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 "
  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", ignoring before "skip" and terminated with
  83  * the "term" character.
  84  * <addr,port> is in network order.
  85  */
  86 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  87                                   const char *pattern, size_t plen,
  88                                   char skip, char term,
  89                                   __be32 *addr, __be16 *port,
  90                                   char **start, char **end)
  91 {
  92         char *s, c;
  93         unsigned char p[6];
  94         int i = 0;
  95
  96         if (data_limit - data < plen) {
  97                 /* check if there is partial match */
  98                 if (strnicmp(data, pattern, data_limit - data) == 0)
  99                         return -1;
 100                 else
 101                         return 0;
 102         }
 103
 104         if (strnicmp(data, pattern, plen) != 0) {
 105                 return 0;
 106         }
 107         s = data + plen;
 108         if (skip) {
 109                 int found = 0;
 110
 111                 for (;; s++) {
 112                         if (s == data_limit)
 113                                 return -1;
 114                         if (!found) {
 115                                 if (*s == skip)
 116                                         found = 1;
 117                         } else if (*s != skip) {
 118                                 break;
 119                         }
 120                 }
 121         }
 122
 123         for (data = s; ; data++) {
 124                 if (data == data_limit)
 125                         return -1;
 126                 if (*data == term)
 127                         break;
 128         }
 129         *end = data;
 130
 131         memset(p, 0, sizeof(p));
 132         for (data = s; ; data++) {
 133                 c = *data;
 134                 if (c == term)
 135                         break;
 136                 if (c >= '0' && c <= '9') {
 137                         p[i] = p[i]*10 + c - '0';
 138                 } else if (c == ',' && i < 5) {
 139                         i++;
 140                 } else {
 141                         /* unexpected character */
 142                         return -1;
 143                 }
 144         }
 145
 146         if (i != 5)
 147                 return -1;
 148
 149         *start = s;
 150         *addr = get_unaligned((__be32 *) p);
 151         *port = get_unaligned((__be16 *) (p + 4));
 152         return 1;
 153 }
 154
 155 /*
 156  * Look at outgoing ftp packets to catch the response to a PASV command
 157  * from the server (inside-to-outside).
 158  * When we see one, we build a connection entry with the client address,
 159  * client port 0 (unknown at the moment), the server address and the
 160  * server port.  Mark the current connection entry as a control channel
 161  * of the new entry. All this work is just to make the data connection
 162  * can be scheduled to the right server later.
 163  *
 164  * The outgoing packet should be something like
 165  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 166  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 167  */
 168 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 169                          struct sk_buff *skb, int *diff)
 170 {
 171         struct iphdr *iph;
 172         struct tcphdr *th;
 173         char *data, *data_limit;
 174         char *start, *end;
 175         union nf_inet_addr from;
 176         __be16 port;
 177         struct ip_vs_conn *n_cp;
 178         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 179         unsigned buf_len;
 180         int ret = 0;
 181         enum ip_conntrack_info ctinfo;
 182         struct nf_conn *ct;
 183         struct net *net;
 184
 185 #ifdef CONFIG_IP_VS_IPV6
 186         /* This application helper doesn't work with IPv6 yet,
 187          * so turn this into a no-op for IPv6 packets
 188          */
 189         if (cp->af == AF_INET6)
 190                 return 1;
 191 #endif
 192
 193         *diff = 0;
 194
 195         /* Only useful for established sessions */
 196         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 197                 return 1;
 198
 199         /* Linear packets are much easier to deal with. */
 200         if (!skb_make_writable(skb, skb->len))
 201                 return 0;
 202
 203         if (cp->app_data == &ip_vs_ftp_pasv) {
 204                 iph = ip_hdr(skb);
 205                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 206                 data = (char *)th + (th->doff << 2);
 207                 data_limit = skb_tail_pointer(skb);
 208
 209                 if (ip_vs_ftp_get_addrport(data, data_limit,
 210                                            SERVER_STRING,
 211                                            sizeof(SERVER_STRING)-1,
 212                                            '(', ')',
 213                                            &from.ip, &port,
 214                                            &start, &end) != 1)
 215                         return 1;
 216
 217                 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
 218                           &from.ip, ntohs(port), &cp->caddr.ip, 0);
 219
 220                 /*
 221                  * Now update or create an connection entry for it
 222                  */
 223                 {
 224                         struct ip_vs_conn_param p;
 225                         ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
 226                                               iph->protocol, &from, port,
 227                                               &cp->caddr, 0, &p);
 228                         n_cp = ip_vs_conn_out_get(&p);
 229                 }
 230                 if (!n_cp) {
 231                         struct ip_vs_conn_param p;
 232                         ip_vs_conn_fill_param(ip_vs_conn_net(cp),
 233                                               AF_INET, IPPROTO_TCP, &cp->caddr,
 234                                               0, &cp->vaddr, port, &p);
 235                         n_cp = ip_vs_conn_new(&p, &from, port,
 236                                               IP_VS_CONN_F_NO_CPORT |
 237                                               IP_VS_CONN_F_NFCT,
 238                                               cp->dest, skb->mark);
 239                         if (!n_cp)
 240                                 return 0;
 241
 242                         /* add its controller */
 243                         ip_vs_control_add(n_cp, cp);
 244                 }
 245
 246                 /*
 247                  * Replace the old passive address with the new one
 248                  */
 249                 from.ip = n_cp->vaddr.ip;
 250                 port = n_cp->vport;
 251                 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 252                          ((unsigned char *)&from.ip)[0],
 253                          ((unsigned char *)&from.ip)[1],
 254                          ((unsigned char *)&from.ip)[2],
 255                          ((unsigned char *)&from.ip)[3],
 256                          ntohs(port) >> 8,
 257                          ntohs(port) & 0xFF);
 258
 259                 buf_len = strlen(buf);
 260
 261                 ct = nf_ct_get(skb, &ctinfo);
 262                 if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
 263                         /* If mangling fails this function will return 0
 264                          * which will cause the packet to be dropped.
