linux/net/ipv4/ah4.c
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   1#define pr_fmt(fmt) "IPsec: " fmt
   2
   3#include <crypto/hash.h>
   4#include <linux/err.h>
   5#include <linux/module.h>
   6#include <linux/slab.h>
   7#include <net/ip.h>
   8#include <net/xfrm.h>
   9#include <net/ah.h>
  10#include <linux/crypto.h>
  11#include <linux/pfkeyv2.h>
  12#include <linux/scatterlist.h>
  13#include <net/icmp.h>
  14#include <net/protocol.h>
  15
  16struct ah_skb_cb {
  17        struct xfrm_skb_cb xfrm;
  18        void *tmp;
  19};
  20
  21#define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
  22
  23static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
  24                          unsigned int size)
  25{
  26        unsigned int len;
  27
  28        len = size + crypto_ahash_digestsize(ahash) +
  29              (crypto_ahash_alignmask(ahash) &
  30               ~(crypto_tfm_ctx_alignment() - 1));
  31
  32        len = ALIGN(len, crypto_tfm_ctx_alignment());
  33
  34        len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
  35        len = ALIGN(len, __alignof__(struct scatterlist));
  36
  37        len += sizeof(struct scatterlist) * nfrags;
  38
  39        return kmalloc(len, GFP_ATOMIC);
  40}
  41
  42static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
  43{
  44        return tmp + offset;
  45}
  46
  47static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
  48                             unsigned int offset)
  49{
  50        return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
  51}
  52
  53static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
  54                                               u8 *icv)
  55{
  56        struct ahash_request *req;
  57
  58        req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
  59                                crypto_tfm_ctx_alignment());
  60
  61        ahash_request_set_tfm(req, ahash);
  62
  63        return req;
  64}
  65
  66static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
  67                                             struct ahash_request *req)
  68{
  69        return (void *)ALIGN((unsigned long)(req + 1) +
  70                             crypto_ahash_reqsize(ahash),
  71                             __alignof__(struct scatterlist));
  72}
  73
  74/* Clear mutable options and find final destination to substitute
  75 * into IP header for icv calculation. Options are already checked
  76 * for validity, so paranoia is not required. */
  77
  78static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
  79{
  80        unsigned char *optptr = (unsigned char *)(iph+1);
  81        int  l = iph->ihl*4 - sizeof(struct iphdr);
  82        int  optlen;
  83
  84        while (l > 0) {
  85                switch (*optptr) {
  86                case IPOPT_END:
  87                        return 0;
  88                case IPOPT_NOOP:
  89                        l--;
  90                        optptr++;
  91                        continue;
  92                }
  93                optlen = optptr[1];
  94                if (optlen<2 || optlen>l)
  95                        return -EINVAL;
  96                switch (*optptr) {
  97                case IPOPT_SEC:
  98                case 0x85:      /* Some "Extended Security" crap. */
  99                case IPOPT_CIPSO:
 100                case IPOPT_RA:
 101                case 0x80|21:   /* RFC1770 */
 102                        break;
 103                case IPOPT_LSRR:
 104                case IPOPT_SSRR:
 105                        if (optlen < 6)
 106                                return -EINVAL;
 107                        memcpy(daddr, optptr+optlen-4, 4);
 108                        /* Fall through */
 109                default:
 110                        memset(optptr, 0, optlen);
 111                }
 112                l -= optlen;
 113                optptr += optlen;
 114        }
 115        return 0;
 116}
 117
 118static void ah_output_done(struct crypto_async_request *base, int err)
 119{
 120        u8 *icv;
 121        struct iphdr *iph;
 122        struct sk_buff *skb = base->data;
 123        struct xfrm_state *x = skb_dst(skb)->xfrm;
 124        struct ah_data *ahp = x->data;
 125        struct iphdr *top_iph = ip_hdr(skb);
 126        struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 127        int ihl = ip_hdrlen(skb);
 128
 129        iph = AH_SKB_CB(skb)->tmp;
 130        icv = ah_tmp_icv(ahp->ahash, iph, ihl);
 131        memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 132
 133        top_iph->tos = iph->tos;
