net/netfilter/nft_payload.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
   4  * Copyright (c) 2016 Pablo Neira Ayuso <pablo@netfilter.org>
   5  *
   6  * Development of this code funded by Astaro AG (http://www.astaro.com/)
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/if_vlan.h>
  11 #include <linux/init.h>
  12 #include <linux/module.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 /* For layer 4 checksum field offset. */
  19 #include <linux/tcp.h>
  20 #include <linux/udp.h>
  21 #include <linux/icmpv6.h>
  22
  23 /* add vlan header into the user buffer for if tag was removed by offloads */
  24 static bool
  25 nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u8 offset, u8 len)
  26 {
  27         int mac_off = skb_mac_header(skb) - skb->data;
  28         u8 vlan_len, *vlanh, *dst_u8 = (u8 *) d;
  29         struct vlan_ethhdr veth;
  30
  31         vlanh = (u8 *) &veth;
  32         if (offset < ETH_HLEN) {
  33                 u8 ethlen = min_t(u8, len, ETH_HLEN - offset);
  34
  35                 if (skb_copy_bits(skb, mac_off, &veth, ETH_HLEN))
  36                         return false;
  37
  38                 veth.h_vlan_proto = skb->vlan_proto;
  39
  40                 memcpy(dst_u8, vlanh + offset, ethlen);
  41
  42                 len -= ethlen;
  43                 if (len == 0)
  44                         return true;
  45
  46                 dst_u8 += ethlen;
  47                 offset = ETH_HLEN;
  48         } else if (offset >= VLAN_ETH_HLEN) {
  49                 offset -= VLAN_HLEN;
  50                 goto skip;
  51         }
  52
  53         veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
  54         veth.h_vlan_encapsulated_proto = skb->protocol;
  55
  56         vlanh += offset;
  57
  58         vlan_len = min_t(u8, len, VLAN_ETH_HLEN - offset);
  59         memcpy(dst_u8, vlanh, vlan_len);
  60
  61         len -= vlan_len;
  62         if (!len)
  63                 return true;
  64
  65         dst_u8 += vlan_len;
  66  skip:
  67         return skb_copy_bits(skb, offset + mac_off, dst_u8, len) == 0;
  68 }
  69
  70 void nft_payload_eval(const struct nft_expr *expr,
  71                       struct nft_regs *regs,
  72                       const struct nft_pktinfo *pkt)
  73 {
  74         const struct nft_payload *priv = nft_expr_priv(expr);
  75         const struct sk_buff *skb = pkt->skb;
  76         u32 *dest = &regs->data[priv->dreg];
  77         int offset;
  78
  79         dest[priv->len / NFT_REG32_SIZE] = 0;
  80         switch (priv->base) {
  81         case NFT_PAYLOAD_LL_HEADER:
  82                 if (!skb_mac_header_was_set(skb))
  83                         goto err;
  84
  85                 if (skb_vlan_tag_present(skb)) {
  86                         if (!nft_payload_copy_vlan(dest, skb,
  87                                                    priv->offset, priv->len))
  88                                 goto err;
  89                         return;
  90                 }
  91                 offset = skb_mac_header(skb) - skb->data;
  92                 break;
  93         case NFT_PAYLOAD_NETWORK_HEADER:
  94                 offset = skb_network_offset(skb);
  95                 break;
  96         case NFT_PAYLOAD_TRANSPORT_HEADER:
  97                 if (!pkt->tprot_set)
  98                         goto err;
  99                 offset = pkt->xt.thoff;
 100                 break;
 101         default:
 102                 BUG();
 103         }
 104         offset += priv->offset;
 105
 106         if (skb_copy_bits(skb, offset, dest, priv->len) < 0)
 107                 goto err;
 108         return;
 109 err:
 110         regs->verdict.code = NFT_BREAK;
 111 }
 112
 113 static const struct nla_policy nft_payload_policy[NFTA_PAYLOAD_MAX + 1] = {
 114         [NFTA_PAYLOAD_SREG]             = { .type = NLA_U32 },
 115         [NFTA_PAYLOAD_DREG]             = { .type = NLA_U32 },
 116         [NFTA_PAYLOAD_BASE]             = { .type = NLA_U32 },
 117         [NFTA_PAYLOAD_OFFSET]           = { .type = NLA_U32 },
