net/netfilter/nft_payload.c

   1 /*
   2  * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
   3  * Copyright (c) 2016 Pablo Neira Ayuso <pablo@netfilter.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/if_vlan.h>
  14 #include <linux/init.h>
  15 #include <linux/module.h>
  16 #include <linux/netlink.h>
  17 #include <linux/netfilter.h>
  18 #include <linux/netfilter/nf_tables.h>
  19 #include <net/netfilter/nf_tables_core.h>
  20 #include <net/netfilter/nf_tables.h>
  21 /* For layer 4 checksum field offset. */
  22 #include <linux/tcp.h>
  23 #include <linux/udp.h>
  24 #include <linux/icmpv6.h>
  25
  26 /* add vlan header into the user buffer for if tag was removed by offloads */
  27 static bool
  28 nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u8 offset, u8 len)
  29 {
  30         int mac_off = skb_mac_header(skb) - skb->data;
  31         u8 vlan_len, *vlanh, *dst_u8 = (u8 *) d;
  32         struct vlan_ethhdr veth;
  33
  34         vlanh = (u8 *) &veth;
  35         if (offset < ETH_HLEN) {
  36                 u8 ethlen = min_t(u8, len, ETH_HLEN - offset);
  37
  38                 if (skb_copy_bits(skb, mac_off, &veth, ETH_HLEN))
  39                         return false;
  40
  41                 veth.h_vlan_proto = skb->vlan_proto;
  42
  43                 memcpy(dst_u8, vlanh + offset, ethlen);
  44
  45                 len -= ethlen;
  46                 if (len == 0)
  47                         return true;
  48
  49                 dst_u8 += ethlen;
  50                 offset = ETH_HLEN;
  51         } else if (offset >= VLAN_ETH_HLEN) {
  52                 offset -= VLAN_HLEN;
  53                 goto skip;
  54         }
  55
  56         veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
  57         veth.h_vlan_encapsulated_proto = skb->protocol;
  58
  59         vlanh += offset;
  60
  61         vlan_len = min_t(u8, len, VLAN_ETH_HLEN - offset);
  62         memcpy(dst_u8, vlanh, vlan_len);
  63
  64         len -= vlan_len;
  65         if (!len)
  66                 return true;
  67
  68         dst_u8 += vlan_len;
  69  skip:
  70         return skb_copy_bits(skb, offset + mac_off, dst_u8, len) == 0;
  71 }
  72
  73 static void nft_payload_eval(const struct nft_expr *expr,
  74                              struct nft_regs *regs,
  75                              const struct nft_pktinfo *pkt)
  76 {
  77         const struct nft_payload *priv = nft_expr_priv(expr);
  78         const struct sk_buff *skb = pkt->skb;
  79         u32 *dest = &regs->data[priv->dreg];
  80         int offset;
  81
  82         dest[priv->len / NFT_REG32_SIZE] = 0;
  83         switch (priv->base) {
  84         case NFT_PAYLOAD_LL_HEADER:
  85                 if (!skb_mac_header_was_set(skb))
  86                         goto err;
  87
  88                 if (skb_vlan_tag_present(skb)) {
  89                         if (!nft_payload_copy_vlan(dest, skb,
  90                                                    priv->offset, priv->len))
  91                                 goto err;
  92                         return;
  93                 }
  94                 offset = skb_mac_header(skb) - skb->data;
  95                 break;
  96         case NFT_PAYLOAD_NETWORK_HEADER:
  97                 offset = skb_network_offset(skb);
  98                 break;
  99         case NFT_PAYLOAD_TRANSPORT_HEADER:
 100                 if (!pkt->tprot_set)
 101                         goto err;
 102                 offset = pkt->xt.thoff;
 103                 break;
 104         default:
 105                 BUG();
 106         }
 107         offset += priv->offset;
 108
 109         if (skb_copy_bits(skb, offset, dest, priv->len) < 0)
 110                 goto err;
 111         return;
 112 err:
 113         regs->verdict.code = NFT_BREAK;
 114 }
 115
 116 static const struct nla_policy nft_payload_policy[NFTA_PAYLOAD_MAX + 1] = {
 117         [NFTA_PAYLOAD_SREG]             = { .type = NLA_U32 },
 118         [NFTA_PAYLOAD_DREG]             = { .type = NLA_U32 },
 119         [NFTA_PAYLOAD_BASE]             = { .type = NLA_U32 },
 120         [NFTA_PAYLOAD_OFFSET]           = { .type = NLA_U32 },
