net/netfilter/ipvs/ip_vs_ftp.c

   1 /*
   2  * ip_vs_ftp.c: IPVS ftp application module
   3  *
   4  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   5  *
   6  * Changes:
   7  *
   8  *
   9  *      This program is free software; you can redistribute it and/or
  10  *      modify it under the terms of the GNU General Public License
  11  *      as published by the Free Software Foundation; either version
  12  *      2 of the License, or (at your option) any later version.
  13  *
  14  * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
  15  * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
  16  *
  17  *              IP_MASQ_FTP ftp masquerading module
  18  *
  19  * Version:     @(#)ip_masq_ftp.c 0.04   02/05/96
  20  *
  21  * Author:      Wouter Gadeyne
  22  *
  23  */
  24
  25 #define KMSG_COMPONENT "IPVS"
  26 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  27
  28 #include <linux/module.h>
  29 #include <linux/moduleparam.h>
  30 #include <linux/kernel.h>
  31 #include <linux/skbuff.h>
  32 #include <linux/in.h>
  33 #include <linux/ip.h>
  34 #include <linux/netfilter.h>
  35 #include <net/netfilter/nf_conntrack.h>
  36 #include <net/netfilter/nf_conntrack_expect.h>
  37 #include <net/netfilter/nf_nat.h>
  38 #include <net/netfilter/nf_nat_helper.h>
  39 #include <linux/gfp.h>
  40 #include <net/protocol.h>
  41 #include <net/tcp.h>
  42 #include <asm/unaligned.h>
  43
  44 #include <net/ip_vs.h>
  45
  46
  47 #define SERVER_STRING "227 Entering Passive Mode ("
  48 #define CLIENT_STRING "PORT "
  49
  50
  51 /*
  52  * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  53  * First port is set to the default port.
  54  */
  55 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  56 module_param_array(ports, ushort, NULL, 0);
  57 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  58
  59
  60 /*      Dummy variable */
  61 static int ip_vs_ftp_pasv;
  62
  63
  64 static int
  65 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  66 {
  67         /* We use connection tracking for the command connection */
  68         cp->flags |= IP_VS_CONN_F_NFCT;
  69         return 0;
  70 }
  71
  72
  73 static int
  74 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  75 {
  76         return 0;
  77 }
  78
  79
  80 /*
  81  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  82  * with the "pattern" and terminated with the "term" character.
  83  * <addr,port> is in network order.
  84  */
  85 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  86                                   const char *pattern, size_t plen, char term,
  87                                   __be32 *addr, __be16 *port,
  88                                   char **start, char **end)
  89 {
  90         unsigned char p[6];
  91         int i = 0;
  92
  93         if (data_limit - data < plen) {
  94                 /* check if there is partial match */
  95                 if (strnicmp(data, pattern, data_limit - data) == 0)
  96                         return -1;
  97                 else
  98                         return 0;
  99         }
 100
 101         if (strnicmp(data, pattern, plen) != 0) {
 102                 return 0;
 103         }
 104         *start = data + plen;
 105
 106         for (data = *start; *data != term; data++) {
 107                 if (data == data_limit)
 108                         return -1;
 109         }
 110         *end = data;
 111
 112         memset(p, 0, sizeof(p));
 113         for (data = *start; data != *end; data++) {
 114                 if (*data >= '0' && *data <= '9') {
 115                         p[i] = p[i]*10 + *data - '0';
 116                 } else if (*data == ',' && i < 5) {
 117                         i++;
 118                 } else {
 119                         /* unexpected character */
 120                         return -1;
 121                 }
 122         }
 123
 124         if (i != 5)
 125                 return -1;
 126
 127         *addr = get_unaligned((__be32 *)p);
 128         *port = get_unaligned((__be16 *)(p + 4));
 129         return 1;
 130 }
 131
 132 /*
 133  * Look at outgoing ftp packets to catch the response to a PASV command
 134  * from the server (inside-to-outside).
