net/ipv4/ip_options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              The options processing module for ip.c
   8  *
   9  * Authors:     A.N.Kuznetsov
  10  *
  11  */
  12
  13 #define pr_fmt(fmt) "IPv4: " fmt
  14
  15 #include <linux/capability.h>
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include <linux/types.h>
  19 #include <linux/uaccess.h>
  20 #include <asm/unaligned.h>
  21 #include <linux/skbuff.h>
  22 #include <linux/ip.h>
  23 #include <linux/icmp.h>
  24 #include <linux/netdevice.h>
  25 #include <linux/rtnetlink.h>
  26 #include <net/sock.h>
  27 #include <net/ip.h>
  28 #include <net/icmp.h>
  29 #include <net/route.h>
  30 #include <net/cipso_ipv4.h>
  31 #include <net/ip_fib.h>
  32
  33 /*
  34  * Write options to IP header, record destination address to
  35  * source route option, address of outgoing interface
  36  * (we should already know it, so that this  function is allowed be
  37  * called only after routing decision) and timestamp,
  38  * if we originate this datagram.
  39  *
  40  * daddr is real destination address, next hop is recorded in IP header.
  41  * saddr is address of outgoing interface.
  42  */
  43
  44 void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
  45                       __be32 daddr, struct rtable *rt)
  46 {
  47         unsigned char *iph = skb_network_header(skb);
  48
  49         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  50         memcpy(iph + sizeof(struct iphdr), opt->__data, opt->optlen);
  51         opt = &(IPCB(skb)->opt);
  52
  53         if (opt->srr)
  54                 memcpy(iph + opt->srr + iph[opt->srr + 1] - 4, &daddr, 4);
  55
  56         if (opt->rr_needaddr)
  57                 ip_rt_get_source(iph + opt->rr + iph[opt->rr + 2] - 5, skb, rt);
  58         if (opt->ts_needaddr)
  59                 ip_rt_get_source(iph + opt->ts + iph[opt->ts + 2] - 9, skb, rt);
  60         if (opt->ts_needtime) {
  61                 __be32 midtime;
  62
  63                 midtime = inet_current_timestamp();
  64                 memcpy(iph + opt->ts + iph[opt->ts + 2] - 5, &midtime, 4);
  65         }
  66 }
  67
  68 /*
  69  * Provided (sopt, skb) points to received options,
  70  * build in dopt compiled option set appropriate for answering.
  71  * i.e. invert SRR option, copy anothers,
  72  * and grab room in RR/TS options.
  73  *
  74  * NOTE: dopt cannot point to skb.
  75  */
  76
  77 int __ip_options_echo(struct net *net, struct ip_options *dopt,
  78                       struct sk_buff *skb, const struct ip_options *sopt)
  79 {
  80         unsigned char *sptr, *dptr;
  81         int soffset, doffset;
  82         int     optlen;
  83
  84         memset(dopt, 0, sizeof(struct ip_options));
  85
  86         if (sopt->optlen == 0)
  87                 return 0;
  88
  89         sptr = skb_network_header(skb);
  90         dptr = dopt->__data;
  91
  92         if (sopt->rr) {
  93                 optlen  = sptr[sopt->rr+1];
  94                 soffset = sptr[sopt->rr+2];
  95                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
  96                 memcpy(dptr, sptr+sopt->rr, optlen);
  97                 if (sopt->rr_needaddr && soffset <= optlen) {
  98                         if (soffset + 3 > optlen)
  99                                 return -EINVAL;
 100                         dptr[2] = soffset + 4;
 101                         dopt->rr_needaddr = 1;
 102                 }
 103                 dptr += optlen;
 104                 dopt->optlen += optlen;
 105         }
 106         if (sopt->ts) {
 107                 optlen = sptr[sopt->ts+1];
 108                 soffset = sptr[sopt->ts+2];
 109                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 110                 memcpy(dptr, sptr+sopt->ts, optlen);
 111                 if (soffset <= optlen) {
 112                         if (sopt->ts_needaddr) {
 113                                 if (soffset + 3 > optlen)
 114                                         return -EINVAL;
 115                                 dopt->ts_needaddr = 1;
 116                                 soffset += 4;
 117                         }
 118                         if (sopt->ts_needtime) {
 119                                 if (soffset + 3 > optlen)
 120                                         return -EINVAL;
 121                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 122                                         dopt->ts_needtime = 1;
 123                                         soffset += 4;
 124                                 } else {
 125                                         dopt->ts_needtime = 0;
 126
 127                                         if (soffset + 7 <= optlen) {
 128                                                 __be32 addr;
 129
 130                                                 memcpy(&addr, dptr+soffset-1, 4);
 131                                                 if (inet_addr_type(net, addr) != RTN_UNICAST) {
 132                                                         dopt->ts_needtime = 1;
 133                                                         soffset += 8;
 134                                                 }
 135                                         }
 136                                 }
 137                         }
 138                         dptr[2] = soffset;
 139                 }
 140                 dptr += optlen;
 141                 dopt->optlen += optlen;
 142         }
 143         if (sopt->srr) {
 144                 unsigned char *start = sptr+sopt->srr;
 145                 __be32 faddr;
 146
 147                 optlen  = start[1];
 148                 soffset = start[2];
 149                 doffset = 0;
 150                 if (soffset > optlen)
 151                         soffset = optlen + 1;
 152                 soffset -= 4;
 153                 if (soffset > 3) {
 154                         memcpy(&faddr, &start[soffset-1], 4);
 155                         for (soffset -= 4, doffset = 4; soffset > 3; soffset -= 4, doffset += 4)
 156                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 157                         /*
 158                          * RFC1812 requires to fix illegal source routes.