 265                          * Mangling can only fail under memory pressure,
 266                          * hopefully it will succeed on the retransmitted
 267                          * packet.
 268                          */
 269                         ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 270                                                        start-data, end-start,
 271                                                        buf, buf_len);
 272                         if (ret) {
 273                                 ip_vs_nfct_expect_related(skb, ct, n_cp,
 274                                                           IPPROTO_TCP, 0, 0);
 275                                 if (skb->ip_summed == CHECKSUM_COMPLETE)
 276                                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 277                                 /* csum is updated */
 278                                 ret = 1;
 279                         }
 280                 }
 281
 282                 /*
 283                  * Not setting 'diff' is intentional, otherwise the sequence
 284                  * would be adjusted twice.
 285                  */
 286
 287                 net = skb_net(skb);
 288                 cp->app_data = NULL;
 289                 ip_vs_tcp_conn_listen(net, n_cp);
 290                 ip_vs_conn_put(n_cp);
 291                 return ret;
 292         }
 293         return 1;
 294 }
 295
 296
 297 /*
 298  * Look at incoming ftp packets to catch the PASV/PORT command
 299  * (outside-to-inside).
 300  *
 301  * The incoming packet having the PORT command should be something like
 302  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 303  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 304  * In this case, we create a connection entry using the client address and
 305  * port, so that the active ftp data connection from the server can reach
 306  * the client.
 307  */
 308 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 309                         struct sk_buff *skb, int *diff)
 310 {
 311         struct iphdr *iph;
 312         struct tcphdr *th;
 313         char *data, *data_start, *data_limit;
 314         char *start, *end;
 315         union nf_inet_addr to;
 316         __be16 port;
 317         struct ip_vs_conn *n_cp;
 318         struct net *net;
 319
 320 #ifdef CONFIG_IP_VS_IPV6
 321         /* This application helper doesn't work with IPv6 yet,
 322          * so turn this into a no-op for IPv6 packets
 323          */
 324         if (cp->af == AF_INET6)
 325                 return 1;
 326 #endif
 327
 328         /* no diff required for incoming packets */
 329         *diff = 0;
 330
 331         /* Only useful for established sessions */
 332         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 333                 return 1;
 334
 335         /* Linear packets are much easier to deal with. */
 336         if (!skb_make_writable(skb, skb->len))
 337                 return 0;
 338
 339         /*
 340          * Detecting whether it is passive
 341          */
 342         iph = ip_hdr(skb);
 343         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 344
 345         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 346            the length of the header in 32-bit multiples, it is accurate
 347            to calculate data address by th+HLEN*4 */
 348         data = data_start = (char *)th + (th->doff << 2);
 349         data_limit = skb_tail_pointer(skb);
 350
 351         while (data <= data_limit - 6) {
 352                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 353                         /* Passive mode on */
 354                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 355                                   data - data_start,
 356                                   data_limit - data_start);
 357                         cp->app_data = &ip_vs_ftp_pasv;
 358                         return 1;
 359                 }
 360                 data++;
 361         }
 362
 363         /*
 364          * To support virtual FTP server, the scenerio is as follows:
 365          *       FTP client ----> Load Balancer ----> FTP server
 366          * First detect the port number in the application data,
 367          * then create a new connection entry for the coming data
 368          * connection.