 121         [NFTA_PAYLOAD_LEN]              = { .type = NLA_U32 },
 122         [NFTA_PAYLOAD_CSUM_TYPE]        = { .type = NLA_U32 },
 123         [NFTA_PAYLOAD_CSUM_OFFSET]      = { .type = NLA_U32 },
 124         [NFTA_PAYLOAD_CSUM_FLAGS]       = { .type = NLA_U32 },
 125 };
 126
 127 static int nft_payload_init(const struct nft_ctx *ctx,
 128                             const struct nft_expr *expr,
 129                             const struct nlattr * const tb[])
 130 {
 131         struct nft_payload *priv = nft_expr_priv(expr);
 132
 133         priv->base   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 134         priv->offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 135         priv->len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 136         priv->dreg   = nft_parse_register(tb[NFTA_PAYLOAD_DREG]);
 137
 138         return nft_validate_register_store(ctx, priv->dreg, NULL,
 139                                            NFT_DATA_VALUE, priv->len);
 140 }
 141
 142 static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
 143 {
 144         const struct nft_payload *priv = nft_expr_priv(expr);
 145
 146         if (nft_dump_register(skb, NFTA_PAYLOAD_DREG, priv->dreg) ||
 147             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
 148             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
 149             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)))
 150                 goto nla_put_failure;
 151         return 0;
 152
 153 nla_put_failure:
 154         return -1;
 155 }
 156
 157 static const struct nft_expr_ops nft_payload_ops = {
 158         .type           = &nft_payload_type,
 159         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 160         .eval           = nft_payload_eval,
 161         .init           = nft_payload_init,
 162         .dump           = nft_payload_dump,
 163 };
 164
 165 const struct nft_expr_ops nft_payload_fast_ops = {
 166         .type           = &nft_payload_type,
 167         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 168         .eval           = nft_payload_eval,
 169         .init           = nft_payload_init,
 170         .dump           = nft_payload_dump,
 171 };
 172
 173 static inline void nft_csum_replace(__sum16 *sum, __wsum fsum, __wsum tsum)
 174 {
 175         *sum = csum_fold(csum_add(csum_sub(~csum_unfold(*sum), fsum), tsum));
 176         if (*sum == 0)
 177                 *sum = CSUM_MANGLED_0;
 178 }
 179
 180 static bool nft_payload_udp_checksum(struct sk_buff *skb, unsigned int thoff)
 181 {
 182         struct udphdr *uh, _uh;
 183
 184         uh = skb_header_pointer(skb, thoff, sizeof(_uh), &_uh);
 185         if (!uh)
 186                 return false;
 187
 188         return (__force bool)uh->check;
 189 }
 190
 191 static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
 192                                      struct sk_buff *skb,
 193                                      unsigned int *l4csum_offset)
 194 {
 195         switch (pkt->tprot) {
 196         case IPPROTO_TCP:
 197                 *l4csum_offset = offsetof(struct tcphdr, check);
 198                 break;
 199         case IPPROTO_UDP:
 200                 if (!nft_payload_udp_checksum(skb, pkt->xt.thoff))
 201                         return -1;
 202                 /* Fall through. */
 203         case IPPROTO_UDPLITE:
 204                 *l4csum_offset = offsetof(struct udphdr, check);
 205                 break;
 206         case IPPROTO_ICMPV6:
 207                 *l4csum_offset = offsetof(struct icmp6hdr, icmp6_cksum);
 208                 break;
 209         default:
 210                 return -1;
 211         }
 212
 213         *l4csum_offset += pkt->xt.thoff;
 214         return 0;
 215 }
 216
 217 static int nft_payload_l4csum_update(const struct nft_pktinfo *pkt,
 218                                      struct sk_buff *skb,
 219                                      __wsum fsum, __wsum tsum)
 220 {
 221         int l4csum_offset;
 222         __sum16 sum;
 223
 224         /* If we cannot determine layer 4 checksum offset or this packet doesn't
 225          * require layer 4 checksum recalculation, skip this packet.