 159                          */
 160                         if (memcmp(&ip_hdr(skb)->saddr,
 161                                    &start[soffset + 3], 4) == 0)
 162                                 doffset -= 4;
 163                 }
 164                 if (doffset > 3) {
 165                         dopt->faddr = faddr;
 166                         dptr[0] = start[0];
 167                         dptr[1] = doffset+3;
 168                         dptr[2] = 4;
 169                         dptr += doffset+3;
 170                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 171                         dopt->optlen += doffset+3;
 172                         dopt->is_strictroute = sopt->is_strictroute;
 173                 }
 174         }
 175         if (sopt->cipso) {
 176                 optlen  = sptr[sopt->cipso+1];
 177                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
 178                 memcpy(dptr, sptr+sopt->cipso, optlen);
 179                 dptr += optlen;
 180                 dopt->optlen += optlen;
 181         }
 182         while (dopt->optlen & 3) {
 183                 *dptr++ = IPOPT_END;
 184                 dopt->optlen++;
 185         }
 186         return 0;
 187 }
 188
 189 /*
 190  *      Options "fragmenting", just fill options not
 191  *      allowed in fragments with NOOPs.
 192  *      Simple and stupid 8), but the most efficient way.
 193  */
 194
 195 void ip_options_fragment(struct sk_buff *skb)
 196 {
 197         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
 198         struct ip_options *opt = &(IPCB(skb)->opt);
 199         int  l = opt->optlen;
 200         int  optlen;
 201
 202         while (l > 0) {
 203                 switch (*optptr) {
 204                 case IPOPT_END:
 205                         return;
 206                 case IPOPT_NOOP:
 207                         l--;
 208                         optptr++;
 209                         continue;
 210                 }
 211                 optlen = optptr[1];
 212                 if (optlen < 2 || optlen > l)
 213                   return;
 214                 if (!IPOPT_COPIED(*optptr))
 215                         memset(optptr, IPOPT_NOOP, optlen);
 216                 l -= optlen;
 217                 optptr += optlen;
 218         }
 219         opt->ts = 0;
 220         opt->rr = 0;
 221         opt->rr_needaddr = 0;
 222         opt->ts_needaddr = 0;
 223         opt->ts_needtime = 0;
 224 }
 225
 226 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
 227  * at most one time.
 228  */
 229 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
 230 {
 231         if (*spec_dst == htonl(INADDR_ANY))
 232                 *spec_dst = fib_compute_spec_dst(skb);
 233 }
 234
 235 /*
 236  * Verify options and fill pointers in struct options.
 237  * Caller should clear *opt, and set opt->data.
 238  * If opt == NULL, then skb->data should point to IP header.
