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 #include <linux/module.h>
  26 #include <linux/moduleparam.h>
  27 #include <linux/kernel.h>
  28 #include <linux/skbuff.h>
  29 #include <linux/in.h>
  30 #include <linux/ip.h>
  31 #include <linux/netfilter.h>
  32 #include <net/protocol.h>
  33 #include <net/tcp.h>
  34 #include <asm/unaligned.h>
  35
  36 #include <net/ip_vs.h>
  37
  38
  39 #define SERVER_STRING "227 Entering Passive Mode ("
  40 #define CLIENT_STRING "PORT "
  41
  42
  43 /*
  44  * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  45  * First port is set to the default port.
  46  */
  47 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  48 module_param_array(ports, ushort, NULL, 0);
  49 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  50
  51
  52 /*      Dummy variable */
  53 static int ip_vs_ftp_pasv;
  54
  55
  56 static int
  57 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  58 {
  59         return 0;
  60 }
  61
  62
  63 static int
  64 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  65 {
  66         return 0;
  67 }
  68
  69
  70 /*
  71  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  72  * with the "pattern" and terminated with the "term" character.
  73  * <addr,port> is in network order.
  74  */
  75 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  76                                   const char *pattern, size_t plen, char term,
  77                                   __be32 *addr, __be16 *port,
  78                                   char **start, char **end)
  79 {
  80         unsigned char p[6];
  81         int i = 0;
  82
  83         if (data_limit - data < plen) {
  84                 /* check if there is partial match */
  85                 if (strnicmp(data, pattern, data_limit - data) == 0)
  86                         return -1;
  87                 else
  88                         return 0;
  89         }
  90
  91         if (strnicmp(data, pattern, plen) != 0) {
  92                 return 0;
  93         }
  94         *start = data + plen;
  95
  96         for (data = *start; *data != term; data++) {
  97                 if (data == data_limit)
  98                         return -1;
  99         }
 100         *end = data;
 101
 102         memset(p, 0, sizeof(p));
 103         for (data = *start; data != *end; data++) {
 104                 if (*data >= '0' && *data <= '9') {
 105                         p[i] = p[i]*10 + *data - '0';
 106                 } else if (*data == ',' && i < 5) {
 107                         i++;
 108                 } else {
 109                         /* unexpected character */
 110                         return -1;
 111                 }
 112         }
 113
 114         if (i != 5)
 115                 return -1;
 116
 117         *addr = get_unaligned((__be32 *)p);
 118         *port = get_unaligned((__be16 *)(p + 4));
 119         return 1;
 120 }
 121
 122
 123 /*
 124  * Look at outgoing ftp packets to catch the response to a PASV command
 125  * from the server (inside-to-outside).
 126  * When we see one, we build a connection entry with the client address,
 127  * client port 0 (unknown at the moment), the server address and the
 128  * server port.  Mark the current connection entry as a control channel
 129  * of the new entry. All this work is just to make the data connection
 130  * can be scheduled to the right server later.
