net/netfilter/nft_exthdr.c

   1 /*
   2  * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Development of this code funded by Astaro AG (http://www.astaro.com/)
   9  */
  10
  11 #include <asm/unaligned.h>
  12 #include <linux/kernel.h>
  13 #include <linux/netlink.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter/nf_tables.h>
  16 #include <net/netfilter/nf_tables_core.h>
  17 #include <net/netfilter/nf_tables.h>
  18 #include <net/tcp.h>
  19
  20 struct nft_exthdr {
  21         u8                      type;
  22         u8                      offset;
  23         u8                      len;
  24         u8                      op;
  25         enum nft_registers      dreg:8;
  26         enum nft_registers      sreg:8;
  27         u8                      flags;
  28 };
  29
  30 static unsigned int optlen(const u8 *opt, unsigned int offset)
  31 {
  32         /* Beware zero-length options: make finite progress */
  33         if (opt[offset] <= TCPOPT_NOP || opt[offset + 1] == 0)
  34                 return 1;
  35         else
  36                 return opt[offset + 1];
  37 }
  38
  39 static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
  40                                  struct nft_regs *regs,
  41                                  const struct nft_pktinfo *pkt)
  42 {
  43         struct nft_exthdr *priv = nft_expr_priv(expr);
  44         u32 *dest = &regs->data[priv->dreg];
  45         unsigned int offset = 0;
  46         int err;
  47
  48         err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL);
  49         if (priv->flags & NFT_EXTHDR_F_PRESENT) {
  50                 *dest = (err >= 0);
  51                 return;
  52         } else if (err < 0) {
  53                 goto err;
  54         }
  55         offset += priv->offset;
  56
  57         dest[priv->len / NFT_REG32_SIZE] = 0;
  58         if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
  59                 goto err;
  60         return;
  61 err:
  62         regs->verdict.code = NFT_BREAK;
  63 }
  64
  65 static void *
  66 nft_tcp_header_pointer(const struct nft_pktinfo *pkt,
  67                        unsigned int len, void *buffer, unsigned int *tcphdr_len)
  68 {
  69         struct tcphdr *tcph;
  70
  71         if (!pkt->tprot_set || pkt->tprot != IPPROTO_TCP)
  72                 return NULL;
  73
  74         tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, sizeof(*tcph), buffer);
  75         if (!tcph)
  76                 return NULL;
  77
  78         *tcphdr_len = __tcp_hdrlen(tcph);
  79         if (*tcphdr_len < sizeof(*tcph) || *tcphdr_len > len)
  80                 return NULL;
  81
  82         return skb_header_pointer(pkt->skb, pkt->xt.thoff, *tcphdr_len, buffer);
  83 }
  84
  85 static void nft_exthdr_tcp_eval(const struct nft_expr *expr,
  86                                 struct nft_regs *regs,
  87                                 const struct nft_pktinfo *pkt)
  88 {
  89         u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
  90         struct nft_exthdr *priv = nft_expr_priv(expr);
  91         unsigned int i, optl, tcphdr_len, offset;
  92         u32 *dest = &regs->data[priv->dreg];
  93         struct tcphdr *tcph;
  94         u8 *opt;
  95
  96         tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
  97         if (!tcph)
  98                 goto err;
  99
 100         opt = (u8 *)tcph;
 101         for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
 102                 optl = optlen(opt, i);
 103
 104                 if (priv->type != opt[i])
 105                         continue;
 106
 107                 if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
 108                         goto err;
 109
 110                 offset = i + priv->offset;
 111                 if (priv->flags & NFT_EXTHDR_F_PRESENT) {
 112                         *dest = 1;
 113                 } else {
 114                         dest[priv->len / NFT_REG32_SIZE] = 0;
 115                         memcpy(dest, opt + offset, priv->len);
 116                 }
 117
 118                 return;
 119         }
 120
 121 err:
 122         if (priv->flags & NFT_EXTHDR_F_PRESENT)
 123                 *dest = 0;
 124         else
 125                 regs->verdict.code = NFT_BREAK;
 126 }
 127
 128 static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr,
 129                                     struct nft_regs *regs,
 130                                     const struct nft_pktinfo *pkt)
 131 {
 132         u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
 133         struct nft_exthdr *priv = nft_expr_priv(expr);
 134         unsigned int i, optl, tcphdr_len, offset;
 135         struct tcphdr *tcph;
 136         u8 *opt;
 137         u32 src;
 138
 139         tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
 140         if (!tcph)
 141                 return;
 142
 143         opt = (u8 *)tcph;
 144         for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
 145                 union {
 146                         u8 octet;
 147                         __be16 v16;