 239  */
 240
 241 int __ip_options_compile(struct net *net,
 242                          struct ip_options *opt, struct sk_buff *skb,
 243                          __be32 *info)
 244 {
 245         __be32 spec_dst = htonl(INADDR_ANY);
 246         unsigned char *pp_ptr = NULL;
 247         struct rtable *rt = NULL;
 248         unsigned char *optptr;
 249         unsigned char *iph;
 250         int optlen, l;
 251
 252         if (skb) {
 253                 rt = skb_rtable(skb);
 254                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
 255         } else
 256                 optptr = opt->__data;
 257         iph = optptr - sizeof(struct iphdr);
 258
 259         for (l = opt->optlen; l > 0; ) {
 260                 switch (*optptr) {
 261                 case IPOPT_END:
 262                         for (optptr++, l--; l > 0; optptr++, l--) {
 263                                 if (*optptr != IPOPT_END) {
 264                                         *optptr = IPOPT_END;
 265                                         opt->is_changed = 1;
 266                                 }
 267                         }
 268                         goto eol;
 269                 case IPOPT_NOOP:
 270                         l--;
 271                         optptr++;
 272                         continue;
 273                 }
 274                 if (unlikely(l < 2)) {
 275                         pp_ptr = optptr;
 276                         goto error;
 277                 }
 278                 optlen = optptr[1];
 279                 if (optlen < 2 || optlen > l) {
 280                         pp_ptr = optptr;
 281                         goto error;
 282                 }
 283                 switch (*optptr) {
 284                 case IPOPT_SSRR:
 285                 case IPOPT_LSRR:
 286                         if (optlen < 3) {
 287                                 pp_ptr = optptr + 1;
 288                                 goto error;
 289                         }
 290                         if (optptr[2] < 4) {
 291                                 pp_ptr = optptr + 2;
 292                                 goto error;
 293                         }
 294                         /* NB: cf RFC-1812 5.2.4.1 */
 295                         if (opt->srr) {
 296                                 pp_ptr = optptr;
 297                                 goto error;
 298                         }
 299                         if (!skb) {
 300                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 301                                         pp_ptr = optptr + 1;
 302                                         goto error;
 303                                 }
 304                                 memcpy(&opt->faddr, &optptr[3], 4);
 305                                 if (optlen > 7)
 306                                         memmove(&optptr[3], &optptr[7], optlen-7);
 307                         }
 308                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 309                         opt->srr = optptr - iph;
 310                         break;
 311                 case IPOPT_RR:
 312                         if (opt->rr) {
 313                                 pp_ptr = optptr;
 314                                 goto error;
 315                         }
 316                         if (optlen < 3) {
 317                                 pp_ptr = optptr + 1;
 318                                 goto error;
 319                         }
 320                         if (optptr[2] < 4) {
 321                                 pp_ptr = optptr + 2;
 322                                 goto error;
 323                         }
 324                         if (optptr[2] <= optlen) {
 325                                 if (optptr[2]+3 > optlen) {
 326                                         pp_ptr = optptr + 2;
 327                                         goto error;
 328                                 }
 329                                 if (rt) {
 330                                         spec_dst_fill(&spec_dst, skb);
 331                                         memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
 332                                         opt->is_changed = 1;
 333                                 }
 334                                 optptr[2] += 4;
 335                                 opt->rr_needaddr = 1;
 336                         }
 337                         opt->rr = optptr - iph;
 338                         break;
 339                 case IPOPT_TIMESTAMP:
 340                         if (opt->ts) {
 341                                 pp_ptr = optptr;
 342                                 goto error;
 343                         }
 344                         if (optlen < 4) {
 345                                 pp_ptr = optptr + 1;
 346                                 goto error;
 347                         }
 348                         if (optptr[2] < 5) {
 349                                 pp_ptr = optptr + 2;
 350                                 goto error;
 351                         }
 352                         if (optptr[2] <= optlen) {
 353                                 unsigned char *timeptr = NULL;
 354                                 if (optptr[2]+3 > optlen) {
 355                                         pp_ptr = optptr + 2;
 356                                         goto error;
 357                                 }
 358                                 switch (optptr[3]&0xF) {
 359                                 case IPOPT_TS_TSONLY:
 360                                         if (skb)
 361                                                 timeptr = &optptr[optptr[2]-1];
 362                                         opt->ts_needtime = 1;
