root/net/netfilter/nft_exthdr.c

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DEFINITIONS

This source file includes following definitions.
  1. optlen
  2. nft_exthdr_ipv6_eval
  3. ipv4_find_option
  4. nft_exthdr_ipv4_eval
  5. nft_tcp_header_pointer
  6. nft_exthdr_tcp_eval
  7. nft_exthdr_tcp_set_eval
  8. nft_exthdr_init
  9. nft_exthdr_tcp_set_init
  10. nft_exthdr_ipv4_init
  11. nft_exthdr_dump_common
  12. nft_exthdr_dump
  13. nft_exthdr_dump_set
  14. nft_exthdr_select_ops

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   4  *
   5  * Development of this code funded by Astaro AG (http://www.astaro.com/)
   6  */
   7 
   8 #include <asm/unaligned.h>
   9 #include <linux/kernel.h>
  10 #include <linux/netlink.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/netfilter/nf_tables.h>
  13 #include <net/netfilter/nf_tables_core.h>
  14 #include <net/netfilter/nf_tables.h>
  15 #include <net/tcp.h>
  16 
  17 struct nft_exthdr {
  18         u8                      type;
  19         u8                      offset;
  20         u8                      len;
  21         u8                      op;
  22         enum nft_registers      dreg:8;
  23         enum nft_registers      sreg:8;
  24         u8                      flags;
  25 };
  26 
  27 static unsigned int optlen(const u8 *opt, unsigned int offset)
  28 {
  29         /* Beware zero-length options: make finite progress */
  30         if (opt[offset] <= TCPOPT_NOP || opt[offset + 1] == 0)
  31                 return 1;
  32         else
  33                 return opt[offset + 1];
  34 }
  35 
  36 static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
  37                                  struct nft_regs *regs,
  38                                  const struct nft_pktinfo *pkt)
  39 {
  40         struct nft_exthdr *priv = nft_expr_priv(expr);
  41         u32 *dest = &regs->data[priv->dreg];
  42         unsigned int offset = 0;
  43         int err;
  44 
  45         err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL);
  46         if (priv->flags & NFT_EXTHDR_F_PRESENT) {
  47                 *dest = (err >= 0);
  48                 return;
  49         } else if (err < 0) {
  50                 goto err;
  51         }
  52         offset += priv->offset;
  53 
  54         dest[priv->len / NFT_REG32_SIZE] = 0;
  55         if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
  56                 goto err;
  57         return;
  58 err:
  59         regs->verdict.code = NFT_BREAK;
  60 }
  61 
  62 /* find the offset to specified option.
  63  *
  64  * If target header is found, its offset is set in *offset and return option
  65  * number. Otherwise, return negative error.
  66  *
  67  * If the first fragment doesn't contain the End of Options it is considered
  68  * invalid.
  69  */
  70 static int ipv4_find_option(struct net *net, struct sk_buff *skb,
  71                             unsigned int *offset, int target)
  72 {
  73         unsigned char optbuf[sizeof(struct ip_options) + 40];
  74         struct ip_options *opt = (struct ip_options *)optbuf;
  75         struct iphdr *iph, _iph;
  76         unsigned int start;
  77         bool found = false;
  78         __be32 info;
  79         int optlen;
  80 
  81         iph = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
  82         if (!iph)
  83                 return -EBADMSG;
  84         start = sizeof(struct iphdr);
  85 
  86         optlen = iph->ihl * 4 - (int)sizeof(struct iphdr);
  87         if (optlen <= 0)
  88                 return -ENOENT;
  89 
  90         memset(opt, 0, sizeof(struct ip_options));
  91         /* Copy the options since __ip_options_compile() modifies
  92          * the options.
