err.no Git - linux-2.6/blob - net/ipv4/netfilter/nf_nat_sip.c

   1 /* SIP extension for UDP NAT alteration.
   2  *
   3  * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
   4  * based on RR's ip_nat_ftp.c and other modules.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/ip.h>
  14 #include <net/ip.h>
  15 #include <linux/udp.h>
  16
  17 #include <net/netfilter/nf_nat.h>
  18 #include <net/netfilter/nf_nat_helper.h>
  19 #include <net/netfilter/nf_nat_rule.h>
  20 #include <net/netfilter/nf_conntrack_helper.h>
  21 #include <net/netfilter/nf_conntrack_expect.h>
  22 #include <linux/netfilter/nf_conntrack_sip.h>
  23
  24 MODULE_LICENSE("GPL");
  25 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
  26 MODULE_DESCRIPTION("SIP NAT helper");
  27 MODULE_ALIAS("ip_nat_sip");
  28
  29 struct addr_map {
  30         struct {
  31                 char            src[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
  32                 char            dst[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
  33                 unsigned int    srclen, srciplen;
  34                 unsigned int    dstlen, dstiplen;
  35         } addr[IP_CT_DIR_MAX];
  36 };
  37
  38 static void addr_map_init(const struct nf_conn *ct, struct addr_map *map)
  39 {
  40         const struct nf_conntrack_tuple *t;
  41         enum ip_conntrack_dir dir;
  42         unsigned int n;
  43
  44         for (dir = 0; dir < IP_CT_DIR_MAX; dir++) {
  45                 t = &ct->tuplehash[dir].tuple;
  46
  47                 n = sprintf(map->addr[dir].src, "%u.%u.%u.%u",
  48                             NIPQUAD(t->src.u3.ip));
  49                 map->addr[dir].srciplen = n;
  50                 n += sprintf(map->addr[dir].src + n, ":%u",
  51                              ntohs(t->src.u.udp.port));
  52                 map->addr[dir].srclen = n;
  53
  54                 n = sprintf(map->addr[dir].dst, "%u.%u.%u.%u",
  55                             NIPQUAD(t->dst.u3.ip));
  56                 map->addr[dir].dstiplen = n;
  57                 n += sprintf(map->addr[dir].dst + n, ":%u",
  58                              ntohs(t->dst.u.udp.port));
  59                 map->addr[dir].dstlen = n;
  60         }
  61 }
  62
  63 static unsigned int mangle_packet(struct sk_buff *skb,
  64                                   const char **dptr, unsigned int *datalen,
  65                                   unsigned int matchoff, unsigned int matchlen,
  66                                   const char *buffer, unsigned int buflen)
  67 {
  68         enum ip_conntrack_info ctinfo;
  69         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  70
  71         if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, matchoff, matchlen,
  72                                       buffer, buflen))
  73                 return 0;
  74
  75         /* Reload data pointer and adjust datalen value */
  76         *dptr = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
  77         *datalen += buflen - matchlen;
  78         return 1;
  79 }
  80
  81 static int map_sip_addr(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
  82                         struct nf_conn *ct,
  83                         const char **dptr, unsigned int *datalen,
  84                         enum sip_header_pos pos, struct addr_map *map)
  85 {
  86         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
  87         unsigned int matchlen, matchoff, addrlen;
  88         char *addr;
  89
  90         if (ct_sip_get_info(ct, *dptr, *datalen, &matchoff, &matchlen,
  91                             pos) <= 0)
  92                 return 1;
  93
  94         if ((matchlen == map->addr[dir].srciplen ||
  95              matchlen == map->addr[dir].srclen) &&
  96             memcmp(*dptr + matchoff, map->addr[dir].src, matchlen) == 0) {
  97                 addr    = map->addr[!dir].dst;
  98                 addrlen = map->addr[!dir].dstlen;
  99         } else if ((matchlen == map->addr[dir].dstiplen ||
 100                     matchlen == map->addr[dir].dstlen) &&
 101                    memcmp(*dptr + matchoff, map->addr[dir].dst, matchlen) == 0) {
 102                 addr    = map->addr[!dir].src;
 103                 addrlen = map->addr[!dir].srclen;
 104         } else
 105                 return 1;
 106
 107         return mangle_packet(skb, dptr, datalen, matchoff, matchlen,
 108                              addr, addrlen);
 109 }
 110
 111 static unsigned int ip_nat_sip(struct sk_buff *skb,
 112                                enum ip_conntrack_info ctinfo,
 113                                struct nf_conn *ct,
 114                                const char **dptr, unsigned int *datalen)
 115 {
 116         enum sip_header_pos pos;
 117         struct addr_map map;
 118
 119         if (*datalen < sizeof("SIP/2.0") - 1)
 120                 return NF_ACCEPT;
 121
 122         addr_map_init(ct, &map);
 123
 124         /* Basic rules: requests and responses. */
 125         if (strncmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) != 0) {
 126                 /* 10.2: Constructing the REGISTER Request:
 127                  *
 128                  * The "userinfo" and "@" components of the SIP URI MUST NOT
 129                  * be present.
