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 <linux/gfp.h>
  36 #include <net/protocol.h>
  37 #include <net/tcp.h>
  38 #include <asm/unaligned.h>
  39
  40 #include <net/ip_vs.h>
  41
  42
  43 #define SERVER_STRING "227 Entering Passive Mode ("
  44 #define CLIENT_STRING "PORT "
  45
  46
  47 /*
  48  * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  49  * First port is set to the default port.
  50  */
  51 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  52 module_param_array(ports, ushort, NULL, 0);
  53 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  54
  55
  56 /*      Dummy variable */
  57 static int ip_vs_ftp_pasv;
  58
  59
  60 static int
  61 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  62 {
  63         return 0;
  64 }
  65
  66
  67 static int
  68 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  69 {
  70         return 0;
  71 }
  72
  73
  74 /*
  75  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  76  * with the "pattern" and terminated with the "term" character.
  77  * <addr,port> is in network order.
  78  */
  79 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  80                                   const char *pattern, size_t plen, char term,
  81                                   __be32 *addr, __be16 *port,
  82                                   char **start, char **end)
  83 {
  84         unsigned char p[6];
  85         int i = 0;
  86
  87         if (data_limit - data < plen) {
  88                 /* check if there is partial match */
  89                 if (strnicmp(data, pattern, data_limit - data) == 0)
  90                         return -1;
  91                 else
  92                         return 0;
  93         }
  94
  95         if (strnicmp(data, pattern, plen) != 0) {
  96                 return 0;
  97         }
  98         *start = data + plen;
  99
 100         for (data = *start; *data != term; data++) {
 101                 if (data == data_limit)
 102                         return -1;
 103         }
 104         *end = data;
 105
 106         memset(p, 0, sizeof(p));
 107         for (data = *start; data != *end; data++) {
 108                 if (*data >= '0' && *data <= '9') {
 109                         p[i] = p[i]*10 + *data - '0';
 110                 } else if (*data == ',' && i < 5) {
 111                         i++;
 112                 } else {
 113                         /* unexpected character */
 114                         return -1;
 115                 }
 116         }
 117
 118         if (i != 5)
 119                 return -1;
 120
 121         *addr = get_unaligned((__be32 *)p);
 122         *port = get_unaligned((__be16 *)(p + 4));
 123         return 1;
 124 }
 125
 126
 127 /*
 128  * Look at outgoing ftp packets to catch the response to a PASV command
 129  * from the server (inside-to-outside).
 130  * When we see one, we build a connection entry with the client address,
 131  * client port 0 (unknown at the moment), the server address and the
 132  * server port.  Mark the current connection entry as a control channel
 133  * of the new entry. All this work is just to make the data connection
 134  * can be scheduled to the right server later.
 135  *
 136  * The outgoing packet should be something like
 137  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 138  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 139  */
 140 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 141                          struct sk_buff *skb, int *diff)
 142 {
 143         struct iphdr *iph;
 144         struct tcphdr *th;
 145         char *data, *data_limit;
 146         char *start, *end;
 147         union nf_inet_addr from;
 148         __be16 port;
 149         struct ip_vs_conn *n_cp;
 150         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 151         unsigned buf_len;
 152         int ret;
 153
 154 #ifdef CONFIG_IP_VS_IPV6
 155         /* This application helper doesn't work with IPv6 yet,
 156          * so turn this into a no-op for IPv6 packets
 157          */
 158         if (cp->af == AF_INET6)
 159                 return 1;
 160 #endif
 161
 162         *diff = 0;
 163
 164         /* Only useful for established sessions */
 165         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 166                 return 1;
 167
 168         /* Linear packets are much easier to deal with. */
 169         if (!skb_make_writable(skb, skb->len))
 170                 return 0;
 171
 172         if (cp->app_data == &ip_vs_ftp_pasv) {
 173                 iph = ip_hdr(skb);
 174                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 175                 data = (char *)th + (th->doff << 2);
 176                 data_limit = skb_tail_pointer(skb);
 177
 178                 if (ip_vs_ftp_get_addrport(data, data_limit,
 179                                            SERVER_STRING,
 180                                            sizeof(SERVER_STRING)-1, ')',
 181                                            &from.ip, &port,
 182                                            &start, &end) != 1)
 183                         return 1;
 184
 185                 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
 186                           &from.ip, ntohs(port), &cp->caddr.ip, 0);
 187
 188                 /*