  93          */
  94         if (skb_copy_bits(skb, start, opt->__data, optlen))
  95                 return -EBADMSG;
  96         opt->optlen = optlen;
  97 
  98         if (__ip_options_compile(net, opt, NULL, &info))
  99                 return -EBADMSG;
 100 
 101         switch (target) {
 102         case IPOPT_SSRR:
 103         case IPOPT_LSRR:
 104                 if (!opt->srr)
 105                         break;
 106                 found = target == IPOPT_SSRR ? opt->is_strictroute :
 107                                                !opt->is_strictroute;
 108                 if (found)
 109                         *offset = opt->srr + start;
 110                 break;
 111         case IPOPT_RR:
 112                 if (!opt->rr)
 113                         break;
 114                 *offset = opt->rr + start;
 115                 found = true;
 116                 break;
 117         case IPOPT_RA:
 118                 if (!opt->router_alert)
 119                         break;
 120                 *offset = opt->router_alert + start;
 121                 found = true;
 122                 break;
 123         default:
 124                 return -EOPNOTSUPP;
 125         }
 126         return found ? target : -ENOENT;
 127 }
 128 
 129 static void nft_exthdr_ipv4_eval(const struct nft_expr *expr,
 130                                  struct nft_regs *regs,
 131                                  const struct nft_pktinfo *pkt)
 132 {
 133         struct nft_exthdr *priv = nft_expr_priv(expr);
 134         u32 *dest = &regs->data[priv->dreg];
 135         struct sk_buff *skb = pkt->skb;
 136         unsigned int offset;
 137         int err;
 138 
 139         if (skb->protocol != htons(ETH_P_IP))
 140                 goto err;
 141 
 142         err = ipv4_find_option(nft_net(pkt), skb, &offset, priv->type);
 143         if (priv->flags & NFT_EXTHDR_F_PRESENT) {
 144                 *dest = (err >= 0);
 145                 return;
 146         } else if (err < 0) {
 147                 goto err;
 148         }
 149         offset += priv->offset;
 150 
 151         dest[priv->len / NFT_REG32_SIZE] = 0;
 152         if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
 153                 goto err;
 154         return;
 155 err:
 156         regs->verdict.code = NFT_BREAK;
 157 }
 158 
 159 static void *
 160 nft_tcp_header_pointer(const struct nft_pktinfo *pkt,
 161                        unsigned int len, void *buffer, unsigned int *tcphdr_len)
 162 {
 163         struct tcphdr *tcph;
 164 
 165         if (!pkt->tprot_set || pkt->tprot != IPPROTO_TCP)
 166                 return NULL;
 167 
 168         tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, sizeof(*tcph), buffer);
 169         if (!tcph)
 170                 return NULL;
 171 
 172         *tcphdr_len = __tcp_hdrlen(tcph);
 173         if (*tcphdr_len < sizeof(*tcph) || *tcphdr_len > len)
 174                 return NULL;
 175 
 176         return skb_header_pointer(pkt->skb, pkt->xt.thoff, *tcphdr_len, buffer);
 177 }
 178 
 179 static void nft_exthdr_tcp_eval(const struct nft_expr *expr,
 180                                 struct nft_regs *regs,
 181                                 const struct nft_pktinfo *pkt)
 182 {
 183         u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
 184         struct nft_exthdr *priv = nft_expr_priv(expr);
 185         unsigned int i, optl, tcphdr_len, offset;
 186         u32 *dest = &regs->data[priv->dreg];
 187         struct tcphdr *tcph;
 188         u8 *opt;
 189 
 190         tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
 191         if (!tcph)
 192                 goto err;
 193 
 194         opt = (u8 *)tcph;
 195         for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
 196                 optl = optlen(opt, i);
 197 
 198                 if (priv->type != opt[i])
 199                         continue;
 200 
 201                 if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
 202                         goto err;
 203 
 204                 offset = i + priv->offset;
 205                 if (priv->flags & NFT_EXTHDR_F_PRESENT) {
 206                         *dest = 1;
 207                 } else {
 208                         dest[priv->len / NFT_REG32_SIZE] = 0;