 118         [NFTA_PAYLOAD_LEN]              = { .type = NLA_U32 },
 119         [NFTA_PAYLOAD_CSUM_TYPE]        = { .type = NLA_U32 },
 120         [NFTA_PAYLOAD_CSUM_OFFSET]      = { .type = NLA_U32 },
 121 };
 122
 123 static int nft_payload_init(const struct nft_ctx *ctx,
 124                             const struct nft_expr *expr,
 125                             const struct nlattr * const tb[])
 126 {
 127         struct nft_payload *priv = nft_expr_priv(expr);
 128
 129         priv->base   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 130         priv->offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 131         priv->len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 132         priv->dreg   = nft_parse_register(tb[NFTA_PAYLOAD_DREG]);
 133
 134         return nft_validate_register_store(ctx, priv->dreg, NULL,
 135                                            NFT_DATA_VALUE, priv->len);
 136 }
 137
 138 static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
 139 {
 140         const struct nft_payload *priv = nft_expr_priv(expr);
 141
 142         if (nft_dump_register(skb, NFTA_PAYLOAD_DREG, priv->dreg) ||
 143             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
 144             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
 145             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)))
 146                 goto nla_put_failure;
 147         return 0;
 148
 149 nla_put_failure:
 150         return -1;
 151 }
 152
 153 static const struct nft_expr_ops nft_payload_ops = {
 154         .type           = &nft_payload_type,
 155         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 156         .eval           = nft_payload_eval,
 157         .init           = nft_payload_init,
 158         .dump           = nft_payload_dump,
 159 };
 160
 161 const struct nft_expr_ops nft_payload_fast_ops = {
 162         .type           = &nft_payload_type,
 163         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 164         .eval           = nft_payload_eval,
 165         .init           = nft_payload_init,
 166         .dump           = nft_payload_dump,
 167 };
 168
 169 static inline void nft_csum_replace(__sum16 *sum, __wsum fsum, __wsum tsum)
 170 {
 171         *sum = csum_fold(csum_add(csum_sub(~csum_unfold(*sum), fsum), tsum));
 172         if (*sum == 0)
 173                 *sum = CSUM_MANGLED_0;
 174 }
 175
 176 static bool nft_payload_udp_checksum(struct sk_buff *skb, unsigned int thoff)
 177 {
 178         struct udphdr *uh, _uh;
 179
 180         uh = skb_header_pointer(skb, thoff, sizeof(_uh), &_uh);
 181         if (!uh)
 182                 return false;
 183
 184         return (__force bool)uh->check;
 185 }
 186
 187 static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
 188                                      struct sk_buff *skb,
 189                                      unsigned int *l4csum_offset)
 190 {
 191         switch (pkt->tprot) {
 192         case IPPROTO_TCP:
 193                 *l4csum_offset = offsetof(struct tcphdr, check);
 194                 break;
 195         case IPPROTO_UDP:
 196                 if (!nft_payload_udp_checksum(skb, pkt->xt.thoff))
 197                         return -1;
 198                 /* Fall through. */
 199         case IPPROTO_UDPLITE:
 200                 *l4csum_offset = offsetof(struct udphdr, check);
 201                 break;
 202         case IPPROTO_ICMPV6:
 203                 *l4csum_offset = offsetof(struct icmp6hdr, icmp6_cksum);
 204                 break;
 205         default:
 206                 return -1;
 207         }
 208
 209         *l4csum_offset += pkt->xt.thoff;
 210         return 0;
 211 }
 212
 213 static int nft_payload_l4csum_update(const struct nft_pktinfo *pkt,
 214                                      struct sk_buff *skb,
 215                                      __wsum fsum, __wsum tsum)
 216 {
 217         int l4csum_offset;
 218         __sum16 sum;
 219
 220         /* If we cannot determine layer 4 checksum offset or this packet doesn't
 221          * require layer 4 checksum recalculation, skip this packet.