 135  * When we see one, we build a connection entry with the client address,
 136  * client port 0 (unknown at the moment), the server address and the
 137  * server port.  Mark the current connection entry as a control channel
 138  * of the new entry. All this work is just to make the data connection
 139  * can be scheduled to the right server later.
 140  *
 141  * The outgoing packet should be something like
 142  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 143  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 144  */
 145 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 146                          struct sk_buff *skb, int *diff)
 147 {
 148         struct iphdr *iph;
 149         struct tcphdr *th;
 150         char *data, *data_limit;
 151         char *start, *end;
 152         union nf_inet_addr from;
 153         __be16 port;
 154         struct ip_vs_conn *n_cp;
 155         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 156         unsigned buf_len;
 157         int ret = 0;
 158         enum ip_conntrack_info ctinfo;
 159         struct nf_conn *ct;
 160         struct net *net;
 161
 162 #ifdef CONFIG_IP_VS_IPV6
 163         /* This application helper doesn't work with IPv6 yet,
 164          * so turn this into a no-op for IPv6 packets
 165          */
 166         if (cp->af == AF_INET6)
 167                 return 1;
 168 #endif
 169
 170         *diff = 0;
 171
 172         /* Only useful for established sessions */
 173         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 174                 return 1;
 175
 176         /* Linear packets are much easier to deal with. */
 177         if (!skb_make_writable(skb, skb->len))
 178                 return 0;
 179
 180         if (cp->app_data == &ip_vs_ftp_pasv) {
 181                 iph = ip_hdr(skb);
 182                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 183                 data = (char *)th + (th->doff << 2);
 184                 data_limit = skb_tail_pointer(skb);
 185
 186                 if (ip_vs_ftp_get_addrport(data, data_limit,
 187                                            SERVER_STRING,
 188                                            sizeof(SERVER_STRING)-1, ')',
 189                                            &from.ip, &port,
 190                                            &start, &end) != 1)
 191                         return 1;
 192
 193                 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
 194                           &from.ip, ntohs(port), &cp->caddr.ip, 0);
 195
 196                 /*
 197                  * Now update or create an connection entry for it
 198                  */
 199                 {
 200                         struct ip_vs_conn_param p;
 201                         ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
 202                                               iph->protocol, &from, port,
 203                                               &cp->caddr, 0, &p);
 204                         n_cp = ip_vs_conn_out_get(&p);
 205                 }
 206                 if (!n_cp) {
 207                         struct ip_vs_conn_param p;
 208                         ip_vs_conn_fill_param(ip_vs_conn_net(cp),
 209                                               AF_INET, IPPROTO_TCP, &cp->caddr,
 210                                               0, &cp->vaddr, port, &p);
 211                         n_cp = ip_vs_conn_new(&p, &from, port,
 212                                               IP_VS_CONN_F_NO_CPORT |
 213                                               IP_VS_CONN_F_NFCT,
 214                                               cp->dest, skb->mark);
 215                         if (!n_cp)
 216                                 return 0;
 217
 218                         /* add its controller */
 219                         ip_vs_control_add(n_cp, cp);
 220                 }
 221
 222                 /*
 223                  * Replace the old passive address with the new one
 224                  */
 225                 from.ip = n_cp->vaddr.ip;
 226                 port = n_cp->vport;
 227                 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 228                          ((unsigned char *)&from.ip)[0],
 229                          ((unsigned char *)&from.ip)[1],
 230                          ((unsigned char *)&from.ip)[2],
 231                          ((unsigned char *)&from.ip)[3],
 232                          ntohs(port) >> 8,
 233                          ntohs(port) & 0xFF);
 234
 235                 buf_len = strlen(buf);
 236
 237                 ct = nf_ct_get(skb, &ctinfo);
 238                 if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
 239                         /* If mangling fails this function will return 0
 240                          * which will cause the packet to be dropped.