 209                         memcpy(dest, opt + offset, priv->len);
 210                 }
 211 
 212                 return;
 213         }
 214 
 215 err:
 216         if (priv->flags & NFT_EXTHDR_F_PRESENT)
 217                 *dest = 0;
 218         else
 219                 regs->verdict.code = NFT_BREAK;
 220 }
 221 
 222 static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr,
 223                                     struct nft_regs *regs,
 224                                     const struct nft_pktinfo *pkt)
 225 {
 226         u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
 227         struct nft_exthdr *priv = nft_expr_priv(expr);
 228         unsigned int i, optl, tcphdr_len, offset;
 229         struct tcphdr *tcph;
 230         u8 *opt;
 231         u32 src;
 232 
 233         tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
 234         if (!tcph)
 235                 return;
 236 
 237         opt = (u8 *)tcph;
 238         for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
 239                 union {
 240                         u8 octet;
 241                         __be16 v16;
 242                         __be32 v32;
 243                 } old, new;
 244 
 245                 optl = optlen(opt, i);
 246 
 247                 if (priv->type != opt[i])
 248                         continue;
 249 
 250                 if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
 251                         return;
 252 
 253                 if (skb_ensure_writable(pkt->skb,
 254                                         pkt->xt.thoff + i + priv->len))
 255                         return;
 256 
 257                 tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff,
 258                                               &tcphdr_len);
 259                 if (!tcph)
 260                         return;
 261 
 262                 src = regs->data[priv->sreg];
 263                 offset = i + priv->offset;
 264 
 265                 switch (priv->len) {
 266                 case 2:
 267                         old.v16 = get_unaligned((u16 *)(opt + offset));
 268                         new.v16 = src;
 269 
 270                         switch (priv->type) {
 271                         case TCPOPT_MSS:
 272                                 /* increase can cause connection to stall */
 273                                 if (ntohs(old.v16) <= ntohs(new.v16))
 274                                         return;
 275                         break;
 276                         }
 277 
 278                         if (old.v16 == new.v16)
 279                                 return;
 280 
 281                         put_unaligned(new.v16, (u16*)(opt + offset));
 282                         inet_proto_csum_replace2(&tcph->check, pkt->skb,
 283                                                  old.v16, new.v16, false);
 284                         break;
 285                 case 4:
 286                         new.v32 = src;
 287                         old.v32 = get_unaligned((u32 *)(opt + offset));
 288 
 289                         if (old.v32 == new.v32)
 290                                 return;
 291 
 292                         put_unaligned(new.v32, (u32*)(opt + offset));
 293                         inet_proto_csum_replace4(&tcph->check, pkt->skb,
 294                                                  old.v32, new.v32, false);
 295                         break;
 296                 default:
 297                         WARN_ON_ONCE(1);
 298                         break;
 299                 }
 300 
 301                 return;
 302         }
 303 }
 304 
 305 static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = {
 306         [NFTA_EXTHDR_DREG]              = { .type = NLA_U32 },
 307         [NFTA_EXTHDR_TYPE]              = { .type = NLA_U8 },
 308         [NFTA_EXTHDR_OFFSET]            = { .type = NLA_U32 },
 309         [NFTA_EXTHDR_LEN]               = { .type = NLA_U32 },
 310         [NFTA_EXTHDR_FLAGS]             = { .type = NLA_U32 },
 311         [NFTA_EXTHDR_OP]                = { .type = NLA_U32 },
 312         [NFTA_EXTHDR_SREG]              = { .type = NLA_U32 },
 313 };
 314 
 315 static int nft_exthdr_init(const struct nft_ctx *ctx,