 189                  * Now update or create an connection entry for it
 190                  */
 191                 n_cp = ip_vs_conn_out_get(AF_INET, iph->protocol, &from, port,
 192                                           &cp->caddr, 0);
 193                 if (!n_cp) {
 194                         n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
 195                                               &cp->caddr, 0,
 196                                               &cp->vaddr, port,
 197                                               &from, port,
 198                                               IP_VS_CONN_F_NO_CPORT,
 199                                               cp->dest);
 200                         if (!n_cp)
 201                                 return 0;
 202
 203                         /* add its controller */
 204                         ip_vs_control_add(n_cp, cp);
 205                 }
 206
 207                 /*
 208                  * Replace the old passive address with the new one
 209                  */
 210                 from.ip = n_cp->vaddr.ip;
 211                 port = n_cp->vport;
 212                 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 213                          ((unsigned char *)&from.ip)[0],
 214                          ((unsigned char *)&from.ip)[1],
 215                          ((unsigned char *)&from.ip)[2],
 216                          ((unsigned char *)&from.ip)[3],
 217                          ntohs(port) >> 8,
 218                          ntohs(port) & 0xFF);
 219
 220                 buf_len = strlen(buf);
 221
 222                 /*
 223                  * Calculate required delta-offset to keep TCP happy
 224                  */
 225                 *diff = buf_len - (end-start);
 226
 227                 if (*diff == 0) {
 228                         /* simply replace it with new passive address */
 229                         memcpy(start, buf, buf_len);
 230                         ret = 1;
 231                 } else {
 232                         ret = !ip_vs_skb_replace(skb, GFP_ATOMIC, start,
 233                                           end-start, buf, buf_len);
 234                 }
 235
 236                 cp->app_data = NULL;
 237                 ip_vs_tcp_conn_listen(n_cp);
 238                 ip_vs_conn_put(n_cp);
 239                 return ret;
 240         }
 241         return 1;
 242 }
 243
 244
 245 /*
 246  * Look at incoming ftp packets to catch the PASV/PORT command
 247  * (outside-to-inside).
 248  *
 249  * The incoming packet having the PORT command should be something like
 250  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 251  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 252  * In this case, we create a connection entry using the client address and
 253  * port, so that the active ftp data connection from the server can reach
 254  * the client.
 255  */
 256 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 257                         struct sk_buff *skb, int *diff)
 258 {
 259         struct iphdr *iph;
 260         struct tcphdr *th;
 261         char *data, *data_start, *data_limit;
 262         char *start, *end;
 263         union nf_inet_addr to;
 264         __be16 port;
 265         struct ip_vs_conn *n_cp;
 266
 267 #ifdef CONFIG_IP_VS_IPV6
 268         /* This application helper doesn't work with IPv6 yet,
 269          * so turn this into a no-op for IPv6 packets
 270          */
 271         if (cp->af == AF_INET6)
 272                 return 1;
 273 #endif
 274
 275         /* no diff required for incoming packets */
 276         *diff = 0;
 277
 278         /* Only useful for established sessions */
 279         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 280                 return 1;
 281
 282         /* Linear packets are much easier to deal with. */
 283         if (!skb_make_writable(skb, skb->len))
 284                 return 0;
 285
 286         /*
 287          * Detecting whether it is passive
 288          */
 289         iph = ip_hdr(skb);
 290         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 291
 292         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 293            the length of the header in 32-bit multiples, it is accurate
 294            to calculate data address by th+HLEN*4 */
 295         data = data_start = (char *)th + (th->doff << 2);
 296         data_limit = skb_tail_pointer(skb);
 297
 298         while (data <= data_limit - 6) {
 299                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 300                         /* Passive mode on */
 301                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 302                                   data - data_start,
 303                                   data_limit - data_start);
 304                         cp->app_data = &ip_vs_ftp_pasv;
 305                         return 1;
 306                 }
 307                 data++;
 308         }
 309
 310         /*
 311          * To support virtual FTP server, the scenerio is as follows:
 312          *       FTP client ----> Load Balancer ----> FTP server
 313          * First detect the port number in the application data,
 314          * then create a new connection entry for the coming data
 315          * connection.