 241                          * Mangling can only fail under memory pressure,
 242                          * hopefully it will succeed on the retransmitted
 243                          * packet.
 244                          */
 245                         ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 246                                                        start-data, end-start,
 247                                                        buf, buf_len);
 248                         if (ret) {
 249                                 ip_vs_nfct_expect_related(skb, ct, n_cp,
 250                                                           IPPROTO_TCP, 0, 0);
 251                                 if (skb->ip_summed == CHECKSUM_COMPLETE)
 252                                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 253                                 /* csum is updated */
 254                                 ret = 1;
 255                         }
 256                 }
 257
 258                 /*
 259                  * Not setting 'diff' is intentional, otherwise the sequence
 260                  * would be adjusted twice.
 261                  */
 262
 263                 net = skb_net(skb);
 264                 cp->app_data = NULL;
 265                 ip_vs_tcp_conn_listen(net, n_cp);
 266                 ip_vs_conn_put(n_cp);
 267                 return ret;
 268         }
 269         return 1;
 270 }
 271
 272
 273 /*
 274  * Look at incoming ftp packets to catch the PASV/PORT command
 275  * (outside-to-inside).
 276  *
 277  * The incoming packet having the PORT command should be something like
 278  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 279  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 280  * In this case, we create a connection entry using the client address and
 281  * port, so that the active ftp data connection from the server can reach
 282  * the client.
 283  */
 284 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 285                         struct sk_buff *skb, int *diff)
 286 {
 287         struct iphdr *iph;
 288         struct tcphdr *th;
 289         char *data, *data_start, *data_limit;
 290         char *start, *end;
 291         union nf_inet_addr to;
 292         __be16 port;
 293         struct ip_vs_conn *n_cp;
 294         struct net *net;
 295
 296 #ifdef CONFIG_IP_VS_IPV6
 297         /* This application helper doesn't work with IPv6 yet,
 298          * so turn this into a no-op for IPv6 packets
 299          */
 300         if (cp->af == AF_INET6)
 301                 return 1;
 302 #endif
 303
 304         /* no diff required for incoming packets */
 305         *diff = 0;
 306
 307         /* Only useful for established sessions */
 308         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 309                 return 1;
 310
 311         /* Linear packets are much easier to deal with. */
 312         if (!skb_make_writable(skb, skb->len))
 313                 return 0;
 314
 315         /*
 316          * Detecting whether it is passive
 317          */
 318         iph = ip_hdr(skb);
 319         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 320
 321         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 322            the length of the header in 32-bit multiples, it is accurate
 323            to calculate data address by th+HLEN*4 */
 324         data = data_start = (char *)th + (th->doff << 2);
 325         data_limit = skb_tail_pointer(skb);
 326
 327         while (data <= data_limit - 6) {
 328                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 329                         /* Passive mode on */
 330                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 331                                   data - data_start,
 332                                   data_limit - data_start);
 333                         cp->app_data = &ip_vs_ftp_pasv;
 334                         return 1;
 335                 }
 336                 data++;
 337         }
 338
 339         /*
 340          * To support virtual FTP server, the scenerio is as follows:
 341          *       FTP client ----> Load Balancer ----> FTP server
 342          * First detect the port number in the application data,
 343          * then create a new connection entry for the coming data
 344          * connection.
