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TOMOYO Linux Cross Reference
Linux/net/ipv4/ah4.c

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  1 #include <crypto/hash.h>
  2 #include <linux/err.h>
  3 #include <linux/module.h>
  4 #include <linux/slab.h>
  5 #include <net/ip.h>
  6 #include <net/xfrm.h>
  7 #include <net/ah.h>
  8 #include <linux/crypto.h>
  9 #include <linux/pfkeyv2.h>
 10 #include <linux/scatterlist.h>
 11 #include <net/icmp.h>
 12 #include <net/protocol.h>
 13 
 14 struct ah_skb_cb {
 15         struct xfrm_skb_cb xfrm;
 16         void *tmp;
 17 };
 18 
 19 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
 20 
 21 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
 22                           unsigned int size)
 23 {
 24         unsigned int len;
 25 
 26         len = size + crypto_ahash_digestsize(ahash) +
 27               (crypto_ahash_alignmask(ahash) &
 28                ~(crypto_tfm_ctx_alignment() - 1));
 29 
 30         len = ALIGN(len, crypto_tfm_ctx_alignment());
 31 
 32         len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
 33         len = ALIGN(len, __alignof__(struct scatterlist));
 34 
 35         len += sizeof(struct scatterlist) * nfrags;
 36 
 37         return kmalloc(len, GFP_ATOMIC);
 38 }
 39 
 40 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
 41 {
 42         return tmp + offset;
 43 }
 44 
 45 static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
 46                              unsigned int offset)
 47 {
 48         return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
 49 }
 50 
 51 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
 52                                                u8 *icv)
 53 {
 54         struct ahash_request *req;
 55 
 56         req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
 57                                 crypto_tfm_ctx_alignment());
 58 
 59         ahash_request_set_tfm(req, ahash);
 60 
 61         return req;
 62 }
 63 
 64 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
 65                                              struct ahash_request *req)
 66 {
 67         return (void *)ALIGN((unsigned long)(req + 1) +
 68                              crypto_ahash_reqsize(ahash),
 69                              __alignof__(struct scatterlist));
 70 }
 71 
 72 /* Clear mutable options and find final destination to substitute
 73  * into IP header for icv calculation. Options are already checked
 74  * for validity, so paranoia is not required. */
 75 
 76 static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
 77 {
 78         unsigned char * optptr = (unsigned char*)(iph+1);
 79         int  l = iph->ihl*4 - sizeof(struct iphdr);
 80         int  optlen;
 81 
 82         while (l > 0) {
 83                 switch (*optptr) {
 84                 case IPOPT_END:
 85                         return 0;
 86                 case IPOPT_NOOP:
 87                         l--;
 88                         optptr++;
 89                         continue;
 90                 }
 91                 optlen = optptr[1];
 92                 if (optlen<2 || optlen>l)
 93                         return -EINVAL;
 94                 switch (*optptr) {
 95                 case IPOPT_SEC:
 96                 case 0x85:      /* Some "Extended Security" crap. */
 97                 case IPOPT_CIPSO:
 98                 case IPOPT_RA:
 99                 case 0x80|21:   /* RFC1770 */
100                         break;
101                 case IPOPT_LSRR:
102                 case IPOPT_SSRR:
103                         if (optlen < 6)
104                                 return -EINVAL;
105                         memcpy(daddr, optptr+optlen-4, 4);
106                         /* Fall through */
107                 default:
108                         memset(optptr, 0, optlen);
109                 }
110                 l -= optlen;
111                 optptr += optlen;
112         }
113         return 0;
114 }
115 
116 static void ah_output_done(struct crypto_async_request *base, int err)
117 {
118         u8 *icv;
119         struct iphdr *iph;
120         struct sk_buff *skb = base->data;
121         struct xfrm_state *x = skb_dst(skb)->xfrm;
122         struct ah_data *ahp = x->data;
123         struct iphdr *top_iph = ip_hdr(skb);
124         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
125         int ihl = ip_hdrlen(skb);
126 
127         iph = AH_SKB_CB(skb)->tmp;
128         icv = ah_tmp_icv(ahp->ahash, iph, ihl);