 131  *
 132  * The outgoing packet should be something like
 133  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 134  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 135  */
 136 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 137                          struct sk_buff *skb, int *diff)
 138 {
 139         struct iphdr *iph;
 140         struct tcphdr *th;
 141         char *data, *data_limit;
 142         char *start, *end;
 143         union nf_inet_addr from;
 144         __be16 port;
 145         struct ip_vs_conn *n_cp;
 146         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 147         unsigned buf_len;
 148         int ret;
 149
 150 #ifdef CONFIG_IP_VS_IPV6
 151         /* This application helper doesn't work with IPv6 yet,
 152          * so turn this into a no-op for IPv6 packets
 153          */
 154         if (cp->af == AF_INET6)
 155                 return 1;
 156 #endif
 157
 158         *diff = 0;
 159
 160         /* Only useful for established sessions */
 161         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 162                 return 1;
 163
 164         /* Linear packets are much easier to deal with. */
 165         if (!skb_make_writable(skb, skb->len))
 166                 return 0;
 167
 168         if (cp->app_data == &ip_vs_ftp_pasv) {
 169                 iph = ip_hdr(skb);
 170                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 171                 data = (char *)th + (th->doff << 2);
 172                 data_limit = skb_tail_pointer(skb);
 173
 174                 if (ip_vs_ftp_get_addrport(data, data_limit,
 175                                            SERVER_STRING,
 176                                            sizeof(SERVER_STRING)-1, ')',
 177                                            &from.ip, &port,
 178                                            &start, &end) != 1)
 179                         return 1;
 180
 181                 IP_VS_DBG(7, "PASV response (%u.%u.%u.%u:%d) -> "
 182                           "%u.%u.%u.%u:%d detected\n",
 183                           NIPQUAD(from.ip), ntohs(port),
 184                           NIPQUAD(cp->caddr.ip), 0);
 185
 186                 /*
 187                  * Now update or create an connection entry for it
 188                  */
 189                 n_cp = ip_vs_conn_out_get(AF_INET, iph->protocol, &from, port,
 190                                           &cp->caddr, 0);
 191                 if (!n_cp) {
 192                         n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
 193                                               &cp->caddr, 0,
 194                                               &cp->vaddr, port,
 195                                               &from, port,
 196                                               IP_VS_CONN_F_NO_CPORT,
 197                                               cp->dest);
 198                         if (!n_cp)
 199                                 return 0;
 200
 201                         /* add its controller */
 202                         ip_vs_control_add(n_cp, cp);
 203                 }
 204
 205                 /*
 206                  * Replace the old passive address with the new one
 207                  */
 208                 from.ip = n_cp->vaddr.ip;
 209                 port = n_cp->vport;
 210                 sprintf(buf, "%d,%d,%d,%d,%d,%d", NIPQUAD(from.ip),
 211                         (ntohs(port)>>8)&255, ntohs(port)&255);
 212                 buf_len = strlen(buf);
 213
 214                 /*
 215                  * Calculate required delta-offset to keep TCP happy
 216                  */
 217                 *diff = buf_len - (end-start);
 218
 219                 if (*diff == 0) {
 220                         /* simply replace it with new passive address */
 221                         memcpy(start, buf, buf_len);
 222                         ret = 1;
 223                 } else {
 224                         ret = !ip_vs_skb_replace(skb, GFP_ATOMIC, start,
 225                                           end-start, buf, buf_len);
 226                 }
 227
 228                 cp->app_data = NULL;
 229                 ip_vs_tcp_conn_listen(n_cp);
 230                 ip_vs_conn_put(n_cp);
 231                 return ret;
 232         }
 233         return 1;
 234 }
 235
 236
 237 /*
 238  * Look at incoming ftp packets to catch the PASV/PORT command
 239  * (outside-to-inside).
 240  *
 241  * The incoming packet having the PORT command should be something like
 242  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 243  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 244  * In this case, we create a connection entry using the client address and
 245  * port, so that the active ftp data connection from the server can reach
 246  * the client.
 247  */
 248 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 249                         struct sk_buff *skb, int *diff)
 250 {
 251         struct iphdr *iph;
 252         struct tcphdr *th;
 253         char *data, *data_start, *data_limit;
 254         char *start, *end;
 255         union nf_inet_addr to;
 256         __be16 port;
 257         struct ip_vs_conn *n_cp;
 258
 259 #ifdef CONFIG_IP_VS_IPV6
 260         /* This application helper doesn't work with IPv6 yet,
 261          * so turn this into a no-op for IPv6 packets
 262          */
 263         if (cp->af == AF_INET6)
 264                 return 1;
 265 #endif
 266
 267         /* no diff required for incoming packets */
 268         *diff = 0;
 269
 270         /* Only useful for established sessions */
 271         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 272                 return 1;
 273
 274         /* Linear packets are much easier to deal with. */
 275         if (!skb_make_writable(skb, skb->len))
 276                 return 0;
 277
 278         /*
 279          * Detecting whether it is passive
 280          */
 281         iph = ip_hdr(skb);
 282         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 283
 284         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 285            the length of the header in 32-bit multiples, it is accurate
 286            to calculate data address by th+HLEN*4 */
 287         data = data_start = (char *)th + (th->doff << 2);
 288         data_limit = skb_tail_pointer(skb);
 289
 290         while (data <= data_limit - 6) {
 291                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 292                         /* Passive mode on */
 293                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 294                                   data - data_start,
 295                                   data_limit - data_start);
 296                         cp->app_data = &ip_vs_ftp_pasv;
 297                         return 1;
 298                 }
 299                 data++;
 300         }
 301
 302         /*
 303          * To support virtual FTP server, the scenerio is as follows:
 304          *       FTP client ----> Load Balancer ----> FTP server
 305          * First detect the port number in the application data,
 306          * then create a new connection entry for the coming data
 307          * connection.