 148                         __be32 v32;
 149                 } old, new;
 150
 151                 optl = optlen(opt, i);
 152
 153                 if (priv->type != opt[i])
 154                         continue;
 155
 156                 if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
 157                         return;
 158
 159                 if (!skb_make_writable(pkt->skb, pkt->xt.thoff + i + priv->len))
 160                         return;
 161
 162                 tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff,
 163                                               &tcphdr_len);
 164                 if (!tcph)
 165                         return;
 166
 167                 src = regs->data[priv->sreg];
 168                 offset = i + priv->offset;
 169
 170                 switch (priv->len) {
 171                 case 2:
 172                         old.v16 = get_unaligned((u16 *)(opt + offset));
 173                         new.v16 = src;
 174
 175                         switch (priv->type) {
 176                         case TCPOPT_MSS:
 177                                 /* increase can cause connection to stall */
 178                                 if (ntohs(old.v16) <= ntohs(new.v16))
 179                                         return;
 180                         break;
 181                         }
 182
 183                         if (old.v16 == new.v16)
 184                                 return;
 185
 186                         put_unaligned(new.v16, (u16*)(opt + offset));
 187                         inet_proto_csum_replace2(&tcph->check, pkt->skb,
 188                                                  old.v16, new.v16, false);
 189                         break;
 190                 case 4:
 191                         new.v32 = src;
 192                         old.v32 = get_unaligned((u32 *)(opt + offset));
 193
 194                         if (old.v32 == new.v32)
 195                                 return;
 196
 197                         put_unaligned(new.v32, (u32*)(opt + offset));
 198                         inet_proto_csum_replace4(&tcph->check, pkt->skb,
 199                                                  old.v32, new.v32, false);
 200                         break;
 201                 default:
 202                         WARN_ON_ONCE(1);
 203                         break;
 204                 }
 205
 206                 return;
 207         }
 208 }
 209
 210 static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = {
 211         [NFTA_EXTHDR_DREG]              = { .type = NLA_U32 },
 212         [NFTA_EXTHDR_TYPE]              = { .type = NLA_U8 },
 213         [NFTA_EXTHDR_OFFSET]            = { .type = NLA_U32 },
 214         [NFTA_EXTHDR_LEN]               = { .type = NLA_U32 },
 215         [NFTA_EXTHDR_FLAGS]             = { .type = NLA_U32 },
 216         [NFTA_EXTHDR_OP]                = { .type = NLA_U32 },
 217         [NFTA_EXTHDR_SREG]              = { .type = NLA_U32 },
 218 };
 219
 220 static int nft_exthdr_init(const struct nft_ctx *ctx,
 221                            const struct nft_expr *expr,
 222                            const struct nlattr * const tb[])
 223 {
 224         struct nft_exthdr *priv = nft_expr_priv(expr);
 225         u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
 226         int err;
 227
 228         if (!tb[NFTA_EXTHDR_DREG] ||
 229             !tb[NFTA_EXTHDR_TYPE] ||
 230             !tb[NFTA_EXTHDR_OFFSET] ||
 231             !tb[NFTA_EXTHDR_LEN])
 232                 return -EINVAL;
 233
 234         err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
 235         if (err < 0)
 236                 return err;
 237
 238         err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
 239         if (err < 0)
 240                 return err;
 241
 242         if (tb[NFTA_EXTHDR_FLAGS]) {
 243                 err = nft_parse_u32_check(tb[NFTA_EXTHDR_FLAGS], U8_MAX, &flags);
 244                 if (err < 0)
 245                         return err;
 246
 247                 if (flags & ~NFT_EXTHDR_F_PRESENT)
 248                         return -EINVAL;
 249         }
 250
 251         if (tb[NFTA_EXTHDR_OP]) {
 252                 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
 253                 if (err < 0)
 254                         return err;
 255         }
 256
 257         priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
 258         priv->offset = offset;
 259         priv->len    = len;
 260         priv->dreg   = nft_parse_register(tb[NFTA_EXTHDR_DREG]);
 261         priv->flags  = flags;
 262         priv->op     = op;
 263
 264         return nft_validate_register_store(ctx, priv->dreg, NULL,
 265                                            NFT_DATA_VALUE, priv->len);
 266 }
 267
 268 static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx,
 269                                    const struct nft_expr *expr,
 270                                    const struct nlattr * const tb[])
 271 {
 272         struct nft_exthdr *priv = nft_expr_priv(expr);
 273         u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
 274         int err;
