LXR linux/net/netfilter/ipvs/ip_vs

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * ip_vs_ftp.c: IPVS ftp application module
   4 *
   5 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   6 *
   7 * Changes:
   8 *
   9 * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
  10 * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
  11 *
  12 *              IP_MASQ_FTP ftp masquerading module
  13 *
  14 * Version:     @(#)ip_masq_ftp.c 0.04   02/05/96
  15 *
  16 * Author:      Wouter Gadeyne
  17 */
  18
  19#define KMSG_COMPONENT "IPVS"
  20#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  21
  22#include <linux/module.h>
  23#include <linux/moduleparam.h>
  24#include <linux/kernel.h>
  25#include <linux/skbuff.h>
  26#include <linux/ctype.h>
  27#include <linux/inet.h>
  28#include <linux/in.h>
  29#include <linux/ip.h>
  30#include <linux/netfilter.h>
  31#include <net/netfilter/nf_conntrack.h>
  32#include <net/netfilter/nf_conntrack_expect.h>
  33#include <net/netfilter/nf_nat.h>
  34#include <net/netfilter/nf_nat_helper.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_PASV "227 "
  44#define CLIENT_STRING_PORT "PORT"
  45#define SERVER_STRING_EPSV "229 "
  46#define CLIENT_STRING_EPRT "EPRT"
  47
  48enum {
  49        IP_VS_FTP_ACTIVE = 0,
  50        IP_VS_FTP_PORT = 0,
  51        IP_VS_FTP_PASV,
  52        IP_VS_FTP_EPRT,
  53        IP_VS_FTP_EPSV,
  54};
  55
  56/*
  57 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  58 * First port is set to the default port.
  59 */
  60static unsigned int ports_count = 1;
  61static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  62module_param_array(ports, ushort, &ports_count, 0444);
  63MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  64
  65
  66static char *ip_vs_ftp_data_ptr(struct sk_buff *skb, struct ip_vs_iphdr *ipvsh)
  67{
  68        struct tcphdr *th = (struct tcphdr *)((char *)skb->data + ipvsh->len);
  69
  70        if ((th->doff << 2) < sizeof(struct tcphdr))
  71                return NULL;
  72
  73        return (char *)th + (th->doff << 2);
  74}
  75
  76static int
  77ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  78{
  79        /* We use connection tracking for the command connection */
  80        cp->flags |= IP_VS_CONN_F_NFCT;
  81        return 0;
  82}
  83
  84
  85static int
  86ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  87{
  88        return 0;
  89}
  90
  91
  92/* Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  93 * with the "pattern". <addr,port> is in network order.
  94 * Parse extended format depending on ext. In this case addr can be pre-set.
  95 */
  96static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  97                                  const char *pattern, size_t plen,
  98                                  char skip, bool ext, int mode,
  99                                  union nf_inet_addr *addr, __be16 *port,
 100                                  __u16 af, char **start, char **end)
 101{
 102        char *s, c;
 103        unsigned char p[6];
 104        char edelim;
 105        __u16 hport;
 106        int i = 0;
 107
 108        if (data_limit - data < plen) {
 109                /* check if there is partial match */
 110                if (strncasecmp(data, pattern, data_limit - data) == 0)
 111                        return -1;
 112                else
 113                        return 0;
 114        }
 115
 116        if (strncasecmp(data, pattern, plen) != 0) {
 117                return 0;
 118        }
 119        s = data + plen;
 120        if (skip) {
 121                bool found = false;
 122
 123                for (;; s++) {
 124                        if (s == data_limit)
 125                                return -1;
 126                        if (!found) {
 127                                /* "(" is optional for non-extended format,
 128                                 * so catch the start of IPv4 address
 129                                 */
 130                                if (!ext && isdigit(*s))
 131                                        break;
 132                                if (*s == skip)
 133                                        found = true;
 134                        } else if (*s != skip) {
 135                                break;
 136                        }
 137                }
 138        }
 139        /* Old IPv4-only format? */
 140        if (!ext) {
 141                p[0] = 0;
 142                for (data = s; ; data++) {
 143                        if (data == data_limit)
 144                                return -1;
 145                        c = *data;
 146                        if (isdigit(c)) {
 147                                p[i] = p[i]*10 + c - '0';
 148                        } else if (c == ',' && i < 5) {
 149                                i++;
 150                                p[i] = 0;
 151                        } else {
 152                                /* unexpected character or terminator */
 153                                break;
 154                        }
 155                }
 156
 157                if (i != 5)
 158                        return -1;
 159
 160                *start = s;
 161                *end = data;
 162                addr->ip = get_unaligned((__be32 *) p);
 163                *port = get_unaligned((__be16 *) (p + 4));
 164                return 1;
 165        }
 166        if (s == data_limit)
