net/netfilter/nf_conntrack_proto_udp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   5  */
   6
   7 #include <linux/types.h>
   8 #include <linux/timer.h>
   9 #include <linux/module.h>
  10 #include <linux/udp.h>
  11 #include <linux/seq_file.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/ipv6.h>
  14 #include <net/ip6_checksum.h>
  15 #include <net/checksum.h>
  16
  17 #include <linux/netfilter.h>
  18 #include <linux/netfilter_ipv4.h>
  19 #include <linux/netfilter_ipv6.h>
  20 #include <net/netfilter/nf_conntrack_l4proto.h>
  21 #include <net/netfilter/nf_conntrack_ecache.h>
  22 #include <net/netfilter/nf_conntrack_timeout.h>
  23 #include <net/netfilter/nf_log.h>
  24 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  25 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  26
  27 static const unsigned int udp_timeouts[UDP_CT_MAX] = {
  28         [UDP_CT_UNREPLIED]      = 30*HZ,
  29         [UDP_CT_REPLIED]        = 120*HZ,
  30 };
  31
  32 static unsigned int *udp_get_timeouts(struct net *net)
  33 {
  34         return nf_udp_pernet(net)->timeouts;
  35 }
  36
  37 static void udp_error_log(const struct sk_buff *skb,
  38                           const struct nf_hook_state *state,
  39                           const char *msg)
  40 {
  41         nf_l4proto_log_invalid(skb, state->net, state->pf,
  42                                IPPROTO_UDP, "%s", msg);
  43 }
  44
  45 static bool udp_error(struct sk_buff *skb,
  46                       unsigned int dataoff,
  47                       const struct nf_hook_state *state)
  48 {
  49         unsigned int udplen = skb->len - dataoff;
  50         const struct udphdr *hdr;
  51         struct udphdr _hdr;
  52
  53         /* Header is too small? */
  54         hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  55         if (!hdr) {
  56                 udp_error_log(skb, state, "short packet");
  57                 return true;
  58         }
  59
  60         /* Truncated/malformed packets */
  61         if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
  62                 udp_error_log(skb, state, "truncated/malformed packet");
  63                 return true;
  64         }
  65
  66         /* Packet with no checksum */
  67         if (!hdr->check)
  68                 return false;
  69
  70         /* Checksum invalid? Ignore.
  71          * We skip checking packets on the outgoing path
  72          * because the checksum is assumed to be correct.
  73          * FIXME: Source route IP option packets --RR */
  74         if (state->hook == NF_INET_PRE_ROUTING &&
  75             state->net->ct.sysctl_checksum &&
  76             nf_checksum(skb, state->hook, dataoff, IPPROTO_UDP, state->pf)) {
  77                 udp_error_log(skb, state, "bad checksum");
  78                 return true;
  79         }
  80
  81         return false;
  82 }
  83
  84 /* Returns verdict for packet, and may modify conntracktype */
  85 int nf_conntrack_udp_packet(struct nf_conn *ct,
  86                             struct sk_buff *skb,
  87                             unsigned int dataoff,
  88                             enum ip_conntrack_info ctinfo,
  89                             const struct nf_hook_state *state)
  90 {
  91         unsigned int *timeouts;
  92
  93         if (udp_error(skb, dataoff, state))
  94                 return -NF_ACCEPT;
  95
  96         timeouts = nf_ct_timeout_lookup(ct);
  97         if (!timeouts)
  98                 timeouts = udp_get_timeouts(nf_ct_net(ct));
  99
 100         if (!nf_ct_is_confirmed(ct))
 101                 ct->proto.udp.stream_ts = 2 * HZ + jiffies;
 102
 103         /* If we've seen traffic both ways, this is some kind of UDP
 104          * stream. Set Assured.
