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 int ports_count = 1;
  56 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  57 module_param_array(ports, ushort, &ports_count, 0444);
  58 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  59
  60
  61 /*      Dummy variable */
  62 static int ip_vs_ftp_pasv;
  63
  64
  65 static int
  66 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  67 {
  68         /* We use connection tracking for the command connection */
  69         cp->flags |= IP_VS_CONN_F_NFCT;
  70         return 0;
  71 }
  72
  73
  74 static int
  75 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  76 {
  77         return 0;
  78 }
  79
  80
  81 /*
  82  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  83  * with the "pattern", ignoring before "skip" and terminated with
  84  * the "term" character.
  85  * <addr,port> is in network order.
  86  */
  87 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  88                                   const char *pattern, size_t plen,
  89                                   char skip, char term,
  90                                   __be32 *addr, __be16 *port,
  91                                   char **start, char **end)
  92 {
  93         char *s, c;
  94         unsigned char p[6];
  95         int i = 0;
  96
  97         if (data_limit - data < plen) {
  98                 /* check if there is partial match */
  99                 if (strncasecmp(data, pattern, data_limit - data) == 0)
 100                         return -1;
 101                 else
 102                         return 0;
 103         }
 104
 105         if (strncasecmp(data, pattern, plen) != 0) {
 106                 return 0;
 107         }
 108         s = data + plen;
 109         if (skip) {
 110                 int found = 0;
 111
 112                 for (;; s++) {
 113                         if (s == data_limit)
 114                                 return -1;
 115                         if (!found) {
 116                                 if (*s == skip)
 117                                         found = 1;
 118                         } else if (*s != skip) {
 119                                 break;
 120                         }
 121                 }
 122         }
 123
 124         for (data = s; ; data++) {
 125                 if (data == data_limit)
 126                         return -1;
 127                 if (*data == term)
 128                         break;
 129         }
 130         *end = data;
 131
 132         memset(p, 0, sizeof(p));
 133         for (data = s; ; data++) {
 134                 c = *data;
 135                 if (c == term)
 136                         break;
 137                 if (c >= '0' && c <= '9') {
 138                         p[i] = p[i]*10 + c - '0';
 139                 } else if (c == ',' && i < 5) {
 140                         i++;
 141                 } else {
 142                         /* unexpected character */
 143                         return -1;
 144                 }
 145         }
 146
 147         if (i != 5)
 148                 return -1;
 149
 150         *start = s;
 151         *addr = get_unaligned((__be32 *) p);
 152         *port = get_unaligned((__be16 *) (p + 4));
 153         return 1;
 154 }
 155
 156 /*
 157  * Look at outgoing ftp packets to catch the response to a PASV command
 158  * from the server (inside-to-outside).
 159  * When we see one, we build a connection entry with the client address,
 160  * client port 0 (unknown at the moment), the server address and the
 161  * server port.  Mark the current connection entry as a control channel
 162  * of the new entry. All this work is just to make the data connection
 163  * can be scheduled to the right server later.
 164  *
 165  * The outgoing packet should be something like
 166  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 167  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 168  */
 169 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 170                          struct sk_buff *skb, int *diff)
 171 {
 172         struct iphdr *iph;
 173         struct tcphdr *th;
 174         char *data, *data_limit;
 175         char *start, *end;
 176         union nf_inet_addr from;
 177         __be16 port;
 178         struct ip_vs_conn *n_cp;
 179         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 180         unsigned int buf_len;
 181         int ret = 0;
 182         enum ip_conntrack_info ctinfo;
 183         struct nf_conn *ct;
 184
 185         *diff = 0;
 186
 187 #ifdef CONFIG_IP_VS_IPV6
 188         /* This application helper doesn't work with IPv6 yet,
 189          * so turn this into a no-op for IPv6 packets
 190          */
 191         if (cp->af == AF_INET6)
 192                 return 1;
 193 #endif
 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(cp->ipvs, 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(cp->ipvs,
 233                                               AF_INET, IPPROTO_TCP, &cp->caddr,
 234                                               0, &cp->vaddr, port, &p);
 235                         /* As above, this is ipv4 only */
 236                         n_cp = ip_vs_conn_new(&p, AF_INET, &from, port,
 237                                               IP_VS_CONN_F_NO_CPORT |
 238                                               IP_VS_CONN_F_NFCT,
 239                                               cp->dest, skb->mark);
 240                         if (!n_cp)
 241                                 return 0;
 242
 243                         /* add its controller */
 244                         ip_vs_control_add(n_cp, cp);
 245                 }
 246
 247                 /*
 248                  * Replace the old passive address with the new one
 249                  */
 250                 from.ip = n_cp->vaddr.ip;
 251                 port = n_cp->vport;
 252                 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 253                          ((unsigned char *)&from.ip)[0],
 254                          ((unsigned char *)&from.ip)[1],
 255                          ((unsigned char *)&from.ip)[2],
 256                          ((unsigned char *)&from.ip)[3],
 257                          ntohs(port) >> 8,
 258                          ntohs(port) & 0xFF);
 259
 260                 buf_len = strlen(buf);
 261
 262                 ct = nf_ct_get(skb, &ctinfo);
 263                 if (ct) {
 264                         bool mangled;
 265
 266                         /* If mangling fails this function will return 0
 267                          * which will cause the packet to be dropped.