 222          */
 223         if (nft_payload_l4csum_offset(pkt, skb, &l4csum_offset) < 0)
 224                 return 0;
 225
 226         if (skb_copy_bits(skb, l4csum_offset, &sum, sizeof(sum)) < 0)
 227                 return -1;
 228
 229         /* Checksum mangling for an arbitrary amount of bytes, based on
 230          * inet_proto_csum_replace*() functions.
 231          */
 232         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 233                 nft_csum_replace(&sum, fsum, tsum);
 234                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 235                         skb->csum = ~csum_add(csum_sub(~(skb->csum), fsum),
 236                                               tsum);
 237                 }
 238         } else {
 239                 sum = ~csum_fold(csum_add(csum_sub(csum_unfold(sum), fsum),
 240                                           tsum));
 241         }
 242
 243         if (!skb_make_writable(skb, l4csum_offset + sizeof(sum)) ||
 244             skb_store_bits(skb, l4csum_offset, &sum, sizeof(sum)) < 0)
 245                 return -1;
 246
 247         return 0;
 248 }
 249
 250 static int nft_payload_csum_inet(struct sk_buff *skb, const u32 *src,
 251                                  __wsum fsum, __wsum tsum, int csum_offset)
 252 {
 253         __sum16 sum;
 254
 255         if (skb_copy_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
 256                 return -1;
 257
 258         nft_csum_replace(&sum, fsum, tsum);
 259         if (!skb_make_writable(skb, csum_offset + sizeof(sum)) ||
 260             skb_store_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
 261                 return -1;
 262
 263         return 0;
 264 }
 265
 266 static void nft_payload_set_eval(const struct nft_expr *expr,
 267                                  struct nft_regs *regs,
 268                                  const struct nft_pktinfo *pkt)
 269 {
 270         const struct nft_payload_set *priv = nft_expr_priv(expr);
 271         struct sk_buff *skb = pkt->skb;
 272         const u32 *src = &regs->data[priv->sreg];
 273         int offset, csum_offset;
 274         __wsum fsum, tsum;
 275
 276         switch (priv->base) {
 277         case NFT_PAYLOAD_LL_HEADER:
 278                 if (!skb_mac_header_was_set(skb))
 279                         goto err;
 280                 offset = skb_mac_header(skb) - skb->data;
 281                 break;
 282         case NFT_PAYLOAD_NETWORK_HEADER:
 283                 offset = skb_network_offset(skb);
 284                 break;
 285         case NFT_PAYLOAD_TRANSPORT_HEADER:
 286                 if (!pkt->tprot_set)
 287                         goto err;
 288                 offset = pkt->xt.thoff;
 289                 break;
 290         default:
 291                 BUG();
 292         }
 293
 294         csum_offset = offset + priv->csum_offset;
 295         offset += priv->offset;
 296
 297         if ((priv->csum_type == NFT_PAYLOAD_CSUM_INET || priv->csum_flags) &&
 298             (priv->base != NFT_PAYLOAD_TRANSPORT_HEADER ||
 299              skb->ip_summed != CHECKSUM_PARTIAL)) {
 300                 fsum = skb_checksum(skb, offset, priv->len, 0);
 301                 tsum = csum_partial(src, priv->len, 0);
 302
 303                 if (priv->csum_type == NFT_PAYLOAD_CSUM_INET &&
 304                     nft_payload_csum_inet(skb, src, fsum, tsum, csum_offset))
 305                         goto err;
 306
 307                 if (priv->csum_flags &&
 308                     nft_payload_l4csum_update(pkt, skb, fsum, tsum) < 0)
 309                         goto err;
 310         }
 311
 312         if (!skb_make_writable(skb, max(offset + priv->len, 0)) ||
 313             skb_store_bits(skb, offset, src, priv->len) < 0)
 314                 goto err;
 315
 316         return;
 317 err:
 318         regs->verdict.code = NFT_BREAK;
 319 }
 320
 321 static int nft_payload_set_init(const struct nft_ctx *ctx,
 322                                 const struct nft_expr *expr,
 323                                 const struct nlattr * const tb[])
 324 {
 325         struct nft_payload_set *priv = nft_expr_priv(expr);
 326