 226          */
 227         if (nft_payload_l4csum_offset(pkt, skb, &l4csum_offset) < 0)
 228                 return 0;
 229
 230         if (skb_copy_bits(skb, l4csum_offset, &sum, sizeof(sum)) < 0)
 231                 return -1;
 232
 233         /* Checksum mangling for an arbitrary amount of bytes, based on
 234          * inet_proto_csum_replace*() functions.
 235          */
 236         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 237                 nft_csum_replace(&sum, fsum, tsum);
 238                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 239                         skb->csum = ~csum_add(csum_sub(~(skb->csum), fsum),
 240                                               tsum);
 241                 }
 242         } else {
 243                 sum = ~csum_fold(csum_add(csum_sub(csum_unfold(sum), fsum),
 244                                           tsum));
 245         }
 246
 247         if (!skb_make_writable(skb, l4csum_offset + sizeof(sum)) ||
 248             skb_store_bits(skb, l4csum_offset, &sum, sizeof(sum)) < 0)
 249                 return -1;
 250
 251         return 0;
 252 }
 253
 254 static int nft_payload_csum_inet(struct sk_buff *skb, const u32 *src,
 255                                  __wsum fsum, __wsum tsum, int csum_offset)
 256 {
 257         __sum16 sum;
 258
 259         if (skb_copy_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
 260                 return -1;
 261
 262         nft_csum_replace(&sum, fsum, tsum);
 263         if (!skb_make_writable(skb, csum_offset + sizeof(sum)) ||
 264             skb_store_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
 265                 return -1;
 266
 267         return 0;
 268 }
 269
 270 static void nft_payload_set_eval(const struct nft_expr *expr,
 271                                  struct nft_regs *regs,
 272                                  const struct nft_pktinfo *pkt)
 273 {
 274         const struct nft_payload_set *priv = nft_expr_priv(expr);
 275         struct sk_buff *skb = pkt->skb;
 276         const u32 *src = &regs->data[priv->sreg];
 277         int offset, csum_offset;
 278         __wsum fsum, tsum;
 279
 280         switch (priv->base) {
 281         case NFT_PAYLOAD_LL_HEADER:
 282                 if (!skb_mac_header_was_set(skb))
 283                         goto err;
 284                 offset = skb_mac_header(skb) - skb->data;
 285                 break;
 286         case NFT_PAYLOAD_NETWORK_HEADER:
 287                 offset = skb_network_offset(skb);
 288                 break;
 289         case NFT_PAYLOAD_TRANSPORT_HEADER:
 290                 if (!pkt->tprot_set)
 291                         goto err;
 292                 offset = pkt->xt.thoff;
 293                 break;
 294         default:
 295                 BUG();
 296         }
 297
 298         csum_offset = offset + priv->csum_offset;
 299         offset += priv->offset;
 300
 301         if ((priv->csum_type == NFT_PAYLOAD_CSUM_INET || priv->csum_flags) &&
 302             (priv->base != NFT_PAYLOAD_TRANSPORT_HEADER ||
 303              skb->ip_summed != CHECKSUM_PARTIAL)) {
 304                 fsum = skb_checksum(skb, offset, priv->len, 0);
 305                 tsum = csum_partial(src, priv->len, 0);
 306
 307                 if (priv->csum_type == NFT_PAYLOAD_CSUM_INET &&
 308                     nft_payload_csum_inet(skb, src, fsum, tsum, csum_offset))
 309                         goto err;
 310
 311                 if (priv->csum_flags &&
 312                     nft_payload_l4csum_update(pkt, skb, fsum, tsum) < 0)
 313                         goto err;
 314         }
 315
 316         if (!skb_make_writable(skb, max(offset + priv->len, 0)) ||
 317             skb_store_bits(skb, offset, src, priv->len) < 0)
 318                 goto err;
 319
 320         return;
 321 err:
 322         regs->verdict.code = NFT_BREAK;
 323 }
 324
 325 static int nft_payload_set_init(const struct nft_ctx *ctx,
 326                                 const struct nft_expr *expr,
 327                                 const struct nlattr * const tb[])
 328 {
 329         struct nft_payload_set *priv = nft_expr_priv(expr);
 330