 316                            const struct nft_expr *expr,
 317                            const struct nlattr * const tb[])
 318 {
 319         struct nft_exthdr *priv = nft_expr_priv(expr);
 320         u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
 321         int err;
 322 
 323         if (!tb[NFTA_EXTHDR_DREG] ||
 324             !tb[NFTA_EXTHDR_TYPE] ||
 325             !tb[NFTA_EXTHDR_OFFSET] ||
 326             !tb[NFTA_EXTHDR_LEN])
 327                 return -EINVAL;
 328 
 329         err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
 330         if (err < 0)
 331                 return err;
 332 
 333         err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
 334         if (err < 0)
 335                 return err;
 336 
 337         if (tb[NFTA_EXTHDR_FLAGS]) {
 338                 err = nft_parse_u32_check(tb[NFTA_EXTHDR_FLAGS], U8_MAX, &flags);
 339                 if (err < 0)
 340                         return err;
 341 
 342                 if (flags & ~NFT_EXTHDR_F_PRESENT)
 343                         return -EINVAL;
 344         }
 345 
 346         if (tb[NFTA_EXTHDR_OP]) {
 347                 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
 348                 if (err < 0)
 349                         return err;
 350         }
 351 
 352         priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
 353         priv->offset = offset;
 354         priv->len    = len;
 355         priv->dreg   = nft_parse_register(tb[NFTA_EXTHDR_DREG]);
 356         priv->flags  = flags;
 357         priv->op     = op;
 358 
 359         return nft_validate_register_store(ctx, priv->dreg, NULL,
 360                                            NFT_DATA_VALUE, priv->len);
 361 }
 362 
 363 static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx,
 364                                    const struct nft_expr *expr,
 365                                    const struct nlattr * const tb[])
 366 {
 367         struct nft_exthdr *priv = nft_expr_priv(expr);
 368         u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
 369         int err;
 370 
 371         if (!tb[NFTA_EXTHDR_SREG] ||
 372             !tb[NFTA_EXTHDR_TYPE] ||
 373             !tb[NFTA_EXTHDR_OFFSET] ||
 374             !tb[NFTA_EXTHDR_LEN])
 375                 return -EINVAL;
 376 
 377         if (tb[NFTA_EXTHDR_DREG] || tb[NFTA_EXTHDR_FLAGS])
 378                 return -EINVAL;
 379 
 380         err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
 381         if (err < 0)
 382                 return err;
 383 
 384         err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
 385         if (err < 0)
 386                 return err;
 387 
 388         if (offset < 2)
 389                 return -EOPNOTSUPP;
 390 
 391         switch (len) {
 392         case 2: break;
 393         case 4: break;
 394         default:
 395                 return -EOPNOTSUPP;
 396         }
 397 
 398         err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
 399         if (err < 0)
 400                 return err;
 401 
 402         priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
 403         priv->offset = offset;
 404         priv->len    = len;
 405         priv->sreg   = nft_parse_register(tb[NFTA_EXTHDR_SREG]);
 406         priv->flags  = flags;
 407         priv->op     = op;
 408 
 409         return nft_validate_register_load(priv->sreg, priv->len);
 410 }
 411 
 412 static int nft_exthdr_ipv4_init(const struct nft_ctx *ctx,
 413                                 const struct nft_expr *expr,
 414                                 const struct nlattr * const tb[])
 415 {
 416         struct nft_exthdr *priv = nft_expr_priv(expr);
 417         int err = nft_exthdr_init(ctx, expr, tb);
 418 
 419         if (err < 0)
 420                 return err;
 421 
 422         switch (priv->type) {
 423         case IPOPT_SSRR:
 424         case IPOPT_LSRR:
 425         case IPOPT_RR:
 426         case IPOPT_RA:
 427                 break;
 428         default:
 429                 return -EOPNOTSUPP;
 430         }
 431         return 0;
 432 }
 433 
 434 static int nft_exthdr_dump_common(struct sk_buff *skb, const struct nft_exthdr *priv)
 435 {
 436         if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type))