 134        top_iph->ttl = iph->ttl;
 135        top_iph->frag_off = iph->frag_off;
 136        if (top_iph->ihl != 5) {
 137                top_iph->daddr = iph->daddr;
 138                memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 139        }
 140
 141        kfree(AH_SKB_CB(skb)->tmp);
 142        xfrm_output_resume(skb, err);
 143}
 144
 145static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 146{
 147        int err;
 148        int nfrags;
 149        int ihl;
 150        u8 *icv;
 151        struct sk_buff *trailer;
 152        struct crypto_ahash *ahash;
 153        struct ahash_request *req;
 154        struct scatterlist *sg;
 155        struct iphdr *iph, *top_iph;
 156        struct ip_auth_hdr *ah;
 157        struct ah_data *ahp;
 158
 159        ahp = x->data;
 160        ahash = ahp->ahash;
 161
 162        if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 163                goto out;
 164        nfrags = err;
 165
 166        skb_push(skb, -skb_network_offset(skb));
 167        ah = ip_auth_hdr(skb);
 168        ihl = ip_hdrlen(skb);
 169
 170        err = -ENOMEM;
 171        iph = ah_alloc_tmp(ahash, nfrags, ihl);
 172        if (!iph)
 173                goto out;
 174
 175        icv = ah_tmp_icv(ahash, iph, ihl);
 176        req = ah_tmp_req(ahash, icv);
 177        sg = ah_req_sg(ahash, req);
 178
 179        memset(ah->auth_data, 0, ahp->icv_trunc_len);
 180
 181        top_iph = ip_hdr(skb);
 182
 183        iph->tos = top_iph->tos;
 184        iph->ttl = top_iph->ttl;
 185        iph->frag_off = top_iph->frag_off;
 186
 187        if (top_iph->ihl != 5) {
 188                iph->daddr = top_iph->daddr;
 189                memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 190                err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 191                if (err)
 192                        goto out_free;
 193        }
 194
 195        ah->nexthdr = *skb_mac_header(skb);
 196        *skb_mac_header(skb) = IPPROTO_AH;
 197
 198        top_iph->tos = 0;
 199        top_iph->tot_len = htons(skb->len);
 200        top_iph->frag_off = 0;
 201        top_iph->ttl = 0;
 202        top_iph->check = 0;
 203
 204        if (x->props.flags & XFRM_STATE_ALIGN4)
 205                ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 206        else
 207                ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 208
 209        ah->reserved = 0;
 210        ah->spi = x->id.spi;
 211        ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 212
 213        sg_init_table(sg, nfrags);
 214        skb_to_sgvec(skb, sg, 0, skb->len);
 215
 216        ahash_request_set_crypt(req, sg, icv, skb->len);
 217        ahash_request_set_callback(req, 0, ah_output_done, skb);
 218
 219        AH_SKB_CB(skb)->tmp = iph;
 220
 221        err = crypto_ahash_digest(req);
 222        if (err) {
 223                if (err == -EINPROGRESS)
 224                        goto out;
 225
 226                if (err == -EBUSY)
 227                        err = NET_XMIT_DROP;
 228                goto out_free;
 229        }
 230
 231        memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 232
 233        top_iph->tos = iph->tos;
 234        top_iph->ttl = iph->ttl;
 235        top_iph->frag_off = iph->frag_off;
 236        if (top_iph->ihl != 5) {
 237                top_iph->daddr = iph->daddr;
 238                memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 239        }
 240
 241out_free:
 242        kfree(iph);
 243out:
 244        return err;
 245}
 246
 247static void ah_input_done(struct crypto_async_request *base, int err)
 248{
 249        u8 *auth_data;
 250        u8 *icv;
 251        struct iphdr *work_iph;
 252        struct sk_buff *skb = base->data;
 253        struct xfrm_state *x = xfrm_input_state(skb);
 254        struct ah_data *ahp = x->data;
 255        struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 256        int ihl = ip_hdrlen(skb);
 257        int ah_hlen = (ah->hdrlen + 2) << 2;
 258
 259        work_iph = AH_SKB_CB(skb)->tmp;
 260        auth_data = ah_tmp_auth(work_iph, ihl);
 261        icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 262
 263        err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 264        if (err)
 265                goto out;
 266
 267        err = ah->nexthdr;
 268
 269        skb->network_header += ah_hlen;
 270        memcpy(skb_network_header(skb), work_iph, ihl);
 271        __skb_pull(skb, ah_hlen + ihl);
 272        skb_set_transport_header(skb, -ihl);
 273out:
 274        kfree(AH_SKB_CB(skb)->tmp);