 345          */
 346         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 347                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 348                                    '\r', &to.ip, &port,
 349                                    &start, &end) != 1)
 350                 return 1;
 351
 352         IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
 353
 354         /* Passive mode off */
 355         cp->app_data = NULL;
 356
 357         /*
 358          * Now update or create a connection entry for it
 359          */
 360         IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
 361                   ip_vs_proto_name(iph->protocol),
 362                   &to.ip, ntohs(port), &cp->vaddr.ip, 0);
 363
 364         {
 365                 struct ip_vs_conn_param p;
 366                 ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
 367                                       iph->protocol, &to, port, &cp->vaddr,
 368                                       htons(ntohs(cp->vport)-1), &p);
 369                 n_cp = ip_vs_conn_in_get(&p);
 370                 if (!n_cp) {
 371                         n_cp = ip_vs_conn_new(&p, &cp->daddr,
 372                                               htons(ntohs(cp->dport)-1),
 373                                               IP_VS_CONN_F_NFCT, cp->dest,
 374                                               skb->mark);
 375                         if (!n_cp)
 376                                 return 0;
 377
 378                         /* add its controller */
 379                         ip_vs_control_add(n_cp, cp);
 380                 }
 381         }
 382
 383         /*
 384          *      Move tunnel to listen state
 385          */
 386         net = skb_net(skb);
 387         ip_vs_tcp_conn_listen(net, n_cp);
 388         ip_vs_conn_put(n_cp);
 389
 390         return 1;
 391 }
 392
 393
 394 static struct ip_vs_app ip_vs_ftp = {
 395         .name =         "ftp",
 396         .type =         IP_VS_APP_TYPE_FTP,
 397         .protocol =     IPPROTO_TCP,
 398         .module =       THIS_MODULE,
 399         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 400         .init_conn =    ip_vs_ftp_init_conn,
 401         .done_conn =    ip_vs_ftp_done_conn,
 402         .bind_conn =    NULL,
 403         .unbind_conn =  NULL,
 404         .pkt_out =      ip_vs_ftp_out,
 405         .pkt_in =       ip_vs_ftp_in,
 406 };
 407
 408 /*
 409  *      per netns ip_vs_ftp initialization
 410  */
 411 static int __net_init __ip_vs_ftp_init(struct net *net)
 412 {
 413         int i, ret;
 414         struct ip_vs_app *app;
 415         struct netns_ipvs *ipvs = net_ipvs(net);
 416
 417         app = kmemdup(&ip_vs_ftp, sizeof(struct ip_vs_app), GFP_KERNEL);
 418         if (!app)
 419                 return -ENOMEM;
 420         INIT_LIST_HEAD(&app->a_list);
 421         INIT_LIST_HEAD(&app->incs_list);
 422         ipvs->ftp_app = app;
 423
 424         ret = register_ip_vs_app(net, app);
 425         if (ret)
 426                 goto err_exit;
 427
 428         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 429                 if (!ports[i])
 430                         continue;
 431                 ret = register_ip_vs_app_inc(net, app, app->protocol, ports[i]);
 432                 if (ret)
 433                         goto err_unreg;
 434                 pr_info("%s: loaded support on port[%d] = %d\n",
 435                         app->name, i, ports[i]);
 436         }
 437         return 0;
 438
 439 err_unreg:
 440         unregister_ip_vs_app(net, app);
 441 err_exit:
 442         kfree(ipvs->ftp_app);
 443         return ret;
 444 }
 445 /*
 446  *      netns exit
 447  */
 448 static void __ip_vs_ftp_exit(struct net *net)
 449 {
 450         struct netns_ipvs *ipvs = net_ipvs(net);
 451
 452         unregister_ip_vs_app(net, ipvs->ftp_app);
 453         kfree(ipvs->ftp_app);
 454 }
 455
 456 static struct pernet_operations ip_vs_ftp_ops = {
 457         .init = __ip_vs_ftp_init,
 458         .exit = __ip_vs_ftp_exit,
 459 };
 460
 461 int __init ip_vs_ftp_init(void)
 462 {
 463         int rv;
 464
 465         rv = register_pernet_subsys(&ip_vs_ftp_ops);
 466         return rv;
 467 }
 468
 469 /*
 470  *      ip_vs_ftp finish.
 471  */
 472 static void __exit ip_vs_ftp_exit(void)
 473 {
 474         unregister_pernet_subsys(&ip_vs_ftp_ops);
 475 }
 476
 477
 478 module_init(ip_vs_ftp_init);
 479 module_exit(ip_vs_ftp_exit);
 480 MODULE_LICENSE("GPL");