 167                return -1;
 168        *start = s;
 169        edelim = *s++;
 170        if (edelim < 33 || edelim > 126)
 171                return -1;
 172        if (s == data_limit)
 173                return -1;
 174        if (*s == edelim) {
 175                /* Address family is usually missing for EPSV response */
 176                if (mode != IP_VS_FTP_EPSV)
 177                        return -1;
 178                s++;
 179                if (s == data_limit)
 180                        return -1;
 181                /* Then address should be missing too */
 182                if (*s != edelim)
 183                        return -1;
 184                /* Caller can pre-set addr, if needed */
 185                s++;
 186        } else {
 187                const char *ep;
 188
 189                /* We allow address only from same family */
 190                if (af == AF_INET6 && *s != '2')
 191                        return -1;
 192                if (af == AF_INET && *s != '1')
 193                        return -1;
 194                s++;
 195                if (s == data_limit)
 196                        return -1;
 197                if (*s != edelim)
 198                        return -1;
 199                s++;
 200                if (s == data_limit)
 201                        return -1;
 202                if (af == AF_INET6) {
 203                        if (in6_pton(s, data_limit - s, (u8 *)addr, edelim,
 204                                     &ep) <= 0)
 205                                return -1;
 206                } else {
 207                        if (in4_pton(s, data_limit - s, (u8 *)addr, edelim,
 208                                     &ep) <= 0)
 209                                return -1;
 210                }
 211                s = (char *) ep;
 212                if (s == data_limit)
 213                        return -1;
 214                if (*s != edelim)
 215                        return -1;
 216                s++;
 217        }
 218        for (hport = 0; ; s++)
 219        {
 220                if (s == data_limit)
 221                        return -1;
 222                if (!isdigit(*s))
 223                        break;
 224                hport = hport * 10 + *s - '0';
 225        }
 226        if (s == data_limit || !hport || *s != edelim)
 227                return -1;
 228        s++;
 229        *end = s;
 230        *port = htons(hport);
 231        return 1;
 232}
 233
 234/* Look at outgoing ftp packets to catch the response to a PASV/EPSV command
 235 * from the server (inside-to-outside).
 236 * When we see one, we build a connection entry with the client address,
 237 * client port 0 (unknown at the moment), the server address and the
 238 * server port.  Mark the current connection entry as a control channel
 239 * of the new entry. All this work is just to make the data connection
 240 * can be scheduled to the right server later.
 241 *
 242 * The outgoing packet should be something like
 243 *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 244 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 245 * The extended format for EPSV response provides usually only port:
 246 *   "229 Entering Extended Passive Mode (|||ppp|)"
 247 */
 248static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 249                         struct sk_buff *skb, int *diff,
 250                         struct ip_vs_iphdr *ipvsh)
 251{
 252        char *data, *data_limit;
 253        char *start, *end;
 254        union nf_inet_addr from;
 255        __be16 port;
 256        struct ip_vs_conn *n_cp;
 257        char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 258        unsigned int buf_len;
 259        int ret = 0;
 260        enum ip_conntrack_info ctinfo;
 261        struct nf_conn *ct;
 262
 263        *diff = 0;
 264
 265        /* Only useful for established sessions */
 266        if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 267                return 1;
 268
 269        /* Linear packets are much easier to deal with. */
 270        if (skb_ensure_writable(skb, skb->len))
 271                return 0;
 272
 273        if (cp->app_data == (void *) IP_VS_FTP_PASV) {
 274                data = ip_vs_ftp_data_ptr(skb, ipvsh);
 275                data_limit = skb_tail_pointer(skb);
 276
 277                if (!data || data >= data_limit)
 278                        return 1;
 279
 280                if (ip_vs_ftp_get_addrport(data, data_limit,
 281                                           SERVER_STRING_PASV,
 282                                           sizeof(SERVER_STRING_PASV)-1,
 283                                           '(', false, IP_VS_FTP_PASV,
 284                                           &from, &port, cp->af,
 285                                           &start, &end) != 1)
 286                        return 1;
 287
 288                IP_VS_DBG(7, "PASV response (%pI4:%u) -> %pI4:%u detected\n",
 289                          &from.ip, ntohs(port), &cp->caddr.ip, 0);
 290        } else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
 291                data = ip_vs_ftp_data_ptr(skb, ipvsh);
 292                data_limit = skb_tail_pointer(skb);
 293
 294                if (!data || data >= data_limit)
 295                        return 1;
 296
 297                /* Usually, data address is not specified but
 298                 * we support different address, so pre-set it.