 275        xfrm_input_resume(skb, err);
 276}
 277
 278static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 279{
 280        int ah_hlen;
 281        int ihl;
 282        int nexthdr;
 283        int nfrags;
 284        u8 *auth_data;
 285        u8 *icv;
 286        struct sk_buff *trailer;
 287        struct crypto_ahash *ahash;
 288        struct ahash_request *req;
 289        struct scatterlist *sg;
 290        struct iphdr *iph, *work_iph;
 291        struct ip_auth_hdr *ah;
 292        struct ah_data *ahp;
 293        int err = -ENOMEM;
 294
 295        if (!pskb_may_pull(skb, sizeof(*ah)))
 296                goto out;
 297
 298        ah = (struct ip_auth_hdr *)skb->data;
 299        ahp = x->data;
 300        ahash = ahp->ahash;
 301
 302        nexthdr = ah->nexthdr;
 303        ah_hlen = (ah->hdrlen + 2) << 2;
 304
 305        if (x->props.flags & XFRM_STATE_ALIGN4) {
 306                if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 307                    ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 308                        goto out;
 309        } else {
 310                if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 311                    ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 312                        goto out;
 313        }
 314
 315        if (!pskb_may_pull(skb, ah_hlen))
 316                goto out;
 317
 318        /* We are going to _remove_ AH header to keep sockets happy,
 319         * so... Later this can change. */
 320        if (skb_cloned(skb) &&
 321            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 322                goto out;
 323
 324        skb->ip_summed = CHECKSUM_NONE;
 325
 326
 327        if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 328                goto out;
 329        nfrags = err;
 330
 331        ah = (struct ip_auth_hdr *)skb->data;
 332        iph = ip_hdr(skb);
 333        ihl = ip_hdrlen(skb);
 334
 335        work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
 336        if (!work_iph)
 337                goto out;
 338
 339        auth_data = ah_tmp_auth(work_iph, ihl);
 340        icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 341        req = ah_tmp_req(ahash, icv);
 342        sg = ah_req_sg(ahash, req);
 343
 344        memcpy(work_iph, iph, ihl);
 345        memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 346        memset(ah->auth_data, 0, ahp->icv_trunc_len);
 347
 348        iph->ttl = 0;
 349        iph->tos = 0;
 350        iph->frag_off = 0;
 351        iph->check = 0;
 352        if (ihl > sizeof(*iph)) {
 353                __be32 dummy;
 354                err = ip_clear_mutable_options(iph, &dummy);
 355                if (err)
 356                        goto out_free;
 357        }
 358
 359        skb_push(skb, ihl);
 360
 361        sg_init_table(sg, nfrags);
 362        skb_to_sgvec(skb, sg, 0, skb->len);
 363
 364        ahash_request_set_crypt(req, sg, icv, skb->len);
 365        ahash_request_set_callback(req, 0, ah_input_done, skb);
 366
 367        AH_SKB_CB(skb)->tmp = work_iph;
 368
 369        err = crypto_ahash_digest(req);
 370        if (err) {
 371                if (err == -EINPROGRESS)
 372                        goto out;
 373
 374                goto out_free;
 375        }
 376
 377        err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 378        if (err)
 379                goto out_free;
 380
 381        skb->network_header += ah_hlen;
 382        memcpy(skb_network_header(skb), work_iph, ihl);
 383        __skb_pull(skb, ah_hlen + ihl);
 384        skb_set_transport_header(skb, -ihl);
 385
 386        err = nexthdr;
 387
 388out_free:
 389        kfree (work_iph);
 390out:
 391        return err;
 392}
 393
 394static void ah4_err(struct sk_buff *skb, u32 info)
 395{
 396        struct net *net = dev_net(skb->dev);
 397        const struct iphdr *iph = (const struct iphdr *)skb->data;
 398        struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 399        struct xfrm_state *x;
 400
 401        switch (icmp_hdr(skb)->type) {
 402        case ICMP_DEST_UNREACH:
 403                if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 404                        return;
 405        case ICMP_REDIRECT:
 406                break;
 407        default:
 408                return;
 409        }
 410
 411        x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
 412                              ah->spi, IPPROTO_AH, AF_INET);
 413        if (!x)
 414                return;
 415
 416        if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