 268                          * Mangling can only fail under memory pressure,
 269                          * hopefully it will succeed on the retransmitted
 270                          * packet.
 271                          */
 272                         mangled = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 273                                                            iph->ihl * 4,
 274                                                            start - data,
 275                                                            end - start,
 276                                                            buf, buf_len);
 277                         if (mangled) {
 278                                 ip_vs_nfct_expect_related(skb, ct, n_cp,
 279                                                           IPPROTO_TCP, 0, 0);
 280                                 if (skb->ip_summed == CHECKSUM_COMPLETE)
 281                                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 282                                 /* csum is updated */
 283                                 ret = 1;
 284                         }
 285                 }
 286
 287                 /*
 288                  * Not setting 'diff' is intentional, otherwise the sequence
 289                  * would be adjusted twice.
 290                  */
 291
 292                 cp->app_data = NULL;
 293                 ip_vs_tcp_conn_listen(n_cp);
 294                 ip_vs_conn_put(n_cp);
 295                 return ret;
 296         }
 297         return 1;
 298 }
 299
 300
 301 /*
 302  * Look at incoming ftp packets to catch the PASV/PORT command
 303  * (outside-to-inside).
 304  *
 305  * The incoming packet having the PORT command should be something like
 306  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 307  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 308  * In this case, we create a connection entry using the client address and
 309  * port, so that the active ftp data connection from the server can reach
 310  * the client.
 311  */
 312 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 313                         struct sk_buff *skb, int *diff)
 314 {
 315         struct iphdr *iph;
 316         struct tcphdr *th;
 317         char *data, *data_start, *data_limit;
 318         char *start, *end;
 319         union nf_inet_addr to;
 320         __be16 port;
 321         struct ip_vs_conn *n_cp;
 322
 323         /* no diff required for incoming packets */
 324         *diff = 0;
 325
 326 #ifdef CONFIG_IP_VS_IPV6
 327         /* This application helper doesn't work with IPv6 yet,
 328          * so turn this into a no-op for IPv6 packets
 329          */
 330         if (cp->af == AF_INET6)
 331                 return 1;
 332 #endif
 333
 334         /* Only useful for established sessions */
 335         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 336                 return 1;
 337
 338         /* Linear packets are much easier to deal with. */
 339         if (!skb_make_writable(skb, skb->len))
 340                 return 0;
 341
 342         /*
 343          * Detecting whether it is passive
 344          */
 345         iph = ip_hdr(skb);
 346         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 347
 348         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 349            the length of the header in 32-bit multiples, it is accurate
 350            to calculate data address by th+HLEN*4 */
 351         data = data_start = (char *)th + (th->doff << 2);
 352         data_limit = skb_tail_pointer(skb);
 353
 354         while (data <= data_limit - 6) {
 355                 if (strncasecmp(data, "PASV\r\n", 6) == 0) {
 356                         /* Passive mode on */
 357                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 358                                   data - data_start,
 359                                   data_limit - data_start);
 360                         cp->app_data = &ip_vs_ftp_pasv;
 361                         return 1;
 362                 }
 363                 data++;
 364         }
 365
 366         /*
 367          * To support virtual FTP server, the scenerio is as follows:
 368          *       FTP client ----> Load Balancer ----> FTP server
 369          * First detect the port number in the application data,
 370          * then create a new connection entry for the coming data
 371          * connection.
