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Linux/net/netfilter/nft_payload.c

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  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 };
125 
126 static int nft_payload_init(const struct nft_ctx *ctx,
127                             const struct nft_expr *expr,
128                             const struct nlattr * const tb[])
129 {
130         struct nft_payload *priv = nft_expr_priv(expr);
131 
132         priv->base   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
133         priv->offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
134         priv->len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
135         priv->dreg   = nft_parse_register(tb[NFTA_PAYLOAD_DREG]);
136 
137         return nft_validate_register_store(ctx, priv->dreg, NULL,
138                                            NFT_DATA_VALUE, priv->len);
139 }
140 
141 static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
142 {
143         const struct nft_payload *priv = nft_expr_priv(expr);
144 
145         if (nft_dump_register(skb, NFTA_PAYLOAD_DREG, priv->dreg) ||
146             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
147             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
148             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)))
149                 goto nla_put_failure;
150         return 0;
151 
152 nla_put_failure:
153         return -1;
154 }
155 
156 static const struct nft_expr_ops nft_payload_ops = {
157         .type           = &nft_payload_type,
158         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
159         .eval           = nft_payload_eval,
160         .init           = nft_payload_init,
161         .dump           = nft_payload_dump,
162 };
163 
164 const struct nft_expr_ops nft_payload_fast_ops = {
165         .type           = &nft_payload_type,
166         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
167         .eval           = nft_payload_eval,
168         .init           = nft_payload_init,
169         .dump           = nft_payload_dump,
170 };
171 
172 static inline void nft_csum_replace(__sum16 *sum, __wsum fsum, __wsum tsum)
173 {
174         *sum = csum_fold(csum_add(csum_sub(~csum_unfold(*sum), fsum), tsum));
175         if (*sum == 0)
176                 *sum = CSUM_MANGLED_0;
177 }
178 
179 static bool nft_payload_udp_checksum(struct sk_buff *skb, unsigned int thoff)
180 {
181         struct udphdr *uh, _uh;
182 
183         uh = skb_header_pointer(skb, thoff, sizeof(_uh), &_uh);
184         if (!uh)
185                 return false;
186 
187         return (__force bool)uh->check;
188 }
189 
190 static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
191                                      struct sk_buff *skb,
192                                      unsigned int *l4csum_offset)
193 {
194         switch (pkt->tprot) {
195         case IPPROTO_TCP:
196                 *l4csum_offset = offsetof(struct tcphdr, check);
197                 break;
198         case IPPROTO_UDP:
199                 if (!nft_payload_udp_checksum(skb, pkt->xt.thoff))
200                         return -1;
201                 /* Fall through. */
202         case IPPROTO_UDPLITE:
203                 *l4csum_offset = offsetof(struct udphdr, check);
204                 break;
205         case IPPROTO_ICMPV6:
206                 *l4csum_offset = offsetof(struct icmp6hdr, icmp6_cksum);
207                 break;
208         default:
209                 return -1;
210         }
211 
212         *l4csum_offset += pkt->xt.thoff;
213         return 0;
214 }
215 
216 static int nft_payload_l4csum_update(const struct nft_pktinfo *pkt,
217                                      struct sk_buff *skb,
218                                      __wsum fsum, __wsum tsum)
219 {
220         int l4csum_offset;
221         __sum16 sum;
222 
223         /* If we cannot determine layer 4 checksum offset or this packet doesn't
224          * require layer 4 checksum recalculation, skip this packet.
225          */
226         if (nft_payload_l4csum_offset(pkt, skb, &l4csum_offset) < 0)
227                 return 0;
228 
229         if (skb_copy_bits(skb, l4csum_offset, &sum, sizeof(sum)) < 0)
230                 return -1;
231 
232         /* Checksum mangling for an arbitrary amount of bytes, based on
233          * inet_proto_csum_replace*() functions.
234          */
235         if (skb->ip_summed != CHECKSUM_PARTIAL) {
236                 nft_csum_replace(&sum, fsum, tsum);
237                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
238                         skb->csum = ~csum_add(csum_sub(~(skb->csum), fsum),
239                                               tsum);
240                 }
241         } else {
242                 sum = ~csum_fold(csum_add(csum_sub(csum_unfold(sum), fsum),
243                                           tsum));
244         }
245 
246         if (!skb_make_writable(skb, l4csum_offset + sizeof(sum)) ||
247             skb_store_bits(skb, l4csum_offset, &sum, sizeof(sum)) < 0)
248                 return -1;
249 
250         return 0;
251 }
252 
253 static int nft_payload_csum_inet(struct sk_buff *skb, const u32 *src,
254                                  __wsum fsum, __wsum tsum, int csum_offset)
255 {
256         __sum16 sum;
257 
258         if (skb_copy_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
259                 return -1;
260 
261         nft_csum_replace(&sum, fsum, tsum);
262         if (!skb_make_writable(skb, csum_offset + sizeof(sum)) ||
263             skb_store_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
264                 return -1;
265 
266         return 0;
267 }
268 
269 static void nft_payload_set_eval(const struct nft_expr *expr,
270                                  struct nft_regs *regs,
271                                  const struct nft_pktinfo *pkt)
272 {
273         const struct nft_payload_set *priv = nft_expr_priv(expr);
274         struct sk_buff *skb = pkt->skb;
275         const u32 *src = &regs->data[priv->sreg];
276         int offset, csum_offset;
277         __wsum fsum, tsum;
278 
279         switch (priv->base) {
280         case NFT_PAYLOAD_LL_HEADER:
281                 if (!skb_mac_header_was_set(skb))