 299                 */
 300                from = cp->daddr;
 301                if (ip_vs_ftp_get_addrport(data, data_limit,
 302                                           SERVER_STRING_EPSV,
 303                                           sizeof(SERVER_STRING_EPSV)-1,
 304                                           '(', true, IP_VS_FTP_EPSV,
 305                                           &from, &port, cp->af,
 306                                           &start, &end) != 1)
 307                        return 1;
 308
 309                IP_VS_DBG_BUF(7, "EPSV response (%s:%u) -> %s:%u detected\n",
 310                              IP_VS_DBG_ADDR(cp->af, &from), ntohs(port),
 311                              IP_VS_DBG_ADDR(cp->af, &cp->caddr), 0);
 312        } else {
 313                return 1;
 314        }
 315
 316        /* Now update or create a connection entry for it */
 317        {
 318                struct ip_vs_conn_param p;
 319
 320                ip_vs_conn_fill_param(cp->ipvs, cp->af,
 321                                      ipvsh->protocol, &from, port,
 322                                      &cp->caddr, 0, &p);
 323                n_cp = ip_vs_conn_out_get(&p);
 324        }
 325        if (!n_cp) {
 326                struct ip_vs_conn_param p;
 327
 328                ip_vs_conn_fill_param(cp->ipvs,
 329                                      cp->af, ipvsh->protocol, &cp->caddr,
 330                                      0, &cp->vaddr, port, &p);
 331                n_cp = ip_vs_conn_new(&p, cp->af, &from, port,
 332                                      IP_VS_CONN_F_NO_CPORT |
 333                                      IP_VS_CONN_F_NFCT,
 334                                      cp->dest, skb->mark);
 335                if (!n_cp)
 336                        return 0;
 337
 338                /* add its controller */
 339                ip_vs_control_add(n_cp, cp);
 340        }
 341
 342        /* Replace the old passive address with the new one */
 343        if (cp->app_data == (void *) IP_VS_FTP_PASV) {
 344                from.ip = n_cp->vaddr.ip;
 345                port = n_cp->vport;
 346                snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 347                         ((unsigned char *)&from.ip)[0],
 348                         ((unsigned char *)&from.ip)[1],
 349                         ((unsigned char *)&from.ip)[2],
 350                         ((unsigned char *)&from.ip)[3],
 351                         ntohs(port) >> 8,
 352                         ntohs(port) & 0xFF);
 353        } else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
 354                from = n_cp->vaddr;
 355                port = n_cp->vport;
 356                /* Only port, client will use VIP for the data connection */
 357                snprintf(buf, sizeof(buf), "|||%u|",
 358                         ntohs(port));
 359        } else {
 360                *buf = 0;
 361        }
 362        buf_len = strlen(buf);
 363
 364        ct = nf_ct_get(skb, &ctinfo);
 365        if (ct) {
 366                bool mangled;
 367
 368                /* If mangling fails this function will return 0
 369                 * which will cause the packet to be dropped.
 370                 * Mangling can only fail under memory pressure,
 371                 * hopefully it will succeed on the retransmitted
 372                 * packet.
 373                 */
 374                mangled = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 375                                                   ipvsh->len,
 376                                                   start - data,
 377                                                   end - start,
 378                                                   buf, buf_len);
 379                if (mangled) {
 380                        ip_vs_nfct_expect_related(skb, ct, n_cp,
 381                                                  ipvsh->protocol, 0, 0);
 382                        if (skb->ip_summed == CHECKSUM_COMPLETE)
 383                                skb->ip_summed = CHECKSUM_UNNECESSARY;
 384                        /* csum is updated */
 385                        ret = 1;
 386                }
 387        }
 388
 389        /* Not setting 'diff' is intentional, otherwise the sequence
 390         * would be adjusted twice.
 391         */
 392
 393        cp->app_data = (void *) IP_VS_FTP_ACTIVE;
 394        ip_vs_tcp_conn_listen(n_cp);
 395        ip_vs_conn_put(n_cp);
 396        return ret;
 397}
 398
 399
 400/* Look at incoming ftp packets to catch the PASV/PORT/EPRT/EPSV command
 401 * (outside-to-inside).