 363                                         optptr[2] += 4;
 364                                         break;
 365                                 case IPOPT_TS_TSANDADDR:
 366                                         if (optptr[2]+7 > optlen) {
 367                                                 pp_ptr = optptr + 2;
 368                                                 goto error;
 369                                         }
 370                                         if (rt)  {
 371                                                 spec_dst_fill(&spec_dst, skb);
 372                                                 memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
 373                                                 timeptr = &optptr[optptr[2]+3];
 374                                         }
 375                                         opt->ts_needaddr = 1;
 376                                         opt->ts_needtime = 1;
 377                                         optptr[2] += 8;
 378                                         break;
 379                                 case IPOPT_TS_PRESPEC:
 380                                         if (optptr[2]+7 > optlen) {
 381                                                 pp_ptr = optptr + 2;
 382                                                 goto error;
 383                                         }
 384                                         {
 385                                                 __be32 addr;
 386                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 387                                                 if (inet_addr_type(net, addr) == RTN_UNICAST)
 388                                                         break;
 389                                                 if (skb)
 390                                                         timeptr = &optptr[optptr[2]+3];
 391                                         }
 392                                         opt->ts_needtime = 1;
 393                                         optptr[2] += 8;
 394                                         break;
 395                                 default:
 396                                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 397                                                 pp_ptr = optptr + 3;
 398                                                 goto error;
 399                                         }
 400                                         break;
 401                                 }
 402                                 if (timeptr) {
 403                                         __be32 midtime;
 404
 405                                         midtime = inet_current_timestamp();
 406                                         memcpy(timeptr, &midtime, 4);
 407                                         opt->is_changed = 1;
 408                                 }
 409                         } else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 410                                 unsigned int overflow = optptr[3]>>4;
 411                                 if (overflow == 15) {
 412                                         pp_ptr = optptr + 3;
 413                                         goto error;
 414                                 }
 415                                 if (skb) {
 416                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 417                                         opt->is_changed = 1;
 418                                 }
 419                         }
 420                         opt->ts = optptr - iph;
 421                         break;
 422                 case IPOPT_RA:
 423                         if (optlen < 4) {
 424                                 pp_ptr = optptr + 1;
 425                                 goto error;
 426                         }
 427                         if (optptr[2] == 0 && optptr[3] == 0)
 428                                 opt->router_alert = optptr - iph;
 429                         break;
 430                 case IPOPT_CIPSO:
 431                         if ((!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
 432                                 pp_ptr = optptr;
 433                                 goto error;
 434                         }
 435                         opt->cipso = optptr - iph;
 436                         if (cipso_v4_validate(skb, &optptr)) {
 437                                 pp_ptr = optptr;
 438                                 goto error;
 439                         }
 440                         break;
 441                 case IPOPT_SEC:
 442                 case IPOPT_SID:
 443                 default:
 444                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 445                                 pp_ptr = optptr;
 446                                 goto error;
 447                         }
 448                         break;
 449                 }
 450                 l -= optlen;
 451                 optptr += optlen;
 452         }
 453
 454 eol:
 455         if (!pp_ptr)
 456                 return 0;
 457
 458 error:
 459         if (info)
 460                 *info = htonl((pp_ptr-iph)<<24);
 461         return -EINVAL;
 462 }
 463 EXPORT_SYMBOL(__ip_options_compile);
 464
 465 int ip_options_compile(struct net *net,
 466                        struct ip_options *opt, struct sk_buff *skb)
 467 {
 468         int ret;
 469         __be32 info;
 470
 471         ret = __ip_options_compile(net, opt, skb, &info);
 472         if (ret != 0 && skb)
 473                 icmp_send(skb, ICMP_PARAMETERPROB, 0, info);
 474         return ret;
 475 }
 476 EXPORT_SYMBOL(ip_options_compile);
 477
 478 /*
 479  *      Undo all the changes done by ip_options_compile().