 105          */
 106         if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
 107                 unsigned long extra = timeouts[UDP_CT_UNREPLIED];
 108                 bool stream = false;
 109
 110                 /* Still active after two seconds? Extend timeout. */
 111                 if (time_after(jiffies, ct->proto.udp.stream_ts)) {
 112                         extra = timeouts[UDP_CT_REPLIED];
 113                         stream = true;
 114                 }
 115
 116                 nf_ct_refresh_acct(ct, ctinfo, skb, extra);
 117
 118                 /* never set ASSURED for IPS_NAT_CLASH, they time out soon */
 119                 if (unlikely((ct->status & IPS_NAT_CLASH)))
 120                         return NF_ACCEPT;
 121
 122                 /* Also, more likely to be important, and not a probe */
 123                 if (stream && !test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 124                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 125         } else {
 126                 nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 127         }
 128         return NF_ACCEPT;
 129 }
 130
 131 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
 132 static void udplite_error_log(const struct sk_buff *skb,
 133                               const struct nf_hook_state *state,
 134                               const char *msg)
 135 {
 136         nf_l4proto_log_invalid(skb, state->net, state->pf,
 137                                IPPROTO_UDPLITE, "%s", msg);
 138 }
 139
 140 static bool udplite_error(struct sk_buff *skb,
 141                           unsigned int dataoff,
 142                           const struct nf_hook_state *state)
 143 {
 144         unsigned int udplen = skb->len - dataoff;
 145         const struct udphdr *hdr;
 146         struct udphdr _hdr;
 147         unsigned int cscov;
 148
 149         /* Header is too small? */
 150         hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
 151         if (!hdr) {
 152                 udplite_error_log(skb, state, "short packet");
 153                 return true;
 154         }
 155
 156         cscov = ntohs(hdr->len);
 157         if (cscov == 0) {
 158                 cscov = udplen;
 159         } else if (cscov < sizeof(*hdr) || cscov > udplen) {
 160                 udplite_error_log(skb, state, "invalid checksum coverage");
 161                 return true;
 162         }
 163
 164         /* UDPLITE mandates checksums */
 165         if (!hdr->check) {
 166                 udplite_error_log(skb, state, "checksum missing");
 167                 return true;
 168         }
 169
 170         /* Checksum invalid? Ignore. */
 171         if (state->hook == NF_INET_PRE_ROUTING &&
 172             state->net->ct.sysctl_checksum &&
 173             nf_checksum_partial(skb, state->hook, dataoff, cscov, IPPROTO_UDP,
 174                                 state->pf)) {
 175                 udplite_error_log(skb, state, "bad checksum");
 176                 return true;
 177         }
 178
 179         return false;
 180 }
 181
 182 /* Returns verdict for packet, and may modify conntracktype */
 183 int nf_conntrack_udplite_packet(struct nf_conn *ct,
 184                                 struct sk_buff *skb,
 185                                 unsigned int dataoff,
 186                                 enum ip_conntrack_info ctinfo,
 187                                 const struct nf_hook_state *state)
 188 {
 189         unsigned int *timeouts;
 190
 191         if (udplite_error(skb, dataoff, state))
 192                 return -NF_ACCEPT;
 193
 194         timeouts = nf_ct_timeout_lookup(ct);
 195         if (!timeouts)
 196                 timeouts = udp_get_timeouts(nf_ct_net(ct));
 197
 198         /* If we've seen traffic both ways, this is some kind of UDP
 199            stream.  Extend timeout. */
 200         if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
 201                 nf_ct_refresh_acct(ct, ctinfo, skb,
 202                                    timeouts[UDP_CT_REPLIED]);
 203
 204                 if (unlikely((ct->status & IPS_NAT_CLASH)))
 205                         return NF_ACCEPT;
 206
 207                 /* Also, more likely to be important, and not a probe */
 208                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 209                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 210         } else {