 437                 goto nla_put_failure;
 438         if (nla_put_be32(skb, NFTA_EXTHDR_OFFSET, htonl(priv->offset)))
 439                 goto nla_put_failure;
 440         if (nla_put_be32(skb, NFTA_EXTHDR_LEN, htonl(priv->len)))
 441                 goto nla_put_failure;
 442         if (nla_put_be32(skb, NFTA_EXTHDR_FLAGS, htonl(priv->flags)))
 443                 goto nla_put_failure;
 444         if (nla_put_be32(skb, NFTA_EXTHDR_OP, htonl(priv->op)))
 445                 goto nla_put_failure;
 446         return 0;
 447 
 448 nla_put_failure:
 449         return -1;
 450 }
 451 
 452 static int nft_exthdr_dump(struct sk_buff *skb, const struct nft_expr *expr)
 453 {
 454         const struct nft_exthdr *priv = nft_expr_priv(expr);
 455 
 456         if (nft_dump_register(skb, NFTA_EXTHDR_DREG, priv->dreg))
 457                 return -1;
 458 
 459         return nft_exthdr_dump_common(skb, priv);
 460 }
 461 
 462 static int nft_exthdr_dump_set(struct sk_buff *skb, const struct nft_expr *expr)
 463 {
 464         const struct nft_exthdr *priv = nft_expr_priv(expr);
 465 
 466         if (nft_dump_register(skb, NFTA_EXTHDR_SREG, priv->sreg))
 467                 return -1;
 468 
 469         return nft_exthdr_dump_common(skb, priv);
 470 }
 471 
 472 static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
 473         .type           = &nft_exthdr_type,
 474         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 475         .eval           = nft_exthdr_ipv6_eval,
 476         .init           = nft_exthdr_init,
 477         .dump           = nft_exthdr_dump,
 478 };
 479 
 480 static const struct nft_expr_ops nft_exthdr_ipv4_ops = {
 481         .type           = &nft_exthdr_type,
 482         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 483         .eval           = nft_exthdr_ipv4_eval,
 484         .init           = nft_exthdr_ipv4_init,
 485         .dump           = nft_exthdr_dump,
 486 };
 487 
 488 static const struct nft_expr_ops nft_exthdr_tcp_ops = {
 489         .type           = &nft_exthdr_type,
 490         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 491         .eval           = nft_exthdr_tcp_eval,
 492         .init           = nft_exthdr_init,
 493         .dump           = nft_exthdr_dump,
 494 };
 495 
 496 static const struct nft_expr_ops nft_exthdr_tcp_set_ops = {
 497         .type           = &nft_exthdr_type,
 498         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 499         .eval           = nft_exthdr_tcp_set_eval,
 500         .init           = nft_exthdr_tcp_set_init,
 501         .dump           = nft_exthdr_dump_set,
 502 };
 503 
 504 static const struct nft_expr_ops *
 505 nft_exthdr_select_ops(const struct nft_ctx *ctx,
 506                       const struct nlattr * const tb[])
 507 {
 508         u32 op;
 509 
 510         if (!tb[NFTA_EXTHDR_OP])
 511                 return &nft_exthdr_ipv6_ops;
 512 
 513         if (tb[NFTA_EXTHDR_SREG] && tb[NFTA_EXTHDR_DREG])
 514                 return ERR_PTR(-EOPNOTSUPP);
 515 
 516         op = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OP]));
 517         switch (op) {
 518         case NFT_EXTHDR_OP_TCPOPT:
 519                 if (tb[NFTA_EXTHDR_SREG])
 520                         return &nft_exthdr_tcp_set_ops;
 521                 if (tb[NFTA_EXTHDR_DREG])
 522                         return &nft_exthdr_tcp_ops;
 523                 break;
 524         case NFT_EXTHDR_OP_IPV6:
 525                 if (tb[NFTA_EXTHDR_DREG])
 526                         return &nft_exthdr_ipv6_ops;
 527                 break;
 528         case NFT_EXTHDR_OP_IPV4:
 529                 if (ctx->family != NFPROTO_IPV6) {
 530                         if (tb[NFTA_EXTHDR_DREG])
 531                                 return &nft_exthdr_ipv4_ops;
 532                 }
 533                 break;
 534         }
 535 
 536         return ERR_PTR(-EOPNOTSUPP);
 537 }
 538 
 539 struct nft_expr_type nft_exthdr_type __read_mostly = {
 540         .name           = "exthdr",
 541         .select_ops     = nft_exthdr_select_ops,
 542         .policy         = nft_exthdr_policy,
 543         .maxattr        = NFTA_EXTHDR_MAX,
 544         .owner          = THIS_MODULE,
 545 };

/* [<][>][^][v][top][bottom][index][help] */