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