129         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
130 
131         top_iph->tos = iph->tos;
132         top_iph->ttl = iph->ttl;
133         top_iph->frag_off = iph->frag_off;
134         if (top_iph->ihl != 5) {
135                 top_iph->daddr = iph->daddr;
136                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
137         }
138 
139         kfree(AH_SKB_CB(skb)->tmp);
140         xfrm_output_resume(skb, err);
141 }
142 
143 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
144 {
145         int err;
146         int nfrags;
147         int ihl;
148         u8 *icv;
149         struct sk_buff *trailer;
150         struct crypto_ahash *ahash;
151         struct ahash_request *req;
152         struct scatterlist *sg;
153         struct iphdr *iph, *top_iph;
154         struct ip_auth_hdr *ah;
155         struct ah_data *ahp;
156 
157         ahp = x->data;
158         ahash = ahp->ahash;
159 
160         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
161                 goto out;
162         nfrags = err;
163 
164         skb_push(skb, -skb_network_offset(skb));
165         ah = ip_auth_hdr(skb);
166         ihl = ip_hdrlen(skb);
167 
168         err = -ENOMEM;
169         iph = ah_alloc_tmp(ahash, nfrags, ihl);
170         if (!iph)
171                 goto out;
172 
173         icv = ah_tmp_icv(ahash, iph, ihl);
174         req = ah_tmp_req(ahash, icv);
175         sg = ah_req_sg(ahash, req);
176 
177         memset(ah->auth_data, 0, ahp->icv_trunc_len);
178 
179         top_iph = ip_hdr(skb);
180 
181         iph->tos = top_iph->tos;
182         iph->ttl = top_iph->ttl;
183         iph->frag_off = top_iph->frag_off;
184 
185         if (top_iph->ihl != 5) {
186                 iph->daddr = top_iph->daddr;
187                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
188                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
189                 if (err)
190                         goto out_free;
191         }
192 
193         ah->nexthdr = *skb_mac_header(skb);
194         *skb_mac_header(skb) = IPPROTO_AH;
195 
196         top_iph->tos = 0;
197         top_iph->tot_len = htons(skb->len);
198         top_iph->frag_off = 0;
199         top_iph->ttl = 0;
200         top_iph->check = 0;
201 
202         if (x->props.flags & XFRM_STATE_ALIGN4)
203                 ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
204         else
205                 ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
206 
207         ah->reserved = 0;
208         ah->spi = x->id.spi;
209         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
210 
211         sg_init_table(sg, nfrags);
212         skb_to_sgvec(skb, sg, 0, skb->len);
213 
214         ahash_request_set_crypt(req, sg, icv, skb->len);
215         ahash_request_set_callback(req, 0, ah_output_done, skb);
216 
217         AH_SKB_CB(skb)->tmp = iph;
218 
219         err = crypto_ahash_digest(req);
220         if (err) {
221                 if (err == -EINPROGRESS)
222                         goto out;
223 
224                 if (err == -EBUSY)
225                         err = NET_XMIT_DROP;
226                 goto out_free;
227         }
228 
229         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
230 
231         top_iph->tos = iph->tos;
232         top_iph->ttl = iph->ttl;
233         top_iph->frag_off = iph->frag_off;
234         if (top_iph->ihl != 5) {
235                 top_iph->daddr = iph->daddr;
236                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
237         }
238 
239 out_free:
240         kfree(iph);
241 out:
242         return err;
243 }
244 
245 static void ah_input_done(struct crypto_async_request *base, int err)
246 {
247         u8 *auth_data;
248         u8 *icv;
249         struct iphdr *work_iph;
250         struct sk_buff *skb = base->data;
251         struct xfrm_state *x = xfrm_input_state(skb);
252         struct ah_data *ahp = x->data;
253         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
254         int ihl = ip_hdrlen(skb);
255         int ah_hlen = (ah->hdrlen + 2) << 2;
256 
257         work_iph = AH_SKB_CB(skb)->tmp;
258         auth_data = ah_tmp_auth(work_iph, ihl);
259         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
260 
261         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
262         if (err)
263                 goto out;
264 
265         err = ah->nexthdr;
266 
267         skb->network_header += ah_hlen;
268         memcpy(skb_network_header(skb), work_iph, ihl);