 308          */
 309         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 310                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 311                                    '\r', &to.ip, &port,
 312                                    &start, &end) != 1)
 313                 return 1;
 314
 315         IP_VS_DBG(7, "PORT %u.%u.%u.%u:%d detected\n",
 316                   NIPQUAD(to.ip), ntohs(port));
 317
 318         /* Passive mode off */
 319         cp->app_data = NULL;
 320
 321         /*
 322          * Now update or create a connection entry for it
 323          */
 324         IP_VS_DBG(7, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
 325                   ip_vs_proto_name(iph->protocol),
 326                   NIPQUAD(to.ip), ntohs(port), NIPQUAD(cp->vaddr.ip), 0);
 327
 328         n_cp = ip_vs_conn_in_get(AF_INET, iph->protocol,
 329                                  &to, port,
 330                                  &cp->vaddr, htons(ntohs(cp->vport)-1));
 331         if (!n_cp) {
 332                 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
 333                                       &to, port,
 334                                       &cp->vaddr, htons(ntohs(cp->vport)-1),
 335                                       &cp->daddr, htons(ntohs(cp->dport)-1),
 336                                       0,
 337                                       cp->dest);
 338                 if (!n_cp)
 339                         return 0;
 340
 341                 /* add its controller */
 342                 ip_vs_control_add(n_cp, cp);
 343         }
 344
 345         /*
 346          *      Move tunnel to listen state
 347          */
 348         ip_vs_tcp_conn_listen(n_cp);
 349         ip_vs_conn_put(n_cp);
 350
 351         return 1;
 352 }
 353
 354
 355 static struct ip_vs_app ip_vs_ftp = {
 356         .name =         "ftp",
 357         .type =         IP_VS_APP_TYPE_FTP,
 358         .protocol =     IPPROTO_TCP,
 359         .module =       THIS_MODULE,
 360         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 361         .init_conn =    ip_vs_ftp_init_conn,
 362         .done_conn =    ip_vs_ftp_done_conn,
 363         .bind_conn =    NULL,
 364         .unbind_conn =  NULL,
 365         .pkt_out =      ip_vs_ftp_out,
 366         .pkt_in =       ip_vs_ftp_in,
 367 };
 368
 369
 370 /*
 371  *      ip_vs_ftp initialization
 372  */
 373 static int __init ip_vs_ftp_init(void)
 374 {
 375         int i, ret;
 376         struct ip_vs_app *app = &ip_vs_ftp;
 377
 378         ret = register_ip_vs_app(app);
 379         if (ret)
 380                 return ret;
 381
 382         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 383                 if (!ports[i])
 384                         continue;
 385                 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
 386                 if (ret)
 387                         break;
 388                 IP_VS_INFO("%s: loaded support on port[%d] = %d\n",
 389                            app->name, i, ports[i]);
 390         }
 391
 392         if (ret)
 393                 unregister_ip_vs_app(app);
 394
 395         return ret;
 396 }
 397
 398
 399 /*
 400  *      ip_vs_ftp finish.
 401  */
 402 static void __exit ip_vs_ftp_exit(void)
 403 {
 404         unregister_ip_vs_app(&ip_vs_ftp);
 405 }
 406
 407
 408 module_init(ip_vs_ftp_init);
 409 module_exit(ip_vs_ftp_exit);
 410 MODULE_LICENSE("GPL");