 372          */
 373         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 374                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 375                                    ' ', '\r', &to.ip, &port,
 376                                    &start, &end) != 1)
 377                 return 1;
 378
 379         IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
 380
 381         /* Passive mode off */
 382         cp->app_data = NULL;
 383
 384         /*
 385          * Now update or create a connection entry for it
 386          */
 387         IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
 388                   ip_vs_proto_name(iph->protocol),
 389                   &to.ip, ntohs(port), &cp->vaddr.ip, 0);
 390
 391         {
 392                 struct ip_vs_conn_param p;
 393                 ip_vs_conn_fill_param(cp->ipvs, AF_INET,
 394                                       iph->protocol, &to, port, &cp->vaddr,
 395                                       htons(ntohs(cp->vport)-1), &p);
 396                 n_cp = ip_vs_conn_in_get(&p);
 397                 if (!n_cp) {
 398                         /* This is ipv4 only */
 399                         n_cp = ip_vs_conn_new(&p, AF_INET, &cp->daddr,
 400                                               htons(ntohs(cp->dport)-1),
 401                                               IP_VS_CONN_F_NFCT, cp->dest,
 402                                               skb->mark);
 403                         if (!n_cp)
 404                                 return 0;
 405
 406                         /* add its controller */
 407                         ip_vs_control_add(n_cp, cp);
 408                 }
 409         }
 410
 411         /*
 412          *      Move tunnel to listen state
 413          */
 414         ip_vs_tcp_conn_listen(n_cp);
 415         ip_vs_conn_put(n_cp);
 416
 417         return 1;
 418 }
 419
 420
 421 static struct ip_vs_app ip_vs_ftp = {
 422         .name =         "ftp",
 423         .type =         IP_VS_APP_TYPE_FTP,
 424         .protocol =     IPPROTO_TCP,
 425         .module =       THIS_MODULE,
 426         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 427         .init_conn =    ip_vs_ftp_init_conn,
 428         .done_conn =    ip_vs_ftp_done_conn,
 429         .bind_conn =    NULL,
 430         .unbind_conn =  NULL,
 431         .pkt_out =      ip_vs_ftp_out,
 432         .pkt_in =       ip_vs_ftp_in,
 433 };
 434
 435 /*
 436  *      per netns ip_vs_ftp initialization
 437  */
 438 static int __net_init __ip_vs_ftp_init(struct net *net)
 439 {
 440         int i, ret;
 441         struct ip_vs_app *app;
 442         struct netns_ipvs *ipvs = net_ipvs(net);
 443
 444         if (!ipvs)
 445                 return -ENOENT;
 446
 447         app = register_ip_vs_app(ipvs, &ip_vs_ftp);
 448         if (IS_ERR(app))
 449                 return PTR_ERR(app);
 450
 451         for (i = 0; i < ports_count; i++) {
 452                 if (!ports[i])
 453                         continue;
 454                 ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
 455                 if (ret)
 456                         goto err_unreg;
 457                 pr_info("%s: loaded support on port[%d] = %d\n",
 458                         app->name, i, ports[i]);
 459         }
 460         return 0;
 461
 462 err_unreg:
 463         unregister_ip_vs_app(ipvs, &ip_vs_ftp);
 464         return ret;
 465 }
 466 /*
 467  *      netns exit
 468  */
 469 static void __ip_vs_ftp_exit(struct net *net)
 470 {
 471         struct netns_ipvs *ipvs = net_ipvs(net);
 472
 473         if (!ipvs)
 474                 return;
 475
 476         unregister_ip_vs_app(ipvs, &ip_vs_ftp);
 477 }
 478
 479 static struct pernet_operations ip_vs_ftp_ops = {
 480         .init = __ip_vs_ftp_init,
 481         .exit = __ip_vs_ftp_exit,
 482 };
 483
 484 static int __init ip_vs_ftp_init(void)
 485 {
 486         /* rcu_barrier() is called by netns on error */
 487         return register_pernet_subsys(&ip_vs_ftp_ops);
 488 }
 489
 490 /*
 491  *      ip_vs_ftp finish.
 492  */
 493 static void __exit ip_vs_ftp_exit(void)
 494 {
 495         unregister_pernet_subsys(&ip_vs_ftp_ops);
 496         /* rcu_barrier() is called by netns */
 497 }
 498
 499
 500 module_init(ip_vs_ftp_init);
 501 module_exit(ip_vs_ftp_exit);
 502 MODULE_LICENSE("GPL");