 316          */
 317         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 318                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 319                                    '\r', &to.ip, &port,
 320                                    &start, &end) != 1)
 321                 return 1;
 322
 323         IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
 324
 325         /* Passive mode off */
 326         cp->app_data = NULL;
 327
 328         /*
 329          * Now update or create a connection entry for it
 330          */
 331         IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
 332                   ip_vs_proto_name(iph->protocol),
 333                   &to.ip, ntohs(port), &cp->vaddr.ip, 0);
 334
 335         n_cp = ip_vs_conn_in_get(AF_INET, iph->protocol,
 336                                  &to, port,
 337                                  &cp->vaddr, htons(ntohs(cp->vport)-1));
 338         if (!n_cp) {
 339                 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
 340                                       &to, port,
 341                                       &cp->vaddr, htons(ntohs(cp->vport)-1),
 342                                       &cp->daddr, htons(ntohs(cp->dport)-1),
 343                                       0,
 344                                       cp->dest);
 345                 if (!n_cp)
 346                         return 0;
 347
 348                 /* add its controller */
 349                 ip_vs_control_add(n_cp, cp);
 350         }
 351
 352         /*
 353          *      Move tunnel to listen state
 354          */
 355         ip_vs_tcp_conn_listen(n_cp);
 356         ip_vs_conn_put(n_cp);
 357
 358         return 1;
 359 }
 360
 361
 362 static struct ip_vs_app ip_vs_ftp = {
 363         .name =         "ftp",
 364         .type =         IP_VS_APP_TYPE_FTP,
 365         .protocol =     IPPROTO_TCP,
 366         .module =       THIS_MODULE,
 367         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 368         .init_conn =    ip_vs_ftp_init_conn,
 369         .done_conn =    ip_vs_ftp_done_conn,
 370         .bind_conn =    NULL,
 371         .unbind_conn =  NULL,
 372         .pkt_out =      ip_vs_ftp_out,
 373         .pkt_in =       ip_vs_ftp_in,
 374 };
 375
 376
 377 /*
 378  *      ip_vs_ftp initialization
 379  */
 380 static int __init ip_vs_ftp_init(void)
 381 {
 382         int i, ret;
 383         struct ip_vs_app *app = &ip_vs_ftp;
 384
 385         ret = register_ip_vs_app(app);
 386         if (ret)
 387                 return ret;
 388
 389         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 390                 if (!ports[i])
 391                         continue;
 392                 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
 393                 if (ret)
 394                         break;
 395                 pr_info("%s: loaded support on port[%d] = %d\n",
 396                         app->name, i, ports[i]);
 397         }
 398
 399         if (ret)
 400                 unregister_ip_vs_app(app);
 401
 402         return ret;
 403 }
 404
 405
 406 /*
 407  *      ip_vs_ftp finish.
 408  */
 409 static void __exit ip_vs_ftp_exit(void)
 410 {
 411         unregister_ip_vs_app(&ip_vs_ftp);
 412 }
 413
 414
 415 module_init(ip_vs_ftp_init);
 416 module_exit(ip_vs_ftp_exit);
 417 MODULE_LICENSE("GPL");