 327         priv->base        = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 328         priv->offset      = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 329         priv->len         = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 330         priv->sreg        = nft_parse_register(tb[NFTA_PAYLOAD_SREG]);
 331
 332         if (tb[NFTA_PAYLOAD_CSUM_TYPE])
 333                 priv->csum_type =
 334                         ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_TYPE]));
 335         if (tb[NFTA_PAYLOAD_CSUM_OFFSET])
 336                 priv->csum_offset =
 337                         ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_OFFSET]));
 338         if (tb[NFTA_PAYLOAD_CSUM_FLAGS]) {
 339                 u32 flags;
 340
 341                 flags = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_FLAGS]));
 342                 if (flags & ~NFT_PAYLOAD_L4CSUM_PSEUDOHDR)
 343                         return -EINVAL;
 344
 345                 priv->csum_flags = flags;
 346         }
 347
 348         switch (priv->csum_type) {
 349         case NFT_PAYLOAD_CSUM_NONE:
 350         case NFT_PAYLOAD_CSUM_INET:
 351                 break;
 352         default:
 353                 return -EOPNOTSUPP;
 354         }
 355
 356         return nft_validate_register_load(priv->sreg, priv->len);
 357 }
 358
 359 static int nft_payload_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
 360 {
 361         const struct nft_payload_set *priv = nft_expr_priv(expr);
 362
 363         if (nft_dump_register(skb, NFTA_PAYLOAD_SREG, priv->sreg) ||
 364             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
 365             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
 366             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)) ||
 367             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_TYPE, htonl(priv->csum_type)) ||
 368             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_OFFSET,
 369                          htonl(priv->csum_offset)) ||
 370             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_FLAGS, htonl(priv->csum_flags)))
 371                 goto nla_put_failure;
 372         return 0;
 373
 374 nla_put_failure:
 375         return -1;
 376 }
 377
 378 static const struct nft_expr_ops nft_payload_set_ops = {
 379         .type           = &nft_payload_type,
 380         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload_set)),
 381         .eval           = nft_payload_set_eval,
 382         .init           = nft_payload_set_init,
 383         .dump           = nft_payload_set_dump,
 384 };
 385
 386 static const struct nft_expr_ops *
 387 nft_payload_select_ops(const struct nft_ctx *ctx,
 388                        const struct nlattr * const tb[])
 389 {
 390         enum nft_payload_bases base;
 391         unsigned int offset, len;
 392
 393         if (tb[NFTA_PAYLOAD_BASE] == NULL ||
 394             tb[NFTA_PAYLOAD_OFFSET] == NULL ||
 395             tb[NFTA_PAYLOAD_LEN] == NULL)
 396                 return ERR_PTR(-EINVAL);
 397
 398         base = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 399         switch (base) {
 400         case NFT_PAYLOAD_LL_HEADER:
 401         case NFT_PAYLOAD_NETWORK_HEADER:
 402         case NFT_PAYLOAD_TRANSPORT_HEADER:
 403                 break;
 404         default:
 405                 return ERR_PTR(-EOPNOTSUPP);
 406         }
 407
 408         if (tb[NFTA_PAYLOAD_SREG] != NULL) {
 409                 if (tb[NFTA_PAYLOAD_DREG] != NULL)
 410                         return ERR_PTR(-EINVAL);
 411                 return &nft_payload_set_ops;
 412         }
 413
 414         if (tb[NFTA_PAYLOAD_DREG] == NULL)
 415                 return ERR_PTR(-EINVAL);
 416
 417         offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 418         len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 419
 420         if (len <= 4 && is_power_of_2(len) && IS_ALIGNED(offset, len) &&
 421             base != NFT_PAYLOAD_LL_HEADER)
 422                 return &nft_payload_fast_ops;
 423         else
 424                 return &nft_payload_ops;
 425 }
 426
 427 struct nft_expr_type nft_payload_type __read_mostly = {
 428         .name           = "payload",
 429         .select_ops     = nft_payload_select_ops,
 430         .policy         = nft_payload_policy,
 431         .maxattr        = NFTA_PAYLOAD_MAX,
 432         .owner          = THIS_MODULE,
 433 };