 211                 nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 212         }
 213         return NF_ACCEPT;
 214 }
 215 #endif
 216
 217 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 218
 219 #include <linux/netfilter/nfnetlink.h>
 220 #include <linux/netfilter/nfnetlink_cttimeout.h>
 221
 222 static int udp_timeout_nlattr_to_obj(struct nlattr *tb[],
 223                                      struct net *net, void *data)
 224 {
 225         unsigned int *timeouts = data;
 226         struct nf_udp_net *un = nf_udp_pernet(net);
 227
 228         if (!timeouts)
 229                 timeouts = un->timeouts;
 230
 231         /* set default timeouts for UDP. */
 232         timeouts[UDP_CT_UNREPLIED] = un->timeouts[UDP_CT_UNREPLIED];
 233         timeouts[UDP_CT_REPLIED] = un->timeouts[UDP_CT_REPLIED];
 234
 235         if (tb[CTA_TIMEOUT_UDP_UNREPLIED]) {
 236                 timeouts[UDP_CT_UNREPLIED] =
 237                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_UNREPLIED])) * HZ;
 238         }
 239         if (tb[CTA_TIMEOUT_UDP_REPLIED]) {
 240                 timeouts[UDP_CT_REPLIED] =
 241                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_REPLIED])) * HZ;
 242         }
 243         return 0;
 244 }
 245
 246 static int
 247 udp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 248 {
 249         const unsigned int *timeouts = data;
 250
 251         if (nla_put_be32(skb, CTA_TIMEOUT_UDP_UNREPLIED,
 252                          htonl(timeouts[UDP_CT_UNREPLIED] / HZ)) ||
 253             nla_put_be32(skb, CTA_TIMEOUT_UDP_REPLIED,
 254                          htonl(timeouts[UDP_CT_REPLIED] / HZ)))
 255                 goto nla_put_failure;
 256         return 0;
 257
 258 nla_put_failure:
 259         return -ENOSPC;
 260 }
 261
 262 static const struct nla_policy
 263 udp_timeout_nla_policy[CTA_TIMEOUT_UDP_MAX+1] = {
 264        [CTA_TIMEOUT_UDP_UNREPLIED]      = { .type = NLA_U32 },
 265        [CTA_TIMEOUT_UDP_REPLIED]        = { .type = NLA_U32 },
 266 };
 267 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 268
 269 void nf_conntrack_udp_init_net(struct net *net)
 270 {
 271         struct nf_udp_net *un = nf_udp_pernet(net);
 272         int i;
 273
 274         for (i = 0; i < UDP_CT_MAX; i++)
 275                 un->timeouts[i] = udp_timeouts[i];
 276 }
 277
 278 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udp =
 279 {
 280         .l4proto                = IPPROTO_UDP,
 281         .allow_clash            = true,
 282 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 283         .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
 284         .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
 285         .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
 286         .nla_policy             = nf_ct_port_nla_policy,
 287 #endif
 288 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 289         .ctnl_timeout           = {
 290                 .nlattr_to_obj  = udp_timeout_nlattr_to_obj,
 291                 .obj_to_nlattr  = udp_timeout_obj_to_nlattr,
 292                 .nlattr_max     = CTA_TIMEOUT_UDP_MAX,
 293                 .obj_size       = sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
 294                 .nla_policy     = udp_timeout_nla_policy,
 295         },
 296 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 297 };
 298
 299 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
 300 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udplite =
 301 {
 302         .l4proto                = IPPROTO_UDPLITE,
 303         .allow_clash            = true,
 304 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 305         .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
 306         .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
 307         .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
 308         .nla_policy             = nf_ct_port_nla_policy,
 309 #endif
 310 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 311         .ctnl_timeout           = {
 312                 .nlattr_to_obj  = udp_timeout_nlattr_to_obj,
 313                 .obj_to_nlattr  = udp_timeout_obj_to_nlattr,
 314                 .nlattr_max     = CTA_TIMEOUT_UDP_MAX,
 315                 .obj_size       = sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
 316                 .nla_policy     = udp_timeout_nla_policy,
 317         },
 318 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 319 };
 320 #endif