 417                ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_AH, 0);
 418        else
 419                ipv4_redirect(skb, net, 0, 0, IPPROTO_AH, 0);
 420        xfrm_state_put(x);
 421}
 422
 423static int ah_init_state(struct xfrm_state *x)
 424{
 425        struct ah_data *ahp = NULL;
 426        struct xfrm_algo_desc *aalg_desc;
 427        struct crypto_ahash *ahash;
 428
 429        if (!x->aalg)
 430                goto error;
 431
 432        if (x->encap)
 433                goto error;
 434
 435        ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 436        if (!ahp)
 437                return -ENOMEM;
 438
 439        ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 440        if (IS_ERR(ahash))
 441                goto error;
 442
 443        ahp->ahash = ahash;
 444        if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 445                                (x->aalg->alg_key_len + 7) / 8))
 446                goto error;
 447
 448        /*
 449         * Lookup the algorithm description maintained by xfrm_algo,
 450         * verify crypto transform properties, and store information
 451         * we need for AH processing.  This lookup cannot fail here
 452         * after a successful crypto_alloc_ahash().
 453         */
 454        aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 455        BUG_ON(!aalg_desc);
 456
 457        if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 458            crypto_ahash_digestsize(ahash)) {
 459                pr_info("%s: %s digestsize %u != %hu\n",
 460                        __func__, x->aalg->alg_name,
 461                        crypto_ahash_digestsize(ahash),
 462                        aalg_desc->uinfo.auth.icv_fullbits / 8);
 463                goto error;
 464        }
 465
 466        ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 467        ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 468
 469        BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 470
 471        if (x->props.flags & XFRM_STATE_ALIGN4)
 472                x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 473                                                  ahp->icv_trunc_len);
 474        else
 475                x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 476                                                  ahp->icv_trunc_len);
 477        if (x->props.mode == XFRM_MODE_TUNNEL)
 478                x->props.header_len += sizeof(struct iphdr);
 479        x->data = ahp;
 480
 481        return 0;
 482
 483error:
 484        if (ahp) {
 485                crypto_free_ahash(ahp->ahash);
 486                kfree(ahp);
 487        }
 488        return -EINVAL;
 489}
 490
 491static void ah_destroy(struct xfrm_state *x)
 492{
 493        struct ah_data *ahp = x->data;
 494
 495        if (!ahp)
 496                return;
 497
 498        crypto_free_ahash(ahp->ahash);
 499        kfree(ahp);
 500}
 501
 502
 503static const struct xfrm_type ah_type =
 504{
 505        .description    = "AH4",
 506        .owner          = THIS_MODULE,
 507        .proto          = IPPROTO_AH,
 508        .flags          = XFRM_TYPE_REPLAY_PROT,
 509        .init_state     = ah_init_state,
 510        .destructor     = ah_destroy,
 511        .input          = ah_input,
 512        .output         = ah_output
 513};
 514
 515static const struct net_protocol ah4_protocol = {
 516        .handler        =       xfrm4_rcv,
 517        .err_handler    =       ah4_err,
 518        .no_policy      =       1,
 519        .netns_ok       =       1,
 520};
 521
 522static int __init ah4_init(void)
 523{
 524        if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 525                pr_info("%s: can't add xfrm type\n", __func__);
 526                return -EAGAIN;
 527        }
 528        if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 529                pr_info("%s: can't add protocol\n", __func__);
 530                xfrm_unregister_type(&ah_type, AF_INET);
 531                return -EAGAIN;
 532        }
 533        return 0;
 534}
 535
 536static void __exit ah4_fini(void)
 537{
 538        if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 539                pr_info("%s: can't remove protocol\n", __func__);
 540        if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 541                pr_info("%s: can't remove xfrm type\n", __func__);
 542}
 543
 544module_init(ah4_init);
 545module_exit(ah4_fini);
 546MODULE_LICENSE("GPL");
 547MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
 548
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