269         __skb_pull(skb, ah_hlen + ihl);
270         skb_set_transport_header(skb, -ihl);
271 out:
272         kfree(AH_SKB_CB(skb)->tmp);
273         xfrm_input_resume(skb, err);
274 }
275 
276 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
277 {
278         int ah_hlen;
279         int ihl;
280         int nexthdr;
281         int nfrags;
282         u8 *auth_data;
283         u8 *icv;
284         struct sk_buff *trailer;
285         struct crypto_ahash *ahash;
286         struct ahash_request *req;
287         struct scatterlist *sg;
288         struct iphdr *iph, *work_iph;
289         struct ip_auth_hdr *ah;
290         struct ah_data *ahp;
291         int err = -ENOMEM;
292 
293         if (!pskb_may_pull(skb, sizeof(*ah)))
294                 goto out;
295 
296         ah = (struct ip_auth_hdr *)skb->data;
297         ahp = x->data;
298         ahash = ahp->ahash;
299 
300         nexthdr = ah->nexthdr;
301         ah_hlen = (ah->hdrlen + 2) << 2;
302 
303         if (x->props.flags & XFRM_STATE_ALIGN4) {
304                 if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
305                     ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
306                         goto out;
307         } else {
308                 if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
309                     ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
310                         goto out;
311         }
312 
313         if (!pskb_may_pull(skb, ah_hlen))
314                 goto out;
315 
316         /* We are going to _remove_ AH header to keep sockets happy,
317          * so... Later this can change. */
318         if (skb_cloned(skb) &&
319             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
320                 goto out;
321 
322         skb->ip_summed = CHECKSUM_NONE;
323 
324 
325         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
326                 goto out;
327         nfrags = err;
328 
329         ah = (struct ip_auth_hdr *)skb->data;
330         iph = ip_hdr(skb);
331         ihl = ip_hdrlen(skb);
332 
333         work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
334         if (!work_iph)
335                 goto out;
336 
337         auth_data = ah_tmp_auth(work_iph, ihl);
338         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
339         req = ah_tmp_req(ahash, icv);
340         sg = ah_req_sg(ahash, req);
341 
342         memcpy(work_iph, iph, ihl);
343         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
344         memset(ah->auth_data, 0, ahp->icv_trunc_len);
345 
346         iph->ttl = 0;
347         iph->tos = 0;
348         iph->frag_off = 0;
349         iph->check = 0;
350         if (ihl > sizeof(*iph)) {
351                 __be32 dummy;
352                 err = ip_clear_mutable_options(iph, &dummy);
353                 if (err)
354                         goto out_free;
355         }
356 
357         skb_push(skb, ihl);
358 
359         sg_init_table(sg, nfrags);
360         skb_to_sgvec(skb, sg, 0, skb->len);
361 
362         ahash_request_set_crypt(req, sg, icv, skb->len);
363         ahash_request_set_callback(req, 0, ah_input_done, skb);
364 
365         AH_SKB_CB(skb)->tmp = work_iph;
366 
367         err = crypto_ahash_digest(req);
368         if (err) {
369                 if (err == -EINPROGRESS)
370                         goto out;
371 
372                 goto out_free;
373         }
374 
375         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
376         if (err)
377                 goto out_free;
378 
379         skb->network_header += ah_hlen;
380         memcpy(skb_network_header(skb), work_iph, ihl);
381         __skb_pull(skb, ah_hlen + ihl);
382         skb_set_transport_header(skb, -ihl);
383 
384         err = nexthdr;
385 
386 out_free:
387         kfree (work_iph);
388 out:
389         return err;
390 }
391 
392 static void ah4_err(struct sk_buff *skb, u32 info)
393 {
394         struct net *net = dev_net(skb->dev);
395         const struct iphdr *iph = (const struct iphdr *)skb->data;
396         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
397         struct xfrm_state *x;
398 
399         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
400             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
401                 return;
402 
403         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
404                               ah->spi, IPPROTO_AH, AF_INET);
405         if (!x)
406                 return;