 130                  */
 131                 if (*datalen >= sizeof("REGISTER") - 1 &&
 132                     strncmp(*dptr, "REGISTER", sizeof("REGISTER") - 1) == 0)
 133                         pos = POS_REG_REQ_URI;
 134                 else
 135                         pos = POS_REQ_URI;
 136
 137                 if (!map_sip_addr(skb, ctinfo, ct, dptr, datalen, pos, &map))
 138                         return NF_DROP;
 139         }
 140
 141         if (!map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_FROM, &map) ||
 142             !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_TO, &map) ||
 143             !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_VIA, &map) ||
 144             !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_CONTACT, &map))
 145                 return NF_DROP;
 146         return NF_ACCEPT;
 147 }
 148
 149 static unsigned int mangle_sip_packet(struct sk_buff *skb,
 150                                       enum ip_conntrack_info ctinfo,
 151                                       struct nf_conn *ct,
 152                                       const char **dptr, unsigned int *datalen,
 153                                       char *buffer, int bufflen,
 154                                       enum sip_header_pos pos)
 155 {
 156         unsigned int matchlen, matchoff;
 157
 158         if (ct_sip_get_info(ct, *dptr, *datalen, &matchoff, &matchlen,
 159                             pos) <= 0)
 160                 return 0;
 161
 162         return mangle_packet(skb, dptr, datalen, matchoff, matchlen,
 163                              buffer, bufflen);
 164 }
 165
 166 static int mangle_content_len(struct sk_buff *skb,
 167                               enum ip_conntrack_info ctinfo,
 168                               struct nf_conn *ct,
 169                               const char **dptr, unsigned int *datalen)
 170 {
 171         unsigned int matchoff, matchlen;
 172         char buffer[sizeof("65536")];
 173         int bufflen;
 174
 175         /* Get actual SDP length */
 176         if (ct_sip_get_info(ct, *dptr, *datalen, &matchoff,
 177                             &matchlen, POS_SDP_HEADER) > 0) {
 178
 179                 /* since ct_sip_get_info() give us a pointer passing 'v='
 180                    we need to add 2 bytes in this count. */
 181                 int c_len = *datalen - matchoff + 2;
 182
 183                 /* Now, update SDP length */
 184                 if (ct_sip_get_info(ct, *dptr, *datalen, &matchoff,
 185                                     &matchlen, POS_CONTENT) > 0) {
 186
 187                         bufflen = sprintf(buffer, "%u", c_len);
 188                         return mangle_packet(skb, dptr, datalen,
 189                                              matchoff, matchlen,
 190                                              buffer, bufflen);
 191                 }
 192         }
 193         return 0;
 194 }
 195
 196 static unsigned int mangle_sdp(struct sk_buff *skb,
 197                                enum ip_conntrack_info ctinfo,
 198                                struct nf_conn *ct,
 199                                __be32 newip, u_int16_t port,
 200                                const char **dptr, unsigned int *datalen)
 201 {
 202         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 203         unsigned int bufflen;
 204
 205         /* Mangle owner and contact info. */
 206         bufflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(newip));
 207         if (!mangle_sip_packet(skb, ctinfo, ct, dptr, datalen,
 208                                buffer, bufflen, POS_OWNER_IP4))
 209                 return 0;
 210
 211         if (!mangle_sip_packet(skb, ctinfo, ct, dptr, datalen,