 402 *
 403 * The incoming packet having the PORT command should be something like
 404 *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 405 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 406 * In this case, we create a connection entry using the client address and
 407 * port, so that the active ftp data connection from the server can reach
 408 * the client.
 409 * Extended format:
 410 *      "EPSV\r\n" when client requests server address from same family
 411 *      "EPSV 1\r\n" when client requests IPv4 server address
 412 *      "EPSV 2\r\n" when client requests IPv6 server address
 413 *      "EPSV ALL\r\n" - not supported
 414 *      EPRT with specified delimiter (ASCII 33..126), "|" by default:
 415 *      "EPRT |1|IPv4ADDR|PORT|\r\n" when client provides IPv4 addrport
 416 *      "EPRT |2|IPv6ADDR|PORT|\r\n" when client provides IPv6 addrport
 417 */
 418static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 419                        struct sk_buff *skb, int *diff,
 420                        struct ip_vs_iphdr *ipvsh)
 421{
 422        char *data, *data_start, *data_limit;
 423        char *start, *end;
 424        union nf_inet_addr to;
 425        __be16 port;
 426        struct ip_vs_conn *n_cp;
 427
 428        /* no diff required for incoming packets */
 429        *diff = 0;
 430
 431        /* Only useful for established sessions */
 432        if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 433                return 1;
 434
 435        /* Linear packets are much easier to deal with. */
 436        if (skb_ensure_writable(skb, skb->len))
 437                return 0;
 438
 439        data = data_start = ip_vs_ftp_data_ptr(skb, ipvsh);
 440        data_limit = skb_tail_pointer(skb);
 441        if (!data || data >= data_limit)
 442                return 1;
 443
 444        while (data <= data_limit - 6) {
 445                if (cp->af == AF_INET &&
 446                    strncasecmp(data, "PASV\r\n", 6) == 0) {
 447                        /* Passive mode on */
 448                        IP_VS_DBG(7, "got PASV at %td of %td\n",
 449                                  data - data_start,
 450                                  data_limit - data_start);
 451                        cp->app_data = (void *) IP_VS_FTP_PASV;
 452                        return 1;
 453                }
 454
 455                /* EPSV or EPSV<space><net-prt> */
 456                if (strncasecmp(data, "EPSV", 4) == 0 &&
 457                    (data[4] == ' ' || data[4] == '\r')) {
 458                        if (data[4] == ' ') {
 459                                char proto = data[5];
 460
 461                                if (data > data_limit - 7 || data[6] != '\r')
 462                                        return 1;
 463
 464#ifdef CONFIG_IP_VS_IPV6
 465                                if (cp->af == AF_INET6 && proto == '2') {
 466                                } else
 467#endif
 468                                if (cp->af == AF_INET && proto == '1') {
 469                                } else {
 470                                        return 1;
 471                                }
 472                        }
 473                        /* Extended Passive mode on */
 474                        IP_VS_DBG(7, "got EPSV at %td of %td\n",
 475                                  data - data_start,
 476                                  data_limit - data_start);
 477                        cp->app_data = (void *) IP_VS_FTP_EPSV;
 478                        return 1;
 479                }
 480
 481                data++;
 482        }
 483
 484        /*
 485         * To support virtual FTP server, the scenerio is as follows:
 486         *       FTP client ----> Load Balancer ----> FTP server
 487         * First detect the port number in the application data,
 488         * then create a new connection entry for the coming data
 489         * connection.