407         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
408                ntohl(ah->spi), ntohl(iph->daddr));
409         xfrm_state_put(x);
410 }
411 
412 static int ah_init_state(struct xfrm_state *x)
413 {
414         struct ah_data *ahp = NULL;
415         struct xfrm_algo_desc *aalg_desc;
416         struct crypto_ahash *ahash;
417 
418         if (!x->aalg)
419                 goto error;
420 
421         if (x->encap)
422                 goto error;
423 
424         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
425         if (!ahp)
426                 return -ENOMEM;
427 
428         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
429         if (IS_ERR(ahash))
430                 goto error;
431 
432         ahp->ahash = ahash;
433         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
434                                 (x->aalg->alg_key_len + 7) / 8))
435                 goto error;
436 
437         /*
438          * Lookup the algorithm description maintained by xfrm_algo,
439          * verify crypto transform properties, and store information
440          * we need for AH processing.  This lookup cannot fail here
441          * after a successful crypto_alloc_ahash().
442          */
443         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
444         BUG_ON(!aalg_desc);
445 
446         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
447             crypto_ahash_digestsize(ahash)) {
448                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
449                        x->aalg->alg_name, crypto_ahash_digestsize(ahash),
450                        aalg_desc->uinfo.auth.icv_fullbits/8);
451                 goto error;
452         }
453 
454         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
455         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
456 
457         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
458 
459         if (x->props.flags & XFRM_STATE_ALIGN4)
460                 x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
461                                                   ahp->icv_trunc_len);
462         else
463                 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
464                                                   ahp->icv_trunc_len);
465         if (x->props.mode == XFRM_MODE_TUNNEL)
466                 x->props.header_len += sizeof(struct iphdr);
467         x->data = ahp;
468 
469         return 0;
470 
471 error:
472         if (ahp) {
473                 crypto_free_ahash(ahp->ahash);
474                 kfree(ahp);
475         }
476         return -EINVAL;
477 }
478 
479 static void ah_destroy(struct xfrm_state *x)
480 {
481         struct ah_data *ahp = x->data;
482 
483         if (!ahp)
484                 return;
485 
486         crypto_free_ahash(ahp->ahash);
487         kfree(ahp);
488 }
489 
490 
491 static const struct xfrm_type ah_type =
492 {
493         .description    = "AH4",
494         .owner          = THIS_MODULE,
495         .proto          = IPPROTO_AH,
496         .flags          = XFRM_TYPE_REPLAY_PROT,
497         .init_state     = ah_init_state,
498         .destructor     = ah_destroy,
499         .input          = ah_input,
500         .output         = ah_output
501 };
502 
503 static const struct net_protocol ah4_protocol = {
504         .handler        =       xfrm4_rcv,
505         .err_handler    =       ah4_err,
506         .no_policy      =       1,
507         .netns_ok       =       1,
508 };
509 
510 static int __init ah4_init(void)
511 {
512         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
513                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
514                 return -EAGAIN;
515         }
516         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
517                 printk(KERN_INFO "ip ah init: can't add protocol\n");
518                 xfrm_unregister_type(&ah_type, AF_INET);
519                 return -EAGAIN;
520         }
521         return 0;
522 }
523 
524 static void __exit ah4_fini(void)
525 {
526         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
527                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
528         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
529                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
530 }
531 
532 module_init(ah4_init);
533 module_exit(ah4_fini);
534 MODULE_LICENSE("GPL");
535 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
536 

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