                 nf_ct_expect_put(exp);
  86                 break;
  87         case TFTP_OPCODE_DATA:
  88         case TFTP_OPCODE_ACK:
  89                 pr_debug("Data/ACK opcode\n");
  90                 break;
  91         case TFTP_OPCODE_ERROR:
  92                 pr_debug("Error opcode\n");
  93                 break;
  94         default:
  95                 pr_debug("Unknown opcode\n");
  96         }
  97         return ret;
  98 }
  99
 100 static struct nf_conntrack_helper tftp[MAX_PORTS * 2] __read_mostly;
 101
 102 static const struct nf_conntrack_expect_policy tftp_exp_policy = {
 103         .max_expected   = 1,
 104         .timeout        = 5 * 60,
 105 };
 106
 107 static void __exit nf_conntrack_tftp_fini(void)
 108 {
 109         nf_conntrack_helpers_unregister(tftp, ports_c * 2);
 110 }
 111
 112 static int __init nf_conntrack_tftp_init(void)
 113 {
 114         int i, ret;
 115
 116         NF_CT_HELPER_BUILD_BUG_ON(0);
 117
 118         if (ports_c == 0)
 119                 ports[ports_c++] = TFTP_PORT;
 120
 121         for (i = 0; i < ports_c; i++) {
 122                 nf_ct_helper_init(&tftp[2 * i], AF_INET, IPPROTO_UDP,
 123                                   HELPER_NAME, TFTP_PORT, ports[i], i,
 124                                   &tftp_exp_policy, 0, tftp_help, NULL,
 125                                   THIS_MODULE);
 126                 nf_ct_helper_init(&tftp[2 * i + 1], AF_INET6, IPPROTO_UDP,
 127                                   HELPER_NAME, TFTP_PORT, ports[i], i,
 128                                   &tftp_exp_policy, 0, tftp_help, NULL,
 129                                   THIS_MODULE);
 130         }
 131
 132         ret = nf_conntrack_helpers_register(tftp, ports_c * 2);
 133         if (ret < 0) {
 134                 pr_err("failed to register helpers\n");
 135                 return ret;
 136         }
 137         return 0;
 138 }
 139
 140 module_init(nf_conntrack_tftp_init);
 141 module_exit(nf_conntrack_tftp_fini);