 275
 276         if (!tb[NFTA_EXTHDR_SREG] ||
 277             !tb[NFTA_EXTHDR_TYPE] ||
 278             !tb[NFTA_EXTHDR_OFFSET] ||
 279             !tb[NFTA_EXTHDR_LEN])
 280                 return -EINVAL;
 281
 282         if (tb[NFTA_EXTHDR_DREG] || tb[NFTA_EXTHDR_FLAGS])
 283                 return -EINVAL;
 284
 285         err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
 286         if (err < 0)
 287                 return err;
 288
 289         err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
 290         if (err < 0)
 291                 return err;
 292
 293         if (offset < 2)
 294                 return -EOPNOTSUPP;
 295
 296         switch (len) {
 297         case 2: break;
 298         case 4: break;
 299         default:
 300                 return -EOPNOTSUPP;
 301         }
 302
 303         err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
 304         if (err < 0)
 305                 return err;
 306
 307         priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
 308         priv->offset = offset;
 309         priv->len    = len;
 310         priv->sreg   = nft_parse_register(tb[NFTA_EXTHDR_SREG]);
 311         priv->flags  = flags;
 312         priv->op     = op;
 313
 314         return nft_validate_register_load(priv->sreg, priv->len);
 315 }
 316
 317 static int nft_exthdr_dump_common(struct sk_buff *skb, const struct nft_exthdr *priv)
 318 {
 319         if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type))
 320                 goto nla_put_failure;
 321         if (nla_put_be32(skb, NFTA_EXTHDR_OFFSET, htonl(priv->offset)))
 322                 goto nla_put_failure;
 323         if (nla_put_be32(skb, NFTA_EXTHDR_LEN, htonl(priv->len)))
 324                 goto nla_put_failure;
 325         if (nla_put_be32(skb, NFTA_EXTHDR_FLAGS, htonl(priv->flags)))
 326                 goto nla_put_failure;
 327         if (nla_put_be32(skb, NFTA_EXTHDR_OP, htonl(priv->op)))
 328                 goto nla_put_failure;
 329         return 0;
 330
 331 nla_put_failure:
 332         return -1;
 333 }
 334
 335 static int nft_exthdr_dump(struct sk_buff *skb, const struct nft_expr *expr)
 336 {
 337         const struct nft_exthdr *priv = nft_expr_priv(expr);
 338
 339         if (nft_dump_register(skb, NFTA_EXTHDR_DREG, priv->dreg))
 340                 return -1;
 341
 342         return nft_exthdr_dump_common(skb, priv);
 343 }
 344
 345 static int nft_exthdr_dump_set(struct sk_buff *skb, const struct nft_expr *expr)
 346 {
 347         const struct nft_exthdr *priv = nft_expr_priv(expr);
 348
 349         if (nft_dump_register(skb, NFTA_EXTHDR_SREG, priv->sreg))
 350                 return -1;
 351
 352         return nft_exthdr_dump_common(skb, priv);
 353 }
 354
 355 static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
 356         .type           = &nft_exthdr_type,
 357         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 358         .eval           = nft_exthdr_ipv6_eval,
 359         .init           = nft_exthdr_init,
 360         .dump           = nft_exthdr_dump,
 361 };
 362
 363 static const struct nft_expr_ops nft_exthdr_tcp_ops = {
 364         .type           = &nft_exthdr_type,
 365         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 366         .eval           = nft_exthdr_tcp_eval,
 367         .init           = nft_exthdr_init,
 368         .dump           = nft_exthdr_dump,
 369 };
 370
 371 static const struct nft_expr_ops nft_exthdr_tcp_set_ops = {
 372         .type           = &nft_exthdr_type,
 373         .size           = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 374         .eval           = nft_exthdr_tcp_set_eval,
 375         .init           = nft_exthdr_tcp_set_init,
 376         .dump           = nft_exthdr_dump_set,
 377 };
 378
 379 static const struct nft_expr_ops *
 380 nft_exthdr_select_ops(const struct nft_ctx *ctx,
 381                       const struct nlattr * const tb[])
 382 {
 383         u32 op;
 384
 385         if (!tb[NFTA_EXTHDR_OP])
 386                 return &nft_exthdr_ipv6_ops;
 387
 388         if (tb[NFTA_EXTHDR_SREG] && tb[NFTA_EXTHDR_DREG])
 389                 return ERR_PTR(-EOPNOTSUPP);
 390
 391         op = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OP]));
 392         switch (op) {
 393         case NFT_EXTHDR_OP_TCPOPT:
 394                 if (tb[NFTA_EXTHDR_SREG])
 395                         return &nft_exthdr_tcp_set_ops;
 396                 if (tb[NFTA_EXTHDR_DREG])
 397                         return &nft_exthdr_tcp_ops;
 398                 break;
 399         case NFT_EXTHDR_OP_IPV6:
 400                 if (tb[NFTA_EXTHDR_DREG])
 401                         return &nft_exthdr_ipv6_ops;
 402                 break;
 403         }
 404
 405         return ERR_PTR(-EOPNOTSUPP);
 406 }
 407
 408 struct nft_expr_type nft_exthdr_type __read_mostly = {
 409         .name           = "exthdr",
 410         .select_ops     = nft_exthdr_select_ops,
 411         .policy         = nft_exthdr_policy,
 412         .maxattr        = NFTA_EXTHDR_MAX,
 413         .owner          = THIS_MODULE,
 414 };