 331         priv->base        = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 332         priv->offset      = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 333         priv->len         = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 334         priv->sreg        = nft_parse_register(tb[NFTA_PAYLOAD_SREG]);
 335
 336         if (tb[NFTA_PAYLOAD_CSUM_TYPE])
 337                 priv->csum_type =
 338                         ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_TYPE]));
 339         if (tb[NFTA_PAYLOAD_CSUM_OFFSET])
 340                 priv->csum_offset =
 341                         ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_OFFSET]));
 342         if (tb[NFTA_PAYLOAD_CSUM_FLAGS]) {
 343                 u32 flags;
 344
 345                 flags = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_FLAGS]));
 346                 if (flags & ~NFT_PAYLOAD_L4CSUM_PSEUDOHDR)
 347                         return -EINVAL;
 348
 349                 priv->csum_flags = flags;
 350         }
 351
 352         switch (priv->csum_type) {
 353         case NFT_PAYLOAD_CSUM_NONE:
 354         case NFT_PAYLOAD_CSUM_INET:
 355                 break;
 356         default:
 357                 return -EOPNOTSUPP;
 358         }
 359
 360         return nft_validate_register_load(priv->sreg, priv->len);
 361 }
 362
 363 static int nft_payload_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
 364 {
 365         const struct nft_payload_set *priv = nft_expr_priv(expr);
 366
 367         if (nft_dump_register(skb, NFTA_PAYLOAD_SREG, priv->sreg) ||
 368             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
 369             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
 370             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)) ||
 371             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_TYPE, htonl(priv->csum_type)) ||
 372             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_OFFSET,
 373                          htonl(priv->csum_offset)) ||
 374             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_FLAGS, htonl(priv->csum_flags)))
 375                 goto nla_put_failure;
 376         return 0;
 377
 378 nla_put_failure:
 379         return -1;
 380 }
 381
 382 static const struct nft_expr_ops nft_payload_set_ops = {
 383         .type           = &nft_payload_type,
 384         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload_set)),
 385         .eval           = nft_payload_set_eval,
 386         .init           = nft_payload_set_init,
 387         .dump           = nft_payload_set_dump,
 388 };
 389
 390 static const struct nft_expr_ops *
 391 nft_payload_select_ops(const struct nft_ctx *ctx,
 392                        const struct nlattr * const tb[])
 393 {
 394         enum nft_payload_bases base;
 395         unsigned int offset, len;
 396
 397         if (tb[NFTA_PAYLOAD_BASE] == NULL ||
 398             tb[NFTA_PAYLOAD_OFFSET] == NULL ||
 399             tb[NFTA_PAYLOAD_LEN] == NULL)
 400                 return ERR_PTR(-EINVAL);
 401
 402         base = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 403         switch (base) {
 404         case NFT_PAYLOAD_LL_HEADER:
 405         case NFT_PAYLOAD_NETWORK_HEADER:
 406         case NFT_PAYLOAD_TRANSPORT_HEADER:
 407                 break;
 408         default:
 409                 return ERR_PTR(-EOPNOTSUPP);
 410         }
 411
 412         if (tb[NFTA_PAYLOAD_SREG] != NULL) {
 413                 if (tb[NFTA_PAYLOAD_DREG] != NULL)
 414                         return ERR_PTR(-EINVAL);
 415                 return &nft_payload_set_ops;
 416         }
 417
 418         if (tb[NFTA_PAYLOAD_DREG] == NULL)
 419                 return ERR_PTR(-EINVAL);
 420
 421         offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 422         len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 423
 424         if (len <= 4 && is_power_of_2(len) && IS_ALIGNED(offset, len) &&
 425             base != NFT_PAYLOAD_LL_HEADER)
 426                 return &nft_payload_fast_ops;
 427         else
 428                 return &nft_payload_ops;
 429 }
 430
 431 struct nft_expr_type nft_payload_type __read_mostly = {
 432         .name           = "payload",
 433         .select_ops     = nft_payload_select_ops,
 434         .policy         = nft_payload_policy,
 435         .maxattr        = NFTA_PAYLOAD_MAX,
 436         .owner          = THIS_MODULE,
 437 };