282                         goto err;
283                 offset = skb_mac_header(skb) - skb->data;
284                 break;
285         case NFT_PAYLOAD_NETWORK_HEADER:
286                 offset = skb_network_offset(skb);
287                 break;
288         case NFT_PAYLOAD_TRANSPORT_HEADER:
289                 if (!pkt->tprot_set)
290                         goto err;
291                 offset = pkt->xt.thoff;
292                 break;
293         default:
294                 BUG();
295         }
296 
297         csum_offset = offset + priv->csum_offset;
298         offset += priv->offset;
299 
300         if ((priv->csum_type == NFT_PAYLOAD_CSUM_INET || priv->csum_flags) &&
301             (priv->base != NFT_PAYLOAD_TRANSPORT_HEADER ||
302              skb->ip_summed != CHECKSUM_PARTIAL)) {
303                 fsum = skb_checksum(skb, offset, priv->len, 0);
304                 tsum = csum_partial(src, priv->len, 0);
305 
306                 if (priv->csum_type == NFT_PAYLOAD_CSUM_INET &&
307                     nft_payload_csum_inet(skb, src, fsum, tsum, csum_offset))
308                         goto err;
309 
310                 if (priv->csum_flags &&
311                     nft_payload_l4csum_update(pkt, skb, fsum, tsum) < 0)
312                         goto err;
313         }
314 
315         if (!skb_make_writable(skb, max(offset + priv->len, 0)) ||
316             skb_store_bits(skb, offset, src, priv->len) < 0)
317                 goto err;
318 
319         return;
320 err:
321         regs->verdict.code = NFT_BREAK;
322 }
323 
324 static int nft_payload_set_init(const struct nft_ctx *ctx,
325                                 const struct nft_expr *expr,
326                                 const struct nlattr * const tb[])
327 {
328         struct nft_payload_set *priv = nft_expr_priv(expr);
329 
330         priv->base        = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
331         priv->offset      = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
332         priv->len         = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
333         priv->sreg        = nft_parse_register(tb[NFTA_PAYLOAD_SREG]);
334 
335         if (tb[NFTA_PAYLOAD_CSUM_TYPE])
336                 priv->csum_type =
337                         ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_TYPE]));
338         if (tb[NFTA_PAYLOAD_CSUM_OFFSET])
339                 priv->csum_offset =
340                         ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_OFFSET]));
341         if (tb[NFTA_PAYLOAD_CSUM_FLAGS]) {
342                 u32 flags;
343 
344                 flags = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_FLAGS]));
345                 if (flags & ~NFT_PAYLOAD_L4CSUM_PSEUDOHDR)
346                         return -EINVAL;
347 
348                 priv->csum_flags = flags;
349         }
350 
351         switch (priv->csum_type) {
352         case NFT_PAYLOAD_CSUM_NONE:
353         case NFT_PAYLOAD_CSUM_INET:
354                 break;
355         default:
356                 return -EOPNOTSUPP;
357         }
358 
359         return nft_validate_register_load(priv->sreg, priv->len);
360 }
361 
362 static int nft_payload_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
363 {
364         const struct nft_payload_set *priv = nft_expr_priv(expr);
365 
366         if (nft_dump_register(skb, NFTA_PAYLOAD_SREG, priv->sreg) ||
367             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
368             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
369             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)) ||
370             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_TYPE, htonl(priv->csum_type)) ||
371             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_OFFSET,
372                          htonl(priv->csum_offset)) ||
373             nla_put_be32(skb, NFTA_PAYLOAD_CSUM_FLAGS, htonl(priv->csum_flags)))
374                 goto nla_put_failure;
375         return 0;
376 
377 nla_put_failure:
378         return -1;
379 }
380 
381 static const struct nft_expr_ops nft_payload_set_ops = {
382         .type           = &nft_payload_type,
383         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload_set)),
384         .eval           = nft_payload_set_eval,
385         .init           = nft_payload_set_init,
386         .dump           = nft_payload_set_dump,
387 };
388 
389 static const struct nft_expr_ops *
390 nft_payload_select_ops(const struct nft_ctx *ctx,
391                        const struct nlattr * const tb[])
392 {
393         enum nft_payload_bases base;
394         unsigned int offset, len;
395 
396         if (tb[NFTA_PAYLOAD_BASE] == NULL ||
397             tb[NFTA_PAYLOAD_OFFSET] == NULL ||
398             tb[NFTA_PAYLOAD_LEN] == NULL)
399                 return ERR_PTR(-EINVAL);
400 
401         base = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
402         switch (base) {
403         case NFT_PAYLOAD_LL_HEADER:
404         case NFT_PAYLOAD_NETWORK_HEADER:
405         case NFT_PAYLOAD_TRANSPORT_HEADER:
406                 break;
407         default:
408                 return ERR_PTR(-EOPNOTSUPP);
409         }
410 
411         if (tb[NFTA_PAYLOAD_SREG] != NULL) {
412                 if (tb[NFTA_PAYLOAD_DREG] != NULL)
413                         return ERR_PTR(-EINVAL);
414                 return &nft_payload_set_ops;
415         }
416 
417         if (tb[NFTA_PAYLOAD_DREG] == NULL)
418                 return ERR_PTR(-EINVAL);
419 
420         offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
421         len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
422 
423         if (len <= 4 && is_power_of_2(len) && IS_ALIGNED(offset, len) &&
424             base != NFT_PAYLOAD_LL_HEADER)
425                 return &nft_payload_fast_ops;
426         else
427                 return &nft_payload_ops;
428 }
429 
430 struct nft_expr_type nft_payload_type __read_mostly = {
431         .name           = "payload",
432         .select_ops     = nft_payload_select_ops,
433         .policy         = nft_payload_policy,
434         .maxattr        = NFTA_PAYLOAD_MAX,
435         .owner          = THIS_MODULE,
436 };
437 

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