 490         */
 491        if (cp->af == AF_INET &&
 492            ip_vs_ftp_get_addrport(data_start, data_limit,
 493                                   CLIENT_STRING_PORT,
 494                                   sizeof(CLIENT_STRING_PORT)-1,
 495                                   ' ', false, IP_VS_FTP_PORT,
 496                                   &to, &port, cp->af,
 497                                   &start, &end) == 1) {
 498
 499                IP_VS_DBG(7, "PORT %pI4:%u detected\n", &to.ip, ntohs(port));
 500
 501                /* Now update or create a connection entry for it */
 502                IP_VS_DBG(7, "protocol %s %pI4:%u %pI4:%u\n",
 503                          ip_vs_proto_name(ipvsh->protocol),
 504                          &to.ip, ntohs(port), &cp->vaddr.ip,
 505                          ntohs(cp->vport)-1);
 506        } else if (ip_vs_ftp_get_addrport(data_start, data_limit,
 507                                          CLIENT_STRING_EPRT,
 508                                          sizeof(CLIENT_STRING_EPRT)-1,
 509                                          ' ', true, IP_VS_FTP_EPRT,
 510                                          &to, &port, cp->af,
 511                                          &start, &end) == 1) {
 512
 513                IP_VS_DBG_BUF(7, "EPRT %s:%u detected\n",
 514                              IP_VS_DBG_ADDR(cp->af, &to), ntohs(port));
 515
 516                /* Now update or create a connection entry for it */
 517                IP_VS_DBG_BUF(7, "protocol %s %s:%u %s:%u\n",
 518                              ip_vs_proto_name(ipvsh->protocol),
 519                              IP_VS_DBG_ADDR(cp->af, &to), ntohs(port),
 520                              IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
 521                              ntohs(cp->vport)-1);
 522        } else {
 523                return 1;
 524        }
 525
 526        /* Passive mode off */
 527        cp->app_data = (void *) IP_VS_FTP_ACTIVE;
 528
 529        {
 530                struct ip_vs_conn_param p;
 531                ip_vs_conn_fill_param(cp->ipvs, cp->af,
 532                                      ipvsh->protocol, &to, port, &cp->vaddr,
 533                                      htons(ntohs(cp->vport)-1), &p);
 534                n_cp = ip_vs_conn_in_get(&p);
 535                if (!n_cp) {
 536                        n_cp = ip_vs_conn_new(&p, cp->af, &cp->daddr,
 537                                              htons(ntohs(cp->dport)-1),
 538                                              IP_VS_CONN_F_NFCT, cp->dest,
 539                                              skb->mark);
 540                        if (!n_cp)
 541                                return 0;
 542
 543                        /* add its controller */
 544                        ip_vs_control_add(n_cp, cp);
 545                }
 546        }
 547
 548        /*
 549         *      Move tunnel to listen state
 550         */
 551        ip_vs_tcp_conn_listen(n_cp);
 552        ip_vs_conn_put(n_cp);
 553
 554        return 1;
 555}
 556
 557
 558static struct ip_vs_app ip_vs_ftp = {
 559        .name =         "ftp",
 560        .type =         IP_VS_APP_TYPE_FTP,
 561        .protocol =     IPPROTO_TCP,
 562        .module =       THIS_MODULE,
 563        .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 564        .init_conn =    ip_vs_ftp_init_conn,
 565        .done_conn =    ip_vs_ftp_done_conn,
 566        .bind_conn =    NULL,
 567        .unbind_conn =  NULL,
 568        .pkt_out =      ip_vs_ftp_out,
 569        .pkt_in =       ip_vs_ftp_in,
 570};
 571
 572/*
 573 *      per netns ip_vs_ftp initialization
 574 */
 575static int __net_init __ip_vs_ftp_init(struct net *net)
 576{
 577        int i, ret;
 578        struct ip_vs_app *app;
 579        struct netns_ipvs *ipvs = net_ipvs(net);
 580
 581        if (!ipvs)
 582                return -ENOENT;
 583
 584        app = register_ip_vs_app(ipvs, &ip_vs_ftp);
 585        if (IS_ERR(app))
 586                return PTR_ERR(app);
 587
 588        for (i = 0; i < ports_count; i++) {
 589                if (!ports[i])
 590                        continue;
 591                ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
 592                if (ret)
 593                        goto err_unreg;
 594        }
 595        return 0;
 596
 597err_unreg:
 598        unregister_ip_vs_app(ipvs, &ip_vs_ftp);
 599        return ret;
 600}
 601/*
 602 *      netns exit
 603 */
 604static void __ip_vs_ftp_exit(struct net *net)
 605{
 606        struct netns_ipvs *ipvs = net_ipvs(net);
 607
 608        if (!ipvs)
 609                return;
 610
 611        unregister_ip_vs_app(ipvs, &ip_vs_ftp);
 612}
 613
 614static struct pernet_operations ip_vs_ftp_ops = {
 615        .init = __ip_vs_ftp_init,
 616        .exit = __ip_vs_ftp_exit,
 617};
 618
 619static int __init ip_vs_ftp_init(void)
 620{
 621        /* rcu_barrier() is called by netns on error */
 622        return register_pernet_subsys(&ip_vs_ftp_ops);
 623}
 624
 625/*
 626 *      ip_vs_ftp finish.
 627 */
 628static void __exit ip_vs_ftp_exit(void)
 629{
 630        unregister_pernet_subsys(&ip_vs_ftp_ops);
 631        /* rcu_barrier() is called by netns */
 632}
 633
 634
 635module_init(ip_vs_ftp_init);
 636module_exit(ip_vs_ftp_exit);
 637MODULE_LICENSE("GPL");
 638