 480  */
 481
 482 void ip_options_undo(struct ip_options *opt)
 483 {
 484         if (opt->srr) {
 485                 unsigned char *optptr = opt->__data + opt->srr - sizeof(struct iphdr);
 486
 487                 memmove(optptr + 7, optptr + 3, optptr[1] - 7);
 488                 memcpy(optptr + 3, &opt->faddr, 4);
 489         }
 490         if (opt->rr_needaddr) {
 491                 unsigned char *optptr = opt->__data + opt->rr - sizeof(struct iphdr);
 492
 493                 optptr[2] -= 4;
 494                 memset(&optptr[optptr[2] - 1], 0, 4);
 495         }
 496         if (opt->ts) {
 497                 unsigned char *optptr = opt->__data + opt->ts - sizeof(struct iphdr);
 498
 499                 if (opt->ts_needtime) {
 500                         optptr[2] -= 4;
 501                         memset(&optptr[optptr[2] - 1], 0, 4);
 502                         if ((optptr[3] & 0xF) == IPOPT_TS_PRESPEC)
 503                                 optptr[2] -= 4;
 504                 }
 505                 if (opt->ts_needaddr) {
 506                         optptr[2] -= 4;
 507                         memset(&optptr[optptr[2] - 1], 0, 4);
 508                 }
 509         }
 510 }
 511
 512 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
 513                    sockptr_t data, int optlen)
 514 {
 515         struct ip_options_rcu *opt;
 516
 517         opt = kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
 518                        GFP_KERNEL);
 519         if (!opt)
 520                 return -ENOMEM;
 521         if (optlen && copy_from_sockptr(opt->opt.__data, data, optlen)) {
 522                 kfree(opt);
 523                 return -EFAULT;
 524         }
 525
 526         while (optlen & 3)
 527                 opt->opt.__data[optlen++] = IPOPT_END;
 528         opt->opt.optlen = optlen;
 529         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
 530                 kfree(opt);
 531                 return -EINVAL;
 532         }
 533         kfree(*optp);
 534         *optp = opt;
 535         return 0;
 536 }
 537
 538 void ip_forward_options(struct sk_buff *skb)
 539 {
 540         struct   ip_options *opt        = &(IPCB(skb)->opt);
 541         unsigned char *optptr;
 542         struct rtable *rt = skb_rtable(skb);
 543         unsigned char *raw = skb_network_header(skb);
 544
 545         if (opt->rr_needaddr) {
 546                 optptr = (unsigned char *)raw + opt->rr;
 547                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
 548                 opt->is_changed = 1;
 549         }
 550         if (opt->srr_is_hit) {
 551                 int srrptr, srrspace;
 552
 553                 optptr = raw + opt->srr;
 554
 555                 for ( srrptr = optptr[2], srrspace = optptr[1];
 556                      srrptr <= srrspace;
 557                      srrptr += 4
 558                      ) {
 559                         if (srrptr + 3 > srrspace)
 560                                 break;
 561                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
 562                                 break;
 563                 }
 564                 if (srrptr + 3 <= srrspace) {
 565                         opt->is_changed = 1;
 566                         ip_hdr(skb)->daddr = opt->nexthop;
 567                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
 568                         optptr[2] = srrptr+4;
 569                 } else {
 570                         net_crit_ratelimited("%s(): Argh! Destination lost!\n",
 571                                              __func__);
 572                 }
 573                 if (opt->ts_needaddr) {
 574                         optptr = raw + opt->ts;
 575                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
 576                         opt->is_changed = 1;
 577                 }
 578         }
 579         if (opt->is_changed) {
 580                 opt->is_changed = 0;
 581                 ip_send_check(ip_hdr(skb));
 582         }
 583 }
 584
 585 int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev)
 586 {
 587         struct ip_options *opt = &(IPCB(skb)->opt);
 588         int srrspace, srrptr;
 589         __be32 nexthop;
 590         struct iphdr *iph = ip_hdr(skb);
 591         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 592         struct rtable *rt = skb_rtable(skb);
 593         struct rtable *rt2;
 594         unsigned long orefdst;
 595         int err;
 596
 597         if (!rt)
 598                 return 0;
 599
 600         if (skb->pkt_type != PACKET_HOST)
 601                 return -EINVAL;
 602         if (rt->rt_type == RTN_UNICAST) {
 603                 if (!opt->is_strictroute)
 604                         return 0;
 605                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 606                 return -EINVAL;
 607         }
 608         if (rt->rt_type != RTN_LOCAL)
 609                 return -EINVAL;
 610
 611         for (srrptr = optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 612                 if (srrptr + 3 > srrspace) {
 613                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 614                         return -EINVAL;
 615                 }
 616                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 617
 618                 orefdst = skb->_skb_refdst;
 619                 skb_dst_set(skb, NULL);
 620                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, dev);
 621                 rt2 = skb_rtable(skb);
 622                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 623                         skb_dst_drop(skb);
 624                         skb->_skb_refdst = orefdst;
 625                         return -EINVAL;
 626                 }
 627                 refdst_drop(orefdst);
 628                 if (rt2->rt_type != RTN_LOCAL)
 629                         break;
 630                 /* Superfast 8) loopback forward */
 631                 iph->daddr = nexthop;
 632                 opt->is_changed = 1;
 633         }
 634         if (srrptr <= srrspace) {
 635                 opt->srr_is_hit = 1;
 636                 opt->nexthop = nexthop;
 637                 opt->is_changed = 1;
 638         }
 639         return 0;
 640 }
 641 EXPORT_SYMBOL(ip_options_rcv_srr);