 212                                buffer, bufflen, POS_CONNECTION_IP4))
 213                 return 0;
 214
 215         /* Mangle media port. */
 216         bufflen = sprintf(buffer, "%u", port);
 217         if (!mangle_sip_packet(skb, ctinfo, ct, dptr, datalen,
 218                                buffer, bufflen, POS_MEDIA))
 219                 return 0;
 220
 221         return mangle_content_len(skb, ctinfo, ct, dptr, datalen);
 222 }
 223
 224 static void ip_nat_sdp_expect(struct nf_conn *ct,
 225                               struct nf_conntrack_expect *exp)
 226 {
 227         struct nf_nat_range range;
 228
 229         /* This must be a fresh one. */
 230         BUG_ON(ct->status & IPS_NAT_DONE_MASK);
 231
 232         /* For DST manip, map port here to where it's expected. */
 233         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
 234         range.min = range.max = exp->saved_proto;
 235         range.min_ip = range.max_ip = exp->saved_ip;
 236         nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST);
 237
 238         /* Change src to where master sends to */
 239         range.flags = IP_NAT_RANGE_MAP_IPS;
 240         range.min_ip = range.max_ip
 241                 = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
 242         nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC);
 243 }
 244
 245 /* So, this packet has hit the connection tracking matching code.
 246    Mangle it, and change the expectation to match the new version. */
 247 static unsigned int ip_nat_sdp(struct sk_buff *skb,
 248                                enum ip_conntrack_info ctinfo,
 249                                struct nf_conntrack_expect *exp,
 250                                const char **dptr, unsigned int *datalen)
 251 {
 252         struct nf_conn *ct = exp->master;
 253         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 254         __be32 newip;
 255         u_int16_t port;
 256
 257         /* Connection will come from reply */
 258         if (ct->tuplehash[dir].tuple.src.u3.ip ==
 259             ct->tuplehash[!dir].tuple.dst.u3.ip)
 260                 newip = exp->tuple.dst.u3.ip;
 261         else
 262                 newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 263
 264         exp->saved_ip = exp->tuple.dst.u3.ip;
 265         exp->tuple.dst.u3.ip = newip;
 266         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
 267         exp->dir = !dir;
 268
 269         /* When you see the packet, we need to NAT it the same as the
 270            this one. */
 271         exp->expectfn = ip_nat_sdp_expect;
 272
 273         /* Try to get same port: if not, try to change it. */
 274         for (port = ntohs(exp->saved_proto.udp.port); port != 0; port++) {
 275                 exp->tuple.dst.u.udp.port = htons(port);
 276                 if (nf_ct_expect_related(exp) == 0)
 277                         break;
 278         }
 279
 280         if (port == 0)
 281                 return NF_DROP;
 282
 283         if (!mangle_sdp(skb, ctinfo, ct, newip, port, dptr, datalen)) {
 284                 nf_ct_unexpect_related(exp);
 285                 return NF_DROP;
 286         }
 287         return NF_ACCEPT;
 288 }
 289
 290 static void __exit nf_nat_sip_fini(void)
 291 {
 292         rcu_assign_pointer(nf_nat_sip_hook, NULL);
 293         rcu_assign_pointer(nf_nat_sdp_hook, NULL);
 294         synchronize_rcu();
 295 }
 296
 297 static int __init nf_nat_sip_init(void)
 298 {
 299         BUG_ON(nf_nat_sip_hook != NULL);
 300         BUG_ON(nf_nat_sdp_hook != NULL);
 301         rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip);
 302         rcu_assign_pointer(nf_nat_sdp_hook, ip_nat_sdp);
 303         return 0;
 304 }
 305
 306 module_init(nf_nat_sip_init);
 307 module_exit(nf_nat_sip_fini);