 369          */
 370         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 371                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 372                                    ' ', '\r', &to.ip, &port,
 373                                    &start, &end) != 1)
 374                 return 1;
 375
 376         IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
 377
 378         /* Passive mode off */
 379         cp->app_data = NULL;
 380
 381         /*
 382          * Now update or create a connection entry for it
 383          */
 384         IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
 385                   ip_vs_proto_name(iph->protocol),
 386                   &to.ip, ntohs(port), &cp->vaddr.ip, 0);
 387
 388         {
 389                 struct ip_vs_conn_param p;
 390                 ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
 391                                       iph->protocol, &to, port, &cp->vaddr,
 392                                       htons(ntohs(cp->vport)-1), &p);
 393                 n_cp = ip_vs_conn_in_get(&p);
 394                 if (!n_cp) {
 395                         n_cp = ip_vs_conn_new(&p, &cp->daddr,
 396                                               htons(ntohs(cp->dport)-1),
 397                                               IP_VS_CONN_F_NFCT, cp->dest,
 398                                               skb->mark);
 399                         if (!n_cp)
 400                                 return 0;
 401
 402                         /* add its controller */
 403                         ip_vs_control_add(n_cp, cp);
 404                 }
 405         }
 406
 407         /*
 408          *      Move tunnel to listen state
 409          */
 410         net = skb_net(skb);
 411         ip_vs_tcp_conn_listen(net, n_cp);
 412         ip_vs_conn_put(n_cp);
 413
 414         return 1;
 415 }
 416
 417
 418 static struct ip_vs_app ip_vs_ftp = {
 419         .name =         "ftp",
 420         .type =         IP_VS_APP_TYPE_FTP,
 421         .protocol =     IPPROTO_TCP,
 422         .module =       THIS_MODULE,
 423         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 424         .init_conn =    ip_vs_ftp_init_conn,
 425         .done_conn =    ip_vs_ftp_done_conn,
 426         .bind_conn =    NULL,
 427         .unbind_conn =  NULL,
 428         .pkt_out =      ip_vs_ftp_out,
 429         .pkt_in =       ip_vs_ftp_in,
 430 };
 431
 432 /*
 433  *      per netns ip_vs_ftp initialization
 434  */
 435 static int __net_init __ip_vs_ftp_init(struct net *net)
 436 {
 437         int i, ret;
 438         struct ip_vs_app *app;
 439         struct netns_ipvs *ipvs = net_ipvs(net);
 440
 441         app = kmemdup(&ip_vs_ftp, sizeof(struct ip_vs_app), GFP_KERNEL);
 442         if (!app)
 443                 return -ENOMEM;
 444         INIT_LIST_HEAD(&app->a_list);
 445         INIT_LIST_HEAD(&app->incs_list);
 446         ipvs->ftp_app = app;
 447
 448         ret = register_ip_vs_app(net, app);
 449         if (ret)
 450                 goto err_exit;
 451
 452         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 453                 if (!ports[i])
 454                         continue;
 455                 ret = register_ip_vs_app_inc(net, app, app->protocol, ports[i]);
 456                 if (ret)
 457                         goto err_unreg;
 458                 pr_info("%s: loaded support on port[%d] = %d\n",
 459                         app->name, i, ports[i]);
 460         }
 461         return 0;
 462
 463 err_unreg:
 464         unregister_ip_vs_app(net, app);
 465 err_exit:
 466         kfree(ipvs->ftp_app);
 467         return ret;
 468 }
 469 /*
 470  *      netns exit
 471  */
 472 static void __ip_vs_ftp_exit(struct net *net)
 473 {
 474         struct netns_ipvs *ipvs = net_ipvs(net);
 475
 476         unregister_ip_vs_app(net, ipvs->ftp_app);
 477         kfree(ipvs->ftp_app);
 478 }
 479
 480 static struct pernet_operations ip_vs_ftp_ops = {
 481         .init = __ip_vs_ftp_init,
 482         .exit = __ip_vs_ftp_exit,
 483 };
 484
 485 int __init ip_vs_ftp_init(void)
 486 {
 487         int rv;
 488
 489         rv = register_pernet_subsys(&ip_vs_ftp_ops);
 490         return rv;
 491 }
 492
 493 /*
 494  *      ip_vs_ftp finish.
 495  */
 496 static void __exit ip_vs_ftp_exit(void)
 497 {
 498         unregister_pernet_subsys(&ip_vs_ftp_ops);
 499 }
 500
 501
 502 module_init(ip_vs_ftp_init);
 503 module_exit(ip_vs_ftp_exit);
 504 MODULE_LICENSE("GPL");